// SPDX-License-Identifier: GPL-2.0
/*
 * File operations used by nfsd. Some of these have been ripped from
 * other parts of the kernel because they weren't exported, others
 * are partial duplicates with added or changed functionality.
 *
 * Note that several functions dget() the dentry upon which they want
 * to act, most notably those that create directory entries. Response
 * dentry's are dput()'d if necessary in the release callback.
 * So if you notice code paths that apparently fail to dput() the
 * dentry, don't worry--they have been taken care of.
 *
 * Copyright (C) 1995-1999 Olaf Kirch <okir@monad.swb.de>
 * Zerocpy NFS support (C) 2002 Hirokazu Takahashi <taka@valinux.co.jp>
 */

#include <linux/fs.h>
#include <linux/file.h>
#include <linux/splice.h>
#include <linux/falloc.h>
#include <linux/fcntl.h>
#include <linux/namei.h>
#include <linux/delay.h>
#include <linux/fsnotify.h>
#include <linux/posix_acl_xattr.h>
#include <linux/xattr.h>
#include <linux/jhash.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/exportfs.h>
#include <linux/writeback.h>
#include <linux/security.h>
#include <linux/sunrpc/xdr.h>

#include "xdr3.h"

#ifdef CONFIG_NFSD_V4
#include "acl.h"
#include "idmap.h"
#include "xdr4.h"
#endif /* CONFIG_NFSD_V4 */

#include "nfsd.h"
#include "vfs.h"
#include "filecache.h"
#include "trace.h"

#define NFSDDBG_FACILITY                NFSDDBG_FILEOP

bool nfsd_disable_splice_read __read_mostly;
u64 nfsd_io_cache_read __read_mostly = NFSD_IO_BUFFERED;
u64 nfsd_io_cache_write __read_mostly = NFSD_IO_BUFFERED;

/**
 * nfserrno - Map Linux errnos to NFS errnos
 * @errno: POSIX(-ish) error code to be mapped
 *
 * Returns the appropriate (net-endian) nfserr_* (or nfs_ok if errno is 0). If
 * it's an error we don't expect, log it once and return nfserr_io.
 */
__be32
nfserrno (int errno)
{
        static struct {
                __be32  nfserr;
                int     syserr;
        } nfs_errtbl[] = {
                { nfs_ok, 0 },
                { nfserr_perm, -EPERM },
                { nfserr_noent, -ENOENT },
                { nfserr_io, -EIO },
                { nfserr_nxio, -ENXIO },
                { nfserr_fbig, -E2BIG },
                { nfserr_stale, -EBADF },
                { nfserr_acces, -EACCES },
                { nfserr_exist, -EEXIST },
                { nfserr_xdev, -EXDEV },
                { nfserr_nodev, -ENODEV },
                { nfserr_notdir, -ENOTDIR },
                { nfserr_isdir, -EISDIR },
                { nfserr_inval, -EINVAL },
                { nfserr_fbig, -EFBIG },
                { nfserr_nospc, -ENOSPC },
                { nfserr_rofs, -EROFS },
                { nfserr_mlink, -EMLINK },
                { nfserr_nametoolong, -ENAMETOOLONG },
                { nfserr_notempty, -ENOTEMPTY },
                { nfserr_dquot, -EDQUOT },
                { nfserr_stale, -ESTALE },
                { nfserr_jukebox, -ETIMEDOUT },
                { nfserr_jukebox, -ERESTARTSYS },
                { nfserr_jukebox, -EAGAIN },
                { nfserr_jukebox, -EWOULDBLOCK },
                { nfserr_jukebox, -ENOMEM },
                { nfserr_io, -ETXTBSY },
                { nfserr_notsupp, -EOPNOTSUPP },
                { nfserr_toosmall, -ETOOSMALL },
                { nfserr_serverfault, -ESERVERFAULT },
                { nfserr_serverfault, -ENFILE },
                { nfserr_io, -EREMOTEIO },
                { nfserr_stale, -EOPENSTALE },
                { nfserr_io, -EUCLEAN },
                { nfserr_perm, -ENOKEY },
                { nfserr_no_grace, -ENOGRACE},
                { nfserr_io, -EBADMSG },
        };
        int     i;

        for (i = 0; i < ARRAY_SIZE(nfs_errtbl); i++) {
                if (nfs_errtbl[i].syserr == errno)
                        return nfs_errtbl[i].nfserr;
        }
        WARN_ONCE(1, "nfsd: non-standard errno: %d\n", errno);
        return nfserr_io;
}

/* 
 * Called from nfsd_lookup and encode_dirent. Check if we have crossed 
 * a mount point.
 * Returns -EAGAIN or -ETIMEDOUT leaving *dpp and *expp unchanged,
 *  or nfs_ok having possibly changed *dpp and *expp
 */
int
nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp, 
                        struct svc_export **expp)
{
        struct svc_export *exp = *expp, *exp2 = NULL;
        struct dentry *dentry = *dpp;
        struct path path = {.mnt = mntget(exp->ex_path.mnt),
                            .dentry = dget(dentry)};
        unsigned int follow_flags = 0;
        int err = 0;

        if (exp->ex_flags & NFSEXP_CROSSMOUNT)
                follow_flags = LOOKUP_AUTOMOUNT;

        err = follow_down(&path, follow_flags);
        if (err < 0)
                goto out;
        if (path.mnt == exp->ex_path.mnt && path.dentry == dentry &&
            nfsd_mountpoint(dentry, exp) == 2) {
                /* This is only a mountpoint in some other namespace */
                path_put(&path);
                goto out;
        }

        exp2 = rqst_exp_get_by_name(rqstp, &path);
        if (IS_ERR(exp2)) {
                err = PTR_ERR(exp2);
                /*
                 * We normally allow NFS clients to continue
                 * "underneath" a mountpoint that is not exported.
                 * The exception is V4ROOT, where no traversal is ever
                 * allowed without an explicit export of the new
                 * directory.
                 */
                if (err == -ENOENT && !(exp->ex_flags & NFSEXP_V4ROOT))
                        err = 0;
                path_put(&path);
                goto out;
        }
        if (nfsd_v4client(rqstp) ||
                (exp->ex_flags & NFSEXP_CROSSMOUNT) || EX_NOHIDE(exp2)) {
                /* successfully crossed mount point */
                /*
                 * This is subtle: path.dentry is *not* on path.mnt
                 * at this point.  The only reason we are safe is that
                 * original mnt is pinned down by exp, so we should
                 * put path *before* putting exp
                 */
                *dpp = path.dentry;
                path.dentry = dentry;
                *expp = exp2;
                exp2 = exp;
        }
        path_put(&path);
        exp_put(exp2);
out:
        return err;
}

static void follow_to_parent(struct path *path)
{
        struct dentry *dp;

        while (path->dentry == path->mnt->mnt_root && follow_up(path))
                ;
        dp = dget_parent(path->dentry);
        dput(path->dentry);
        path->dentry = dp;
}

static int nfsd_lookup_parent(struct svc_rqst *rqstp, struct dentry *dparent, struct svc_export **exp, struct dentry **dentryp)
{
        struct svc_export *exp2;
        struct path path = {.mnt = mntget((*exp)->ex_path.mnt),
                            .dentry = dget(dparent)};

        follow_to_parent(&path);

        exp2 = rqst_exp_parent(rqstp, &path);
        if (PTR_ERR(exp2) == -ENOENT) {
                *dentryp = dget(dparent);
        } else if (IS_ERR(exp2)) {
                path_put(&path);
                return PTR_ERR(exp2);
        } else {
                *dentryp = dget(path.dentry);
                exp_put(*exp);
                *exp = exp2;
        }
        path_put(&path);
        return 0;
}

/*
 * For nfsd purposes, we treat V4ROOT exports as though there was an
 * export at *every* directory.
 * We return:
 * '1' if this dentry *must* be an export point,
 * '2' if it might be, if there is really a mount here, and
 * '0' if there is no chance of an export point here.
 */
int nfsd_mountpoint(struct dentry *dentry, struct svc_export *exp)
{
        if (!d_inode(dentry))
                return 0;
        if (exp->ex_flags & NFSEXP_V4ROOT)
                return 1;
        if (nfsd4_is_junction(dentry))
                return 1;
        if (d_managed(dentry))
                /*
                 * Might only be a mountpoint in a different namespace,
                 * but we need to check.
                 */
                return 2;
        return 0;
}

__be32
nfsd_lookup_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp,
                   const char *name, unsigned int len,
                   struct svc_export **exp_ret, struct dentry **dentry_ret)
{
        struct svc_export       *exp;
        struct dentry           *dparent;
        struct dentry           *dentry;
        int                     host_err;

        trace_nfsd_vfs_lookup(rqstp, fhp, name, len);

        dparent = fhp->fh_dentry;
        exp = exp_get(fhp->fh_export);

        /* Lookup the name, but don't follow links */
        if (isdotent(name, len)) {
                if (len==1)
                        dentry = dget(dparent);
                else if (dparent != exp->ex_path.dentry)
                        dentry = dget_parent(dparent);
                else if (!EX_NOHIDE(exp) && !nfsd_v4client(rqstp))
                        dentry = dget(dparent); /* .. == . just like at / */
                else {
                        /* checking mountpoint crossing is very different when stepping up */
                        host_err = nfsd_lookup_parent(rqstp, dparent, &exp, &dentry);
                        if (host_err)
                                goto out_nfserr;
                }
        } else {
                dentry = lookup_one_unlocked(&nop_mnt_idmap,
                                             &QSTR_LEN(name, len), dparent);
                host_err = PTR_ERR(dentry);
                if (IS_ERR(dentry))
                        goto out_nfserr;
                if (nfsd_mountpoint(dentry, exp)) {
                        host_err = nfsd_cross_mnt(rqstp, &dentry, &exp);
                        if (host_err) {
                                dput(dentry);
                                goto out_nfserr;
                        }
                }
        }
        *dentry_ret = dentry;
        *exp_ret = exp;
        return 0;

out_nfserr:
        exp_put(exp);
        return nfserrno(host_err);
}

/**
 * nfsd_lookup - look up a single path component for nfsd
 *
 * @rqstp:   the request context
 * @fhp:     the file handle of the directory
 * @name:    the component name, or %NULL to look up parent
 * @len:     length of name to examine
 * @resfh:   pointer to pre-initialised filehandle to hold result.
 *
 * Look up one component of a pathname.
 * N.B. After this call _both_ fhp and resfh need an fh_put
 *
 * If the lookup would cross a mountpoint, and the mounted filesystem
 * is exported to the client with NFSEXP_NOHIDE, then the lookup is
 * accepted as it stands and the mounted directory is
 * returned. Otherwise the covered directory is returned.
 * NOTE: this mountpoint crossing is not supported properly by all
 *   clients and is explicitly disallowed for NFSv3
 *
 */
__be32
nfsd_lookup(struct svc_rqst *rqstp, struct svc_fh *fhp, const char *name,
            unsigned int len, struct svc_fh *resfh)
{
        struct svc_export       *exp;
        struct dentry           *dentry;
        __be32 err;

        err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_EXEC);
        if (err)
                return err;
        err = nfsd_lookup_dentry(rqstp, fhp, name, len, &exp, &dentry);
        if (err)
                return err;
        err = check_nfsd_access(exp, rqstp, false);
        if (err)
                goto out;
        /*
         * Note: we compose the file handle now, but as the
         * dentry may be negative, it may need to be updated.
         */
        err = fh_compose(resfh, exp, dentry, fhp);
        if (!err && d_really_is_negative(dentry))
                err = nfserr_noent;
out:
        dput(dentry);
        exp_put(exp);
        return err;
}

static void
commit_reset_write_verifier(struct nfsd_net *nn, struct svc_rqst *rqstp,
                            int err)
{
        switch (err) {
        case -EAGAIN:
        case -ESTALE:
                /*
                 * Neither of these are the result of a problem with
                 * durable storage, so avoid a write verifier reset.
                 */
                break;
        default:
                nfsd_reset_write_verifier(nn);
                trace_nfsd_writeverf_reset(nn, rqstp, err);
        }
}

/*
 * Commit metadata changes to stable storage.
 */
static int
commit_inode_metadata(struct inode *inode)
{
        const struct export_operations *export_ops = inode->i_sb->s_export_op;

        if (export_ops->commit_metadata)
                return export_ops->commit_metadata(inode);
        return sync_inode_metadata(inode, 1);
}

static int
commit_metadata(struct svc_fh *fhp)
{
        struct inode *inode = d_inode(fhp->fh_dentry);

        if (!EX_ISSYNC(fhp->fh_export))
                return 0;
        return commit_inode_metadata(inode);
}

/*
 * Go over the attributes and take care of the small differences between
 * NFS semantics and what Linux expects.
 */
static void
nfsd_sanitize_attrs(struct inode *inode, struct iattr *iap)
{
        /* Ignore mode updates on symlinks */
        if (S_ISLNK(inode->i_mode))
                iap->ia_valid &= ~ATTR_MODE;

        /* sanitize the mode change */
        if (iap->ia_valid & ATTR_MODE) {
                iap->ia_mode &= S_IALLUGO;
                iap->ia_mode |= (inode->i_mode & ~S_IALLUGO);
        }

        /* Revoke setuid/setgid on chown */
        if (!S_ISDIR(inode->i_mode) &&
            ((iap->ia_valid & ATTR_UID) || (iap->ia_valid & ATTR_GID))) {
                iap->ia_valid |= ATTR_KILL_PRIV;
                if (iap->ia_valid & ATTR_MODE) {
                        /* we're setting mode too, just clear the s*id bits */
                        iap->ia_mode &= ~S_ISUID;
                        if (iap->ia_mode & S_IXGRP)
                                iap->ia_mode &= ~S_ISGID;
                } else {
                        /* set ATTR_KILL_* bits and let VFS handle it */
                        iap->ia_valid |= ATTR_KILL_SUID;
                        iap->ia_valid |=
                                setattr_should_drop_sgid(&nop_mnt_idmap, inode);
                }
        }
}

static __be32
nfsd_get_write_access(struct svc_rqst *rqstp, struct svc_fh *fhp,
                struct iattr *iap)
{
        struct inode *inode = d_inode(fhp->fh_dentry);

        if (iap->ia_size < inode->i_size) {
                __be32 err;

                err = nfsd_permission(&rqstp->rq_cred,
                                      fhp->fh_export, fhp->fh_dentry,
                                      NFSD_MAY_TRUNC | NFSD_MAY_OWNER_OVERRIDE);
                if (err)
                        return err;
        }
        return nfserrno(get_write_access(inode));
}

static int __nfsd_setattr(struct dentry *dentry, struct iattr *iap)
{
        int host_err;

        if (iap->ia_valid & ATTR_SIZE) {
                /*
                 * RFC5661, Section 18.30.4:
                 *   Changing the size of a file with SETATTR indirectly
                 *   changes the time_modify and change attributes.
                 *
                 * (and similar for the older RFCs)
                 */
                struct iattr size_attr = {
                        .ia_valid       = ATTR_SIZE | ATTR_CTIME | ATTR_MTIME,
                        .ia_size        = iap->ia_size,
                };

                if (iap->ia_size < 0)
                        return -EFBIG;

                host_err = notify_change(&nop_mnt_idmap, dentry, &size_attr, NULL);
                if (host_err)
                        return host_err;
                iap->ia_valid &= ~ATTR_SIZE;

                /*
                 * Avoid the additional setattr call below if the only other
                 * attribute that the client sends is the mtime, as we update
                 * it as part of the size change above.
                 */
                if ((iap->ia_valid & ~ATTR_MTIME) == 0)
                        return 0;
        }

        if ((iap->ia_valid & ~ATTR_DELEG) == 0)
                return 0;

        /*
         * If ATTR_DELEG is set, then this is an update from a client that
         * holds a delegation. If this is an update for only the atime, the
         * ctime should not be changed. If the update contains the mtime
         * too, then ATTR_CTIME should already be set.
         */
        if (!(iap->ia_valid & ATTR_DELEG))
                iap->ia_valid |= ATTR_CTIME;

        return notify_change(&nop_mnt_idmap, dentry, iap, NULL);
}

/**
 * nfsd_setattr - Set various file attributes.
 * @rqstp: controlling RPC transaction
 * @fhp: filehandle of target
 * @attr: attributes to set
 * @guardtime: do not act if ctime.tv_sec does not match this timestamp
 *
 * This call may adjust the contents of @attr (in particular, this
 * call may change the bits in the na_iattr.ia_valid field).
 *
 * Returns nfs_ok on success, otherwise an NFS status code is
 * returned. Caller must release @fhp by calling fh_put in either
 * case.
 */
__be32
nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp,
             struct nfsd_attrs *attr, const struct timespec64 *guardtime)
{
        struct dentry   *dentry;
        struct inode    *inode;
        struct iattr    *iap = attr->na_iattr;
        int             accmode = NFSD_MAY_SATTR;
        umode_t         ftype = 0;
        __be32          err;
        int             host_err = 0;
        bool            get_write_count;
        bool            size_change = (iap->ia_valid & ATTR_SIZE);
        int             retries;

        trace_nfsd_vfs_setattr(rqstp, fhp, iap, guardtime);

        if (iap->ia_valid & ATTR_SIZE) {
                accmode |= NFSD_MAY_WRITE|NFSD_MAY_OWNER_OVERRIDE;
                ftype = S_IFREG;
        }

        /*
         * If utimes(2) and friends are called with times not NULL, we should
         * not set NFSD_MAY_WRITE bit. Otherwise fh_verify->nfsd_permission
         * will return EACCES, when the caller's effective UID does not match
         * the owner of the file, and the caller is not privileged. In this
         * situation, we should return EPERM(notify_change will return this).
         */
        if (iap->ia_valid & (ATTR_ATIME | ATTR_MTIME)) {
                accmode |= NFSD_MAY_OWNER_OVERRIDE;
                if (!(iap->ia_valid & (ATTR_ATIME_SET | ATTR_MTIME_SET)))
                        accmode |= NFSD_MAY_WRITE;
        }

        /* Callers that do fh_verify should do the fh_want_write: */
        get_write_count = !fhp->fh_dentry;

        /* Get inode */
        err = fh_verify(rqstp, fhp, ftype, accmode);
        if (err)
                return err;
        if (get_write_count) {
                host_err = fh_want_write(fhp);
                if (host_err)
                        goto out;
        }

        dentry = fhp->fh_dentry;
        inode = d_inode(dentry);

        nfsd_sanitize_attrs(inode, iap);

        /*
         * The size case is special, it changes the file in addition to the
         * attributes, and file systems don't expect it to be mixed with
         * "random" attribute changes.  We thus split out the size change
         * into a separate call to ->setattr, and do the rest as a separate
         * setattr call.
         */
        if (size_change) {
                err = nfsd_get_write_access(rqstp, fhp, iap);
                if (err)
                        return err;
        }

        inode_lock(inode);
        err = fh_fill_pre_attrs(fhp);
        if (err)
                goto out_unlock;

        if (guardtime) {
                struct timespec64 ctime = inode_get_ctime(inode);
                if ((u32)guardtime->tv_sec != (u32)ctime.tv_sec ||
                    guardtime->tv_nsec != ctime.tv_nsec) {
                        err = nfserr_notsync;
                        goto out_fill_attrs;
                }
        }

        for (retries = 1;;) {
                struct iattr attrs;

                /*
                 * notify_change() can alter its iattr argument, making
                 * @iap unsuitable for submission multiple times. Make a
                 * copy for every loop iteration.
                 */
                attrs = *iap;
                host_err = __nfsd_setattr(dentry, &attrs);
                if (host_err != -EAGAIN || !retries--)
                        break;
                if (!nfsd_wait_for_delegreturn(rqstp, inode))
                        break;
        }
        if (attr->na_seclabel && attr->na_seclabel->len)
                attr->na_labelerr = security_inode_setsecctx(dentry,
                        attr->na_seclabel->data, attr->na_seclabel->len);
        if (IS_ENABLED(CONFIG_FS_POSIX_ACL) && attr->na_dpacl) {
                if (!S_ISDIR(inode->i_mode))
                        attr->na_dpaclerr = -EINVAL;
                else if (attr->na_dpacl->a_count > 0)
                        /* a_count == 0 means delete the ACL. */
                        attr->na_dpaclerr = set_posix_acl(&nop_mnt_idmap,
                                                dentry, ACL_TYPE_DEFAULT,
                                                attr->na_dpacl);
                else
                        attr->na_dpaclerr = set_posix_acl(&nop_mnt_idmap,
                                                dentry, ACL_TYPE_DEFAULT,
                                                NULL);
        }
        if (IS_ENABLED(CONFIG_FS_POSIX_ACL) && attr->na_pacl) {
                /*
                 * For any file system that is not ACL_SCOPE_FILE_OBJECT,
                 * a_count == 0 MUST reply nfserr_inval.
                 * For a file system that is ACL_SCOPE_FILE_OBJECT,
                 * a_count == 0 deletes the ACL.
                 * XXX File systems that are ACL_SCOPE_FILE_OBJECT
                 * are not yet supported.
                 */
                if (attr->na_pacl->a_count > 0)
                        attr->na_paclerr = set_posix_acl(&nop_mnt_idmap,
                                                        dentry, ACL_TYPE_ACCESS,
                                                        attr->na_pacl);
                else
                        attr->na_paclerr = -EINVAL;
        }
out_fill_attrs:
        /*
         * RFC 1813 Section 3.3.2 does not mandate that an NFS server
         * returns wcc_data for SETATTR. Some client implementations
         * depend on receiving wcc_data, however, to sort out partial
         * updates (eg., the client requested that size and mode be
         * modified, but the server changed only the file mode).
         */
        fh_fill_post_attrs(fhp);
out_unlock:
        inode_unlock(inode);
        if (size_change)
                put_write_access(inode);
out:
        if (!host_err)
                host_err = commit_metadata(fhp);
        return err != 0 ? err : nfserrno(host_err);
}

#if defined(CONFIG_NFSD_V4)
/*
 * NFS junction information is stored in an extended attribute.
 */
#define NFSD_JUNCTION_XATTR_NAME        XATTR_TRUSTED_PREFIX "junction.nfs"

/**
 * nfsd4_is_junction - Test if an object could be an NFS junction
 *
 * @dentry: object to test
 *
 * Returns 1 if "dentry" appears to contain NFS junction information.
 * Otherwise 0 is returned.
 */
int nfsd4_is_junction(struct dentry *dentry)
{
        struct inode *inode = d_inode(dentry);

        if (inode == NULL)
                return 0;
        if (inode->i_mode & S_IXUGO)
                return 0;
        if (!(inode->i_mode & S_ISVTX))
                return 0;
        if (vfs_getxattr(&nop_mnt_idmap, dentry, NFSD_JUNCTION_XATTR_NAME,
                         NULL, 0) <= 0)
                return 0;
        return 1;
}

static struct nfsd4_compound_state *nfsd4_get_cstate(struct svc_rqst *rqstp)
{
        return &((struct nfsd4_compoundres *)rqstp->rq_resp)->cstate;
}

__be32 nfsd4_clone_file_range(struct svc_rqst *rqstp,
                struct nfsd_file *nf_src, u64 src_pos,
                struct nfsd_file *nf_dst, u64 dst_pos,
                u64 count, bool sync)
{
        struct file *src = nf_src->nf_file;
        struct file *dst = nf_dst->nf_file;
        errseq_t since;
        loff_t cloned;
        __be32 ret = 0;

        since = READ_ONCE(dst->f_wb_err);
        cloned = vfs_clone_file_range(src, src_pos, dst, dst_pos, count, 0);
        if (cloned < 0) {
                ret = nfserrno(cloned);
                goto out_err;
        }
        if (count && cloned != count) {
                ret = nfserrno(-EINVAL);
                goto out_err;
        }
        if (sync) {
                loff_t dst_end = count ? dst_pos + count - 1 : LLONG_MAX;
                int status = vfs_fsync_range(dst, dst_pos, dst_end, 0);

                if (!status)
                        status = filemap_check_wb_err(dst->f_mapping, since);
                if (!status)
                        status = commit_inode_metadata(file_inode(src));
                if (status < 0) {
                        struct nfsd_net *nn = net_generic(nf_dst->nf_net,
                                                          nfsd_net_id);

                        trace_nfsd_clone_file_range_err(rqstp,
                                        &nfsd4_get_cstate(rqstp)->save_fh,
                                        src_pos,
                                        &nfsd4_get_cstate(rqstp)->current_fh,
                                        dst_pos,
                                        count, status);
                        commit_reset_write_verifier(nn, rqstp, status);
                        ret = nfserrno(status);
                }
        }
out_err:
        return ret;
}

ssize_t nfsd_copy_file_range(struct file *src, u64 src_pos, struct file *dst,
                             u64 dst_pos, u64 count)
{
        ssize_t ret;

        /*
         * Limit copy to 4MB to prevent indefinitely blocking an nfsd
         * thread and client rpc slot.  The choice of 4MB is somewhat
         * arbitrary.  We might instead base this on r/wsize, or make it
         * tunable, or use a time instead of a byte limit, or implement
         * asynchronous copy.  In theory a client could also recognize a
         * limit like this and pipeline multiple COPY requests.
         */
        count = min_t(u64, count, 1 << 22);
        ret = vfs_copy_file_range(src, src_pos, dst, dst_pos, count, 0);

        if (ret == -EOPNOTSUPP || ret == -EXDEV)
                ret = vfs_copy_file_range(src, src_pos, dst, dst_pos, count,
                                          COPY_FILE_SPLICE);
        return ret;
}

__be32 nfsd4_vfs_fallocate(struct svc_rqst *rqstp, struct svc_fh *fhp,
                           struct file *file, loff_t offset, loff_t len,
                           int flags)
{
        int error;

        if (!S_ISREG(file_inode(file)->i_mode))
                return nfserr_inval;

        error = vfs_fallocate(file, flags, offset, len);
        if (!error)
                error = commit_metadata(fhp);

        return nfserrno(error);
}
#endif /* defined(CONFIG_NFSD_V4) */

/*
 * Check server access rights to a file system object
 */
struct accessmap {
        u32             access;
        int             how;
};
static struct accessmap nfs3_regaccess[] = {
    {   NFS3_ACCESS_READ,       NFSD_MAY_READ                   },
    {   NFS3_ACCESS_EXECUTE,    NFSD_MAY_EXEC                   },
    {   NFS3_ACCESS_MODIFY,     NFSD_MAY_WRITE|NFSD_MAY_TRUNC   },
    {   NFS3_ACCESS_EXTEND,     NFSD_MAY_WRITE                  },

#ifdef CONFIG_NFSD_V4
    {   NFS4_ACCESS_XAREAD,     NFSD_MAY_READ                   },
    {   NFS4_ACCESS_XAWRITE,    NFSD_MAY_WRITE                  },
    {   NFS4_ACCESS_XALIST,     NFSD_MAY_READ                   },
#endif

    {   0,                      0                               }
};

static struct accessmap nfs3_diraccess[] = {
    {   NFS3_ACCESS_READ,       NFSD_MAY_READ                   },
    {   NFS3_ACCESS_LOOKUP,     NFSD_MAY_EXEC                   },
    {   NFS3_ACCESS_MODIFY,     NFSD_MAY_EXEC|NFSD_MAY_WRITE|NFSD_MAY_TRUNC},
    {   NFS3_ACCESS_EXTEND,     NFSD_MAY_EXEC|NFSD_MAY_WRITE    },
    {   NFS3_ACCESS_DELETE,     NFSD_MAY_REMOVE                 },

#ifdef CONFIG_NFSD_V4
    {   NFS4_ACCESS_XAREAD,     NFSD_MAY_READ                   },
    {   NFS4_ACCESS_XAWRITE,    NFSD_MAY_WRITE                  },
    {   NFS4_ACCESS_XALIST,     NFSD_MAY_READ                   },
#endif

    {   0,                      0                               }
};

static struct accessmap nfs3_anyaccess[] = {
        /* Some clients - Solaris 2.6 at least, make an access call
         * to the server to check for access for things like /dev/null
         * (which really, the server doesn't care about).  So
         * We provide simple access checking for them, looking
         * mainly at mode bits, and we make sure to ignore read-only
         * filesystem checks
         */
    {   NFS3_ACCESS_READ,       NFSD_MAY_READ                   },
    {   NFS3_ACCESS_EXECUTE,    NFSD_MAY_EXEC                   },
    {   NFS3_ACCESS_MODIFY,     NFSD_MAY_WRITE|NFSD_MAY_LOCAL_ACCESS    },
    {   NFS3_ACCESS_EXTEND,     NFSD_MAY_WRITE|NFSD_MAY_LOCAL_ACCESS    },

    {   0,                      0                               }
};

__be32
nfsd_access(struct svc_rqst *rqstp, struct svc_fh *fhp, u32 *access, u32 *supported)
{
        struct accessmap        *map;
        struct svc_export       *export;
        struct dentry           *dentry;
        u32                     query, result = 0, sresult = 0;
        __be32                  error;

        error = fh_verify(rqstp, fhp, 0, NFSD_MAY_NOP);
        if (error)
                goto out;

        export = fhp->fh_export;
        dentry = fhp->fh_dentry;

        if (d_is_reg(dentry))
                map = nfs3_regaccess;
        else if (d_is_dir(dentry))
                map = nfs3_diraccess;
        else
                map = nfs3_anyaccess;


        query = *access;
        for  (; map->access; map++) {
                if (map->access & query) {
                        __be32 err2;

                        sresult |= map->access;

                        err2 = nfsd_permission(&rqstp->rq_cred, export,
                                               dentry, map->how);
                        switch (err2) {
                        case nfs_ok:
                                result |= map->access;
                                break;
                                
                        /* the following error codes just mean the access was not allowed,
                         * rather than an error occurred */
                        case nfserr_rofs:
                        case nfserr_acces:
                        case nfserr_perm:
                                /* simply don't "or" in the access bit. */
                                break;
                        default:
                                error = err2;
                                goto out;
                        }
                }
        }
        *access = result;
        if (supported)
                *supported = sresult;

 out:
        return error;
}

int nfsd_open_break_lease(struct inode *inode, int access)
{
        unsigned int mode;

        if (access & NFSD_MAY_NOT_BREAK_LEASE)
                return 0;
        mode = (access & NFSD_MAY_WRITE) ? O_WRONLY : O_RDONLY;
        return break_lease(inode, mode | O_NONBLOCK);
}

/*
 * Open an existing file or directory.
 * The may_flags argument indicates the type of open (read/write/lock)
 * and additional flags.
 * N.B. After this call fhp needs an fh_put
 */
static int
__nfsd_open(struct svc_fh *fhp, umode_t type, int may_flags, struct file **filp)
{
        struct path     path;
        struct inode    *inode;
        struct file     *file;
        int             flags = O_RDONLY|O_LARGEFILE;
        int             host_err = -EPERM;

        path.mnt = fhp->fh_export->ex_path.mnt;
        path.dentry = fhp->fh_dentry;
        inode = d_inode(path.dentry);

        if (IS_APPEND(inode) && (may_flags & NFSD_MAY_WRITE))
                goto out;

        if (!inode->i_fop)
                goto out;

        host_err = nfsd_open_break_lease(inode, may_flags);
        if (host_err) /* NOMEM or WOULDBLOCK */
                goto out;

        if (may_flags & NFSD_MAY_WRITE) {
                if (may_flags & NFSD_MAY_READ)
                        flags = O_RDWR|O_LARGEFILE;
                else
                        flags = O_WRONLY|O_LARGEFILE;
        }

        file = dentry_open(&path, flags, current_cred());
        if (IS_ERR(file)) {
                host_err = PTR_ERR(file);
                goto out;
        }

        host_err = security_file_post_open(file, may_flags);
        if (host_err) {
                fput(file);
                goto out;
        }

        *filp = file;
out:
        return host_err;
}

__be32
nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type,
                int may_flags, struct file **filp)
{
        __be32 err;
        int host_err;
        bool retried = false;

        /*
         * If we get here, then the client has already done an "open",
         * and (hopefully) checked permission - so allow OWNER_OVERRIDE
         * in case a chmod has now revoked permission.
         *
         * Arguably we should also allow the owner override for
         * directories, but we never have and it doesn't seem to have
         * caused anyone a problem.  If we were to change this, note
         * also that our filldir callbacks would need a variant of
         * lookup_one_positive_unlocked() that doesn't check permissions.
         */
        if (type == S_IFREG)
                may_flags |= NFSD_MAY_OWNER_OVERRIDE;
retry:
        err = fh_verify(rqstp, fhp, type, may_flags);
        if (!err) {
                host_err = __nfsd_open(fhp, type, may_flags, filp);
                if (host_err == -EOPENSTALE && !retried) {
                        retried = true;
                        fh_put(fhp);
                        goto retry;
                }
                err = nfserrno(host_err);
        }
        return err;
}

/**
 * nfsd_open_verified - Open a regular file for the filecache
 * @fhp: NFS filehandle of the file to open
 * @type: S_IFMT inode type allowed (0 means any type is allowed)
 * @may_flags: internal permission flags
 * @filp: OUT: open "struct file *"
 *
 * Returns zero on success, or a negative errno value.
 */
int
nfsd_open_verified(struct svc_fh *fhp, umode_t type, int may_flags, struct file **filp)
{
        return __nfsd_open(fhp, type, may_flags, filp);
}

/*
 * Grab and keep cached pages associated with a file in the svc_rqst
 * so that they can be passed to the network sendmsg routines
 * directly. They will be released after the sending has completed.
 *
 * Return values: Number of bytes consumed, or -EIO if there are no
 * remaining pages in rqstp->rq_pages.
 */
static int
nfsd_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
                  struct splice_desc *sd)
{
        struct svc_rqst *rqstp = sd->u.data;
        struct page *page = buf->page;  // may be a compound one
        unsigned offset = buf->offset;
        struct page *last_page;

        last_page = page + (offset + sd->len - 1) / PAGE_SIZE;
        for (page += offset / PAGE_SIZE; page <= last_page; page++) {
                /*
                 * Skip page replacement when extending the contents of the
                 * current page.  But note that we may get two zero_pages in a
                 * row from shmem.
                 */
                if (page == *(rqstp->rq_next_page - 1) &&
                    offset_in_page(rqstp->rq_res.page_base +
                                   rqstp->rq_res.page_len))
                        continue;
                if (unlikely(!svc_rqst_replace_page(rqstp, page)))
                        return -EIO;
        }
        if (rqstp->rq_res.page_len == 0)        // first call
                rqstp->rq_res.page_base = offset % PAGE_SIZE;
        rqstp->rq_res.page_len += sd->len;
        return sd->len;
}

static int nfsd_direct_splice_actor(struct pipe_inode_info *pipe,
                                    struct splice_desc *sd)
{
        return __splice_from_pipe(pipe, sd, nfsd_splice_actor);
}

static u32 nfsd_eof_on_read(struct file *file, loff_t offset, ssize_t len,
                size_t expected)
{
        if (expected != 0 && len == 0)
                return 1;
        if (offset+len >= i_size_read(file_inode(file)))
                return 1;
        return 0;
}

static __be32 nfsd_finish_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
                               struct file *file, loff_t offset,
                               unsigned long *count, u32 *eof, ssize_t host_err)
{
        if (host_err >= 0) {
                struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);

                nfsd_stats_io_read_add(nn, fhp->fh_export, host_err);
                *eof = nfsd_eof_on_read(file, offset, host_err, *count);
                *count = host_err;
                fsnotify_access(file);
                trace_nfsd_read_io_done(rqstp, fhp, offset, *count);
                return 0;
        } else {
                trace_nfsd_read_err(rqstp, fhp, offset, host_err);
                return nfserrno(host_err);
        }
}

/**
 * nfsd_splice_read - Perform a VFS read using a splice pipe
 * @rqstp: RPC transaction context
 * @fhp: file handle of file to be read
 * @file: opened struct file of file to be read
 * @offset: starting byte offset
 * @count: IN: requested number of bytes; OUT: number of bytes read
 * @eof: OUT: set non-zero if operation reached the end of the file
 *
 * Returns nfs_ok on success, otherwise an nfserr stat value is
 * returned.
 */
__be32 nfsd_splice_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
                        struct file *file, loff_t offset, unsigned long *count,
                        u32 *eof)
{
        struct splice_desc sd = {
                .len            = 0,
                .total_len      = *count,
                .pos            = offset,
                .u.data         = rqstp,
        };
        ssize_t host_err;

        trace_nfsd_read_splice(rqstp, fhp, offset, *count);
        host_err = rw_verify_area(READ, file, &offset, *count);
        if (!host_err)
                host_err = splice_direct_to_actor(file, &sd,
                                                  nfsd_direct_splice_actor);
        return nfsd_finish_read(rqstp, fhp, file, offset, count, eof, host_err);
}

/*
 * The byte range of the client's READ request is expanded on both ends
 * until it meets the underlying file system's direct I/O alignment
 * requirements. After the internal read is complete, the byte range of
 * the NFS READ payload is reduced to the byte range that was originally
 * requested.
 *
 * Note that a direct read can be done only when the xdr_buf containing
 * the NFS READ reply does not already have contents in its .pages array.
 * This is due to potentially restrictive alignment requirements on the
 * read buffer. When .page_len and @base are zero, the .pages array is
 * guaranteed to be page-aligned.
 */
static noinline_for_stack __be32
nfsd_direct_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
                 struct nfsd_file *nf, loff_t offset, unsigned long *count,
                 u32 *eof)
{
        u64 dio_start, dio_end;
        unsigned long v, total;
        struct iov_iter iter;
        struct kiocb kiocb;
        ssize_t host_err;
        size_t len;

        init_sync_kiocb(&kiocb, nf->nf_file);
        kiocb.ki_flags |= IOCB_DIRECT;

        /* Read a properly-aligned region of bytes into rq_bvec */
        dio_start = round_down(offset, nf->nf_dio_read_offset_align);
        dio_end = round_up((u64)offset + *count, nf->nf_dio_read_offset_align);

        kiocb.ki_pos = dio_start;

        v = 0;
        total = dio_end - dio_start;
        while (total && v < rqstp->rq_maxpages &&
               rqstp->rq_next_page < rqstp->rq_page_end) {
                len = min_t(size_t, total, PAGE_SIZE);
                bvec_set_page(&rqstp->rq_bvec[v], *rqstp->rq_next_page,
                              len, 0);

                total -= len;
                ++rqstp->rq_next_page;
                ++v;
        }

        trace_nfsd_read_direct(rqstp, fhp, offset, *count - total);
        iov_iter_bvec(&iter, ITER_DEST, rqstp->rq_bvec, v,
                      dio_end - dio_start - total);

        host_err = vfs_iocb_iter_read(nf->nf_file, &kiocb, &iter);
        if (host_err >= 0) {
                unsigned int pad = offset - dio_start;

                /* The returned payload starts after the pad */
                rqstp->rq_res.page_base = pad;

                /* Compute the count of bytes to be returned */
                if (host_err > pad + *count)
                        host_err = *count;
                else if (host_err > pad)
                        host_err -= pad;
                else
                        host_err = 0;
        } else if (unlikely(host_err == -EINVAL)) {
                struct inode *inode = d_inode(fhp->fh_dentry);

                pr_info_ratelimited("nfsd: Direct I/O alignment failure on %s/%ld\n",
                                    inode->i_sb->s_id, inode->i_ino);
                host_err = -ESERVERFAULT;
        }

        return nfsd_finish_read(rqstp, fhp, nf->nf_file, offset, count,
                                eof, host_err);
}

/**
 * nfsd_iter_read - Perform a VFS read using an iterator
 * @rqstp: RPC transaction context
 * @fhp: file handle of file to be read
 * @nf: opened struct nfsd_file of file to be read
 * @offset: starting byte offset
 * @count: IN: requested number of bytes; OUT: number of bytes read
 * @base: offset in first page of read buffer
 * @eof: OUT: set non-zero if operation reached the end of the file
 *
 * Some filesystems or situations cannot use nfsd_splice_read. This
 * function is the slightly less-performant fallback for those cases.
 *
 * Returns nfs_ok on success, otherwise an nfserr stat value is
 * returned.
 */
__be32 nfsd_iter_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
                      struct nfsd_file *nf, loff_t offset, unsigned long *count,
                      unsigned int base, u32 *eof)
{
        struct file *file = nf->nf_file;
        unsigned long v, total;
        struct iov_iter iter;
        struct kiocb kiocb;
        ssize_t host_err;
        size_t len;

        init_sync_kiocb(&kiocb, file);

        switch (nfsd_io_cache_read) {
        case NFSD_IO_BUFFERED:
                break;
        case NFSD_IO_DIRECT:
                /* When dio_read_offset_align is zero, dio is not supported */
                if (nf->nf_dio_read_offset_align && !rqstp->rq_res.page_len)
                        return nfsd_direct_read(rqstp, fhp, nf, offset,
                                                count, eof);
                fallthrough;
        case NFSD_IO_DONTCACHE:
                if (file->f_op->fop_flags & FOP_DONTCACHE)
                        kiocb.ki_flags = IOCB_DONTCACHE;
                break;
        }

        kiocb.ki_pos = offset;

        v = 0;
        total = *count;
        while (total && v < rqstp->rq_maxpages &&
               rqstp->rq_next_page < rqstp->rq_page_end) {
                len = min_t(size_t, total, PAGE_SIZE - base);
                bvec_set_page(&rqstp->rq_bvec[v], *rqstp->rq_next_page,
                              len, base);

                total -= len;
                ++rqstp->rq_next_page;
                ++v;
                base = 0;
        }

        trace_nfsd_read_vector(rqstp, fhp, offset, *count - total);
        iov_iter_bvec(&iter, ITER_DEST, rqstp->rq_bvec, v, *count - total);
        host_err = vfs_iocb_iter_read(file, &kiocb, &iter);
        return nfsd_finish_read(rqstp, fhp, file, offset, count, eof, host_err);
}

/*
 * Gathered writes: If another process is currently writing to the file,
 * there's a high chance this is another nfsd (triggered by a bulk write
 * from a client's biod). Rather than syncing the file with each write
 * request, we sleep for 10 msec.
 *
 * I don't know if this roughly approximates C. Juszak's idea of
 * gathered writes, but it's a nice and simple solution (IMHO), and it
 * seems to work:-)
 *
 * Note: we do this only in the NFSv2 case, since v3 and higher have a
 * better tool (separate unstable writes and commits) for solving this
 * problem.
 */
static int wait_for_concurrent_writes(struct file *file)
{
        struct inode *inode = file_inode(file);
        static ino_t last_ino;
        static dev_t last_dev;
        int err = 0;

        if (atomic_read(&inode->i_writecount) > 1
            || (last_ino == inode->i_ino && last_dev == inode->i_sb->s_dev)) {
                dprintk("nfsd: write defer %d\n", task_pid_nr(current));
                msleep(10);
                dprintk("nfsd: write resume %d\n", task_pid_nr(current));
        }

        if (inode_state_read_once(inode) & I_DIRTY) {
                dprintk("nfsd: write sync %d\n", task_pid_nr(current));
                err = vfs_fsync(file, 0);
        }
        last_ino = inode->i_ino;
        last_dev = inode->i_sb->s_dev;
        return err;
}

struct nfsd_write_dio_seg {
        struct iov_iter                 iter;
        int                             flags;
};

static unsigned long
iov_iter_bvec_offset(const struct iov_iter *iter)
{
        return (unsigned long)(iter->bvec->bv_offset + iter->iov_offset);
}

static void
nfsd_write_dio_seg_init(struct nfsd_write_dio_seg *segment,
                        struct bio_vec *bvec, unsigned int nvecs,
                        unsigned long total, size_t start, size_t len,
                        struct kiocb *iocb)
{
        iov_iter_bvec(&segment->iter, ITER_SOURCE, bvec, nvecs, total);
        if (start)
                iov_iter_advance(&segment->iter, start);
        iov_iter_truncate(&segment->iter, len);
        segment->flags = iocb->ki_flags;
}

static unsigned int
nfsd_write_dio_iters_init(struct nfsd_file *nf, struct bio_vec *bvec,
                          unsigned int nvecs, struct kiocb *iocb,
                          unsigned long total,
                          struct nfsd_write_dio_seg segments[3])
{
        u32 offset_align = nf->nf_dio_offset_align;
        loff_t prefix_end, orig_end, middle_end;
        u32 mem_align = nf->nf_dio_mem_align;
        size_t prefix, middle, suffix;
        loff_t offset = iocb->ki_pos;
        unsigned int nsegs = 0;

        /*
         * Check if direct I/O is feasible for this write request.
         * If alignments are not available, the write is too small,
         * or no alignment can be found, fall back to buffered I/O.
         */
        if (unlikely(!mem_align || !offset_align) ||
            unlikely(total < max(offset_align, mem_align)))
                goto no_dio;

        prefix_end = round_up(offset, offset_align);
        orig_end = offset + total;
        middle_end = round_down(orig_end, offset_align);

        prefix = prefix_end - offset;
        middle = middle_end - prefix_end;
        suffix = orig_end - middle_end;

        if (!middle)
                goto no_dio;

        if (prefix)
                nfsd_write_dio_seg_init(&segments[nsegs++], bvec,
                                        nvecs, total, 0, prefix, iocb);

        nfsd_write_dio_seg_init(&segments[nsegs], bvec, nvecs,
                                total, prefix, middle, iocb);

        /*
         * Check if the bvec iterator is aligned for direct I/O.
         *
         * bvecs generated from RPC receive buffers are contiguous: After
         * the first bvec, all subsequent bvecs start at bv_offset zero
         * (page-aligned). Therefore, only the first bvec is checked.
         */
        if (iov_iter_bvec_offset(&segments[nsegs].iter) & (mem_align - 1))
                goto no_dio;
        segments[nsegs].flags |= IOCB_DIRECT;
        nsegs++;

        if (suffix)
                nfsd_write_dio_seg_init(&segments[nsegs++], bvec, nvecs, total,
                                        prefix + middle, suffix, iocb);

        return nsegs;

no_dio:
        /* No DIO alignment possible - pack into single non-DIO segment. */
        nfsd_write_dio_seg_init(&segments[0], bvec, nvecs, total, 0,
                                total, iocb);
        return 1;
}

static noinline_for_stack int
nfsd_direct_write(struct svc_rqst *rqstp, struct svc_fh *fhp,
                  struct nfsd_file *nf, unsigned int nvecs,
                  unsigned long *cnt, struct kiocb *kiocb)
{
        struct nfsd_write_dio_seg segments[3];
        struct file *file = nf->nf_file;
        unsigned int nsegs, i;
        ssize_t host_err;

        nsegs = nfsd_write_dio_iters_init(nf, rqstp->rq_bvec, nvecs,
                                          kiocb, *cnt, segments);

        *cnt = 0;
        for (i = 0; i < nsegs; i++) {
                kiocb->ki_flags = segments[i].flags;
                if (kiocb->ki_flags & IOCB_DIRECT)
                        trace_nfsd_write_direct(rqstp, fhp, kiocb->ki_pos,
                                                segments[i].iter.count);
                else {
                        trace_nfsd_write_vector(rqstp, fhp, kiocb->ki_pos,
                                                segments[i].iter.count);
                        /*
                         * Mark the I/O buffer as evict-able to reduce
                         * memory contention.
                         */
                        if (nf->nf_file->f_op->fop_flags & FOP_DONTCACHE)
                                kiocb->ki_flags |= IOCB_DONTCACHE;
                }

                host_err = vfs_iocb_iter_write(file, kiocb, &segments[i].iter);
                if (host_err < 0)
                        return host_err;
                *cnt += host_err;
                if (host_err < segments[i].iter.count)
                        break;  /* partial write */
        }

        return 0;
}

/**
 * nfsd_vfs_write - write data to an already-open file
 * @rqstp: RPC execution context
 * @fhp: File handle of file to write into
 * @nf: An open file matching @fhp
 * @offset: Byte offset of start
 * @payload: xdr_buf containing the write payload
 * @cnt: IN: number of bytes to write, OUT: number of bytes actually written
 * @stable: An NFS stable_how value
 * @verf: NFS WRITE verifier
 *
 * Upon return, caller must invoke fh_put on @fhp.
 *
 * Return values:
 *   An nfsstat value in network byte order.
 */
__be32
nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp,
               struct nfsd_file *nf, loff_t offset,
               const struct xdr_buf *payload, unsigned long *cnt,
               int stable, __be32 *verf)
{
        struct nfsd_net         *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
        struct file             *file = nf->nf_file;
        struct super_block      *sb = file_inode(file)->i_sb;
        struct kiocb            kiocb;
        struct svc_export       *exp;
        struct iov_iter         iter;
        errseq_t                since;
        __be32                  nfserr;
        int                     host_err;
        unsigned long           exp_op_flags = 0;
        unsigned int            pflags = current->flags;
        bool                    restore_flags = false;
        unsigned int            nvecs;

        trace_nfsd_write_opened(rqstp, fhp, offset, *cnt);

        if (sb->s_export_op)
                exp_op_flags = sb->s_export_op->flags;

        if (test_bit(RQ_LOCAL, &rqstp->rq_flags) &&
            !(exp_op_flags & EXPORT_OP_REMOTE_FS)) {
                /*
                 * We want throttling in balance_dirty_pages()
                 * and shrink_inactive_list() to only consider
                 * the backingdev we are writing to, so that nfs to
                 * localhost doesn't cause nfsd to lock up due to all
                 * the client's dirty pages or its congested queue.
                 */
                current->flags |= PF_LOCAL_THROTTLE;
                restore_flags = true;
        }

        exp = fhp->fh_export;

        if (!EX_ISSYNC(exp))
                stable = NFS_UNSTABLE;
        init_sync_kiocb(&kiocb, file);
        kiocb.ki_pos = offset;
        if (likely(!fhp->fh_use_wgather)) {
                switch (stable) {
                case NFS_FILE_SYNC:
                        /* persist data and timestamps */
                        kiocb.ki_flags |= IOCB_DSYNC | IOCB_SYNC;
                        break;
                case NFS_DATA_SYNC:
                        /* persist data only */
                        kiocb.ki_flags |= IOCB_DSYNC;
                        break;
                }
        }

        nvecs = xdr_buf_to_bvec(rqstp->rq_bvec, rqstp->rq_maxpages, payload);

        since = READ_ONCE(file->f_wb_err);
        if (verf)
                nfsd_copy_write_verifier(verf, nn);

        switch (nfsd_io_cache_write) {
        case NFSD_IO_DIRECT:
                host_err = nfsd_direct_write(rqstp, fhp, nf, nvecs,
                                             cnt, &kiocb);
                break;
        case NFSD_IO_DONTCACHE:
                if (file->f_op->fop_flags & FOP_DONTCACHE)
                        kiocb.ki_flags |= IOCB_DONTCACHE;
                fallthrough;
        case NFSD_IO_BUFFERED:
                iov_iter_bvec(&iter, ITER_SOURCE, rqstp->rq_bvec, nvecs, *cnt);
                host_err = vfs_iocb_iter_write(file, &kiocb, &iter);
                if (host_err < 0)
                        break;
                *cnt = host_err;
                break;
        }
        if (host_err < 0) {
                commit_reset_write_verifier(nn, rqstp, host_err);
                goto out_nfserr;
        }
        nfsd_stats_io_write_add(nn, exp, *cnt);
        fsnotify_modify(file);
        host_err = filemap_check_wb_err(file->f_mapping, since);
        if (host_err < 0)
                goto out_nfserr;

        if (stable && fhp->fh_use_wgather) {
                host_err = wait_for_concurrent_writes(file);
                if (host_err < 0)
                        commit_reset_write_verifier(nn, rqstp, host_err);
        }

out_nfserr:
        if (host_err >= 0) {
                trace_nfsd_write_io_done(rqstp, fhp, offset, *cnt);
                nfserr = nfs_ok;
        } else {
                trace_nfsd_write_err(rqstp, fhp, offset, host_err);
                nfserr = nfserrno(host_err);
        }
        if (restore_flags)
                current_restore_flags(pflags, PF_LOCAL_THROTTLE);
        return nfserr;
}

/**
 * nfsd_read_splice_ok - check if spliced reading is supported
 * @rqstp: RPC transaction context
 *
 * Return values:
 *   %true: nfsd_splice_read() may be used
 *   %false: nfsd_splice_read() must not be used
 *
 * NFS READ normally uses splice to send data in-place. However the
 * data in cache can change after the reply's MIC is computed but
 * before the RPC reply is sent. To prevent the client from
 * rejecting the server-computed MIC in this somewhat rare case, do
 * not use splice with the GSS integrity and privacy services.
 */
bool nfsd_read_splice_ok(struct svc_rqst *rqstp)
{
        if (nfsd_disable_splice_read)
                return false;
        switch (svc_auth_flavor(rqstp)) {
        case RPC_AUTH_GSS_KRB5I:
        case RPC_AUTH_GSS_KRB5P:
                return false;
        }
        return true;
}

/**
 * nfsd_read - Read data from a file
 * @rqstp: RPC transaction context
 * @fhp: file handle of file to be read
 * @offset: starting byte offset
 * @count: IN: requested number of bytes; OUT: number of bytes read
 * @eof: OUT: set non-zero if operation reached the end of the file
 *
 * The caller must verify that there is enough space in @rqstp.rq_res
 * to perform this operation.
 *
 * N.B. After this call fhp needs an fh_put
 *
 * Returns nfs_ok on success, otherwise an nfserr stat value is
 * returned.
 */
__be32 nfsd_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
                 loff_t offset, unsigned long *count, u32 *eof)
{
        struct nfsd_file        *nf;
        struct file *file;
        __be32 err;

        trace_nfsd_read_start(rqstp, fhp, offset, *count);
        err = nfsd_file_acquire_gc(rqstp, fhp, NFSD_MAY_READ, &nf);
        if (err)
                return err;

        file = nf->nf_file;
        if (file->f_op->splice_read && nfsd_read_splice_ok(rqstp))
                err = nfsd_splice_read(rqstp, fhp, file, offset, count, eof);
        else
                err = nfsd_iter_read(rqstp, fhp, nf, offset, count, 0, eof);

        nfsd_file_put(nf);
        trace_nfsd_read_done(rqstp, fhp, offset, *count);
        return err;
}

/**
 * nfsd_write - open a file and write data to it
 * @rqstp: RPC execution context
 * @fhp: File handle of file to write into; nfsd_write() may modify it
 * @offset: Byte offset of start
 * @payload: xdr_buf containing the write payload
 * @cnt: IN: number of bytes to write, OUT: number of bytes actually written
 * @stable: An NFS stable_how value
 * @verf: NFS WRITE verifier
 *
 * Upon return, caller must invoke fh_put on @fhp.
 *
 * Return values:
 *   An nfsstat value in network byte order.
 */
__be32
nfsd_write(struct svc_rqst *rqstp, struct svc_fh *fhp, loff_t offset,
           const struct xdr_buf *payload, unsigned long *cnt, int stable,
           __be32 *verf)
{
        struct nfsd_file *nf;
        __be32 err;

        trace_nfsd_write_start(rqstp, fhp, offset, *cnt);

        err = nfsd_file_acquire_gc(rqstp, fhp, NFSD_MAY_WRITE, &nf);
        if (err)
                goto out;

        err = nfsd_vfs_write(rqstp, fhp, nf, offset, payload, cnt,
                             stable, verf);
        nfsd_file_put(nf);
out:
        trace_nfsd_write_done(rqstp, fhp, offset, *cnt);
        return err;
}

/**
 * nfsd_commit - Commit pending writes to stable storage
 * @rqstp: RPC request being processed
 * @fhp: NFS filehandle
 * @nf: target file
 * @offset: raw offset from beginning of file
 * @count: raw count of bytes to sync
 * @verf: filled in with the server's current write verifier
 *
 * Note: we guarantee that data that lies within the range specified
 * by the 'offset' and 'count' parameters will be synced. The server
 * is permitted to sync data that lies outside this range at the
 * same time.
 *
 * Unfortunately we cannot lock the file to make sure we return full WCC
 * data to the client, as locking happens lower down in the filesystem.
 *
 * Return values:
 *   An nfsstat value in network byte order.
 */
__be32
nfsd_commit(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
            u64 offset, u32 count, __be32 *verf)
{
        __be32                  err = nfs_ok;
        u64                     maxbytes;
        loff_t                  start, end;
        struct nfsd_net         *nn;

        trace_nfsd_commit_start(rqstp, fhp, offset, count);

        /*
         * Convert the client-provided (offset, count) range to a
         * (start, end) range. If the client-provided range falls
         * outside the maximum file size of the underlying FS,
         * clamp the sync range appropriately.
         */
        start = 0;
        end = LLONG_MAX;
        maxbytes = (u64)fhp->fh_dentry->d_sb->s_maxbytes;
        if (offset < maxbytes) {
                start = offset;
                if (count && (offset + count - 1 < maxbytes))
                        end = offset + count - 1;
        }

        nn = net_generic(nf->nf_net, nfsd_net_id);
        if (EX_ISSYNC(fhp->fh_export)) {
                errseq_t since = READ_ONCE(nf->nf_file->f_wb_err);
                int err2;

                err2 = vfs_fsync_range(nf->nf_file, start, end, 0);
                switch (err2) {
                case 0:
                        nfsd_copy_write_verifier(verf, nn);
                        err2 = filemap_check_wb_err(nf->nf_file->f_mapping,
                                                    since);
                        err = nfserrno(err2);
                        break;
                case -EINVAL:
                        err = nfserr_notsupp;
                        break;
                default:
                        commit_reset_write_verifier(nn, rqstp, err2);
                        err = nfserrno(err2);
                }
        } else
                nfsd_copy_write_verifier(verf, nn);

        trace_nfsd_commit_done(rqstp, fhp, offset, count);
        return err;
}

/**
 * nfsd_create_setattr - Set a created file's attributes
 * @rqstp: RPC transaction being executed
 * @fhp: NFS filehandle of parent directory
 * @resfhp: NFS filehandle of new object
 * @attrs: requested attributes of new object
 *
 * Returns nfs_ok on success, or an nfsstat in network byte order.
 */
__be32
nfsd_create_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp,
                    struct svc_fh *resfhp, struct nfsd_attrs *attrs)
{
        struct iattr *iap = attrs->na_iattr;
        __be32 status;

        /*
         * Mode has already been set by file creation.
         */
        iap->ia_valid &= ~ATTR_MODE;

        /*
         * Setting uid/gid works only for root.  Irix appears to
         * send along the gid on create when it tries to implement
         * setgid directories via NFS:
         */
        if (!uid_eq(current_fsuid(), GLOBAL_ROOT_UID))
                iap->ia_valid &= ~(ATTR_UID|ATTR_GID);

        /*
         * Callers expect new file metadata to be committed even
         * if the attributes have not changed.
         */
        if (nfsd_attrs_valid(attrs))
                status = nfsd_setattr(rqstp, resfhp, attrs, NULL);
        else
                status = nfserrno(commit_metadata(resfhp));

        /*
         * Transactional filesystems had a chance to commit changes
         * for both parent and child simultaneously making the
         * following commit_metadata a noop in many cases.
         */
        if (!status)
                status = nfserrno(commit_metadata(fhp));

        /*
         * Update the new filehandle to pick up the new attributes.
         */
        if (!status)
                status = fh_update(resfhp);

        return status;
}

/* HPUX client sometimes creates a file in mode 000, and sets size to 0.
 * setting size to 0 may fail for some specific file systems by the permission
 * checking which requires WRITE permission but the mode is 000.
 * we ignore the resizing(to 0) on the just new created file, since the size is
 * 0 after file created.
 *
 * call this only after vfs_create() is called.
 * */
static void
nfsd_check_ignore_resizing(struct iattr *iap)
{
        if ((iap->ia_valid & ATTR_SIZE) && (iap->ia_size == 0))
                iap->ia_valid &= ~ATTR_SIZE;
}

/* The parent directory should already be locked - we will unlock */
__be32
nfsd_create_locked(struct svc_rqst *rqstp, struct svc_fh *fhp,
                   struct nfsd_attrs *attrs,
                   int type, dev_t rdev, struct svc_fh *resfhp)
{
        struct dentry   *dentry, *dchild;
        struct inode    *dirp;
        struct iattr    *iap = attrs->na_iattr;
        __be32          err;
        int             host_err = 0;

        dentry = fhp->fh_dentry;
        dirp = d_inode(dentry);

        dchild = dget(resfhp->fh_dentry);
        err = nfsd_permission(&rqstp->rq_cred, fhp->fh_export, dentry,
                              NFSD_MAY_CREATE);
        if (err)
                goto out;

        if (!(iap->ia_valid & ATTR_MODE))
                iap->ia_mode = 0;
        iap->ia_mode = (iap->ia_mode & S_IALLUGO) | type;

        if (!IS_POSIXACL(dirp))
                iap->ia_mode &= ~current_umask();

        err = 0;
        switch (type) {
        case S_IFREG:
                host_err = vfs_create(&nop_mnt_idmap, dchild, iap->ia_mode, NULL);
                if (!host_err)
                        nfsd_check_ignore_resizing(iap);
                break;
        case S_IFDIR:
                dchild = vfs_mkdir(&nop_mnt_idmap, dirp, dchild, iap->ia_mode, NULL);
                if (IS_ERR(dchild)) {
                        host_err = PTR_ERR(dchild);
                } else if (d_is_negative(dchild)) {
                        err = nfserr_serverfault;
                        goto out;
                } else if (unlikely(dchild != resfhp->fh_dentry)) {
                        dput(resfhp->fh_dentry);
                        resfhp->fh_dentry = dget(dchild);
                }
                break;
        case S_IFCHR:
        case S_IFBLK:
        case S_IFIFO:
        case S_IFSOCK:
                host_err = vfs_mknod(&nop_mnt_idmap, dirp, dchild,
                                     iap->ia_mode, rdev, NULL);
                break;
        default:
                printk(KERN_WARNING "nfsd: bad file type %o in nfsd_create\n",
                       type);
                host_err = -EINVAL;
        }
        if (host_err < 0)
                goto out_nfserr;

        err = nfsd_create_setattr(rqstp, fhp, resfhp, attrs);

out:
        if (!err)
                fh_fill_post_attrs(fhp);
        end_creating(dchild);
        return err;

out_nfserr:
        err = nfserrno(host_err);
        goto out;
}

/*
 * Create a filesystem object (regular, directory, special).
 * Note that the parent directory is left locked.
 *
 * N.B. Every call to nfsd_create needs an fh_put for _both_ fhp and resfhp
 */
__be32
nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
            char *fname, int flen, struct nfsd_attrs *attrs,
            int type, dev_t rdev, struct svc_fh *resfhp)
{
        struct dentry   *dentry, *dchild = NULL;
        __be32          err;
        int             host_err;

        trace_nfsd_vfs_create(rqstp, fhp, type, fname, flen);

        if (isdotent(fname, flen))
                return nfserr_exist;

        err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_NOP);
        if (err)
                return err;

        dentry = fhp->fh_dentry;

        host_err = fh_want_write(fhp);
        if (host_err)
                return nfserrno(host_err);

        dchild = start_creating(&nop_mnt_idmap, dentry, &QSTR_LEN(fname, flen));
        host_err = PTR_ERR(dchild);
        if (IS_ERR(dchild))
                return nfserrno(host_err);

        err = fh_compose(resfhp, fhp->fh_export, dchild, fhp);
        if (err)
                goto out_unlock;
        err = fh_fill_pre_attrs(fhp);
        if (err != nfs_ok)
                goto out_unlock;
        err = nfsd_create_locked(rqstp, fhp, attrs, type, rdev, resfhp);
        /* nfsd_create_locked() unlocked the parent */
        dput(dchild);
        return err;

out_unlock:
        end_creating(dchild);
        return err;
}

/*
 * Read a symlink. On entry, *lenp must contain the maximum path length that
 * fits into the buffer. On return, it contains the true length.
 * N.B. After this call fhp needs an fh_put
 */
__be32
nfsd_readlink(struct svc_rqst *rqstp, struct svc_fh *fhp, char *buf, int *lenp)
{
        __be32          err;
        const char *link;
        struct path path;
        DEFINE_DELAYED_CALL(done);
        int len;

        err = fh_verify(rqstp, fhp, S_IFLNK, NFSD_MAY_NOP);
        if (unlikely(err))
                return err;

        path.mnt = fhp->fh_export->ex_path.mnt;
        path.dentry = fhp->fh_dentry;

        if (unlikely(!d_is_symlink(path.dentry)))
                return nfserr_inval;

        touch_atime(&path);

        link = vfs_get_link(path.dentry, &done);
        if (IS_ERR(link))
                return nfserrno(PTR_ERR(link));

        len = strlen(link);
        if (len < *lenp)
                *lenp = len;
        memcpy(buf, link, *lenp);
        do_delayed_call(&done);
        return 0;
}

/**
 * nfsd_symlink - Create a symlink and look up its inode
 * @rqstp: RPC transaction being executed
 * @fhp: NFS filehandle of parent directory
 * @fname: filename of the new symlink
 * @flen: length of @fname
 * @path: content of the new symlink (NUL-terminated)
 * @attrs: requested attributes of new object
 * @resfhp: NFS filehandle of new object
 *
 * N.B. After this call _both_ fhp and resfhp need an fh_put
 *
 * Returns nfs_ok on success, or an nfsstat in network byte order.
 */
__be32
nfsd_symlink(struct svc_rqst *rqstp, struct svc_fh *fhp,
             char *fname, int flen,
             char *path, struct nfsd_attrs *attrs,
             struct svc_fh *resfhp)
{
        struct dentry   *dentry, *dnew;
        __be32          err, cerr;
        int             host_err;

        trace_nfsd_vfs_symlink(rqstp, fhp, fname, flen, path);

        err = nfserr_noent;
        if (!flen || path[0] == '\0')
                goto out;
        err = nfserr_exist;
        if (isdotent(fname, flen))
                goto out;

        err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_CREATE);
        if (err)
                goto out;

        host_err = fh_want_write(fhp);
        if (host_err) {
                err = nfserrno(host_err);
                goto out;
        }

        dentry = fhp->fh_dentry;
        dnew = start_creating(&nop_mnt_idmap, dentry, &QSTR_LEN(fname, flen));
        if (IS_ERR(dnew)) {
                err = nfserrno(PTR_ERR(dnew));
                goto out_drop_write;
        }
        err = fh_fill_pre_attrs(fhp);
        if (err != nfs_ok)
                goto out_unlock;
        host_err = vfs_symlink(&nop_mnt_idmap, d_inode(dentry), dnew, path, NULL);
        err = nfserrno(host_err);
        cerr = fh_compose(resfhp, fhp->fh_export, dnew, fhp);
        if (!err)
                nfsd_create_setattr(rqstp, fhp, resfhp, attrs);
        fh_fill_post_attrs(fhp);
out_unlock:
        end_creating(dnew);
        if (!err)
                err = nfserrno(commit_metadata(fhp));
        if (!err)
                err = cerr;
out_drop_write:
        fh_drop_write(fhp);
out:
        return err;
}

/**
 * nfsd_link - create a link
 * @rqstp: RPC transaction context
 * @ffhp: the file handle of the directory where the new link is to be created
 * @name: the filename of the new link
 * @len: the length of @name in octets
 * @tfhp: the file handle of an existing file object
 *
 * After this call _both_ ffhp and tfhp need an fh_put.
 *
 * Returns a generic NFS status code in network byte-order.
 */
__be32
nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
                                char *name, int len, struct svc_fh *tfhp)
{
        struct dentry   *ddir, *dnew, *dold;
        struct inode    *dirp;
        int             type;
        __be32          err;
        int             host_err;

        trace_nfsd_vfs_link(rqstp, ffhp, tfhp, name, len);

        err = fh_verify(rqstp, ffhp, S_IFDIR, NFSD_MAY_CREATE);
        if (err)
                goto out;
        err = fh_verify(rqstp, tfhp, 0, NFSD_MAY_NOP);
        if (err)
                goto out;
        err = nfserr_isdir;
        if (d_is_dir(tfhp->fh_dentry))
                goto out;
        err = nfserr_perm;
        if (!len)
                goto out;
        err = nfserr_exist;
        if (isdotent(name, len))
                goto out;

        err = nfs_ok;
        type = d_inode(tfhp->fh_dentry)->i_mode & S_IFMT;
        host_err = fh_want_write(tfhp);
        if (host_err)
                goto out;

        ddir = ffhp->fh_dentry;
        dirp = d_inode(ddir);
        dnew = start_creating(&nop_mnt_idmap, ddir, &QSTR_LEN(name, len));

        if (IS_ERR(dnew)) {
                host_err = PTR_ERR(dnew);
                goto out_drop_write;
        }

        dold = tfhp->fh_dentry;

        err = nfserr_noent;
        if (d_really_is_negative(dold))
                goto out_unlock;
        err = fh_fill_pre_attrs(ffhp);
        if (err != nfs_ok)
                goto out_unlock;
        host_err = vfs_link(dold, &nop_mnt_idmap, dirp, dnew, NULL);
        fh_fill_post_attrs(ffhp);
out_unlock:
        end_creating(dnew);
        if (!host_err) {
                host_err = commit_metadata(ffhp);
                if (!host_err)
                        host_err = commit_metadata(tfhp);
        }

out_drop_write:
        fh_drop_write(tfhp);
        if (host_err == -EBUSY) {
                /*
                 * See RFC 8881 Section 18.9.4 para 1-2: NFSv4 LINK
                 * wants a status unique to the object type.
                 */
                if (type != S_IFDIR)
                        err = nfserr_file_open;
                else
                        err = nfserr_acces;
        }
out:
        return err != nfs_ok ? err : nfserrno(host_err);
}

static void
nfsd_close_cached_files(struct dentry *dentry)
{
        struct inode *inode = d_inode(dentry);

        if (inode && S_ISREG(inode->i_mode))
                nfsd_file_close_inode_sync(inode);
}

static bool
nfsd_has_cached_files(struct dentry *dentry)
{
        bool            ret = false;
        struct inode *inode = d_inode(dentry);

        if (inode && S_ISREG(inode->i_mode))
                ret = nfsd_file_is_cached(inode);
        return ret;
}

/**
 * nfsd_rename - rename a directory entry
 * @rqstp: RPC transaction context
 * @ffhp: the file handle of parent directory containing the entry to be renamed
 * @fname: the filename of directory entry to be renamed
 * @flen: the length of @fname in octets
 * @tfhp: the file handle of parent directory to contain the renamed entry
 * @tname: the filename of the new entry
 * @tlen: the length of @tlen in octets
 *
 * After this call _both_ ffhp and tfhp need an fh_put.
 *
 * Returns a generic NFS status code in network byte-order.
 */
__be32
nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
                            struct svc_fh *tfhp, char *tname, int tlen)
{
        struct dentry   *fdentry, *tdentry;
        int             type = S_IFDIR;
        struct renamedata rd = {};
        __be32          err;
        int             host_err;
        struct dentry   *close_cached;

        trace_nfsd_vfs_rename(rqstp, ffhp, tfhp, fname, flen, tname, tlen);

        err = fh_verify(rqstp, ffhp, S_IFDIR, NFSD_MAY_REMOVE);
        if (err)
                goto out;
        err = fh_verify(rqstp, tfhp, S_IFDIR, NFSD_MAY_CREATE);
        if (err)
                goto out;

        fdentry = ffhp->fh_dentry;

        tdentry = tfhp->fh_dentry;

        err = nfserr_perm;
        if (!flen || isdotent(fname, flen) || !tlen || isdotent(tname, tlen))
                goto out;

        err = nfserr_xdev;
        if (ffhp->fh_export->ex_path.mnt != tfhp->fh_export->ex_path.mnt)
                goto out;
        if (ffhp->fh_export->ex_path.dentry != tfhp->fh_export->ex_path.dentry)
                goto out;

retry:
        close_cached = NULL;
        host_err = fh_want_write(ffhp);
        if (host_err) {
                err = nfserrno(host_err);
                goto out;
        }

        rd.mnt_idmap    = &nop_mnt_idmap;
        rd.old_parent   = fdentry;
        rd.new_parent   = tdentry;

        host_err = start_renaming(&rd, 0, &QSTR_LEN(fname, flen),
                                  &QSTR_LEN(tname, tlen));

        if (host_err) {
                err = nfserrno(host_err);
                goto out_want_write;
        }
        err = fh_fill_pre_attrs(ffhp);
        if (err != nfs_ok)
                goto out_unlock;
        err = fh_fill_pre_attrs(tfhp);
        if (err != nfs_ok)
                goto out_unlock;

        type = d_inode(rd.old_dentry)->i_mode & S_IFMT;

        if (d_inode(rd.new_dentry))
                type = d_inode(rd.new_dentry)->i_mode & S_IFMT;

        if ((rd.new_dentry->d_sb->s_export_op->flags & EXPORT_OP_CLOSE_BEFORE_UNLINK) &&
            nfsd_has_cached_files(rd.new_dentry)) {
                close_cached = dget(rd.new_dentry);
                goto out_unlock;
        } else {
                int retries;

                for (retries = 1;;) {
                        host_err = vfs_rename(&rd);
                        if (host_err != -EAGAIN || !retries--)
                                break;
                        if (!nfsd_wait_for_delegreturn(rqstp, d_inode(rd.old_dentry)))
                                break;
                }
                if (!host_err) {
                        host_err = commit_metadata(tfhp);
                        if (!host_err)
                                host_err = commit_metadata(ffhp);
                }
        }
        if (host_err == -EBUSY) {
                /*
                 * See RFC 8881 Section 18.26.4 para 1-3: NFSv4 RENAME
                 * wants a status unique to the object type.
                 */
                if (type != S_IFDIR)
                        err = nfserr_file_open;
                else
                        err = nfserr_acces;
        } else {
                err = nfserrno(host_err);
        }

        if (!close_cached) {
                fh_fill_post_attrs(ffhp);
                fh_fill_post_attrs(tfhp);
        }
out_unlock:
        end_renaming(&rd);
out_want_write:
        fh_drop_write(ffhp);

        /*
         * If the target dentry has cached open files, then we need to
         * try to close them prior to doing the rename.  Final fput
         * shouldn't be done with locks held however, so we delay it
         * until this point and then reattempt the whole shebang.
         */
        if (close_cached) {
                nfsd_close_cached_files(close_cached);
                dput(close_cached);
                goto retry;
        }
out:
        return err;
}

/**
 * nfsd_unlink - remove a directory entry
 * @rqstp: RPC transaction context
 * @fhp: the file handle of the parent directory to be modified
 * @type: enforced file type of the object to be removed
 * @fname: the name of directory entry to be removed
 * @flen: length of @fname in octets
 *
 * After this call fhp needs an fh_put.
 *
 * Returns a generic NFS status code in network byte-order.
 */
__be32
nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
                                char *fname, int flen)
{
        struct dentry   *dentry, *rdentry;
        struct inode    *dirp;
        struct inode    *rinode = NULL;
        __be32          err;
        int             host_err;

        trace_nfsd_vfs_unlink(rqstp, fhp, fname, flen);

        err = nfserr_acces;
        if (!flen || isdotent(fname, flen))
                goto out;
        err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_REMOVE);
        if (err)
                goto out;

        host_err = fh_want_write(fhp);
        if (host_err)
                goto out_nfserr;

        dentry = fhp->fh_dentry;
        dirp = d_inode(dentry);

        rdentry = start_removing(&nop_mnt_idmap, dentry, &QSTR_LEN(fname, flen));

        host_err = PTR_ERR(rdentry);
        if (IS_ERR(rdentry))
                goto out_drop_write;

        err = fh_fill_pre_attrs(fhp);
        if (err != nfs_ok)
                goto out_unlock;

        rinode = d_inode(rdentry);
        /* Prevent truncation until after locks dropped */
        ihold(rinode);

        if (!type)
                type = d_inode(rdentry)->i_mode & S_IFMT;

        if (type != S_IFDIR) {
                int retries;

                if (rdentry->d_sb->s_export_op->flags & EXPORT_OP_CLOSE_BEFORE_UNLINK)
                        nfsd_close_cached_files(rdentry);

                for (retries = 1;;) {
                        host_err = vfs_unlink(&nop_mnt_idmap, dirp, rdentry, NULL);
                        if (host_err != -EAGAIN || !retries--)
                                break;
                        if (!nfsd_wait_for_delegreturn(rqstp, rinode))
                                break;
                }
        } else {
                host_err = vfs_rmdir(&nop_mnt_idmap, dirp, rdentry, NULL);
        }
        fh_fill_post_attrs(fhp);

out_unlock:
        end_removing(rdentry);
        if (!err && !host_err)
                host_err = commit_metadata(fhp);
        iput(rinode);    /* truncate the inode here */

out_drop_write:
        fh_drop_write(fhp);
out_nfserr:
        if (host_err == -EBUSY) {
                /*
                 * See RFC 8881 Section 18.25.4 para 4: NFSv4 REMOVE
                 * wants a status unique to the object type.
                 */
                if (type != S_IFDIR)
                        err = nfserr_file_open;
                else
                        err = nfserr_acces;
        }
out:
        return err != nfs_ok ? err : nfserrno(host_err);
}

/*
 * We do this buffering because we must not call back into the file
 * system's ->lookup() method from the filldir callback. That may well
 * deadlock a number of file systems.
 *
 * This is based heavily on the implementation of same in XFS.
 */
struct buffered_dirent {
        u64             ino;
        loff_t          offset;
        int             namlen;
        unsigned int    d_type;
        char            name[];
};

struct readdir_data {
        struct dir_context ctx;
        char            *dirent;
        size_t          used;
        int             full;
};

static bool nfsd_buffered_filldir(struct dir_context *ctx, const char *name,
                                 int namlen, loff_t offset, u64 ino,
                                 unsigned int d_type)
{
        struct readdir_data *buf =
                container_of(ctx, struct readdir_data, ctx);
        struct buffered_dirent *de = (void *)(buf->dirent + buf->used);
        unsigned int reclen;

        reclen = ALIGN(sizeof(struct buffered_dirent) + namlen, sizeof(u64));
        if (buf->used + reclen > PAGE_SIZE) {
                buf->full = 1;
                return false;
        }

        de->namlen = namlen;
        de->offset = offset;
        de->ino = ino;
        de->d_type = d_type;
        memcpy(de->name, name, namlen);
        buf->used += reclen;

        return true;
}

static __be32 nfsd_buffered_readdir(struct file *file, struct svc_fh *fhp,
                                    nfsd_filldir_t func, struct readdir_cd *cdp,
                                    loff_t *offsetp)
{
        struct buffered_dirent *de;
        int host_err;
        int size;
        loff_t offset;
        struct readdir_data buf = {
                .ctx.actor = nfsd_buffered_filldir,
                .dirent = (void *)__get_free_page(GFP_KERNEL)
        };

        if (!buf.dirent)
                return nfserrno(-ENOMEM);

        offset = *offsetp;

        while (1) {
                unsigned int reclen;

                cdp->err = nfserr_eof; /* will be cleared on successful read */
                buf.used = 0;
                buf.full = 0;

                host_err = iterate_dir(file, &buf.ctx);
                if (buf.full)
                        host_err = 0;

                if (host_err < 0)
                        break;

                size = buf.used;

                if (!size)
                        break;

                de = (struct buffered_dirent *)buf.dirent;
                while (size > 0) {
                        offset = de->offset;

                        if (func(cdp, de->name, de->namlen, de->offset,
                                 de->ino, de->d_type))
                                break;

                        if (cdp->err != nfs_ok)
                                break;

                        trace_nfsd_dirent(fhp, de->ino, de->name, de->namlen);

                        reclen = ALIGN(sizeof(*de) + de->namlen,
                                       sizeof(u64));
                        size -= reclen;
                        de = (struct buffered_dirent *)((char *)de + reclen);
                }
                if (size > 0) /* We bailed out early */
                        break;

                offset = vfs_llseek(file, 0, SEEK_CUR);
        }

        free_page((unsigned long)(buf.dirent));

        if (host_err)
                return nfserrno(host_err);

        *offsetp = offset;
        return cdp->err;
}

/**
 * nfsd_readdir - Read entries from a directory
 * @rqstp: RPC transaction context
 * @fhp: NFS file handle of directory to be read
 * @offsetp: OUT: seek offset of final entry that was read
 * @cdp: OUT: an eof error value
 * @func: entry filler actor
 *
 * This implementation ignores the NFSv3/4 verifier cookie.
 *
 * NB: normal system calls hold file->f_pos_lock when calling
 * ->iterate_shared and ->llseek, but nfsd_readdir() does not.
 * Because the struct file acquired here is not visible to other
 * threads, it's internal state does not need mutex protection.
 *
 * Returns nfs_ok on success, otherwise an nfsstat code is
 * returned.
 */
__be32
nfsd_readdir(struct svc_rqst *rqstp, struct svc_fh *fhp, loff_t *offsetp, 
             struct readdir_cd *cdp, nfsd_filldir_t func)
{
        __be32          err;
        struct file     *file;
        loff_t          offset = *offsetp;
        int             may_flags = NFSD_MAY_READ;

        err = nfsd_open(rqstp, fhp, S_IFDIR, may_flags, &file);
        if (err)
                goto out;

        if (fhp->fh_64bit_cookies)
                file->f_mode |= FMODE_64BITHASH;
        else
                file->f_mode |= FMODE_32BITHASH;

        offset = vfs_llseek(file, offset, SEEK_SET);
        if (offset < 0) {
                err = nfserrno((int)offset);
                goto out_close;
        }

        err = nfsd_buffered_readdir(file, fhp, func, cdp, offsetp);

        if (err == nfserr_eof || err == nfserr_toosmall)
                err = nfs_ok; /* can still be found in ->err */
out_close:
        nfsd_filp_close(file);
out:
        return err;
}

/**
 * nfsd_filp_close: close a file synchronously
 * @fp: the file to close
 *
 * nfsd_filp_close() is similar in behaviour to filp_close().
 * The difference is that if this is the final close on the
 * file, the that finalisation happens immediately, rather then
 * being handed over to a work_queue, as it the case for
 * filp_close().
 * When a user-space process closes a file (even when using
 * filp_close() the finalisation happens before returning to
 * userspace, so it is effectively synchronous.  When a kernel thread
 * uses file_close(), on the other hand, the handling is completely
 * asynchronous.  This means that any cost imposed by that finalisation
 * is not imposed on the nfsd thread, and nfsd could potentually
 * close files more quickly than the work queue finalises the close,
 * which would lead to unbounded growth in the queue.
 *
 * In some contexts is it not safe to synchronously wait for
 * close finalisation (see comment for __fput_sync()), but nfsd
 * does not match those contexts.  In partcilarly it does not, at the
 * time that this function is called, hold and locks and no finalisation
 * of any file, socket, or device driver would have any cause to wait
 * for nfsd to make progress.
 */
void nfsd_filp_close(struct file *fp)
{
        get_file(fp);
        filp_close(fp, NULL);
        __fput_sync(fp);
}

/*
 * Get file system stats
 * N.B. After this call fhp needs an fh_put
 */
__be32
nfsd_statfs(struct svc_rqst *rqstp, struct svc_fh *fhp, struct kstatfs *stat, int access)
{
        __be32 err;

        trace_nfsd_vfs_statfs(rqstp, fhp);

        err = fh_verify(rqstp, fhp, 0, NFSD_MAY_NOP | access);
        if (!err) {
                struct path path = {
                        .mnt    = fhp->fh_export->ex_path.mnt,
                        .dentry = fhp->fh_dentry,
                };
                if (vfs_statfs(&path, stat))
                        err = nfserr_io;
        }
        return err;
}

static int exp_rdonly(struct svc_cred *cred, struct svc_export *exp)
{
        return nfsexp_flags(cred, exp) & NFSEXP_READONLY;
}

#ifdef CONFIG_NFSD_V4
/*
 * Helper function to translate error numbers. In the case of xattr operations,
 * some error codes need to be translated outside of the standard translations.
 *
 * ENODATA needs to be translated to nfserr_noxattr.
 * E2BIG to nfserr_xattr2big.
 *
 * Additionally, vfs_listxattr can return -ERANGE. This means that the
 * file has too many extended attributes to retrieve inside an
 * XATTR_LIST_MAX sized buffer. This is a bug in the xattr implementation:
 * filesystems will allow the adding of extended attributes until they hit
 * their own internal limit. This limit may be larger than XATTR_LIST_MAX.
 * So, at that point, the attributes are present and valid, but can't
 * be retrieved using listxattr, since the upper level xattr code enforces
 * the XATTR_LIST_MAX limit.
 *
 * This bug means that we need to deal with listxattr returning -ERANGE. The
 * best mapping is to return TOOSMALL.
 */
static __be32
nfsd_xattr_errno(int err)
{
        switch (err) {
        case -ENODATA:
                return nfserr_noxattr;
        case -E2BIG:
                return nfserr_xattr2big;
        case -ERANGE:
                return nfserr_toosmall;
        }
        return nfserrno(err);
}

/*
 * Retrieve the specified user extended attribute. To avoid always
 * having to allocate the maximum size (since we are not getting
 * a maximum size from the RPC), do a probe + alloc. Hold a reader
 * lock on i_rwsem to prevent the extended attribute from changing
 * size while we're doing this.
 */
__be32
nfsd_getxattr(struct svc_rqst *rqstp, struct svc_fh *fhp, char *name,
              void **bufp, int *lenp)
{
        ssize_t len;
        __be32 err;
        char *buf;
        struct inode *inode;
        struct dentry *dentry;

        err = fh_verify(rqstp, fhp, 0, NFSD_MAY_READ);
        if (err)
                return err;

        err = nfs_ok;
        dentry = fhp->fh_dentry;
        inode = d_inode(dentry);

        inode_lock_shared(inode);

        len = vfs_getxattr(&nop_mnt_idmap, dentry, name, NULL, 0);

        /*
         * Zero-length attribute, just return.
         */
        if (len == 0) {
                *bufp = NULL;
                *lenp = 0;
                goto out;
        }

        if (len < 0) {
                err = nfsd_xattr_errno(len);
                goto out;
        }

        if (len > *lenp) {
                err = nfserr_toosmall;
                goto out;
        }

        buf = kvmalloc(len, GFP_KERNEL);
        if (buf == NULL) {
                err = nfserr_jukebox;
                goto out;
        }

        len = vfs_getxattr(&nop_mnt_idmap, dentry, name, buf, len);
        if (len <= 0) {
                kvfree(buf);
                buf = NULL;
                err = nfsd_xattr_errno(len);
        }

        *lenp = len;
        *bufp = buf;

out:
        inode_unlock_shared(inode);

        return err;
}

/*
 * Retrieve the xattr names. Since we can't know how many are
 * user extended attributes, we must get all attributes here,
 * and have the XDR encode filter out the "user." ones.
 *
 * While this could always just allocate an XATTR_LIST_MAX
 * buffer, that's a waste, so do a probe + allocate. To
 * avoid any changes between the probe and allocate, wrap
 * this in inode_lock.
 */
__be32
nfsd_listxattr(struct svc_rqst *rqstp, struct svc_fh *fhp, char **bufp,
               int *lenp)
{
        ssize_t len;
        __be32 err;
        char *buf;
        struct inode *inode;
        struct dentry *dentry;

        err = fh_verify(rqstp, fhp, 0, NFSD_MAY_READ);
        if (err)
                return err;

        dentry = fhp->fh_dentry;
        inode = d_inode(dentry);
        *lenp = 0;

        inode_lock_shared(inode);

        len = vfs_listxattr(dentry, NULL, 0);
        if (len <= 0) {
                err = nfsd_xattr_errno(len);
                goto out;
        }

        if (len > XATTR_LIST_MAX) {
                err = nfserr_xattr2big;
                goto out;
        }

        buf = kvmalloc(len, GFP_KERNEL);
        if (buf == NULL) {
                err = nfserr_jukebox;
                goto out;
        }

        len = vfs_listxattr(dentry, buf, len);
        if (len <= 0) {
                kvfree(buf);
                err = nfsd_xattr_errno(len);
                goto out;
        }

        *lenp = len;
        *bufp = buf;

        err = nfs_ok;
out:
        inode_unlock_shared(inode);

        return err;
}

/**
 * nfsd_removexattr - Remove an extended attribute
 * @rqstp: RPC transaction being executed
 * @fhp: NFS filehandle of object with xattr to remove
 * @name: name of xattr to remove (NUL-terminate)
 *
 * Pass in a NULL pointer for delegated_inode, and let the client deal
 * with NFS4ERR_DELAY (same as with e.g. setattr and remove).
 *
 * Returns nfs_ok on success, or an nfsstat in network byte order.
 */
__be32
nfsd_removexattr(struct svc_rqst *rqstp, struct svc_fh *fhp, char *name)
{
        __be32 err;
        int ret;

        err = fh_verify(rqstp, fhp, 0, NFSD_MAY_WRITE);
        if (err)
                return err;

        ret = fh_want_write(fhp);
        if (ret)
                return nfserrno(ret);

        inode_lock(fhp->fh_dentry->d_inode);
        err = fh_fill_pre_attrs(fhp);
        if (err != nfs_ok)
                goto out_unlock;
        ret = __vfs_removexattr_locked(&nop_mnt_idmap, fhp->fh_dentry,
                                       name, NULL);
        err = nfsd_xattr_errno(ret);
        fh_fill_post_attrs(fhp);
out_unlock:
        inode_unlock(fhp->fh_dentry->d_inode);
        fh_drop_write(fhp);

        return err;
}

__be32
nfsd_setxattr(struct svc_rqst *rqstp, struct svc_fh *fhp, char *name,
              void *buf, u32 len, u32 flags)
{
        __be32 err;
        int ret;

        err = fh_verify(rqstp, fhp, 0, NFSD_MAY_WRITE);
        if (err)
                return err;

        ret = fh_want_write(fhp);
        if (ret)
                return nfserrno(ret);
        inode_lock(fhp->fh_dentry->d_inode);
        err = fh_fill_pre_attrs(fhp);
        if (err != nfs_ok)
                goto out_unlock;
        ret = __vfs_setxattr_locked(&nop_mnt_idmap, fhp->fh_dentry,
                                    name, buf, len, flags, NULL);
        fh_fill_post_attrs(fhp);
        err = nfsd_xattr_errno(ret);
out_unlock:
        inode_unlock(fhp->fh_dentry->d_inode);
        fh_drop_write(fhp);
        return err;
}
#endif

/*
 * Check for a user's access permissions to this inode.
 */
__be32
nfsd_permission(struct svc_cred *cred, struct svc_export *exp,
                struct dentry *dentry, int acc)
{
        struct inode    *inode = d_inode(dentry);
        int             err;

        if ((acc & NFSD_MAY_MASK) == NFSD_MAY_NOP)
                return 0;
#if 0
        dprintk("nfsd: permission 0x%x%s%s%s%s%s%s%s mode 0%o%s%s%s\n",
                acc,
                (acc & NFSD_MAY_READ)?  " read"  : "",
                (acc & NFSD_MAY_WRITE)? " write" : "",
                (acc & NFSD_MAY_EXEC)?  " exec"  : "",
                (acc & NFSD_MAY_SATTR)? " sattr" : "",
                (acc & NFSD_MAY_TRUNC)? " trunc" : "",
                (acc & NFSD_MAY_NLM)?   " nlm"  : "",
                (acc & NFSD_MAY_OWNER_OVERRIDE)? " owneroverride" : "",
                inode->i_mode,
                IS_IMMUTABLE(inode)?    " immut" : "",
                IS_APPEND(inode)?       " append" : "",
                __mnt_is_readonly(exp->ex_path.mnt)?    " ro" : "");
        dprintk("      owner %d/%d user %d/%d\n",
                inode->i_uid, inode->i_gid, current_fsuid(), current_fsgid());
#endif

        /* Normally we reject any write/sattr etc access on a read-only file
         * system.  But if it is IRIX doing check on write-access for a 
         * device special file, we ignore rofs.
         */
        if (!(acc & NFSD_MAY_LOCAL_ACCESS))
                if (acc & (NFSD_MAY_WRITE | NFSD_MAY_SATTR | NFSD_MAY_TRUNC)) {
                        if (exp_rdonly(cred, exp) ||
                            __mnt_is_readonly(exp->ex_path.mnt))
                                return nfserr_rofs;
                        if (/* (acc & NFSD_MAY_WRITE) && */ IS_IMMUTABLE(inode))
                                return nfserr_perm;
                }
        if ((acc & NFSD_MAY_TRUNC) && IS_APPEND(inode))
                return nfserr_perm;

        /*
         * The file owner always gets access permission for accesses that
         * would normally be checked at open time. This is to make
         * file access work even when the client has done a fchmod(fd, 0).
         *
         * However, `cp foo bar' should fail nevertheless when bar is
         * readonly. A sensible way to do this might be to reject all
         * attempts to truncate a read-only file, because a creat() call
         * always implies file truncation.
         * ... but this isn't really fair.  A process may reasonably call
         * ftruncate on an open file descriptor on a file with perm 000.
         * We must trust the client to do permission checking - using "ACCESS"
         * with NFSv3.
         */
        if ((acc & NFSD_MAY_OWNER_OVERRIDE) &&
            uid_eq(inode->i_uid, current_fsuid()))
                return 0;

        /* This assumes  NFSD_MAY_{READ,WRITE,EXEC} == MAY_{READ,WRITE,EXEC} */
        err = inode_permission(&nop_mnt_idmap, inode,
                               acc & (MAY_READ | MAY_WRITE | MAY_EXEC));

        /* Allow read access to binaries even when mode 111 */
        if (err == -EACCES && S_ISREG(inode->i_mode) &&
             (((acc & NFSD_MAY_MASK) == NFSD_MAY_READ) &&
              (acc & (NFSD_MAY_OWNER_OVERRIDE | NFSD_MAY_READ_IF_EXEC))))
                err = inode_permission(&nop_mnt_idmap, inode, MAY_EXEC);

        return err? nfserrno(err) : 0;
}