// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2011 Novell Inc.
 * Copyright (C) 2016 Red Hat, Inc.
 */

#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/xattr.h>
#include <linux/exportfs.h>
#include <linux/file.h>
#include <linux/fileattr.h>
#include <linux/uuid.h>
#include <linux/namei.h>
#include <linux/ratelimit.h>
#include <linux/overflow.h>
#include "overlayfs.h"

/* Get write access to upper mnt - may fail if upper sb was remounted ro */
int ovl_get_write_access(struct dentry *dentry)
{
        struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
        return mnt_get_write_access(ovl_upper_mnt(ofs));
}

/* Get write access to upper sb - may block if upper sb is frozen */
void ovl_start_write(struct dentry *dentry)
{
        struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
        sb_start_write(ovl_upper_mnt(ofs)->mnt_sb);
}

int ovl_want_write(struct dentry *dentry)
{
        struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
        return mnt_want_write(ovl_upper_mnt(ofs));
}

void ovl_put_write_access(struct dentry *dentry)
{
        struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
        mnt_put_write_access(ovl_upper_mnt(ofs));
}

void ovl_end_write(struct dentry *dentry)
{
        struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
        sb_end_write(ovl_upper_mnt(ofs)->mnt_sb);
}

void ovl_drop_write(struct dentry *dentry)
{
        struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
        mnt_drop_write(ovl_upper_mnt(ofs));
}

struct dentry *ovl_workdir(struct dentry *dentry)
{
        struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
        return ofs->workdir;
}

const struct cred *ovl_override_creds(struct super_block *sb)
{
        struct ovl_fs *ofs = OVL_FS(sb);

        return override_creds(ofs->creator_cred);
}

/*
 * Check if underlying fs supports file handles and try to determine encoding
 * type, in order to deduce maximum inode number used by fs.
 *
 * Return 0 if file handles are not supported.
 * Return 1 (FILEID_INO32_GEN) if fs uses the default 32bit inode encoding.
 * Return -1 if fs uses a non default encoding with unknown inode size.
 */
int ovl_can_decode_fh(struct super_block *sb)
{
        if (!capable(CAP_DAC_READ_SEARCH))
                return 0;

        if (!exportfs_can_decode_fh(sb->s_export_op))
                return 0;

        if (sb->s_export_op->encode_fh == generic_encode_ino32_fh)
                return FILEID_INO32_GEN;

        return -1;
}

struct dentry *ovl_indexdir(struct super_block *sb)
{
        struct ovl_fs *ofs = OVL_FS(sb);

        return ofs->config.index ? ofs->workdir : NULL;
}

/* Index all files on copy up. For now only enabled for NFS export */
bool ovl_index_all(struct super_block *sb)
{
        struct ovl_fs *ofs = OVL_FS(sb);

        return ofs->config.nfs_export && ofs->config.index;
}

/* Verify lower origin on lookup. For now only enabled for NFS export */
bool ovl_verify_lower(struct super_block *sb)
{
        struct ovl_fs *ofs = OVL_FS(sb);

        return ofs->config.nfs_export && ofs->config.index;
}

struct ovl_path *ovl_stack_alloc(unsigned int n)
{
        return kzalloc_objs(struct ovl_path, n);
}

void ovl_stack_cpy(struct ovl_path *dst, struct ovl_path *src, unsigned int n)
{
        unsigned int i;

        memcpy(dst, src, sizeof(struct ovl_path) * n);
        for (i = 0; i < n; i++)
                dget(src[i].dentry);
}

void ovl_stack_put(struct ovl_path *stack, unsigned int n)
{
        unsigned int i;

        for (i = 0; stack && i < n; i++)
                dput(stack[i].dentry);
}

void ovl_stack_free(struct ovl_path *stack, unsigned int n)
{
        ovl_stack_put(stack, n);
        kfree(stack);
}

struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
{
        struct ovl_entry *oe;

        oe = kzalloc_flex(*oe, __lowerstack, numlower);
        if (oe)
                oe->__numlower = numlower;

        return oe;
}

void ovl_free_entry(struct ovl_entry *oe)
{
        ovl_stack_put(ovl_lowerstack(oe), ovl_numlower(oe));
        kfree(oe);
}

#define OVL_D_REVALIDATE (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE)

bool ovl_dentry_remote(struct dentry *dentry)
{
        return dentry->d_flags & OVL_D_REVALIDATE;
}

void ovl_dentry_update_reval(struct dentry *dentry, struct dentry *realdentry)
{
        if (!ovl_dentry_remote(realdentry))
                return;

        spin_lock(&dentry->d_lock);
        dentry->d_flags |= realdentry->d_flags & OVL_D_REVALIDATE;
        spin_unlock(&dentry->d_lock);
}

void ovl_dentry_init_reval(struct dentry *dentry, struct dentry *upperdentry,
                           struct ovl_entry *oe)
{
        return ovl_dentry_init_flags(dentry, upperdentry, oe, OVL_D_REVALIDATE);
}

void ovl_dentry_init_flags(struct dentry *dentry, struct dentry *upperdentry,
                           struct ovl_entry *oe, unsigned int mask)
{
        struct ovl_path *lowerstack = ovl_lowerstack(oe);
        unsigned int i, flags = 0;

        if (upperdentry)
                flags |= upperdentry->d_flags;
        for (i = 0; i < ovl_numlower(oe) && lowerstack[i].dentry; i++)
                flags |= lowerstack[i].dentry->d_flags;

        spin_lock(&dentry->d_lock);
        dentry->d_flags &= ~mask;
        dentry->d_flags |= flags & mask;
        spin_unlock(&dentry->d_lock);
}

bool ovl_dentry_weird(struct dentry *dentry)
{
        if (!d_can_lookup(dentry) && !d_is_file(dentry) && !d_is_symlink(dentry))
                return true;

        if (dentry->d_flags & (DCACHE_NEED_AUTOMOUNT | DCACHE_MANAGE_TRANSIT))
                return true;

        /*
         * Exceptionally for layers with casefold, we accept that they have
         * their own hash and compare operations
         */
        if (sb_has_encoding(dentry->d_sb))
                return false;

        return dentry->d_flags & (DCACHE_OP_HASH | DCACHE_OP_COMPARE);
}

enum ovl_path_type ovl_path_type(struct dentry *dentry)
{
        struct ovl_entry *oe = OVL_E(dentry);
        enum ovl_path_type type = 0;

        if (ovl_dentry_upper(dentry)) {
                type = __OVL_PATH_UPPER;

                /*
                 * Non-dir dentry can hold lower dentry of its copy up origin.
                 */
                if (ovl_numlower(oe)) {
                        if (ovl_test_flag(OVL_CONST_INO, d_inode(dentry)))
                                type |= __OVL_PATH_ORIGIN;
                        if (d_is_dir(dentry) ||
                            !ovl_has_upperdata(d_inode(dentry)))
                                type |= __OVL_PATH_MERGE;
                }
        } else {
                if (ovl_numlower(oe) > 1)
                        type |= __OVL_PATH_MERGE;
        }
        return type;
}

void ovl_path_upper(struct dentry *dentry, struct path *path)
{
        struct ovl_fs *ofs = OVL_FS(dentry->d_sb);

        path->mnt = ovl_upper_mnt(ofs);
        path->dentry = ovl_dentry_upper(dentry);
}

void ovl_path_lower(struct dentry *dentry, struct path *path)
{
        struct ovl_entry *oe = OVL_E(dentry);
        struct ovl_path *lowerpath = ovl_lowerstack(oe);

        if (ovl_numlower(oe)) {
                path->mnt = lowerpath->layer->mnt;
                path->dentry = lowerpath->dentry;
        } else {
                *path = (struct path) { };
        }
}

void ovl_path_lowerdata(struct dentry *dentry, struct path *path)
{
        struct ovl_entry *oe = OVL_E(dentry);
        struct ovl_path *lowerdata = ovl_lowerdata(oe);
        struct dentry *lowerdata_dentry = ovl_lowerdata_dentry(oe);

        if (lowerdata_dentry) {
                path->dentry = lowerdata_dentry;
                /*
                 * Pairs with smp_wmb() in ovl_dentry_set_lowerdata().
                 * Make sure that if lowerdata->dentry is visible, then
                 * datapath->layer is visible as well.
                 */
                smp_rmb();
                path->mnt = READ_ONCE(lowerdata->layer)->mnt;
        } else {
                *path = (struct path) { };
        }
}

enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
{
        enum ovl_path_type type = ovl_path_type(dentry);

        if (!OVL_TYPE_UPPER(type))
                ovl_path_lower(dentry, path);
        else
                ovl_path_upper(dentry, path);

        return type;
}

enum ovl_path_type ovl_path_realdata(struct dentry *dentry, struct path *path)
{
        enum ovl_path_type type = ovl_path_type(dentry);

        WARN_ON_ONCE(d_is_dir(dentry));

        if (!OVL_TYPE_UPPER(type) || OVL_TYPE_MERGE(type))
                ovl_path_lowerdata(dentry, path);
        else
                ovl_path_upper(dentry, path);

        return type;
}

struct dentry *ovl_dentry_upper(struct dentry *dentry)
{
        struct inode *inode = d_inode(dentry);

        return inode ? ovl_upperdentry_dereference(OVL_I(inode)) : NULL;
}

struct dentry *ovl_dentry_lower(struct dentry *dentry)
{
        struct ovl_entry *oe = OVL_E(dentry);

        return ovl_numlower(oe) ? ovl_lowerstack(oe)->dentry : NULL;
}

const struct ovl_layer *ovl_layer_lower(struct dentry *dentry)
{
        struct ovl_entry *oe = OVL_E(dentry);

        return ovl_numlower(oe) ? ovl_lowerstack(oe)->layer : NULL;
}

/*
 * ovl_dentry_lower() could return either a data dentry or metacopy dentry
 * depending on what is stored in lowerstack[0]. At times we need to find
 * lower dentry which has data (and not metacopy dentry). This helper
 * returns the lower data dentry.
 */
struct dentry *ovl_dentry_lowerdata(struct dentry *dentry)
{
        return ovl_lowerdata_dentry(OVL_E(dentry));
}

int ovl_dentry_set_lowerdata(struct dentry *dentry, struct ovl_path *datapath)
{
        struct ovl_entry *oe = OVL_E(dentry);
        struct ovl_path *lowerdata = ovl_lowerdata(oe);
        struct dentry *datadentry = datapath->dentry;

        if (WARN_ON_ONCE(ovl_numlower(oe) <= 1))
                return -EIO;

        WRITE_ONCE(lowerdata->layer, datapath->layer);
        /*
         * Pairs with smp_rmb() in ovl_path_lowerdata().
         * Make sure that if lowerdata->dentry is visible, then
         * lowerdata->layer is visible as well.
         */
        smp_wmb();
        WRITE_ONCE(lowerdata->dentry, dget(datadentry));

        ovl_dentry_update_reval(dentry, datadentry);

        return 0;
}

struct dentry *ovl_dentry_real(struct dentry *dentry)
{
        return ovl_dentry_upper(dentry) ?: ovl_dentry_lower(dentry);
}

struct dentry *ovl_i_dentry_upper(struct inode *inode)
{
        return ovl_upperdentry_dereference(OVL_I(inode));
}

struct inode *ovl_i_path_real(struct inode *inode, struct path *path)
{
        struct ovl_path *lowerpath = ovl_lowerpath(OVL_I_E(inode));

        path->dentry = ovl_i_dentry_upper(inode);
        if (!path->dentry) {
                path->dentry = lowerpath->dentry;
                path->mnt = lowerpath->layer->mnt;
        } else {
                path->mnt = ovl_upper_mnt(OVL_FS(inode->i_sb));
        }

        return path->dentry ? d_inode_rcu(path->dentry) : NULL;
}

struct inode *ovl_inode_upper(struct inode *inode)
{
        struct dentry *upperdentry = ovl_i_dentry_upper(inode);

        return upperdentry ? d_inode(upperdentry) : NULL;
}

struct inode *ovl_inode_lower(struct inode *inode)
{
        struct ovl_path *lowerpath = ovl_lowerpath(OVL_I_E(inode));

        return lowerpath ? d_inode(lowerpath->dentry) : NULL;
}

struct inode *ovl_inode_real(struct inode *inode)
{
        return ovl_inode_upper(inode) ?: ovl_inode_lower(inode);
}

/* Return inode which contains lower data. Do not return metacopy */
struct inode *ovl_inode_lowerdata(struct inode *inode)
{
        struct dentry *lowerdata = ovl_lowerdata_dentry(OVL_I_E(inode));

        if (WARN_ON(!S_ISREG(inode->i_mode)))
                return NULL;

        return lowerdata ? d_inode(lowerdata) : NULL;
}

/* Return real inode which contains data. Does not return metacopy inode */
struct inode *ovl_inode_realdata(struct inode *inode)
{
        struct inode *upperinode;

        upperinode = ovl_inode_upper(inode);
        if (upperinode && ovl_has_upperdata(inode))
                return upperinode;

        return ovl_inode_lowerdata(inode);
}

const char *ovl_lowerdata_redirect(struct inode *inode)
{
        return inode && S_ISREG(inode->i_mode) ?
                OVL_I(inode)->lowerdata_redirect : NULL;
}

struct ovl_dir_cache *ovl_dir_cache(struct inode *inode)
{
        return inode && S_ISDIR(inode->i_mode) ? OVL_I(inode)->cache : NULL;
}

void ovl_set_dir_cache(struct inode *inode, struct ovl_dir_cache *cache)
{
        OVL_I(inode)->cache = cache;
}

void ovl_dentry_set_flag(unsigned long flag, struct dentry *dentry)
{
        set_bit(flag, OVL_E_FLAGS(dentry));
}

void ovl_dentry_clear_flag(unsigned long flag, struct dentry *dentry)
{
        clear_bit(flag, OVL_E_FLAGS(dentry));
}

bool ovl_dentry_test_flag(unsigned long flag, struct dentry *dentry)
{
        return test_bit(flag, OVL_E_FLAGS(dentry));
}

bool ovl_dentry_is_opaque(struct dentry *dentry)
{
        return ovl_dentry_test_flag(OVL_E_OPAQUE, dentry);
}

bool ovl_dentry_is_whiteout(struct dentry *dentry)
{
        return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
}

void ovl_dentry_set_opaque(struct dentry *dentry)
{
        ovl_dentry_set_flag(OVL_E_OPAQUE, dentry);
}

bool ovl_dentry_has_xwhiteouts(struct dentry *dentry)
{
        return ovl_dentry_test_flag(OVL_E_XWHITEOUTS, dentry);
}

void ovl_dentry_set_xwhiteouts(struct dentry *dentry)
{
        ovl_dentry_set_flag(OVL_E_XWHITEOUTS, dentry);
}

/*
 * ovl_layer_set_xwhiteouts() is called before adding the overlay dir
 * dentry to dcache, while readdir of that same directory happens after
 * the overlay dir dentry is in dcache, so if some cpu observes that
 * ovl_dentry_is_xwhiteouts(), it will also observe layer->has_xwhiteouts
 * for the layers where xwhiteouts marker was found in that merge dir.
 */
void ovl_layer_set_xwhiteouts(struct ovl_fs *ofs,
                              const struct ovl_layer *layer)
{
        if (layer->has_xwhiteouts)
                return;

        /* Write once to read-mostly layer properties */
        ofs->layers[layer->idx].has_xwhiteouts = true;
}

/*
 * For hard links and decoded file handles, it's possible for ovl_dentry_upper()
 * to return positive, while there's no actual upper alias for the inode.
 * Copy up code needs to know about the existence of the upper alias, so it
 * can't use ovl_dentry_upper().
 */
bool ovl_dentry_has_upper_alias(struct dentry *dentry)
{
        return ovl_dentry_test_flag(OVL_E_UPPER_ALIAS, dentry);
}

void ovl_dentry_set_upper_alias(struct dentry *dentry)
{
        ovl_dentry_set_flag(OVL_E_UPPER_ALIAS, dentry);
}

static bool ovl_should_check_upperdata(struct inode *inode)
{
        if (!S_ISREG(inode->i_mode))
                return false;

        if (!ovl_inode_lower(inode))
                return false;

        return true;
}

bool ovl_has_upperdata(struct inode *inode)
{
        if (!ovl_should_check_upperdata(inode))
                return true;

        if (!ovl_test_flag(OVL_UPPERDATA, inode))
                return false;
        /*
         * Pairs with smp_wmb() in ovl_set_upperdata(). Main user of
         * ovl_has_upperdata() is ovl_copy_up_meta_inode_data(). Make sure
         * if setting of OVL_UPPERDATA is visible, then effects of writes
         * before that are visible too.
         */
        smp_rmb();
        return true;
}

void ovl_set_upperdata(struct inode *inode)
{
        /*
         * Pairs with smp_rmb() in ovl_has_upperdata(). Make sure
         * if OVL_UPPERDATA flag is visible, then effects of write operations
         * before it are visible as well.
         */
        smp_wmb();
        ovl_set_flag(OVL_UPPERDATA, inode);
}

/* Caller should hold ovl_inode->lock */
bool ovl_dentry_needs_data_copy_up_locked(struct dentry *dentry, int flags)
{
        if (!ovl_open_flags_need_copy_up(flags))
                return false;

        return !ovl_test_flag(OVL_UPPERDATA, d_inode(dentry));
}

bool ovl_dentry_needs_data_copy_up(struct dentry *dentry, int flags)
{
        if (!ovl_open_flags_need_copy_up(flags))
                return false;

        return !ovl_has_upperdata(d_inode(dentry));
}

const char *ovl_dentry_get_redirect(struct dentry *dentry)
{
        return OVL_I(d_inode(dentry))->redirect;
}

void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
{
        struct ovl_inode *oi = OVL_I(d_inode(dentry));

        kfree(oi->redirect);
        oi->redirect = redirect;
}

void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
{
        struct inode *upperinode = d_inode(upperdentry);

        WARN_ON(OVL_I(inode)->__upperdentry);

        /*
         * Make sure upperdentry is consistent before making it visible
         */
        smp_wmb();
        OVL_I(inode)->__upperdentry = upperdentry;
        if (inode_unhashed(inode)) {
                inode->i_private = upperinode;
                __insert_inode_hash(inode, (unsigned long) upperinode);
        }
}

static void ovl_dir_version_inc(struct dentry *dentry, bool impurity)
{
        struct inode *inode = d_inode(dentry);

        WARN_ON(!inode_is_locked(inode));
        WARN_ON(!d_is_dir(dentry));
        /*
         * Version is used by readdir code to keep cache consistent.
         * For merge dirs (or dirs with origin) all changes need to be noted.
         * For non-merge dirs, cache contains only impure entries (i.e. ones
         * which have been copied up and have origins), so only need to note
         * changes to impure entries.
         */
        if (!ovl_dir_is_real(inode) || impurity)
                OVL_I(inode)->version++;
}

void ovl_dir_modified(struct dentry *dentry, bool impurity)
{
        /* Copy mtime/ctime */
        ovl_copyattr(d_inode(dentry));

        ovl_dir_version_inc(dentry, impurity);
}

u64 ovl_inode_version_get(struct inode *inode)
{
        WARN_ON(!inode_is_locked(inode));
        return OVL_I(inode)->version;
}

bool ovl_is_whiteout(struct dentry *dentry)
{
        struct inode *inode = dentry->d_inode;

        return inode && IS_WHITEOUT(inode);
}

/*
 * Use this over ovl_is_whiteout for upper and lower files, as it also
 * handles overlay.whiteout xattr whiteout files.
 */
bool ovl_path_is_whiteout(struct ovl_fs *ofs, const struct path *path)
{
        return ovl_is_whiteout(path->dentry) ||
                ovl_path_check_xwhiteout_xattr(ofs, path);
}

struct file *ovl_path_open(const struct path *path, int flags)
{
        struct inode *inode = d_inode(path->dentry);
        struct mnt_idmap *real_idmap = mnt_idmap(path->mnt);
        int err, acc_mode;

        if (flags & ~(O_ACCMODE | O_LARGEFILE))
                BUG();

        switch (flags & O_ACCMODE) {
        case O_RDONLY:
                acc_mode = MAY_READ;
                break;
        case O_WRONLY:
                acc_mode = MAY_WRITE;
                break;
        default:
                BUG();
        }

        err = inode_permission(real_idmap, inode, acc_mode | MAY_OPEN);
        if (err)
                return ERR_PTR(err);

        /* O_NOATIME is an optimization, don't fail if not permitted */
        if (inode_owner_or_capable(real_idmap, inode))
                flags |= O_NOATIME;

        return dentry_open(path, flags, current_cred());
}

/* Caller should hold ovl_inode->lock */
static bool ovl_already_copied_up_locked(struct dentry *dentry, int flags)
{
        bool disconnected = dentry->d_flags & DCACHE_DISCONNECTED;

        if (ovl_dentry_upper(dentry) &&
            (ovl_dentry_has_upper_alias(dentry) || disconnected) &&
            !ovl_dentry_needs_data_copy_up_locked(dentry, flags))
                return true;

        return false;
}

bool ovl_already_copied_up(struct dentry *dentry, int flags)
{
        bool disconnected = dentry->d_flags & DCACHE_DISCONNECTED;

        /*
         * Check if copy-up has happened as well as for upper alias (in
         * case of hard links) is there.
         *
         * Both checks are lockless:
         *  - false negatives: will recheck under oi->lock
         *  - false positives:
         *    + ovl_dentry_upper() uses memory barriers to ensure the
         *      upper dentry is up-to-date
         *    + ovl_dentry_has_upper_alias() relies on locking of
         *      upper parent i_rwsem to prevent reordering copy-up
         *      with rename.
         */
        if (ovl_dentry_upper(dentry) &&
            (ovl_dentry_has_upper_alias(dentry) || disconnected) &&
            !ovl_dentry_needs_data_copy_up(dentry, flags))
                return true;

        return false;
}

/*
 * The copy up "transaction" keeps an elevated mnt write count on upper mnt,
 * but leaves taking freeze protection on upper sb to lower level helpers.
 */
int ovl_copy_up_start(struct dentry *dentry, int flags)
{
        struct inode *inode = d_inode(dentry);
        int err;

        err = ovl_inode_lock_interruptible(inode);
        if (err)
                return err;

        if (ovl_already_copied_up_locked(dentry, flags))
                err = 1; /* Already copied up */
        else
                err = ovl_get_write_access(dentry);
        if (err)
                goto out_unlock;

        return 0;

out_unlock:
        ovl_inode_unlock(inode);
        return err;
}

void ovl_copy_up_end(struct dentry *dentry)
{
        ovl_put_write_access(dentry);
        ovl_inode_unlock(d_inode(dentry));
}

bool ovl_path_check_origin_xattr(struct ovl_fs *ofs, const struct path *path)
{
        int res;

        res = ovl_path_getxattr(ofs, path, OVL_XATTR_ORIGIN, NULL, 0);

        /* Zero size value means "copied up but origin unknown" */
        if (res >= 0)
                return true;

        return false;
}

bool ovl_path_check_xwhiteout_xattr(struct ovl_fs *ofs, const struct path *path)
{
        struct dentry *dentry = path->dentry;
        int res;

        /* xattr.whiteout must be a zero size regular file */
        if (!d_is_reg(dentry) || i_size_read(d_inode(dentry)) != 0)
                return false;

        res = ovl_path_getxattr(ofs, path, OVL_XATTR_XWHITEOUT, NULL, 0);
        return res >= 0;
}

/*
 * Load persistent uuid from xattr into s_uuid if found, or store a new
 * random generated value in s_uuid and in xattr.
 */
bool ovl_init_uuid_xattr(struct super_block *sb, struct ovl_fs *ofs,
                         const struct path *upperpath)
{
        bool set = false;
        uuid_t uuid;
        int res;

        /* Try to load existing persistent uuid */
        res = ovl_path_getxattr(ofs, upperpath, OVL_XATTR_UUID, uuid.b,
                                UUID_SIZE);
        if (res == UUID_SIZE)
                goto set_uuid;

        if (res != -ENODATA)
                goto fail;

        /*
         * With uuid=auto, if uuid xattr is found, it will be used.
         * If uuid xattrs is not found, generate a persistent uuid only on mount
         * of new overlays where upper root dir is not yet marked as impure.
         * An upper dir is marked as impure on copy up or lookup of its subdirs.
         */
        if (ofs->config.uuid == OVL_UUID_AUTO) {
                res = ovl_path_getxattr(ofs, upperpath, OVL_XATTR_IMPURE, NULL,
                                        0);
                if (res > 0) {
                        /* Any mount of old overlay - downgrade to uuid=null */
                        ofs->config.uuid = OVL_UUID_NULL;
                        return true;
                } else if (res == -ENODATA) {
                        /* First mount of new overlay - upgrade to uuid=on */
                        ofs->config.uuid = OVL_UUID_ON;
                } else if (res < 0) {
                        goto fail;
                }

        }

        /* Generate overlay instance uuid */
        uuid_gen(&uuid);

        /* Try to store persistent uuid */
        set = true;
        res = ovl_setxattr(ofs, upperpath->dentry, OVL_XATTR_UUID, uuid.b,
                           UUID_SIZE);
        if (res)
                goto fail;

set_uuid:
        super_set_uuid(sb, uuid.b, sizeof(uuid));
        return true;

fail:
        ofs->config.uuid = OVL_UUID_NULL;
        pr_warn("failed to %s uuid (%pd2, err=%i); falling back to uuid=null.\n",
                set ? "set" : "get", upperpath->dentry, res);
        return false;
}

char ovl_get_dir_xattr_val(struct ovl_fs *ofs, const struct path *path,
                           enum ovl_xattr ox)
{
        int res;
        char val;

        if (!d_is_dir(path->dentry))
                return 0;

        res = ovl_path_getxattr(ofs, path, ox, &val, 1);
        return res == 1 ? val : 0;
}

#define OVL_XATTR_OPAQUE_POSTFIX        "opaque"
#define OVL_XATTR_REDIRECT_POSTFIX      "redirect"
#define OVL_XATTR_ORIGIN_POSTFIX        "origin"
#define OVL_XATTR_IMPURE_POSTFIX        "impure"
#define OVL_XATTR_NLINK_POSTFIX         "nlink"
#define OVL_XATTR_UPPER_POSTFIX         "upper"
#define OVL_XATTR_UUID_POSTFIX          "uuid"
#define OVL_XATTR_METACOPY_POSTFIX      "metacopy"
#define OVL_XATTR_PROTATTR_POSTFIX      "protattr"
#define OVL_XATTR_XWHITEOUT_POSTFIX     "whiteout"

#define OVL_XATTR_TAB_ENTRY(x) \
        [x] = { [false] = OVL_XATTR_TRUSTED_PREFIX x ## _POSTFIX, \
                [true] = OVL_XATTR_USER_PREFIX x ## _POSTFIX }

const char *const ovl_xattr_table[][2] = {
        OVL_XATTR_TAB_ENTRY(OVL_XATTR_OPAQUE),
        OVL_XATTR_TAB_ENTRY(OVL_XATTR_REDIRECT),
        OVL_XATTR_TAB_ENTRY(OVL_XATTR_ORIGIN),
        OVL_XATTR_TAB_ENTRY(OVL_XATTR_IMPURE),
        OVL_XATTR_TAB_ENTRY(OVL_XATTR_NLINK),
        OVL_XATTR_TAB_ENTRY(OVL_XATTR_UPPER),
        OVL_XATTR_TAB_ENTRY(OVL_XATTR_UUID),
        OVL_XATTR_TAB_ENTRY(OVL_XATTR_METACOPY),
        OVL_XATTR_TAB_ENTRY(OVL_XATTR_PROTATTR),
        OVL_XATTR_TAB_ENTRY(OVL_XATTR_XWHITEOUT),
};

int ovl_check_setxattr(struct ovl_fs *ofs, struct dentry *upperdentry,
                       enum ovl_xattr ox, const void *value, size_t size,
                       int xerr)
{
        int err;

        if (ofs->noxattr)
                return xerr;

        err = ovl_setxattr(ofs, upperdentry, ox, value, size);

        if (err == -EOPNOTSUPP) {
                pr_warn("cannot set %s xattr on upper\n", ovl_xattr(ofs, ox));
                ofs->noxattr = true;
                return xerr;
        }

        return err;
}

int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry)
{
        struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
        int err;

        if (ovl_test_flag(OVL_IMPURE, d_inode(dentry)))
                return 0;

        /*
         * Do not fail when upper doesn't support xattrs.
         * Upper inodes won't have origin nor redirect xattr anyway.
         */
        err = ovl_check_setxattr(ofs, upperdentry, OVL_XATTR_IMPURE, "y", 1, 0);
        if (!err)
                ovl_set_flag(OVL_IMPURE, d_inode(dentry));

        return err;
}


#define OVL_PROTATTR_MAX 32 /* Reserved for future flags */

void ovl_check_protattr(struct inode *inode, struct dentry *upper)
{
        struct ovl_fs *ofs = OVL_FS(inode->i_sb);
        u32 iflags = inode->i_flags & OVL_PROT_I_FLAGS_MASK;
        char buf[OVL_PROTATTR_MAX+1];
        int res, n;

        res = ovl_getxattr_upper(ofs, upper, OVL_XATTR_PROTATTR, buf,
                                 OVL_PROTATTR_MAX);
        if (res < 0)
                return;

        /*
         * Initialize inode flags from overlay.protattr xattr and upper inode
         * flags.  If upper inode has those fileattr flags set (i.e. from old
         * kernel), we do not clear them on ovl_get_inode(), but we will clear
         * them on next fileattr_set().
         */
        for (n = 0; n < res; n++) {
                if (buf[n] == 'a')
                        iflags |= S_APPEND;
                else if (buf[n] == 'i')
                        iflags |= S_IMMUTABLE;
                else
                        break;
        }

        if (!res || n < res) {
                pr_warn_ratelimited("incompatible overlay.protattr format (%pd2, len=%d)\n",
                                    upper, res);
        } else {
                inode_set_flags(inode, iflags, OVL_PROT_I_FLAGS_MASK);
        }
}

int ovl_set_protattr(struct inode *inode, struct dentry *upper,
                      struct file_kattr *fa)
{
        struct ovl_fs *ofs = OVL_FS(inode->i_sb);
        char buf[OVL_PROTATTR_MAX];
        int len = 0, err = 0;
        u32 iflags = 0;

        BUILD_BUG_ON(HWEIGHT32(OVL_PROT_FS_FLAGS_MASK) > OVL_PROTATTR_MAX);

        if (fa->flags & FS_APPEND_FL) {
                buf[len++] = 'a';
                iflags |= S_APPEND;
        }
        if (fa->flags & FS_IMMUTABLE_FL) {
                buf[len++] = 'i';
                iflags |= S_IMMUTABLE;
        }

        /*
         * Do not allow to set protection flags when upper doesn't support
         * xattrs, because we do not set those fileattr flags on upper inode.
         * Remove xattr if it exist and all protection flags are cleared.
         */
        if (len) {
                err = ovl_check_setxattr(ofs, upper, OVL_XATTR_PROTATTR,
                                         buf, len, -EPERM);
        } else if (inode->i_flags & OVL_PROT_I_FLAGS_MASK) {
                err = ovl_removexattr(ofs, upper, OVL_XATTR_PROTATTR);
                if (err == -EOPNOTSUPP || err == -ENODATA)
                        err = 0;
        }
        if (err)
                return err;

        inode_set_flags(inode, iflags, OVL_PROT_I_FLAGS_MASK);

        /* Mask out the fileattr flags that should not be set in upper inode */
        fa->flags &= ~OVL_PROT_FS_FLAGS_MASK;
        fa->fsx_xflags &= ~OVL_PROT_FSX_FLAGS_MASK;

        return 0;
}

/*
 * Caller must hold a reference to inode to prevent it from being freed while
 * it is marked inuse.
 */
bool ovl_inuse_trylock(struct dentry *dentry)
{
        struct inode *inode = d_inode(dentry);
        bool locked = false;

        spin_lock(&inode->i_lock);
        if (!(inode_state_read(inode) & I_OVL_INUSE)) {
                inode_state_set(inode, I_OVL_INUSE);
                locked = true;
        }
        spin_unlock(&inode->i_lock);

        return locked;
}

void ovl_inuse_unlock(struct dentry *dentry)
{
        if (dentry) {
                struct inode *inode = d_inode(dentry);

                spin_lock(&inode->i_lock);
                WARN_ON(!(inode_state_read(inode) & I_OVL_INUSE));
                inode_state_clear(inode, I_OVL_INUSE);
                spin_unlock(&inode->i_lock);
        }
}

bool ovl_is_inuse(struct dentry *dentry)
{
        struct inode *inode = d_inode(dentry);
        bool inuse;

        spin_lock(&inode->i_lock);
        inuse = (inode_state_read(inode) & I_OVL_INUSE);
        spin_unlock(&inode->i_lock);

        return inuse;
}

/*
 * Does this overlay dentry need to be indexed on copy up?
 */
bool ovl_need_index(struct dentry *dentry)
{
        struct dentry *lower = ovl_dentry_lower(dentry);

        if (!lower || !ovl_indexdir(dentry->d_sb))
                return false;

        /* Index all files for NFS export and consistency verification */
        if (ovl_index_all(dentry->d_sb))
                return true;

        /* Index only lower hardlinks on copy up */
        if (!d_is_dir(lower) && d_inode(lower)->i_nlink > 1)
                return true;

        return false;
}

/* Caller must hold OVL_I(inode)->lock */
static void ovl_cleanup_index(struct dentry *dentry)
{
        struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
        struct dentry *indexdir = ovl_indexdir(dentry->d_sb);
        struct dentry *lowerdentry = ovl_dentry_lower(dentry);
        struct dentry *upperdentry = ovl_dentry_upper(dentry);
        struct dentry *index = NULL;
        struct inode *inode;
        struct qstr name = { };
        bool got_write = false;
        int err;

        err = ovl_get_index_name(ofs, lowerdentry, &name);
        if (err)
                goto fail;

        err = ovl_want_write(dentry);
        if (err)
                goto fail;

        got_write = true;
        inode = d_inode(upperdentry);
        if (!S_ISDIR(inode->i_mode) && inode->i_nlink != 1) {
                pr_warn_ratelimited("cleanup linked index (%pd2, ino=%lu, nlink=%u)\n",
                                    upperdentry, inode->i_ino, inode->i_nlink);
                /*
                 * We either have a bug with persistent union nlink or a lower
                 * hardlink was added while overlay is mounted. Adding a lower
                 * hardlink and then unlinking all overlay hardlinks would drop
                 * overlay nlink to zero before all upper inodes are unlinked.
                 * As a safety measure, when that situation is detected, set
                 * the overlay nlink to the index inode nlink minus one for the
                 * index entry itself.
                 */
                set_nlink(d_inode(dentry), inode->i_nlink - 1);
                ovl_set_nlink_upper(dentry);
                goto out;
        }

        index = ovl_lookup_upper_unlocked(ofs, name.name, indexdir, name.len);
        err = PTR_ERR(index);
        if (IS_ERR(index)) {
                index = NULL;
        } else if (ovl_index_all(dentry->d_sb)) {
                /* Whiteout orphan index to block future open by handle */
                err = ovl_cleanup_and_whiteout(OVL_FS(dentry->d_sb),
                                               indexdir, index);
        } else {
                /* Cleanup orphan index entries */
                err = ovl_cleanup(ofs, indexdir, index);
        }
        if (err)
                goto fail;

out:
        if (got_write)
                ovl_drop_write(dentry);
        kfree(name.name);
        dput(index);
        return;

fail:
        pr_err("cleanup index of '%pd2' failed (%i)\n", dentry, err);
        goto out;
}

/*
 * Operations that change overlay inode and upper inode nlink need to be
 * synchronized with copy up for persistent nlink accounting.
 */
int ovl_nlink_start(struct dentry *dentry)
{
        struct inode *inode = d_inode(dentry);
        int err;

        if (WARN_ON(!inode))
                return -ENOENT;

        /*
         * With inodes index is enabled, we store the union overlay nlink
         * in an xattr on the index inode. When whiting out an indexed lower,
         * we need to decrement the overlay persistent nlink, but before the
         * first copy up, we have no upper index inode to store the xattr.
         *
         * As a workaround, before whiteout/rename over an indexed lower,
         * copy up to create the upper index. Creating the upper index will
         * initialize the overlay nlink, so it could be dropped if unlink
         * or rename succeeds.
         *
         * TODO: implement metadata only index copy up when called with
         *       ovl_copy_up_flags(dentry, O_PATH).
         */
        if (ovl_need_index(dentry) && !ovl_dentry_has_upper_alias(dentry)) {
                err = ovl_copy_up(dentry);
                if (err)
                        return err;
        }

        err = ovl_inode_lock_interruptible(inode);
        if (err)
                return err;

        err = ovl_want_write(dentry);
        if (err)
                goto out_unlock;

        if (d_is_dir(dentry) || !ovl_test_flag(OVL_INDEX, inode))
                return 0;

        /*
         * The overlay inode nlink should be incremented/decremented IFF the
         * upper operation succeeds, along with nlink change of upper inode.
         * Therefore, before link/unlink/rename, we store the union nlink
         * value relative to the upper inode nlink in an upper inode xattr.
         */
        with_ovl_creds(dentry->d_sb)
                err = ovl_set_nlink_upper(dentry);
        if (err)
                goto out_drop_write;

        return 0;

out_drop_write:
        ovl_drop_write(dentry);
out_unlock:
        ovl_inode_unlock(inode);

        return err;
}

void ovl_nlink_end(struct dentry *dentry)
{
        struct inode *inode = d_inode(dentry);

        ovl_drop_write(dentry);

        if (ovl_test_flag(OVL_INDEX, inode) && inode->i_nlink == 0) {
                with_ovl_creds(dentry->d_sb)
                        ovl_cleanup_index(dentry);
        }

        ovl_inode_unlock(inode);
}

int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *work,
                            struct dentry *upperdir, struct dentry *upper)
{
        struct dentry *trap;

        /* Workdir should not be subdir of upperdir and vice versa */
        trap = lock_rename(workdir, upperdir);
        if (IS_ERR(trap))
                goto err;
        if (trap)
                goto err_unlock;
        if (work && (work->d_parent != workdir || d_unhashed(work)))
                goto err_unlock;
        if (upper && (upper->d_parent != upperdir || d_unhashed(upper)))
                goto err_unlock;

        return 0;

err_unlock:
        unlock_rename(workdir, upperdir);
err:
        pr_err("failed to lock workdir+upperdir\n");
        return -EIO;
}

/*
 * err < 0, 0 if no metacopy xattr, metacopy data size if xattr found.
 * an empty xattr returns OVL_METACOPY_MIN_SIZE to distinguish from no xattr value.
 */
int ovl_check_metacopy_xattr(struct ovl_fs *ofs, const struct path *path,
                             struct ovl_metacopy *data)
{
        int res;

        /* Only regular files can have metacopy xattr */
        if (!S_ISREG(d_inode(path->dentry)->i_mode))
                return 0;

        res = ovl_path_getxattr(ofs, path, OVL_XATTR_METACOPY,
                                data, data ? OVL_METACOPY_MAX_SIZE : 0);
        if (res < 0) {
                if (res == -ENODATA || res == -EOPNOTSUPP)
                        return 0;
                /*
                 * getxattr on user.* may fail with EACCES in case there's no
                 * read permission on the inode.  Not much we can do, other than
                 * tell the caller that this is not a metacopy inode.
                 */
                if (ofs->config.userxattr && res == -EACCES)
                        return 0;
                goto out;
        }

        if (res == 0) {
                /* Emulate empty data for zero size metacopy xattr */
                res = OVL_METACOPY_MIN_SIZE;
                if (data) {
                        memset(data, 0, res);
                        data->len = res;
                }
        } else if (res < OVL_METACOPY_MIN_SIZE) {
                pr_warn_ratelimited("metacopy file '%pd' has too small xattr\n",
                                    path->dentry);
                return -EIO;
        } else if (data) {
                if (data->version != 0) {
                        pr_warn_ratelimited("metacopy file '%pd' has unsupported version\n",
                                            path->dentry);
                        return -EIO;
                }
                if (res != data->len) {
                        pr_warn_ratelimited("metacopy file '%pd' has invalid xattr size\n",
                                            path->dentry);
                        return -EIO;
                }
        }

        return res;
out:
        pr_warn_ratelimited("failed to get metacopy (%i)\n", res);
        return res;
}

int ovl_set_metacopy_xattr(struct ovl_fs *ofs, struct dentry *d, struct ovl_metacopy *metacopy)
{
        size_t len = metacopy->len;

        /* If no flags or digest fall back to empty metacopy file */
        if (metacopy->version == 0 && metacopy->flags == 0 && metacopy->digest_algo == 0)
                len = 0;

        return ovl_check_setxattr(ofs, d, OVL_XATTR_METACOPY,
                                  metacopy, len, -EOPNOTSUPP);
}

bool ovl_is_metacopy_dentry(struct dentry *dentry)
{
        struct ovl_entry *oe = OVL_E(dentry);

        if (!d_is_reg(dentry))
                return false;

        if (ovl_dentry_upper(dentry)) {
                if (!ovl_has_upperdata(d_inode(dentry)))
                        return true;
                return false;
        }

        return (ovl_numlower(oe) > 1);
}

char *ovl_get_redirect_xattr(struct ovl_fs *ofs, const struct path *path, int padding)
{
        int res;
        char *s, *next, *buf = NULL;

        res = ovl_path_getxattr(ofs, path, OVL_XATTR_REDIRECT, NULL, 0);
        if (res == -ENODATA || res == -EOPNOTSUPP)
                return NULL;
        if (res < 0)
                goto fail;
        if (res == 0)
                goto invalid;

        buf = kzalloc(res + padding + 1, GFP_KERNEL);
        if (!buf)
                return ERR_PTR(-ENOMEM);

        res = ovl_path_getxattr(ofs, path, OVL_XATTR_REDIRECT, buf, res);
        if (res < 0)
                goto fail;
        if (res == 0)
                goto invalid;

        if (buf[0] == '/') {
                for (s = buf; *s++ == '/'; s = next) {
                        next = strchrnul(s, '/');
                        if (s == next)
                                goto invalid;
                }
        } else {
                if (strchr(buf, '/') != NULL)
                        goto invalid;
        }

        return buf;
invalid:
        pr_warn_ratelimited("invalid redirect (%s)\n", buf);
        res = -EINVAL;
        goto err_free;
fail:
        pr_warn_ratelimited("failed to get redirect (%i)\n", res);
err_free:
        kfree(buf);
        return ERR_PTR(res);
}

/* Call with mounter creds as it may open the file */
int ovl_ensure_verity_loaded(const struct path *datapath)
{
        struct inode *inode = d_inode(datapath->dentry);
        struct file *filp;

        if (!fsverity_active(inode) && IS_VERITY(inode)) {
                /*
                 * If this inode was not yet opened, the verity info hasn't been
                 * loaded yet, so we need to do that here to force it into memory.
                 */
                filp = kernel_file_open(datapath, O_RDONLY, current_cred());
                if (IS_ERR(filp))
                        return PTR_ERR(filp);
                fput(filp);
        }

        return 0;
}

int ovl_validate_verity(struct ovl_fs *ofs,
                        const struct path *metapath,
                        const struct path *datapath)
{
        struct ovl_metacopy metacopy_data;
        u8 actual_digest[FS_VERITY_MAX_DIGEST_SIZE];
        int xattr_digest_size, digest_size;
        int xattr_size, err;
        u8 verity_algo;

        if (!ofs->config.verity_mode ||
            /* Verity only works on regular files */
            !S_ISREG(d_inode(metapath->dentry)->i_mode))
                return 0;

        xattr_size = ovl_check_metacopy_xattr(ofs, metapath, &metacopy_data);
        if (xattr_size < 0)
                return xattr_size;

        if (!xattr_size || !metacopy_data.digest_algo) {
                if (ofs->config.verity_mode == OVL_VERITY_REQUIRE) {
                        pr_warn_ratelimited("metacopy file '%pd' has no digest specified\n",
                                            metapath->dentry);
                        return -EIO;
                }
                return 0;
        }

        xattr_digest_size = ovl_metadata_digest_size(&metacopy_data);

        err = ovl_ensure_verity_loaded(datapath);
        if (err < 0) {
                pr_warn_ratelimited("lower file '%pd' failed to load fs-verity info\n",
                                    datapath->dentry);
                return -EIO;
        }

        digest_size = fsverity_get_digest(d_inode(datapath->dentry), actual_digest,
                                          &verity_algo, NULL);
        if (digest_size == 0) {
                pr_warn_ratelimited("lower file '%pd' has no fs-verity digest\n", datapath->dentry);
                return -EIO;
        }

        if (xattr_digest_size != digest_size ||
            metacopy_data.digest_algo != verity_algo ||
            memcmp(metacopy_data.digest, actual_digest, xattr_digest_size) != 0) {
                pr_warn_ratelimited("lower file '%pd' has the wrong fs-verity digest\n",
                                    datapath->dentry);
                return -EIO;
        }

        return 0;
}

int ovl_get_verity_digest(struct ovl_fs *ofs, const struct path *src,
                          struct ovl_metacopy *metacopy)
{
        int err, digest_size;

        if (!ofs->config.verity_mode || !S_ISREG(d_inode(src->dentry)->i_mode))
                return 0;

        err = ovl_ensure_verity_loaded(src);
        if (err < 0) {
                pr_warn_ratelimited("lower file '%pd' failed to load fs-verity info\n",
                                    src->dentry);
                return -EIO;
        }

        digest_size = fsverity_get_digest(d_inode(src->dentry),
                                          metacopy->digest, &metacopy->digest_algo, NULL);
        if (digest_size == 0 ||
            WARN_ON_ONCE(digest_size > FS_VERITY_MAX_DIGEST_SIZE)) {
                if (ofs->config.verity_mode == OVL_VERITY_REQUIRE) {
                        pr_warn_ratelimited("lower file '%pd' has no fs-verity digest\n",
                                            src->dentry);
                        return -EIO;
                }
                return 0;
        }

        metacopy->len += digest_size;
        return 0;
}

/*
 * ovl_sync_status() - Check fs sync status for volatile mounts
 *
 * Returns 1 if this is not a volatile mount and a real sync is required.
 *
 * Returns 0 if syncing can be skipped because mount is volatile, and no errors
 * have occurred on the upperdir since the mount.
 *
 * Returns -errno if it is a volatile mount, and the error that occurred since
 * the last mount. If the error code changes, it'll return the latest error
 * code.
 */

int ovl_sync_status(struct ovl_fs *ofs)
{
        struct vfsmount *mnt;

        if (ovl_should_sync(ofs))
                return 1;

        mnt = ovl_upper_mnt(ofs);
        if (!mnt)
                return 0;

        return errseq_check(&mnt->mnt_sb->s_wb_err, ofs->errseq);
}

/*
 * ovl_copyattr() - copy inode attributes from layer to ovl inode
 *
 * When overlay copies inode information from an upper or lower layer to the
 * relevant overlay inode it will apply the idmapping of the upper or lower
 * layer when doing so ensuring that the ovl inode ownership will correctly
 * reflect the ownership of the idmapped upper or lower layer. For example, an
 * idmapped upper or lower layer mapping id 1001 to id 1000 will take care to
 * map any lower or upper inode owned by id 1001 to id 1000. These mapping
 * helpers are nops when the relevant layer isn't idmapped.
 */
void ovl_copyattr(struct inode *inode)
{
        struct path realpath;
        struct inode *realinode;
        struct mnt_idmap *real_idmap;
        vfsuid_t vfsuid;
        vfsgid_t vfsgid;

        realinode = ovl_i_path_real(inode, &realpath);
        real_idmap = mnt_idmap(realpath.mnt);

        spin_lock(&inode->i_lock);
        vfsuid = i_uid_into_vfsuid(real_idmap, realinode);
        vfsgid = i_gid_into_vfsgid(real_idmap, realinode);

        inode->i_uid = vfsuid_into_kuid(vfsuid);
        inode->i_gid = vfsgid_into_kgid(vfsgid);
        inode->i_mode = realinode->i_mode;
        inode_set_atime_to_ts(inode, inode_get_atime(realinode));
        inode_set_mtime_to_ts(inode, inode_get_mtime(realinode));
        inode_set_ctime_to_ts(inode, inode_get_ctime(realinode));
        i_size_write(inode, i_size_read(realinode));
        spin_unlock(&inode->i_lock);
}