// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/fs/nfs/file.c
 *
 *  Copyright (C) 1992  Rick Sladkey
 *
 *  Changes Copyright (C) 1994 by Florian La Roche
 *   - Do not copy data too often around in the kernel.
 *   - In nfs_file_read the return value of kmalloc wasn't checked.
 *   - Put in a better version of read look-ahead buffering. Original idea
 *     and implementation by Wai S Kok elekokws@ee.nus.sg.
 *
 *  Expire cache on write to a file by Wai S Kok (Oct 1994).
 *
 *  Total rewrite of read side for new NFS buffer cache.. Linus.
 *
 *  nfs regular file handling functions
 */

#include <linux/module.h>
#include <linux/time.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/stat.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_mount.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/gfp.h>
#include <linux/rmap.h>
#include <linux/swap.h>
#include <linux/compaction.h>

#include <linux/uaccess.h>
#include <linux/filelock.h>

#include "delegation.h"
#include "internal.h"
#include "iostat.h"
#include "fscache.h"
#include "pnfs.h"

#include "nfstrace.h"

#define NFSDBG_FACILITY         NFSDBG_FILE

static const struct vm_operations_struct nfs_file_vm_ops;

int nfs_check_flags(int flags)
{
        if ((flags & (O_APPEND | O_DIRECT)) == (O_APPEND | O_DIRECT))
                return -EINVAL;

        return 0;
}
EXPORT_SYMBOL_GPL(nfs_check_flags);

/*
 * Open file
 */
static int
nfs_file_open(struct inode *inode, struct file *filp)
{
        int res;

        dprintk("NFS: open file(%pD2)\n", filp);

        nfs_inc_stats(inode, NFSIOS_VFSOPEN);
        res = nfs_check_flags(filp->f_flags);
        if (res)
                return res;

        res = nfs_open(inode, filp);
        if (res == 0)
                filp->f_mode |= FMODE_CAN_ODIRECT;
        return res;
}

int
nfs_file_release(struct inode *inode, struct file *filp)
{
        dprintk("NFS: release(%pD2)\n", filp);

        nfs_inc_stats(inode, NFSIOS_VFSRELEASE);
        nfs_file_clear_open_context(filp);
        nfs_fscache_release_file(inode, filp);
        return 0;
}
EXPORT_SYMBOL_GPL(nfs_file_release);

/**
 * nfs_revalidate_file_size - Revalidate the file size
 * @inode: pointer to inode struct
 * @filp: pointer to struct file
 *
 * Revalidates the file length. This is basically a wrapper around
 * nfs_revalidate_inode() that takes into account the fact that we may
 * have cached writes (in which case we don't care about the server's
 * idea of what the file length is), or O_DIRECT (in which case we
 * shouldn't trust the cache).
 */
static int nfs_revalidate_file_size(struct inode *inode, struct file *filp)
{
        struct nfs_server *server = NFS_SERVER(inode);

        if (filp->f_flags & O_DIRECT)
                goto force_reval;
        if (nfs_check_cache_invalid(inode, NFS_INO_INVALID_SIZE))
                goto force_reval;
        return 0;
force_reval:
        return __nfs_revalidate_inode(server, inode);
}

loff_t nfs_file_llseek(struct file *filp, loff_t offset, int whence)
{
        dprintk("NFS: llseek file(%pD2, %lld, %d)\n",
                        filp, offset, whence);

        /*
         * whence == SEEK_END || SEEK_DATA || SEEK_HOLE => we must revalidate
         * the cached file length
         */
        if (whence != SEEK_SET && whence != SEEK_CUR) {
                struct inode *inode = filp->f_mapping->host;

                int retval = nfs_revalidate_file_size(inode, filp);
                if (retval < 0)
                        return (loff_t)retval;
        }

        return generic_file_llseek(filp, offset, whence);
}
EXPORT_SYMBOL_GPL(nfs_file_llseek);

/*
 * Flush all dirty pages, and check for write errors.
 */
static int
nfs_file_flush(struct file *file, fl_owner_t id)
{
        struct inode    *inode = file_inode(file);
        errseq_t since;

        dprintk("NFS: flush(%pD2)\n", file);

        nfs_inc_stats(inode, NFSIOS_VFSFLUSH);
        if ((file->f_mode & FMODE_WRITE) == 0)
                return 0;

        /* Flush writes to the server and return any errors */
        since = filemap_sample_wb_err(file->f_mapping);
        nfs_wb_all(inode);
        return filemap_check_wb_err(file->f_mapping, since);
}

ssize_t
nfs_file_read(struct kiocb *iocb, struct iov_iter *to)
{
        struct inode *inode = file_inode(iocb->ki_filp);
        ssize_t result;

        trace_nfs_file_read(iocb, to);

        if (iocb->ki_flags & IOCB_DIRECT)
                return nfs_file_direct_read(iocb, to, false);

        dprintk("NFS: read(%pD2, %zu@%lu)\n",
                iocb->ki_filp,
                iov_iter_count(to), (unsigned long) iocb->ki_pos);

        result = nfs_start_io_read(inode);
        if (result)
                return result;

        result = nfs_revalidate_mapping(inode, iocb->ki_filp->f_mapping);
        if (!result) {
                result = generic_file_read_iter(iocb, to);
                if (result > 0)
                        nfs_add_stats(inode, NFSIOS_NORMALREADBYTES, result);
        }
        nfs_end_io_read(inode);
        return result;
}
EXPORT_SYMBOL_GPL(nfs_file_read);

ssize_t
nfs_file_splice_read(struct file *in, loff_t *ppos, struct pipe_inode_info *pipe,
                     size_t len, unsigned int flags)
{
        struct inode *inode = file_inode(in);
        ssize_t result;

        dprintk("NFS: splice_read(%pD2, %zu@%llu)\n", in, len, *ppos);

        result = nfs_start_io_read(inode);
        if (result)
                return result;

        result = nfs_revalidate_mapping(inode, in->f_mapping);
        if (!result) {
                result = filemap_splice_read(in, ppos, pipe, len, flags);
                if (result > 0)
                        nfs_add_stats(inode, NFSIOS_NORMALREADBYTES, result);
        }
        nfs_end_io_read(inode);
        return result;
}
EXPORT_SYMBOL_GPL(nfs_file_splice_read);

int
nfs_file_mmap_prepare(struct vm_area_desc *desc)
{
        struct file *file = desc->file;
        struct inode *inode = file_inode(file);
        int     status;

        dprintk("NFS: mmap(%pD2)\n", file);

        /* Note: generic_file_mmap_prepare() returns ENOSYS on nommu systems
         *       so we call that before revalidating the mapping
         */
        status = generic_file_mmap_prepare(desc);
        if (!status) {
                desc->vm_ops = &nfs_file_vm_ops;
                status = nfs_revalidate_mapping(inode, file->f_mapping);
        }
        return status;
}
EXPORT_SYMBOL_GPL(nfs_file_mmap_prepare);

/*
 * Flush any dirty pages for this process, and check for write errors.
 * The return status from this call provides a reliable indication of
 * whether any write errors occurred for this process.
 */
static int
nfs_file_fsync_commit(struct file *file, int datasync)
{
        struct inode *inode = file_inode(file);
        int ret, ret2;

        dprintk("NFS: fsync file(%pD2) datasync %d\n", file, datasync);

        nfs_inc_stats(inode, NFSIOS_VFSFSYNC);
        ret = nfs_commit_inode(inode, FLUSH_SYNC);
        ret2 = file_check_and_advance_wb_err(file);
        if (ret2 < 0)
                return ret2;
        return ret;
}

int
nfs_file_fsync(struct file *file, loff_t start, loff_t end, int datasync)
{
        struct inode *inode = file_inode(file);
        struct nfs_inode *nfsi = NFS_I(inode);
        long save_nredirtied = atomic_long_read(&nfsi->redirtied_pages);
        long nredirtied;
        int ret;

        trace_nfs_fsync_enter(inode);

        for (;;) {
                ret = file_write_and_wait_range(file, start, end);
                if (ret != 0)
                        break;
                ret = nfs_file_fsync_commit(file, datasync);
                if (ret != 0)
                        break;
                ret = pnfs_sync_inode(inode, !!datasync);
                if (ret != 0)
                        break;
                nredirtied = atomic_long_read(&nfsi->redirtied_pages);
                if (nredirtied == save_nredirtied)
                        break;
                save_nredirtied = nredirtied;
        }

        trace_nfs_fsync_exit(inode, ret);
        return ret;
}
EXPORT_SYMBOL_GPL(nfs_file_fsync);

void nfs_truncate_last_folio(struct address_space *mapping, loff_t from,
                             loff_t to)
{
        struct folio *folio;

        if (from >= to)
                return;

        folio = filemap_lock_folio(mapping, from >> PAGE_SHIFT);
        if (IS_ERR(folio))
                return;

        if (folio_mkclean(folio))
                folio_mark_dirty(folio);

        if (folio_test_uptodate(folio)) {
                loff_t fpos = folio_pos(folio);
                size_t offset = from - fpos;
                size_t end = folio_size(folio);

                if (to - fpos < end)
                        end = to - fpos;
                folio_zero_segment(folio, offset, end);
                trace_nfs_size_truncate_folio(mapping->host, to);
        }

        folio_unlock(folio);
        folio_put(folio);
}
EXPORT_SYMBOL_GPL(nfs_truncate_last_folio);

/*
 * Decide whether a read/modify/write cycle may be more efficient
 * then a modify/write/read cycle when writing to a page in the
 * page cache.
 *
 * Some pNFS layout drivers can only read/write at a certain block
 * granularity like all block devices and therefore we must perform
 * read/modify/write whenever a page hasn't read yet and the data
 * to be written there is not aligned to a block boundary and/or
 * smaller than the block size.
 *
 * The modify/write/read cycle may occur if a page is read before
 * being completely filled by the writer.  In this situation, the
 * page must be completely written to stable storage on the server
 * before it can be refilled by reading in the page from the server.
 * This can lead to expensive, small, FILE_SYNC mode writes being
 * done.
 *
 * It may be more efficient to read the page first if the file is
 * open for reading in addition to writing, the page is not marked
 * as Uptodate, it is not dirty or waiting to be committed,
 * indicating that it was previously allocated and then modified,
 * that there were valid bytes of data in that range of the file,
 * and that the new data won't completely replace the old data in
 * that range of the file.
 */
static bool nfs_folio_is_full_write(struct folio *folio, loff_t pos,
                                    unsigned int len)
{
        unsigned int pglen = nfs_folio_length(folio);
        unsigned int offset = offset_in_folio(folio, pos);
        unsigned int end = offset + len;

        return !pglen || (end >= pglen && !offset);
}

static bool nfs_want_read_modify_write(struct file *file, struct folio *folio,
                                       loff_t pos, unsigned int len)
{
        /*
         * Up-to-date pages, those with ongoing or full-page write
         * don't need read/modify/write
         */
        if (folio_test_uptodate(folio) || folio_test_private(folio) ||
            nfs_folio_is_full_write(folio, pos, len))
                return false;

        if (pnfs_ld_read_whole_page(file_inode(file)))
                return true;
        if (folio_test_dropbehind(folio))
                return false;
        /* Open for reading too? */
        if (file->f_mode & FMODE_READ)
                return true;
        return false;
}

/*
 * This does the "real" work of the write. We must allocate and lock the
 * page to be sent back to the generic routine, which then copies the
 * data from user space.
 *
 * If the writer ends up delaying the write, the writer needs to
 * increment the page use counts until he is done with the page.
 */
static int nfs_write_begin(const struct kiocb *iocb,
                           struct address_space *mapping,
                           loff_t pos, unsigned len, struct folio **foliop,
                           void **fsdata)
{
        struct folio *folio;
        struct file *file = iocb->ki_filp;
        int once_thru = 0;
        int ret;

        trace_nfs_write_begin(file_inode(file), pos, len);

        dfprintk(PAGECACHE, "NFS: write_begin(%pD2(%lu), %u@%lld)\n",
                file, mapping->host->i_ino, len, (long long) pos);
        nfs_truncate_last_folio(mapping, i_size_read(mapping->host), pos);

start:
        folio = write_begin_get_folio(iocb, mapping, pos >> PAGE_SHIFT, len);
        if (IS_ERR(folio)) {
                ret = PTR_ERR(folio);
                goto out;
        }
        *foliop = folio;

        ret = nfs_flush_incompatible(file, folio);
        if (ret) {
                folio_unlock(folio);
                folio_put(folio);
        } else if (!once_thru &&
                   nfs_want_read_modify_write(file, folio, pos, len)) {
                once_thru = 1;
                folio_clear_dropbehind(folio);
                ret = nfs_read_folio(file, folio);
                folio_put(folio);
                if (!ret)
                        goto start;
        }
out:
        trace_nfs_write_begin_done(file_inode(file), pos, len, ret);
        return ret;
}

static int nfs_write_end(const struct kiocb *iocb,
                         struct address_space *mapping,
                         loff_t pos, unsigned len, unsigned copied,
                         struct folio *folio, void *fsdata)
{
        struct file *file = iocb->ki_filp;
        struct nfs_open_context *ctx = nfs_file_open_context(file);
        unsigned offset = offset_in_folio(folio, pos);
        int status;

        trace_nfs_write_end(file_inode(file), pos, len);
        dfprintk(PAGECACHE, "NFS: write_end(%pD2(%lu), %u@%lld)\n",
                file, mapping->host->i_ino, len, (long long) pos);

        /*
         * Zero any uninitialised parts of the page, and then mark the page
         * as up to date if it turns out that we're extending the file.
         */
        if (!folio_test_uptodate(folio)) {
                size_t fsize = folio_size(folio);
                unsigned pglen = nfs_folio_length(folio);
                unsigned end = offset + copied;

                if (pglen == 0) {
                        folio_zero_segments(folio, 0, offset, end, fsize);
                        folio_mark_uptodate(folio);
                } else if (end >= pglen) {
                        folio_zero_segment(folio, end, fsize);
                        if (offset == 0)
                                folio_mark_uptodate(folio);
                } else
                        folio_zero_segment(folio, pglen, fsize);
        }

        status = nfs_update_folio(file, folio, offset, copied);

        folio_unlock(folio);
        folio_put(folio);

        if (status < 0) {
                trace_nfs_write_end_done(file_inode(file), pos, len, status);
                return status;
        }
        NFS_I(mapping->host)->write_io += copied;

        if (nfs_ctx_key_to_expire(ctx, mapping->host))
                nfs_wb_all(mapping->host);

        trace_nfs_write_end_done(file_inode(file), pos, len, copied);
        return copied;
}

/*
 * Partially or wholly invalidate a page
 * - Release the private state associated with a page if undergoing complete
 *   page invalidation
 * - Called if either PG_private or PG_fscache is set on the page
 * - Caller holds page lock
 */
static void nfs_invalidate_folio(struct folio *folio, size_t offset,
                                size_t length)
{
        struct inode *inode = folio->mapping->host;
        dfprintk(PAGECACHE, "NFS: invalidate_folio(%lu, %zu, %zu)\n",
                 folio->index, offset, length);

        /* Cancel any unstarted writes on this page */
        if (offset != 0 || length < folio_size(folio))
                nfs_wb_folio(inode, folio);
        else
                nfs_wb_folio_cancel(inode, folio);
        folio_wait_private_2(folio); /* [DEPRECATED] */
        trace_nfs_invalidate_folio(inode, folio_pos(folio) + offset, length);
}

/*
 * Attempt to release the private state associated with a folio
 * - Called if either private or fscache flags are set on the folio
 * - Caller holds folio lock
 * - Return true (may release folio) or false (may not)
 */
static bool nfs_release_folio(struct folio *folio, gfp_t gfp)
{
        dfprintk(PAGECACHE, "NFS: release_folio(%p)\n", folio);

        /* If the private flag is set, then the folio is not freeable */
        if (folio_test_private(folio)) {
                if ((current_gfp_context(gfp) & GFP_KERNEL) != GFP_KERNEL ||
                    current_is_kswapd() || current_is_kcompactd())
                        return false;
                if (nfs_wb_folio_reclaim(folio->mapping->host, folio) < 0 ||
                    folio_test_private(folio))
                        return false;
        }
        return nfs_fscache_release_folio(folio, gfp);
}

static void nfs_check_dirty_writeback(struct folio *folio,
                                bool *dirty, bool *writeback)
{
        struct nfs_inode *nfsi;
        struct address_space *mapping = folio->mapping;

        /*
         * Check if an unstable folio is currently being committed and
         * if so, have the VM treat it as if the folio is under writeback
         * so it will not block due to folios that will shortly be freeable.
         */
        nfsi = NFS_I(mapping->host);
        if (atomic_read(&nfsi->commit_info.rpcs_out)) {
                *writeback = true;
                return;
        }

        /*
         * If the private flag is set, then the folio is not freeable
         * and as the inode is not being committed, it's not going to
         * be cleaned in the near future so treat it as dirty
         */
        if (folio_test_private(folio))
                *dirty = true;
}

/*
 * Attempt to clear the private state associated with a page when an error
 * occurs that requires the cached contents of an inode to be written back or
 * destroyed
 * - Called if either PG_private or fscache is set on the page
 * - Caller holds page lock
 * - Return 0 if successful, -error otherwise
 */
static int nfs_launder_folio(struct folio *folio)
{
        struct inode *inode = folio->mapping->host;
        int ret;

        dfprintk(PAGECACHE, "NFS: launder_folio(%ld, %llu)\n",
                inode->i_ino, folio_pos(folio));

        folio_wait_private_2(folio); /* [DEPRECATED] */
        ret = nfs_wb_folio(inode, folio);
        trace_nfs_launder_folio_done(inode, folio_pos(folio),
                        folio_size(folio), ret);
        return ret;
}

static int nfs_swap_activate(struct swap_info_struct *sis, struct file *file,
                                                sector_t *span)
{
        unsigned long blocks;
        long long isize;
        int ret;
        struct inode *inode = file_inode(file);
        struct rpc_clnt *clnt = NFS_CLIENT(inode);
        struct nfs_client *cl = NFS_SERVER(inode)->nfs_client;

        spin_lock(&inode->i_lock);
        blocks = inode->i_blocks;
        isize = inode->i_size;
        spin_unlock(&inode->i_lock);
        if (blocks*512 < isize) {
                pr_warn("swap activate: swapfile has holes\n");
                return -EINVAL;
        }

        ret = rpc_clnt_swap_activate(clnt);
        if (ret)
                return ret;
        ret = add_swap_extent(sis, 0, sis->max, 0);
        if (ret < 0) {
                rpc_clnt_swap_deactivate(clnt);
                return ret;
        }

        *span = sis->pages;

        if (cl->rpc_ops->enable_swap)
                cl->rpc_ops->enable_swap(inode);

        sis->flags |= SWP_FS_OPS;
        return ret;
}

static void nfs_swap_deactivate(struct file *file)
{
        struct inode *inode = file_inode(file);
        struct rpc_clnt *clnt = NFS_CLIENT(inode);
        struct nfs_client *cl = NFS_SERVER(inode)->nfs_client;

        rpc_clnt_swap_deactivate(clnt);
        if (cl->rpc_ops->disable_swap)
                cl->rpc_ops->disable_swap(file_inode(file));
}

const struct address_space_operations nfs_file_aops = {
        .read_folio = nfs_read_folio,
        .readahead = nfs_readahead,
        .dirty_folio = filemap_dirty_folio,
        .writepages = nfs_writepages,
        .write_begin = nfs_write_begin,
        .write_end = nfs_write_end,
        .invalidate_folio = nfs_invalidate_folio,
        .release_folio = nfs_release_folio,
        .migrate_folio = nfs_migrate_folio,
        .launder_folio = nfs_launder_folio,
        .is_dirty_writeback = nfs_check_dirty_writeback,
        .error_remove_folio = generic_error_remove_folio,
        .swap_activate = nfs_swap_activate,
        .swap_deactivate = nfs_swap_deactivate,
        .swap_rw = nfs_swap_rw,
};

/*
 * Notification that a PTE pointing to an NFS page is about to be made
 * writable, implying that someone is about to modify the page through a
 * shared-writable mapping
 */
static vm_fault_t nfs_vm_page_mkwrite(struct vm_fault *vmf)
{
        struct file *filp = vmf->vma->vm_file;
        struct inode *inode = file_inode(filp);
        unsigned pagelen;
        vm_fault_t ret = VM_FAULT_NOPAGE;
        struct address_space *mapping;
        struct folio *folio = page_folio(vmf->page);

        dfprintk(PAGECACHE, "NFS: vm_page_mkwrite(%pD2(%lu), offset %lld)\n",
                 filp, filp->f_mapping->host->i_ino,
                 (long long)folio_pos(folio));

        sb_start_pagefault(inode->i_sb);

        /* make sure the cache has finished storing the page */
        if (folio_test_private_2(folio) && /* [DEPRECATED] */
            folio_wait_private_2_killable(folio) < 0) {
                ret = VM_FAULT_RETRY;
                goto out;
        }

        wait_on_bit_action(&NFS_I(inode)->flags, NFS_INO_INVALIDATING,
                           nfs_wait_bit_killable,
                           TASK_KILLABLE|TASK_FREEZABLE_UNSAFE);

        folio_lock(folio);
        mapping = folio->mapping;
        if (mapping != inode->i_mapping)
                goto out_unlock;

        folio_wait_writeback(folio);

        pagelen = nfs_folio_length(folio);
        if (pagelen == 0)
                goto out_unlock;

        ret = VM_FAULT_LOCKED;
        if (nfs_flush_incompatible(filp, folio) == 0 &&
            nfs_update_folio(filp, folio, 0, pagelen) == 0)
                goto out;

        ret = VM_FAULT_SIGBUS;
out_unlock:
        folio_unlock(folio);
out:
        sb_end_pagefault(inode->i_sb);
        return ret;
}

static const struct vm_operations_struct nfs_file_vm_ops = {
        .fault = filemap_fault,
        .map_pages = filemap_map_pages,
        .page_mkwrite = nfs_vm_page_mkwrite,
};

ssize_t nfs_file_write(struct kiocb *iocb, struct iov_iter *from)
{
        struct file *file = iocb->ki_filp;
        struct inode *inode = file_inode(file);
        unsigned int mntflags = NFS_SERVER(inode)->flags;
        ssize_t result, written;
        errseq_t since;
        int error;

        trace_nfs_file_write(iocb, from);

        result = nfs_key_timeout_notify(file, inode);
        if (result)
                return result;

        if (iocb->ki_flags & IOCB_DIRECT)
                return nfs_file_direct_write(iocb, from, false);

        dprintk("NFS: write(%pD2, %zu@%Ld)\n",
                file, iov_iter_count(from), (long long) iocb->ki_pos);

        if (IS_SWAPFILE(inode))
                goto out_swapfile;
        /*
         * O_APPEND implies that we must revalidate the file length.
         */
        if (iocb->ki_flags & IOCB_APPEND || iocb->ki_pos > i_size_read(inode)) {
                result = nfs_revalidate_file_size(inode, file);
                if (result)
                        return result;
        }

        nfs_clear_invalid_mapping(file->f_mapping);

        since = filemap_sample_wb_err(file->f_mapping);
        error = nfs_start_io_write(inode);
        if (error)
                return error;
        result = generic_write_checks(iocb, from);
        if (result > 0)
                result = generic_perform_write(iocb, from);
        nfs_end_io_write(inode);
        if (result <= 0)
                goto out;

        written = result;
        nfs_add_stats(inode, NFSIOS_NORMALWRITTENBYTES, written);

        if (mntflags & NFS_MOUNT_WRITE_EAGER) {
                result = filemap_fdatawrite_range(file->f_mapping,
                                                  iocb->ki_pos - written,
                                                  iocb->ki_pos - 1);
                if (result < 0)
                        goto out;
        }
        if (mntflags & NFS_MOUNT_WRITE_WAIT) {
                filemap_fdatawait_range(file->f_mapping,
                                        iocb->ki_pos - written,
                                        iocb->ki_pos - 1);
        }
        result = generic_write_sync(iocb, written);
        if (result < 0)
                return result;

out:
        /* Return error values */
        error = filemap_check_wb_err(file->f_mapping, since);
        switch (error) {
        default:
                break;
        case -EDQUOT:
        case -EFBIG:
        case -ENOSPC:
                nfs_wb_all(inode);
                error = file_check_and_advance_wb_err(file);
                if (error < 0)
                        result = error;
        }
        return result;

out_swapfile:
        printk(KERN_INFO "NFS: attempt to write to active swap file!\n");
        return -ETXTBSY;
}
EXPORT_SYMBOL_GPL(nfs_file_write);

static int
do_getlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
{
        struct inode *inode = filp->f_mapping->host;
        int status = 0;
        unsigned int saved_type = fl->c.flc_type;

        /* Try local locking first */
        posix_test_lock(filp, fl);
        if (fl->c.flc_type != F_UNLCK) {
                /* found a conflict */
                goto out;
        }
        fl->c.flc_type = saved_type;

        if (nfs_have_read_or_write_delegation(inode))
                goto out_noconflict;

        if (is_local)
                goto out_noconflict;

        status = NFS_PROTO(inode)->lock(filp, cmd, fl);
out:
        return status;
out_noconflict:
        fl->c.flc_type = F_UNLCK;
        goto out;
}

static int
do_unlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
{
        struct inode *inode = filp->f_mapping->host;
        struct nfs_lock_context *l_ctx;
        int status;

        /*
         * Flush all pending writes before doing anything
         * with locks..
         */
        nfs_wb_all(inode);

        l_ctx = nfs_get_lock_context(nfs_file_open_context(filp));
        if (!IS_ERR(l_ctx)) {
                status = nfs_iocounter_wait(l_ctx);
                nfs_put_lock_context(l_ctx);
                /*  NOTE: special case
                 *      If we're signalled while cleaning up locks on process exit, we
                 *      still need to complete the unlock.
                 */
                if (status < 0 && !(fl->c.flc_flags & FL_CLOSE))
                        return status;
        }

        /*
         * Use local locking if mounted with "-onolock" or with appropriate
         * "-olocal_lock="
         */
        if (!is_local)
                status = NFS_PROTO(inode)->lock(filp, cmd, fl);
        else
                status = locks_lock_file_wait(filp, fl);
        return status;
}

static int
do_setlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
{
        struct inode *inode = filp->f_mapping->host;
        int status;

        /*
         * Flush all pending writes before doing anything
         * with locks..
         */
        status = nfs_sync_mapping(filp->f_mapping);
        if (status != 0)
                goto out;

        /*
         * Use local locking if mounted with "-onolock" or with appropriate
         * "-olocal_lock="
         */
        if (!is_local)
                status = NFS_PROTO(inode)->lock(filp, cmd, fl);
        else
                status = locks_lock_file_wait(filp, fl);
        if (status < 0)
                goto out;

        /*
         * Invalidate cache to prevent missing any changes.  If
         * the file is mapped, clear the page cache as well so
         * those mappings will be loaded.
         *
         * This makes locking act as a cache coherency point.
         */
        nfs_sync_mapping(filp->f_mapping);
        if (!nfs_have_read_or_write_delegation(inode)) {
                nfs_zap_caches(inode);
                if (mapping_mapped(filp->f_mapping))
                        nfs_revalidate_mapping(inode, filp->f_mapping);
        }
out:
        return status;
}

/*
 * Lock a (portion of) a file
 */
int nfs_lock(struct file *filp, int cmd, struct file_lock *fl)
{
        struct inode *inode = filp->f_mapping->host;
        int ret = -ENOLCK;
        int is_local = 0;

        dprintk("NFS: lock(%pD2, t=%x, fl=%x, r=%lld:%lld)\n",
                        filp, fl->c.flc_type, fl->c.flc_flags,
                        (long long)fl->fl_start, (long long)fl->fl_end);

        nfs_inc_stats(inode, NFSIOS_VFSLOCK);

        if (fl->c.flc_flags & FL_RECLAIM)
                return -ENOGRACE;

        if (NFS_SERVER(inode)->flags & NFS_MOUNT_LOCAL_FCNTL)
                is_local = 1;

        if (NFS_PROTO(inode)->lock_check_bounds != NULL) {
                ret = NFS_PROTO(inode)->lock_check_bounds(fl);
                if (ret < 0)
                        goto out_err;
        }

        if (IS_GETLK(cmd))
                ret = do_getlk(filp, cmd, fl, is_local);
        else if (lock_is_unlock(fl))
                ret = do_unlk(filp, cmd, fl, is_local);
        else
                ret = do_setlk(filp, cmd, fl, is_local);
out_err:
        return ret;
}
EXPORT_SYMBOL_GPL(nfs_lock);

/*
 * Lock a (portion of) a file
 */
int nfs_flock(struct file *filp, int cmd, struct file_lock *fl)
{
        struct inode *inode = filp->f_mapping->host;
        int is_local = 0;

        dprintk("NFS: flock(%pD2, t=%x, fl=%x)\n",
                        filp, fl->c.flc_type, fl->c.flc_flags);

        if (!(fl->c.flc_flags & FL_FLOCK))
                return -ENOLCK;

        if (NFS_SERVER(inode)->flags & NFS_MOUNT_LOCAL_FLOCK)
                is_local = 1;

        /* We're simulating flock() locks using posix locks on the server */
        if (lock_is_unlock(fl))
                return do_unlk(filp, cmd, fl, is_local);
        return do_setlk(filp, cmd, fl, is_local);
}
EXPORT_SYMBOL_GPL(nfs_flock);

const struct file_operations nfs_file_operations = {
        .llseek         = nfs_file_llseek,
        .read_iter      = nfs_file_read,
        .write_iter     = nfs_file_write,
        .mmap_prepare   = nfs_file_mmap_prepare,
        .open           = nfs_file_open,
        .flush          = nfs_file_flush,
        .release        = nfs_file_release,
        .fsync          = nfs_file_fsync,
        .lock           = nfs_lock,
        .flock          = nfs_flock,
        .splice_read    = nfs_file_splice_read,
        .splice_write   = iter_file_splice_write,
        .check_flags    = nfs_check_flags,
        .fop_flags      = FOP_DONTCACHE,
};
EXPORT_SYMBOL_GPL(nfs_file_operations);