/*
 *  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/swap.h>

#include <linux/uaccess.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;

/* Hack for future NFS swap support */
#ifndef IS_SWAPFILE
# define IS_SWAPFILE(inode)     (0)
#endif

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);
        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);
        return 0;
}
EXPORT_SYMBOL_GPL(nfs_file_release);

/**
 * nfs_revalidate_size - Revalidate the file size
 * @inode - pointer to inode struct
 * @file - 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_REVAL_PAGECACHE))
                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);

        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 */
        return vfs_fsync(file, 0);
}

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

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

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

        nfs_start_io_read(inode);
        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);

int
nfs_file_mmap(struct file * file, struct vm_area_struct * vma)
{
        struct inode *inode = file_inode(file);
        int     status;

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

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

/*
 * 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.
 *
 * Notice that it clears the NFS_CONTEXT_ERROR_WRITE before synching to
 * disk, but it retrieves and clears ctx->error after synching, despite
 * the two being set at the same time in nfs_context_set_write_error().
 * This is because the former is used to notify the _next_ call to
 * nfs_file_write() that a write error occurred, and hence cause it to
 * fall back to doing a synchronous write.
 */
static int
nfs_file_fsync_commit(struct file *file, loff_t start, loff_t end, int datasync)
{
        struct nfs_open_context *ctx = nfs_file_open_context(file);
        struct inode *inode = file_inode(file);
        int have_error, do_resend, status;
        int ret = 0;

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

        nfs_inc_stats(inode, NFSIOS_VFSFSYNC);
        do_resend = test_and_clear_bit(NFS_CONTEXT_RESEND_WRITES, &ctx->flags);
        have_error = test_and_clear_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags);
        status = nfs_commit_inode(inode, FLUSH_SYNC);
        have_error |= test_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags);
        if (have_error) {
                ret = xchg(&ctx->error, 0);
                if (ret)
                        goto out;
        }
        if (status < 0) {
                ret = status;
                goto out;
        }
        do_resend |= test_bit(NFS_CONTEXT_RESEND_WRITES, &ctx->flags);
        if (do_resend)
                ret = -EAGAIN;
out:
        return ret;
}

int
nfs_file_fsync(struct file *file, loff_t start, loff_t end, int datasync)
{
        int ret;
        struct inode *inode = file_inode(file);

        trace_nfs_fsync_enter(inode);

        do {
                ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
                if (ret != 0)
                        break;
                ret = nfs_file_fsync_commit(file, start, end, datasync);
                if (!ret)
                        ret = pnfs_sync_inode(inode, !!datasync);
                /*
                 * If nfs_file_fsync_commit detected a server reboot, then
                 * resend all dirty pages that might have been covered by
                 * the NFS_CONTEXT_RESEND_WRITES flag
                 */
                start = 0;
                end = LLONG_MAX;
        } while (ret == -EAGAIN);

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

/*
 * 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.
 *
 * 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 int nfs_want_read_modify_write(struct file *file, struct page *page,
                        loff_t pos, unsigned len)
{
        unsigned int pglen = nfs_page_length(page);
        unsigned int offset = pos & (PAGE_SIZE - 1);
        unsigned int end = offset + len;

        if (pnfs_ld_read_whole_page(file->f_mapping->host)) {
                if (!PageUptodate(page))
                        return 1;
                return 0;
        }

        if ((file->f_mode & FMODE_READ) &&      /* open for read? */
            !PageUptodate(page) &&              /* Uptodate? */
            !PagePrivate(page) &&               /* i/o request already? */
            pglen &&                            /* valid bytes of file? */
            (end < pglen || offset))            /* replace all valid bytes? */
                return 1;
        return 0;
}

/*
 * 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(struct file *file, struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned flags,
                        struct page **pagep, void **fsdata)
{
        int ret;
        pgoff_t index = pos >> PAGE_SHIFT;
        struct page *page;
        int once_thru = 0;

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

start:
        page = grab_cache_page_write_begin(mapping, index, flags);
        if (!page)
                return -ENOMEM;
        *pagep = page;

        ret = nfs_flush_incompatible(file, page);
        if (ret) {
                unlock_page(page);
                put_page(page);
        } else if (!once_thru &&
                   nfs_want_read_modify_write(file, page, pos, len)) {
                once_thru = 1;
                ret = nfs_readpage(file, page);
                put_page(page);
                if (!ret)
                        goto start;
        }
        return ret;
}

static int nfs_write_end(struct file *file, struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned copied,
                        struct page *page, void *fsdata)
{
        unsigned offset = pos & (PAGE_SIZE - 1);
        struct nfs_open_context *ctx = nfs_file_open_context(file);
        int status;

        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 (!PageUptodate(page)) {
                unsigned pglen = nfs_page_length(page);
                unsigned end = offset + copied;

                if (pglen == 0) {
                        zero_user_segments(page, 0, offset,
                                        end, PAGE_SIZE);
                        SetPageUptodate(page);
                } else if (end >= pglen) {
                        zero_user_segment(page, end, PAGE_SIZE);
                        if (offset == 0)
                                SetPageUptodate(page);
                } else
                        zero_user_segment(page, pglen, PAGE_SIZE);
        }

        status = nfs_updatepage(file, page, offset, copied);

        unlock_page(page);
        put_page(page);

        if (status < 0)
                return status;
        NFS_I(mapping->host)->write_io += copied;

        if (nfs_ctx_key_to_expire(ctx, mapping->host)) {
                status = nfs_wb_all(mapping->host);
                if (status < 0)
                        return status;
        }

        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_page(struct page *page, unsigned int offset,
                                unsigned int length)
{
        dfprintk(PAGECACHE, "NFS: invalidate_page(%p, %u, %u)\n",
                 page, offset, length);

        if (offset != 0 || length < PAGE_SIZE)
                return;
        /* Cancel any unstarted writes on this page */
        nfs_wb_page_cancel(page_file_mapping(page)->host, page);

        nfs_fscache_invalidate_page(page, page->mapping->host);
}

/*
 * Attempt to release the private state associated with a page
 * - Called if either PG_private or PG_fscache is set on the page
 * - Caller holds page lock
 * - Return true (may release page) or false (may not)
 */
static int nfs_release_page(struct page *page, gfp_t gfp)
{
        dfprintk(PAGECACHE, "NFS: release_page(%p)\n", page);

        /* If PagePrivate() is set, then the page is not freeable */
        if (PagePrivate(page))
                return 0;
        return nfs_fscache_release_page(page, gfp);
}

static void nfs_check_dirty_writeback(struct page *page,
                                bool *dirty, bool *writeback)
{
        struct nfs_inode *nfsi;
        struct address_space *mapping = page_file_mapping(page);

        if (!mapping || PageSwapCache(page))
                return;

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

        /*
         * If PagePrivate() is set, then the page 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 (PagePrivate(page))
                *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_page(struct page *page)
{
        struct inode *inode = page_file_mapping(page)->host;
        struct nfs_inode *nfsi = NFS_I(inode);

        dfprintk(PAGECACHE, "NFS: launder_page(%ld, %llu)\n",
                inode->i_ino, (long long)page_offset(page));

        nfs_fscache_wait_on_page_write(nfsi, page);
        return nfs_wb_launder_page(inode, page);
}

static int nfs_swap_activate(struct swap_info_struct *sis, struct file *file,
                                                sector_t *span)
{
        struct rpc_clnt *clnt = NFS_CLIENT(file->f_mapping->host);

        *span = sis->pages;

        return rpc_clnt_swap_activate(clnt);
}

static void nfs_swap_deactivate(struct file *file)
{
        struct rpc_clnt *clnt = NFS_CLIENT(file->f_mapping->host);

        rpc_clnt_swap_deactivate(clnt);
}

const struct address_space_operations nfs_file_aops = {
        .readpage = nfs_readpage,
        .readpages = nfs_readpages,
        .set_page_dirty = __set_page_dirty_nobuffers,
        .writepage = nfs_writepage,
        .writepages = nfs_writepages,
        .write_begin = nfs_write_begin,
        .write_end = nfs_write_end,
        .invalidatepage = nfs_invalidate_page,
        .releasepage = nfs_release_page,
        .direct_IO = nfs_direct_IO,
#ifdef CONFIG_MIGRATION
        .migratepage = nfs_migrate_page,
#endif
        .launder_page = nfs_launder_page,
        .is_dirty_writeback = nfs_check_dirty_writeback,
        .error_remove_page = generic_error_remove_page,
        .swap_activate = nfs_swap_activate,
        .swap_deactivate = nfs_swap_deactivate,
};

/*
 * 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 int nfs_vm_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
{
        struct page *page = vmf->page;
        struct file *filp = vma->vm_file;
        struct inode *inode = file_inode(filp);
        unsigned pagelen;
        int ret = VM_FAULT_NOPAGE;
        struct address_space *mapping;

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

        sb_start_pagefault(inode->i_sb);

        /* make sure the cache has finished storing the page */
        nfs_fscache_wait_on_page_write(NFS_I(inode), page);

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

        lock_page(page);
        mapping = page_file_mapping(page);
        if (mapping != inode->i_mapping)
                goto out_unlock;

        wait_on_page_writeback(page);

        pagelen = nfs_page_length(page);
        if (pagelen == 0)
                goto out_unlock;

        ret = VM_FAULT_LOCKED;
        if (nfs_flush_incompatible(filp, page) == 0 &&
            nfs_updatepage(filp, page, 0, pagelen) == 0)
                goto out;

        ret = VM_FAULT_SIGBUS;
out_unlock:
        unlock_page(page);
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,
};

static int nfs_need_check_write(struct file *filp, struct inode *inode)
{
        struct nfs_open_context *ctx;

        ctx = nfs_file_open_context(filp);
        if (test_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags) ||
            nfs_ctx_key_to_expire(ctx, inode))
                return 1;
        return 0;
}

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 long written = 0;
        ssize_t result;

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

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

        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) {
                result = nfs_revalidate_file_size(inode, file);
                if (result)
                        goto out;
        }

        nfs_start_io_write(inode);
        result = generic_write_checks(iocb, from);
        if (result > 0) {
                current->backing_dev_info = inode_to_bdi(inode);
                result = generic_perform_write(file, from, iocb->ki_pos);
                current->backing_dev_info = NULL;
        }
        nfs_end_io_write(inode);
        if (result <= 0)
                goto out;

        result = generic_write_sync(iocb, result);
        if (result < 0)
                goto out;
        written = result;
        iocb->ki_pos += written;

        /* Return error values */
        if (nfs_need_check_write(file, inode)) {
                int err = vfs_fsync(file, 0);
                if (err < 0)
                        result = err;
        }
        nfs_add_stats(inode, NFSIOS_NORMALWRITTENBYTES, written);
out:
        return result;

out_swapfile:
        printk(KERN_INFO "NFS: attempt to write to active swap file!\n");
        return -EBUSY;
}
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->fl_type;

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

        if (NFS_PROTO(inode)->have_delegation(inode, FMODE_READ))
                goto out_noconflict;

        if (is_local)
                goto out_noconflict;

        status = NFS_PROTO(inode)->lock(filp, cmd, fl);
out:
        return status;
out_noconflict:
        fl->fl_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..
         */
        vfs_fsync(filp, 0);

        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);
                if (status < 0)
                        return status;
        }

        /* NOTE: special case
         *      If we're signalled while cleaning up locks on process exit, we
         *      still need to complete the unlock.
         */
        /*
         * 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;

        /*
         * Revalidate the cache if the server has time stamps granular
         * enough to detect subsecond changes.  Otherwise, clear the
         * cache to prevent missing any changes.
         *
         * This makes locking act as a cache coherency point.
         */
        nfs_sync_mapping(filp->f_mapping);
        if (!NFS_PROTO(inode)->have_delegation(inode, FMODE_READ))
                nfs_zap_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->fl_type, fl->fl_flags,
                        (long long)fl->fl_start, (long long)fl->fl_end);

        nfs_inc_stats(inode, NFSIOS_VFSLOCK);

        /* No mandatory locks over NFS */
        if (__mandatory_lock(inode) && fl->fl_type != F_UNLCK)
                goto out_err;

        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 (fl->fl_type == F_UNLCK)
                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->fl_type, fl->fl_flags);

        if (!(fl->fl_flags & FL_FLOCK))
                return -ENOLCK;

        /*
         * The NFSv4 protocol doesn't support LOCK_MAND, which is not part of
         * any standard. In principle we might be able to support LOCK_MAND
         * on NFSv2/3 since NLMv3/4 support DOS share modes, but for now the
         * NFS code is not set up for it.
         */
        if (fl->fl_type & LOCK_MAND)
                return -EINVAL;

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

        /* We're simulating flock() locks using posix locks on the server */
        if (fl->fl_type == F_UNLCK)
                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           = nfs_file_mmap,
        .open           = nfs_file_open,
        .flush          = nfs_file_flush,
        .release        = nfs_file_release,
        .fsync          = nfs_file_fsync,
        .lock           = nfs_lock,
        .flock          = nfs_flock,
        .splice_read    = generic_file_splice_read,
        .splice_write   = iter_file_splice_write,
        .check_flags    = nfs_check_flags,
        .setlease       = simple_nosetlease,
};
EXPORT_SYMBOL_GPL(nfs_file_operations);