file.c

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/*
 *  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 [email protected].
 *
 *  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/aio.h>
#include <linux/gfp.h>
#include <linux/swap.h>

#include <asm/uaccess.h>

#include "delegation.h"
#include "internal.h"
#include "iostat.h"
#include "fscache.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(%s/%s)\n",
            filp->f_path.dentry->d_parent->d_name.name,
            filp->f_path.dentry->d_name.name);

    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(%s/%s)\n",
            filp->f_path.dentry->d_parent->d_name.name,
            filp->f_path.dentry->d_name.name);

    nfs_inc_stats(inode, NFSIOS_VFSRELEASE);
    return nfs_release(inode, filp);
}
EXPORT_SYMBOL_GPL(nfs_file_release);

static int nfs_revalidate_file_size(struct inode *inode, struct file *filp)
{
    struct nfs_server *server = NFS_SERVER(inode);
    struct nfs_inode *nfsi = NFS_I(inode);

    if (nfs_have_delegated_attributes(inode))
        goto out_noreval;

    if (filp->f_flags & O_DIRECT)
        goto force_reval;
    if (nfsi->cache_validity & NFS_INO_REVAL_PAGECACHE)
        goto force_reval;
    if (nfs_attribute_timeout(inode))
        goto force_reval;
out_noreval:
    return 0;
force_reval:
    return __nfs_revalidate_inode(server, inode);
}

loff_t nfs_file_llseek(struct file *filp, loff_t offset, int origin)
{
    dprintk("NFS: llseek file(%s/%s, %lld, %d)\n",
            filp->f_path.dentry->d_parent->d_name.name,
            filp->f_path.dentry->d_name.name,
            offset, origin);

    /*
     * origin == SEEK_END || SEEK_DATA || SEEK_HOLE => we must revalidate
     * the cached file length
     */
    if (origin != SEEK_SET && origin != 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, origin);
}
EXPORT_SYMBOL_GPL(nfs_file_llseek);

/*
 * Flush all dirty pages, and check for write errors.
 */
int
nfs_file_flush(struct file *file, fl_owner_t id)
{
    struct dentry   *dentry = file->f_path.dentry;
    struct inode    *inode = dentry->d_inode;

    dprintk("NFS: flush(%s/%s)\n",
            dentry->d_parent->d_name.name,
            dentry->d_name.name);

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

    /*
     * If we're holding a write delegation, then just start the i/o
     * but don't wait for completion (or send a commit).
     */
    if (NFS_PROTO(inode)->have_delegation(inode, FMODE_WRITE))
        return filemap_fdatawrite(file->f_mapping);

    /* Flush writes to the server and return any errors */
    return vfs_fsync(file, 0);
}
EXPORT_SYMBOL_GPL(nfs_file_flush);

ssize_t
nfs_file_read(struct kiocb *iocb, const struct iovec *iov,
        unsigned long nr_segs, loff_t pos)
{
    struct dentry * dentry = iocb->ki_filp->f_path.dentry;
    struct inode * inode = dentry->d_inode;
    ssize_t result;

    if (iocb->ki_filp->f_flags & O_DIRECT)
        return nfs_file_direct_read(iocb, iov, nr_segs, pos, true);

    dprintk("NFS: read(%s/%s, %lu@%lu)\n",
        dentry->d_parent->d_name.name, dentry->d_name.name,
        (unsigned long) iov_length(iov, nr_segs), (unsigned long) pos);

    result = nfs_revalidate_mapping(inode, iocb->ki_filp->f_mapping);
    if (!result) {
        result = generic_file_aio_read(iocb, iov, nr_segs, pos);
        if (result > 0)
            nfs_add_stats(inode, NFSIOS_NORMALREADBYTES, result);
    }
    return result;
}
EXPORT_SYMBOL_GPL(nfs_file_read);

ssize_t
nfs_file_splice_read(struct file *filp, loff_t *ppos,
             struct pipe_inode_info *pipe, size_t count,
             unsigned int flags)
{
    struct dentry *dentry = filp->f_path.dentry;
    struct inode *inode = dentry->d_inode;
    ssize_t res;

    dprintk("NFS: splice_read(%s/%s, %lu@%Lu)\n",
        dentry->d_parent->d_name.name, dentry->d_name.name,
        (unsigned long) count, (unsigned long long) *ppos);

    res = nfs_revalidate_mapping(inode, filp->f_mapping);
    if (!res) {
        res = generic_file_splice_read(filp, ppos, pipe, count, flags);
        if (res > 0)
            nfs_add_stats(inode, NFSIOS_NORMALREADBYTES, res);
    }
    return res;
}
EXPORT_SYMBOL_GPL(nfs_file_splice_read);

int
nfs_file_mmap(struct file * file, struct vm_area_struct * vma)
{
    struct dentry *dentry = file->f_path.dentry;
    struct inode *inode = dentry->d_inode;
    int status;

    dprintk("NFS: mmap(%s/%s)\n",
        dentry->d_parent->d_name.name, dentry->d_name.name);

    /* 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.
 */
int
nfs_file_fsync_commit(struct file *file, loff_t start, loff_t end, int datasync)
{
    struct dentry *dentry = file->f_path.dentry;
    struct nfs_open_context *ctx = nfs_file_open_context(file);
    struct inode *inode = dentry->d_inode;
    int have_error, do_resend, status;
    int ret = 0;

    dprintk("NFS: fsync file(%s/%s) datasync %d\n",
            dentry->d_parent->d_name.name, dentry->d_name.name,
            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;
}
EXPORT_SYMBOL_GPL(nfs_file_fsync_commit);

static int
nfs_file_fsync(struct file *file, loff_t start, loff_t end, int datasync)
{
    int ret;
    struct inode *inode = file->f_path.dentry->d_inode;

    do {
        ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
        if (ret != 0)
            break;
        mutex_lock(&inode->i_mutex);
        ret = nfs_file_fsync_commit(file, start, end, datasync);
        mutex_unlock(&inode->i_mutex);
        /*
         * 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);

    return ret;
}

/*
 * 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_CACHE_SIZE - 1);
    unsigned int end = offset + len;

    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_CACHE_SHIFT;
    struct page *page;
    int once_thru = 0;

    dfprintk(PAGECACHE, "NFS: write_begin(%s/%s(%ld), %u@%lld)\n",
        file->f_path.dentry->d_parent->d_name.name,
        file->f_path.dentry->d_name.name,
        mapping->host->i_ino, len, (long long) pos);

start:
    /*
     * Prevent starvation issues if someone is doing a consistency
     * sync-to-disk
     */
    ret = wait_on_bit(&NFS_I(mapping->host)->flags, NFS_INO_FLUSHING,
            nfs_wait_bit_killable, TASK_KILLABLE);
    if (ret)
        return ret;

    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);
        page_cache_release(page);
    } else if (!once_thru &&
           nfs_want_read_modify_write(file, page, pos, len)) {
        once_thru = 1;
        ret = nfs_readpage(file, page);
        page_cache_release(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_CACHE_SIZE - 1);
    int status;

    dfprintk(PAGECACHE, "NFS: write_end(%s/%s(%ld), %u@%lld)\n",
        file->f_path.dentry->d_parent->d_name.name,
        file->f_path.dentry->d_name.name,
        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 + len;

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

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

    unlock_page(page);
    page_cache_release(page);

    if (status < 0)
        return status;
    NFS_I(mapping->host)->write_io += 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_page(struct page *page, unsigned long offset)
{
    dfprintk(PAGECACHE, "NFS: invalidate_page(%p, %lu)\n", page, offset);

    if (offset != 0)
        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)
{
    struct address_space *mapping = page->mapping;

    dfprintk(PAGECACHE, "NFS: release_page(%p)\n", page);

    /* Only do I/O if gfp is a superset of GFP_KERNEL, and we're not
     * doing this memory reclaim for a fs-related allocation.
     */
    if (mapping && (gfp & GFP_KERNEL) == GFP_KERNEL &&
        !(current->flags & PF_FSTRANS)) {
        int how = FLUSH_SYNC;

        /* Don't let kswapd deadlock waiting for OOM RPC calls */
        if (current_is_kswapd())
            how = 0;
        nfs_commit_inode(mapping->host, how);
    }
    /* If PagePrivate() is set, then the page is not freeable */
    if (PagePrivate(page))
        return 0;
    return nfs_fscache_release_page(page, gfp);
}

/*
 * 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_page(inode, page);
}

#ifdef CONFIG_NFS_SWAP
static int nfs_swap_activate(struct swap_info_struct *sis, struct file *file,
                        sector_t *span)
{
    *span = sis->pages;
    return xs_swapper(NFS_CLIENT(file->f_mapping->host)->cl_xprt, 1);
}

static void nfs_swap_deactivate(struct file *file)
{
    xs_swapper(NFS_CLIENT(file->f_mapping->host)->cl_xprt, 0);
}
#endif

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,
    .migratepage = nfs_migrate_page,
    .launder_page = nfs_launder_page,
    .error_remove_page = generic_error_remove_page,
#ifdef CONFIG_NFS_SWAP
    .swap_activate = nfs_swap_activate,
    .swap_deactivate = nfs_swap_deactivate,
#endif
};

/*
 * 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 dentry *dentry = filp->f_path.dentry;
    unsigned pagelen;
    int ret = VM_FAULT_NOPAGE;
    struct address_space *mapping;

    dfprintk(PAGECACHE, "NFS: vm_page_mkwrite(%s/%s(%ld), offset %lld)\n",
        dentry->d_parent->d_name.name, dentry->d_name.name,
        filp->f_mapping->host->i_ino,
        (long long)page_offset(page));

    /* make sure the cache has finished storing the page */
    nfs_fscache_wait_on_page_write(NFS_I(dentry->d_inode), page);

    lock_page(page);
    mapping = page_file_mapping(page);
    if (mapping != dentry->d_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:
    return ret;
}

static const struct vm_operations_struct nfs_file_vm_ops = {
    .fault = filemap_fault,
    .page_mkwrite = nfs_vm_page_mkwrite,
    .remap_pages = generic_file_remap_pages,
};

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

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

ssize_t nfs_file_write(struct kiocb *iocb, const struct iovec *iov,
               unsigned long nr_segs, loff_t pos)
{
    struct dentry * dentry = iocb->ki_filp->f_path.dentry;
    struct inode * inode = dentry->d_inode;
    unsigned long written = 0;
    ssize_t result;
    size_t count = iov_length(iov, nr_segs);

    if (iocb->ki_filp->f_flags & O_DIRECT)
        return nfs_file_direct_write(iocb, iov, nr_segs, pos, true);

    dprintk("NFS: write(%s/%s, %lu@%Ld)\n",
        dentry->d_parent->d_name.name, dentry->d_name.name,
        (unsigned long) count, (long long) pos);

    result = -EBUSY;
    if (IS_SWAPFILE(inode))
        goto out_swapfile;
    /*
     * O_APPEND implies that we must revalidate the file length.
     */
    if (iocb->ki_filp->f_flags & O_APPEND) {
        result = nfs_revalidate_file_size(inode, iocb->ki_filp);
        if (result)
            goto out;
    }

    result = count;
    if (!count)
        goto out;

    result = generic_file_aio_write(iocb, iov, nr_segs, pos);
    if (result > 0)
        written = result;

    /* Return error values for O_DSYNC and IS_SYNC() */
    if (result >= 0 && nfs_need_sync_write(iocb->ki_filp, inode)) {
        int err = vfs_fsync(iocb->ki_filp, 0);
        if (err < 0)
            result = err;
    }
    if (result > 0)
        nfs_add_stats(inode, NFSIOS_NORMALWRITTENBYTES, written);
out:
    return result;

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

ssize_t nfs_file_splice_write(struct pipe_inode_info *pipe,
                  struct file *filp, loff_t *ppos,
                  size_t count, unsigned int flags)
{
    struct dentry *dentry = filp->f_path.dentry;
    struct inode *inode = dentry->d_inode;
    unsigned long written = 0;
    ssize_t ret;

    dprintk("NFS splice_write(%s/%s, %lu@%llu)\n",
        dentry->d_parent->d_name.name, dentry->d_name.name,
        (unsigned long) count, (unsigned long long) *ppos);

    /*
     * The combination of splice and an O_APPEND destination is disallowed.
     */

    ret = generic_file_splice_write(pipe, filp, ppos, count, flags);
    if (ret > 0)
        written = ret;

    if (ret >= 0 && nfs_need_sync_write(filp, inode)) {
        int err = vfs_fsync(filp, 0);
        if (err < 0)
            ret = err;
    }
    if (ret > 0)
        nfs_add_stats(inode, NFSIOS_NORMALWRITTENBYTES, written);
    return ret;
}
EXPORT_SYMBOL_GPL(nfs_file_splice_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_vfs_lock(struct file *file, struct file_lock *fl)
{
    int res = 0;
    switch (fl->fl_flags & (FL_POSIX|FL_FLOCK)) {
        case FL_POSIX:
            res = posix_lock_file_wait(file, fl);
            break;
        case FL_FLOCK:
            res = flock_lock_file_wait(file, fl);
            break;
        default:
            BUG();
    }
    return res;
}

static int
do_unlk(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..
     */
    nfs_sync_mapping(filp->f_mapping);

    /* 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 = do_vfs_lock(filp, fl);
    return status;
}

static int
is_time_granular(struct timespec *ts) {
    return ((ts->tv_sec == 0) && (ts->tv_nsec <= 1000));
}

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 = do_vfs_lock(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)) {
        if (is_time_granular(&NFS_SERVER(inode)->time_delta))
            __nfs_revalidate_inode(NFS_SERVER(inode), inode);
        else
            nfs_zap_caches(inode);
    }
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(%s/%s, t=%x, fl=%x, r=%lld:%lld)\n",
            filp->f_path.dentry->d_parent->d_name.name,
            filp->f_path.dentry->d_name.name,
            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(%s/%s, t=%x, fl=%x)\n",
            filp->f_path.dentry->d_parent->d_name.name,
            filp->f_path.dentry->d_name.name,
            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 */
    fl->fl_owner = (fl_owner_t)filp;
    fl->fl_start = 0;
    fl->fl_end = OFFSET_MAX;

    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);

/*
 * There is no protocol support for leases, so we have no way to implement
 * them correctly in the face of opens by other clients.
 */
int nfs_setlease(struct file *file, long arg, struct file_lock **fl)
{
    dprintk("NFS: setlease(%s/%s, arg=%ld)\n",
            file->f_path.dentry->d_parent->d_name.name,
            file->f_path.dentry->d_name.name, arg);
    return -EINVAL;
}
EXPORT_SYMBOL_GPL(nfs_setlease);

const struct file_operations nfs_file_operations = {
    .llseek     = nfs_file_llseek,
    .read       = do_sync_read,
    .write      = do_sync_write,
    .aio_read   = nfs_file_read,
    .aio_write  = 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    = nfs_file_splice_read,
    .splice_write   = nfs_file_splice_write,
    .check_flags    = nfs_check_flags,
    .setlease   = nfs_setlease,
};
EXPORT_SYMBOL_GPL(nfs_file_operations);