xfs_file.c

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/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_log.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_trans.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_inode_item.h"
#include "xfs_bmap.h"
#include "xfs_error.h"
#include "xfs_vnodeops.h"
#include "xfs_da_btree.h"
#include "xfs_ioctl.h"
#include "xfs_trace.h"

#include <linux/dcache.h>
#include <linux/falloc.h>
#include <linux/pagevec.h>

static const struct vm_operations_struct xfs_file_vm_ops;

/*
 * Locking primitives for read and write IO paths to ensure we consistently use
 * and order the inode->i_mutex, ip->i_lock and ip->i_iolock.
 */
static inline void
xfs_rw_ilock(
    struct xfs_inode    *ip,
    int         type)
{
    if (type & XFS_IOLOCK_EXCL)
        mutex_lock(&VFS_I(ip)->i_mutex);
    xfs_ilock(ip, type);
}

static inline void
xfs_rw_iunlock(
    struct xfs_inode    *ip,
    int         type)
{
    xfs_iunlock(ip, type);
    if (type & XFS_IOLOCK_EXCL)
        mutex_unlock(&VFS_I(ip)->i_mutex);
}

static inline void
xfs_rw_ilock_demote(
    struct xfs_inode    *ip,
    int         type)
{
    xfs_ilock_demote(ip, type);
    if (type & XFS_IOLOCK_EXCL)
        mutex_unlock(&VFS_I(ip)->i_mutex);
}

/*
 *  xfs_iozero
 *
 *  xfs_iozero clears the specified range of buffer supplied,
 *  and marks all the affected blocks as valid and modified.  If
 *  an affected block is not allocated, it will be allocated.  If
 *  an affected block is not completely overwritten, and is not
 *  valid before the operation, it will be read from disk before
 *  being partially zeroed.
 */
STATIC int
xfs_iozero(
    struct xfs_inode    *ip,    /* inode            */
    loff_t          pos,    /* offset in file       */
    size_t          count)  /* size of data to zero     */
{
    struct page     *page;
    struct address_space    *mapping;
    int         status;

    mapping = VFS_I(ip)->i_mapping;
    do {
        unsigned offset, bytes;
        void *fsdata;

        offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
        bytes = PAGE_CACHE_SIZE - offset;
        if (bytes > count)
            bytes = count;

        status = pagecache_write_begin(NULL, mapping, pos, bytes,
                    AOP_FLAG_UNINTERRUPTIBLE,
                    &page, &fsdata);
        if (status)
            break;

        zero_user(page, offset, bytes);

        status = pagecache_write_end(NULL, mapping, pos, bytes, bytes,
                    page, fsdata);
        WARN_ON(status <= 0); /* can't return less than zero! */
        pos += bytes;
        count -= bytes;
        status = 0;
    } while (count);

    return (-status);
}

/*
 * Fsync operations on directories are much simpler than on regular files,
 * as there is no file data to flush, and thus also no need for explicit
 * cache flush operations, and there are no non-transaction metadata updates
 * on directories either.
 */
STATIC int
xfs_dir_fsync(
    struct file     *file,
    loff_t          start,
    loff_t          end,
    int         datasync)
{
    struct xfs_inode    *ip = XFS_I(file->f_mapping->host);
    struct xfs_mount    *mp = ip->i_mount;
    xfs_lsn_t       lsn = 0;

    trace_xfs_dir_fsync(ip);

    xfs_ilock(ip, XFS_ILOCK_SHARED);
    if (xfs_ipincount(ip))
        lsn = ip->i_itemp->ili_last_lsn;
    xfs_iunlock(ip, XFS_ILOCK_SHARED);

    if (!lsn)
        return 0;
    return _xfs_log_force_lsn(mp, lsn, XFS_LOG_SYNC, NULL);
}

STATIC int
xfs_file_fsync(
    struct file     *file,
    loff_t          start,
    loff_t          end,
    int         datasync)
{
    struct inode        *inode = file->f_mapping->host;
    struct xfs_inode    *ip = XFS_I(inode);
    struct xfs_mount    *mp = ip->i_mount;
    int         error = 0;
    int         log_flushed = 0;
    xfs_lsn_t       lsn = 0;

    trace_xfs_file_fsync(ip);

    error = filemap_write_and_wait_range(inode->i_mapping, start, end);
    if (error)
        return error;

    if (XFS_FORCED_SHUTDOWN(mp))
        return -XFS_ERROR(EIO);

    xfs_iflags_clear(ip, XFS_ITRUNCATED);

    if (mp->m_flags & XFS_MOUNT_BARRIER) {
        /*
         * If we have an RT and/or log subvolume we need to make sure
         * to flush the write cache the device used for file data
         * first.  This is to ensure newly written file data make
         * it to disk before logging the new inode size in case of
         * an extending write.
         */
        if (XFS_IS_REALTIME_INODE(ip))
            xfs_blkdev_issue_flush(mp->m_rtdev_targp);
        else if (mp->m_logdev_targp != mp->m_ddev_targp)
            xfs_blkdev_issue_flush(mp->m_ddev_targp);
    }

    /*
     * All metadata updates are logged, which means that we just have
     * to flush the log up to the latest LSN that touched the inode.
     */
    xfs_ilock(ip, XFS_ILOCK_SHARED);
    if (xfs_ipincount(ip)) {
        if (!datasync ||
            (ip->i_itemp->ili_fields & ~XFS_ILOG_TIMESTAMP))
            lsn = ip->i_itemp->ili_last_lsn;
    }
    xfs_iunlock(ip, XFS_ILOCK_SHARED);

    if (lsn)
        error = _xfs_log_force_lsn(mp, lsn, XFS_LOG_SYNC, &log_flushed);

    /*
     * If we only have a single device, and the log force about was
     * a no-op we might have to flush the data device cache here.
     * This can only happen for fdatasync/O_DSYNC if we were overwriting
     * an already allocated file and thus do not have any metadata to
     * commit.
     */
    if ((mp->m_flags & XFS_MOUNT_BARRIER) &&
        mp->m_logdev_targp == mp->m_ddev_targp &&
        !XFS_IS_REALTIME_INODE(ip) &&
        !log_flushed)
        xfs_blkdev_issue_flush(mp->m_ddev_targp);

    return -error;
}

STATIC ssize_t
xfs_file_aio_read(
    struct kiocb        *iocb,
    const struct iovec  *iovp,
    unsigned long       nr_segs,
    loff_t          pos)
{
    struct file     *file = iocb->ki_filp;
    struct inode        *inode = file->f_mapping->host;
    struct xfs_inode    *ip = XFS_I(inode);
    struct xfs_mount    *mp = ip->i_mount;
    size_t          size = 0;
    ssize_t         ret = 0;
    int         ioflags = 0;
    xfs_fsize_t     n;

    XFS_STATS_INC(xs_read_calls);

    BUG_ON(iocb->ki_pos != pos);

    if (unlikely(file->f_flags & O_DIRECT))
        ioflags |= IO_ISDIRECT;
    if (file->f_mode & FMODE_NOCMTIME)
        ioflags |= IO_INVIS;

    ret = generic_segment_checks(iovp, &nr_segs, &size, VERIFY_WRITE);
    if (ret < 0)
        return ret;

    if (unlikely(ioflags & IO_ISDIRECT)) {
        xfs_buftarg_t   *target =
            XFS_IS_REALTIME_INODE(ip) ?
                mp->m_rtdev_targp : mp->m_ddev_targp;
        if ((iocb->ki_pos & target->bt_smask) ||
            (size & target->bt_smask)) {
            if (iocb->ki_pos == i_size_read(inode))
                return 0;
            return -XFS_ERROR(EINVAL);
        }
    }

    n = mp->m_super->s_maxbytes - iocb->ki_pos;
    if (n <= 0 || size == 0)
        return 0;

    if (n < size)
        size = n;

    if (XFS_FORCED_SHUTDOWN(mp))
        return -EIO;

    /*
     * Locking is a bit tricky here. If we take an exclusive lock
     * for direct IO, we effectively serialise all new concurrent
     * read IO to this file and block it behind IO that is currently in
     * progress because IO in progress holds the IO lock shared. We only
     * need to hold the lock exclusive to blow away the page cache, so
     * only take lock exclusively if the page cache needs invalidation.
     * This allows the normal direct IO case of no page cache pages to
     * proceeed concurrently without serialisation.
     */
    xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
    if ((ioflags & IO_ISDIRECT) && inode->i_mapping->nrpages) {
        xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
        xfs_rw_ilock(ip, XFS_IOLOCK_EXCL);

        if (inode->i_mapping->nrpages) {
            ret = -xfs_flushinval_pages(ip,
                    (iocb->ki_pos & PAGE_CACHE_MASK),
                    -1, FI_REMAPF_LOCKED);
            if (ret) {
                xfs_rw_iunlock(ip, XFS_IOLOCK_EXCL);
                return ret;
            }
        }
        xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL);
    }

    trace_xfs_file_read(ip, size, iocb->ki_pos, ioflags);

    ret = generic_file_aio_read(iocb, iovp, nr_segs, iocb->ki_pos);
    if (ret > 0)
        XFS_STATS_ADD(xs_read_bytes, ret);

    xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
    return ret;
}

STATIC ssize_t
xfs_file_splice_read(
    struct file     *infilp,
    loff_t          *ppos,
    struct pipe_inode_info  *pipe,
    size_t          count,
    unsigned int        flags)
{
    struct xfs_inode    *ip = XFS_I(infilp->f_mapping->host);
    int         ioflags = 0;
    ssize_t         ret;

    XFS_STATS_INC(xs_read_calls);

    if (infilp->f_mode & FMODE_NOCMTIME)
        ioflags |= IO_INVIS;

    if (XFS_FORCED_SHUTDOWN(ip->i_mount))
        return -EIO;

    xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);

    trace_xfs_file_splice_read(ip, count, *ppos, ioflags);

    ret = generic_file_splice_read(infilp, ppos, pipe, count, flags);
    if (ret > 0)
        XFS_STATS_ADD(xs_read_bytes, ret);

    xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
    return ret;
}

/*
 * xfs_file_splice_write() does not use xfs_rw_ilock() because
 * generic_file_splice_write() takes the i_mutex itself. This, in theory,
 * couuld cause lock inversions between the aio_write path and the splice path
 * if someone is doing concurrent splice(2) based writes and write(2) based
 * writes to the same inode. The only real way to fix this is to re-implement
 * the generic code here with correct locking orders.
 */
STATIC ssize_t
xfs_file_splice_write(
    struct pipe_inode_info  *pipe,
    struct file     *outfilp,
    loff_t          *ppos,
    size_t          count,
    unsigned int        flags)
{
    struct inode        *inode = outfilp->f_mapping->host;
    struct xfs_inode    *ip = XFS_I(inode);
    int         ioflags = 0;
    ssize_t         ret;

    XFS_STATS_INC(xs_write_calls);

    if (outfilp->f_mode & FMODE_NOCMTIME)
        ioflags |= IO_INVIS;

    if (XFS_FORCED_SHUTDOWN(ip->i_mount))
        return -EIO;

    xfs_ilock(ip, XFS_IOLOCK_EXCL);

    trace_xfs_file_splice_write(ip, count, *ppos, ioflags);

    ret = generic_file_splice_write(pipe, outfilp, ppos, count, flags);
    if (ret > 0)
        XFS_STATS_ADD(xs_write_bytes, ret);

    xfs_iunlock(ip, XFS_IOLOCK_EXCL);
    return ret;
}

/*
 * This routine is called to handle zeroing any space in the last block of the
 * file that is beyond the EOF.  We do this since the size is being increased
 * without writing anything to that block and we don't want to read the
 * garbage on the disk.
 */
STATIC int              /* error (positive) */
xfs_zero_last_block(
    struct xfs_inode    *ip,
    xfs_fsize_t     offset,
    xfs_fsize_t     isize)
{
    struct xfs_mount    *mp = ip->i_mount;
    xfs_fileoff_t       last_fsb = XFS_B_TO_FSBT(mp, isize);
    int         zero_offset = XFS_B_FSB_OFFSET(mp, isize);
    int         zero_len;
    int         nimaps = 1;
    int         error = 0;
    struct xfs_bmbt_irec    imap;

    xfs_ilock(ip, XFS_ILOCK_EXCL);
    error = xfs_bmapi_read(ip, last_fsb, 1, &imap, &nimaps, 0);
    xfs_iunlock(ip, XFS_ILOCK_EXCL);
    if (error)
        return error;

    ASSERT(nimaps > 0);

    /*
     * If the block underlying isize is just a hole, then there
     * is nothing to zero.
     */
    if (imap.br_startblock == HOLESTARTBLOCK)
        return 0;

    zero_len = mp->m_sb.sb_blocksize - zero_offset;
    if (isize + zero_len > offset)
        zero_len = offset - isize;
    return xfs_iozero(ip, isize, zero_len);
}

/*
 * Zero any on disk space between the current EOF and the new, larger EOF.
 *
 * This handles the normal case of zeroing the remainder of the last block in
 * the file and the unusual case of zeroing blocks out beyond the size of the
 * file.  This second case only happens with fixed size extents and when the
 * system crashes before the inode size was updated but after blocks were
 * allocated.
 *
 * Expects the iolock to be held exclusive, and will take the ilock internally.
 */
int                 /* error (positive) */
xfs_zero_eof(
    struct xfs_inode    *ip,
    xfs_off_t       offset,     /* starting I/O offset */
    xfs_fsize_t     isize)      /* current inode size */
{
    struct xfs_mount    *mp = ip->i_mount;
    xfs_fileoff_t       start_zero_fsb;
    xfs_fileoff_t       end_zero_fsb;
    xfs_fileoff_t       zero_count_fsb;
    xfs_fileoff_t       last_fsb;
    xfs_fileoff_t       zero_off;
    xfs_fsize_t     zero_len;
    int         nimaps;
    int         error = 0;
    struct xfs_bmbt_irec    imap;

    ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
    ASSERT(offset > isize);

    /*
     * First handle zeroing the block on which isize resides.
     *
     * We only zero a part of that block so it is handled specially.
     */
    if (XFS_B_FSB_OFFSET(mp, isize) != 0) {
        error = xfs_zero_last_block(ip, offset, isize);
        if (error)
            return error;
    }

    /*
     * Calculate the range between the new size and the old where blocks
     * needing to be zeroed may exist.
     *
     * To get the block where the last byte in the file currently resides,
     * we need to subtract one from the size and truncate back to a block
     * boundary.  We subtract 1 in case the size is exactly on a block
     * boundary.
     */
    last_fsb = isize ? XFS_B_TO_FSBT(mp, isize - 1) : (xfs_fileoff_t)-1;
    start_zero_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)isize);
    end_zero_fsb = XFS_B_TO_FSBT(mp, offset - 1);
    ASSERT((xfs_sfiloff_t)last_fsb < (xfs_sfiloff_t)start_zero_fsb);
    if (last_fsb == end_zero_fsb) {
        /*
         * The size was only incremented on its last block.
         * We took care of that above, so just return.
         */
        return 0;
    }

    ASSERT(start_zero_fsb <= end_zero_fsb);
    while (start_zero_fsb <= end_zero_fsb) {
        nimaps = 1;
        zero_count_fsb = end_zero_fsb - start_zero_fsb + 1;

        xfs_ilock(ip, XFS_ILOCK_EXCL);
        error = xfs_bmapi_read(ip, start_zero_fsb, zero_count_fsb,
                      &imap, &nimaps, 0);
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        if (error)
            return error;

        ASSERT(nimaps > 0);

        if (imap.br_state == XFS_EXT_UNWRITTEN ||
            imap.br_startblock == HOLESTARTBLOCK) {
            start_zero_fsb = imap.br_startoff + imap.br_blockcount;
            ASSERT(start_zero_fsb <= (end_zero_fsb + 1));
            continue;
        }

        /*
         * There are blocks we need to zero.
         */
        zero_off = XFS_FSB_TO_B(mp, start_zero_fsb);
        zero_len = XFS_FSB_TO_B(mp, imap.br_blockcount);

        if ((zero_off + zero_len) > offset)
            zero_len = offset - zero_off;

        error = xfs_iozero(ip, zero_off, zero_len);
        if (error)
            return error;

        start_zero_fsb = imap.br_startoff + imap.br_blockcount;
        ASSERT(start_zero_fsb <= (end_zero_fsb + 1));
    }

    return 0;
}

/*
 * Common pre-write limit and setup checks.
 *
 * Called with the iolocked held either shared and exclusive according to
 * @iolock, and returns with it held.  Might upgrade the iolock to exclusive
 * if called for a direct write beyond i_size.
 */
STATIC ssize_t
xfs_file_aio_write_checks(
    struct file     *file,
    loff_t          *pos,
    size_t          *count,
    int         *iolock)
{
    struct inode        *inode = file->f_mapping->host;
    struct xfs_inode    *ip = XFS_I(inode);
    int         error = 0;

restart:
    error = generic_write_checks(file, pos, count, S_ISBLK(inode->i_mode));
    if (error)
        return error;

    /*
     * If the offset is beyond the size of the file, we need to zero any
     * blocks that fall between the existing EOF and the start of this
     * write.  If zeroing is needed and we are currently holding the
     * iolock shared, we need to update it to exclusive which implies
     * having to redo all checks before.
     */
    if (*pos > i_size_read(inode)) {
        if (*iolock == XFS_IOLOCK_SHARED) {
            xfs_rw_iunlock(ip, *iolock);
            *iolock = XFS_IOLOCK_EXCL;
            xfs_rw_ilock(ip, *iolock);
            goto restart;
        }
        error = -xfs_zero_eof(ip, *pos, i_size_read(inode));
        if (error)
            return error;
    }

    /*
     * Updating the timestamps will grab the ilock again from
     * xfs_fs_dirty_inode, so we have to call it after dropping the
     * lock above.  Eventually we should look into a way to avoid
     * the pointless lock roundtrip.
     */
    if (likely(!(file->f_mode & FMODE_NOCMTIME))) {
        error = file_update_time(file);
        if (error)
            return error;
    }

    /*
     * If we're writing the file then make sure to clear the setuid and
     * setgid bits if the process is not being run by root.  This keeps
     * people from modifying setuid and setgid binaries.
     */
    return file_remove_suid(file);
}

/*
 * xfs_file_dio_aio_write - handle direct IO writes
 *
 * Lock the inode appropriately to prepare for and issue a direct IO write.
 * By separating it from the buffered write path we remove all the tricky to
 * follow locking changes and looping.
 *
 * If there are cached pages or we're extending the file, we need IOLOCK_EXCL
 * until we're sure the bytes at the new EOF have been zeroed and/or the cached
 * pages are flushed out.
 *
 * In most cases the direct IO writes will be done holding IOLOCK_SHARED
 * allowing them to be done in parallel with reads and other direct IO writes.
 * However, if the IO is not aligned to filesystem blocks, the direct IO layer
 * needs to do sub-block zeroing and that requires serialisation against other
 * direct IOs to the same block. In this case we need to serialise the
 * submission of the unaligned IOs so that we don't get racing block zeroing in
 * the dio layer.  To avoid the problem with aio, we also need to wait for
 * outstanding IOs to complete so that unwritten extent conversion is completed
 * before we try to map the overlapping block. This is currently implemented by
 * hitting it with a big hammer (i.e. inode_dio_wait()).
 *
 * Returns with locks held indicated by @iolock and errors indicated by
 * negative return values.
 */
STATIC ssize_t
xfs_file_dio_aio_write(
    struct kiocb        *iocb,
    const struct iovec  *iovp,
    unsigned long       nr_segs,
    loff_t          pos,
    size_t          ocount)
{
    struct file     *file = iocb->ki_filp;
    struct address_space    *mapping = file->f_mapping;
    struct inode        *inode = mapping->host;
    struct xfs_inode    *ip = XFS_I(inode);
    struct xfs_mount    *mp = ip->i_mount;
    ssize_t         ret = 0;
    size_t          count = ocount;
    int         unaligned_io = 0;
    int         iolock;
    struct xfs_buftarg  *target = XFS_IS_REALTIME_INODE(ip) ?
                    mp->m_rtdev_targp : mp->m_ddev_targp;

    if ((pos & target->bt_smask) || (count & target->bt_smask))
        return -XFS_ERROR(EINVAL);

    if ((pos & mp->m_blockmask) || ((pos + count) & mp->m_blockmask))
        unaligned_io = 1;

    /*
     * We don't need to take an exclusive lock unless there page cache needs
     * to be invalidated or unaligned IO is being executed. We don't need to
     * consider the EOF extension case here because
     * xfs_file_aio_write_checks() will relock the inode as necessary for
     * EOF zeroing cases and fill out the new inode size as appropriate.
     */
    if (unaligned_io || mapping->nrpages)
        iolock = XFS_IOLOCK_EXCL;
    else
        iolock = XFS_IOLOCK_SHARED;
    xfs_rw_ilock(ip, iolock);

    /*
     * Recheck if there are cached pages that need invalidate after we got
     * the iolock to protect against other threads adding new pages while
     * we were waiting for the iolock.
     */
    if (mapping->nrpages && iolock == XFS_IOLOCK_SHARED) {
        xfs_rw_iunlock(ip, iolock);
        iolock = XFS_IOLOCK_EXCL;
        xfs_rw_ilock(ip, iolock);
    }

    ret = xfs_file_aio_write_checks(file, &pos, &count, &iolock);
    if (ret)
        goto out;

    if (mapping->nrpages) {
        ret = -xfs_flushinval_pages(ip, (pos & PAGE_CACHE_MASK), -1,
                            FI_REMAPF_LOCKED);
        if (ret)
            goto out;
    }

    /*
     * If we are doing unaligned IO, wait for all other IO to drain,
     * otherwise demote the lock if we had to flush cached pages
     */
    if (unaligned_io)
        inode_dio_wait(inode);
    else if (iolock == XFS_IOLOCK_EXCL) {
        xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL);
        iolock = XFS_IOLOCK_SHARED;
    }

    trace_xfs_file_direct_write(ip, count, iocb->ki_pos, 0);
    ret = generic_file_direct_write(iocb, iovp,
            &nr_segs, pos, &iocb->ki_pos, count, ocount);

out:
    xfs_rw_iunlock(ip, iolock);

    /* No fallback to buffered IO on errors for XFS. */
    ASSERT(ret < 0 || ret == count);
    return ret;
}

STATIC ssize_t
xfs_file_buffered_aio_write(
    struct kiocb        *iocb,
    const struct iovec  *iovp,
    unsigned long       nr_segs,
    loff_t          pos,
    size_t          ocount)
{
    struct file     *file = iocb->ki_filp;
    struct address_space    *mapping = file->f_mapping;
    struct inode        *inode = mapping->host;
    struct xfs_inode    *ip = XFS_I(inode);
    ssize_t         ret;
    int         enospc = 0;
    int         iolock = XFS_IOLOCK_EXCL;
    size_t          count = ocount;

    xfs_rw_ilock(ip, iolock);

    ret = xfs_file_aio_write_checks(file, &pos, &count, &iolock);
    if (ret)
        goto out;

    /* We can write back this queue in page reclaim */
    current->backing_dev_info = mapping->backing_dev_info;

write_retry:
    trace_xfs_file_buffered_write(ip, count, iocb->ki_pos, 0);
    ret = generic_file_buffered_write(iocb, iovp, nr_segs,
            pos, &iocb->ki_pos, count, ret);
    /*
     * if we just got an ENOSPC, flush the inode now we aren't holding any
     * page locks and retry *once*
     */
    if (ret == -ENOSPC && !enospc) {
        enospc = 1;
        ret = -xfs_flush_pages(ip, 0, -1, 0, FI_NONE);
        if (!ret)
            goto write_retry;
    }

    current->backing_dev_info = NULL;
out:
    xfs_rw_iunlock(ip, iolock);
    return ret;
}

STATIC ssize_t
xfs_file_aio_write(
    struct kiocb        *iocb,
    const struct iovec  *iovp,
    unsigned long       nr_segs,
    loff_t          pos)
{
    struct file     *file = iocb->ki_filp;
    struct address_space    *mapping = file->f_mapping;
    struct inode        *inode = mapping->host;
    struct xfs_inode    *ip = XFS_I(inode);
    ssize_t         ret;
    size_t          ocount = 0;

    XFS_STATS_INC(xs_write_calls);

    BUG_ON(iocb->ki_pos != pos);

    ret = generic_segment_checks(iovp, &nr_segs, &ocount, VERIFY_READ);
    if (ret)
        return ret;

    if (ocount == 0)
        return 0;

    sb_start_write(inode->i_sb);

    if (XFS_FORCED_SHUTDOWN(ip->i_mount)) {
        ret = -EIO;
        goto out;
    }

    if (unlikely(file->f_flags & O_DIRECT))
        ret = xfs_file_dio_aio_write(iocb, iovp, nr_segs, pos, ocount);
    else
        ret = xfs_file_buffered_aio_write(iocb, iovp, nr_segs, pos,
                          ocount);

    if (ret > 0) {
        ssize_t err;

        XFS_STATS_ADD(xs_write_bytes, ret);

        /* Handle various SYNC-type writes */
        err = generic_write_sync(file, pos, ret);
        if (err < 0)
            ret = err;
    }

out:
    sb_end_write(inode->i_sb);
    return ret;
}

STATIC long
xfs_file_fallocate(
    struct file *file,
    int     mode,
    loff_t      offset,
    loff_t      len)
{
    struct inode    *inode = file->f_path.dentry->d_inode;
    long        error;
    loff_t      new_size = 0;
    xfs_flock64_t   bf;
    xfs_inode_t *ip = XFS_I(inode);
    int     cmd = XFS_IOC_RESVSP;
    int     attr_flags = XFS_ATTR_NOLOCK;

    if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
        return -EOPNOTSUPP;

    bf.l_whence = 0;
    bf.l_start = offset;
    bf.l_len = len;

    xfs_ilock(ip, XFS_IOLOCK_EXCL);

    if (mode & FALLOC_FL_PUNCH_HOLE)
        cmd = XFS_IOC_UNRESVSP;

    /* check the new inode size is valid before allocating */
    if (!(mode & FALLOC_FL_KEEP_SIZE) &&
        offset + len > i_size_read(inode)) {
        new_size = offset + len;
        error = inode_newsize_ok(inode, new_size);
        if (error)
            goto out_unlock;
    }

    if (file->f_flags & O_DSYNC)
        attr_flags |= XFS_ATTR_SYNC;

    error = -xfs_change_file_space(ip, cmd, &bf, 0, attr_flags);
    if (error)
        goto out_unlock;

    /* Change file size if needed */
    if (new_size) {
        struct iattr iattr;

        iattr.ia_valid = ATTR_SIZE;
        iattr.ia_size = new_size;
        error = -xfs_setattr_size(ip, &iattr, XFS_ATTR_NOLOCK);
    }

out_unlock:
    xfs_iunlock(ip, XFS_IOLOCK_EXCL);
    return error;
}


STATIC int
xfs_file_open(
    struct inode    *inode,
    struct file *file)
{
    if (!(file->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
        return -EFBIG;
    if (XFS_FORCED_SHUTDOWN(XFS_M(inode->i_sb)))
        return -EIO;
    return 0;
}

STATIC int
xfs_dir_open(
    struct inode    *inode,
    struct file *file)
{
    struct xfs_inode *ip = XFS_I(inode);
    int     mode;
    int     error;

    error = xfs_file_open(inode, file);
    if (error)
        return error;

    /*
     * If there are any blocks, read-ahead block 0 as we're almost
     * certain to have the next operation be a read there.
     */
    mode = xfs_ilock_map_shared(ip);
    if (ip->i_d.di_nextents > 0)
        xfs_da_reada_buf(NULL, ip, 0, XFS_DATA_FORK);
    xfs_iunlock(ip, mode);
    return 0;
}

STATIC int
xfs_file_release(
    struct inode    *inode,
    struct file *filp)
{
    return -xfs_release(XFS_I(inode));
}

STATIC int
xfs_file_readdir(
    struct file *filp,
    void        *dirent,
    filldir_t   filldir)
{
    struct inode    *inode = filp->f_path.dentry->d_inode;
    xfs_inode_t *ip = XFS_I(inode);
    int     error;
    size_t      bufsize;

    /*
     * The Linux API doesn't pass down the total size of the buffer
     * we read into down to the filesystem.  With the filldir concept
     * it's not needed for correct information, but the XFS dir2 leaf
     * code wants an estimate of the buffer size to calculate it's
     * readahead window and size the buffers used for mapping to
     * physical blocks.
     *
     * Try to give it an estimate that's good enough, maybe at some
     * point we can change the ->readdir prototype to include the
     * buffer size.  For now we use the current glibc buffer size.
     */
    bufsize = (size_t)min_t(loff_t, 32768, ip->i_d.di_size);

    error = xfs_readdir(ip, dirent, bufsize,
                (xfs_off_t *)&filp->f_pos, filldir);
    if (error)
        return -error;
    return 0;
}

STATIC int
xfs_file_mmap(
    struct file *filp,
    struct vm_area_struct *vma)
{
    vma->vm_ops = &xfs_file_vm_ops;

    file_accessed(filp);
    return 0;
}

/*
 * mmap()d file has taken write protection fault and is being made
 * writable. We can set the page state up correctly for a writable
 * page, which means we can do correct delalloc accounting (ENOSPC
 * checking!) and unwritten extent mapping.
 */
STATIC int
xfs_vm_page_mkwrite(
    struct vm_area_struct   *vma,
    struct vm_fault     *vmf)
{
    return block_page_mkwrite(vma, vmf, xfs_get_blocks);
}

/*
 * This type is designed to indicate the type of offset we would like
 * to search from page cache for either xfs_seek_data() or xfs_seek_hole().
 */
enum {
    HOLE_OFF = 0,
    DATA_OFF,
};

/*
 * Lookup the desired type of offset from the given page.
 *
 * On success, return true and the offset argument will point to the
 * start of the region that was found.  Otherwise this function will
 * return false and keep the offset argument unchanged.
 */
STATIC bool
xfs_lookup_buffer_offset(
    struct page     *page,
    loff_t          *offset,
    unsigned int        type)
{
    loff_t          lastoff = page_offset(page);
    bool            found = false;
    struct buffer_head  *bh, *head;

    bh = head = page_buffers(page);
    do {
        /*
         * Unwritten extents that have data in the page
         * cache covering them can be identified by the
         * BH_Unwritten state flag.  Pages with multiple
         * buffers might have a mix of holes, data and
         * unwritten extents - any buffer with valid
         * data in it should have BH_Uptodate flag set
         * on it.
         */
        if (buffer_unwritten(bh) ||
            buffer_uptodate(bh)) {
            if (type == DATA_OFF)
                found = true;
        } else {
            if (type == HOLE_OFF)
                found = true;
        }

        if (found) {
            *offset = lastoff;
            break;
        }
        lastoff += bh->b_size;
    } while ((bh = bh->b_this_page) != head);

    return found;
}

/*
 * This routine is called to find out and return a data or hole offset
 * from the page cache for unwritten extents according to the desired
 * type for xfs_seek_data() or xfs_seek_hole().
 *
 * The argument offset is used to tell where we start to search from the
 * page cache.  Map is used to figure out the end points of the range to
 * lookup pages.
 *
 * Return true if the desired type of offset was found, and the argument
 * offset is filled with that address.  Otherwise, return false and keep
 * offset unchanged.
 */
STATIC bool
xfs_find_get_desired_pgoff(
    struct inode        *inode,
    struct xfs_bmbt_irec    *map,
    unsigned int        type,
    loff_t          *offset)
{
    struct xfs_inode    *ip = XFS_I(inode);
    struct xfs_mount    *mp = ip->i_mount;
    struct pagevec      pvec;
    pgoff_t         index;
    pgoff_t         end;
    loff_t          endoff;
    loff_t          startoff = *offset;
    loff_t          lastoff = startoff;
    bool            found = false;

    pagevec_init(&pvec, 0);

    index = startoff >> PAGE_CACHE_SHIFT;
    endoff = XFS_FSB_TO_B(mp, map->br_startoff + map->br_blockcount);
    end = endoff >> PAGE_CACHE_SHIFT;
    do {
        int     want;
        unsigned    nr_pages;
        unsigned int    i;

        want = min_t(pgoff_t, end - index, PAGEVEC_SIZE);
        nr_pages = pagevec_lookup(&pvec, inode->i_mapping, index,
                      want);
        /*
         * No page mapped into given range.  If we are searching holes
         * and if this is the first time we got into the loop, it means
         * that the given offset is landed in a hole, return it.
         *
         * If we have already stepped through some block buffers to find
         * holes but they all contains data.  In this case, the last
         * offset is already updated and pointed to the end of the last
         * mapped page, if it does not reach the endpoint to search,
         * that means there should be a hole between them.
         */
        if (nr_pages == 0) {
            /* Data search found nothing */
            if (type == DATA_OFF)
                break;

            ASSERT(type == HOLE_OFF);
            if (lastoff == startoff || lastoff < endoff) {
                found = true;
                *offset = lastoff;
            }
            break;
        }

        /*
         * At lease we found one page.  If this is the first time we
         * step into the loop, and if the first page index offset is
         * greater than the given search offset, a hole was found.
         */
        if (type == HOLE_OFF && lastoff == startoff &&
            lastoff < page_offset(pvec.pages[0])) {
            found = true;
            break;
        }

        for (i = 0; i < nr_pages; i++) {
            struct page *page = pvec.pages[i];
            loff_t      b_offset;

            /*
             * At this point, the page may be truncated or
             * invalidated (changing page->mapping to NULL),
             * or even swizzled back from swapper_space to tmpfs
             * file mapping. However, page->index will not change
             * because we have a reference on the page.
             *
             * Searching done if the page index is out of range.
             * If the current offset is not reaches the end of
             * the specified search range, there should be a hole
             * between them.
             */
            if (page->index > end) {
                if (type == HOLE_OFF && lastoff < endoff) {
                    *offset = lastoff;
                    found = true;
                }
                goto out;
            }

            lock_page(page);
            /*
             * Page truncated or invalidated(page->mapping == NULL).
             * We can freely skip it and proceed to check the next
             * page.
             */
            if (unlikely(page->mapping != inode->i_mapping)) {
                unlock_page(page);
                continue;
            }

            if (!page_has_buffers(page)) {
                unlock_page(page);
                continue;
            }

            found = xfs_lookup_buffer_offset(page, &b_offset, type);
            if (found) {
                /*
                 * The found offset may be less than the start
                 * point to search if this is the first time to
                 * come here.
                 */
                *offset = max_t(loff_t, startoff, b_offset);
                unlock_page(page);
                goto out;
            }

            /*
             * We either searching data but nothing was found, or
             * searching hole but found a data buffer.  In either
             * case, probably the next page contains the desired
             * things, update the last offset to it so.
             */
            lastoff = page_offset(page) + PAGE_SIZE;
            unlock_page(page);
        }

        /*
         * The number of returned pages less than our desired, search
         * done.  In this case, nothing was found for searching data,
         * but we found a hole behind the last offset.
         */
        if (nr_pages < want) {
            if (type == HOLE_OFF) {
                *offset = lastoff;
                found = true;
            }
            break;
        }

        index = pvec.pages[i - 1]->index + 1;
        pagevec_release(&pvec);
    } while (index <= end);

out:
    pagevec_release(&pvec);
    return found;
}

STATIC loff_t
xfs_seek_data(
    struct file     *file,
    loff_t          start)
{
    struct inode        *inode = file->f_mapping->host;
    struct xfs_inode    *ip = XFS_I(inode);
    struct xfs_mount    *mp = ip->i_mount;
    loff_t          uninitialized_var(offset);
    xfs_fsize_t     isize;
    xfs_fileoff_t       fsbno;
    xfs_filblks_t       end;
    uint            lock;
    int         error;

    lock = xfs_ilock_map_shared(ip);

    isize = i_size_read(inode);
    if (start >= isize) {
        error = ENXIO;
        goto out_unlock;
    }

    /*
     * Try to read extents from the first block indicated
     * by fsbno to the end block of the file.
     */
    fsbno = XFS_B_TO_FSBT(mp, start);
    end = XFS_B_TO_FSB(mp, isize);
    for (;;) {
        struct xfs_bmbt_irec    map[2];
        int         nmap = 2;
        unsigned int        i;

        error = xfs_bmapi_read(ip, fsbno, end - fsbno, map, &nmap,
                       XFS_BMAPI_ENTIRE);
        if (error)
            goto out_unlock;

        /* No extents at given offset, must be beyond EOF */
        if (nmap == 0) {
            error = ENXIO;
            goto out_unlock;
        }

        for (i = 0; i < nmap; i++) {
            offset = max_t(loff_t, start,
                       XFS_FSB_TO_B(mp, map[i].br_startoff));

            /* Landed in a data extent */
            if (map[i].br_startblock == DELAYSTARTBLOCK ||
                (map[i].br_state == XFS_EXT_NORM &&
                 !isnullstartblock(map[i].br_startblock)))
                goto out;

            /*
             * Landed in an unwritten extent, try to search data
             * from page cache.
             */
            if (map[i].br_state == XFS_EXT_UNWRITTEN) {
                if (xfs_find_get_desired_pgoff(inode, &map[i],
                            DATA_OFF, &offset))
                    goto out;
            }
        }

        /*
         * map[0] is hole or its an unwritten extent but
         * without data in page cache.  Probably means that
         * we are reading after EOF if nothing in map[1].
         */
        if (nmap == 1) {
            error = ENXIO;
            goto out_unlock;
        }

        ASSERT(i > 1);

        /*
         * Nothing was found, proceed to the next round of search
         * if reading offset not beyond or hit EOF.
         */
        fsbno = map[i - 1].br_startoff + map[i - 1].br_blockcount;
        start = XFS_FSB_TO_B(mp, fsbno);
        if (start >= isize) {
            error = ENXIO;
            goto out_unlock;
        }
    }

out:
    if (offset != file->f_pos)
        file->f_pos = offset;

out_unlock:
    xfs_iunlock_map_shared(ip, lock);

    if (error)
        return -error;
    return offset;
}

STATIC loff_t
xfs_seek_hole(
    struct file     *file,
    loff_t          start)
{
    struct inode        *inode = file->f_mapping->host;
    struct xfs_inode    *ip = XFS_I(inode);
    struct xfs_mount    *mp = ip->i_mount;
    loff_t          uninitialized_var(offset);
    xfs_fsize_t     isize;
    xfs_fileoff_t       fsbno;
    xfs_filblks_t       end;
    uint            lock;
    int         error;

    if (XFS_FORCED_SHUTDOWN(mp))
        return -XFS_ERROR(EIO);

    lock = xfs_ilock_map_shared(ip);

    isize = i_size_read(inode);
    if (start >= isize) {
        error = ENXIO;
        goto out_unlock;
    }

    fsbno = XFS_B_TO_FSBT(mp, start);
    end = XFS_B_TO_FSB(mp, isize);

    for (;;) {
        struct xfs_bmbt_irec    map[2];
        int         nmap = 2;
        unsigned int        i;

        error = xfs_bmapi_read(ip, fsbno, end - fsbno, map, &nmap,
                       XFS_BMAPI_ENTIRE);
        if (error)
            goto out_unlock;

        /* No extents at given offset, must be beyond EOF */
        if (nmap == 0) {
            error = ENXIO;
            goto out_unlock;
        }

        for (i = 0; i < nmap; i++) {
            offset = max_t(loff_t, start,
                       XFS_FSB_TO_B(mp, map[i].br_startoff));

            /* Landed in a hole */
            if (map[i].br_startblock == HOLESTARTBLOCK)
                goto out;

            /*
             * Landed in an unwritten extent, try to search hole
             * from page cache.
             */
            if (map[i].br_state == XFS_EXT_UNWRITTEN) {
                if (xfs_find_get_desired_pgoff(inode, &map[i],
                            HOLE_OFF, &offset))
                    goto out;
            }
        }

        /*
         * map[0] contains data or its unwritten but contains
         * data in page cache, probably means that we are
         * reading after EOF.  We should fix offset to point
         * to the end of the file(i.e., there is an implicit
         * hole at the end of any file).
         */
        if (nmap == 1) {
            offset = isize;
            break;
        }

        ASSERT(i > 1);

        /*
         * Both mappings contains data, proceed to the next round of
         * search if the current reading offset not beyond or hit EOF.
         */
        fsbno = map[i - 1].br_startoff + map[i - 1].br_blockcount;
        start = XFS_FSB_TO_B(mp, fsbno);
        if (start >= isize) {
            offset = isize;
            break;
        }
    }

out:
    /*
     * At this point, we must have found a hole.  However, the returned
     * offset may be bigger than the file size as it may be aligned to
     * page boundary for unwritten extents, we need to deal with this
     * situation in particular.
     */
    offset = min_t(loff_t, offset, isize);
    if (offset != file->f_pos)
        file->f_pos = offset;

out_unlock:
    xfs_iunlock_map_shared(ip, lock);

    if (error)
        return -error;
    return offset;
}

STATIC loff_t
xfs_file_llseek(
    struct file *file,
    loff_t      offset,
    int     origin)
{
    switch (origin) {
    case SEEK_END:
    case SEEK_CUR:
    case SEEK_SET:
        return generic_file_llseek(file, offset, origin);
    case SEEK_DATA:
        return xfs_seek_data(file, offset);
    case SEEK_HOLE:
        return xfs_seek_hole(file, offset);
    default:
        return -EINVAL;
    }
}

const struct file_operations xfs_file_operations = {
    .llseek     = xfs_file_llseek,
    .read       = do_sync_read,
    .write      = do_sync_write,
    .aio_read   = xfs_file_aio_read,
    .aio_write  = xfs_file_aio_write,
    .splice_read    = xfs_file_splice_read,
    .splice_write   = xfs_file_splice_write,
    .unlocked_ioctl = xfs_file_ioctl,
#ifdef CONFIG_COMPAT
    .compat_ioctl   = xfs_file_compat_ioctl,
#endif
    .mmap       = xfs_file_mmap,
    .open       = xfs_file_open,
    .release    = xfs_file_release,
    .fsync      = xfs_file_fsync,
    .fallocate  = xfs_file_fallocate,
};

const struct file_operations xfs_dir_file_operations = {
    .open       = xfs_dir_open,
    .read       = generic_read_dir,
    .readdir    = xfs_file_readdir,
    .llseek     = generic_file_llseek,
    .unlocked_ioctl = xfs_file_ioctl,
#ifdef CONFIG_COMPAT
    .compat_ioctl   = xfs_file_compat_ioctl,
#endif
    .fsync      = xfs_dir_fsync,
};

static const struct vm_operations_struct xfs_file_vm_ops = {
    .fault      = filemap_fault,
    .page_mkwrite   = xfs_vm_page_mkwrite,
    .remap_pages    = generic_file_remap_pages,
};