[Fwd: [PATCH] Fix speculative allocation beyond eof]

[Lachlan McIlroy <lachlan@xxxxxxx>]

ping.

Anyone have any objections to this?

-------- Original Message --------
Subject: [PATCH] Fix speculative allocation beyond eof
Date: Tue, 23 Sep 2008 13:14:44 +1000
From: Lachlan McIlroy <lachlan@xxxxxxx>
Reply-To: lachlan@xxxxxxx
To: xfs-dev <xfs-dev@xxxxxxx>, xfs-oss <xfs@xxxxxxxxxxx>

Speculative allocation beyond eof doesn't work properly.  It was broken some
time ago after a code cleanup that moved what is now 
xfs_iomap_eof_align_last_fsb()
and xfs_iomap_eof_want_preallocate() out of xfs_iomap_write_delay() into
separate functions.  The code used to use the current file size in various 
checks
but got changed to be max(file_size, i_new_size).  Since i_new_size is the 
result
of 'offset + count' then in xfs_iomap_eof_want_preallocate() the check for
'(offset + count) <= isize' will always be true.

ie if 'offset + count' is > ip->i_size then isize will be i_new_size and equal 
to
'offset + count'.

This change fixes all the places that used to use the current file size.

--- a/fs/xfs/xfs_iomap.c        2008-09-23 12:52:12.000000000 +1000
+++ b/fs/xfs/xfs_iomap.c        2008-09-23 12:51:29.000000000 +1000
@@ -290,7 +290,6 @@ STATIC int
xfs_iomap_eof_align_last_fsb(
        xfs_mount_t     *mp,
        xfs_inode_t     *ip,
-       xfs_fsize_t     isize,
        xfs_extlen_t    extsize,
        xfs_fileoff_t   *last_fsb)
{
@@ -306,14 +305,14 @@ xfs_iomap_eof_align_last_fsb(
         * stripe width and we are allocating past the allocation eof.
         */
        else if (mp->m_swidth && (mp->m_flags & XFS_MOUNT_SWALLOC) &&
-               (isize >= XFS_FSB_TO_B(mp, mp->m_swidth)))
+               (ip->i_size >= XFS_FSB_TO_B(mp, mp->m_swidth)))
                new_last_fsb = roundup_64(*last_fsb, mp->m_swidth);
        /*
         * Roundup the allocation request to a stripe unit (m_dalign) boundary
         * if the file size is >= stripe unit size, and we are allocating past
         * the allocation eof.
         */
-       else if (mp->m_dalign && (isize >= XFS_FSB_TO_B(mp, mp->m_dalign)))
+       else if (mp->m_dalign && (ip->i_size >= XFS_FSB_TO_B(mp, mp->m_dalign)))
                new_last_fsb = roundup_64(*last_fsb, mp->m_dalign);

        /*
@@ -403,7 +402,6 @@ xfs_iomap_write_direct(
        xfs_filblks_t   count_fsb, resaligned;
        xfs_fsblock_t   firstfsb;
        xfs_extlen_t    extsz, temp;
-       xfs_fsize_t     isize;
        int             nimaps;
        int             bmapi_flag;
        int             quota_flag;
@@ -426,15 +424,10 @@ xfs_iomap_write_direct(
        rt = XFS_IS_REALTIME_INODE(ip);
        extsz = xfs_get_extsz_hint(ip);

-       isize = ip->i_size;
-       if (ip->i_new_size > isize)
-               isize = ip->i_new_size;
-
        offset_fsb = XFS_B_TO_FSBT(mp, offset);
        last_fsb = XFS_B_TO_FSB(mp, ((xfs_ufsize_t)(offset + count)));
-       if ((offset + count) > isize) {
-               error = xfs_iomap_eof_align_last_fsb(mp, ip, isize, extsz,
-                                                       &last_fsb);
+       if ((offset + count) > ip->i_size) {
+               error = xfs_iomap_eof_align_last_fsb(mp, ip, extsz, &last_fsb);
                if (error)
                        goto error_out;
        } else {
@@ -559,7 +552,6 @@ STATIC int
xfs_iomap_eof_want_preallocate(
        xfs_mount_t     *mp,
        xfs_inode_t     *ip,
-       xfs_fsize_t     isize,
        xfs_off_t       offset,
        size_t          count,
        int             ioflag,
@@ -573,7 +565,7 @@ xfs_iomap_eof_want_preallocate(
        int             n, error, imaps;

        *prealloc = 0;
-       if ((ioflag & BMAPI_SYNC) || (offset + count) <= isize)
+       if ((ioflag & BMAPI_SYNC) || (offset + count) <= ip->i_size)
                return 0;

        /*
@@ -617,7 +609,6 @@ xfs_iomap_write_delay(
        xfs_fileoff_t   ioalign;
        xfs_fsblock_t   firstblock;
        xfs_extlen_t    extsz;
-       xfs_fsize_t     isize;
        int             nimaps;
        xfs_bmbt_irec_t imap[XFS_WRITE_IMAPS];
        int             prealloc, fsynced = 0;
@@ -637,11 +628,7 @@ xfs_iomap_write_delay(
        offset_fsb = XFS_B_TO_FSBT(mp, offset);

retry:
-       isize = ip->i_size;
-       if (ip->i_new_size > isize)
-               isize = ip->i_new_size;
-
-       error = xfs_iomap_eof_want_preallocate(mp, ip, isize, offset, count,
+       error = xfs_iomap_eof_want_preallocate(mp, ip, offset, count,
                                ioflag, imap, XFS_WRITE_IMAPS, &prealloc);
        if (error)
                return error;
@@ -655,8 +642,7 @@ retry:
        }

        if (prealloc || extsz) {
-               error = xfs_iomap_eof_align_last_fsb(mp, ip, isize, extsz,
-                                                       &last_fsb);
+               error = xfs_iomap_eof_align_last_fsb(mp, ip, extsz, &last_fsb);
                if (error)
                        return error;
        }