Lachlan McIlroy wrote:
> 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.
Lachlan, so what's the failure mode? (is it that we simply don't do
that speculative preallocation anymore due to the problem?)
From your description of the change above, it seems like you're talking
about:
dd9f438e32900d67def49fa1b8961b3e19b6fefc
[XFS] Implement the di_extsize allocator hint for non-realtime files as
well. Also provides a mechanism for inheriting this property from the
parent directory for new files.
SGI-PV: 945264
SGI-Modid: xfs-linux-melb:xfs-kern:24367a
Signed-off-by: Nathan Scott <nathans@xxxxxxx>
but that isn't really a cleanup; and I don't think it changed the isize
behavior.
Was it possibly [XFS] Fix to prevent the notorious 'NULL files' problem
after a crash. that caused the regression?
Thanks,
-Eric
> --- 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;
> }
>
>
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