diff options
| -rw-r--r-- | fs/xfs/xfs_iomap.c | 75 |
1 files changed, 50 insertions, 25 deletions
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c index d16f40cdf5f6..637a24473f9b 100644 --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -702,6 +702,9 @@ retry: * the originating callers request. * * Called without a lock on the inode. + * + * We no longer bother to look at the incoming map - all we have to + * guarantee is that whatever we allocate fills the required range. */ int xfs_iomap_write_allocate( @@ -717,9 +720,9 @@ xfs_iomap_write_allocate( xfs_fsblock_t first_block; xfs_bmap_free_t free_list; xfs_filblks_t count_fsb; - xfs_bmbt_irec_t imap[XFS_STRAT_WRITE_IMAPS]; + xfs_bmbt_irec_t imap; xfs_trans_t *tp; - int i, nimaps, committed; + int nimaps, committed; int error = 0; int nres; @@ -766,13 +769,38 @@ xfs_iomap_write_allocate( XFS_BMAP_INIT(&free_list, &first_block); - nimaps = XFS_STRAT_WRITE_IMAPS; /* - * Ensure we don't go beyond eof - it is possible - * the extents changed since we did the read call, - * we dropped the ilock in the interim. + * it is possible that the extents have changed since + * we did the read call as we dropped the ilock for a + * while. We have to be careful about truncates or hole + * punchs here - we are not allowed to allocate + * non-delalloc blocks here. + * + * The only protection against truncation is the pages + * for the range we are being asked to convert are + * locked and hence a truncate will block on them + * first. + * + * As a result, if we go beyond the range we really + * need and hit an delalloc extent boundary followed by + * a hole while we have excess blocks in the map, we + * will fill the hole incorrectly and overrun the + * transaction reservation. + * + * Using a single map prevents this as we are forced to + * check each map we look for overlap with the desired + * range and abort as soon as we find it. Also, given + * that we only return a single map, having one beyond + * what we can return is probably a bit silly. + * + * We also need to check that we don't go beyond EOF; + * this is a truncate optimisation as a truncate sets + * the new file size before block on the pages we + * currently have locked under writeback. Because they + * are about to be tossed, we don't need to write them + * back.... */ - + nimaps = 1; end_fsb = XFS_B_TO_FSB(mp, ip->i_size); xfs_bmap_last_offset(NULL, ip, &last_block, XFS_DATA_FORK); @@ -788,7 +816,7 @@ xfs_iomap_write_allocate( /* Go get the actual blocks */ error = xfs_bmapi(tp, ip, map_start_fsb, count_fsb, XFS_BMAPI_WRITE, &first_block, 1, - imap, &nimaps, &free_list, NULL); + &imap, &nimaps, &free_list, NULL); if (error) goto trans_cancel; @@ -807,27 +835,24 @@ xfs_iomap_write_allocate( * See if we were able to allocate an extent that * covers at least part of the callers request */ - for (i = 0; i < nimaps; i++) { - if (unlikely(!imap[i].br_startblock && - !(ip->i_d.di_flags & XFS_DIFLAG_REALTIME))) - return xfs_cmn_err_fsblock_zero(ip, &imap[i]); - if ((offset_fsb >= imap[i].br_startoff) && - (offset_fsb < (imap[i].br_startoff + - imap[i].br_blockcount))) { - *map = imap[i]; - *retmap = 1; - XFS_STATS_INC(xs_xstrat_quick); - return 0; - } - count_fsb -= imap[i].br_blockcount; + if (unlikely(!imap.br_startblock && + XFS_IS_REALTIME_INODE(ip))) + return xfs_cmn_err_fsblock_zero(ip, &imap); + if ((offset_fsb >= imap.br_startoff) && + (offset_fsb < (imap.br_startoff + + imap.br_blockcount))) { + *map = imap; + *retmap = 1; + XFS_STATS_INC(xs_xstrat_quick); + return 0; } - /* So far we have not mapped the requested part of the + /* + * So far we have not mapped the requested part of the * file, just surrounding data, try again. */ - nimaps--; - map_start_fsb = imap[nimaps].br_startoff + - imap[nimaps].br_blockcount; + count_fsb -= imap.br_blockcount; + map_start_fsb = imap.br_startoff + imap.br_blockcount; } trans_cancel: |