From a9bd24ac2becf69e896d88bf8b1b7b0f18c2157b Mon Sep 17 00:00:00 2001 From: Brian Foster Date: Tue, 15 Mar 2016 11:42:46 +1100 Subject: [PATCH] xfs: refactor delalloc indlen reservation split into helper The delayed allocation indirect reservation splitting code is not sufficient in some cases where a delalloc extent is split in two. In preparation for enhancements to this code, refactor the current indlen distribution algorithm into a new helper function. [dchinner: rename temp, temp2 variables] Signed-off-by: Brian Foster Reviewed-by: Dave Chinner Signed-off-by: Dave Chinner --- fs/xfs/libxfs/xfs_bmap.c | 75 +++++++++++++++++++++++++++++----------- 1 file changed, 55 insertions(+), 20 deletions(-) diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c index b48abc300c36..6de613b558a9 100644 --- a/fs/xfs/libxfs/xfs_bmap.c +++ b/fs/xfs/libxfs/xfs_bmap.c @@ -4720,6 +4720,47 @@ error0: return error; } +/* + * When a delalloc extent is split (e.g., due to a hole punch), the original + * indlen reservation must be shared across the two new extents that are left + * behind. + * + * Given the original reservation and the worst case indlen for the two new + * extents (as calculated by xfs_bmap_worst_indlen()), split the original + * reservation fairly across the two new extents. + */ +static void +xfs_bmap_split_indlen( + xfs_filblks_t ores, /* original res. */ + xfs_filblks_t *indlen1, /* ext1 worst indlen */ + xfs_filblks_t *indlen2) /* ext2 worst indlen */ +{ + xfs_filblks_t len1 = *indlen1; + xfs_filblks_t len2 = *indlen2; + xfs_filblks_t nres = len1 + len2; /* new total res. */ + + /* + * The only blocks available are those reserved for the original extent. + * Therefore, we have to skim blocks off each of the new reservations so + * long as the new total reservation is greater than the original. + */ + while (nres > ores) { + if (len1) { + len1--; + nres--; + } + if (nres == ores) + break; + if (len2) { + len2--; + nres--; + } + } + + *indlen1 = len1; + *indlen2 = len2; +} + /* * Called by xfs_bmapi to update file extent records and the btree * after removing space (or undoing a delayed allocation). @@ -4985,27 +5026,21 @@ xfs_bmap_del_extent( XFS_IFORK_NEXTENTS(ip, whichfork) + 1); } else { ASSERT(whichfork == XFS_DATA_FORK); - temp = xfs_bmap_worst_indlen(ip, temp); - xfs_bmbt_set_startblock(ep, nullstartblock((int)temp)); - temp2 = xfs_bmap_worst_indlen(ip, temp2); - new.br_startblock = nullstartblock((int)temp2); + + /* + * Distribute the original indlen reservation across the + * two new extents. + */ + temp = xfs_bmap_worst_indlen(ip, got.br_blockcount); + temp2 = xfs_bmap_worst_indlen(ip, new.br_blockcount); + xfs_bmap_split_indlen(da_old, &temp, &temp2); da_new = temp + temp2; - while (da_new > da_old) { - if (temp) { - temp--; - da_new--; - xfs_bmbt_set_startblock(ep, - nullstartblock((int)temp)); - } - if (da_new == da_old) - break; - if (temp2) { - temp2--; - da_new--; - new.br_startblock = - nullstartblock((int)temp2); - } - } + + /* + * Set the reservation for each extent. + */ + xfs_bmbt_set_startblock(ep, nullstartblock((int)temp)); + new.br_startblock = nullstartblock((int)temp2); } trace_xfs_bmap_post_update(ip, *idx, state, _THIS_IP_); xfs_iext_insert(ip, *idx + 1, 1, &new, state);