[PATCH 02/20] xfs: factor out free space extent length check

Dave Chinner
2015-06-03T06:05:11Z

The longest extent length checks in xfs_alloc_fix_freelist() are now
essentially identical. Factor them out into a helper function, so we
know they are checking exactly the same thing before and after we
lock the AGF.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
fs/xfs/libxfs/xfs_alloc.c | 71 +++++++++++++++++++++++++++++------------------
1 file changed, 44 insertions(+), 27 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index 08b45f8..2471cb5 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -1871,6 +1871,39 @@ xfs_alloc_longest_free_extent(
}

/*
+ * Check if the operation we are fixing up the freelist for should go ahead or
+ * not. If we are freeing blocks, we always allow it, otherwise the allocation
+ * is dependent on whether the size and shape of free space available will
+ * permit the requested allocation to take place.
+ */
+static bool
+xfs_alloc_space_available(
+ struct xfs_alloc_arg *args,
+ xfs_extlen_t min_free,
+ int flags)
+{
+ struct xfs_perag *pag = args->pag;
+ xfs_extlen_t longest;
+ int available;
+
+ if (flags & XFS_ALLOC_FLAG_FREEING)
+ return true;
+
+ /* do we have enough contiguous free space for the allocation? */
+ longest = xfs_alloc_longest_free_extent(args->mp, pag, min_free);
+ if ((args->minlen + args->alignment + args->minalignslop - 1) > longest)
+ return false;
+
+ /* do have enough free space remaining for the allocation? */
+ available = (int)(pag->pagf_freeblks + pag->pagf_flcount -
+ min_free - args->total);
+ if (available < (int)args->minleft)
+ return false;
+
+ return true;
+}
+
+/*
* Decide whether to use this allocation group for this allocation.
* If so, fix up the btree freelist's size.
*/
@@ -1883,7 +1916,6 @@ xfs_alloc_fix_freelist(
xfs_buf_t *agflbp;/* agfl buffer pointer */
xfs_agblock_t bno; /* freelist block */
int error; /* error result code */
- xfs_extlen_t longest;/* longest extent in allocation group */
xfs_mount_t *mp; /* file system mount point structure */
xfs_extlen_t need; /* total blocks needed in freelist */
xfs_perag_t *pag; /* per-ag information structure */
@@ -1919,22 +1951,12 @@ xfs_alloc_fix_freelist(
return 0;
}

- if (!(flags & XFS_ALLOC_FLAG_FREEING)) {
- /*
- * If it looks like there isn't a long enough extent, or enough
- * total blocks, reject it.
- */
- need = XFS_MIN_FREELIST_PAG(pag, mp);
- longest = xfs_alloc_longest_free_extent(mp, pag, need);
- if ((args->minlen + args->alignment + args->minalignslop - 1) >
- longest ||
- ((int)(pag->pagf_freeblks + pag->pagf_flcount -
- need - args->total) < (int)args->minleft)) {
- if (agbp)
- xfs_trans_brelse(tp, agbp);
- args->agbp = NULL;
- return 0;
- }
+ need = XFS_MIN_FREELIST_PAG(pag, mp);
+ if (!xfs_alloc_space_available(args, need, flags)) {
+ if (agbp)
+ xfs_trans_brelse(tp, agbp);
+ args->agbp = NULL;
+ return 0;
}

/*
@@ -1956,17 +1978,12 @@ xfs_alloc_fix_freelist(

/* If there isn't enough total space or single-extent, reject it. */
need = XFS_MIN_FREELIST_PAG(pag, mp);
- if (!(flags & XFS_ALLOC_FLAG_FREEING)) {
- longest = xfs_alloc_longest_free_extent(mp, pag, need);
- if ((args->minlen + args->alignment + args->minalignslop - 1) >
- longest ||
- ((int)(pag->pagf_freeblks + pag->pagf_flcount -
- need - args->total) < (int)args->minleft)) {
- xfs_trans_brelse(tp, agbp);
- args->agbp = NULL;
- return 0;
- }
+ if (!xfs_alloc_space_available(args, need, flags)) {
+ xfs_trans_brelse(tp, agbp);
+ args->agbp = NULL;
+ return 0;
}
+
/*
* Make the freelist shorter if it's too long.
*