xfs: don't rely on ->total in xfs_alloc_space_available

->total is a bit of an odd parameter passed down to the low-level
allocator all the way from the high-level callers.  It's supposed to
contain the maximum number of blocks to be allocated for the whole
transaction [1].

But in xfs_iomap_write_allocate we only convert existing delayed
allocations and thus only have a minimal block reservation for the
current transaction, so xfs_alloc_space_available can't use it for
the allocation decisions.  Use the maximum of args->total and the
calculated block requirement to make a decision.  We probably should
get rid of args->total eventually and instead apply ->minleft more
broadly, but that will require some extensive changes all over.

[1] which creates lots of confusion as most callers don't decrement it
once doing a first allocation.  But that's for a separate series.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index f2e7eb6e5243..9f06a211e157 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -1995,7 +1995,7 @@ xfs_alloc_space_available(
         int                     flags)
 {
         struct xfs_perag        *pag = args->pag;
-        xfs_extlen_t            longest;
+        xfs_extlen_t            alloc_len, longest;
         xfs_extlen_t            reservation; /* blocks that are still reserved */
         int                     available;
 
@@ -2005,15 +2005,16 @@ xfs_alloc_space_available(
         reservation = xfs_ag_resv_needed(pag, args->resv);
 
         /* do we have enough contiguous free space for the allocation? */
+        alloc_len = args->minlen + (args->alignment - 1) + args->minalignslop;
         longest = xfs_alloc_longest_free_extent(args->mp, pag, min_free,
                         reservation);
-        if ((args->minlen + args->alignment + args->minalignslop - 1) > longest)
+        if (longest < alloc_len)
                 return false;
 
         /* do we have enough free space remaining for the allocation? */
         available = (int)(pag->pagf_freeblks + pag->pagf_flcount -
                           reservation - min_free - args->minleft);
-        if (available < (int)args->total)
+        if (available < (int)max(args->total, alloc_len))
                 return false;
 
         /*