xfs: bump up reserved blocks in xfs_alloc_set_aside

Setting aside 4 blocks globally for bmbt splits isn't all that useful,
as different threads can allocate space in parallel.  Bump it to 4
blocks per AG to allow each thread that is currently doing an
allocation to dip into it separately.  Without that we may no have
enough reserved blocks if there are enough parallel transactions
in an almost out space file system that all run into bmap btree
splits.

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>

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index 5050056a0b06445a93845987a52ec8356c499f80..0a46f8488b8dc3791090d19ebbb51a54de3d3a4c 100644 (file)
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -95,10 +95,7 @@ unsigned int
 xfs_alloc_set_aside(
        struct xfs_mount        *mp)
 {
-       unsigned int            blocks;
-
-       blocks = 4 + (mp->m_sb.sb_agcount * XFS_ALLOC_AGFL_RESERVE);
-       return blocks;
+       return mp->m_sb.sb_agcount * (XFS_ALLOC_AGFL_RESERVE + 4);
 }
 
 /*