[PATCH 107/119] xfs: set a default CoW extent size of 32 blocks

Darrick J. Wong
2016-06-17T01:29:36Z

If the admin doesn't set a CoW extent size or a regular extent size
hint, default to creating CoW reservations 32 blocks long to reduce
fragmentation.

Signed-off-by: DarricK J. Wong <darrick.wong@oracle.com>
---
fs/xfs/xfs_inode.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index fb9c2d7..f2971e2 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -80,7 +80,8 @@ xfs_get_extsz_hint(
/*
* Helper function to extract CoW extent size hint from inode.
* Between the extent size hint and the CoW extent size hint, we
- * return the greater of the two.
+ * return the greater of the two. If the value is zero (automatic),
+ * default to 32 blocks.
*/
xfs_extlen_t
xfs_get_cowextsz_hint(
@@ -93,9 +94,10 @@ xfs_get_cowextsz_hint(
a = ip->i_d.di_cowextsize;
b = xfs_get_extsz_hint(ip);

- if (a > b)
- return a;
- return b;
+ a = max(a, b);
+ if (a == 0)
+ return 32;
+ return a;
}

/*