[PATCH 64/71] xfs: set a default CoW extent size of 32 blocks

[Darrick J. Wong]

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 at 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 e91fd84..8c2f9a7 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;
 }
 
 /*