xfs: set a default CoW extent size of 32 blocks
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>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 89e6441..3332fb6 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -80,7 +80,8 @@
/*
* 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),
+ * use the default size.
*/
xfs_extlen_t
xfs_get_cowextsz_hint(
@@ -93,9 +94,10 @@
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 XFS_DEFAULT_COWEXTSZ_HINT;
+ return a;
}
/*
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 6d63dc0..f14c1de 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -490,4 +490,7 @@
extern struct kmem_zone *xfs_inode_zone;
+/* The default CoW extent size hint. */
+#define XFS_DEFAULT_COWEXTSZ_HINT 32
+
#endif /* __XFS_INODE_H__ */
