Btrfs: fix merge delalloc logic

My patch to properly count outstanding extents wrt MAX_EXTENT_SIZE introduced a regression when re-dirtying already dirty areas. We have logic in split to make sure we are taking the largest space into account but didn't have it for merge, so it was sometimes making us think we were turning a tiny extent into a huge extent, when in reality we already had a huge extent and needed to use the other side in our logic. This fixes the regression that was reported by a user on list. Thanks, Reported-by: Markus Trippelsdorf <[email protected]> Signed-off-by: Josef Bacik <[email protected]> Signed-off-by: Chris Mason <[email protected]>
cluon · Mar 13, 2015 · 8461a3d · 8461a3d
1 parent 48da5f0
commit 8461a3d
Showing 1 changed file with 6 additions and 1 deletion.
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
@@ -1592,7 +1592,12 @@ static void btrfs_merge_extent_hook(struct inode *inode,
 		return;
 
 	old_size = other->end - other->start + 1;
-	new_size = old_size + (new->end - new->start + 1);
+	if (old_size < (new->end - new->start + 1))
+		old_size = (new->end - new->start + 1);
+	if (new->start > other->start)
+		new_size = new->end - other->start + 1;
+	else
+		new_size = other->end - new->start + 1;
 
 	/* we're not bigger than the max, unreserve the space and go */
 	if (new_size <= BTRFS_MAX_EXTENT_SIZE) {