[PATCH 4.18 341/350] btrfs: dont use ctl->free_space for max_extent_size

[Greg Kroah-Hartman]

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Josef Bacik <jbacik@xxxxxx>

commit fb5c39d7a887108087de6ff93d3f326b01b4ef41 upstream.

max_extent_size is supposed to be the largest contiguous range for the
space info, and ctl->free_space is the total free space in the block
group.  We need to keep track of these separately and _only_ use the
max_free_space if we don't have a max_extent_size, as that means our
original request was too large to search any of the block groups for and
therefore wouldn't have a max_extent_size set.

CC: stable@xxxxxxxxxxxxxxx # 4.14+
Reviewed-by: Filipe Manana <fdmanana@xxxxxxxx>
Signed-off-by: Josef Bacik <jbacik@xxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/btrfs/extent-tree.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -7409,6 +7409,7 @@ static noinline int find_free_extent(str
 	struct btrfs_block_group_cache *block_group = NULL;
 	u64 search_start = 0;
 	u64 max_extent_size = 0;
+	u64 max_free_space = 0;
 	u64 empty_cluster = 0;
 	struct btrfs_space_info *space_info;
 	int loop = 0;
@@ -7704,8 +7705,8 @@ unclustered_alloc:
 			spin_lock(&ctl->tree_lock);
 			if (ctl->free_space <
 			    num_bytes + empty_cluster + empty_size) {
-				if (ctl->free_space > max_extent_size)
-					max_extent_size = ctl->free_space;
+				max_free_space = max(max_free_space,
+						     ctl->free_space);
 				spin_unlock(&ctl->tree_lock);
 				goto loop;
 			}
@@ -7874,6 +7875,8 @@ loop:
 	}
 out:
 	if (ret == -ENOSPC) {
+		if (!max_extent_size)
+			max_extent_size = max_free_space;
 		spin_lock(&space_info->lock);
 		space_info->max_extent_size = max_extent_size;
 		spin_unlock(&space_info->lock);