btrfs: add helper to replace extent map range with a new extent map

We have several places that need to drop all the extent maps in a given
file range and then add a new extent map for that range. Currently they
call btrfs_drop_extent_map_range() to delete all extent maps in the range
and then keep trying to add the new extent map in a loop that keeps
retrying while the insertion of the new extent map fails with -EEXIST.

So instead of repeating this logic, add a helper to extent_map.c that
does these steps and name it btrfs_replace_extent_map_range(). Also add
a comment about why the retry loop is necessary.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 3 insertions, 11 deletions

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 2faf90a7e9ff..666a37a0ee89 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -2890,7 +2890,6 @@ static noinline_for_stack int prealloc_file_extent_cluster(
 static noinline_for_stack int setup_relocation_extent_mapping(struct inode *inode,
 				u64 start, u64 end, u64 block_start)
 {
-	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
 	struct extent_map *em;
 	int ret = 0;
 
@@ -2905,17 +2904,10 @@ static noinline_for_stack int setup_relocation_extent_mapping(struct inode *inod
 	set_bit(EXTENT_FLAG_PINNED, &em->flags);
 
 	lock_extent(&BTRFS_I(inode)->io_tree, start, end, NULL);
-	while (1) {
-		write_lock(&em_tree->lock);
-		ret = add_extent_mapping(em_tree, em, 0);
-		write_unlock(&em_tree->lock);
-		if (ret != -EEXIST) {
-			free_extent_map(em);
-			break;
-		}
-		btrfs_drop_extent_map_range(BTRFS_I(inode), start, end, false);
-	}
+	ret = btrfs_replace_extent_map_range(BTRFS_I(inode), em, false);
 	unlock_extent(&BTRFS_I(inode)->io_tree, start, end, NULL);
+	free_extent_map(em);
+
 	return ret;
 }