btrfs: don't get an EINTR during drop_snapshot for reloc

This was partially fixed by f3e3d9cc3525 ("btrfs: avoid possible signal
interruption of btrfs_drop_snapshot() on relocation tree"), however it
missed a spot when we restart a trans handle because we need to end the
transaction.  The fix is the same, simply use btrfs_join_transaction()
instead of btrfs_start_transaction() when deleting reloc roots.

Fixes: f3e3d9cc3525 ("btrfs: avoid possible signal interruption of btrfs_drop_snapshot() on relocation tree")
CC: stable@vger.kernel.org # 5.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index d79b8369e6aafedfae71c0a7dcb1299c6c655aee..30b1a630dc2f88b13d1612d5ec8f1dc4cf3f4ad7 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5549,7 +5549,15 @@ int btrfs_drop_snapshot(struct btrfs_root *root, int update_ref, int for_reloc)
                                goto out_free;
                        }
 
-                       trans = btrfs_start_transaction(tree_root, 0);
+                      /*
+                       * Use join to avoid potential EINTR from transaction
+                       * start. See wait_reserve_ticket and the whole
+                       * reservation callchain.
+                       */
+                       if (for_reloc)
+                               trans = btrfs_join_transaction(tree_root);
+                       else
+                               trans = btrfs_start_transaction(tree_root, 0);
                        if (IS_ERR(trans)) {
                                err = PTR_ERR(trans);
                                goto out_free;