Patch "btrfs: do not BUG_ON() on tree mod log failure at balance_level()" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    btrfs: do not BUG_ON() on tree mod log failure at balance_level()

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     btrfs-do-not-bug_on-on-tree-mod-log-failure-at-balan.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 0d68eefaee4ab5908c73b86de4a9ec369ea322d4
Author: Filipe Manana <fdmanana@xxxxxxxx>
Date:   Thu Jun 8 11:27:41 2023 +0100

    btrfs: do not BUG_ON() on tree mod log failure at balance_level()
    
    [ Upstream commit 39020d8abc7ec62c4de9b260e3d10d4a1c2478ce ]
    
    At balance_level(), instead of doing a BUG_ON() in case we fail to record
    tree mod log operations, do a transaction abort and return the error to
    the callers. There's really no need for the BUG_ON() as we can release
    all resources in this context, and we have to abort because other future
    tree searches that use the tree mod log (btrfs_search_old_slot()) may get
    inconsistent results if other operations modify the tree after that
    failure and before the tree mod log based search.
    
    CC: stable@xxxxxxxxxxxxxxx # 5.4+
    Reviewed-by: Qu Wenruo <wqu@xxxxxxxx>
    Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
    Reviewed-by: David Sterba <dsterba@xxxxxxxx>
    Signed-off-by: David Sterba <dsterba@xxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 1a19354382b2b..8b57d691cfae8 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -912,7 +912,12 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
 		}
 
 		ret = btrfs_tree_mod_log_insert_root(root->node, child, true);
-		BUG_ON(ret < 0);
+		if (ret < 0) {
+			btrfs_tree_unlock(child);
+			free_extent_buffer(child);
+			btrfs_abort_transaction(trans, ret);
+			goto enospc;
+		}
 		rcu_assign_pointer(root->node, child);
 
 		add_root_to_dirty_list(root);
@@ -994,7 +999,10 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
 			btrfs_node_key(right, &right_key, 0);
 			ret = btrfs_tree_mod_log_insert_key(parent, pslot + 1,
 					BTRFS_MOD_LOG_KEY_REPLACE, GFP_NOFS);
-			BUG_ON(ret < 0);
+			if (ret < 0) {
+				btrfs_abort_transaction(trans, ret);
+				goto enospc;
+			}
 			btrfs_set_node_key(parent, &right_key, pslot + 1);
 			btrfs_mark_buffer_dirty(parent);
 		}
@@ -1040,7 +1048,10 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
 		btrfs_node_key(mid, &mid_key, 0);
 		ret = btrfs_tree_mod_log_insert_key(parent, pslot,
 				BTRFS_MOD_LOG_KEY_REPLACE, GFP_NOFS);
-		BUG_ON(ret < 0);
+		if (ret < 0) {
+			btrfs_abort_transaction(trans, ret);
+			goto enospc;
+		}
 		btrfs_set_node_key(parent, &mid_key, pslot);
 		btrfs_mark_buffer_dirty(parent);
 	}