FAILED: patch "[PATCH] btrfs: fix space cache inconsistency after error loading it" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 0004ff15ea26015a0a3a6182dca3b9d1df32e2b7
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023051358-embattled-detest-37ff@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

0004ff15ea26 ("btrfs: fix space cache inconsistency after error loading it from disk") fa598b069640 ("btrfs: remove recalc_thresholds from free space ops") cd79909bc7cd ("btrfs: load free space cache into a temporary ctl")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 0004ff15ea26015a0a3a6182dca3b9d1df32e2b7 Mon Sep 17 00:00:00 2001
From: Filipe Manana <[email protected]>
Date: Thu, 4 May 2023 12:04:18 +0100
Subject: [PATCH] btrfs: fix space cache inconsistency after error loading it
from disk

When loading a free space cache from disk, at __load_free_space_cache(), if we fail to insert a bitmap entry, we still increment the number of total bitmaps in the btrfs_free_space_ctl structure, which is incorrect since we failed to add the bitmap entry. On error we then empty the cache by calling __btrfs_remove_free_space_cache(), which will result in getting the total bitmaps counter set to 1.

A failure to load a free space cache is not critical, so if a failure happens we just rebuild the cache by scanning the extent tree, which happens at block-group.c:caching_thread(). Yet the failure will result in having the total bitmaps of the btrfs_free_space_ctl always bigger by 1 then the number of bitmap entries we have. So fix this by having the total bitmaps counter be incremented only if we successfully added the bitmap entry.

index d84cef89cdff..cf98a3c05480 100644
@@ -870,15 +870,16 @@ static int __load_free_space_cache(struct btrfs_root *root, struct inode *inode,
 			}
 			spin_lock(&ctl->tree_lock);
 			ret = link_free_space(ctl, e);
-			ctl->total_bitmaps++;
-			recalculate_thresholds(ctl);
-			spin_unlock(&ctl->tree_lock);
 			if (ret) {
+				spin_unlock(&ctl->tree_lock);
 				btrfs_err(fs_info,
 					"Duplicate entries in free space cache, dumping");
 				kmem_cache_free(btrfs_free_space_cachep, e);
 				goto free_cache;
 			}
+			ctl->total_bitmaps++;
+			recalculate_thresholds(ctl);
+			spin_unlock(&ctl->tree_lock);
 			list_add_tail(&e->list, &bitmaps);
 		}