FAILED: patch "[PATCH] btrfs: set cache_block_group_error if we find an error" failed to apply to 4.19-stable tree

The patch below does not apply to the 4.19-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-4.19.y
git checkout FETCH_HEAD
git cherry-pick -x 92fb94b69c6accf1e49fff699640fa0ce03dc910
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023081201-unmoving-diameter-8fa3@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 92fb94b69c6accf1e49fff699640fa0ce03dc910 Mon Sep 17 00:00:00 2001
From: Josef Bacik <[email protected]>
Date: Wed, 2 Aug 2023 09:20:24 -0400
Subject: [PATCH] btrfs: set cache_block_group_error if we find an error

We set cache_block_group_error if btrfs_cache_block_group() returns an error, this is because we could end up not finding space to allocate and mistakenly return -ENOSPC, and which could then abort the transaction with the incorrect errno, and in the case of ENOSPC result in a WARN_ON() that will trip up tests like generic/475.

However there's the case where multiple threads can be racing, one thread gets the proper error, and the other thread doesn't actually call btrfs_cache_block_group(), it instead sees ->cached == BTRFS_CACHE_ERROR. Again the result is the same, we fail to allocate our space and return -ENOSPC. Instead we need to set cache_block_group_error to -EIO in this case to make sure that if we do not make our allocation we get the appropriate error returned back to the caller.

index 911908ea5f6f..f396a9afa403 100644
@@ -4310,8 +4310,11 @@ static noinline int find_free_extent(struct btrfs_root *root,
 			ret = 0;
 		}
 
-		if (unlikely(block_group->cached == BTRFS_CACHE_ERROR))
+		if (unlikely(block_group->cached == BTRFS_CACHE_ERROR)) {
+			if (!cache_block_group_error)
+				cache_block_group_error = -EIO;
 			goto loop;
+		}
 
 		if (!find_free_extent_check_size_class(ffe_ctl, block_group))
 			goto loop;