releases/6.1.8/btrfs-do-not-abort-transaction-on-failure-to-write-log-tree-when-syncing-log.patch

From 16199ad9eb6db60a6b10794a09fc1ac6d09312ff Mon Sep 17 00:00:00 2001
From: Filipe Manana <fdmanana@suse.com>
Date: Tue, 10 Jan 2023 14:56:37 +0000
Subject: btrfs: do not abort transaction on failure to write log tree when syncing log

From: Filipe Manana <fdmanana@suse.com>

commit 16199ad9eb6db60a6b10794a09fc1ac6d09312ff upstream.

When syncing the log, if we fail to write log tree extent buffers, we mark
the log for a full commit and abort the transaction. However we don't need
to abort the transaction, all we really need to do is to make sure no one
can commit a superblock pointing to new log tree roots. Just because we
got a failure writing extent buffers for a log tree, it does not mean we
will also fail to do a transaction commit.

One particular case is if due to a bug somewhere, when writing log tree
extent buffers, the tree checker detects some corruption and the writeout
fails because of that. Aborting the transaction can be very disruptive for
a user, specially if the issue happened on a root filesystem. One example
is the scenario in the Link tag below, where an isolated corruption on log
tree leaves was causing transaction aborts when syncing the log.

Link: https://lore.kernel.org/linux-btrfs/ae169fc6-f504-28f0-a098-6fa6a4dfb612@leemhuis.info/
CC: stable@vger.kernel.org # 5.15+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/btrfs/disk-io.c  |    9 ++++++++-
 fs/btrfs/tree-log.c |    2 --
 2 files changed, 8 insertions(+), 3 deletions(-)

--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -344,7 +344,14 @@ error:
 	btrfs_print_tree(eb, 0);
 	btrfs_err(fs_info, "block=%llu write time tree block corruption detected",
 		  eb->start);
-	WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG));
+	/*
+	 * Be noisy if this is an extent buffer from a log tree. We don't abort
+	 * a transaction in case there's a bad log tree extent buffer, we just
+	 * fallback to a transaction commit. Still we want to know when there is
+	 * a bad log tree extent buffer, as that may signal a bug somewhere.
+	 */
+	WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG) ||
+		btrfs_header_owner(eb) == BTRFS_TREE_LOG_OBJECTID);
 	return ret;
 }
 
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -3011,7 +3011,6 @@ int btrfs_sync_log(struct btrfs_trans_ha
 		ret = 0;
 	if (ret) {
 		blk_finish_plug(&plug);
-		btrfs_abort_transaction(trans, ret);
 		btrfs_set_log_full_commit(trans);
 		mutex_unlock(&root->log_mutex);
 		goto out;
@@ -3143,7 +3142,6 @@ int btrfs_sync_log(struct btrfs_trans_ha
 		goto out_wake_log_root;
 	} else if (ret) {
 		btrfs_set_log_full_commit(trans);
-		btrfs_abort_transaction(trans, ret);
 		mutex_unlock(&log_root_tree->log_mutex);
 		goto out_wake_log_root;
 	}