From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Johannes Thumshirn <johannes.thumshirn@wdc.com>,
	Filipe Manana <fdmanana@suse.com>,
	David Sterba <dsterba@suse.com>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.18 603/641] btrfs: reduce block group critical section in btrfs_free_reserved_bytes()
Date: Tue, 24 Feb 2026 17:25:29 -0800
Message-ID: <20260225012403.126415990@linuxfoundation.org>
In-Reply-To: <20260225012348.915798704@linuxfoundation.org>
References: <20260225012348.915798704@linuxfoundation.org>
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6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Filipe Manana <fdmanana@suse.com>

[ Upstream commit 8b6fa164ab59f9e3f24e627fe09a0234783e7a8b ]

There's no need to update the space_info fields (bytes_reserved,
max_extent_size, bytes_readonly, bytes_zone_unusable) while holding the
block group's spinlock. So move those updates to happen after we unlock
the block group (and while holding the space_info locked of course), so
that all we do under the block group's critical section is to update the
block group itself.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Stable-dep-of: 5870ec7c8fe5 ("btrfs: reset block group size class when it becomes empty")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/btrfs/block-group.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 035b04e7658d1..144868f02e2aa 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -3859,21 +3859,24 @@ void btrfs_free_reserved_bytes(struct btrfs_block_group *cache, u64 num_bytes,
 			       bool is_delalloc)
 {
 	struct btrfs_space_info *space_info = cache->space_info;
+	bool bg_ro;
 
 	spin_lock(&space_info->lock);
 	spin_lock(&cache->lock);
-	if (cache->ro)
+	bg_ro = cache->ro;
+	cache->reserved -= num_bytes;
+	if (is_delalloc)
+		cache->delalloc_bytes -= num_bytes;
+	spin_unlock(&cache->lock);
+
+	if (bg_ro)
 		space_info->bytes_readonly += num_bytes;
 	else if (btrfs_is_zoned(cache->fs_info))
 		space_info->bytes_zone_unusable += num_bytes;
-	cache->reserved -= num_bytes;
+
 	space_info->bytes_reserved -= num_bytes;
 	space_info->max_extent_size = 0;
 
-	if (is_delalloc)
-		cache->delalloc_bytes -= num_bytes;
-	spin_unlock(&cache->lock);
-
 	btrfs_try_granting_tickets(space_info);
 	spin_unlock(&space_info->lock);
 }
-- 
2.51.0