linux-kernel - [PATCH 5.16 0181/1017] btrfs: extend locking to all space

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Message-Id: <20220405070359.610075798@linuxfoundation.org>
Date:   Tue,  5 Apr 2022 09:18:14 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Johannes Thumshirn <johannes.thumshirn@....com>,
        Josef Bacik <josef@...icpanda.com>,
        Niels Dossche <niels.dossche@...nt.be>,
        Niels Dossche <dossche.niels@...il.com>,
        David Sterba <dsterba@...e.com>
Subject: [PATCH 5.16 0181/1017] btrfs: extend locking to all space_info members accesses

From: Niels Dossche <dossche.niels@...il.com>

commit 06bae876634ebf837ba70ea3de532b288326103d upstream.

bytes_pinned is always accessed under space_info->lock, except in
btrfs_preempt_reclaim_metadata_space, however the other members are
accessed under that lock. The reserved member of the rsv's are also
partially accessed under a lock and partially not. Move all these
accesses into the same lock to ensure consistency.

This could potentially race and lead to a flush instead of a commit but
it's not a big problem as it's only for preemptive flush.

CC: stable@...r.kernel.org # 5.15+
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@....com>
Reviewed-by: Josef Bacik <josef@...icpanda.com>
Signed-off-by: Niels Dossche <niels.dossche@...nt.be>
Signed-off-by: Niels Dossche <dossche.niels@...il.com>
Reviewed-by: David Sterba <dsterba@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/btrfs/space-info.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -1059,7 +1059,6 @@ static void btrfs_preempt_reclaim_metada
 			trans_rsv->reserved;
 		if (block_rsv_size < space_info->bytes_may_use)
 			delalloc_size = space_info->bytes_may_use - block_rsv_size;
-		spin_unlock(&space_info->lock);
 
 		/*
 		 * We don't want to include the global_rsv in our calculation,
@@ -1090,6 +1089,8 @@ static void btrfs_preempt_reclaim_metada
 			flush = FLUSH_DELAYED_REFS_NR;
 		}
 
+		spin_unlock(&space_info->lock);
+
 		/*
 		 * We don't want to reclaim everything, just a portion, so scale
 		 * down the to_reclaim by 1/4.  If it takes us down to 0,