linux-kernel - [PATCH v3 2/2] fscache: Use clear_and_wake_up_bit() in fscache_create_volume

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Message-Id: <20230113115211.2895845-3-houtao@huaweicloud.com>
Date:   Fri, 13 Jan 2023 19:52:11 +0800
From:   Hou Tao <houtao@...weicloud.com>
To:     linux-cachefs@...hat.com
Cc:     David Howells <dhowells@...hat.com>,
        Jeff Layton <jlayton@...nel.org>, linux-erofs@...ts.ozlabs.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jingbo Xu <jefflexu@...ux.alibaba.com>, houtao1@...wei.com
Subject: [PATCH v3 2/2] fscache: Use clear_and_wake_up_bit() in fscache_create_volume_work()

From: Hou Tao <houtao1@...wei.com>

fscache_create_volume_work() uses wake_up_bit() to wake up the processes
which are waiting for the completion of volume creation. According to
comments in wake_up_bit() and waitqueue_active(), an extra smp_mb() is
needed to guarantee the memory order between FSCACHE_VOLUME_CREATING
flag and waitqueue_active() before invoking wake_up_bit().

Fixing it by using clear_and_wake_up_bit() to add the missing memory
barrier.

Reviewed-by: Jingbo Xu <jefflexu@...ux.alibaba.com>
Signed-off-by: Hou Tao <houtao1@...wei.com>
---
 fs/fscache/volume.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/fscache/volume.c b/fs/fscache/volume.c
index 903af9d85f8b..cdf991bdd9de 100644
--- a/fs/fscache/volume.c
+++ b/fs/fscache/volume.c
@@ -280,8 +280,7 @@ static void fscache_create_volume_work(struct work_struct *work)
 	fscache_end_cache_access(volume->cache,
 				 fscache_access_acquire_volume_end);
 
-	clear_bit_unlock(FSCACHE_VOLUME_CREATING, &volume->flags);
-	wake_up_bit(&volume->flags, FSCACHE_VOLUME_CREATING);
+	clear_and_wake_up_bit(FSCACHE_VOLUME_CREATING, &volume->flags);
 	fscache_put_volume(volume, fscache_volume_put_create_work);
 }
 
-- 
2.29.2