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Wed, 22 Apr 2026 14:45:43 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id RCImChff6GlSdQAAD6G6ig (envelope-from ); Wed, 22 Apr 2026 14:45:43 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 7C922A0B44; Wed, 22 Apr 2026 16:45:42 +0200 (CEST) From: Jan Kara To: Christian Brauner Cc: , Jan Kara , Ruikai Peng Subject: [PATCH] fs: Handle multiply claimed blocks more gracefully with mmb Date: Wed, 22 Apr 2026 16:45:30 +0200 Message-ID: <20260422144529.20279-2-jack@suse.cz> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1214; i=jack@suse.cz; h=from:subject; bh=Z0/ctn5eiQgUy6gVc+bq7KSdT7JCHjyqaEbqkMgHfSU=; b=owEBbQGS/pANAwAIAZydqgc/ZEDZAcsmYgBp6N8Jumm5ESDaUn9Axk8CiI7xu51WijaGTXNda ESZ9dxQGMKJATMEAAEIAB0WIQSrWdEr1p4yirVVKBycnaoHP2RA2QUCaejfCQAKCRCcnaoHP2RA 2QL5CADj3UQUd/FqPTI0Z4/wHaSGoX2oDaOvotYR9u2MaJXnBf6gRtKN1LlQL+fK8IFZ9DWPZBX tYjuAcy23cAFXirwHGEkipI0i9GJw07fNl6laXZ0xB1bXHemzvSPgqXwQq5tycSphbpGpbFibw2 tsPMX6WNiVZj3kRe4ym16heQpHIdaov2A6AR7t0yxvyHhNHQbT+i/4p4a3fXOvssZz0Fyf4tXQX puz3GGY+pS2Gjj0suprjoQaizz5O5JyV71yiu+XQ6JnEFJi5f/4x9R41v1XR3AV0n/nM0elx1+2 ZdrhMn3DJ0Pvee5isK71cibNkKl9Pqmi9AWrHOePeMQEQkRf X-Developer-Key: i=jack@suse.cz; 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This can lead to a corruption of mmb linked list. Handle that situation gracefully (at least from mmb POV) by serializing on setting bh->b_mmb. Reported-by: Ruikai Peng Signed-off-by: Jan Kara --- fs/buffer.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/fs/buffer.c b/fs/buffer.c index d6e062c42a8d..35e7b63576cf 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -719,8 +719,15 @@ void mmb_mark_buffer_dirty(struct buffer_head *bh, mark_buffer_dirty(bh); if (!bh->b_mmb) { spin_lock(&mmb->lock); + /* + * For a corrupted filesystem with multiply claimed blocks this + * can fail. Avoid corrupting the linked list in that case. + */ + if (!cmpxchg(&bh->b_mmb, NULL, mmb)) { + spin_unlock(&mmb->lock); + return; + } list_move_tail(&bh->b_assoc_buffers, &mmb->list); - bh->b_mmb = mmb; spin_unlock(&mmb->lock); } } -- 2.51.0