Re: FAILED: patch "[PATCH] block: Fix fsync always failed if once failed" failed to apply to 5.4-stable tree

[Sudip Mukherjee <sudipm.mukherjee@gmail.com>]

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Hi Greg,

On Mon, Jan 24, 2022 at 12:25:00PM +0100, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 5.4-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.

Here is the backport.

--
Regards
Sudip

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From d6a901c1842ff2b9fdcbe19a7e785e4b095f6300 Mon Sep 17 00:00:00 2001
From: Ye Bin <yebin10@huawei.com>
Date: Mon, 29 Nov 2021 09:26:59 +0800
Subject: [PATCH] block: Fix fsync always failed if once failed

commit 8a7518931baa8ea023700987f3db31cb0a80610b upstream.

We do test with inject error fault base on v4.19, after test some time we found
sync /dev/sda always failed.
[root@localhost] sync /dev/sda
sync: error syncing '/dev/sda': Input/output error

scsi log as follows:
[19069.812296] sd 0:0:0:0: [sda] tag#64 Send: scmd 0x00000000d03a0b6b
[19069.812302] sd 0:0:0:0: [sda] tag#64 CDB: Synchronize Cache(10) 35 00 00 00 00 00 00 00 00 00
[19069.812533] sd 0:0:0:0: [sda] tag#64 Done: SUCCESS Result: hostbyte=DID_OK driverbyte=DRIVER_OK
[19069.812536] sd 0:0:0:0: [sda] tag#64 CDB: Synchronize Cache(10) 35 00 00 00 00 00 00 00 00 00
[19069.812539] sd 0:0:0:0: [sda] tag#64 scsi host busy 1 failed 0
[19069.812542] sd 0:0:0:0: Notifying upper driver of completion (result 0)
[19069.812546] sd 0:0:0:0: [sda] tag#64 sd_done: completed 0 of 0 bytes
[19069.812549] sd 0:0:0:0: [sda] tag#64 0 sectors total, 0 bytes done.
[19069.812564] print_req_error: I/O error, dev sda, sector 0

ftrace log as follows:
 rep-306069 [007] .... 19654.923315: block_bio_queue: 8,0 FWS 0 + 0 [rep]
 rep-306069 [007] .... 19654.923333: block_getrq: 8,0 FWS 0 + 0 [rep]
 kworker/7:1H-250   [007] .... 19654.923352: block_rq_issue: 8,0 FF 0 () 0 + 0 [kworker/7:1H]
 <idle>-0     [007] ..s. 19654.923562: block_rq_complete: 8,0 FF () 18446744073709551615 + 0 [0]
 <idle>-0     [007] d.s. 19654.923576: block_rq_complete: 8,0 WS () 0 + 0 [-5]

As 8d6996630c03 introduce 'fq->rq_status', this data only update when 'flush_rq'
reference count isn't zero. If flush request once failed and record error code
in 'fq->rq_status'. If there is no chance to update 'fq->rq_status',then do fsync
will always failed.
To address this issue reset 'fq->rq_status' after return error code to upper layer.

Fixes: 8d6996630c03("block: fix null pointer dereference in blk_mq_rq_timed_out()")
Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20211129012659.1553733-1-yebin10@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
[sudip: adjust context]
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
---
 block/blk-flush.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/block/blk-flush.c b/block/blk-flush.c
index 5aa6fada2259..f66ff1685531 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -222,8 +222,10 @@ static void flush_end_io(struct request *flush_rq, blk_status_t error)
 		return;
 	}
 
-	if (fq->rq_status != BLK_STS_OK)
+	if (fq->rq_status != BLK_STS_OK) {
 		error = fq->rq_status;
+		fq->rq_status = BLK_STS_OK;
+	}
 
 	hctx = flush_rq->mq_hctx;
 	if (!q->elevator) {
-- 
2.30.2