Re: [PATCH -next] block: Fix fsync always failed if once failed

[Ming Lei <ming.lei@redhat.com>]

On Mon, Nov 29, 2021 at 09:26:59AM +0800, Ye Bin wrote:
> 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>
> ---
>  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 902e80e48e4a..8b43088d41f2 100644
> --- a/block/blk-flush.c
> +++ b/block/blk-flush.c
> @@ -242,8 +242,10 @@ static void flush_end_io(struct request *flush_rq, blk_status_t error)
>  	 * avoiding use-after-free.
>  	 */
>  	WRITE_ONCE(flush_rq->state, MQ_RQ_IDLE);
> -	if (fq->rq_status != BLK_STS_OK)
> +	if (fq->rq_status != BLK_STS_OK) {
>  		error = fq->rq_status;
> +		fq->rq_status = BLK_STS_OK;
> +	}

Looks fine,

Reviewed-by: Ming Lei <ming.lei@redhat.com>


Thanks, 
Ming