linux-kernel - Re: [PATCH 4/5] block: move queue enter logic into blk_mq_submit

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Date:   Thu, 11 Nov 2021 23:23:51 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Christoph Hellwig <hch@...radead.org>,
        linux-block@...r.kernel.org,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/5] block: move queue enter logic into
 blk_mq_submit_bio()

Hi Geert,

On Thu, Nov 11, 2021 at 03:51:28PM +0100, Geert Uytterhoeven wrote:
> Hi Ming,
> 
> On Thu, Nov 11, 2021 at 2:45 PM Ming Lei <ming.lei@...hat.com> wrote:
> > On Thu, Nov 11, 2021 at 01:58:38PM +0100, Geert Uytterhoeven wrote:
> > > On Thu, 4 Nov 2021, Jens Axboe wrote:
> > > > On 11/4/21 1:04 PM, Christoph Hellwig wrote:
> > > > > On Thu, Nov 04, 2021 at 01:02:54PM -0600, Jens Axboe wrote:
> > > > > > On 11/4/21 12:52 PM, Christoph Hellwig wrote:
> > > > > > > Looks good:
> > > > > > >
> > > > > > > Reviewed-by: Christoph Hellwig <hch@....de>
> > > > > >
> > > > > > So these two are now:
> > > > > >
> > > > > > https://git.kernel.dk/cgit/linux-block/commit/?h=for-5.16/block&id=c98cb5bbdab10d187aff9b4e386210eb2332af96
> > > > > >
> > > > > > which is the one I sent here, and then the next one gets cleaned up to
> > > > > > remove that queue enter helper:
> > > > > >
> > > > > > https://git.kernel.dk/cgit/linux-block/commit/?h=for-5.16/block&id=7f930eb31eeb07f1b606b3316d8ad3ab6a92905b
> > > > > >
> > > > > > Can I add your reviewed-by to this last one as well? Only change is the
> > > > > > removal of blk_mq_enter_queue() and the weird construct there, it's just
> > > > > > bio_queue_enter() now.
> > > > >
> > > > > Sure.
> > > >
> > > > Thanks, prematurely already done, as you could tell :-)
> > >
> > > The updated version is now commit 900e080752025f00 ("block: move queue
> > > enter logic into blk_mq_submit_bio()") in Linus' tree.
> > >
> > > I have bisected failures on m68k/atari (on ARAnyM, using nfhd as the
> > > root device) to this commit, e.g.:
> > >
> > >     sd 0:0:0:0: [sda] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_OK cmd_age=0s
> > >     sd 0:0:0:0: [sda] tag#0 Sense Key : Illegal Request [current]
> > >     sd 0:0:0:0: [sda] tag#0 Add. Sense: Invalid field in cdb
> > >     sd 0:0:0:0: [sda] tag#0 CDB: Write(10) 2a 08 00 00 00 01 00 00 08 00
> > >     critical target error, dev sda, sector 1 op 0x1:(WRITE) flags 0x20800 phys_seg 1 prio class 0
> > >     Buffer I/O error on dev sda1, logical block 0, lost sync page write
> > >
> > >     EXT4-fs (sda1): I/O error while writing superblock
> > >     sd 0:0:0:0: [sda] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_OK cmd_age=0s
> > >     sd 0:0:0:0: [sda] tag#0 Sense Key : Illegal Request [current]
> > >     sd 0:0:0:0: [sda] tag#0 Add. Sense: Invalid field in cdb
> > >     sd 0:0:0:0: [sda] tag#0 CDB: Write(10) 2a 08 00 00 00 01 00 00 08 00
> > >     critical target error, dev sda, sector 1 op 0x1:(WRITE) flags 0x20800 phys_seg 1 prio class 0
> > >     Buffer I/O error on dev sda1, logical block 0, lost sync page write
> > >     EXT4-fs (sda1): I/O error while writing superblock
> > >
> > > This may happen either when mounting the root file system (leading to an
> > > unable to mount root fs panic), or later (leading to a read-only
> > > rootfs).
> >
> > BTW, today I just found that hang in blk_mq_freeze_queue_wait() is
> > caused by commit 900e080752025f00, and the following patch can fix it:
> >
> > - blk-mq: don't grab ->q_usage_counter in blk_mq_sched_bio_merge
> >
> > https://lore.kernel.org/linux-block/20211111085650.GA476@lst.de/T/#m759b88fda094a65ebf29bc81b780967cdaf9cf28
> >
> > Maybe you can try the above patch.
> 
> Thanks! I have applied both patches, but it doesn't make a difference.

Thanks for your test!

Can you try the following patch?


diff --git a/block/blk-mq.c b/block/blk-mq.c
index f511db395c7f..a5ab2f2e9f67 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2517,7 +2517,6 @@ static struct request *blk_mq_get_new_requests(struct request_queue *q,
 	struct blk_mq_alloc_data data = {
 		.q		= q,
 		.nr_tags	= 1,
-		.cmd_flags	= bio->bi_opf,
 	};
 	struct request *rq;
 
@@ -2525,6 +2524,7 @@ static struct request *blk_mq_get_new_requests(struct request_queue *q,
 		return NULL;
 	if (unlikely(!submit_bio_checks(bio)))
 		goto put_exit;
+	data.cmd_flags	= bio->bi_opf;
 	if (blk_mq_attempt_bio_merge(q, bio, nsegs, same_queue_rq))
 		goto put_exit;
 

-- 
Ming