linux-kernel - Re: [PATCH BUGFIX] block, bfq: postpone rq preparation to insert or merge

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Message-Id: <223CABEA-71E0-426F-A4AB-17BA8437C978@linaro.org>
Date:   Sun, 6 May 2018 09:42:51 +0200
From:   Paolo Valente <paolo.valente@...aro.org>
To:     Mike Galbraith <efault@....de>
Cc:     Jens Axboe <axboe@...nel.dk>,
        linux-block <linux-block@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Mark Brown <broonie@...nel.org>, linus.walleij@...aro.org,
        bfq-iosched@...glegroups.com, oleksandr@...alenko.name
Subject: Re: [PATCH BUGFIX] block, bfq: postpone rq preparation to insert or
 merge



> Il giorno 05 mag 2018, alle ore 16:56, Mike Galbraith <efault@....de> ha scritto:
> 
> On Sat, 2018-05-05 at 12:39 +0200, Paolo Valente wrote:
>> 
>> BTW, if you didn't run out of patience with this permanent issue yet,
>> I was thinking of two o three changes to retry to trigger your failure
>> reliably.
> 
> Sure, fire away, I'll happily give the annoying little bugger
> opportunities to show its tender belly.

I've attached a compressed patch (to avoid possible corruption from my
mailer).  I'm little confident, but no pain, no gain, right?

If possible, apply this patch on top of the fix I proposed in this
thread, just to eliminate possible further noise. Finally, the
patch content follows.

Hoping for a stroke of luck,
Paolo

diff --git a/block/bfq-mq-iosched.c b/block/bfq-mq-iosched.c
index 118f319af7c0..6662efe29b69 100644
--- a/block/bfq-mq-iosched.c
+++ b/block/bfq-mq-iosched.c
@@ -525,8 +525,13 @@ static void bfq_limit_depth(unsigned int op, struct blk_mq_alloc_data *data)
        if (unlikely(bfqd->sb_shift != bt->sb.shift))
                bfq_update_depths(bfqd, bt);
 
+#if 0
        data->shallow_depth =
                bfqd->word_depths[!!bfqd->wr_busy_queues][op_is_sync(op)];
+#else
+       data->shallow_depth = 1;
+#endif
+
 
        bfq_log(bfqd, "wr_busy %d sync %d depth %u",
                        bfqd->wr_busy_queues, op_is_sync(op),


> 
> 	-Mike
>