From: Jens Axboe <axboe@kernel.dk>
To: James Bottomley <James.Bottomley@HansenPartnership.com>,
Mikael Pettersson <mikpelinux@gmail.com>
Cc: Linux SPARC Kernel Mailing List <sparclinux@vger.kernel.org>,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [5.0-rc5 regression] "scsi: kill off the legacy IO path" causes 5 minute delay during boot on Sun Blade 2500
Date: Sun, 10 Feb 2019 09:05:34 -0700 [thread overview]
Message-ID: <3380ed8e-ae02-96f2-142b-7cce09459df8@kernel.dk> (raw)
In-Reply-To: <1549813472.4142.3.camel@HansenPartnership.com>
On 2/10/19 8:44 AM, James Bottomley wrote:
> On Sun, 2019-02-10 at 10:17 +0100, Mikael Pettersson wrote:
>> On Sat, Feb 9, 2019 at 7:19 PM James Bottomley
>> <James.Bottomley@hansenpartnership.com> wrote:
> [...]
>>> I think the reason for this is that the block mq path doesn't feed
>>> the kernel entropy pool correctly, hence the need to install an
>>> entropy gatherer for systems that don't have other good random
>>> number sources.
>>
>> That does sound plausible, I admit I didn't even consider the
>> possibility that the old block I/O path also was an entropy source.
>
> In theory, the new one should be as well since the rotational entropy
> collector is on the SCSI completion path. I'd seen the same problem
> but had assumed it was something someone had done to our internal
> entropy pool and thus hadn't bisected it.
The difference is that the old stack included ADD_RANDOM by default,
so this check:
if (blk_queue_add_random(q))
add_disk_randomness(req->rq_disk);
in scsi_end_request() would be true, and we'd add the randomness. For
sd, it seems to set it just fine for non-rotational drives. Could this
be because other devices don't? Maybe the below makes a difference.
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 6d65ac584eba..60e029911755 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1881,6 +1881,7 @@ struct request_queue *scsi_mq_alloc_queue(struct scsi_device *sdev)
sdev->request_queue->queuedata = sdev;
__scsi_init_queue(sdev->host, sdev->request_queue);
blk_queue_flag_set(QUEUE_FLAG_SCSI_PASSTHROUGH, sdev->request_queue);
+ blk_queue_flag_set(QUEUE_FLAG_ADD_RANDOM, sdev->request_queue);
return sdev->request_queue;
}
--
Jens Axboe
next prev parent reply other threads:[~2019-02-10 16:05 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-09 17:04 [5.0-rc5 regression] "scsi: kill off the legacy IO path" causes 5 minute delay during boot on Sun Blade 2500 Mikael Pettersson
2019-02-09 18:19 ` James Bottomley
2019-02-10 9:17 ` Mikael Pettersson
2019-02-10 15:44 ` James Bottomley
2019-02-10 16:05 ` Jens Axboe [this message]
2019-02-10 16:25 ` James Bottomley
2019-02-10 16:35 ` Jens Axboe
2019-02-11 15:25 ` James Bottomley
2019-02-11 15:28 ` Jens Axboe
2019-02-11 15:42 ` James Bottomley
2019-02-11 15:46 ` Jens Axboe
2019-02-11 16:28 ` James Bottomley
2019-02-11 16:31 ` Jens Axboe
2019-02-12 2:13 ` James Bottomley
2019-02-12 2:50 ` Jens Axboe
2019-02-12 3:37 ` Elliott, Robert (Persistent Memory)
2019-02-12 4:15 ` James Bottomley
2019-02-12 15:24 ` James Bottomley
2019-02-12 15:27 ` Jens Axboe
2019-02-14 18:35 ` Mikael Pettersson
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