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From: Ming Lei <tom.leiming@gmail.com>
To: Keith Busch <kbusch@kernel.org>
Cc: Tokunori Ikegami <ikegami.t@gmail.com>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
	Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>
Subject: Re: [PATCH] block, nvme: Increase max segments parameter setting value
Date: Sat, 28 Mar 2020 16:28:51 +0800	[thread overview]
Message-ID: <CACVXFVNY++56icyHB4+-aGjRXWZ5B7WdK4z-N336u0+v6sDhbQ@mail.gmail.com> (raw)
In-Reply-To: <20200328031334.GA18429@keith-busch>

On Sat, Mar 28, 2020 at 11:13 AM Keith Busch <kbusch@kernel.org> wrote:
>
> On Sat, Mar 28, 2020 at 10:11:57AM +0800, Ming Lei wrote:
> > On Sat, Mar 28, 2020 at 2:18 AM Keith Busch <kbusch@kernel.org> wrote:
> > >
> > > This is actually even more confusing. We do not support 256MB transfers
> > > within a single command in the pci nvme driver anymore. The max is 4MB,
> > > so I don't see how increasing the max segments will help: you should be
> > > hitting the 'max_sectors' limit if you don't hit the segment limit first.
> >
> > That looks a bug for passthrough req, because 'max_sectors' limit is only
> > checked in bio_add_pc_page(), not done in blk_rq_append_bio(), something
> > like the following seems required:
>
> Shouldn't bio_map_user_iov() or bio_copy_user_iov() have caught the
> length limit before proceeding to blk_rq_append_bio()?

Actually the limit should be caught earlier in bio_add_pc_page(), that requires
to pass 'rq' in, then one perfect passthrough bio can be made before
appending to rq.

Not only max sector limit, max segments & virt_boundary should be checked
in request wide too.

So far, only lightnvm calls bio_add_pc_page() before allocating
request, and that is
the 1st bio, so NULL rq can be passed.

thanks,
Ming Lei

WARNING: multiple messages have this Message-ID (diff)
From: Ming Lei <tom.leiming@gmail.com>
To: Keith Busch <kbusch@kernel.org>
Cc: "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	Tokunori Ikegami <ikegami.t@gmail.com>,
	Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>,
	"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>
Subject: Re: [PATCH] block, nvme: Increase max segments parameter setting value
Date: Sat, 28 Mar 2020 16:28:51 +0800	[thread overview]
Message-ID: <CACVXFVNY++56icyHB4+-aGjRXWZ5B7WdK4z-N336u0+v6sDhbQ@mail.gmail.com> (raw)
In-Reply-To: <20200328031334.GA18429@keith-busch>

On Sat, Mar 28, 2020 at 11:13 AM Keith Busch <kbusch@kernel.org> wrote:
>
> On Sat, Mar 28, 2020 at 10:11:57AM +0800, Ming Lei wrote:
> > On Sat, Mar 28, 2020 at 2:18 AM Keith Busch <kbusch@kernel.org> wrote:
> > >
> > > This is actually even more confusing. We do not support 256MB transfers
> > > within a single command in the pci nvme driver anymore. The max is 4MB,
> > > so I don't see how increasing the max segments will help: you should be
> > > hitting the 'max_sectors' limit if you don't hit the segment limit first.
> >
> > That looks a bug for passthrough req, because 'max_sectors' limit is only
> > checked in bio_add_pc_page(), not done in blk_rq_append_bio(), something
> > like the following seems required:
>
> Shouldn't bio_map_user_iov() or bio_copy_user_iov() have caught the
> length limit before proceeding to blk_rq_append_bio()?

Actually the limit should be caught earlier in bio_add_pc_page(), that requires
to pass 'rq' in, then one perfect passthrough bio can be made before
appending to rq.

Not only max sector limit, max segments & virt_boundary should be checked
in request wide too.

So far, only lightnvm calls bio_add_pc_page() before allocating
request, and that is
the 1st bio, so NULL rq can be passed.

thanks,
Ming Lei

_______________________________________________
linux-nvme mailing list
linux-nvme@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-nvme

  reply	other threads:[~2020-03-28  8:29 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-23 18:23 [PATCH] block, nvme: Increase max segments parameter setting value Tokunori Ikegami
2020-03-23 18:23 ` Tokunori Ikegami
2020-03-23 19:14 ` Chaitanya Kulkarni
2020-03-23 19:14   ` Chaitanya Kulkarni
2020-03-23 23:09   ` Tokunori Ikegami
2020-03-23 23:09     ` Tokunori Ikegami
2020-03-24  0:02     ` Keith Busch
2020-03-24  0:02       ` Keith Busch
2020-03-24 16:51       ` Tokunori Ikegami
2020-03-24 16:51         ` Tokunori Ikegami
2020-03-27 17:50         ` Tokunori Ikegami
2020-03-27 17:50           ` Tokunori Ikegami
2020-03-27 18:18           ` Keith Busch
2020-03-27 18:18             ` Keith Busch
2020-03-28  2:11             ` Ming Lei
2020-03-28  2:11               ` Ming Lei
2020-03-28  3:13               ` Keith Busch
2020-03-28  3:13                 ` Keith Busch
2020-03-28  8:28                 ` Ming Lei [this message]
2020-03-28  8:28                   ` Ming Lei
2020-03-28 12:57               ` Tokunori Ikegami
2020-03-28 12:57                 ` Tokunori Ikegami
2020-03-29  3:01                 ` Ming Lei
2020-03-29  3:01                   ` Ming Lei
2020-03-30  9:15                   ` Tokunori Ikegami
2020-03-30  9:15                     ` Tokunori Ikegami
2020-03-30 13:53                     ` Keith Busch
2020-03-30 13:53                       ` Keith Busch
2020-03-31 15:24                       ` Tokunori Ikegami
2020-03-31 15:24                         ` Tokunori Ikegami
2020-03-31 14:13                     ` Joshi
2020-03-31 14:13                       ` Joshi
2020-03-31 15:37                       ` Tokunori Ikegami
2020-03-31 15:37                         ` Tokunori Ikegami
2020-03-24  7:16 ` Hannes Reinecke
2020-03-24  7:16   ` Hannes Reinecke
2020-03-24 17:17   ` Tokunori Ikegami
2020-03-24 17:17     ` Tokunori Ikegami

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