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From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <keith.busch@intel.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, linux-nvme@lists.infradead.org
Subject: Re: [PATCH 4/4] nvme: support ranged discard requests
Date: Tue, 7 Feb 2017 20:34:39 +0100	[thread overview]
Message-ID: <20170207193439.GA26834@lst.de> (raw)
In-Reply-To: <20170207183453.GC10133@localhost.localdomain>

On Tue, Feb 07, 2017 at 01:34:54PM -0500, Keith Busch wrote:
> On Tue, Feb 07, 2017 at 05:46:58PM +0100, Christoph Hellwig wrote:
> > @@ -1233,6 +1243,8 @@ static void nvme_set_queue_limits(struct nvme_ctrl *ctrl,
> >  	if (ctrl->vwc & NVME_CTRL_VWC_PRESENT)
> >  		vwc = true;
> >  	blk_queue_write_cache(q, vwc, vwc);
> > +	blk_queue_max_discard_segments(q,
> > +			PAGE_SIZE / sizeof(struct nvme_dsm_range));
> 
> We need to use ctrl->page_size rather than PAGE_SIZE.

We need the PAGE_SIZE upper bound because the "special" bvec only
allows a single page payload.  I can't find any indication that
the DSM command is limited to a single PRP, so not sure where a
ctrl->page_size would come from.  But now that I looked again there
is a hard limit of 256 entries due to NR being a 8-bit field, so
I need to cap on that at least.

WARNING: multiple messages have this Message-ID (diff)
From: hch@lst.de (Christoph Hellwig)
Subject: [PATCH 4/4] nvme: support ranged discard requests
Date: Tue, 7 Feb 2017 20:34:39 +0100	[thread overview]
Message-ID: <20170207193439.GA26834@lst.de> (raw)
In-Reply-To: <20170207183453.GC10133@localhost.localdomain>

On Tue, Feb 07, 2017@01:34:54PM -0500, Keith Busch wrote:
> On Tue, Feb 07, 2017@05:46:58PM +0100, Christoph Hellwig wrote:
> > @@ -1233,6 +1243,8 @@ static void nvme_set_queue_limits(struct nvme_ctrl *ctrl,
> >  	if (ctrl->vwc & NVME_CTRL_VWC_PRESENT)
> >  		vwc = true;
> >  	blk_queue_write_cache(q, vwc, vwc);
> > +	blk_queue_max_discard_segments(q,
> > +			PAGE_SIZE / sizeof(struct nvme_dsm_range));
> 
> We need to use ctrl->page_size rather than PAGE_SIZE.

We need the PAGE_SIZE upper bound because the "special" bvec only
allows a single page payload.  I can't find any indication that
the DSM command is limited to a single PRP, so not sure where a
ctrl->page_size would come from.  But now that I looked again there
is a hard limit of 256 entries due to NR being a 8-bit field, so
I need to cap on that at least.

  reply	other threads:[~2017-02-07 19:34 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-07 16:46 support for multi-range discard requests Christoph Hellwig
2017-02-07 16:46 ` Christoph Hellwig
2017-02-07 16:46 ` [PATCH 1/4] block: move req_set_nomerge to blk.h Christoph Hellwig
2017-02-07 16:46   ` Christoph Hellwig
2017-02-15 10:29   ` Sagi Grimberg
2017-02-15 10:29     ` Sagi Grimberg
2017-02-07 16:46 ` [PATCH 2/4] block: enumify ELEVATOR_*_MERGE Christoph Hellwig
2017-02-07 16:46   ` Christoph Hellwig
2017-02-15 10:31   ` Sagi Grimberg
2017-02-15 10:31     ` Sagi Grimberg
2017-02-07 16:46 ` [PATCH 3/4] block: optionally merge discontiguous discard bios into a single request Christoph Hellwig
2017-02-07 16:46   ` Christoph Hellwig
2017-02-08 10:54   ` Ming Lei
2017-02-08 10:54     ` Ming Lei
2017-02-08 11:57     ` Christoph Hellwig
2017-02-08 11:57       ` Christoph Hellwig
2017-02-15 10:36   ` Sagi Grimberg
2017-02-15 10:36     ` Sagi Grimberg
2017-02-07 16:46 ` [PATCH 4/4] nvme: support ranged discard requests Christoph Hellwig
2017-02-07 16:46   ` Christoph Hellwig
2017-02-07 18:34   ` Keith Busch
2017-02-07 18:34     ` Keith Busch
2017-02-07 19:34     ` Christoph Hellwig [this message]
2017-02-07 19:34       ` Christoph Hellwig
2017-02-15 10:42       ` Sagi Grimberg
2017-02-15 10:42         ` Sagi Grimberg
2017-02-08 13:13 support for multi-range discard requests V2 Christoph Hellwig
2017-02-08 13:13 ` [PATCH 4/4] nvme: support ranged discard requests Christoph Hellwig
2017-02-08 13:13   ` Christoph Hellwig
2017-02-08 13:32   ` Andrey Kuzmin
2017-02-08 13:36     ` Christoph Hellwig
2017-02-08 13:36       ` Christoph Hellwig
2017-02-08 13:46 support for multi-range discard requests V3 Christoph Hellwig
2017-02-08 13:46 ` [PATCH 4/4] nvme: support ranged discard requests Christoph Hellwig
2017-02-08 13:46   ` Christoph Hellwig
2017-02-15 10:45   ` Sagi Grimberg
2017-02-15 10:45     ` Sagi Grimberg

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