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From: Selva Jove <selvajove@gmail.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: axboe@kernel.dk, Damien Le Moal <damien.lemoal@wdc.com>,
	kch@kernel.org, SelvaKumar S <selvakuma.s1@samsung.com>,
	sagi@grimberg.me, snitzer@redhat.com,
	linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
	nj.shetty@samsung.com, linux-block@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, dm-devel@redhat.com,
	joshi.k@samsung.com, javier.gonz@samsung.com,
	Keith Busch <kbusch@kernel.org>,
	joshiiitr@gmail.com, hch@lst.de
Subject: Re: [RFC PATCH v5 3/4] nvme: add simple copy support
Date: Mon, 22 Feb 2021 21:27:50 +0530	[thread overview]
Message-ID: <CAHqX9vYdz-SRP2y6gzR1ei5WukNGzWhrHrvtXo4L8iFw4Lb9Hg@mail.gmail.com> (raw)
In-Reply-To: <20210220033637.GA2858050@casper.infradead.org>

Matthew,

Maximum Source Range Count (MSRC) is limited by u8. So the maximum
number of source ranges is 256 (0 base value). The number of pages
required to be sent to the device is at most 2. Since we are
allocating the memory using kmalloc_array(), we would get a continuous
physical segment. nvme_map_data() maps the physical segment either by
setting 2 PRP pointers or by SGL. So the copy command sends two pages
to the device for copying more than128 ranges.

On Sat, Feb 20, 2021 at 9:08 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Fri, Feb 19, 2021 at 06:15:16PM +0530, SelvaKumar S wrote:
> > +     struct nvme_copy_range *range = NULL;
> [...]
> > +     range = kmalloc_array(nr_range, sizeof(*range),
> > +                     GFP_ATOMIC | __GFP_NOWARN);
> [...]
> > +     req->special_vec.bv_page = virt_to_page(range);
> > +     req->special_vec.bv_offset = offset_in_page(range);
> > +     req->special_vec.bv_len = sizeof(*range) * nr_range;
> [...]
> > +struct nvme_copy_range {
> > +     __le64                  rsvd0;
> > +     __le64                  slba;
> > +     __le16                  nlb;
> > +     __le16                  rsvd18;
> > +     __le32                  rsvd20;
> > +     __le32                  eilbrt;
> > +     __le16                  elbat;
> > +     __le16                  elbatm;
> > +};
>
> so ... at 32 bytes, you can get 128 per 4kB page.  What happens if you
> try to send down a command that attempts to copy 129 ranges?

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  reply	other threads:[~2021-02-22 15:58 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20210219124555epcas5p1334e7c4d64ada5dc4a2ca0feb48c1d44@epcas5p1.samsung.com>
2021-02-19 12:45 ` [RFC PATCH v5 0/4] " SelvaKumar S
     [not found]   ` <CGME20210219124559epcas5p41da46f1c248e334953d407a154697903@epcas5p4.samsung.com>
2021-02-19 12:45     ` [RFC PATCH v5 1/4] block: make bio_map_kern() non static SelvaKumar S
     [not found]   ` <CGME20210219124603epcas5p33add0f2c1781b2a4d71bf30c9e1ac647@epcas5p3.samsung.com>
2021-02-19 12:45     ` [RFC PATCH v5 2/4] block: add simple copy support SelvaKumar S
2021-02-20  4:59       ` Damien Le Moal
2021-04-07 11:32         ` Selva Jove
2021-04-12  0:24           ` Damien Le Moal
2021-04-12 14:34             ` Selva Jove
2021-04-13  0:32               ` Damien Le Moal
2021-04-14  6:58                 ` Selva Jove
     [not found]   ` <CGME20210219124608epcas5p2a673f9e00c3e7b5352f115497b0e2d98@epcas5p2.samsung.com>
2021-02-19 12:45     ` [RFC PATCH v5 3/4] nvme: " SelvaKumar S
2021-02-20  3:36       ` Matthew Wilcox
2021-02-22 15:57         ` Selva Jove [this message]
     [not found]   ` <CGME20210219124611epcas5p1c775b63b537e75da161556e375fcf05e@epcas5p1.samsung.com>
2021-02-19 12:45     ` [RFC PATCH v5 4/4] dm kcopyd: add simple copy offload support SelvaKumar S
2021-02-20 18:01   ` [RFC PATCH v5 0/4] add simple copy support David Laight
2021-02-20 19:08     ` Matthew Wilcox
2021-02-20 19:19     ` Keith Busch
2021-02-21 23:52   ` Dave Chinner
2021-02-23  9:14     ` Selva Jove
2021-02-22  1:31   ` Ming Lei
2021-02-22  6:52   ` Su Yue
2021-02-23  9:00     ` Selva Jove
2021-04-10  0:21   ` Max Gurtovoy
2021-04-10  0:29     ` Chaitanya Kulkarni
2021-04-10  6:32       ` Javier González
2021-04-11  9:10         ` Max Gurtovoy
2021-04-11 19:26           ` Javier González
2021-04-13 15:38             ` Max Gurtovoy
2021-04-13 18:25               ` Javier González
2021-04-13 18:36                 ` Chaitanya Kulkarni

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