Message-ID: <CAHqX9vbdtNiRvAHSy+1+rD6FEp6zBqmH2P_99P-+dgMZDbMZsA@mail.gmail.com>
Date:   Tue, 23 Feb 2021 14:30:29 +0530
From:   Selva Jove <selvajove@...il.com>
To:     Su Yue <l@...enly.su>
Cc:     SelvaKumar S <selvakuma.s1@...sung.com>,
        linux-nvme@...ts.infradead.org, Keith Busch <kbusch@...nel.org>,
        axboe@...nel.dk, Damien Le Moal <damien.lemoal@....com>,
        hch@....de, sagi@...mberg.me, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, dm-devel@...hat.com,
        snitzer@...hat.com, joshiiitr@...il.com, nj.shetty@...sung.com,
        joshi.k@...sung.com, javier.gonz@...sung.com, kch@...nel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [RFC PATCH v5 0/4] add simple copy support

Thanks Su Yue. I'll update the link in the next series.

On Mon, Feb 22, 2021 at 12:23 PM Su Yue <l@...enly.su> wrote:
>
>
> On Fri 19 Feb 2021 at 20:45, SelvaKumar S
> <selvakuma.s1@...sung.com> wrote:
>
> > This patchset tries to add support for TP4065a ("Simple Copy
> > Command"),
> > v2020.05.04 ("Ratified")
> >
> > The Specification can be found in following link.
> > https://nvmexpress.org/wp-content/uploads/NVM-Express-1.4-Ratified-TPs-1.zip
> >
>
> 404 not found.
> Should it be
> https://nvmexpress.org/wp-content/uploads/NVM-Express-1.4-Ratified-TPs.zip
> ?
>
> > Simple copy command is a copy offloading operation and is  used
> > to copy
> > multiple contiguous ranges (source_ranges) of LBA's to a single
> > destination
> > LBA within the device reducing traffic between host and device.
> >
> > This implementation doesn't add native copy offload support for
> > stacked
> > devices rather copy offload is done through emulation. Possible
> > use
> > cases are F2FS gc and BTRFS relocation/balance.
> >
> > *blkdev_issue_copy* takes source bdev, no of sources, array of
> > source
> > ranges (in sectors), destination bdev and destination offset(in
> > sectors).
> > If both source and destination block devices are same and
> > copy_offload = 1,
> > then copy is done through native copy offloading. Copy emulation
> > is used
> > in other cases.
> >
> > As SCSI XCOPY can take two different block devices and no of
> > source range is
> > equal to 1, this interface can be extended in future to support
> > SCSI XCOPY.
> >
> > For devices supporting native simple copy, attach the control
> > information
> > as payload to the bio and submit to the device. For devices
> > without native
> > copy support, copy emulation is done by reading each source
> > range into memory
> > and writing it to the destination. Caller can choose not to try
> > emulation if copy offload is not supported by setting
> > BLKDEV_COPY_NOEMULATION flag.
> >
> > Following limits are added to queue limits and are exposed in
> > sysfs
> > to userspace
> >       - *copy_offload* controls copy_offload. set 0 to disable copy
> >               offload, 1 to enable native copy offloading support.
> >       - *max_copy_sectors* limits the sum of all source_range length
> >       - *max_copy_nr_ranges* limits the number of source ranges
> >       - *max_copy_range_sectors* limit the maximum number of sectors
> >               that can constitute a single source range.
> >
> >       max_copy_sectors = 0 indicates the device doesn't support copy
> > offloading.
> >
> >       *copy offload* sysfs entry is configurable and can be used
> > toggle
> > between emulation and native support depending upon the usecase.
> >
> > Changes from v4
> >
> > 1. Extend dm-kcopyd to leverage copy-offload, while copying
> > within the
> > same device. The other approach was to have copy-emulation by
> > moving
> > dm-kcopyd to block layer. But it also required moving core dm-io
> > infra,
> > causing a massive churn across multiple dm-targets.
> >
> > 2. Remove export in bio_map_kern()
> > 3. Change copy_offload sysfs to accept 0 or else
> > 4. Rename copy support flag to QUEUE_FLAG_SIMPLE_COPY
> > 5. Rename payload entries, add source bdev field to be used
> > while
> > partition remapping, remove copy_size
> > 6. Change the blkdev_issue_copy() interface to accept
> > destination and
> > source values in sector rather in bytes
> > 7. Add payload to bio using bio_map_kern() for copy_offload case
> > 8. Add check to return error if one of the source range length
> > is 0
> > 9. Add BLKDEV_COPY_NOEMULATION flag to allow user to not try
> > copy
> > emulation incase of copy offload is not supported. Caller can
> > his use
> > his existing copying logic to complete the io.
> > 10. Bug fix copy checks and reduce size of rcu_lock()
> >
> > Planned for next:
> > - adding blktests
> > - handling larger (than device limits) copy
> > - decide on ioctl interface (man-page etc.)
> >
> > Changes from v3
> >
> > 1. gfp_flag fixes.
> > 2. Export bio_map_kern() and use it to allocate and add pages to
> > bio.
> > 3. Move copy offload, reading to buf, writing from buf to
> > separate functions.
> > 4. Send read bio of copy offload by chaining them and submit
> > asynchronously.
> > 5. Add gendisk->part0 and part->bd_start_sect changes to
> > blk_check_copy().
> > 6. Move single source range limit check to blk_check_copy()
> > 7. Rename __blkdev_issue_copy() to blkdev_issue_copy and remove
> > old helper.
> > 8. Change blkdev_issue_copy() interface generic to accepts
> > destination bdev
> >       to support XCOPY as well.
> > 9. Add invalidate_kernel_vmap_range() after reading data for
> > vmalloc'ed memory.
> > 10. Fix buf allocoation logic to allocate buffer for the total
> > size of copy.
> > 11. Reword patch commit description.
> >
> > Changes from v2
> >
> > 1. Add emulation support for devices not supporting copy.
> > 2. Add *copy_offload* sysfs entry to enable and disable
> > copy_offload
> >       in devices supporting simple copy.
> > 3. Remove simple copy support for stacked devices.
> >
> > Changes from v1:
> >
> > 1. Fix memory leak in __blkdev_issue_copy
> > 2. Unmark blk_check_copy inline
> > 3. Fix line break in blk_check_copy_eod
> > 4. Remove p checks and made code more readable
> > 5. Don't use bio_set_op_attrs and remove op and set
> >    bi_opf directly
> > 6. Use struct_size to calculate total_size
> > 7. Fix partition remap of copy destination
> > 8. Remove mcl,mssrl,msrc from nvme_ns
> > 9. Initialize copy queue limits to 0 in nvme_config_copy
> > 10. Remove return in QUEUE_FLAG_COPY check
> > 11. Remove unused OCFS
> >
> > SelvaKumar S (4):
> >   block: make bio_map_kern() non static
> >   block: add simple copy support
> >   nvme: add simple copy support
> >   dm kcopyd: add simple copy offload support
> >
> >  block/blk-core.c          | 102 +++++++++++++++--
> >  block/blk-lib.c           | 223
> >  ++++++++++++++++++++++++++++++++++++++
> >  block/blk-map.c           |   2 +-
> >  block/blk-merge.c         |   2 +
> >  block/blk-settings.c      |  10 ++
> >  block/blk-sysfs.c         |  47 ++++++++
> >  block/blk-zoned.c         |   1 +
> >  block/bounce.c            |   1 +
> >  block/ioctl.c             |  33 ++++++
> >  drivers/md/dm-kcopyd.c    |  49 ++++++++-
> >  drivers/nvme/host/core.c  |  87 +++++++++++++++
> >  include/linux/bio.h       |   1 +
> >  include/linux/blk_types.h |  14 +++
> >  include/linux/blkdev.h    |  17 +++
> >  include/linux/nvme.h      |  43 +++++++-
> >  include/uapi/linux/fs.h   |  13 +++
> >  16 files changed, 627 insertions(+), 18 deletions(-)
>

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