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SubjectRe: [RFC PATCH v5 0/4] add simple copy support
Date

On Fri 19 Feb 2021 at 20:45, SelvaKumar S
<selvakuma.s1@samsung.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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