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SubjectRe: [RFC PATCH v2 0/2] add simple copy support
So, I'm really worried about:

a) a good use case. GC in f2fs or btrfs seem like good use cases, as
does accelating dm-kcopyd. I agree with Damien that lifting dm-kcopyd
to common code would also be really nice. I'm not 100% sure it should
be a requirement, but it sure would be nice to have
I don't think just adding an ioctl is enough of a use case for complex
kernel infrastructure.
b) We had a bunch of different attempts at SCSI XCOPY support form IIRC
Martin, Bart and Mikulas. I think we need to pull them into this
discussion, and make sure whatever we do covers the SCSI needs.

On Fri, Dec 04, 2020 at 03:16:57PM +0530, SelvaKumar S 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
>
> This is an RFC. Looking forward for any feedbacks or other alternate
> designs for plumbing simple copy to IO stack.
>
> 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 accepts destination, no of sources and arrays of
> source ranges from application and attach it as payload to the bio and
> submits to the device.
>
> Following limits are added to queue limits and are exposed in sysfs
> to userspace
> - *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.
>
> 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 (2):
> block: add simple copy support
> nvme: add simple copy support
>
> block/blk-core.c | 94 ++++++++++++++++++++++++++---
> block/blk-lib.c | 123 ++++++++++++++++++++++++++++++++++++++
> block/blk-merge.c | 2 +
> block/blk-settings.c | 11 ++++
> block/blk-sysfs.c | 23 +++++++
> block/blk-zoned.c | 1 +
> block/bounce.c | 1 +
> block/ioctl.c | 43 +++++++++++++
> drivers/nvme/host/core.c | 87 +++++++++++++++++++++++++++
> include/linux/bio.h | 1 +
> include/linux/blk_types.h | 15 +++++
> include/linux/blkdev.h | 15 +++++
> include/linux/nvme.h | 43 ++++++++++++-
> include/uapi/linux/fs.h | 13 ++++
> 14 files changed, 461 insertions(+), 11 deletions(-)
>
> --
> 2.25.1
---end quoted text---

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