Re: [RFC PATCH v2 0/2] add simple copy support

["Javier González" <javier@javigon.com>]

On 07.12.2020 15:11, Christoph Hellwig wrote:
>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.

We are looking at dm-kcopyd. I would have liked to start with a very
specific use case and build from there, but I see Damien's and Keith's
point of having a default path. I believe we can add this to the next
version.

> 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.

Agree. We discussed a lot about the scope and agreed that everything
outside of the specifics of Simple Copy requires the input from the ones
that have worked on XCOPY support in the past.

>
>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---