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

[Javier González]

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---