Re: [RFC 5/5] block: implement io_uring discard cmd

[Ming Lei <ming.lei@redhat.com>]

On Wed, Aug 14, 2024 at 6:46 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
>
> Add ->uring_cmd callback for block device files and use it to implement
> asynchronous discard. Normally, it first tries to execute the command
> from non-blocking context, which we limit to a single bio because
> otherwise one of sub-bios may need to wait for other bios, and we don't
> want to deal with partial IO. If non-blocking attempt fails, we'll retry
> it in a blocking context.
>
> Suggested-by: Conrad Meyer <conradmeyer@meta.com>
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
>  block/blk.h             |  1 +
>  block/fops.c            |  2 +
>  block/ioctl.c           | 94 +++++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/fs.h |  2 +
>  4 files changed, 99 insertions(+)
>
> diff --git a/block/blk.h b/block/blk.h
> index e180863f918b..5178c5ba6852 100644
> --- a/block/blk.h
> +++ b/block/blk.h
> @@ -571,6 +571,7 @@ blk_mode_t file_to_blk_mode(struct file *file);
>  int truncate_bdev_range(struct block_device *bdev, blk_mode_t mode,
>                 loff_t lstart, loff_t lend);
>  long blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg);
> +int blkdev_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags);
>  long compat_blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg);
>
>  extern const struct address_space_operations def_blk_aops;
> diff --git a/block/fops.c b/block/fops.c
> index 9825c1713a49..8154b10b5abf 100644
> --- a/block/fops.c
> +++ b/block/fops.c
> @@ -17,6 +17,7 @@
>  #include <linux/fs.h>
>  #include <linux/iomap.h>
>  #include <linux/module.h>
> +#include <linux/io_uring/cmd.h>
>  #include "blk.h"
>
>  static inline struct inode *bdev_file_inode(struct file *file)
> @@ -873,6 +874,7 @@ const struct file_operations def_blk_fops = {
>         .splice_read    = filemap_splice_read,
>         .splice_write   = iter_file_splice_write,
>         .fallocate      = blkdev_fallocate,
> +       .uring_cmd      = blkdev_uring_cmd,

Just be curious, we have IORING_OP_FALLOCATE already for sending
discard to block device, why is .uring_cmd added for this purpose?

Thanks,