On Thu, Aug 22, 2024 at 04:35:56AM +0100, Pavel Begunkov wrote:
> Add another io_uring cmd for block layer implementing asynchronous write
> zeroes. It reuses helpers we've added for async discards, and inherits
> the code structure as well as all considerations in regards to page
> cache races.
Most comments from discard apply here as well.
> +static int blkdev_queue_cmd(struct io_uring_cmd *cmd, struct block_device *bdev,
> + uint64_t start, uint64_t len, sector_t limit,
> + blk_opf_t opf)
This feels a little over generic as it doesn't just queue any random
command.
> +static int blkdev_cmd_write_zeroes(struct io_uring_cmd *cmd,
> + struct block_device *bdev,
> + uint64_t start, uint64_t len, bool nowait)
> +{
> + blk_opf_t opf = REQ_OP_WRITE_ZEROES | REQ_NOUNMAP;
> +
> + if (nowait)
> + opf |= REQ_NOWAIT;
> + return blkdev_queue_cmd(cmd, bdev, start, len,
> + bdev_write_zeroes_sectors(bdev), opf);
So no support for fallback to Write of zero page here? That's probably
the case where the async offload is needed most.
> +struct bio *blk_alloc_write_zeroes_bio(struct block_device *bdev,
> + sector_t *sector, sector_t *nr_sects,
> + gfp_t gfp_mask);
Please keep this in block/blk.h, no need to expose it to the entire
kernel.
