On Tue, Nov 15, 2016 at 10:50:36PM -0800, Chaitanya Kulkarni wrote:
> This adds a new block layer operation to zero out a range of
> LBAs. This allows to implement zeroing for devices that don't use
> either discard with a predictable zero pattern or WRITE SAME of zeroes.
> The prominent example of that is NVMe with the Write Zeroes command,
> but in the future this should also help with improving the way
> zeroing discards work.
>
> Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxxx>
> ---
> +static int __blkdev_issue_write_zeroes(struct block_device *bdev,
> + sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
> + struct bio **biop)
> +{
> + struct bio *bio = *biop;
> + unsigned int max_write_zeroes_sectors;
> + struct request_queue *q = bdev_get_queue(bdev);
> +
> + if (!q)
> + return -ENXIO;
> +
> + if (!blk_queue_write_zeroes(q))
> + return -EOPNOTSUPP;
> +
> + /* Ensure that max_write_zeroes_sectors doesn't overflow bi_size */
> + max_write_zeroes_sectors = UINT_MAX >> 9;
> +
> + while (nr_sects) {
> + bio = next_bio(bio, 0, gfp_mask);
> + bio->bi_iter.bi_sector = sector;
> + bio->bi_bdev = bdev;
> + bio_set_op_attrs(bio, REQ_OP_WRITE_ZEROES, 0);
> +
> + if (nr_sects > max_write_zeroes_sectors) {
> + bio->bi_iter.bi_size = max_write_zeroes_sectors << 9;
Your maximum bi_size exceeds the 2-bytes an NVMe Write Zeroes command
provides for the block count. Instead of having a simple queue flag
for write zeroes support, have it take a max sectors value instead. I
proposed this here a couple years ago (though I goof'ed registering the
nvme part...):
http://lists.infradead.org/pipermail/linux-nvme/2014-July/001054.html
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