On 10/5/22 12:16, Chaitanya Kulkarni wrote:
> Add a helper functions to enable the REQ_OP_WRITE_ZEROES operations
> when null_blk is configured with the membacked mode.
>
> Since write-zeroes is a non-trivial I/O operation we need this to
> add a blktest so we can test the non-trivial I/O path from the
> application to the block layer.
Why a separate patch for this ? Introducing the module argument and
configfs equivalent separately in 2 different patches is strange and does
not facilitate review.
This patch should be merged with patch 1.
>
> Signed-off-by: Chaitanya Kulkarni <kch@xxxxxxxxxx>
> ---
> drivers/block/null_blk/main.c | 46 ++++++++++++++++++++++++++++++++++-
> 1 file changed, 45 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
> index fc3e883f7b84..2d592b4eb815 100644
> --- a/drivers/block/null_blk/main.c
> +++ b/drivers/block/null_blk/main.c
> @@ -420,6 +420,7 @@ NULLB_DEVICE_ATTR(blocking, bool, NULL);
> NULLB_DEVICE_ATTR(use_per_node_hctx, bool, NULL);
> NULLB_DEVICE_ATTR(memory_backed, bool, NULL);
> NULLB_DEVICE_ATTR(discard, bool, NULL);
> +NULLB_DEVICE_ATTR(write_zeroes, bool, NULL);
> NULLB_DEVICE_ATTR(mbps, uint, NULL);
> NULLB_DEVICE_ATTR(cache_size, ulong, NULL);
> NULLB_DEVICE_ATTR(zoned, bool, NULL);
> @@ -544,6 +545,7 @@ static struct configfs_attribute *nullb_device_attrs[] = {
> &nullb_device_attr_power,
> &nullb_device_attr_memory_backed,
> &nullb_device_attr_discard,
> + &nullb_device_attr_write_zeroes,
> &nullb_device_attr_mbps,
> &nullb_device_attr_cache_size,
> &nullb_device_attr_badblocks,
> @@ -618,7 +620,7 @@ static ssize_t memb_group_features_show(struct config_item *item, char *page)
> "poll_queues,power,queue_mode,shared_tag_bitmap,size,"
> "submit_queues,use_per_node_hctx,virt_boundary,zoned,"
> "zone_capacity,zone_max_active,zone_max_open,"
> - "zone_nr_conv,zone_size\n");
> + "zone_nr_conv,zone_size,write_zeroes\n");
> }
>
> CONFIGFS_ATTR_RO(memb_group_, features);
> @@ -875,6 +877,24 @@ static void null_free_sector(struct nullb *nullb, sector_t sector,
> }
> }
>
> +static void null_zero_sector(struct nullb_device *d, sector_t sect,
> + sector_t nr_sects, bool cache)
> +{
> + struct radix_tree_root *root = cache ? &d->cache : &d->data;
> + struct nullb_page *t_page;
> + unsigned int offset;
> + void *dest;
> +
> + t_page = radix_tree_lookup(root, sect >> PAGE_SECTORS_SHIFT);
> + if (!t_page)
> + return;
> +
> + offset = (sect & SECTOR_MASK) << SECTOR_SHIFT;
> + dest = kmap_atomic(t_page->page);
> + memset(dest + offset, 0, SECTOR_SIZE * nr_sects);
> + kunmap_atomic(dest);
> +}
> +
> static struct nullb_page *null_radix_tree_insert(struct nullb *nullb, u64 idx,
> struct nullb_page *t_page, bool is_cache)
> {
> @@ -1191,6 +1211,27 @@ blk_status_t null_handle_discard(struct nullb_device *dev,
> return BLK_STS_OK;
> }
>
> +static blk_status_t null_handle_write_zeroes(struct nullb_device *dev,
> + sector_t sector, sector_t nr_sectors)
> +{
> + unsigned int bytes_left = nr_sectors << 9;
> + struct nullb *nullb = dev->nullb;
> + size_t curr_bytes;
> +
> + spin_lock_irq(&nullb->lock);
> + while (bytes_left > 0) {
> + curr_bytes = min_t(size_t, bytes_left, nullb->dev->blocksize);
> + nr_sectors = curr_bytes >> SECTOR_SHIFT;
> + null_zero_sector(nullb->dev, sector, nr_sectors, false);
> + if (null_cache_active(nullb))
> + null_zero_sector(nullb->dev, sector, nr_sectors, true);
> + sector += nr_sectors;
> + bytes_left -= curr_bytes;
> + }
> + spin_unlock_irq(&nullb->lock);
> + return BLK_STS_OK;
> +}
> +
> static int null_handle_flush(struct nullb *nullb)
> {
> int err;
> @@ -1357,6 +1398,9 @@ static inline blk_status_t null_handle_memory_backed(struct nullb_cmd *cmd,
> if (op == REQ_OP_DISCARD)
> return null_handle_discard(dev, sector, nr_sectors);
>
> + if (op == REQ_OP_WRITE_ZEROES)
> + return null_handle_write_zeroes(dev, sector, nr_sectors);
> +
> if (dev->queue_mode == NULL_Q_BIO)
> err = null_handle_bio(cmd);
> else
--
Damien Le Moal
Western Digital Research
