This patch adds support for memory backed REQ_OP_WRITE_ZEROES operations for the null_blk request mode. We introduce two new functions where we zeroout the sector(s) using memset which are part of the payloadless write-zeroes request.
Signed-off-by: Chaitanya Kulkarni <[email protected]> --- drivers/block/null_blk_main.c | 45 ++++++++++++++++++++++++++++++++++- 1 file changed, 44 insertions(+), 1 deletion(-) diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c index 65da7c2d93b9..fca011a05277 100644 --- a/drivers/block/null_blk_main.c +++ b/drivers/block/null_blk_main.c @@ -725,6 +725,24 @@ 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) { @@ -1026,6 +1044,25 @@ static void null_handle_discard(struct nullb *nullb, sector_t sector, size_t n) spin_unlock_irq(&nullb->lock); } +static void null_handle_write_zeroes(struct nullb *nullb, sector_t sector, + unsigned int bytes_left) +{ + sector_t nr_sectors; + 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); +} + static int null_handle_flush(struct nullb *nullb) { int err; @@ -1075,9 +1112,15 @@ static int null_handle_rq(struct nullb_cmd *cmd) sector = blk_rq_pos(rq); - if (req_op(rq) == REQ_OP_DISCARD) { + switch (req_op(rq)) { + case REQ_OP_DISCARD: null_handle_discard(nullb, sector, blk_rq_bytes(rq)); return 0; + case REQ_OP_WRITE_ZEROES: + null_handle_write_zeroes(nullb, sector, blk_rq_bytes(rq)); + return 0; + default: + break; } spin_lock_irq(&nullb->lock); -- 2.17.0
