Re: [PATCH for-next v3 4/5] null_blk: pass transfer size to null_handle_rq()
From: Damien Le Moal <dlemoal@kernel.org>
Date: 2025-01-17 23:05:22
On 1/15/25 1:29 PM, Shin'ichiro Kawasaki wrote:
As preparation to support partial data transfer, add a new argument to null_handle_rq() to pass the number of sectors to transfer. This commit does not change the behavior. Signed-off-by: Shin'ichiro Kawasaki <redacted>
Looks good. As a nit, I would suggest renaming null_handle_rq() to the less generic name null_handle_rw(), or may be, null_handle_data_transfer(). Regardless, Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
quoted hunk ↗ jump to hunk
--- drivers/block/null_blk/main.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-)diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c index 87037cb375c9..71c86775354e 100644 --- a/drivers/block/null_blk/main.c +++ b/drivers/block/null_blk/main.c@@ -1263,25 +1263,36 @@ static int null_transfer(struct nullb *nullb, struct page *page, return err; } -static blk_status_t null_handle_rq(struct nullb_cmd *cmd) +/* + * Transfer data for the given request. The transfer size is capped with the + * nr_sectors argument. + */ +static blk_status_t null_handle_rq(struct nullb_cmd *cmd, sector_t nr_sectors) { struct request *rq = blk_mq_rq_from_pdu(cmd); struct nullb *nullb = cmd->nq->dev->nullb; int err = 0; unsigned int len; sector_t sector = blk_rq_pos(rq); + unsigned int max_bytes = nr_sectors << SECTOR_SHIFT; + unsigned int transferred_bytes = 0; struct req_iterator iter; struct bio_vec bvec; spin_lock_irq(&nullb->lock); rq_for_each_segment(bvec, rq, iter) { len = bvec.bv_len; + if (transferred_bytes + len > max_bytes) + len = max_bytes - transferred_bytes; err = null_transfer(nullb, bvec.bv_page, len, bvec.bv_offset, op_is_write(req_op(rq)), sector, rq->cmd_flags & REQ_FUA); if (err) break; sector += len >> SECTOR_SHIFT; + transferred_bytes += len; + if (transferred_bytes >= max_bytes) + break; } spin_unlock_irq(&nullb->lock);@@ -1333,7 +1344,7 @@ blk_status_t null_handle_memory_backed(struct nullb_cmd *cmd, enum req_op op, if (op == REQ_OP_DISCARD) return null_handle_discard(dev, sector, nr_sectors); - return null_handle_rq(cmd); + return null_handle_rq(cmd, nr_sectors); } static void nullb_zero_read_cmd_buffer(struct nullb_cmd *cmd)
-- Damien Le Moal Western Digital Research