From 3d3472f3ed419fe1a9d3f881a4905fa8e03d750c Mon Sep 17 00:00:00 2001 From: Chaitanya Kulkarni Date: Wed, 16 Feb 2022 09:29:45 -0800 Subject: null_blk: remove hardcoded alloc_cmd() parameter Only caller of alloc_cmd() is null_submit_bio() unconditionally sets second parameter to true and that is statically hard-coded in null_blk. There is no point in having statically hardcoded function parameter. Remove the unnecessary parameter can_wait and adjust the code so it can retain existing behavior of waiting when we don't get valid nullb_cmd from __alloc_cmd() in alloc_cmd(). The restructured code avoids multiple return statements, multiple calls to __alloc_cmd() and resulting a fast path call to prepare_to_wait() due to removal of first alloc_cmd() call. Follow the pattern that we have in bio_alloc() to set the structure members in the structure allocation function in alloc_cmd() and pass bio to initialize newly allocated cmd->bio member. Follow the pattern in copy_to_nullb() to use result of one function call (null_cache_active()) to be used as a parameter to another function call (null_insert_page()), use result of alloc_cmd() as a first parameter to the null_handle_cmd() in null_submit_bio() function. This allow us to remove the local variable cmd on stack in null_submit_bio() that is in fast path. Signed-off-by: Chaitanya Kulkarni Reviewed-by: Damien Le Moal Link: https://lore.kernel.org/r/20220216172945.31124-2-kch@nvidia.com Signed-off-by: Jens Axboe --- drivers/block/null_blk/main.c | 29 ++++++++++++----------------- 1 file changed, 12 insertions(+), 17 deletions(-) (limited to 'drivers/block/null_blk/main.c') diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c index 90b6bd2a114b..29e183719e77 100644 --- a/drivers/block/null_blk/main.c +++ b/drivers/block/null_blk/main.c @@ -720,26 +720,25 @@ static struct nullb_cmd *__alloc_cmd(struct nullb_queue *nq) return NULL; } -static struct nullb_cmd *alloc_cmd(struct nullb_queue *nq, int can_wait) +static struct nullb_cmd *alloc_cmd(struct nullb_queue *nq, struct bio *bio) { struct nullb_cmd *cmd; DEFINE_WAIT(wait); - cmd = __alloc_cmd(nq); - if (cmd || !can_wait) - return cmd; - do { - prepare_to_wait(&nq->wait, &wait, TASK_UNINTERRUPTIBLE); + /* + * This avoids multiple return statements, multiple calls to + * __alloc_cmd() and a fast path call to prepare_to_wait(). + */ cmd = __alloc_cmd(nq); - if (cmd) - break; - + if (cmd) { + cmd->bio = bio; + return cmd; + } + prepare_to_wait(&nq->wait, &wait, TASK_UNINTERRUPTIBLE); io_schedule(); + finish_wait(&nq->wait, &wait); } while (1); - - finish_wait(&nq->wait, &wait); - return cmd; } static void end_cmd(struct nullb_cmd *cmd) @@ -1477,12 +1476,8 @@ static void null_submit_bio(struct bio *bio) sector_t nr_sectors = bio_sectors(bio); struct nullb *nullb = bio->bi_bdev->bd_disk->private_data; struct nullb_queue *nq = nullb_to_queue(nullb); - struct nullb_cmd *cmd; - - cmd = alloc_cmd(nq, 1); - cmd->bio = bio; - null_handle_cmd(cmd, sector, nr_sectors, bio_op(bio)); + null_handle_cmd(alloc_cmd(nq, bio), sector, nr_sectors, bio_op(bio)); } static bool should_timeout_request(struct request *rq) -- cgit v1.2.3