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null_blk: remove hardcoded alloc_cmd() parameter

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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 <kch@nvidia.com>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Link: https://lore.kernel.org/r/20220216172945.31124-2-kch@nvidia.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Chaitanya Kulkarni 2022-02-16 09:29:45 -08:00 committed by Jens Axboe
parent ef44c50837
commit 3d3472f3ed
1 changed files with 12 additions and 17 deletions
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29
drivers/block/null_blk/main.c
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@ -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)