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@xxxxxxxxxx>
---
drivers/block/null_blk/main.c | 29 ++++++++++++-----------------
1 file changed, 12 insertions(+), 17 deletions(-)
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)
--
2.29.0
