[PATCH v3 07/15] md/raid5: Drop the do_prepare flag in raid5_make_request()

From: Logan Gunthorpe
Date: Thu Jun 16 2022 - 15:20:57 EST


prepare_to_wait() can be reasonably called after schedule instead of
setting a flag and preparing in the next loop iteration.

This means that prepare_to_wait() will be called before
read_seqcount_begin(), but there shouldn't be any reason that the order
matters here. On the first iteration of the loop prepare_to_wait() is
already called first.

Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Guoqing Jiang <guoqing.jiang@xxxxxxxxx>
---
drivers/md/raid5.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 26ef292842de..c58e70db204a 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5918,7 +5918,6 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
const int rw = bio_data_dir(bi);
enum stripe_result res;
DEFINE_WAIT(w);
- bool do_prepare;

if (unlikely(bi->bi_opf & REQ_PREFLUSH)) {
int ret = log_handle_flush_request(conf, bi);
@@ -5976,12 +5975,8 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
for (; logical_sector < last_sector; logical_sector += RAID5_STRIPE_SECTORS(conf)) {
int seq;

- do_prepare = false;
retry:
seq = read_seqcount_begin(&conf->gen_lock);
- if (do_prepare)
- prepare_to_wait(&conf->wait_for_overlap, &w,
- TASK_UNINTERRUPTIBLE);

res = make_stripe_request(mddev, conf, &ctx, logical_sector,
bi, seq);
@@ -5993,7 +5988,8 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)

if (res == STRIPE_SCHEDULE_AND_RETRY) {
schedule();
- do_prepare = true;
+ prepare_to_wait(&conf->wait_for_overlap, &w,
+ TASK_UNINTERRUPTIBLE);
goto retry;
}
}
--
2.30.2