md/raid5: Drop the do_prepare flag in raid5_make_request()

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@deltatee.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 018b9ab..0eb75b0 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5919,7 +5919,6 @@ 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);
@@ -5977,12 +5976,8 @@ 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);
@@ -5994,7 +5989,8 @@ 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;
                }
        }