md/raid5: Convert prepare_to_wait() to wait_woken() api

raid5_get_active_stripe() can sleep in various situations and it
is called by make_stripe_request() while inside the
prepare_to_wait()/finish_wait() section. Nested waits like this are
not supported.

This was noticed while making other changes that add different sleeps
to raid5_get_active_stripe() that caused a WARNING with
CONFIG_DEBUG_ATOMIC_SLEEP.

No ill effects have been noticed with the code as is, but theoretically
a nested and here could cause a dead lock so it should be fixed.

To fix this, convert the prepare_to_wait() call to use wake_woken()
which supports nested sleeps.

Link: https://lwn.net/Articles/628628/
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
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 2690298bd92baef1ae8baf681e74d79172035504..6a6f7d969198327d5d001eeed8877c6bf5dc8ade 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6044,12 +6044,12 @@ out_release:
 
 static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
 {
+       DEFINE_WAIT_FUNC(wait, woken_wake_function);
        struct r5conf *conf = mddev->private;
        sector_t logical_sector;
        struct stripe_request_ctx ctx = {};
        const int rw = bio_data_dir(bi);
        enum stripe_result res;
-       DEFINE_WAIT(w);
        int s, stripe_cnt;
 
        if (unlikely(bi->bi_opf & REQ_PREFLUSH)) {
@@ -6112,7 +6112,8 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
                return true;
        }
        md_account_bio(mddev, &bi);
-       prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);
+
+       add_wait_queue(&conf->wait_for_overlap, &wait);
        while (1) {
                res = make_stripe_request(mddev, conf, &ctx, logical_sector,
                                          bi);
@@ -6135,9 +6136,8 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
                                ctx.batch_last = NULL;
                        }
 
-                       schedule();
-                       prepare_to_wait(&conf->wait_for_overlap, &w,
-                                       TASK_UNINTERRUPTIBLE);
+                       wait_woken(&wait, TASK_UNINTERRUPTIBLE,
+                                  MAX_SCHEDULE_TIMEOUT);
                        continue;
                }
 
@@ -6148,8 +6148,7 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
                logical_sector = ctx.first_sector +
                        (s << RAID5_STRIPE_SHIFT(conf));
        }
-
-       finish_wait(&conf->wait_for_overlap, &w);
+       remove_wait_queue(&conf->wait_for_overlap, &wait);
 
        if (ctx.batch_last)
                raid5_release_stripe(ctx.batch_last);