blk-wbt: fix has-sleeper queueing check

BugLink: https://bugs.launchpad.net/bugs/1810998
We need to do this inside the loop as well, or we can allow new
IO to supersede previous IO.

Tested-by: Anchal Agarwal <anchalag@amazon.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
(backported from commit c45e6a037a536530bd25781ac7c989e52deb2a63)
[mfo: backport:
 - hunk 1: s/rq_wait_inc_below(rqw/atomic_inc_below(&rqw->inflight/]
Signed-off-by: Mauricio Faria de Oliveira <mfo@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index 036a676de09ce352d325b07f793226643b19b173..b2fe2682b3f95a7337f51b2bf791513441fb519d 100644 (file)
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -523,16 +523,17 @@ static void __wbt_wait(struct rq_wb *rwb, enum wbt_flags wb_acct,
 {
        struct rq_wait *rqw = get_rq_wait(rwb, wb_acct);
        DECLARE_WAITQUEUE(wait, current);
+       bool has_sleeper;
 
-       if (!wq_has_sleeper(&rqw->wait) &&
-           atomic_inc_below(&rqw->inflight, get_limit(rwb, rw)))
+       has_sleeper = wq_has_sleeper(&rqw->wait);
+       if (!has_sleeper && atomic_inc_below(&rqw->inflight, get_limit(rwb, rw)))
                return;
 
        add_wait_queue_exclusive(&rqw->wait, &wait);
        do {
                set_current_state(TASK_UNINTERRUPTIBLE);
 
-               if (atomic_inc_below(&rqw->inflight, get_limit(rwb, rw)))
+               if (!has_sleeper && atomic_inc_below(&rqw->inflight, get_limit(rwb, rw)))
                        break;
 
                if (lock) {
@@ -541,6 +542,7 @@ static void __wbt_wait(struct rq_wb *rwb, enum wbt_flags wb_acct,
                        spin_lock_irq(lock);
                } else
                        io_schedule();
+               has_sleeper = false;
        } while (1);
 
        __set_current_state(TASK_RUNNING);