From: Ming Lei <ming.lei@redhat.com>
Date: Tue, 15 Jan 2019 03:59:52 +0000 (+0800)
Subject: sbitmap: Protect swap_lock from hardirq
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=fe76fc6aaf538df27708ffa3e5d549a6c8e16142;p=openwrt%2Fstaging%2Fblogic.git

sbitmap: Protect swap_lock from hardirq

Because we may call blk_mq_get_driver_tag() directly from
blk_mq_dispatch_rq_list() without holding any lock, then HARDIRQ may
come and the above DEADLOCK is triggered.

Commit ab53dcfb3e7b ("sbitmap: Protect swap_lock from hardirq") tries to
fix this issue by using 'spin_lock_bh', which isn't enough because we
complete request from hardirq context direclty in case of multiqueue.

Cc: Clark Williams <williams@redhat.com>
Fixes: ab53dcfb3e7b ("sbitmap: Protect swap_lock from hardirq")
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index 864354000e04..5b382c1244ed 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -27,8 +27,9 @@ static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index)
 {
 	unsigned long mask, val;
 	bool ret = false;
+	unsigned long flags;
 
-	spin_lock_bh(&sb->map[index].swap_lock);
+	spin_lock_irqsave(&sb->map[index].swap_lock, flags);
 
 	if (!sb->map[index].cleared)
 		goto out_unlock;
@@ -49,7 +50,7 @@ static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index)
 
 	ret = true;
 out_unlock:
-	spin_unlock_bh(&sb->map[index].swap_lock);
+	spin_unlock_irqrestore(&sb->map[index].swap_lock, flags);
 	return ret;
 }