sbitmap: Protect swap_lock from softirqs

The swap_lock used by sbitmap has a chain with locks taken from softirq,
but the swap_lock is not protected from being preempted by softirqs.

A chain exists of:

 sbq->ws[i].wait -> dispatch_wait_lock -> swap_lock

Where the sbq->ws[i].wait lock can be taken from softirq context, which
means all locks below it in the chain must also be protected from
softirqs.

Reported-by: Clark Williams <williams@redhat.com>
Fixes: cd80ddc212fa ("sbitmap: silence bogus lockdep IRQ warning")
Fixes: 5cd47079aec1 ("sbitmap: amortize cost of clearing bits")
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index 65c2d06250a63acd453614011fa42ccd55836beb..864354000e04d65f12e9586a6cf80cad463a7117 100644 (file)
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -26,14 +26,9 @@
 static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index)
 {
        unsigned long mask, val;
-       unsigned long __maybe_unused flags;
        bool ret = false;
 
-       /* Silence bogus lockdep warning */
-#if defined(CONFIG_LOCKDEP)
-       local_irq_save(flags);
-#endif
-       spin_lock(&sb->map[index].swap_lock);
+       spin_lock_bh(&sb->map[index].swap_lock);
 
        if (!sb->map[index].cleared)
                goto out_unlock;
@@ -54,10 +49,7 @@ static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index)
 
        ret = true;
 out_unlock:
-       spin_unlock(&sb->map[index].swap_lock);
-#if defined(CONFIG_LOCKDEP)
-       local_irq_restore(flags);
-#endif
+       spin_unlock_bh(&sb->map[index].swap_lock);
        return ret;
 }