block: fix handling of dead zone write plugs

block/blk-zoned.c

@@ -623,6 +623,28 @@ static void disk_mark_zone_wplug_dead(struct blk_zone_wplug *zwplug)
 	}
 }
 
+static inline bool disk_check_zone_wplug_dead(struct blk_zone_wplug *zwplug)
+{
+	if (!(zwplug->flags & BLK_ZONE_WPLUG_DEAD))
+		return false;
+
+	/*
+	 * If a new write is received right after a zone reset completes and
+	 * while the disk_zone_wplugs_worker() thread has not yet released the
+	 * reference on the zone write plug after processing the last write to
+	 * the zone, then the new write BIO will see the zone write plug marked
+	 * as dead. This case is however a false positive and a perfectly valid
+	 * pattern. In such case, restore the zone write plug to a live one.
+	 */
+	if (!zwplug->wp_offset && bio_list_empty(&zwplug->bio_list)) {
+		zwplug->flags &= ~BLK_ZONE_WPLUG_DEAD;
+		refcount_inc(&zwplug->ref);
+		return false;
+	}
+
+	return true;
+}
+
 static bool disk_zone_wplug_submit_bio(struct gendisk *disk,
 				       struct blk_zone_wplug *zwplug);
 
@@ -1444,12 +1466,12 @@ static bool blk_zone_wplug_handle_write(struct bio *bio, unsigned int nr_segs)
 	spin_lock_irqsave(&zwplug->lock, flags);
 
 	/*
-	 * If we got a zone write plug marked as dead, then the user is issuing
-	 * writes to a full zone, or without synchronizing with zone reset or
-	 * zone finish operations. In such case, fail the BIO to signal this
-	 * invalid usage.
+	 * Check if we got a zone write plug marked as dead. If yes, then the
+	 * user is likely issuing writes to a full zone, or without
+	 * synchronizing with zone reset or zone finish operations. In such
+	 * case, fail the BIO to signal this invalid usage.
 	 */
-	if (zwplug->flags & BLK_ZONE_WPLUG_DEAD) {
+	if (disk_check_zone_wplug_dead(zwplug)) {
 		spin_unlock_irqrestore(&zwplug->lock, flags);
 		disk_put_zone_wplug(zwplug);
 		bio_io_error(bio);