Merge tag 'md/4.0-fixes' of git://neil.brown.name/md

Pull md fixes from Neil Brown:
 "Three md fixes:

   - fix a read-balance problem that was reported 2 years ago, but that
     I never noticed the report :-(

   - fix for rare RAID6 problem causing incorrect bitmap updates when
     two devices fail.

   - add __ATTR_PREALLOC annotation now that it is possible"

* tag 'md/4.0-fixes' of git://neil.brown.name/md:
  md: mark some attributes as pre-alloc
  raid5: check faulty flag for array status during recovery.
  md/raid1: fix read balance when a drive is write-mostly.

1 files changed, 9 insertions, 4 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index e75d48c0421a..cd2f96b2c572 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5121,12 +5121,17 @@ static inline sector_t sync_request(struct mddev *mddev, sector_t sector_nr, int
 		schedule_timeout_uninterruptible(1);
 	}
 	/* Need to check if array will still be degraded after recovery/resync
-	 * We don't need to check the 'failed' flag as when that gets set,
-	 * recovery aborts.
+	 * Note in case of > 1 drive failures it's possible we're rebuilding
+	 * one drive while leaving another faulty drive in array.
 	 */
-	for (i = 0; i < conf->raid_disks; i++)
-		if (conf->disks[i].rdev == NULL)
+	rcu_read_lock();
+	for (i = 0; i < conf->raid_disks; i++) {
+		struct md_rdev *rdev = ACCESS_ONCE(conf->disks[i].rdev);
+
+		if (rdev == NULL || test_bit(Faulty, &rdev->flags))
 			still_degraded = 1;
+	}
+	rcu_read_unlock();
 
 	bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, still_degraded);