block: Fix bdi assignment to bdev inode when racing with disk delete

When disk->fops->open() in __blkdev_get() returns -ERESTARTSYS, we
restart the process of opening the block device. However we forget to
switch bdev->bd_bdi back to noop_backing_dev_info and as a result bdev
inode will be pointing to a stale bdi. Fix the problem by setting
bdev->bd_bdi later when __blkdev_get() is already guaranteed to succeed.

Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 3 insertions, 4 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 2eca00ec4370..53e2389ae4d4 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1556,8 +1556,6 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
                 bdev->bd_disk = disk;
                 bdev->bd_queue = disk->queue;
                 bdev->bd_contains = bdev;
-                if (bdev->bd_bdi == &noop_backing_dev_info)
-                        bdev->bd_bdi = bdi_get(disk->queue->backing_dev_info);
 
                 if (!partno) {
                         ret = -ENXIO;
@@ -1622,6 +1620,9 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
                         }
                         bd_set_size(bdev, (loff_t)bdev->bd_part->nr_sects << 9);
                 }
+
+                if (bdev->bd_bdi == &noop_backing_dev_info)
+                        bdev->bd_bdi = bdi_get(disk->queue->backing_dev_info);
         } else {
                 if (bdev->bd_contains == bdev) {
                         ret = 0;
@@ -1653,8 +1654,6 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
         bdev->bd_disk = NULL;
         bdev->bd_part = NULL;
         bdev->bd_queue = NULL;
-        bdi_put(bdev->bd_bdi);
-        bdev->bd_bdi = &noop_backing_dev_info;
         if (bdev != bdev->bd_contains)
                 __blkdev_put(bdev->bd_contains, mode, 1);
         bdev->bd_contains = NULL;