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>

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 2eca00ec43706bb78955cd221a24593942625d57..53e2389ae4d4e7902de07a67cf4814a4d6553496 100644 (file)
--- 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;