block: opencode devcgroup_inode_permission

Just call devcgroup_check_permission to avoid various superflous checks
and a double conversion of the access flags.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/block_dev.c

@@ -1520,15 +1520,13 @@ static int blkdev_get(struct block_device *bdev, fmode_t mode, void *holder)
 	struct block_device *claiming;
 	bool unblock_events = true;
 	struct gendisk *disk;
-	int perm = 0;
 	int partno;
 	int ret;
 
-	if (mode & FMODE_READ)
-		perm |= MAY_READ;
-	if (mode & FMODE_WRITE)
-		perm |= MAY_WRITE;
-	ret = devcgroup_inode_permission(bdev->bd_inode, perm);
+	ret = devcgroup_check_permission(DEVCG_DEV_BLOCK,
+			imajor(bdev->bd_inode), iminor(bdev->bd_inode),
+			((mode & FMODE_READ) ? DEVCG_ACC_READ : 0) |
+			((mode & FMODE_WRITE) ? DEVCG_ACC_WRITE : 0));
 	if (ret)
 		goto bdput;