Commit 06f0e9e6 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

block: loop: fix another reread part failure 



loop_clr_fd() can be run piggyback with lo_release(), and
under this situation, reread partition may always fail because
bd_mutex has been held already.

This patch detects the situation by the reference count, and
call __blkdev_reread_part() to avoid acquiring the lock again.

In the meantime, this patch switches to new kernel APIs
of blkdev_reread_part() and __blkdev_reread_part().

Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Tested-by: default avatarJarod Wilson <jarod@redhat.com>
Acked-by: default avatarJarod Wilson <jarod@redhat.com>
Signed-off-by: default avatarJarod Wilson <jarod@redhat.com>
Signed-off-by: default avatarMing Lei <ming.lei@canonical.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent f8933667

drivers/block/loop.c

+26 −4
Original line number Diff line number Diff line
@@ -474,6 +474,28 @@ static int loop_flush(struct loop_device *lo) 
	return loop_switch(lo, NULL);

}



static void loop_reread_partitions(struct loop_device *lo,

				   struct block_device *bdev)

{

	int rc;



	/*

	 * bd_mutex has been held already in release path, so don't

	 * acquire it if this function is called in such case.

	 *

	 * If the reread partition isn't from release path, lo_refcnt

	 * must be at least one and it can only become zero when the

	 * current holder is released.

	 */

	if (!atomic_read(&lo->lo_refcnt))

		rc = __blkdev_reread_part(bdev);

	else

		rc = blkdev_reread_part(bdev);

	if (rc)

		pr_warn("%s: partition scan of loop%d (%s) failed (rc=%d)\n",

			__func__, lo->lo_number, lo->lo_file_name, rc);

}



/*

 * loop_change_fd switched the backing store of a loopback device to

 * a new file. This is useful for operating system installers to free up
@@ -522,7 +544,7 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev, 


	fput(old_file);

	if (lo->lo_flags & LO_FLAGS_PARTSCAN)

		ioctl_by_bdev(bdev, BLKRRPART, 0);

		loop_reread_partitions(lo, bdev);

	return 0;



 out_putf:
@@ -759,7 +781,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode, 
	if (part_shift)

		lo->lo_flags |= LO_FLAGS_PARTSCAN;

	if (lo->lo_flags & LO_FLAGS_PARTSCAN)

		ioctl_by_bdev(bdev, BLKRRPART, 0);

		loop_reread_partitions(lo, bdev);



	/* Grab the block_device to prevent its destruction after we

	 * put /dev/loopXX inode. Later in loop_clr_fd() we bdput(bdev).
@@ -877,7 +899,7 @@ static int loop_clr_fd(struct loop_device *lo) 
	blk_mq_unfreeze_queue(lo->lo_queue);



	if (lo->lo_flags & LO_FLAGS_PARTSCAN && bdev)

		ioctl_by_bdev(bdev, BLKRRPART, 0);

		loop_reread_partitions(lo, bdev);

	lo->lo_flags = 0;

	if (!part_shift)

		lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
@@ -954,7 +976,7 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info) 
	     !(lo->lo_flags & LO_FLAGS_PARTSCAN)) {

		lo->lo_flags |= LO_FLAGS_PARTSCAN;

		lo->lo_disk->flags &= ~GENHD_FL_NO_PART_SCAN;

		ioctl_by_bdev(lo->lo_device, BLKRRPART, 0);

		loop_reread_partitions(lo, lo->lo_device);

	}



	lo->lo_encrypt_key_size = info->lo_encrypt_key_size;

CRA Git | Maintained and supported by SUSTech CRA and CCSE