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Commit 758a58d0 authored by Dongli Zhang's avatar Dongli Zhang Committed by Jens Axboe
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loop: set GENHD_FL_NO_PART_SCAN after blkdev_reread_part() 



Commit 0da03cab
("loop: Fix deadlock when calling blkdev_reread_part()") moves
blkdev_reread_part() out of the loop_ctl_mutex. However,
GENHD_FL_NO_PART_SCAN is set before __blkdev_reread_part(). As a result,
__blkdev_reread_part() will fail the check of GENHD_FL_NO_PART_SCAN and
will not rescan the loop device to delete all partitions.

Below are steps to reproduce the issue:

step1 # dd if=/dev/zero of=tmp.raw bs=1M count=100
step2 # losetup -P /dev/loop0 tmp.raw
step3 # parted /dev/loop0 mklabel gpt
step4 # parted -a none -s /dev/loop0 mkpart primary 64s 1
step5 # losetup -d /dev/loop0

Step5 will not be able to delete /dev/loop0p1 (introduced by step4) and
there is below kernel warning message:

[  464.414043] __loop_clr_fd: partition scan of loop0 failed (rc=-22)

This patch sets GENHD_FL_NO_PART_SCAN after blkdev_reread_part().

Fixes: 0da03cab ("loop: Fix deadlock when calling blkdev_reread_part()")
Signed-off-by: default avatarDongli Zhang <dongli.zhang@oracle.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 40853d6f

drivers/block/loop.c

+17 −4
Original line number Diff line number Diff line
@@ -1089,16 +1089,12 @@ static int __loop_clr_fd(struct loop_device *lo, bool release) 
		kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);

	}

	mapping_set_gfp_mask(filp->f_mapping, gfp);

	lo->lo_state = Lo_unbound;

	/* This is safe: open() is still holding a reference. */

	module_put(THIS_MODULE);

	blk_mq_unfreeze_queue(lo->lo_queue);



	partscan = lo->lo_flags & LO_FLAGS_PARTSCAN && bdev;

	lo_number = lo->lo_number;

	lo->lo_flags = 0;

	if (!part_shift)

		lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;

	loop_unprepare_queue(lo);

out_unlock:

	mutex_unlock(&loop_ctl_mutex);
@@ -1121,6 +1117,23 @@ static int __loop_clr_fd(struct loop_device *lo, bool release) 
		/* Device is gone, no point in returning error */

		err = 0;

	}



	/*

	 * lo->lo_state is set to Lo_unbound here after above partscan has

	 * finished.

	 *

	 * There cannot be anybody else entering __loop_clr_fd() as

	 * lo->lo_backing_file is already cleared and Lo_rundown state

	 * protects us from all the other places trying to change the 'lo'

	 * device.

	 */

	mutex_lock(&loop_ctl_mutex);

	lo->lo_flags = 0;

	if (!part_shift)

		lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;

	lo->lo_state = Lo_unbound;

	mutex_unlock(&loop_ctl_mutex);



	/*

	 * Need not hold loop_ctl_mutex to fput backing file.

	 * Calling fput holding loop_ctl_mutex triggers a circular