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Commit 3f47fe64 authored by Hannes Reinecke's avatar Hannes Reinecke Committed by Greg Kroah-Hartman
Browse files

dm: avoid filesystem lookup in dm_get_dev_t() 



commit 809b1e4945774c9ec5619a8f4e2189b7b3833c0c upstream.

This reverts commit
644bda6f ("dm table: fall back to getting device using name_to_dev_t()")

dm_get_dev_t() is just used to convert an arbitrary 'path' string
into a dev_t. It doesn't presume that the device is present; that
check will be done later, as the only caller is dm_get_device(),
which does a dm_get_table_device() later on, which will properly
open the device.

So if the path string already _is_ in major:minor representation
we can convert it directly, avoiding a recursion into the filesystem
to lookup the block device.

This avoids a hang in multipath_message() when the filesystem is
inaccessible.

Fixes: 644bda6f ("dm table: fall back to getting device using name_to_dev_t()")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarHannes Reinecke <hare@suse.de>
Signed-off-by: default avatarMartin Wilck <mwilck@suse.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 5c9546d5

drivers/md/dm-table.c

+12 −3
Original line number Diff line number Diff line
@@ -396,14 +396,23 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, 
{

	int r;

	dev_t dev;

	unsigned int major, minor;

	char dummy;

	struct dm_dev_internal *dd;

	struct dm_table *t = ti->table;



	BUG_ON(!t);



	if (sscanf(path, "%u:%u%c", &major, &minor, &dummy) == 2) {

		/* Extract the major/minor numbers */

		dev = MKDEV(major, minor);

		if (MAJOR(dev) != major || MINOR(dev) != minor)

			return -EOVERFLOW;

	} else {

		dev = dm_get_dev_t(path);

		if (!dev)

			return -ENODEV;

	}



	dd = find_device(&t->devices, dev);

	if (!dd) {