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dm: avoid filesystem lookup in dm_get_dev_t()

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commit 809b1e4945774c9ec5619a8f4e2189b7b3833c0c upstream.

This reverts commit
644bda6f34 ("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: 644bda6f34 ("dm table: fall back to getting device using name_to_dev_t()")
Cc: stable@vger.kernel.org
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin Wilck <mwilck@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Hannes Reinecke 2021-01-21 18:50:56 +01:00 committed by Greg Kroah-Hartman
parent 4749ffd9c4
commit 5a5095ac9e
1 changed files with 12 additions and 3 deletions
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15
drivers/md/dm-table.c
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@ -370,14 +370,23 @@ 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);
dev = dm_get_dev_t(path);
if (!dev)
return -ENODEV;
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) {