From a03ce9cc4bb880a27a42987b378b044a6d207b8b Mon Sep 17 00:00:00 2001 From: Hannes Reinecke Date: Thu, 21 Jan 2021 18:50:56 +0100 Subject: [PATCH] dm: avoid filesystem lookup in dm_get_dev_t() commit 809b1e4945774c9ec5619a8f4e2189b7b3833c0c upstream. This reverts commit 644bda6f3460 ("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: 644bda6f3460 ("dm table: fall back to getting device using name_to_dev_t()") Cc: stable@vger.kernel.org Signed-off-by: Hannes Reinecke Signed-off-by: Martin Wilck Reviewed-by: Christoph Hellwig Signed-off-by: Mike Snitzer Signed-off-by: Greg Kroah-Hartman --- drivers/md/dm-table.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index 6dd56afa048c..98be040cf958 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -428,14 +428,23 @@ 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) {