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btrfs: harden identification of a stale device

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Identifying and removing the stale device from the fs_uuids list is done
by btrfs_free_stale_devices().  btrfs_free_stale_devices() in turn
depends on device_path_matched() to check if the device appears in more
than one btrfs_device structure.

The matching of the device happens by its path, the device path. However,
when device mapper is in use, the dm device paths are nothing but a link
to the actual block device, which leads to the device_path_matched()
failing to match.

Fix this by matching the dev_t as provided by lookup_bdev() instead of
plain string compare of the device paths.

Reported-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Anand Jain 2022-01-12 13:05:59 +08:00 committed by David Sterba
parent bef16b5298
commit 770c79fb65
1 changed files with 38 additions and 7 deletions
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45
fs/btrfs/volumes.c
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@ -534,15 +534,48 @@ error:
return ret;
}
static bool device_path_matched(const char *path, struct btrfs_device *device)
/*
* Check if the device in the path matches the device in the given struct device.
*
* Returns:
* true If it is the same device.
* false If it is not the same device or on error.
*/
static bool device_matched(const struct btrfs_device *device, const char *path)
{
int found;
char *device_name;
dev_t dev_old;
dev_t dev_new;
int ret;
/*
* If we are looking for a device with the matching dev_t, then skip
* device without a name (a missing device).
*/
if (!device->name)
return false;
device_name = kzalloc(BTRFS_PATH_NAME_MAX, GFP_KERNEL);
if (!device_name)
return false;
rcu_read_lock();
found = strcmp(rcu_str_deref(device->name), path);
scnprintf(device_name, BTRFS_PATH_NAME_MAX, "%s", rcu_str_deref(device->name));
rcu_read_unlock();
return found == 0;
ret = lookup_bdev(device_name, &dev_old);
kfree(device_name);
if (ret)
return false;
ret = lookup_bdev(path, &dev_new);
if (ret)
return false;
if (dev_old == dev_new)
return true;
return false;
}
/*
@ -575,9 +608,7 @@ static int btrfs_free_stale_devices(const char *path,
&fs_devices->devices, dev_list) {
if (skip_device && skip_device == device)
continue;
if (path && !device->name)
continue;
if (path && !device_path_matched(path, device))
if (path && !device_matched(device, path))
continue;
if (fs_devices->opened) {
/* for an already deleted device return 0 */