btrfs: skip devices without magic signature when mounting

Many things can happen after the device is scanned and before the device
is mounted.  One such thing is losing the BTRFS_MAGIC on the device.
If it happens we still won't free that device from the memory and cause
the userland confusion.

For example: As the BTRFS_IOC_DEV_INFO still carries the device path
which does not have the BTRFS_MAGIC, 'btrfs fi show' still lists
device which does not belong to the filesystem anymore:

  $ mkfs.btrfs -fq -draid1 -mraid1 /dev/sda /dev/sdb
  $ wipefs -a /dev/sdb
  # /dev/sdb does not contain magic signature
  $ mount -o degraded /dev/sda /btrfs
  $ btrfs fi show -m
  Label: none  uuid: 470ec6fb-646b-4464-b3cb-df1b26c527bd
	  Total devices 2 FS bytes used 128.00KiB
	  devid    1 size 3.00GiB used 571.19MiB path /dev/sda
	  devid    2 size 3.00GiB used 571.19MiB path /dev/sdb

We need to distinguish the missing signature and invalid superblock, so
add a specific error code ENODATA for that. This also fixes failure of
fstest btrfs/198.

CC: stable@vger.kernel.org # 4.19+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 3d39f5d47ad35b790dd3e5063867f3b034760218..764001609a154fac4cf4393ce5cb2e8acc1a59fa 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3424,8 +3424,12 @@ struct btrfs_super_block *btrfs_read_dev_one_super(struct block_device *bdev,
                return ERR_CAST(page);
 
        super = page_address(page);
-       if (btrfs_super_bytenr(super) != bytenr ||
-                   btrfs_super_magic(super) != BTRFS_MAGIC) {
+       if (btrfs_super_magic(super) != BTRFS_MAGIC) {
+               btrfs_release_disk_super(super);
+               return ERR_PTR(-ENODATA);
+       }
+
+       if (btrfs_super_bytenr(super) != bytenr) {
                btrfs_release_disk_super(super);
                return ERR_PTR(-EINVAL);
        }

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 46f4efd586526a6714d58b817bbd0912f03e26d9..58b9c419a2b6b257b61f43a21dd289560878a55e 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1198,17 +1198,23 @@ static int open_fs_devices(struct btrfs_fs_devices *fs_devices,
 {
        struct btrfs_device *device;
        struct btrfs_device *latest_dev = NULL;
+       struct btrfs_device *tmp_device;
 
        flags |= FMODE_EXCL;
 
-       list_for_each_entry(device, &fs_devices->devices, dev_list) {
-               /* Just open everything we can; ignore failures here */
-               if (btrfs_open_one_device(fs_devices, device, flags, holder))
-                       continue;
+       list_for_each_entry_safe(device, tmp_device, &fs_devices->devices,
+                                dev_list) {
+               int ret;
 
-               if (!latest_dev ||
-                   device->generation > latest_dev->generation)
+               ret = btrfs_open_one_device(fs_devices, device, flags, holder);
+               if (ret == 0 &&
+                   (!latest_dev || device->generation > latest_dev->generation)) {
                        latest_dev = device;
+               } else if (ret == -ENODATA) {
+                       fs_devices->num_devices--;
+                       list_del(&device->dev_list);
+                       btrfs_free_device(device);
+               }
        }
        if (fs_devices->open_devices == 0)
                return -EINVAL;