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 3d39f5d..7640016 100644
--- 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);
}