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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>
This commit is contained in:
Anand Jain 2020-09-30 21:09:52 +08:00 committed by David Sterba
parent 572c83acdc
commit 96c2e067ed
2 changed files with 18 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
fs/btrfs/disk-io.c
View File

@ -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);
}

18
fs/btrfs/volumes.c
View File

@ -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;