On 2019/1/8 下午7:16, Filipe Manana wrote:
> On Tue, Jan 8, 2019 at 6:11 AM Qu Wenruo <wqu@suse.com> wrote:
>>
>> [BUG]
>> Linux v5.0-rc1 will fail fstests/btrfs/163 with the following kernel
>> message:
>>
>>   BTRFS error (device dm-6): dev extent devid 1 physical offset 13631488 len 8388608 is beyond device boundary 0
>>   BTRFS error (device dm-6): failed to verify dev extents against chunks: -117
>>   BTRFS error (device dm-6): open_ctree failed
>>
>> [CAUSE]
>> Commit cf90d884b347 ("btrfs: Introduce mount time chunk <-> dev extent
>> mapping check") introduced strict check on dev extents.
>>
>> We use btrfs_find_device() with dev uuid and fs uuid set to NULL, and
>> only dependent on @devid to find the real device.
>>
>> For seed devices, we call clone_fs_devices() in open_seed_devices() to
>> allow us search seed devices directly.
>>
>> However clone_fs_devices() just populates devices with devid and dev
>> uuid, without populating other essential members, like disk_total_bytes.
>>
>> This makes any device returned by btrfs_find_device(fs_info, devid,
>> NULL, NULL) is just a dummy, with 0 disk_total_bytes, and any dev
>> extents on the seed device will not pass the device boundary check.
>>
>> [FIX]
>> This patch will try to verify the device returned by btrfs_find_device()
>> and if it's a dummy then re-search in seed devices.
>>
>> Reported-by: Filipe Manana <fdmanana@suse.com>
>> Fixes: cf90d884b347 ("btrfs: Introduce mount time chunk <-> dev extent mapping check")
>> Signed-off-by: Qu Wenruo <wqu@suse.com>
>> ---
>>  fs/btrfs/volumes.c | 12 ++++++++++++
>>  1 file changed, 12 insertions(+)
>>
>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>> index 2576b1a379c9..3e4f8f88353e 100644
>> --- a/fs/btrfs/volumes.c
>> +++ b/fs/btrfs/volumes.c
>> @@ -7825,6 +7825,18 @@ static int verify_one_dev_extent(struct btrfs_fs_info *fs_info,
>>                 ret = -EUCLEAN;
>>                 goto out;
>>         }
>> +
>> +       /* It's possible this device is a dummy for seed device */
>> +       if (dev->disk_total_bytes == 0) {
>> +               dev = find_device(fs_info->fs_devices->seed, devid, NULL);
>> +               if (!dev) {
>> +                       btrfs_err(fs_info, "failed to find seed devid %llu",
>> +                                 devid);
>> +                       ret = -EUCLEAN;
>> +                       goto out;
>> +               }
>> +       }
> 
> Why just not pass the FSID (can be taken from fs_info->super_copy) to
> the previous call to btrfs_find_device()?
> It's a lot simpler.

Then btrfs_find_device() will just return NULL.
We still need to verify the dev extent of the seed device not to exceed
seed device boundary.

What we need is device uuid, however we can't easily get that dev uuid
from dev extent item.

Thanks,
Qu

> 
>> +
>>         if (physical_offset + physical_len > dev->disk_total_bytes) {
>>                 btrfs_err(fs_info,
>>  "dev extent devid %llu physical offset %llu len %llu is beyond device boundary %llu",
>> --
>> 2.20.1
>>
> 
>