On 2018年01月08日 13:13, Anand Jain wrote:
>
>
> On 01/08/2018 01:08 PM, Qu Wenruo wrote:
>>
>>
>> On 2018年01月08日 13:04, Anand Jain wrote:
>>> Userland sets SUPER_FLAG_CHANGING_FSID and resets it only when changing
>>> fsid is complete. Its not a good idea to mount the device anything in
>>> between, so this patch fails the mount if SB SUPER_FLAG_CHANGING_FSID
>>> is set.
>>>
>>> Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
>>> cc: wqu@xxxxxxxx
>>> ---
>>> v1->v2: Oops. Fix cut and paste error, remove ~. My bad.
>>>
>>> fs/btrfs/disk-io.c | 7 ++++++-
>>> include/uapi/linux/btrfs_tree.h | 1 +
>>> 2 files changed, 7 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
>>> index a69e5944dc08..0dd215258ff9 100644
>>> --- a/fs/btrfs/disk-io.c
>>> +++ b/fs/btrfs/disk-io.c
>>> @@ -61,7 +61,8 @@
>>> BTRFS_HEADER_FLAG_RELOC |\
>>> BTRFS_SUPER_FLAG_ERROR |\
>>> BTRFS_SUPER_FLAG_SEEDING |\
>>> - BTRFS_SUPER_FLAG_METADUMP)
>>> + BTRFS_SUPER_FLAG_METADUMP |\
>>> + BTRFS_SUPER_FLAG_CHANGING_FSID)
>>
>> Still the same problem here.
>>
>> Since that super flag is excluded in btrfs_check_super_valid(), I didn't
>> see any meaning including it into BTRFS_SUPER_FLAG_SUPP, and it will
>> confuse later BTRFS_SUPER_FLAG_SUPP users.
>
>
> Anyway BTRFS_SUPER_FLAG_SUPP as such does not stop to mount, it
> just warns. So when there is a new flag which is not supported
> we get this warning. As in the case with BTRFS_SUPER_FLAG_METADUMP_V2.
> BTRFS_SUPER_FLAG_METADUMP_V2 in kernel is defined but not supported.
> However since we are supporting BTRFS_SUPER_FLAG_CHANGING_FSID, so
> adding to BTRFS_SUPER_FLAG_SUPP make sense to me. ?
We still refuse to mount the fs if CHANGING_FSID is set, which I believe
should be called "unsupported"
On the other hand it would be better to include METADUMP_V2 into SUPP,
as we allow it to be mounted and now kernel knows that flag, output a
warning doesn't seems necessary now.
It would be even better to change the later SUPP flags checks, into
something not only output some meaningless numeric flags, but also
output the human readable flags if it's recognized but unsupported. (For
CHANGIND_FSID).
Thanks,
Qu
>
> Thanks, Anand
>
>
>> Thanks,
>> Qu
>>
>>> static const struct extent_io_ops btree_extent_io_ops;
>>> static void end_workqueue_fn(struct btrfs_work *work);
>>> @@ -3906,6 +3907,10 @@ static int btrfs_check_super_valid(struct
>>> btrfs_fs_info *fs_info)
>>> btrfs_err(fs_info, "no valid FS found");
>>> ret = -EINVAL;
>>> }
>>> + if (btrfs_super_flags(sb) & BTRFS_SUPER_FLAG_CHANGING_FSID) {
>>> + btrfs_err(fs_info, "SUPER_FLAG_CHANGING_FSID is set");
>>> + ret = -EINVAL;
>>> + }
>>> if (btrfs_super_flags(sb) & ~BTRFS_SUPER_FLAG_SUPP)
>>> btrfs_warn(fs_info, "unrecognized super flag: %llu",
>>> btrfs_super_flags(sb) & ~BTRFS_SUPER_FLAG_SUPP);
>>> diff --git a/include/uapi/linux/btrfs_tree.h
>>> b/include/uapi/linux/btrfs_tree.h
>>> index 38ab0e06259a..aff1356c2bb8 100644
>>> --- a/include/uapi/linux/btrfs_tree.h
>>> +++ b/include/uapi/linux/btrfs_tree.h
>>> @@ -457,6 +457,7 @@ struct btrfs_free_space_header {
>>> #define BTRFS_SUPER_FLAG_SEEDING (1ULL << 32)
>>> #define BTRFS_SUPER_FLAG_METADUMP (1ULL << 33)
>>> #define BTRFS_SUPER_FLAG_METADUMP_V2 (1ULL << 34)
>>> +#define BTRFS_SUPER_FLAG_CHANGING_FSID (1ULL << 35)
>>> /*
>>>
>>
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