Re: [PATCH] btrfs: manage subvolid mount option as %u

[Anand Jain <anand.jain@oracle.com>]

On 02/14/2018 12:10 AM, David Sterba wrote:
> On Tue, Feb 13, 2018 at 05:50:43PM +0800, Anand Jain wrote:
>> As -o subvolid mount option is an u64 manage it as %u for
>> token verifications, instead of %s.
>>
>> Signed-off-by: Anand Jain <anand.jain@oracle.com>
>> ---
>>   fs/btrfs/super.c | 23 ++++++++++-------------
>>   1 file changed, 10 insertions(+), 13 deletions(-)
>>
>> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
>> index 8112619cac95..bf629c8a6a47 100644
>> --- a/fs/btrfs/super.c
>> +++ b/fs/btrfs/super.c
>> @@ -336,7 +336,7 @@ enum {
>>   static const match_table_t tokens = {
>>   	{Opt_degraded, "degraded"},
>>   	{Opt_subvol, "subvol=%s"},
>> -	{Opt_subvolid, "subvolid=%s"},
>> +	{Opt_subvolid, "subvolid=%u"},
> 
> This gets implemented as simple_strtoul, deep in the perser it uses an
> unsigned long long and then casts to usigned long. Long and long-long
> are same only on subset of architectures, so we'd need to either extend
> teh parser capabilities to really do u64 or we'd have to use the %s and
> match_u64.

  For now I would use %s and match_u64.

> Though a subvolid larger than full 32bit number is unlikely, for sake of
> correctness I think we should stick to the constraints of the subvolid
> that allows u64.

  Agree.

>>   	{Opt_device, "device=%s"},
>>   	{Opt_nodatasum, "nodatasum"},
>>   	{Opt_datasum, "datasum"},
>> @@ -964,8 +964,8 @@ static int btrfs_parse_subvol_options(const char *options, fmode_t flags,
>>   {
>>   	substring_t args[MAX_OPT_ARGS];
>>   	char *opts, *orig, *p;
>> -	char *num = NULL;
>>   	int error = 0;
>> +	u64 subvolid;
>>   
>>   	if (!options)
>>   		return 0;
>> @@ -995,18 +995,15 @@ static int btrfs_parse_subvol_options(const char *options, fmode_t flags,
>>   			}
>>   			break;
>>   		case Opt_subvolid:
>> -			num = match_strdup(&args[0]);
>> -			if (num) {
>> -				*subvol_objectid = memparse(num, NULL);
>> -				kfree(num);
>> -				/* we want the original fs_tree */
>> -				if (!*subvol_objectid)
>> -					*subvol_objectid =
>> -						BTRFS_FS_TREE_OBJECTID;
>> -			} else {
>> -				error = -EINVAL;
>> +			error = match_u64(&args[0], &subvolid);
> 
> So this is the right way (with the %s), as memparse accepts the size
> suffixes (K/M/G/...), that we don't want for a subvolume id.

  Fixed in V2. Pls find.

Thanks, Anand


>> +			if (error)
>>   				goto out;
>> -			}
>> +
>> +			/* we want the original fs_tree */
>> +			if (subvolid == 0)
>> +				subvolid = BTRFS_FS_TREE_OBJECTID;
>> +
>> +			*subvol_objectid = subvolid;
>>   			break;
>>   		case Opt_subvolrootid:
>>   			pr_warn("BTRFS: 'subvolrootid' mount option is deprecated and has no effect\n");
>> -- 
>> 2.7.0
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>