Kyungmin Park <kmpark@xxxxxxxxxxxxx> writes:
>>> + start = range->start >> sb->s_blocksize_bits;
>>> + start = start / sbi->sec_per_clus;
>>
>> start is round-down, I think it's strange interface. E.g. user specified
>> the range as "start=10 len=1024". So the range should be 10-1034,
>> i.e. (assume cluster-size is 512) 512-1024, right?
>
> I don't know what's the correct way? If you're right. it's better to round-up.
> If cluster-size is 32KiB and start sector is in the middle of cluster,
> then which is better. round-down or round-up?
It depends on the design of this interface though, I bet it's round-up,
and should use same way with other FSes.
>>> + minlen = range->minlen >> sb->s_blocksize_bits;
>>> + minlen = minlen / sbi->sec_per_clus;
>>> + trimmed = 0;
>>> + count = 0;
>>> + err = -EINVAL;
>>> +
>>> + lock_fat(sbi);
>>> + if (sbi->free_clusters != -1 && sbi->free_clus_valid)
>>> + goto out;
>>
>> free clusters count validation doesn't matter here. If you want to check
>> free cluster count, you should check free_clusters==0 or not (after
>> validation).
>
> I borrowed it from "fat_count_free_clusters()". anyway fill fix it.
Yes. fat_count_free_clusters() needs to check free_clusters value,
because it updates free_clusters value. If it's uptodate, does nothing.
>>> + if (start < FAT_START_ENT)
>>> + start = FAT_START_ENT;
>>
>> Valid data cluster is 2 - max_cluster, but it should be mapped to 0 -
>> (max_cluster - FAT_START_ENT). Otherwise this interface's abstraction is
>> useless, right?
>
> user program don't know the filesystem internals. The same program is
> used for ext4 and fat. so it should be handled at filesystem.
Yes. It's what I'm saying. If user wants to trim 0-2 then user will
specify 0-2, but this trims only 2. It's not right.
>>> + fatent_set_entry(&fatent, start);
>>> +
>>> + while (count < sbi->max_cluster) {
>>> + if (fatent.entry >= sbi->max_cluster)
>>> + fatent.entry = FAT_START_ENT;
>>
>> Why do we cyclic this?
> If the start is middle and len is the whole disk size, then check the
> all clusters.
Strange design. If user wants to trim between middle and end, user have
to know length from middle correctly? Ext4 really does it?
Thanks.
--
OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
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