On 4/1/25 3:33 PM, Eric Sandeen wrote:
> On 3/31/25 3:31 AM, Chao Yu wrote:
>> On 3/29/25 12:18, Eric Sandeen wrote:
>>> I was working on next steps for this, and I have a followup question.
>>>
>>> Today, several mount options are simply ignored if the on-disk format
>>> does not support them. For example:
>>>
>>> case Opt_compress_mode:
>>> if (!f2fs_sb_has_compression(sbi)) {
>>> f2fs_info(sbi, "Image doesn't support
>>> compression");
>>> break;
>>> }
>>> name = match_strdup(&args[0]);
>>> if (!name)
>>> return -ENOMEM;
>>> if (!strcmp(name, "fs")) {
>>> F2FS_OPTION(sbi).compress_mode =
>>> COMPR_MODE_FS;
>>> } else if (!strcmp(name, "user")) {
>>> F2FS_OPTION(sbi).compress_mode =
>>> COMPR_MODE_USER;
>>> } else {
>>> kfree(name);
>>> return -EINVAL;
>>> }
>>> kfree(name);
>>> break;
>>>
>>> so if f2fs_sb_has_compression() is not true, then the option is ignored
>>> without
>>> any validation.
>>>
>>> in other words, "mount -o compress_mode=nope ..." will succeed if the
>>> feature
>>> is disabled on the filesystem.
>>>
>>> If I move the f2fs_sb_has_compression() check to later for the new mount
>>> API,
>>> then "mount -o compress_mode=nope ..." will start failing for all images.
>>> Is
>>> this acceptable? It seems wise to reject invalid options rather than ignore
>>> them,
>>> even if they are incompatible with the format, but this would be a behavior
>>> change.
>>
>> I'm fine w/ this change. IIRC, I haven't saw above use case, otherwise user
>> should stop passing invalid mount option to f2fs.
>
> Great, I will proceed with this. It will make the conversion simpler (but may
> make testing/validation more difficult, as behavior will change with invalid
> input).
FYI - I don't think I will be able to complete this conversion task myself -
f2fs is
by far the most difficult conversion I've encountered, and my time for these
sorts of
projects is sadly limited. I do have one more patch series that moves a lot of
the
on-disk feature checking out of option parsing, and perhaps I will send it as
an example
at least.
But I think it may be time to ask the f2fs experts to take over this effort,
because
I'm just not getting through it on my own.
(We are down to only a small handful of filesystems left - in fact, I think only
bfs, 9p, and f2fs, that don't have patches anywhere. So it would be really
great to
get some help on this.)
Thanks,
-Eric
> -Eric
>
>> Thanks,
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