linux-kernel - Re: [PATCH v2] ext4: fix hole punch failure when depth is greater than 0

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Date:	Mon, 9 Jul 2012 23:07:42 +0530
From:	Ashish Sangwan <ashishsangwan2@...il.com>
To:	Lukáš Czerner <lczerner@...hat.com>
Cc:	sandeen@...hat.com, Ted Tso <tytso@....edu>,
	linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org,
	Namjae Jeon <linkinjeon@...il.com>
Subject: Re: [PATCH v2] ext4: fix hole punch failure when depth is greater
 than 0

> Ok, the code is not very clear, but now I can see it. p_block is
> actually misused here to store the number of indexes in the current
> node while diving into the tree. Then on the way up, we are checking
> that to see if the eh_entries changed or not (which is indicating
> that something has been freed deeper in the tree).
True, p_block is misused. We tried to fix the problem with
minimum code change.
>
> That said, it makes sense to set it before the loop itself because
> we are actually skipping the path construction while diving into
> the tree since patch is already initialized and we're starting
> walking back from 'depth' up in this case. So the patch seems fine.
> Thanks for catching it and fixing it.
>
> You can add
>
> Reviewed-by: Lukas Czerner <lczerner@...hat.com>
>
Thanks for your review.
>
>> >
>> > Note: there are some indent problems in your patch, like for example
>> > this:
>> >
>> > +                       path[k].p_block =
>> > +                       le16_to_cpu(path[k].p_hdr->eh_entries)+1;
>> >
>> >
>> Before submitting the patch, I run checkpatch.pl with --strict option.
>> It did'nt show any error or warning. Should I re-submit
>> the patch with an extra tab before the second line? The call is yours.
>
> checkpatch.pl does not catch everything. Just look at how wrapping
> of long lines is done in the code, there are plenty of examples.
>
True again. I will resend patch with proper indentation.
>>
>> > Anyway, what do you think about the modification ?
>> >
>> Also there is 1 modification missing from your patch.
>>     ext4_ext_drop_refs(path);
>>         kfree(path);
>> +       path = NULL;
>>         if (err == -EAGAIN)
>>                 goto again;
>> If path is not set to NULL, it will crash in xfstest #13. Ted has
>> already reported it.
>
> Right, I've probably used the old patch as an example.
>
> Thanks!
> -Lukas
>
Thanks,
Ashish
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