linux-kernel - Re: [PATCH v2] loop: use vfs_getattr

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Message-ID: <e2a5550d-fb55-99c1-82b1-5b6c174f7cfc@huaweicloud.com>
Date: Tue, 12 Aug 2025 17:34:57 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Christoph Hellwig <hch@...radead.org>, Damien Le Moal <dlemoal@...nel.org>
Cc: Al Viro <viro@...iv.linux.org.uk>, Rajeev Mishra <rajeevm@....com>,
 axboe@...nel.dk, yukuai1@...weicloud.com, linux-block@...r.kernel.org,
 linux-kernel@...r.kernel.org, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH v2] loop: use vfs_getattr_nosec() for accurate file size

Hi,

在 2025/08/12 16:37, Christoph Hellwig 写道:
> On Tue, Aug 12, 2025 at 02:17:01PM +0900, Damien Le Moal wrote:
>> And indeed, that:
>>
>> 	/* size of the new backing store needs to be the same */
>>          if (get_loop_size(lo, file) != get_loop_size(lo, old_file))
>>                  goto out_err;
>>
>> Will need some massaging.
> 
> Why?  get_loop_size just derives the first arguments to get_size
> from the passed in loop device in the same way the only other caller
> to get_size does.  So we can just:
> 
>    1) convert loop_set_status to use get_loop_size
>    2) Fold get_size into get_loop_size
>    3) Maye rename get_size to lo_calculate_size to have a descriptive
>       name while we're touching it?
>    4) switch to vfs_getattr

This looks good, it's better to refactor a bit before switch to getattr,
and I agree still return 0 on failue is fine.

Thanks,
Kuai

> 
> 
> .
>