Re: [PATCH v2] loop: use vfs_getattr_nosec() for accurate file size

Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> · Tue, 12 Aug 2025 17:34:57 +0800

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

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