Re: [PATCH] loop: fix zero sized loop for block special file

[Yu Kuai <yukuai1@xxxxxxxxxxxxxxx>]

Hi,

在 2025/08/25 17:18, Christoph Hellwig 写道:
> On Mon, Aug 25, 2025 at 04:56:55PM +0800, Ming Lei wrote:
> > `stat $BDEV_PATH` never works for getting bdev size, so it looks wrong
> > to call vfs_getattr_nosec() with bdev path for retrieving bdev's size.
>
> Exactly.

Ok.
> > So just wondering why not take the following more readable way?
> >
> > 	/* vfs_getattr() never works for retrieving bdev size */
> > 	if (S_ISBLK(stat.mode)) {
> > 		loopsize = i_size_read(file->f_mapping->host);
> > 	} else {
> >            ret = vfs_getattr_nosec(&file->f_path, &stat, STATX_SIZE, 0);
> >            if (ret)
> >                    return 0;
> >            loopsize = stat.size;
> > 	}

Just we can't use stat.mode here, I'll replace it with:

S_ISBLK(file_inode(file)->i_mode)

Thanks,
Kuai

> > Also the above looks like how application reads file size in case of bdev
> > involved.
>
> That's not just more readable, but simply the way to go.  Maybe split
> it into a helper for readability, though.
> .