linux-kernel - Re: [PATCH v2] loop: fix zero sized loop for block special file

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Message-ID: <CAFj5m9KTdHdQrrwBdUF=2xK9uDqnv6Zt6j7gLXRzr7CYy_cW+A@mail.gmail.com>
Date: Mon, 25 Aug 2025 19:26:58 +0800
From: Ming Lei <ming.lei@...hat.com>
To: Yu Kuai <yukuai1@...weicloud.com>
Cc: hch@...radead.org, axboe@...nel.dk, yukuai3@...wei.com, rajeevm@....com, 
	linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, 
	yi.zhang@...wei.com, yangerkun@...wei.com, johnny.chenyi@...wei.com
Subject: Re: [PATCH v2] loop: fix zero sized loop for block special file

On Mon, Aug 25, 2025 at 5:40 PM Yu Kuai <yukuai1@...weicloud.com> wrote:
>
> From: Yu Kuai <yukuai3@...wei.com>
>
> By default, /dev/sda is block specail file from devtmpfs, getattr will
> return file size as zero, causing loop failed for raw block device.
>
> We can add bdev_statx() to return device size, however this may introduce
> changes that are not acknowledged by user. Fix this problem by reverting
> changes for block special file, file mapping host is set to bdev inode
> while opening, and use i_size_read() directly to get device size.
>
> Fixes: 47b71abd5846 ("loop: use vfs_getattr_nosec for accurate file size")
> Reported-by: kernel test robot <oliver.sang@...el.com>
> Closes: https://lore.kernel.org/oe-lkp/202508200409.b2459c02-lkp@intel.com
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
> Changes in v2:
>  - don't call vfs_getattr_nosec() for block special file path, by Ming

Reviewed-by: Ming Lei <ming.lei@...hat.com>