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	Mon, 25 Aug 2025 09:18:09 +0000
Date: Mon, 25 Aug 2025 02:18:09 -0700
From: Christoph Hellwig <hch@infradead.org>
To: Ming Lei <ming.lei@redhat.com>
Cc: Yu Kuai <yukuai1@huaweicloud.com>, axboe@kernel.dk, rajeevm@hpe.com,
	yukuai3@huawei.com, linux-block@vger.kernel.org,
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	yangerkun@huawei.com, johnny.chenyi@huawei.com,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] loop: fix zero sized loop for block special file
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References: <20250825062300.2485281-1-yukuai1@huaweicloud.com>
 <aKwlVypJuBtPH_EL@fedora>
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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.

> 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;
> 	}
> 
> 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.