linux-kernel - Re: [PATCH 3/6] block: open code __generic_file_write

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Message-ID: <20230829020614.GB325446@ZenIV>
Date:   Tue, 29 Aug 2023 03:06:14 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Christoph Hellwig <hch@....de>
Cc:     Jens Axboe <axboe@...nel.dk>,
        "Darrick J. Wong" <djwong@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Christian Brauner <christian@...uner.io>,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] block: open code __generic_file_write_iter for
 blkdev writes

On Tue, Aug 01, 2023 at 07:21:58PM +0200, Christoph Hellwig wrote:
> @@ -569,7 +594,23 @@ static ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  		iov_iter_truncate(from, size);
>  	}
>  
> -	ret = __generic_file_write_iter(iocb, from);
> +	ret = file_remove_privs(file);
> +	if (ret)
> +		return ret;

That chunk is a bit of a WTF generator...  Thankfully,

static int __file_remove_privs(struct file *file, unsigned int flags)
{
        struct dentry *dentry = file_dentry(file);
	struct inode *inode = file_inode(file);
	int error = 0;
	int kill;

	if (IS_NOSEC(inode) || !S_ISREG(inode->i_mode))
		return 0;

means that it's really a no-op.  But I'd still suggest
removing it, just to reduce the amount of head-scratching
for people who'll be reading that code later...