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Date: Mon, 21 Sep 2020 15:48:09 +0100
From: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH 02/11] mm: call import_iovec() instead of
 rw_copy_check_uvector() in process_vm_rw()
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References: <20200921143434.707844-1-hch@lst.de>
 <20200921143434.707844-3-hch@lst.de>
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To: Christoph Hellwig <hch@lst.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>, Andrew Morton <akpm@linux-foundation.org>, Jens Axboe <axboe@kernel.dk>, Arnd Bergmann <arnd@arndb.de>, David Howells <dhowells@redhat.com>, David Laight <David.Laight@aculab.com>, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, io-uring@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org

On Mon, Sep 21, 2020 at 04:34:25PM +0200, Christoph Hellwig wrote:
>  {
> -	WARN_ON(direction & ~(READ | WRITE));
> +	WARN_ON(direction & ~(READ | WRITE | CHECK_IOVEC_ONLY));

This is now a no-op because:

include/linux/fs.h:#define CHECK_IOVEC_ONLY -1

I'd suggest we renumber it to 2?

(READ is 0, WRITE is 1.  This WARN_ON should probably be
	WARN_ON(direction > CHECK_IOVEC_ONLY)