From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from userp2120.oracle.com ([156.151.31.85]:54732 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725832AbfHPCOF (ORCPT ); Thu, 15 Aug 2019 22:14:05 -0400 Date: Thu, 15 Aug 2019 19:13:27 -0700 From: "Darrick J. Wong" Subject: Re: [PATCH RFC 3/2] fstests: check that we can't write to swap files Message-ID: <20190816021327.GD15198@magnolia> References: <156588514105.111054.13645634739408399209.stgit@magnolia> <20190815163434.GA15186@magnolia> <20190815142603.de9f1c0d9fcc017f3237708d@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190815142603.de9f1c0d9fcc017f3237708d@linux-foundation.org> Sender: fstests-owner@vger.kernel.org To: Andrew Morton Cc: hch@infradead.org, tytso@mit.edu, viro@zeniv.linux.org.uk, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, fstests List-ID: On Thu, Aug 15, 2019 at 02:26:03PM -0700, Andrew Morton wrote: > On Thu, 15 Aug 2019 09:34:34 -0700 "Darrick J. Wong" wrote: > > > While active, the media backing a swap file is leased to the kernel. > > Userspace has no business writing to it. Make sure we can't do this. > > I don't think this tests the case where a file was already open for > writing and someone does swapon(that file)? > > And then does swapoff(that file), when writes should start working again? > > Ditto all the above, with s/open/mmap/. Heh, ok. I'll start working on a C program to do that. > Do we handle (and test!) the case where there's unwritten dirty > pagecache at the time of swapon()? Ditto pte-dirty MAP_SHARED pages? One of the tests I wrote for iomap_swapfile_activate way back when checks that. The iomap version calls vfs_fsync, but AFAICT generic_swapfile_activate doesn't do that. --D