From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from renko.ucs.ed.ac.uk (renko.ucs.ed.ac.uk [129.215.13.3]) by kvack.org (8.8.7/8.8.7) with ESMTP id UAA17561 for ; Thu, 23 Apr 1998 20:18:21 -0400 Date: Thu, 23 Apr 1998 23:01:32 +0100 Message-Id: <199804232201.XAA02883@dax.dcs.ed.ac.uk> From: "Stephen C. Tweedie" MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Subject: Re: filemap_nopage is broken!! In-Reply-To: References: Sender: owner-linux-mm@kvack.org To: "Eric W. Biederman" Cc: linux-mm@kvack.org List-ID: Hi, On 22 Apr 1998 15:51:07 -0500, ebiederm+eric@npwt.net (Eric W. Biederman) said: > Now if the following sequence of actions occure. > a) A page is mapped privately with poor alignment. > b) That part of the file is written again. > c) The page is again mapped privately with poor alignment. > When the page cache page is not scavenged between a and c, the same > data is read, despite the fact it has changed on disk, and in the > aligned page cache page! > That is broken behavior. I don't think this is necessarily a problem. The kernel simply does not guarantee full correspondance semantics between filesystem updates and the page cache for non-aligned pages, but then again, it is not required to --- it is not even required to support such mmaps, so I can live with an undefined behaviour in this case! --Stephen