From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bombadil.infradead.org ([198.137.202.133]:49494 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726426AbeIEB3f (ORCPT ); Tue, 4 Sep 2018 21:29:35 -0400 Date: Tue, 4 Sep 2018 14:02:37 -0700 From: Matthew Wilcox To: Vito Caputo Cc: Jeff Layton , "J. Bruce Fields" , Rogier Wolff , =?utf-8?B?54Sm5pmT5Yas?= , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: POSIX violation by writeback error Message-ID: <20180904210237.GA12303@bombadil.infradead.org> References: <20180904075347.GH11854@BitWizard.nl> <82ffc434137c2ca47a8edefbe7007f5cbecd1cca.camel@redhat.com> <20180904161203.GD17478@fieldses.org> <20180904162348.GN17123@BitWizard.nl> <20180904185411.GA22166@fieldses.org> <20180904203534.yumaest6v5p6izln@shells.gnugeneration.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180904203534.yumaest6v5p6izln@shells.gnugeneration.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, Sep 04, 2018 at 01:35:34PM -0700, Vito Caputo wrote: > Implement a new class of swap space for backing dirty pages which fail > to write back. Pages in this space survive reboots, essentially backing > the implicit commitment POSIX establishes in the face of asynchronous > writeback errors. Rather than evicting these pages as clean, they are > swapped out to the persistent swap. You not only need to track which index within a file this swapped page belongs to but also which file. And that starts to get tricky. It may or may not have a name; it may or may not have a persistent inode number; it may or may not have a persistent fhandle. If it's on network storage, it may have been modified by another machine. If it's on removable storage, it may have been modified by another machine.