From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:45014 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726991AbeHFGOG (ORCPT ); Mon, 6 Aug 2018 02:14:06 -0400 Subject: Re: [PATCH V2] mkfs: avoid divide-by-zero when hardware reports optimal i/o size as 0 References: <20180805222044.GJ2234@dastard> From: Eric Sandeen Message-ID: Date: Sun, 5 Aug 2018 23:06:57 -0500 MIME-Version: 1.0 In-Reply-To: <20180805222044.GJ2234@dastard> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Dave Chinner Cc: linux-xfs , Jeff Mahoney On 8/5/18 5:20 PM, Dave Chinner wrote: > On Wed, Aug 01, 2018 at 03:49:45PM -0500, Eric Sandeen wrote: >> From: Jeff Mahoney >> >> Commit 051b4e37f5e (mkfs: factor AG alignment) factored out the >> AG alignment code into a separate function. It got rid of >> redundant checks for dswidth != 0 since calc_stripe_factors was >> supposed to guarantee that if dsunit is non-zero dswidth will be >> as well. Unfortunately, there's hardware out there that reports its >> optimal i/o size as larger than the maximum i/o size, which the kernel >> treats as broken and zeros out the optimal i/o size. >> >> To resolve this we can check the topology before consuming it, and >> ignore the bad stripe geometry. >> >> [sandeen: remove guessing heuristic, just warn and ignore bad data.] >> >> Fixes: 051b4e37f5e (mkfs: factor AG alignment) >> Signed-off-by: Jeff Mahoney >> Reviewed-by: Eric Sandeen >> Signed-off-by: Eric Sandeen >> --- >> >> so, I rewrote this a bit. I'm not a fan of guessing what the kernel >> really must have meant, becaue next time the root cause may be differnt. >> In other cases we ignore bad geometry, I think we should in this case as >> well. This will also let me go forward with a factored-out geometry checker, >> and for user-specified badness we'll warn and exit, for kernel-provided >> badness we'll warn and ignore. >> >> diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c >> index 1074886..2e53c1e 100644 >> --- a/mkfs/xfs_mkfs.c >> +++ b/mkfs/xfs_mkfs.c >> @@ -2281,11 +2281,20 @@ _("data stripe width (%d) must be a multiple of the data stripe unit (%d)\n"), >> >> /* if no stripe config set, use the device default */ >> if (!dsunit) { >> - dsunit = ft->dsunit; >> - dswidth = ft->dswidth; >> - use_dev = true; >> + /* Ignore nonsense from device. XXX add more validation */ >> + if (ft->dsunit && ft->dswidth == 0) { >> + fprintf(stderr, >> +_("%s: Volume reports stripe unit of %d bytes and stripe width of 0, ignoring.\n"), >> + progname, BBTOB(ft->dsunit)); >> + ft->dsunit = 0; >> + ft->dswidth = 0; > > Not sure this is the right thing to do. If a stripe unit has been > given, then the device has an alignment requirement. If it hasn't > given an "optimal IO size", then shouldn't we just set ft->dswidth = > ft->dsunit to retain the alignment the device requested? Yeah, I'm on the fence about that. If it's giving us inconsistent information, how can we know what's right and wrong? -Eric