Return-Path: Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:50354 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755905AbaCTBCJ (ORCPT ); Wed, 19 Mar 2014 21:02:09 -0400 From: Chris Mason To: Marc MERLIN CC: "linux-btrfs@vger.kernel.org" Subject: Re: btrfs-rmw-2: page allocation failure: order:1, mode:0x8020 Date: Thu, 20 Mar 2014 01:01:35 +0000 Message-ID: In-Reply-To: <20140320002007.GY18959@merlins.org> Content-Type: text/plain; charset="euc-kr" MIME-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 3/19/14, 8:20 PM, "Marc MERLIN" wrote: >On Thu, Mar 20, 2014 at 12:13:36AM +0000, Chris Mason wrote: >> >Should I double it? >> > >> >For now, I have the copy running again, and it's been going for 8 hours >> >without failure on the old kernel but of course that doesn't mean my >>2TB >> >copy will complete without hitting the bug again. >> >> Sorry, I misspoke, you should bump /proc/sys/vm/min_free_kbytes. >>Honestly >> though, its just a bug in the mvs driver. Atomic 8K allocations are >> doomed to fail eventually. > >Gotcha >polgara:/mnt/btrfs_backupcopy# cat /proc/sys/vm/min_free_kbytes >45056 >polgara:/mnt/btrfs_backupcopy# echo 100000 > /proc/sys/vm/min_free_kbytes >polgara:/mnt/btrfs_backupcopy# cat /proc/sys/vm/min_free_kbytes >100000 >polgara:/mnt/btrfs_backupcopy# > >> The driver should either busy loop until the allocation completes >>(really >> not a great choice), gracefully deal with the failure (looks tricky), or >> preallocate the space (like the rest of the block layer). > >Gotcha. I'll report this to the folks maintaining the marvel driver. > >So just to make sure I got you right, although the page allocation failure >was shown in btrfs, it's really the underlying marvel driver at fault >here, >and there isn't really anything to change on the btrfs side, correct? The process is a btrfs worker, and the IO was started by btrfs, but the allocation failure is all inside the mvs driver. Theres even the printk in there from mvs about the allocation failing. The only reason its btrfs instead of a regular process is because for raid5/6 the rmw is farmed out to helper threads. -chris {.n++%ݶw{.n+{k~^nrzh&zzޗ++zfh~iz_j:+v)ߣm