From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:47736 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727806AbeLFKrv (ORCPT ); Thu, 6 Dec 2018 05:47:51 -0500 Date: Thu, 6 Dec 2018 11:47:48 +0100 From: Greg KH To: Nikolay Borisov Cc: stable@vger.kernel.org, dsterba@suse.com, wqu@suse.com Subject: Re: [PATCH] btrfs: Always try all copies when reading extent buffers Message-ID: <20181206104748.GE19891@kroah.com> References: <154383135818461@kroah.com> <20181204124903.31280-1-nborisov@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181204124903.31280-1-nborisov@suse.com> Sender: stable-owner@vger.kernel.org List-ID: On Tue, Dec 04, 2018 at 02:49:03PM +0200, Nikolay Borisov wrote: > When a metadata read is served the endio routine btree_readpage_end_io_hook > is called which eventually runs the tree-checker. If tree-checker fails > to validate the read eb then it sets EXTENT_BUFFER_CORRUPT flag. This > leads to btree_read_extent_buffer_pages wrongly assuming that all > available copies of this extent buffer are wrong and failing prematurely. > Fix this modify btree_read_extent_buffer_pages to read all copies of > the data. > > This failure was exhibitted in xfstests btrfs/124 which would > spuriously fail its balance operations. The reason was that when balance > was run following re-introduction of the missing raid1 disk > __btrfs_map_block would map the read request to stripe 0, which > corresponded to devid 2 (the disk which is being removed in the test): > > item 2 key (FIRST_CHUNK_TREE CHUNK_ITEM 3553624064) itemoff 15975 itemsize 112 > length 1073741824 owner 2 stripe_len 65536 type DATA|RAID1 > io_align 65536 io_width 65536 sector_size 4096 > num_stripes 2 sub_stripes 1 > stripe 0 devid 2 offset 2156920832 > dev_uuid 8466c350-ed0c-4c3b-b17d-6379b445d5c8 > stripe 1 devid 1 offset 3553624064 > dev_uuid 1265d8db-5596-477e-af03-df08eb38d2ca > > This caused read requests for a checksum item that to be routed to the > stale disk which triggered the aforementioned logic involving > EXTENT_BUFFER_CORRUPT flag. This then triggered cascading failures of > the balance operation. > > Fixes: a826d6dcb32d ("Btrfs: check items for correctness as we search") > CC: stable@vger.kernel.org # 4.4+ > Suggested-by: Qu Wenruo > Reviewed-by: Qu Wenruo > Signed-off-by: Nikolay Borisov > Signed-off-by: David Sterba > --- > Hi Greg, > > Please apply this backport of upstream commit f8397d69daef06d358430d3054662fb597e37c00 > to 4.4.y Now applied, thanks. greg k-h