From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:53632 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751646AbdKTRYr (ORCPT ); Mon, 20 Nov 2017 12:24:47 -0500 Date: Mon, 20 Nov 2017 18:22:51 +0100 From: David Sterba To: Josef Bacik Cc: linux-btrfs@vger.kernel.org, kernel-team@fb.com, Josef Bacik Subject: Re: [PATCH] btrfs: fix deadlock when writing out space cache Message-ID: <20171120172251.GC3553@twin.jikos.cz> Reply-To: dsterba@suse.cz References: <1510780852-8862-1-git-send-email-josef@toxicpanda.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1510780852-8862-1-git-send-email-josef@toxicpanda.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Wed, Nov 15, 2017 at 04:20:52PM -0500, Josef Bacik wrote: > From: Josef Bacik > > If we fail to prepare our pages for whatever reason (out of memory in > our case) we need to make sure to drop the block_group->data_rwsem, > otherwise hilarity ensues. > > Signed-off-by: Josef Bacik > --- > fs/btrfs/free-space-cache.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c > index cdc9f4015ec3..a6c643275210 100644 > --- a/fs/btrfs/free-space-cache.c > +++ b/fs/btrfs/free-space-cache.c > @@ -1263,8 +1263,12 @@ static int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode, > > /* Lock all pages first so we can lock the extent safely. */ > ret = io_ctl_prepare_pages(io_ctl, inode, 0); > - if (ret) > + if (ret) { > + if (block_group && > + (block_group->flags & BTRFS_BLOCK_GROUP_DATA)) > + up_write(&block_group->data_rwsem); > goto out; The unlocking sequence is in the exit block but does not have a label. It would be better to reuse the code.