From patchwork Fri Nov 27 11:06:49 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 1407140 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=linux-ext4-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=suse.cz Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4CjBfZ2mTWz9s1l for ; Fri, 27 Nov 2020 22:07:18 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726171AbgK0LHC (ORCPT ); Fri, 27 Nov 2020 06:07:02 -0500 Received: from mx2.suse.de ([195.135.220.15]:43726 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725865AbgK0LHB (ORCPT ); Fri, 27 Nov 2020 06:07:01 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id D44D4AF37; Fri, 27 Nov 2020 11:06:59 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 784BA1E1139; Fri, 27 Nov 2020 12:06:59 +0100 (CET) From: Jan Kara To: Ted Tso Cc: , Jan Kara , stable@vger.kernel.org, Tahsin Erdogan Subject: [PATCH] ext4: Fix deadlock with fs freezing and EA inodes Date: Fri, 27 Nov 2020 12:06:49 +0100 Message-Id: <20201127110649.24730-1-jack@suse.cz> X-Mailer: git-send-email 2.16.4 Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Xattr code using inodes with large xattr data can end up dropping last inode reference (and thus deleting the inode) from places like ext4_xattr_set_entry(). That function is called with transaction started and so ext4_evict_inode() can deadlock against fs freezing like: CPU1 CPU2 removexattr() freeze_super() vfs_removexattr() ext4_xattr_set() handle = ext4_journal_start() ... ext4_xattr_set_entry() iput(old_ea_inode) ext4_evict_inode(old_ea_inode) sb->s_writers.frozen = SB_FREEZE_FS; sb_wait_write(sb, SB_FREEZE_FS); ext4_freeze() jbd2_journal_lock_updates() -> blocks waiting for all handles to stop sb_start_intwrite() -> blocks as sb is already in SB_FREEZE_FS state Generally it is advisable to delete inodes from a separate transaction as it can consume quite some credits however in this case it would be quite clumsy and furthermore the credits for inode deletion are quite limited and already accounted for. So just tweak ext4_evict_inode() to avoid freeze protection if we have transaction already started and thus it is not really needed anyway. CC: stable@vger.kernel.org Fixes: dec214d00e0d ("ext4: xattr inode deduplication") CC: Tahsin Erdogan Signed-off-by: Jan Kara Reviewed-by: Andreas Dilger --- fs/ext4/inode.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 72534319fae5..777eb08b29cd 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -175,6 +175,7 @@ void ext4_evict_inode(struct inode *inode) */ int extra_credits = 6; struct ext4_xattr_inode_array *ea_inode_array = NULL; + bool freeze_protected = false; trace_ext4_evict_inode(inode); @@ -232,9 +233,14 @@ void ext4_evict_inode(struct inode *inode) /* * Protect us against freezing - iput() caller didn't have to have any - * protection against it + * protection against it. When we are in a running transaction though, + * we are already protected against freezing and we cannot grab further + * protection due to lock ordering constraints. */ - sb_start_intwrite(inode->i_sb); + if (!ext4_journal_current_handle()) { + sb_start_intwrite(inode->i_sb); + freeze_protected = true; + } if (!IS_NOQUOTA(inode)) extra_credits += EXT4_MAXQUOTAS_DEL_BLOCKS(inode->i_sb); @@ -253,7 +259,8 @@ void ext4_evict_inode(struct inode *inode) * cleaned up. */ ext4_orphan_del(NULL, inode); - sb_end_intwrite(inode->i_sb); + if (freeze_protected) + sb_end_intwrite(inode->i_sb); goto no_delete; } @@ -294,7 +301,8 @@ void ext4_evict_inode(struct inode *inode) stop_handle: ext4_journal_stop(handle); ext4_orphan_del(NULL, inode); - sb_end_intwrite(inode->i_sb); + if (freeze_protected) + sb_end_intwrite(inode->i_sb); ext4_xattr_inode_array_free(ea_inode_array); goto no_delete; } @@ -323,7 +331,8 @@ void ext4_evict_inode(struct inode *inode) else ext4_free_inode(handle, inode); ext4_journal_stop(handle); - sb_end_intwrite(inode->i_sb); + if (freeze_protected) + sb_end_intwrite(inode->i_sb); ext4_xattr_inode_array_free(ea_inode_array); return; no_delete: