From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Sandeen Subject: [PATCH V2] ext4: avoid deadlock on sync-mounted FS w/o journal Date: Thu, 16 Feb 2012 15:41:45 -0800 Message-ID: <4F3D9439.3050908@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Martin.Wilck@ts.fujitsu.com To: ext4 development Return-path: Received: from mx1.redhat.com ([209.132.183.28]:15077 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755161Ab2BPXlv (ORCPT ); Thu, 16 Feb 2012 18:41:51 -0500 Sender: linux-ext4-owner@vger.kernel.org List-ID: From: Martin.Wilck@ts.fujitsu.com Processes hang forever on a sync-mounted ext2 file system that is mounted with the ext4 module (default in Fedora 16). I can reproduce this reliably by mounting an ext2 partition with "-o sync" and opening a new file an that partition with vim. vim will hang in "D" state forever. The same happens on ext4 without a journal. I am attaching a small patch here that solves this issue for me. In the sync mounted case without a journal, ext4_handle_dirty_metadata() may call sync_dirty_buffer(), which can't be called with buffer lock held. Also move mb_cache_entry_release inside lock to avoid race fixed previously by 8a2bfdcb ext[34]: EA block reference count racing fix Nonte too that ext2 fixed this same problem in 2006 with b2f49033 [PATCH] fix deadlock in ext2 Signed-off-by: Martin.Wilck@ts.fujitsu.com [sandeen@redhat.com: move mb_cache_entry_release before unlock, edit commit msg] Signed-off-by: Eric Sandeen --- diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c index 93a00d8..4410ae7 100644 --- a/fs/ext4/xattr.c +++ b/fs/ext4/xattr.c @@ -487,18 +487,19 @@ ext4_xattr_release_block(handle_t *handle, struct inode *inode, ext4_free_blocks(handle, inode, bh, 0, 1, EXT4_FREE_BLOCKS_METADATA | EXT4_FREE_BLOCKS_FORGET); + unlock_buffer(bh); } else { le32_add_cpu(&BHDR(bh)->h_refcount, -1); + if (ce) + mb_cache_entry_release(ce); + unlock_buffer(bh); error = ext4_handle_dirty_metadata(handle, inode, bh); if (IS_SYNC(inode)) ext4_handle_sync(handle); dquot_free_block(inode, 1); ea_bdebug(bh, "refcount now=%d; releasing", le32_to_cpu(BHDR(bh)->h_refcount)); - if (ce) - mb_cache_entry_release(ce); } - unlock_buffer(bh); out: ext4_std_error(inode->i_sb, error); return;