Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933678AbcCGXry (ORCPT ); Mon, 7 Mar 2016 18:47:54 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:44077 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933615AbcCGXpj (ORCPT ); Mon, 7 Mar 2016 18:45:39 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Deng Chao , Ming Liu , wangzaiwei , Thomas Betker , David Woodhouse Subject: [PATCH 3.10 09/24] Revert "jffs2: Fix lock acquisition order bug in jffs2_write_begin" Date: Mon, 7 Mar 2016 15:45:11 -0800 Message-Id: <20160307234351.890685454@linuxfoundation.org> X-Mailer: git-send-email 2.7.2 In-Reply-To: <20160307234350.601613335@linuxfoundation.org> References: <20160307234350.601613335@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3954 Lines: 133 3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Betker commit 157078f64b8a9cd7011b6b900b2f2498df850748 upstream. This reverts commit 5ffd3412ae55 ("jffs2: Fix lock acquisition order bug in jffs2_write_begin"). The commit modified jffs2_write_begin() to remove a deadlock with jffs2_garbage_collect_live(), but this introduced new deadlocks found by multiple users. page_lock() actually has to be called before mutex_lock(&c->alloc_sem) or mutex_lock(&f->sem) because jffs2_write_end() and jffs2_readpage() are called with the page locked, and they acquire c->alloc_sem and f->sem, resp. In other words, the lock order in jffs2_write_begin() was correct, and it is the jffs2_garbage_collect_live() path that has to be changed. Revert the commit to get rid of the new deadlocks, and to clear the way for a better fix of the original deadlock. Reported-by: Deng Chao Reported-by: Ming Liu Reported-by: wangzaiwei Signed-off-by: Thomas Betker Signed-off-by: David Woodhouse Signed-off-by: Greg Kroah-Hartman --- fs/jffs2/file.c | 39 ++++++++++++++++++--------------------- 1 file changed, 18 insertions(+), 21 deletions(-) --- a/fs/jffs2/file.c +++ b/fs/jffs2/file.c @@ -138,39 +138,33 @@ static int jffs2_write_begin(struct file struct page *pg; struct inode *inode = mapping->host; struct jffs2_inode_info *f = JFFS2_INODE_INFO(inode); - struct jffs2_sb_info *c = JFFS2_SB_INFO(inode->i_sb); - struct jffs2_raw_inode ri; - uint32_t alloc_len = 0; pgoff_t index = pos >> PAGE_CACHE_SHIFT; uint32_t pageofs = index << PAGE_CACHE_SHIFT; int ret = 0; - jffs2_dbg(1, "%s()\n", __func__); - - if (pageofs > inode->i_size) { - ret = jffs2_reserve_space(c, sizeof(ri), &alloc_len, - ALLOC_NORMAL, JFFS2_SUMMARY_INODE_SIZE); - if (ret) - return ret; - } - - mutex_lock(&f->sem); pg = grab_cache_page_write_begin(mapping, index, flags); - if (!pg) { - if (alloc_len) - jffs2_complete_reservation(c); - mutex_unlock(&f->sem); + if (!pg) return -ENOMEM; - } *pagep = pg; - if (alloc_len) { + jffs2_dbg(1, "%s()\n", __func__); + + if (pageofs > inode->i_size) { /* Make new hole frag from old EOF to new page */ + struct jffs2_sb_info *c = JFFS2_SB_INFO(inode->i_sb); + struct jffs2_raw_inode ri; struct jffs2_full_dnode *fn; + uint32_t alloc_len; jffs2_dbg(1, "Writing new hole frag 0x%x-0x%x between current EOF and new page\n", (unsigned int)inode->i_size, pageofs); + ret = jffs2_reserve_space(c, sizeof(ri), &alloc_len, + ALLOC_NORMAL, JFFS2_SUMMARY_INODE_SIZE); + if (ret) + goto out_page; + + mutex_lock(&f->sem); memset(&ri, 0, sizeof(ri)); ri.magic = cpu_to_je16(JFFS2_MAGIC_BITMASK); @@ -197,6 +191,7 @@ static int jffs2_write_begin(struct file if (IS_ERR(fn)) { ret = PTR_ERR(fn); jffs2_complete_reservation(c); + mutex_unlock(&f->sem); goto out_page; } ret = jffs2_add_full_dnode_to_inode(c, f, fn); @@ -211,10 +206,12 @@ static int jffs2_write_begin(struct file jffs2_mark_node_obsolete(c, fn->raw); jffs2_free_full_dnode(fn); jffs2_complete_reservation(c); + mutex_unlock(&f->sem); goto out_page; } jffs2_complete_reservation(c); inode->i_size = pageofs; + mutex_unlock(&f->sem); } /* @@ -223,18 +220,18 @@ static int jffs2_write_begin(struct file * case of a short-copy. */ if (!PageUptodate(pg)) { + mutex_lock(&f->sem); ret = jffs2_do_readpage_nolock(inode, pg); + mutex_unlock(&f->sem); if (ret) goto out_page; } - mutex_unlock(&f->sem); jffs2_dbg(1, "end write_begin(). pg->flags %lx\n", pg->flags); return ret; out_page: unlock_page(pg); page_cache_release(pg); - mutex_unlock(&f->sem); return ret; }