From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:49534 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755665AbdERKxI (ORCPT ); Thu, 18 May 2017 06:53:08 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jan Kara , Ross Zwisler , Dan Williams , Andrew Morton , Linus Torvalds Subject: [PATCH 4.11 084/114] ext4: return to starting transaction in ext4_dax_huge_fault() Date: Thu, 18 May 2017 12:46:34 +0200 Message-Id: <20170518103617.436700864@linuxfoundation.org> In-Reply-To: <20170518103604.736737251@linuxfoundation.org> References: <20170518103604.736737251@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.11-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jan Kara commit fb26a1cbed8c90025572d48bc9eabe59f7571e88 upstream. DAX will return to locking exceptional entry before mapping blocks for a page fault to fix possible races with concurrent writes. To avoid lock inversion between exceptional entry lock and transaction start, start the transaction already in ext4_dax_huge_fault(). Fixes: 9f141d6ef6258a3a37a045842d9ba7e68f368956 Link: http://lkml.kernel.org/r/20170510085419.27601-4-jack@suse.cz Signed-off-by: Jan Kara Cc: Ross Zwisler Cc: Dan Williams Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/ext4/file.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -257,6 +257,7 @@ static int ext4_dax_huge_fault(struct vm enum page_entry_size pe_size) { int result; + handle_t *handle = NULL; struct inode *inode = file_inode(vmf->vma->vm_file); struct super_block *sb = inode->i_sb; bool write = vmf->flags & FAULT_FLAG_WRITE; @@ -264,12 +265,24 @@ static int ext4_dax_huge_fault(struct vm if (write) { sb_start_pagefault(sb); file_update_time(vmf->vma->vm_file); + down_read(&EXT4_I(inode)->i_mmap_sem); + handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE, + EXT4_DATA_TRANS_BLOCKS(sb)); + } else { + down_read(&EXT4_I(inode)->i_mmap_sem); } - down_read(&EXT4_I(inode)->i_mmap_sem); - result = dax_iomap_fault(vmf, pe_size, &ext4_iomap_ops); - up_read(&EXT4_I(inode)->i_mmap_sem); - if (write) + if (!IS_ERR(handle)) + result = dax_iomap_fault(vmf, pe_size, &ext4_iomap_ops); + else + result = VM_FAULT_SIGBUS; + if (write) { + if (!IS_ERR(handle)) + ext4_journal_stop(handle); + up_read(&EXT4_I(inode)->i_mmap_sem); sb_end_pagefault(sb); + } else { + up_read(&EXT4_I(inode)->i_mmap_sem); + } return result; }