From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f198.google.com (mail-wr0-f198.google.com [209.85.128.198]) by kanga.kvack.org (Postfix) with ESMTP id 8CD30280401 for ; Tue, 9 May 2017 08:18:58 -0400 (EDT) Received: by mail-wr0-f198.google.com with SMTP id g67so19452887wrd.0 for ; Tue, 09 May 2017 05:18:58 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id i201si34538wmd.25.2017.05.09.05.18.56 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 09 May 2017 05:18:57 -0700 (PDT) From: Jan Kara Subject: [PATCH 3/4] ext4: Return back to starting transaction in ext4_dax_huge_fault() Date: Tue, 9 May 2017 14:18:36 +0200 Message-Id: <20170509121837.26153-4-jack@suse.cz> In-Reply-To: <20170509121837.26153-1-jack@suse.cz> References: <20170509121837.26153-1-jack@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Ross Zwisler , Dan Williams , linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-nvdimm@lists.01.org, linux-mm@kvack.org, Jan Kara , stable@vger.kernel.org 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 CC: stable@vger.kernel.org Signed-off-by: Jan Kara --- fs/ext4/file.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) diff --git a/fs/ext4/file.c b/fs/ext4/file.c index cefa9835f275..831fd6beebf0 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -257,6 +257,7 @@ static int ext4_dax_huge_fault(struct vm_fault *vmf, 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_fault *vmf, 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; } -- 2.12.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org