From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Monakhov Subject: [PATCH 2/4] ext4: serialize unlocked dio reads with truncate Date: Tue, 4 Sep 2012 21:36:52 +0400 Message-ID: <1346780214-29845-2-git-send-email-dmonakhov@openvz.org> References: <1346780214-29845-1-git-send-email-dmonakhov@openvz.org> Cc: jack@suse.cz, Dmitry Monakhov To: linux-ext4@vger.kernel.org Return-path: Received: from mail-lb0-f174.google.com ([209.85.217.174]:32769 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757488Ab2IDRhA (ORCPT ); Tue, 4 Sep 2012 13:37:00 -0400 Received: by lbbgj3 with SMTP id gj3so3278491lbb.19 for ; Tue, 04 Sep 2012 10:36:59 -0700 (PDT) In-Reply-To: <1346780214-29845-1-git-send-email-dmonakhov@openvz.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: Current serialization will works only for DIO which holds i_mutex, but nonlocked DIO following race is possible: dio_nolock_read_task truncate_task ->ext4_setattr() ->inode_dio_wait() ->ext4_ext_direct_IO ->ext4_ind_direct_IO ->__blockdev_direct_IO ->ext4_get_block ->truncate_setsize() ->ext4_truncate() #alloc truncated blocks #to other inode ->submit_io() #INFORMATION LEAK In order to serialize with unlocked DIO reads we have to rearrange wait sequence 1) update i_size first 2) wait for outstanding DIO requests 3) and only after that truncate inode blocks Reviewed-by: Jan Kara Signed-off-by: Dmitry Monakhov --- fs/ext4/inode.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 58ef61a..709ec5a 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -4304,7 +4304,6 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr) } if (attr->ia_valid & ATTR_SIZE) { - inode_dio_wait(inode); if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) { struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); @@ -4355,6 +4354,7 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr) if (attr->ia_valid & ATTR_SIZE) { if (attr->ia_size != i_size_read(inode)) truncate_setsize(inode, attr->ia_size); + inode_dio_wait(inode); ext4_truncate(inode); } -- 1.7.7.6