From patchwork Fri Sep 28 15:44:07 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [07/11] ext4: serialize unlocked dio reads with truncate Date: Fri, 28 Sep 2012 05:44:07 -0000 From: Dmitri Monakho X-Patchwork-Id: 187815 Message-Id: <1348847051-6746-8-git-send-email-dmonakhov@openvz.org> To: linux-ext4@vger.kernel.org Cc: tytso@mit.edu, jack@suse.cz, lczerner@redhat.com, Dmitry Monakhov 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) if i_size about to be reduced 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 | 7 +++++-- 1 files changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index da52855..583cb3f 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -4255,7 +4255,6 @@ 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); @@ -4304,8 +4303,12 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr) } if (attr->ia_valid & ATTR_SIZE) { - if (attr->ia_size != i_size_read(inode)) + if (attr->ia_size != inode->i_size) { truncate_setsize(inode, attr->ia_size); + /* Inode size will be reduced, wait for dio in flight */ + if (orphan) + inode_dio_wait(inode); + } ext4_truncate(inode); }