From 4c4679fc02744ec3955e88faf5e8b6844fa8cbd3 Mon Sep 17 00:00:00 2001
From: Dmitry Monakhov <dmonakhov@openvz.org>
Date: Sat, 29 Sep 2012 00:55:23 -0400
Subject: [PATCH 06/13] ext4: serialize unlocked dio reads with truncate
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 <jack@suse.cz>
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
(cherry picked from commit 1c9114f9c0f10f58dd7e568a7152025af47b27e5)
---
fs/ext4/inode.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 2bd7526..b84322d 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4277,7 +4277,6 @@ 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);
@@ -4326,8 +4325,12 @@ 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 != i_size_read(inode)) {
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);
}
--
1.7.12.rc0.22.gcdd159b