From 1f67d62f6f3567437388e5cc190c65578df96e88 Mon Sep 17 00:00:00 2001
From: Ross Zwisler <ross.zwisler@linux.intel.com>
Date: Thu, 12 Oct 2017 11:54:08 -0400
Subject: [PATCH] ext4: prevent data corruption with journaling + DAX
Git-commit: e9072d859df3e0f2c3ba450f0d1739595c2d5d13
Patch-mainline: v4.15-rc1
References: bsc#1064591
The current code has the potential for data corruption when changing an
inode's journaling mode, as that can result in a subsequent unsafe change
in S_DAX.
I've captured an instance of this data corruption in the following fstest:
https://patchwork.kernel.org/patch/9948377/
Prevent this data corruption from happening by disallowing changes to the
journaling mode if the '-o dax' mount option was used. This means that for
a given filesystem we could have a mix of inodes using either DAX or
data journaling, but whatever state the inodes are in will be held for the
duration of the mount.
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Jan Kara <jack@suse.cz>
---
fs/ext4/inode.c | 5 -----
fs/ext4/ioctl.c | 16 +++++++++++++---
2 files changed, 13 insertions(+), 8 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index edfe95f81274..350e0910ed32 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -6004,11 +6004,6 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val)
ext4_clear_inode_flag(inode, EXT4_INODE_JOURNAL_DATA);
}
ext4_set_aops(inode);
- /*
- * Update inode->i_flags after EXT4_INODE_JOURNAL_DATA was updated.
- * E.g. S_DAX may get cleared / set.
- */
- ext4_set_inode_flags(inode);
jbd2_journal_unlock_updates(journal);
percpu_up_write(&sbi->s_journal_flag_rwsem);
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index afb66d4ab5cf..b0b754b37c36 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -290,10 +290,20 @@ static int ext4_ioctl_setflags(struct inode *inode,
if (err)
goto flags_out;
- if ((jflag ^ oldflags) & (EXT4_JOURNAL_DATA_FL))
+ if ((jflag ^ oldflags) & (EXT4_JOURNAL_DATA_FL)) {
+ /*
+ * Changes to the journaling mode can cause unsafe changes to
+ * S_DAX if we are using the DAX mount option.
+ */
+ if (test_opt(inode->i_sb, DAX)) {
+ err = -EBUSY;
+ goto flags_out;
+ }
+
err = ext4_change_inode_journal_flag(inode, jflag);
- if (err)
- goto flags_out;
+ if (err)
+ goto flags_out;
+ }
if (migrate) {
if (flags & EXT4_EXTENTS_FL)
err = ext4_ext_migrate(inode);
--
2.12.3