ext4_should_writeback_data() had an incorrect sequence of
tests to determine if it should return 0 or 1: in
particular, even in no-journal mode, 0 was being returned
for a non-regular-file inode.
This meant that, in non-journal mode, we would use
ext4_journalled_aops for directories, symlinks, and other
non-regular files. However, calling journalled aop
callbacks when there is no valid handle, can cause problems.
This would cause a kernel crash with Jan Kara's commit
2d859db3e4 ("ext4: fix data corruption in inodes with
journalled data"), because we now dereference 'handle' in
ext4_journalled_write_end().
I also added BUG_ONs to check for a valid handle in the
obviously journal-only aops callbacks.
I tested this running xfstests with a scratch device in
these modes:
- no-journal
- data=ordered
- data=writeback
- data=journal
All work fine; the data=journal run has many failures and a
crash in xfstests 074, but this is no different from a
vanilla kernel.
Signed-off-by: Curt Wohlgemuth <curtw@xxxxxxxxxx>
---
fs/ext4/ext4_jbd2.h | 4 ++--
fs/ext4/inode.c | 4 ++++
2 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
index bb85757..5802fa1 100644
--- a/fs/ext4/ext4_jbd2.h
+++ b/fs/ext4/ext4_jbd2.h
@@ -289,10 +289,10 @@ static inline int ext4_should_order_data(struct inode *inode)
static inline int ext4_should_writeback_data(struct inode *inode)
{
- if (!S_ISREG(inode->i_mode))
- return 0;
if (EXT4_JOURNAL(inode) == NULL)
return 1;
+ if (!S_ISREG(inode->i_mode))
+ return 0;
if (ext4_test_inode_flag(inode, EXT4_INODE_JOURNAL_DATA))
return 0;
if (test_opt(inode->i_sb, DATA_FLAGS) == EXT4_MOUNT_WRITEBACK_DATA)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index d47264c..ad3a7ca 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -983,6 +983,8 @@ static int ext4_journalled_write_end(struct file *file,
from = pos & (PAGE_CACHE_SIZE - 1);
to = from + len;
+ BUG_ON(!ext4_handle_valid(handle));
+
if (copied < len) {
if (!PageUptodate(page))
copied = 0;
@@ -1699,6 +1701,8 @@ static int __ext4_journalled_writepage(struct page *page,
goto out;
}
+ BUG_ON(!ext4_handle_valid(handle));
+
ret = walk_page_buffers(handle, page_bufs, 0, len, NULL,
do_journal_get_write_access);
--
1.7.3.1
--
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