i_disksize update should be protected by i_data_sem, by either taking
the lock explicitly or by using ext4_update_i_disksize() helper. But the
i_disksize updates in ext4_direct_IO_write() are not protected at all,
which may be racing with i_disksize updates in writeback path in
delalloc buffer write path.
This is found by code inspection, and I didn't hit any i_disksize
corruption due to this bug. Thanks to Jan Kara for catching this bug and
suggesting the fix!
Reported-by: Jan Kara <jack@xxxxxxx>
Suggested-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Eryu Guan <guaneryu@xxxxxxxxx>
---
There's no v1 version of this patch.
It's a bit unfortunate that I have to remove the "ei" definition in this
patch and reintroduce it in patch 2/2, otherwise I got transient
"defined but not used" build warning with only this patch applied.
fs/ext4/inode.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index c94780075b04..bff44b4a0783 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3658,7 +3658,6 @@ static ssize_t ext4_direct_IO_write(struct kiocb *iocb, struct iov_iter *iter)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
- struct ext4_inode_info *ei = EXT4_I(inode);
ssize_t ret;
loff_t offset = iocb->ki_pos;
size_t count = iov_iter_count(iter);
@@ -3682,7 +3681,7 @@ static ssize_t ext4_direct_IO_write(struct kiocb *iocb, struct iov_iter *iter)
goto out;
}
orphan = 1;
- ei->i_disksize = inode->i_size;
+ ext4_update_i_disksize(inode, inode->i_size);
ext4_journal_stop(handle);
}
@@ -3790,7 +3789,7 @@ static ssize_t ext4_direct_IO_write(struct kiocb *iocb, struct iov_iter *iter)
if (ret > 0) {
loff_t end = offset + ret;
if (end > inode->i_size) {
- ei->i_disksize = end;
+ ext4_update_i_disksize(inode, end);
i_size_write(inode, end);
/*
* We're going to return a positive `ret'
--
2.14.3
