ext4: protect extent conversion after DIO with i_dio_count
Make sure extent conversion after DIO happens while i_dio_count is
still elevated so that inode_dio_wait() waits until extent conversion
is done. This removes the need for explicit waiting for extent
conversion in some cases.
Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 510dba7..eb4ddfe 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3036,11 +3036,18 @@
BUG_ON(iocb->private == NULL);
+ /*
+ * Make all waiters for direct IO properly wait also for extent
+ * conversion. This also disallows race between truncate() and
+ * overwrite DIO as i_dio_count needs to be incremented under i_mutex.
+ */
+ if (rw == WRITE)
+ atomic_inc(&inode->i_dio_count);
+
/* If we do a overwrite dio, i_mutex locking can be released */
overwrite = *((int *)iocb->private);
if (overwrite) {
- atomic_inc(&inode->i_dio_count);
down_read(&EXT4_I(inode)->i_data_sem);
mutex_unlock(&inode->i_mutex);
}
@@ -3143,9 +3150,10 @@
}
retake_lock:
+ if (rw == WRITE)
+ inode_dio_done(inode);
/* take i_mutex locking again if we do a ovewrite dio */
if (overwrite) {
- inode_dio_done(inode);
up_read(&EXT4_I(inode)->i_data_sem);
mutex_lock(&inode->i_mutex);
}