[PATCH] ext4: add a new spinlock i_raw_lock to protect the ext4's raw inode

[Theodore Ts'o]

To avoid potential data races, use a spinlock which protects the raw
(on-disk) inode.

Signed-off-by: "Theodore Ts'o" <tytso at mit.edu>
---
 fs/ext4/ext4.h  | 2 ++
 fs/ext4/inode.c | 5 ++++-
 fs/ext4/super.c | 1 +
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 86c2cda..1d08a1b 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -875,6 +875,8 @@ struct ext4_inode_info {
 	struct inode vfs_inode;
 	struct jbd2_inode *jinode;
 
+	spinlock_t i_raw_lock;	/* protects updates to the raw inode */
+
 	/*
 	 * File creation time. Its function is same as that of
 	 * struct timespec i_{a,c,m}time in the generic inode.
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 2eb5fad..1ee8ff6 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4311,7 +4311,9 @@ static int ext4_do_update_inode(handle_t *handle,
 	uid_t i_uid;
 	gid_t i_gid;
 
-	/* For fields not not tracking in the in-memory inode,
+	spin_lock(&ei->i_raw_lock);
+
+	/* For fields not tracked in the in-memory inode,
 	 * initialise them to zero for new inodes. */
 	if (ext4_test_inode_state(inode, EXT4_STATE_NEW))
 		memset(raw_inode, 0, EXT4_SB(inode->i_sb)->s_inode_size);
@@ -4419,6 +4421,7 @@ static int ext4_do_update_inode(handle_t *handle,
 
 	ext4_update_inode_fsync_trans(handle, inode, need_datasync);
 out_brelse:
+	spin_unlock(&ei->i_raw_lock);
 	brelse(bh);
 	ext4_std_error(inode->i_sb, err);
 	return err;
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index c4895c1..1f8cb18 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -879,6 +879,7 @@ static struct inode *ext4_alloc_inode(struct super_block *sb)
 		return NULL;
 
 	ei->vfs_inode.i_version = 1;
+	spin_lock_init(&ei->i_raw_lock);
 	INIT_LIST_HEAD(&ei->i_prealloc_list);
 	spin_lock_init(&ei->i_prealloc_lock);
 	ext4_es_init_tree(&ei->i_es_tree);
-- 
1.9.0