btrfs: fix inode rbtree corruption

Node may not be inserted over existing node. This causes inode tree
corruption and I was seeing crashes in inode_tree_del which I can not
reproduce after this patch.

The other way to fix this would be to tie inode lifetime in the rbtree
with inode while not in freeing state. I had a look at this but it is
not so trivial at this point. At least this patch gets things working again.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Chris Mason <chris.mason@oracle.com>
Acked-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 14 insertions, 7 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 272b9b2bea86..59cba180fe83 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3099,8 +3099,12 @@ static void inode_tree_add(struct inode *inode)
 {
         struct btrfs_root *root = BTRFS_I(inode)->root;
         struct btrfs_inode *entry;
-        struct rb_node **p = &root->inode_tree.rb_node;
-        struct rb_node *parent = NULL;
+        struct rb_node **p;
+        struct rb_node *parent;
+
+again:
+        p = &root->inode_tree.rb_node;
+        parent = NULL;
 
         spin_lock(&root->inode_lock);
         while (*p) {
@@ -3108,13 +3112,16 @@ static void inode_tree_add(struct inode *inode)
                 entry = rb_entry(parent, struct btrfs_inode, rb_node);
 
                 if (inode->i_ino < entry->vfs_inode.i_ino)
-                        p = &(*p)->rb_left;
+                        p = &parent->rb_left;
                 else if (inode->i_ino > entry->vfs_inode.i_ino)
-                        p = &(*p)->rb_right;
+                        p = &parent->rb_right;
                 else {
                         WARN_ON(!(entry->vfs_inode.i_state &
                                   (I_WILL_FREE | I_FREEING | I_CLEAR)));
-                        break;
+                        rb_erase(parent, &root->inode_tree);
+                        RB_CLEAR_NODE(parent);
+                        spin_unlock(&root->inode_lock);
+                        goto again;
                 }
         }
         rb_link_node(&BTRFS_I(inode)->rb_node, parent, p);
@@ -3126,12 +3133,12 @@ static void inode_tree_del(struct inode *inode)
 {
         struct btrfs_root *root = BTRFS_I(inode)->root;
 
+        spin_lock(&root->inode_lock);
         if (!RB_EMPTY_NODE(&BTRFS_I(inode)->rb_node)) {
-                spin_lock(&root->inode_lock);
                 rb_erase(&BTRFS_I(inode)->rb_node, &root->inode_tree);
-                spin_unlock(&root->inode_lock);
                 RB_CLEAR_NODE(&BTRFS_I(inode)->rb_node);
         }
+        spin_unlock(&root->inode_lock);
 }
 
 static noinline void init_btrfs_i(struct inode *inode)