Btrfs: Fix data=ordered vs wait_on_inode deadlock on older kernels

Using ilookup5 during data=ordered writeback could deadlock on I_LOCK.  This
saves a pointer to the inode instead.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index cba2b623d02e..3ee51e10c187 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -25,6 +25,7 @@
 struct tree_entry {
         u64 root_objectid;
         u64 objectid;
+        struct inode *inode;
         struct rb_node rb_node;
 };
 
@@ -144,6 +145,7 @@ int btrfs_add_ordered_inode(struct inode *inode)
         write_lock(&tree->lock);
         entry->objectid = inode->i_ino;
         entry->root_objectid = root_objectid;
+        entry->inode = inode;
 
         node = tree_insert(&tree->tree, root_objectid,
                            inode->i_ino, &entry->rb_node);
@@ -159,7 +161,8 @@ int btrfs_add_ordered_inode(struct inode *inode)
 }
 
 int btrfs_find_first_ordered_inode(struct btrfs_ordered_inode_tree *tree,
-                                       u64 *root_objectid, u64 *objectid)
+                                   u64 *root_objectid, u64 *objectid,
+                                   struct inode **inode)
 {
         struct tree_entry *entry;
         struct rb_node *node;
@@ -184,13 +187,16 @@ int btrfs_find_first_ordered_inode(struct btrfs_ordered_inode_tree *tree,
         }
 
         *root_objectid = entry->root_objectid;
+        *inode = entry->inode;
+        atomic_inc(&entry->inode->i_count);
         *objectid = entry->objectid;
         write_unlock(&tree->lock);
         return 1;
 }
 
 int btrfs_find_del_first_ordered_inode(struct btrfs_ordered_inode_tree *tree,
-                                       u64 *root_objectid, u64 *objectid)
+                                       u64 *root_objectid, u64 *objectid,
+                                       struct inode **inode)
 {
         struct tree_entry *entry;
         struct rb_node *node;
@@ -216,6 +222,8 @@ int btrfs_find_del_first_ordered_inode(struct btrfs_ordered_inode_tree *tree,
 
         *root_objectid = entry->root_objectid;
         *objectid = entry->objectid;
+        *inode = entry->inode;
+        atomic_inc(&entry->inode->i_count);
         rb_erase(node, &tree->tree);
         write_unlock(&tree->lock);
         kfree(entry);