btrfs: sanitizing ->fs_info, part 4

A new helper: btrfs_alloc_root(fs_info); allocates btrfs_root
and sets ->fs_info.  All places allocating the suckers converted
to it.  At that point we *never* reassign ->fs_info of btrfs_root;
it's set before anyone sees the address of newly allocated
struct btrfs_root and never assigned anywhere else.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

3 files changed, 18 insertions, 20 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 06480fcf0fb3..ee846ce58846 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1215,6 +1215,14 @@ static int find_and_setup_root(struct btrfs_root *tree_root,
         return 0;
 }
 
+struct btrfs_root *btrfs_alloc_root(struct btrfs_fs_info *fs_info)
+{
+        struct btrfs_root *root = kzalloc(sizeof(*root), GFP_NOFS);
+        if (root)
+                root->fs_info = fs_info;
+        return root;
+}
+
 static struct btrfs_root *alloc_log_tree(struct btrfs_trans_handle *trans,
                                          struct btrfs_fs_info *fs_info)
 {
@@ -1222,11 +1230,10 @@ static struct btrfs_root *alloc_log_tree(struct btrfs_trans_handle *trans,
         struct btrfs_root *tree_root = fs_info->tree_root;
         struct extent_buffer *leaf;
 
-        root = kzalloc(sizeof(*root), GFP_NOFS);
+        root = btrfs_alloc_root(fs_info);
         if (!root)
                 return ERR_PTR(-ENOMEM);
 
-        root->fs_info = fs_info;
         __setup_root(tree_root->nodesize, tree_root->leafsize,
                      tree_root->sectorsize, tree_root->stripesize,
                      root, fs_info, BTRFS_TREE_LOG_OBJECTID);
@@ -1317,10 +1324,9 @@ struct btrfs_root *btrfs_read_fs_root_no_radix(struct btrfs_root *tree_root,
         u32 blocksize;
         int ret = 0;
 
-        root = kzalloc(sizeof(*root), GFP_NOFS);
+        root = btrfs_alloc_root(fs_info);
         if (!root)
                 return ERR_PTR(-ENOMEM);
-        root->fs_info = fs_info;
         if (location->offset == (u64)-1) {
                 ret = find_and_setup_root(tree_root, fs_info,
                                           location->objectid, root);
@@ -1900,23 +1906,15 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         int num_backups_tried = 0;
         int backup_index = 0;
 
-        extent_root = fs_info->extent_root =
-                kzalloc(sizeof(struct btrfs_root), GFP_NOFS);
-        csum_root = fs_info->csum_root =
-                kzalloc(sizeof(struct btrfs_root), GFP_NOFS);
-        chunk_root = fs_info->chunk_root =
-                kzalloc(sizeof(struct btrfs_root), GFP_NOFS);
-        dev_root = fs_info->dev_root =
-                kzalloc(sizeof(struct btrfs_root), GFP_NOFS);
+        extent_root = fs_info->extent_root = btrfs_alloc_root(fs_info);
+        csum_root = fs_info->csum_root = btrfs_alloc_root(fs_info);
+        chunk_root = fs_info->chunk_root = btrfs_alloc_root(fs_info);
+        dev_root = fs_info->dev_root = btrfs_alloc_root(fs_info);
 
         if (!extent_root || !csum_root || !chunk_root || !dev_root) {
                 err = -ENOMEM;
                 goto fail;
         }
-        chunk_root->fs_info = fs_info;
-        extent_root->fs_info = fs_info;
-        dev_root->fs_info = fs_info;
-        csum_root->fs_info = fs_info;
 
         ret = init_srcu_struct(&fs_info->subvol_srcu);
         if (ret) {
@@ -2372,13 +2370,12 @@ retry_root_backup:
                      btrfs_level_size(tree_root,
                                       btrfs_super_log_root_level(disk_super));
 
-                log_tree_root = kzalloc(sizeof(struct btrfs_root), GFP_NOFS);
+                log_tree_root = btrfs_alloc_root(fs_info);
                 if (!log_tree_root) {
                         err = -ENOMEM;
                         goto fail_trans_kthread;
                 }
 
-                log_tree_root->fs_info = fs_info;
                 __setup_root(nodesize, leafsize, sectorsize, stripesize,
                              log_tree_root, fs_info, BTRFS_TREE_LOG_OBJECTID);
 
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index c99d0a8f13fa..2bb5f59ddf95 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -86,6 +86,8 @@ int btrfs_init_log_root_tree(struct btrfs_trans_handle *trans,
 int btrfs_add_log_tree(struct btrfs_trans_handle *trans,
                        struct btrfs_root *root);
 
+struct btrfs_root *btrfs_alloc_root(struct btrfs_fs_info *fs_info);
+
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 void btrfs_init_lockdep(void);
 void btrfs_set_buffer_lockdep_class(u64 objectid,
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index b9fd62a0fca2..e9f876a1655b 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -901,12 +901,11 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags,
         if (!fs_info)
                 return ERR_PTR(-ENOMEM);
 
-        fs_info->tree_root = kzalloc(sizeof(struct btrfs_root), GFP_NOFS);
+        fs_info->tree_root = btrfs_alloc_root(fs_info);
         if (!fs_info->tree_root) {
                 error = -ENOMEM;
                 goto error_fs_info;
         }
-        fs_info->tree_root->fs_info = fs_info;
         fs_info->fs_devices = fs_devices;
 
         fs_info->super_copy = kzalloc(BTRFS_SUPER_INFO_SIZE, GFP_NOFS);