btrfs: preparation to fixing mount/umount race

We need fs_info and root to live until the moment when the victim
superblock leaves the list, so we need to postpone free_fs_info()
until after ->put_super().  The call is buried in close_ctree(),
though, so we need to lift it into the callers (including
btrfs_put_super()) first.

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

2 files changed, 6 insertions, 3 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index f99a099a774..dcb5d949b54 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2424,6 +2424,7 @@ retry_root_backup:
                 up_read(&fs_info->cleanup_work_sem);
                 if (err) {
                         close_ctree(tree_root);
+                        free_fs_info(fs_info);
                         return ERR_PTR(err);
                 }
         }
@@ -3059,8 +3060,6 @@ int close_ctree(struct btrfs_root *root)
         bdi_destroy(&fs_info->bdi);
         cleanup_srcu_struct(&fs_info->subvol_srcu);
 
-        free_fs_info(fs_info);
-
         return 0;
 }
 
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index ae488aa1966..a3f435e5898 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -151,6 +151,7 @@ static void btrfs_put_super(struct super_block *sb)
         int ret;
 
         ret = close_ctree(root);
+        free_fs_info(root->fs_info);
         sb->s_fs_info = NULL;
 
         (void)ret; /* FIXME: need to fix VFS to return error? */
@@ -589,6 +590,7 @@ static int btrfs_fill_super(struct super_block *sb,
         struct inode *inode;
         struct dentry *root_dentry;
         struct btrfs_root *tree_root;
+        struct btrfs_fs_info *fs_info;
         struct btrfs_key key;
         int err;
 
@@ -609,12 +611,13 @@ static int btrfs_fill_super(struct super_block *sb,
                 printk("btrfs: open_ctree failed\n");
                 return PTR_ERR(tree_root);
         }
+        fs_info = tree_root->fs_info;
         sb->s_fs_info = tree_root;
 
         key.objectid = BTRFS_FIRST_FREE_OBJECTID;
         key.type = BTRFS_INODE_ITEM_KEY;
         key.offset = 0;
-        inode = btrfs_iget(sb, &key, tree_root->fs_info->fs_root, NULL);
+        inode = btrfs_iget(sb, &key, fs_info->fs_root, NULL);
         if (IS_ERR(inode)) {
                 err = PTR_ERR(inode);
                 goto fail_close;
@@ -635,6 +638,7 @@ static int btrfs_fill_super(struct super_block *sb,
 
 fail_close:
         close_ctree(tree_root);
+        free_fs_info(fs_info);
         return err;
 }