btrfs: get ->kill_sb() of its own

... and move free_fs_info() to that, out of ->put_super().  Do NOT
set ->s_fs_info to NULL in the latter; we need it for sget() to
be able to see and wait for fs in the middle of umount if we get a
mount/umount race.

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

1 files changed, 18 insertions, 9 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index a3f435e58987..eca48624a4f0 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -147,14 +147,13 @@ void __btrfs_std_error(struct btrfs_fs_info *fs_info, const char *function,
 
 static void btrfs_put_super(struct super_block *sb)
 {
-        struct btrfs_root *root = btrfs_sb(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? */
+        (void)close_ctree(btrfs_sb(sb));
+        /* FIXME: need to fix VFS to return error? */
+        /* AV: return it _where_?  ->put_super() can be triggered by any number
+         * of async events, up to and including delivery of SIGKILL to the
+         * last process that kept it busy.  Or segfault in the aforementioned
+         * process...  Whom would you report that to?
+         */
 }
 
 enum {
@@ -1223,11 +1222,21 @@ static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
         return 0;
 }
 
+static void btrfs_kill_super(struct super_block *sb)
+{
+        struct btrfs_fs_info *fs_info = NULL;
+        if (sb->s_root)
+                fs_info = btrfs_sb(sb)->fs_info;
+        kill_anon_super(sb);
+        if (fs_info)
+                free_fs_info(fs_info);
+}
+
 static struct file_system_type btrfs_fs_type = {
         .owner          = THIS_MODULE,
         .name           = "btrfs",
         .mount          = btrfs_mount,
-        .kill_sb        = kill_anon_super,
+        .kill_sb        = btrfs_kill_super,
         .fs_flags       = FS_REQUIRES_DEV,
 };