hypfs dentries end up with refcount 2 when they are not busy.
Refcount 1 is enough to keep them pinned, and going that way
allows to simplify things nicely:
        * don't need to drop an extra reference before the
call of kill_litter_super() in ->kill_sb(); all we need
there is to reset the cleanup list - everything on it will
be taken out automatically.
        * we can make use of simple_recursive_removal() on
tree rebuilds; just make sure that only children of root
end up in the cleanup list and hypfs_delete_tree() becomes
much simpler

Signed-off-by: Al Viro <[email protected]>
---
 arch/s390/hypfs/inode.c | 41 ++++++++++-------------------------------
 1 file changed, 10 insertions(+), 31 deletions(-)

diff --git a/arch/s390/hypfs/inode.c b/arch/s390/hypfs/inode.c
index 96409573c75d..a4dc8e13d999 100644
--- a/arch/s390/hypfs/inode.c
+++ b/arch/s390/hypfs/inode.c
@@ -61,33 +61,17 @@ static void hypfs_update_update(struct super_block *sb)
 
 static void hypfs_add_dentry(struct dentry *dentry)
 {
-       dentry->d_fsdata = hypfs_last_dentry;
-       hypfs_last_dentry = dentry;
-}
-
-static void hypfs_remove(struct dentry *dentry)
-{
-       struct dentry *parent;
-
-       parent = dentry->d_parent;
-       inode_lock(d_inode(parent));
-       if (simple_positive(dentry)) {
-               if (d_is_dir(dentry))
-                       simple_rmdir(d_inode(parent), dentry);
-               else
-                       simple_unlink(d_inode(parent), dentry);
+       if (IS_ROOT(dentry->d_parent)) {
+               dentry->d_fsdata = hypfs_last_dentry;
+               hypfs_last_dentry = dentry;
        }
-       d_drop(dentry);
-       dput(dentry);
-       inode_unlock(d_inode(parent));
 }
 
-static void hypfs_delete_tree(struct dentry *root)
+static void hypfs_delete_tree(void)
 {
        while (hypfs_last_dentry) {
-               struct dentry *next_dentry;
-               next_dentry = hypfs_last_dentry->d_fsdata;
-               hypfs_remove(hypfs_last_dentry);
+               struct dentry *next_dentry = hypfs_last_dentry->d_fsdata;
+               simple_recursive_removal(hypfs_last_dentry, NULL);
                hypfs_last_dentry = next_dentry;
        }
 }
@@ -184,14 +168,14 @@ static ssize_t hypfs_write_iter(struct kiocb *iocb, 
struct iov_iter *from)
                rc = -EBUSY;
                goto out;
        }
-       hypfs_delete_tree(sb->s_root);
+       hypfs_delete_tree();
        if (machine_is_vm())
                rc = hypfs_vm_create_files(sb->s_root);
        else
                rc = hypfs_diag_create_files(sb->s_root);
        if (rc) {
                pr_err("Updating the hypfs tree failed\n");
-               hypfs_delete_tree(sb->s_root);
+               hypfs_delete_tree();
                goto out;
        }
        hypfs_update_update(sb);
@@ -326,13 +310,9 @@ static void hypfs_kill_super(struct super_block *sb)
 {
        struct hypfs_sb_info *sb_info = sb->s_fs_info;
 
-       if (sb->s_root)
-               hypfs_delete_tree(sb->s_root);
-       if (sb_info && sb_info->update_file)
-               hypfs_remove(sb_info->update_file);
-       kfree(sb->s_fs_info);
-       sb->s_fs_info = NULL;
+       hypfs_last_dentry = NULL;
        kill_litter_super(sb);
+       kfree(sb_info);
 }
 
 static struct dentry *hypfs_create_file(struct dentry *parent, const char 
*name,
@@ -367,7 +347,6 @@ static struct dentry *hypfs_create_file(struct dentry 
*parent, const char *name,
                BUG();
        inode->i_private = data;
        d_instantiate(dentry, inode);
-       dget(dentry);
 fail:
        inode_unlock(d_inode(parent));
        return dentry;
-- 
2.47.3


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