On Wed, Sep 10, 2025 at 01:01:49PM +1000, NeilBrown wrote:
> On Tue, 09 Sep 2025, Al Viro wrote:
> > On Tue, Sep 09, 2025 at 02:43:21PM +1000, NeilBrown wrote:
> >
> > > d_instantiate(dentry, inode);
> > > - dget(dentry);
> > > -fail:
> > > - inode_unlock(d_inode(parent));
> > > - return dentry;
> > > + return simple_end_creating(dentry);
> >
> > No. This is the wrong model - dget() belongs with d_instantiate()
> > here; your simple_end_creating() calling conventions are wrong.
>
> I can see that I shouldn't have removed the dget() there - thanks.
> It is not entirely clear why hypfs_create_file() returns with two
> references held to the dentry....
> I see now one is added either to ->update_file or the list at
> hypfs_last_dentry, and the other is disposed of by kill_litter_super().
>
> But apart from that one error is there something broader wrong with the
> patch? You say "the wrong model" but I don't see it.
See below for hypfs:
commit c0c58d3cadfcefcf25f4885b47c47d6e6a3f9aee
Author: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Date: Thu May 9 16:00:48 2024 -0400
hypfs: don't pin dentries twice
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 <viro@xxxxxxxxxxxxxxxxxx>
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;
