Re: [PATCH] kernfs: allocate inodes outside kernfs_rwsem

[Shakeel Butt]

On Thu, Oct 15, 2026 at 03:11:10PM -0700, Shakeel Butt wrote:
[...]
>  
> @@ -173,7 +171,7 @@ static struct dentry *kernfs_get_parent_dentry(struct dentry *child)
>  	struct kernfs_root *root = kernfs_root(kn);
>  
>  	guard(rwsem_read)(&root->kernfs_rwsem);
> -	return d_obtain_alias(kernfs_get_inode(child->d_sb, kernfs_parent(kn)));
> +	return d_obtain_alias(kernfs_iget(child->d_sb, kernfs_parent(kn)));

Sashiko is complaining that inode allocation has been moved outside kernfs_rwsem
but d_obtain_alias() may still allocate dentry under this lock. The fix is
simple. Something like the following:

	scoped_guard(rwsem_read, &root->kernfs_rwsem)
		inode = kernfs_iget(child->d_sb, kernfs_parent(kn));
	
	return d_obtain_alias(inode);

I am testing this change and I will wait for human response/review before
sending out the v2 of this patch.