Re: [PATCH v3 1/2] mm: protect free_pgtables with mmap_lock write lock in exit_mmap

[Matthew Wilcox]

On Tue, Dec 07, 2021 at 01:50:30PM -0800, Suren Baghdasaryan wrote:
> - Added a comment for vm_operations_struct::close, documenting restriction for
> taking mmap_lock in the callback, per Michal Hocko and Matthew Wilcox

This should be a separate patch because it stands alone, but ...

>  struct vm_operations_struct {
>  	void (*open)(struct vm_area_struct * area);
> +    /*
> +     * Called with mmap_lock lock held for write from __split_vma and
> +     * remove_vma, therefore should never take that lock.
> +     */

Your whitespace indentation is weird.  And it'd be nice to make this a
kernel-doc comment (I know none of the others are, but that should be
fixed too).  And naming the functions that call it is wrong too.

	/**
	 * @close: Called when the VMA is being removed from the MM.
	 * Context: Caller holds mmap_lock.
	 */