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

[Suren Baghdasaryan]

On Tue, Dec 7, 2021 at 2:07 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
>
> 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 ...

I thought about it and since it was relevant to the change in
remove_vma locking, I thought it would fit here. However, if you
insist on splitting it, I'll post it as a separate patch. Please let
me know.

>
> >  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.
>          */

Ack. Will change and include in the next respin once I hear from you
on the preference for a separate patch.
Thanks!