Re: [PATCH v2 7/9] mm: Run the fault-around code under the VMA lock

[Matthew Wilcox <willy@xxxxxxxxxxxxx>]

On Thu, Jul 13, 2023 at 08:32:27PM -0700, Suren Baghdasaryan wrote:
> On Tue, Jul 11, 2023 at 1:20 PM Matthew Wilcox (Oracle)
> <willy@xxxxxxxxxxxxx> wrote:
> >
> > The map_pages fs method should be safe to run under the VMA lock instead
> > of the mmap lock.  This should have a measurable reduction in contention
> > on the mmap lock.
> >
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> 
> I'll trust your claim that vmf->vma->vm_ops->map_pages() never rely on
> mmap_lock. I think it makes sense but I did not check every case :)

Fortunately, there's really only one implementation of ->map_pages()
and it's filemap_map_pages().  afs_vm_map_pages() is a thin wrapper
around it.