Re: [PATCH 3/3] mm/vma: remove mmap() retry merge

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

On Fri, May 09, 2025 at 11:45:45AM +0200, David Hildenbrand wrote:
> On 07.05.25 13:03, Lorenzo Stoakes wrote:
> > We have now introduced a mechanism that obviates the need for a reattempted
> > merge via the mmap_prepare() file hook, so eliminate this functionality
> > altogether.
> >
> > The retry merge logic has been the cause of a great deal of complexity in
> > the past and required a great deal of careful manoeuvring of code to ensure
> > its continued and correct functionality.
> >
> > It has also recently been involved in an issue surrounding maple tree
> > state, which again points to its problematic nature.
> >
> > We make it much easier to reason about mmap() logic by eliminating this and
> > simply writing a VMA once. This also opens the doors to future optimisation
> > and improvement in the mmap() logic.
> >
> > For any device or file system which encounters unwanted VMA fragmentation
> > as a result of this change (that is, having not implemented .mmap_prepare
> > hooks), the issue is easily resolvable by doing so.
> >
> > Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
>
> Reviewed-by: David Hildenbrand <david@redhat.com>

Thanks!

>
> --
> Cheers,
>
> David / dhildenb
>