linux-stable.git/tools/testing/vma, branch master

mm: fix CONFIG_STACK_GROWSUP typo in tools/testing/vma/include/dup.h

2026-08-25T01:43:12+00:00

Commit 2b6a3f061f11 ("mm: declare VMA flags by bit") significantly
refactored the header file include/linux/mm.h.  In that step, it
introduced a typo in an ifdef, referring to a non-existing config option
STACK_GROWS_UP, whereas the actual config option is called STACK_GROWSUP.

Commit 40a4af52e047 ("mm: fix CONFIG_STACK_GROWSUP typo in mm.h") fixed
this typo in the mm.h header file, but did not update the copy of the code
in tools/testing/vma/include/dup.h.  Update this copy as well.

Commit message adapted from the above-referenced fix to mm.h.

Link: https://lore.kernel.org/20260611012258.432043-1-enelsonmoore@gmail.com
Signed-off-by: Ethan Nelson-Moore 
Reviewed-by: Lorenzo Stoakes 
Cc: Alice Ryhl 
Cc: Jann Horn 
Cc: Liam R. Howlett 
Cc: Pedro Falcato 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

tools/testing/vma: expand VMA merge tests to assert anon pgoff

2026-08-25T01:42:53+00:00

Now we have introduced the VMA anonymous page offset attribute and update
it when VMAs are manipulated, update VMA merge tests to assert that the
anonymous page offset is as expected.

Also update instances where we could use vma_start_pgoff() to do so.

Link: https://lore.kernel.org/20260813-b4-scalable-cow-virt-pgoff-v5-15-c21581c0c3c8@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) 
Acked-by: David Hildenbrand (Arm) 
Cc: Adrian Hunter 
Cc: Alexander Deucher 
Cc: Alexander Gordeev 
Cc: Alexander Shishkin 
Cc: Alistair Popple 
Cc: Arnaldo Carvalho de Melo 
Cc: Arnd Bergmann 
Cc: Baolin Wang 
Cc: Baoquan He 
Cc: Barry Song 
Cc: Boris Brezillon 
Cc: Byungchul Park 
Cc: Chengming Zhou 
Cc: Chris Li 
Cc: Christan König 
Cc: Christian Borntraeger 
Cc: Claudio Imbrenda 
Cc: Dave Airlie 
Cc: Dev Jain 
Cc: Gerald Schaefer 
Cc: Greg Kroah-Hartman 
Cc: Gregory Price (Meta) 
Cc: Harry Yoo 
Cc: Heiko Carstens 
Cc: Huang Ray 
Cc: "Huang, Ying" 
Cc: Ian Rogers 
Cc: Ingo Molnar 
Cc: James Clark 
Cc: Jan Kara 
Cc: Jann Horn 
Cc: Janosch Frank 
Cc: Jason Gunthorpe 
Cc: Jiri Olsa 
Cc: John Hubbard 
Cc: Joshua Hahn 
Cc: Kairui Song 
Cc: Kees Cook 
Cc: Kemeng Shi 
Cc: Lance Yang 
Cc: Liam R. Howlett 
Cc: Liviu Dudau 
Cc: Maarten Lankhorst 
Cc: Marc Rutland 
Cc: "Masami Hiramatsu (Google)" 
Cc: Matthew Auld 
Cc: Matthew Brost 
Cc: Matthew Wilcox (Oracle) 
Cc: Maxime Ripard 
Cc: Miaohe Lin 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Muchun Song 
Cc: Namhyung kim 
Cc: Naoya Horiguchi 
Cc: Nhat Pham 
Cc: Nico Pache 
Cc: Oleg Nesterov 
Cc: Oscar Salvador 
Cc: Pedro Falcato 
Cc: Peter Xu 
Cc: Peter Zijlstra 
Cc: Rakie Kim 
Cc: Rik van Riel 
Cc: Rodrigo Vivi 
Cc: Ryan Roberts 
Cc: Steven Price 
Cc: Suren Baghdasaryan 
Cc: Sven Schnelle 
Cc: Thomas Hellström 
Cc: Thomas Zimemrmann 
Cc: Vasily Gorbik 
Cc: Vlastimil Babka 
Cc: xu xin 
Cc: Zi Yan 
Signed-off-by: Andrew Morton

mm: propagate VMA anonymous page offset on map, remap, split + merge

2026-08-25T01:42:52+00:00

We must correctly update VMA anonymous page offset state on all VMA
operations that would result in it changing, with special attention given
to remapping.

We cover most cases by simply updating vma_set_range() to do so (with a
new anonymous page offset parameter), but also notably must update the
merging and mapping logic to propagate this parameter correctly.

The remap logic remains the same - we may update the anonymous page offset
if the VMA is unfaulted, but now this applies to MAP_PRIVATE file-backed
mappings too, so we update the code to reflect this.

Note that we use __linear_anon_page_index() upon remap as the VMA may be
shared, in order that we update the field consistently regardless of VMA
type.

Similarly, pass through anon page offset to the merge logic, updating the
vma_merge_struct struct to propagate it, and also use
__linear_anon_page_index() to obtain the anonymous page index so it can be
safely used for both shared and MAP_PRIVATE file-backed mappings.

In copy_vma(), the anonymous page offset is updated regardless of whether
the mapping is a CoW mapping or not.  This is both to keep the anonymous
page offset consistent even for non-CoW mappings (it is set so should at
least remain correct) and makes the logic cleaner.

A self-merge however remains permitted only for mappings which can have a
populated vma->anon_vma and do not require alignment on a separate file
offset - that is pure anonymous VMAs, so only set can_self_merge if
vma_is_anonymous().

Finally, we update insert_vm_struct() to correctly set the anonymous page
offset on insertion of a VMA.

We simply ensure state is correctly propagated here, so no functional
changes are intended.

Also update VMA userland tests to reflect this change.

Link: https://lore.kernel.org/20260813-b4-scalable-cow-virt-pgoff-v5-9-c21581c0c3c8@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) 
Acked-by: David Hildenbrand (Arm) 
Cc: Adrian Hunter 
Cc: Alexander Deucher 
Cc: Alexander Gordeev 
Cc: Alexander Shishkin 
Cc: Alistair Popple 
Cc: Arnaldo Carvalho de Melo 
Cc: Arnd Bergmann 
Cc: Baolin Wang 
Cc: Baoquan He 
Cc: Barry Song 
Cc: Boris Brezillon 
Cc: Byungchul Park 
Cc: Chengming Zhou 
Cc: Chris Li 
Cc: Christan König 
Cc: Christian Borntraeger 
Cc: Claudio Imbrenda 
Cc: Dave Airlie 
Cc: Dev Jain 
Cc: Gerald Schaefer 
Cc: Greg Kroah-Hartman 
Cc: Gregory Price (Meta) 
Cc: Harry Yoo 
Cc: Heiko Carstens 
Cc: Huang Ray 
Cc: "Huang, Ying" 
Cc: Ian Rogers 
Cc: Ingo Molnar 
Cc: James Clark 
Cc: Jan Kara 
Cc: Jann Horn 
Cc: Janosch Frank 
Cc: Jason Gunthorpe 
Cc: Jiri Olsa 
Cc: John Hubbard 
Cc: Joshua Hahn 
Cc: Kairui Song 
Cc: Kees Cook 
Cc: Kemeng Shi 
Cc: Lance Yang 
Cc: Liam R. Howlett 
Cc: Liviu Dudau 
Cc: Maarten Lankhorst 
Cc: Marc Rutland 
Cc: "Masami Hiramatsu (Google)" 
Cc: Matthew Auld 
Cc: Matthew Brost 
Cc: Matthew Wilcox (Oracle) 
Cc: Maxime Ripard 
Cc: Miaohe Lin 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Muchun Song 
Cc: Namhyung kim 
Cc: Naoya Horiguchi 
Cc: Nhat Pham 
Cc: Nico Pache 
Cc: Oleg Nesterov 
Cc: Oscar Salvador 
Cc: Pedro Falcato 
Cc: Peter Xu 
Cc: Peter Zijlstra 
Cc: Rakie Kim 
Cc: Rik van Riel 
Cc: Rodrigo Vivi 
Cc: Ryan Roberts 
Cc: Steven Price 
Cc: Suren Baghdasaryan 
Cc: Sven Schnelle 
Cc: Thomas Hellström 
Cc: Thomas Zimemrmann 
Cc: Vasily Gorbik 
Cc: Vlastimil Babka 
Cc: xu xin 
Cc: Zi Yan 
Signed-off-by: Andrew Morton

tools/testing/vma: add tests for copy_vma() self-merge

2026-08-25T01:42:51+00:00

Assert that a VMA can be moved backwards, forwards and between a preceding
VMA and its old self.

In the cases in which the VMA merges only with itself expect that to be
achieved by expanding its old self, so assert that these function
correctly.

However in the case of a merge between a preceding VMA and itself the
original VMA is removed, so assert that the preceding VMA replaces the one
passed in as vmap and the merge is as expected.

Link: https://lore.kernel.org/20260813-b4-scalable-cow-virt-pgoff-v5-8-c21581c0c3c8@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) 
Acked-by: David Hildenbrand (Arm) 
Cc: Adrian Hunter 
Cc: Alexander Deucher 
Cc: Alexander Gordeev 
Cc: Alexander Shishkin 
Cc: Alistair Popple 
Cc: Arnaldo Carvalho de Melo 
Cc: Arnd Bergmann 
Cc: Baolin Wang 
Cc: Baoquan He 
Cc: Barry Song 
Cc: Boris Brezillon 
Cc: Byungchul Park 
Cc: Chengming Zhou 
Cc: Chris Li 
Cc: Christan König 
Cc: Christian Borntraeger 
Cc: Claudio Imbrenda 
Cc: Dave Airlie 
Cc: Dev Jain 
Cc: Gerald Schaefer 
Cc: Greg Kroah-Hartman 
Cc: Gregory Price (Meta) 
Cc: Harry Yoo 
Cc: Heiko Carstens 
Cc: Huang Ray 
Cc: "Huang, Ying" 
Cc: Ian Rogers 
Cc: Ingo Molnar 
Cc: James Clark 
Cc: Jan Kara 
Cc: Jann Horn 
Cc: Janosch Frank 
Cc: Jason Gunthorpe 
Cc: Jiri Olsa 
Cc: John Hubbard 
Cc: Joshua Hahn 
Cc: Kairui Song 
Cc: Kees Cook 
Cc: Kemeng Shi 
Cc: Lance Yang 
Cc: Liam R. Howlett 
Cc: Liviu Dudau 
Cc: Maarten Lankhorst 
Cc: Marc Rutland 
Cc: "Masami Hiramatsu (Google)" 
Cc: Matthew Auld 
Cc: Matthew Brost 
Cc: Matthew Wilcox (Oracle) 
Cc: Maxime Ripard 
Cc: Miaohe Lin 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Muchun Song 
Cc: Namhyung kim 
Cc: Naoya Horiguchi 
Cc: Nhat Pham 
Cc: Nico Pache 
Cc: Oleg Nesterov 
Cc: Oscar Salvador 
Cc: Pedro Falcato 
Cc: Peter Xu 
Cc: Peter Zijlstra 
Cc: Rakie Kim 
Cc: Rik van Riel 
Cc: Rodrigo Vivi 
Cc: Ryan Roberts 
Cc: Steven Price 
Cc: Suren Baghdasaryan 
Cc: Sven Schnelle 
Cc: Thomas Hellström 
Cc: Thomas Zimemrmann 
Cc: Vasily Gorbik 
Cc: Vlastimil Babka 
Cc: xu xin 
Cc: Zi Yan 
Signed-off-by: Andrew Morton

mm/vma: fix self-merge check in copy_vma()

2026-08-25T01:42:51+00:00

The existing logic is very confusing so improve things.  Firstly rename
the confusing faulted_in_anon_vma variable to can_self_merge and update
this when the page offset is updated.

What is being checked for is a 'self-merge' - that is between the VMA
being remapped and its prior VMA (remember that this is copy_vma() - if a
non-MREMAP_DONTUNMAP remap the original VMA is only removed afterwards).

This can happen if the VMA is moved immediately adjacent to itself, either
before or after it:

		|----------------|----------------|
		|		 |                |
		v		 |		  v
	|...............||---------------||...............|
	|      new      ||      old      ||      new      |
	|...............||---------------||---------------|

In these cases the old VMA is simply expanded to cover the new range.

It is also possible for the move to both self-merge and merge with a prior
VMA if it is placed between a preceding VMA and its old self:

				|---------------|
				|		|
				v		|
	|---------------||...............||---------------|
	|      prev     ||     new       ||     old       |
	|---------------||...............||---------------|

In this case, the old VMA is removed and 'prev' is expanded and replaces
it.

Since copy_vma_and_data() which calls copy_vma() intends to reference the
old VMA after the merge, it must have this pointer updated.

This kind of self-merge is not possible with a succeeding merge, as the
merge always prefers to expand the preceding VMA if possible.

copy_vma() accounts for this by explicitly checking to see if a self-merge
occurred and updating the vmap pointer if so.  However it incorrect did so
even for a subsequent merge (this is simply a noop so it had no impact).

So change this to only check for the case which matters - a backwards
merge - and rearrange the parameters to make it clearer we're doing that -
i.e.  check new_vma->vm_start < old_vma_start (having already renamed
vma_start to old_vma_start to make it clear this is the previous VMA).

Also update the existing wall-of-text comment to be a lot clearer.

While we're here, replace the VM_BUG_ON_VMA() with a VM_WARN_ON_ONCE_VMA()
and update the VMA userland tests accordingly.

No functional change intended.

Link: https://lore.kernel.org/20260813-b4-scalable-cow-virt-pgoff-v5-7-c21581c0c3c8@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) 
Acked-by: David Hildenbrand (Arm) 
Cc: Adrian Hunter 
Cc: Alexander Deucher 
Cc: Alexander Gordeev 
Cc: Alexander Shishkin 
Cc: Alistair Popple 
Cc: Arnaldo Carvalho de Melo 
Cc: Arnd Bergmann 
Cc: Baolin Wang 
Cc: Baoquan He 
Cc: Barry Song 
Cc: Boris Brezillon 
Cc: Byungchul Park 
Cc: Chengming Zhou 
Cc: Chris Li 
Cc: Christan König 
Cc: Christian Borntraeger 
Cc: Claudio Imbrenda 
Cc: Dave Airlie 
Cc: Dev Jain 
Cc: Gerald Schaefer 
Cc: Greg Kroah-Hartman 
Cc: Gregory Price (Meta) 
Cc: Harry Yoo 
Cc: Heiko Carstens 
Cc: Huang Ray 
Cc: "Huang, Ying" 
Cc: Ian Rogers 
Cc: Ingo Molnar 
Cc: James Clark 
Cc: Jan Kara 
Cc: Jann Horn 
Cc: Janosch Frank 
Cc: Jason Gunthorpe 
Cc: Jiri Olsa 
Cc: John Hubbard 
Cc: Joshua Hahn 
Cc: Kairui Song 
Cc: Kees Cook 
Cc: Kemeng Shi 
Cc: Lance Yang 
Cc: Liam R. Howlett 
Cc: Liviu Dudau 
Cc: Maarten Lankhorst 
Cc: Marc Rutland 
Cc: "Masami Hiramatsu (Google)" 
Cc: Matthew Auld 
Cc: Matthew Brost 
Cc: Matthew Wilcox (Oracle) 
Cc: Maxime Ripard 
Cc: Miaohe Lin 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Muchun Song 
Cc: Namhyung kim 
Cc: Naoya Horiguchi 
Cc: Nhat Pham 
Cc: Nico Pache 
Cc: Oleg Nesterov 
Cc: Oscar Salvador 
Cc: Pedro Falcato 
Cc: Peter Xu 
Cc: Peter Zijlstra 
Cc: Rakie Kim 
Cc: Rik van Riel 
Cc: Rodrigo Vivi 
Cc: Ryan Roberts 
Cc: Steven Price 
Cc: Suren Baghdasaryan 
Cc: Sven Schnelle 
Cc: Thomas Hellström 
Cc: Thomas Zimemrmann 
Cc: Vasily Gorbik 
Cc: Vlastimil Babka 
Cc: xu xin 
Cc: Zi Yan 
Signed-off-by: Andrew Morton

mm: introduce linear_anon_page_index()

2026-08-25T01:42:50+00:00

This function provides the anonymous equivalent of linear_page_index(),
instead offsetting based on the anonymous page offset of the VMA.

It is valid only for anonymous or MAP_PRIVATE file-backed mappings, in
other words CoW mappings.

For pure anon VMAs, this will be equal to linear_page_index().

Assert that both of these invariants are true in linear_anon_page_index()
and implement the algorithm in __linear_anon_page_index().

Note that MAP_PRIVATE-/dev/zero mappings will satisfy vma_is_anonymous()
but not fulfill this invariant, so when asserting this we check
vma->vm_file to account for this.

We do not update callsites yet, so no functional change intended.

Also const-ify vma_is_anonymous() to make it compatible with the
const-ified linear_anon_page_index().

While we're here, update linear_page_index() to be more succinct.

VMA userland tests are also updated accordingly.

Link: https://lore.kernel.org/20260813-b4-scalable-cow-virt-pgoff-v5-3-c21581c0c3c8@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) 
Reviewed-by: Gregory Price (Meta) 
Acked-by: David Hildenbrand (Arm) 
Cc: Adrian Hunter 
Cc: Alexander Deucher 
Cc: Alexander Gordeev 
Cc: Alexander Shishkin 
Cc: Alistair Popple 
Cc: Arnaldo Carvalho de Melo 
Cc: Arnd Bergmann 
Cc: Baolin Wang 
Cc: Baoquan He 
Cc: Barry Song 
Cc: Boris Brezillon 
Cc: Byungchul Park 
Cc: Chengming Zhou 
Cc: Chris Li 
Cc: Christan König 
Cc: Christian Borntraeger 
Cc: Claudio Imbrenda 
Cc: Dave Airlie 
Cc: Dev Jain 
Cc: Gerald Schaefer 
Cc: Greg Kroah-Hartman 
Cc: Harry Yoo 
Cc: Heiko Carstens 
Cc: Huang Ray 
Cc: "Huang, Ying" 
Cc: Ian Rogers 
Cc: Ingo Molnar 
Cc: James Clark 
Cc: Jan Kara 
Cc: Jann Horn 
Cc: Janosch Frank 
Cc: Jason Gunthorpe 
Cc: Jiri Olsa 
Cc: John Hubbard 
Cc: Joshua Hahn 
Cc: Kairui Song 
Cc: Kees Cook 
Cc: Kemeng Shi 
Cc: Lance Yang 
Cc: Liam R. Howlett 
Cc: Liviu Dudau 
Cc: Maarten Lankhorst 
Cc: Marc Rutland 
Cc: "Masami Hiramatsu (Google)" 
Cc: Matthew Auld 
Cc: Matthew Brost 
Cc: Matthew Wilcox (Oracle) 
Cc: Maxime Ripard 
Cc: Miaohe Lin 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Muchun Song 
Cc: Namhyung kim 
Cc: Naoya Horiguchi 
Cc: Nhat Pham 
Cc: Nico Pache 
Cc: Oleg Nesterov 
Cc: Oscar Salvador 
Cc: Pedro Falcato 
Cc: Peter Xu 
Cc: Peter Zijlstra 
Cc: Rakie Kim 
Cc: Rik van Riel 
Cc: Rodrigo Vivi 
Cc: Ryan Roberts 
Cc: Steven Price 
Cc: Suren Baghdasaryan 
Cc: Sven Schnelle 
Cc: Thomas Hellström 
Cc: Thomas Zimemrmann 
Cc: Vasily Gorbik 
Cc: Vlastimil Babka 
Cc: xu xin 
Cc: Zi Yan 
Signed-off-by: Andrew Morton

mm: provide vma_[flags_]is_cow_mapping() and remove is_cow_mapping()

2026-08-25T01:42:50+00:00

All remaining callers of is_cow_mapping() are invoking it in the form of
is_cow_mapping(vma->vm_flags) or an indirected version of this.

Therefore, provide a helper - vma_is_cow_mapping() to directly test the
VMA.

Additionally provide a new helper vma_flags_is_cow_mapping() which
performs the check using the new vma_flags_t type, and share this logic
between vma_is_cow_mapping() and vma_desc_is_cow_mapping().

With these changes, no callers of is_cow_mapping() remain, so remove it.

Also update the userland VMA tests to reflect the change.

No functional change intended.

[akpm@linux-foundation.org: fix kerneldoc comment typo, per Lorenzo]
  Link: https://lore.kernel.org/aob1goSSPH6sTN9y@gremlin
Link: https://lore.kernel.org/20260813-b4-scalable-cow-virt-pgoff-v5-2-c21581c0c3c8@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) 
Acked-by: David Hildenbrand (Arm) 
Cc: Adrian Hunter 
Cc: Alexander Deucher 
Cc: Alexander Gordeev 
Cc: Alexander Shishkin 
Cc: Alistair Popple 
Cc: Arnaldo Carvalho de Melo 
Cc: Arnd Bergmann 
Cc: Baolin Wang 
Cc: Baoquan He 
Cc: Barry Song 
Cc: Boris Brezillon 
Cc: Byungchul Park 
Cc: Chengming Zhou 
Cc: Chris Li 
Cc: Christan König 
Cc: Christian Borntraeger 
Cc: Claudio Imbrenda 
Cc: Dave Airlie 
Cc: Dev Jain 
Cc: Gerald Schaefer 
Cc: Greg Kroah-Hartman 
Cc: Gregory Price (Meta) 
Cc: Harry Yoo 
Cc: Heiko Carstens 
Cc: Huang Ray 
Cc: "Huang, Ying" 
Cc: Ian Rogers 
Cc: Ingo Molnar 
Cc: James Clark 
Cc: Jan Kara 
Cc: Jann Horn 
Cc: Janosch Frank 
Cc: Jason Gunthorpe 
Cc: Jiri Olsa 
Cc: John Hubbard 
Cc: Joshua Hahn 
Cc: Kairui Song 
Cc: Kees Cook 
Cc: Kemeng Shi 
Cc: Lance Yang 
Cc: Liam R. Howlett 
Cc: Liviu Dudau 
Cc: Maarten Lankhorst 
Cc: Marc Rutland 
Cc: "Masami Hiramatsu (Google)" 
Cc: Matthew Auld 
Cc: Matthew Brost 
Cc: Matthew Wilcox (Oracle) 
Cc: Maxime Ripard 
Cc: Miaohe Lin 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Muchun Song 
Cc: Namhyung kim 
Cc: Naoya Horiguchi 
Cc: Nhat Pham 
Cc: Nico Pache 
Cc: Oleg Nesterov 
Cc: Oscar Salvador 
Cc: Pedro Falcato 
Cc: Peter Xu 
Cc: Peter Zijlstra 
Cc: Rakie Kim 
Cc: Rik van Riel 
Cc: Rodrigo Vivi 
Cc: Ryan Roberts 
Cc: Steven Price 
Cc: Suren Baghdasaryan 
Cc: Sven Schnelle 
Cc: Thomas Hellström 
Cc: Thomas Zimemrmann 
Cc: Vasily Gorbik 
Cc: Vlastimil Babka 
Cc: xu xin 
Cc: Zi Yan 
Signed-off-by: Andrew Morton

mm/vma: introduce VMA anon page offset field and add helpers

2026-08-25T01:42:49+00:00

Patch series "mm/rmap: index MAP_PRIVATE file-backed folios by anonymous
pgoff", v5.

In memory management we've managed to manufacture a great deal of
confusion around the concept of anonymous memory.  We have:

1. 'Pure anon' memory - anonymous VMAs whose folios are anonymous and
   swap-backed (thus for reclaim purposes, treated as anonymous). These are
   simple enough.

2. shmem - file-backed VMAs, file-backed folios (from rmap perspective) so
   present in the page cache and mapped by an address_space object, but
   whose folios are also swap-backed (thus treated as anonymous for reclaim
   purposes).

3. MAP_PRIVATE-mapped /dev/zero - a strange beast whose VMAs have
   vma->vm_file set, but which clears vma->vm_ops to satisfy
   vma_is_anonymous(), resulting in VMAs that were mmap()'d referencing a
   file, but are in every other sense anonymous, including the folios.

4. Other MAP_PRIVATE-file backed mappings - These possess file-backed VMAs
   and have file-backed folios until CoW'd, at which point those CoW'd
   folios are anonymous.

This series fixes issue 3.

In order for us to traverse VMAs using the reverse mapping, we require two
fields - folio->mapping and folio->index.  The first tells the rmap code
where to look for VMAs, and the second tells it at which offset the folio
starts within the referenced object.

For anonymous folios, folio->mapping points at an anon_vma object.  For
file-backed folios, it points at an address_space.  And:

* For file-backed folios folio->index is simply the page offset of the start
  of the folio within the file.

* For anonymous folios belonging to pure anon mappings, folio->index is
  equal to the anonymous page offset of the folio.

* For anonymous folios belonging to file-backed mappings (i.e. CoW'd folios
  of a MAP_PRIVATE file-backed mapping), folio->index is equal to the file
  page offset.

This series establishes a new anonymous page offset property of VMAs to
allow us to map anonymous folios at their anonymous page offset,
consistent with pure anon.

The purpose of doing so is to lay the foundations for the scalable CoW
work.  This is necessary because scalable CoW looks in the maple tree for
the VMA located at folio->index << PAGE_SHIFT, before falling back to
looking up tracked remaps if necessary.

The MAP_PRIVATE file-backed case means that folio indices will very often
conflict with one another and this remap tracking becomes substantially
more contended, and of course the fast path can never be used.

This also makes it possible, in future, to unshare anonymously mapped
folios with deep fork hierarchies on remap, eliminating the need for remap
tracking in the vast majority of cases.

Similar to page offset of pure anonymous VMAs, we update the anonymous
page offset of unfaulted file-backed VMAs on remap, but do not once CoW'd
(i.e.  vma->anon_vma is non-NULL).

Overall, there is little impact on mergeability, which remains exactly the
same for pure anonymous and shared file-backed mappings, with the only
impact being on MAP_PRIVATE-mapped file-backed mappings, which must now
match on anonymous page offset as well as file page offset to be merged.

To fail to merge like this would require CoW'ing the mapping, then finding
another VMA with identical file and compatible page offset to remap next
to.

This is therefore very much an edge case that should have very little
impact (and which scalable CoW may very well address in any case).


This patch (of 16):

Establish fields in vm_area_struct to store the anonymous page offset of
VMAs.

Initially, the anonymous page offset of a VMA is vma->vm_start >>
PAGE_SHIFT.

When a VMA is remapped to new_address its anonymous page offset is either
updated to new_address >> PAGE_SHIFT if unfaulted or, if faulted, remains
equal to the anonymous page offset it had when first faulted.

Currently, anonymous folios belonging to CoW'd MAP_PRIVATE-mapped
file-backed VMAs are tracked by their file offsets.  By adding anonymous
offset as a property of VMAs, we can now track them by their anonymous
page offset instead.

By tracking this, we provide the means by which to eliminate this
inconsistency, and more importantly lay the foundations for future work
for the scalable CoW anonymous rmap rework.

This patch simply adds the fields and some simple helpers.  Subsequent
patches will update mm code to make use of these fields correctly.

The fields chosen are packed in the VMA such that, for 64-bit kernel
builds, no additional space is taken up.

The first field is present on cacheline 0 containing key VMA fields, and
the second on cacheline 3, which contains file-backed reverse mapping
fields.

Given the relative time spent accessing reverse mapping fields as well as
updating them, there shouldn't be any performance impact here from false
sharing.

Update the VMA userland tests to account for this change.

No callsites are updated yet, so no functional change intended.

Link: https://lore.kernel.org/20260813-b4-scalable-cow-virt-pgoff-v5-0-c21581c0c3c8@kernel.org
Link: https://lore.kernel.org/20260813-b4-scalable-cow-virt-pgoff-v5-1-c21581c0c3c8@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) 
Acked-by: David Hildenbrand (Arm) 
Reviewed-by: Gregory Price (Meta) 
Reviewed-by: Xu Xin 
Cc: Adrian Hunter 
Cc: Alexander Deucher 
Cc: Alexander Gordeev 
Cc: Alexander Shishkin 
Cc: Alistair Popple 
Cc: Arnaldo Carvalho de Melo 
Cc: Arnd Bergmann 
Cc: Baolin Wang 
Cc: Baoquan He 
Cc: Barry Song 
Cc: Boris Brezillon 
Cc: Byungchul Park 
Cc: Chengming Zhou 
Cc: Chris Li 
Cc: Christan König 
Cc: Christian Borntraeger 
Cc: Claudio Imbrenda 
Cc: Dave Airlie 
Cc: Dev Jain 
Cc: Gerald Schaefer 
Cc: Greg Kroah-Hartman 
Cc: Harry Yoo 
Cc: Heiko Carstens 
Cc: Huang Ray 
Cc: "Huang, Ying" 
Cc: Ian Rogers 
Cc: Ingo Molnar 
Cc: James Clark 
Cc: Jan Kara 
Cc: Jann Horn 
Cc: Janosch Frank 
Cc: Jason Gunthorpe 
Cc: Jiri Olsa 
Cc: John Hubbard 
Cc: Joshua Hahn 
Cc: Kairui Song 
Cc: Kees Cook 
Cc: Kemeng Shi 
Cc: Lance Yang 
Cc: Liam R. Howlett 
Cc: Liviu Dudau 
Cc: Maarten Lankhorst 
Cc: Marc Rutland 
Cc: "Masami Hiramatsu (Google)" 
Cc: Matthew Auld 
Cc: Matthew Brost 
Cc: Matthew Wilcox (Oracle) 
Cc: Maxime Ripard 
Cc: Miaohe Lin 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Muchun Song 
Cc: Namhyung kim 
Cc: Naoya Horiguchi 
Cc: Nhat Pham 
Cc: Nico Pache 
Cc: Oleg Nesterov 
Cc: Oscar Salvador 
Cc: Pedro Falcato 
Cc: Peter Xu 
Cc: Peter Zijlstra 
Cc: Rakie Kim 
Cc: Rik van Riel 
Cc: Rodrigo Vivi 
Cc: Ryan Roberts 
Cc: Steven Price 
Cc: Suren Baghdasaryan 
Cc: Sven Schnelle 
Cc: Thomas Hellström 
Cc: Thomas Zimemrmann 
Cc: Vasily Gorbik 
Cc: Vlastimil Babka 
Cc: xu xin 
Cc: Zi Yan 
Signed-off-by: Andrew Morton

mm/vma: update create_init_stack_vma() to use vma_flags_t

2026-08-07T01:57:03+00:00

Replace use of the legacy vm_flags_t flags with vma_flags_t values in
create_init_stack_vma().

As part of this change we add VMA_STACK_EARLY and VMA_STACK_INCOMPLETE
vma_flags_t defines, and slightly rework create_init_stack_vma() for
clarity.

No functional change intended.

Link: https://lore.kernel.org/20260711-b4-vma-flags-mm-v2-9-0fa2357d5431@kernel.org
Signed-off-by: Lorenzo Stoakes 
Reviewed-by: Zi Yan 
Reviewed-by: Lance Yang 
Reviewed-by: Vlastimil Babka (SUSE) 
Cc: Baolin Wang 
Cc: Barry Song 
Cc: Christian Brauner 
Cc: Dave Airlie 
Cc: David Hildenbrand 
Cc: Dev Jain 
Cc: Jani Nikula 
Cc: Jan Kara 
Cc: Jann Horn 
Cc: Mike Rapoport 
Cc: Muchun Song 
Cc: Nico Pache 
Cc: Oscar Salvador 
Cc: Pedro Falcato 
Cc: Suren Baghdasaryan 
Cc: Thomas Zimmermann 
Signed-off-by: Andrew Morton

mm: introduce vma_get_page_prot() and use it

2026-08-07T01:57:03+00:00

There's a large number of vm_get_page_prot(vma->vm_flags) invocations. 
Make life easier by introducing vma_get_page_prot() parameterised by the
VMA.

This also makes converting vm_get_page_prot() to vma_flags_t easier.

Also update the userland VMA tests to reflect the change.

No functional change intended.

Link: https://lore.kernel.org/20260711-b4-vma-flags-mm-v2-8-0fa2357d5431@kernel.org
Signed-off-by: Lorenzo Stoakes 
Acked-by: Zi Yan 
Acked-by: Jani Nikula  # for i915
Reviewed-by: Thomas Zimmermann 	[DRM]
Reviewed-by: Vlastimil Babka (SUSE) 
Cc: Baolin Wang 
Cc: Barry Song 
Cc: Christian Brauner 
Cc: Dave Airlie 
Cc: David Hildenbrand 
Cc: Dev Jain 
Cc: Jan Kara 
Cc: Jann Horn 
Cc: Lance Yang 
Cc: Mike Rapoport 
Cc: Muchun Song 
Cc: Nico Pache 
Cc: Oscar Salvador 
Cc: Pedro Falcato 
Cc: Suren Baghdasaryan 
Signed-off-by: Andrew Morton