* [PATCH v3 1/5] mm/rmap: convert page -> folio for hwpoison checks
2026-07-13 5:00 [PATCH v3 0/5] mm/rmap: Refactor try_to_unmap_one Dev Jain
@ 2026-07-13 5:00 ` Dev Jain
2026-07-13 5:00 ` [PATCH v3 2/5] mm/rmap: Add try_to_unmap_hugetlb_one Dev Jain
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Dev Jain @ 2026-07-13 5:00 UTC (permalink / raw)
To: akpm, david, ljs, muchun.song, osalvador
Cc: Dev Jain, riel, liam, vbabka, harry, jannh, lance.yang, linux-mm,
linux-kernel, ryan.roberts, anshuman.khandual
try_to_unmap() receives hugetlb folios only from the hwpoison path.
hugetlb_update_hwpoison() sets the hugetlb folio's head-page
hwpoison bit, and page_vma_mapped_walk() reports the hugetlb mapping at
the head PFN, so the previous PageHWPoison(subpage) check happened to
work for hugetlb.
For non-hugetlb folios, unmap_poisoned_folio() currently rejects large
folios before calling try_to_unmap(). Hence it is always the case that
if try_to_unmap_one() handles an hwpoisoned folio, then the head page is
marked with the poison bit.
Therefore, convert the poisoned subpage checks to folio_test_hwpoison().
No functional change intended, except that, while at it,
convert VM_BUG_* to VM_WARN_*.
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Dev Jain <dev.jain@arm.com>
---
mm/rmap.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index 26166a6b8cb9b..2b74668f356d6 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -2122,10 +2122,11 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
bool anon = folio_test_anon(folio);
/*
- * The try_to_unmap() is only passed a hugetlb page
- * in the case where the hugetlb page is poisoned.
+ * The try_to_unmap() is only passed a hugetlb folio
+ * in the case where the hugetlb folio contains a
+ * poisoned page.
*/
- VM_BUG_ON_PAGE(!PageHWPoison(subpage), subpage);
+ VM_WARN_ON_FOLIO(!folio_test_hwpoison(folio), folio);
/*
* huge_pmd_unshare may unmap an entire PMD page.
* There is no way of knowing exactly which PMDs may
@@ -2204,7 +2205,11 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
/* Update high watermark before we lower rss */
update_hiwater_rss(mm);
- if (PageHWPoison(subpage) && (flags & TTU_HWPOISON)) {
+ /*
+ * With TTU_HWPOISON, we only expect small folios or hugetlb
+ * folios here for now.
+ */
+ if (folio_test_hwpoison(folio) && (flags & TTU_HWPOISON)) {
pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
if (folio_test_hugetlb(folio)) {
hugetlb_count_sub(folio_nr_pages(folio), mm);
--
2.43.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v3 2/5] mm/rmap: Add try_to_unmap_hugetlb_one
2026-07-13 5:00 [PATCH v3 0/5] mm/rmap: Refactor try_to_unmap_one Dev Jain
2026-07-13 5:00 ` [PATCH v3 1/5] mm/rmap: convert page -> folio for hwpoison checks Dev Jain
@ 2026-07-13 5:00 ` Dev Jain
2026-07-13 5:00 ` [PATCH v3 3/5] mm/rmap: refactor some code around lazyfree folio unmapping Dev Jain
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Dev Jain @ 2026-07-13 5:00 UTC (permalink / raw)
To: akpm, david, ljs, muchun.song, osalvador
Cc: Dev Jain, riel, liam, vbabka, harry, jannh, lance.yang, linux-mm,
linux-kernel, ryan.roberts, anshuman.khandual
Simplify try_to_unmap_one() by separating the hugetlb parts into
try_to_unmap_hugetlb_one().
To understand the correctness of the refactoring, the following points
are noted:
1. try_to_unmap() is called for hugetlb folios only when they are
hwpoisoned.
2. A hugetlb VMA cannot be mlocked.
3. page_vma_mapped_walk() returns at most one hugetlb mapping in a VMA,
and that mapping points at the head PFN.
4. We won't ever process a softleaf entry that encodes a hugetlb folio;
hugetlb folios are never swapped out, migration entries will be
skipped (PVMW_MIGRATION not passed), and device-exclusive does not
work for hugetlb.
5. The hwpoison entry is constructed from the poisoned folio, just as in
the pre-refactor code. Any previous uffd-wp state is deliberately not
preserved for the hwpoison entry.
6. TTU_HWPOISON is always present; for it to not be present, either the
folio has to be in swapcache, or mapping_can_writeback() is true (see
unmap_poisoned_folio), none of which is true for hugetlb folios.
7. Hugetlb uses separate counters from normal rss counters, therefore
update_highwater_rss() need not be called.
While at it:
- Change VM_BUG_* to VM_WARN_*.
- Do not declare variables which are only used once.
- Constify some variables.
- Add some more VM_WARN_* to assert some invariants.
Except the above 4 points, no functional change intended.
Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Dev Jain <dev.jain@arm.com>
---
include/linux/hugetlb.h | 1 +
mm/rmap.c | 183 +++++++++++++++++++++-------------------
2 files changed, 98 insertions(+), 86 deletions(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 4115076e4922a..bf7e163e3779d 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -1271,6 +1271,7 @@ static inline void hugetlb_count_sub(long l, struct mm_struct *mm)
}
pte_t huge_ptep_get(struct mm_struct *mm, unsigned long addr, pte_t *ptep);
+unsigned long huge_pte_dirty(pte_t pte);
static inline pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
unsigned long addr, pte_t *ptep)
diff --git a/mm/rmap.c b/mm/rmap.c
index 2b74668f356d6..7720c49ada4c3 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1978,6 +1978,96 @@ static inline unsigned int folio_unmap_pte_batch(struct folio *folio,
FPB_RESPECT_WRITE | FPB_RESPECT_SOFT_DIRTY);
}
+static bool try_to_unmap_hugetlb_one(struct folio *folio,
+ struct vm_area_struct *vma, unsigned long address, void *arg)
+{
+ DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
+ const unsigned long hsz = huge_page_size(hstate_vma(vma));
+ const enum ttu_flags flags = (enum ttu_flags)(long)arg;
+ struct mm_struct *mm = vma->vm_mm;
+ struct mmu_notifier_range range;
+ bool ret = true;
+ pte_t pteval;
+
+ /*
+ * The try_to_unmap() is only passed a hugetlb folio in the case
+ * where the hugetlb folio is poisoned.
+ */
+ VM_WARN_ON_FOLIO(!folio_test_hwpoison(folio), folio);
+ VM_WARN_ON_ONCE(!(flags & TTU_HWPOISON));
+
+ range.end = vma_address_end(&pvmw);
+ mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
+ address, range.end);
+ adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end);
+ mmu_notifier_invalidate_range_start(&range);
+
+ /* There is only a single mapping in a VMA. */
+ if (!page_vma_mapped_walk(&pvmw))
+ goto range_end;
+
+ VM_WARN_ON_ONCE(address != pvmw.address);
+
+ pteval = huge_ptep_get(mm, address, pvmw.pte);
+ VM_WARN_ON_ONCE(!pte_present(pteval));
+ VM_WARN_ON_ONCE(pte_pfn(pteval) != folio_pfn(folio));
+
+ /*
+ * huge_pmd_unshare may unmap an entire PMD page. There is no way of
+ * knowing exactly which PMDs may be cached for this mm, so we must
+ * flush them all. start/end were already adjusted above to cover this
+ * range.
+ */
+ flush_cache_range(vma, range.start, range.end);
+
+ /*
+ * To call huge_pmd_unshare, i_mmap_rwsem must be held in write mode.
+ * Caller needs to explicitly do this outside rmap routines.
+ *
+ * We also must hold hugetlb vma_lock in write mode. Lock order dictates
+ * acquiring vma_lock BEFORE i_mmap_rwsem. We can only try lock here and
+ * fail if unsuccessful.
+ */
+ if (!folio_test_anon(folio)) {
+ struct mmu_gather tlb;
+
+ VM_WARN_ON(!(flags & TTU_RMAP_LOCKED));
+ if (!hugetlb_vma_trylock_write(vma)) {
+ ret = false;
+ goto walk_done;
+ }
+
+ tlb_gather_mmu_vma(&tlb, vma);
+ if (huge_pmd_unshare(&tlb, vma, address, pvmw.pte)) {
+ hugetlb_vma_unlock_write(vma);
+ huge_pmd_unshare_flush(&tlb, vma);
+ tlb_finish_mmu(&tlb);
+ /*
+ * The PMD table was unmapped, consequently unmapping
+ * the folio.
+ */
+ goto walk_done;
+ }
+ hugetlb_vma_unlock_write(vma);
+ tlb_finish_mmu(&tlb);
+ }
+ pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
+ if (huge_pte_dirty(pteval))
+ folio_mark_dirty(folio);
+
+ pteval = swp_entry_to_pte(make_hwpoison_entry(folio_page(folio, 0)));
+ hugetlb_count_sub(folio_nr_pages(folio), mm);
+ set_huge_pte_at(mm, address, pvmw.pte, pteval, hsz);
+ hugetlb_remove_rmap(folio);
+ folio_put_refs(folio, 1);
+
+walk_done:
+ page_vma_mapped_walk_done(&pvmw);
+range_end:
+ mmu_notifier_invalidate_range_end(&range);
+ return ret;
+}
+
/*
* @arg: enum ttu_flags will be passed to this argument
*/
@@ -1993,7 +2083,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
enum ttu_flags flags = (enum ttu_flags)(long)arg;
unsigned long nr_pages = 1, end_addr;
unsigned long pfn;
- unsigned long hsz = 0;
int ptes = 0;
/*
@@ -2007,8 +2096,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
/*
* For THP, we have to assume the worse case ie pmd for invalidation.
- * For hugetlb, it could be much worse if we need to do pud
- * invalidation in the case of pmd sharing.
*
* Note that the folio can not be freed in this function as call of
* try_to_unmap() must hold a reference on the folio.
@@ -2016,17 +2103,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
range.end = vma_address_end(&pvmw);
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
address, range.end);
- if (folio_test_hugetlb(folio)) {
- /*
- * If sharing is possible, start and end will be adjusted
- * accordingly.
- */
- adjust_range_if_pmd_sharing_possible(vma, &range.start,
- &range.end);
-
- /* We need the huge page size for set_huge_pte_at() */
- hsz = huge_page_size(hstate_vma(vma));
- }
mmu_notifier_invalidate_range_start(&range);
while (page_vma_mapped_walk(&pvmw)) {
@@ -2111,66 +2187,13 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
const softleaf_t entry = softleaf_from_pte(pteval);
pfn = softleaf_to_pfn(entry);
- VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);
}
subpage = folio_page(folio, pfn - folio_pfn(folio));
anon_exclusive = folio_test_anon(folio) &&
PageAnonExclusive(subpage);
- if (folio_test_hugetlb(folio)) {
- bool anon = folio_test_anon(folio);
-
- /*
- * The try_to_unmap() is only passed a hugetlb folio
- * in the case where the hugetlb folio contains a
- * poisoned page.
- */
- VM_WARN_ON_FOLIO(!folio_test_hwpoison(folio), folio);
- /*
- * huge_pmd_unshare may unmap an entire PMD page.
- * There is no way of knowing exactly which PMDs may
- * be cached for this mm, so we must flush them all.
- * start/end were already adjusted above to cover this
- * range.
- */
- flush_cache_range(vma, range.start, range.end);
-
- /*
- * To call huge_pmd_unshare, i_mmap_rwsem must be
- * held in write mode. Caller needs to explicitly
- * do this outside rmap routines.
- *
- * We also must hold hugetlb vma_lock in write mode.
- * Lock order dictates acquiring vma_lock BEFORE
- * i_mmap_rwsem. We can only try lock here and fail
- * if unsuccessful.
- */
- if (!anon) {
- struct mmu_gather tlb;
-
- VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
- if (!hugetlb_vma_trylock_write(vma))
- goto walk_abort;
-
- tlb_gather_mmu_vma(&tlb, vma);
- if (huge_pmd_unshare(&tlb, vma, address, pvmw.pte)) {
- hugetlb_vma_unlock_write(vma);
- huge_pmd_unshare_flush(&tlb, vma);
- tlb_finish_mmu(&tlb);
- /*
- * The PMD table was unmapped,
- * consequently unmapping the folio.
- */
- goto walk_done;
- }
- hugetlb_vma_unlock_write(vma);
- tlb_finish_mmu(&tlb);
- }
- pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
- if (pte_dirty(pteval))
- folio_mark_dirty(folio);
- } else if (likely(pte_present(pteval))) {
+ if (likely(pte_present(pteval))) {
nr_pages = folio_unmap_pte_batch(folio, &pvmw, flags, pteval);
end_addr = address + nr_pages * PAGE_SIZE;
flush_cache_range(vma, address, end_addr);
@@ -2205,20 +2228,11 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
/* Update high watermark before we lower rss */
update_hiwater_rss(mm);
- /*
- * With TTU_HWPOISON, we only expect small folios or hugetlb
- * folios here for now.
- */
+ /* With TTU_HWPOISON, we only expect small folios here. */
if (folio_test_hwpoison(folio) && (flags & TTU_HWPOISON)) {
pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
- if (folio_test_hugetlb(folio)) {
- hugetlb_count_sub(folio_nr_pages(folio), mm);
- set_huge_pte_at(mm, address, pvmw.pte, pteval,
- hsz);
- } else {
- dec_mm_counter(mm, mm_counter(folio));
- set_pte_at(mm, address, pvmw.pte, pteval);
- }
+ dec_mm_counter(mm, mm_counter(folio));
+ set_pte_at(mm, address, pvmw.pte, pteval);
} else if (likely(pte_present(pteval)) && pte_unused(pteval) &&
!userfaultfd_armed(vma)) {
/*
@@ -2346,11 +2360,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
add_mm_counter(mm, mm_counter_file(folio), -nr_pages);
}
discard:
- if (unlikely(folio_test_hugetlb(folio))) {
- hugetlb_remove_rmap(folio);
- } else {
- folio_remove_rmap_ptes(folio, subpage, nr_pages, vma);
- }
+ folio_remove_rmap_ptes(folio, subpage, nr_pages, vma);
if (vma->vm_flags & VM_LOCKED)
mlock_drain_local();
folio_put_refs(folio, nr_pages);
@@ -2398,7 +2408,8 @@ static int folio_not_mapped(struct folio *folio)
void try_to_unmap(struct folio *folio, enum ttu_flags flags)
{
struct rmap_walk_control rwc = {
- .rmap_one = try_to_unmap_one,
+ .rmap_one = folio_test_hugetlb(folio) ?
+ try_to_unmap_hugetlb_one : try_to_unmap_one,
.arg = (void *)flags,
.done = folio_not_mapped,
.anon_lock = folio_lock_anon_vma_read,
--
2.43.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v3 3/5] mm/rmap: refactor some code around lazyfree folio unmapping
2026-07-13 5:00 [PATCH v3 0/5] mm/rmap: Refactor try_to_unmap_one Dev Jain
2026-07-13 5:00 ` [PATCH v3 1/5] mm/rmap: convert page -> folio for hwpoison checks Dev Jain
2026-07-13 5:00 ` [PATCH v3 2/5] mm/rmap: Add try_to_unmap_hugetlb_one Dev Jain
@ 2026-07-13 5:00 ` Dev Jain
2026-07-13 5:00 ` [PATCH v3 4/5] mm/rmap: refactor anon folio unmap in try_to_unmap_one Dev Jain
2026-07-13 5:00 ` [PATCH v3 5/5] mm/rmap: add anon folio unmap dispatcher Dev Jain
4 siblings, 0 replies; 6+ messages in thread
From: Dev Jain @ 2026-07-13 5:00 UTC (permalink / raw)
To: akpm, david, ljs, muchun.song, osalvador
Cc: Dev Jain, riel, liam, vbabka, harry, jannh, lance.yang, linux-mm,
linux-kernel, ryan.roberts, anshuman.khandual
For lazyfree folio unmapping, after clearing the ptes we must abort the
operation if the folio got dirtied or it has unexpected references.
Refactor this logic into a function which will return whether we need
to abort or not.
If we abort, we restore the ptes and bail out of try_to_unmap_one.
Otherwise adjust the rss stats of the mm and jump to a label.
Also rename that label from "discard" to "finish_unmap"; the former
is appropriate in the lazyfree context, but the code following the label
is executed for other successful unmap code paths too, so 'discard' does
not sound correct for them.
No functional change intended.
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Dev Jain <dev.jain@arm.com>
---
mm/rmap.c | 87 ++++++++++++++++++++++++++++++-------------------------
1 file changed, 48 insertions(+), 39 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index 7720c49ada4c3..4465c88ddb77b 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -2068,6 +2068,50 @@ static bool try_to_unmap_hugetlb_one(struct folio *folio,
return ret;
}
+static bool ttu_anon_lazyfree_folio(struct vm_area_struct *vma,
+ struct folio *folio, unsigned long nr_pages)
+{
+ int ref_count, map_count;
+
+ /*
+ * Synchronize with gup_pte_range():
+ * - clear PTE; barrier; read refcount
+ * - inc refcount; barrier; read PTE
+ */
+ smp_mb();
+
+ ref_count = folio_ref_count(folio);
+ map_count = folio_mapcount(folio);
+
+ /*
+ * Order reads for page refcount and dirty flag
+ * (see comments in __remove_mapping()).
+ */
+ smp_rmb();
+
+ if (folio_test_dirty(folio) && !(vma->vm_flags & VM_DROPPABLE)) {
+ /*
+ * redirtied either using the page table or a previously
+ * obtained GUP reference.
+ */
+ folio_set_swapbacked(folio);
+ return false;
+ }
+
+ /*
+ * Additional references could be due to GUP or speculative lookups.
+ * GUP users must mark the folio dirty if there was a modification.
+ * This folio cannot be reclaimed right now either way, so act just
+ * like nothing happened. We'll come back here later and detect if the
+ * folio was dirtied when the additional reference is gone.
+ */
+ if (ref_count != 1 + map_count)
+ return false;
+
+ add_mm_counter(vma->vm_mm, MM_ANONPAGES, -nr_pages);
+ return true;
+}
+
/*
* @arg: enum ttu_flags will be passed to this argument
*/
@@ -2261,47 +2305,12 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
/* MADV_FREE page check */
if (!folio_test_swapbacked(folio)) {
- int ref_count, map_count;
-
- /*
- * Synchronize with gup_pte_range():
- * - clear PTE; barrier; read refcount
- * - inc refcount; barrier; read PTE
- */
- smp_mb();
-
- ref_count = folio_ref_count(folio);
- map_count = folio_mapcount(folio);
-
- /*
- * Order reads for page refcount and dirty flag
- * (see comments in __remove_mapping()).
- */
- smp_rmb();
-
- if (folio_test_dirty(folio) && !(vma->vm_flags & VM_DROPPABLE)) {
- /*
- * redirtied either using the page table or a previously
- * obtained GUP reference.
- */
- set_ptes(mm, address, pvmw.pte, pteval, nr_pages);
- folio_set_swapbacked(folio);
- goto walk_abort;
- } else if (ref_count != 1 + map_count) {
- /*
- * Additional reference. Could be a GUP reference or any
- * speculative reference. GUP users must mark the folio
- * dirty if there was a modification. This folio cannot be
- * reclaimed right now either way, so act just like nothing
- * happened.
- * We'll come back here later and detect if the folio was
- * dirtied when the additional reference is gone.
- */
+ if (!ttu_anon_lazyfree_folio(vma, folio,
+ nr_pages)) {
set_ptes(mm, address, pvmw.pte, pteval, nr_pages);
goto walk_abort;
}
- add_mm_counter(mm, MM_ANONPAGES, -nr_pages);
- goto discard;
+ goto finish_unmap;
}
if (folio_dup_swap(folio, subpage) < 0) {
@@ -2359,7 +2368,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
*/
add_mm_counter(mm, mm_counter_file(folio), -nr_pages);
}
-discard:
+finish_unmap:
folio_remove_rmap_ptes(folio, subpage, nr_pages, vma);
if (vma->vm_flags & VM_LOCKED)
mlock_drain_local();
--
2.43.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v3 4/5] mm/rmap: refactor anon folio unmap in try_to_unmap_one
2026-07-13 5:00 [PATCH v3 0/5] mm/rmap: Refactor try_to_unmap_one Dev Jain
` (2 preceding siblings ...)
2026-07-13 5:00 ` [PATCH v3 3/5] mm/rmap: refactor some code around lazyfree folio unmapping Dev Jain
@ 2026-07-13 5:00 ` Dev Jain
2026-07-13 5:00 ` [PATCH v3 5/5] mm/rmap: add anon folio unmap dispatcher Dev Jain
4 siblings, 0 replies; 6+ messages in thread
From: Dev Jain @ 2026-07-13 5:00 UTC (permalink / raw)
To: akpm, david, ljs, muchun.song, osalvador
Cc: Dev Jain, riel, liam, vbabka, harry, jannh, lance.yang, linux-mm,
linux-kernel, ryan.roberts, anshuman.khandual
Refactor anonymous swapbacked folio unmap to ttu_anon_swapbacked_folio().
While at it, rename the remaining subpage variables to page; folios have
pages, not subpages.
No functional change intended.
Signed-off-by: Dev Jain <dev.jain@arm.com>
---
mm/rmap.c | 115 ++++++++++++++++++++++++++++++++----------------------
1 file changed, 68 insertions(+), 47 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index 4465c88ddb77b..2c910d4575981 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -2112,6 +2112,66 @@ static bool ttu_anon_lazyfree_folio(struct vm_area_struct *vma,
return true;
}
+static pte_t swp_pte_prepare(swp_entry_t entry, pte_t old_pte,
+ bool anon_exclusive)
+{
+ pte_t swp_pte = swp_entry_to_pte(entry);
+
+ if (anon_exclusive)
+ swp_pte = pte_swp_mkexclusive(swp_pte);
+
+ if (likely(pte_present(old_pte))) {
+ if (pte_soft_dirty(old_pte))
+ swp_pte = pte_swp_mksoft_dirty(swp_pte);
+ if (pte_uffd(old_pte))
+ swp_pte = pte_swp_mkuffd(swp_pte);
+ } else {
+ /* Device-exclusive entry */
+ if (pte_swp_soft_dirty(old_pte))
+ swp_pte = pte_swp_mksoft_dirty(swp_pte);
+ if (pte_swp_uffd(old_pte))
+ swp_pte = pte_swp_mkuffd(swp_pte);
+ }
+
+ return swp_pte;
+}
+
+static bool ttu_anon_swapbacked_folio(struct vm_area_struct *vma,
+ struct folio *folio, struct page *page, unsigned long address,
+ pte_t *ptep, pte_t pteval)
+{
+ const bool anon_exclusive = folio_test_anon(folio) &&
+ PageAnonExclusive(page);
+ swp_entry_t entry = page_swap_entry(page);
+ struct mm_struct *mm = vma->vm_mm;
+
+ if (folio_dup_swap(folio, page) < 0)
+ return false;
+
+ /*
+ * arch_unmap_one() is expected to be a NOP on
+ * architectures where we could have PFN swap PTEs,
+ * so we'll not check/care.
+ */
+ if (arch_unmap_one(mm, vma, address, pteval) < 0) {
+ folio_put_swap(folio, page);
+ return false;
+ }
+
+ /* See folio_try_share_anon_rmap(): clear PTE first. */
+ if (anon_exclusive && folio_try_share_anon_rmap_pte(folio, page)) {
+ folio_put_swap(folio, page);
+ return false;
+ }
+
+ mm_prepare_for_swap_entries(mm);
+ dec_mm_counter(mm, MM_ANONPAGES);
+ inc_mm_counter(mm, MM_SWAPENTS);
+ set_pte_at(mm, address, ptep,
+ swp_pte_prepare(entry, pteval, anon_exclusive));
+ return true;
+}
+
/*
* @arg: enum ttu_flags will be passed to this argument
*/
@@ -2120,9 +2180,9 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
{
struct mm_struct *mm = vma->vm_mm;
DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
- bool anon_exclusive, ret = true;
+ bool ret = true;
pte_t pteval;
- struct page *subpage;
+ struct page *page;
struct mmu_notifier_range range;
enum ttu_flags flags = (enum ttu_flags)(long)arg;
unsigned long nr_pages = 1, end_addr;
@@ -2233,9 +2293,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
pfn = softleaf_to_pfn(entry);
}
- subpage = folio_page(folio, pfn - folio_pfn(folio));
- anon_exclusive = folio_test_anon(folio) &&
- PageAnonExclusive(subpage);
+ page = folio_page(folio, pfn - folio_pfn(folio));
if (likely(pte_present(pteval))) {
nr_pages = folio_unmap_pte_batch(folio, &pvmw, flags, pteval);
@@ -2274,7 +2332,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
/* With TTU_HWPOISON, we only expect small folios here. */
if (folio_test_hwpoison(folio) && (flags & TTU_HWPOISON)) {
- pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
+ pteval = swp_entry_to_pte(make_hwpoison_entry(page));
dec_mm_counter(mm, mm_counter(folio));
set_pte_at(mm, address, pvmw.pte, pteval);
} else if (likely(pte_present(pteval)) && pte_unused(pteval) &&
@@ -2291,8 +2349,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
*/
dec_mm_counter(mm, mm_counter(folio));
} else if (folio_test_anon(folio)) {
- swp_entry_t entry = page_swap_entry(subpage);
- pte_t swp_pte;
/*
* Store the swap location in the pte.
* See handle_pte_fault() ...
@@ -2313,47 +2369,12 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
goto finish_unmap;
}
- if (folio_dup_swap(folio, subpage) < 0) {
- set_pte_at(mm, address, pvmw.pte, pteval);
- goto walk_abort;
- }
-
- /*
- * arch_unmap_one() is expected to be a NOP on
- * architectures where we could have PFN swap PTEs,
- * so we'll not check/care.
- */
- if (arch_unmap_one(mm, vma, address, pteval) < 0) {
- folio_put_swap(folio, subpage);
- set_pte_at(mm, address, pvmw.pte, pteval);
- goto walk_abort;
- }
-
- /* See folio_try_share_anon_rmap(): clear PTE first. */
- if (anon_exclusive &&
- folio_try_share_anon_rmap_pte(folio, subpage)) {
- folio_put_swap(folio, subpage);
+ if (!ttu_anon_swapbacked_folio(vma, folio, page, address,
+ pvmw.pte, pteval)) {
set_pte_at(mm, address, pvmw.pte, pteval);
goto walk_abort;
}
- mm_prepare_for_swap_entries(mm);
- dec_mm_counter(mm, MM_ANONPAGES);
- inc_mm_counter(mm, MM_SWAPENTS);
- swp_pte = swp_entry_to_pte(entry);
- if (anon_exclusive)
- swp_pte = pte_swp_mkexclusive(swp_pte);
- if (likely(pte_present(pteval))) {
- if (pte_soft_dirty(pteval))
- swp_pte = pte_swp_mksoft_dirty(swp_pte);
- if (pte_uffd(pteval))
- swp_pte = pte_swp_mkuffd(swp_pte);
- } else {
- if (pte_swp_soft_dirty(pteval))
- swp_pte = pte_swp_mksoft_dirty(swp_pte);
- if (pte_swp_uffd(pteval))
- swp_pte = pte_swp_mkuffd(swp_pte);
- }
- set_pte_at(mm, address, pvmw.pte, swp_pte);
+ goto finish_unmap;
} else {
/*
* This is a locked file-backed folio,
@@ -2369,7 +2390,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
add_mm_counter(mm, mm_counter_file(folio), -nr_pages);
}
finish_unmap:
- folio_remove_rmap_ptes(folio, subpage, nr_pages, vma);
+ folio_remove_rmap_ptes(folio, page, nr_pages, vma);
if (vma->vm_flags & VM_LOCKED)
mlock_drain_local();
folio_put_refs(folio, nr_pages);
--
2.43.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v3 5/5] mm/rmap: add anon folio unmap dispatcher
2026-07-13 5:00 [PATCH v3 0/5] mm/rmap: Refactor try_to_unmap_one Dev Jain
` (3 preceding siblings ...)
2026-07-13 5:00 ` [PATCH v3 4/5] mm/rmap: refactor anon folio unmap in try_to_unmap_one Dev Jain
@ 2026-07-13 5:00 ` Dev Jain
4 siblings, 0 replies; 6+ messages in thread
From: Dev Jain @ 2026-07-13 5:00 UTC (permalink / raw)
To: akpm, david, ljs, muchun.song, osalvador
Cc: Dev Jain, riel, liam, vbabka, harry, jannh, lance.yang, linux-mm,
linux-kernel, ryan.roberts, anshuman.khandual
Add ttu_anon_folio() as the common entry point for anonymous folio
unmapping. It dispatches to the lazyfree or swapbacked helper as
appropriate.
Keep restoration of cleared PTEs in the caller, where the PTEs were
removed.
No functional change intended.
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Dev Jain <dev.jain@arm.com>
---
mm/rmap.c | 45 +++++++++++++++++++++++----------------------
1 file changed, 23 insertions(+), 22 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index 2c910d4575981..fe67ce6ceb5eb 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -2172,6 +2172,26 @@ static bool ttu_anon_swapbacked_folio(struct vm_area_struct *vma,
return true;
}
+static bool ttu_anon_folio(struct vm_area_struct *vma, struct folio *folio,
+ struct page *page, unsigned long address, pte_t *ptep,
+ pte_t pteval, unsigned long nr_pages)
+{
+ /*
+ * Store the swap location in the pte.
+ * See handle_pte_fault() ...
+ */
+ if (WARN_ON_ONCE(folio_test_swapbacked(folio) !=
+ folio_test_swapcache(folio)))
+ return false;
+
+ if (!folio_test_swapbacked(folio))
+ return ttu_anon_lazyfree_folio(vma, folio, nr_pages);
+
+ /* nr_pages > 1 not supported yet */
+ return ttu_anon_swapbacked_folio(vma, folio, page, address, ptep,
+ pteval);
+}
+
/*
* @arg: enum ttu_flags will be passed to this argument
*/
@@ -2349,31 +2369,12 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
*/
dec_mm_counter(mm, mm_counter(folio));
} else if (folio_test_anon(folio)) {
- /*
- * Store the swap location in the pte.
- * See handle_pte_fault() ...
- */
- if (unlikely(folio_test_swapbacked(folio) !=
- folio_test_swapcache(folio))) {
- WARN_ON_ONCE(1);
+ if (!ttu_anon_folio(vma, folio, page, address,
+ pvmw.pte, pteval, nr_pages)) {
+ set_ptes(mm, address, pvmw.pte, pteval, nr_pages);
goto walk_abort;
}
- /* MADV_FREE page check */
- if (!folio_test_swapbacked(folio)) {
- if (!ttu_anon_lazyfree_folio(vma, folio,
- nr_pages)) {
- set_ptes(mm, address, pvmw.pte, pteval, nr_pages);
- goto walk_abort;
- }
- goto finish_unmap;
- }
-
- if (!ttu_anon_swapbacked_folio(vma, folio, page, address,
- pvmw.pte, pteval)) {
- set_pte_at(mm, address, pvmw.pte, pteval);
- goto walk_abort;
- }
goto finish_unmap;
} else {
/*
--
2.43.0
^ permalink raw reply related [flat|nested] 6+ messages in thread