The patch titled
Subject: mm: mlock: update mlock_pte_range to handle large folio
has been added to the -mm mm-unstable branch. Its filename is
mm-mlock-update-mlock_pte_range-to-handle-large-folio.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mlock-update-mlock_pte_range-to-handle-large-folio.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Yin Fengwei <fengwei.yin@xxxxxxxxx>
Subject: mm: mlock: update mlock_pte_range to handle large folio
Date: Mon, 18 Sep 2023 15:33:18 +0800
Current kernel only lock base size folio during mlock syscall.
Add large folio support with following rules:
- Only mlock large folio when it's in VM_LOCKED VMA range
and fully mapped to page table.
fully mapped folio is required as if folio is not fully
mapped to a VM_LOCKED VMA, if system is in memory pressure,
page reclaim is allowed to pick up this folio, split it
and reclaim the pages which are not in VM_LOCKED VMA.
- munlock will apply to the large folio which is in VMA range
or cross the VMA boundary.
This is required to handle the case that the large folio is
mlocked, later the VMA is split in the middle of large folio.
Link: https://lkml.kernel.org/r/20230918073318.1181104-4-fengwei.yin@xxxxxxxxx
Signed-off-by: Yin Fengwei <fengwei.yin@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mlock.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 64 insertions(+), 2 deletions(-)
--- a/mm/mlock.c~mm-mlock-update-mlock_pte_range-to-handle-large-folio
+++ a/mm/mlock.c
@@ -305,6 +305,58 @@ void munlock_folio(struct folio *folio)
local_unlock(&mlock_fbatch.lock);
}
+static inline unsigned int folio_mlock_step(struct folio *folio,
+ pte_t *pte, unsigned long addr, unsigned long end)
+{
+ unsigned int count, i, nr = folio_nr_pages(folio);
+ unsigned long pfn = folio_pfn(folio);
+ pte_t ptent = ptep_get(pte);
+
+ if (!folio_test_large(folio))
+ return 1;
+
+ count = pfn + nr - pte_pfn(ptent);
+ count = min_t(unsigned int, count, (end - addr) >> PAGE_SHIFT);
+
+ for (i = 0; i < count; i++, pte++) {
+ pte_t entry = ptep_get(pte);
+
+ if (!pte_present(entry))
+ break;
+ if (pte_pfn(entry) - pfn >= nr)
+ break;
+ }
+
+ return i;
+}
+
+static inline bool allow_mlock_munlock(struct folio *folio,
+ struct vm_area_struct *vma, unsigned long start,
+ unsigned long end, unsigned int step)
+{
+ /*
+ * For unlock, allow munlock large folio which is partially
+ * mapped to VMA. As it's possible that large folio is
+ * mlocked and VMA is split later.
+ *
+ * During memory pressure, such kind of large folio can
+ * be split. And the pages are not in VM_LOCKed VMA
+ * can be reclaimed.
+ */
+ if (!(vma->vm_flags & VM_LOCKED))
+ return true;
+
+ /* folio not in range [start, end), skip mlock */
+ if (!folio_within_range(folio, vma, start, end))
+ return false;
+
+ /* folio is not fully mapped, skip mlock */
+ if (step != folio_nr_pages(folio))
+ return false;
+
+ return true;
+}
+
static int mlock_pte_range(pmd_t *pmd, unsigned long addr,
unsigned long end, struct mm_walk *walk)
@@ -314,6 +366,8 @@ static int mlock_pte_range(pmd_t *pmd, u
pte_t *start_pte, *pte;
pte_t ptent;
struct folio *folio;
+ unsigned int step = 1;
+ unsigned long start = addr;
ptl = pmd_trans_huge_lock(pmd, vma);
if (ptl) {
@@ -334,6 +388,7 @@ static int mlock_pte_range(pmd_t *pmd, u
walk->action = ACTION_AGAIN;
return 0;
}
+
for (pte = start_pte; addr != end; pte++, addr += PAGE_SIZE) {
ptent = ptep_get(pte);
if (!pte_present(ptent))
@@ -341,12 +396,19 @@ static int mlock_pte_range(pmd_t *pmd, u
folio = vm_normal_folio(vma, addr, ptent);
if (!folio || folio_is_zone_device(folio))
continue;
- if (folio_test_large(folio))
- continue;
+
+ step = folio_mlock_step(folio, pte, addr, end);
+ if (!allow_mlock_munlock(folio, vma, start, end, step))
+ goto next_entry;
+
if (vma->vm_flags & VM_LOCKED)
mlock_folio(folio);
else
munlock_folio(folio);
+
+next_entry:
+ pte += step - 1;
+ addr += (step - 1) << PAGE_SHIFT;
}
pte_unmap(start_pte);
out:
_
Patches currently in -mm which might be from fengwei.yin@xxxxxxxxx are
filemap-add-filemap_map_order0_folio-to-handle-order0-folio.patch
mm-add-functions-folio_in_range-and-folio_within_vma.patch
mm-handle-large-folio-when-large-folio-in-vm_locked-vma-range.patch
mm-mlock-update-mlock_pte_range-to-handle-large-folio.patch
