The patch titled
Subject: mm: introduce page_vma_mapped_walk()
has been removed from the -mm tree. Its filename was
mm-introduce-page_vma_mapped_walk.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: mm: introduce page_vma_mapped_walk()
Introduce a new interface to check if a page is mapped into a vma. It
aims to address shortcomings of page_check_address{,_transhuge}.
Existing interface is not able to handle PTE-mapped THPs: it only finds
the first PTE. The rest lefted unnoticed.
page_vma_mapped_walk() iterates over all possible mapping of the page in
the vma.
Link: http://lkml.kernel.org/r/20170129173858.45174-3-kirill.shutemov@xxxxxxxxxxxxxxx
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/rmap.h | 26 +++++
mm/Makefile | 6 -
mm/huge_memory.c | 9 +
mm/page_vma_mapped.c | 188 +++++++++++++++++++++++++++++++++++++++++
4 files changed, 224 insertions(+), 5 deletions(-)
diff -puN include/linux/rmap.h~mm-introduce-page_vma_mapped_walk include/linux/rmap.h
--- a/include/linux/rmap.h~mm-introduce-page_vma_mapped_walk
+++ a/include/linux/rmap.h
@@ -9,6 +9,7 @@
#include <linux/mm.h>
#include <linux/rwsem.h>
#include <linux/memcontrol.h>
+#include <linux/highmem.h>
/*
* The anon_vma heads a list of private "related" vmas, to scan if
@@ -232,6 +233,31 @@ static inline bool page_check_address_tr
}
#endif
+/* Avoid racy checks */
+#define PVMW_SYNC (1 << 0)
+/* Look for migarion entries rather than present PTEs */
+#define PVMW_MIGRATION (1 << 1)
+
+struct page_vma_mapped_walk {
+ struct page *page;
+ struct vm_area_struct *vma;
+ unsigned long address;
+ pmd_t *pmd;
+ pte_t *pte;
+ spinlock_t *ptl;
+ unsigned int flags;
+};
+
+static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
+{
+ if (pvmw->pte)
+ pte_unmap(pvmw->pte);
+ if (pvmw->ptl)
+ spin_unlock(pvmw->ptl);
+}
+
+bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
+
/*
* Used by swapoff to help locate where page is expected in vma.
*/
diff -puN mm/Makefile~mm-introduce-page_vma_mapped_walk mm/Makefile
--- a/mm/Makefile~mm-introduce-page_vma_mapped_walk
+++ a/mm/Makefile
@@ -23,8 +23,10 @@ KCOV_INSTRUMENT_vmstat.o := n
mmu-y := nommu.o
mmu-$(CONFIG_MMU) := gup.o highmem.o memory.o mincore.o \
- mlock.o mmap.o mprotect.o mremap.o msync.o rmap.o \
- vmalloc.o pagewalk.o pgtable-generic.o
+ mlock.o mmap.o mprotect.o mremap.o msync.o \
+ page_vma_mapped.o pagewalk.o pgtable-generic.o \
+ rmap.o vmalloc.o
+
ifdef CONFIG_CROSS_MEMORY_ATTACH
mmu-$(CONFIG_MMU) += process_vm_access.o
diff -puN mm/huge_memory.c~mm-introduce-page_vma_mapped_walk mm/huge_memory.c
--- a/mm/huge_memory.c~mm-introduce-page_vma_mapped_walk
+++ a/mm/huge_memory.c
@@ -2129,9 +2129,12 @@ static void freeze_page(struct page *pag
static void unfreeze_page(struct page *page)
{
int i;
-
- for (i = 0; i < HPAGE_PMD_NR; i++)
- remove_migration_ptes(page + i, page + i, true);
+ if (PageTransHuge(page)) {
+ remove_migration_ptes(page, page, true);
+ } else {
+ for (i = 0; i < HPAGE_PMD_NR; i++)
+ remove_migration_ptes(page + i, page + i, true);
+ }
}
static void __split_huge_page_tail(struct page *head, int tail,
diff -puN /dev/null mm/page_vma_mapped.c
--- /dev/null
+++ a/mm/page_vma_mapped.c
@@ -0,0 +1,188 @@
+#include <linux/mm.h>
+#include <linux/rmap.h>
+#include <linux/hugetlb.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+
+#include "internal.h"
+
+static inline bool check_pmd(struct page_vma_mapped_walk *pvmw)
+{
+ pmd_t pmde;
+ /*
+ * Make sure we don't re-load pmd between present and !trans_huge check.
+ * We need a consistent view.
+ */
+ pmde = READ_ONCE(*pvmw->pmd);
+ return pmd_present(pmde) && !pmd_trans_huge(pmde);
+}
+
+static inline bool not_found(struct page_vma_mapped_walk *pvmw)
+{
+ page_vma_mapped_walk_done(pvmw);
+ return false;
+}
+
+static bool map_pte(struct page_vma_mapped_walk *pvmw)
+{
+ pvmw->pte = pte_offset_map(pvmw->pmd, pvmw->address);
+ if (!(pvmw->flags & PVMW_SYNC)) {
+ if (pvmw->flags & PVMW_MIGRATION) {
+ if (!is_swap_pte(*pvmw->pte))
+ return false;
+ } else {
+ if (!pte_present(*pvmw->pte))
+ return false;
+ }
+ }
+ pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd);
+ spin_lock(pvmw->ptl);
+ return true;
+}
+
+static bool check_pte(struct page_vma_mapped_walk *pvmw)
+{
+ if (pvmw->flags & PVMW_MIGRATION) {
+#ifdef CONFIG_MIGRATION
+ swp_entry_t entry;
+ if (!is_swap_pte(*pvmw->pte))
+ return false;
+ entry = pte_to_swp_entry(*pvmw->pte);
+ if (!is_migration_entry(entry))
+ return false;
+ if (migration_entry_to_page(entry) - pvmw->page >=
+ hpage_nr_pages(pvmw->page)) {
+ return false;
+ }
+ if (migration_entry_to_page(entry) < pvmw->page)
+ return false;
+#else
+ WARN_ON_ONCE(1);
+#endif
+ } else {
+ if (!pte_present(*pvmw->pte))
+ return false;
+
+ /* THP can be referenced by any subpage */
+ if (pte_page(*pvmw->pte) - pvmw->page >=
+ hpage_nr_pages(pvmw->page)) {
+ return false;
+ }
+ if (pte_page(*pvmw->pte) < pvmw->page)
+ return false;
+ }
+
+ return true;
+}
+
+/**
+ * page_vma_mapped_walk - check if @pvmw->page is mapped in @pvmw->vma at
+ * @pvmw->address
+ * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags
+ * must be set. pmd, pte and ptl must be NULL.
+ *
+ * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point
+ * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is
+ * adjusted if needed (for PTE-mapped THPs).
+ *
+ * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page
+ * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in
+ * a loop to find all PTEs that map the THP.
+ *
+ * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry
+ * regardless of which page table level the page is mapped at. @pvmw->pmd is
+ * NULL.
+ *
+ * Retruns false if there are no more page table entries for the page in
+ * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped.
+ *
+ * If you need to stop the walk before page_vma_mapped_walk() returned false,
+ * use page_vma_mapped_walk_done(). It will do the housekeeping.
+ */
+bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
+{
+ struct mm_struct *mm = pvmw->vma->vm_mm;
+ struct page *page = pvmw->page;
+ pgd_t *pgd;
+ pud_t *pud;
+
+ /* The only possible pmd mapping has been handled on last iteration */
+ if (pvmw->pmd && !pvmw->pte)
+ return not_found(pvmw);
+
+ /* Only for THP, seek to next pte entry makes sense */
+ if (pvmw->pte) {
+ if (!PageTransHuge(pvmw->page) || PageHuge(pvmw->page))
+ return not_found(pvmw);
+ goto next_pte;
+ }
+
+ if (unlikely(PageHuge(pvmw->page))) {
+ /* when pud is not present, pte will be NULL */
+ pvmw->pte = huge_pte_offset(mm, pvmw->address);
+ if (!pvmw->pte)
+ return false;
+
+ pvmw->ptl = huge_pte_lockptr(page_hstate(page), mm, pvmw->pte);
+ spin_lock(pvmw->ptl);
+ if (!check_pte(pvmw))
+ return not_found(pvmw);
+ return true;
+ }
+restart:
+ pgd = pgd_offset(mm, pvmw->address);
+ if (!pgd_present(*pgd))
+ return false;
+ pud = pud_offset(pgd, pvmw->address);
+ if (!pud_present(*pud))
+ return false;
+ pvmw->pmd = pmd_offset(pud, pvmw->address);
+ if (pmd_trans_huge(*pvmw->pmd)) {
+ pvmw->ptl = pmd_lock(mm, pvmw->pmd);
+ if (!pmd_present(*pvmw->pmd))
+ return not_found(pvmw);
+ if (likely(pmd_trans_huge(*pvmw->pmd))) {
+ if (pvmw->flags & PVMW_MIGRATION)
+ return not_found(pvmw);
+ if (pmd_page(*pvmw->pmd) != page)
+ return not_found(pvmw);
+ return true;
+ } else {
+ /* THP pmd was split under us: handle on pte level */
+ spin_unlock(pvmw->ptl);
+ pvmw->ptl = NULL;
+ }
+ } else {
+ if (!check_pmd(pvmw))
+ return false;
+ }
+ if (!map_pte(pvmw))
+ goto next_pte;
+ while (1) {
+ if (check_pte(pvmw))
+ return true;
+next_pte: do {
+ pvmw->address += PAGE_SIZE;
+ if (pvmw->address >=
+ __vma_address(pvmw->page, pvmw->vma) +
+ hpage_nr_pages(pvmw->page) * PAGE_SIZE)
+ return not_found(pvmw);
+ /* Did we cross page table boundary? */
+ if (pvmw->address % PMD_SIZE == 0) {
+ pte_unmap(pvmw->pte);
+ if (pvmw->ptl) {
+ spin_unlock(pvmw->ptl);
+ pvmw->ptl = NULL;
+ }
+ goto restart;
+ } else {
+ pvmw->pte++;
+ }
+ } while (pte_none(*pvmw->pte));
+
+ if (!pvmw->ptl) {
+ pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
+ spin_lock(pvmw->ptl);
+ }
+ }
+}
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
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