Commit ace71a19 authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Linus Torvalds

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@linux.intel.comSigned-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c8394812
......@@ -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_transhuge(struct page *page,
}
#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.
*/
......
......@@ -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
......
......@@ -2129,9 +2129,12 @@ static void freeze_page(struct page *page)
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,
......
#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);
}
}
}
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