2022-02-07 16:46:57

by Matthew Wilcox

[permalink] [raw]
Subject: [PATCH 51/75] mm/rmap: Convert try_to_unmap() to take a folio

Change both callers and the worker function try_to_unmap_one().
---
include/linux/rmap.h | 4 +--
mm/huge_memory.c | 3 +-
mm/memory-failure.c | 7 ++--
mm/memory_hotplug.c | 13 ++++---
mm/rmap.c | 81 +++++++++++++++++++++++---------------------
mm/vmscan.c | 2 +-
6 files changed, 60 insertions(+), 50 deletions(-)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 31f3a299ef66..66407434c3b5 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -193,7 +193,7 @@ int folio_referenced(struct folio *, int is_locked,
struct mem_cgroup *memcg, unsigned long *vm_flags);

void try_to_migrate(struct page *page, enum ttu_flags flags);
-void try_to_unmap(struct page *, enum ttu_flags flags);
+void try_to_unmap(struct folio *, enum ttu_flags flags);

int make_device_exclusive_range(struct mm_struct *mm, unsigned long start,
unsigned long end, struct page **pages,
@@ -311,7 +311,7 @@ static inline int folio_referenced(struct folio *folio, int is_locked,
return 0;
}

-static inline void try_to_unmap(struct page *page, enum ttu_flags flags)
+static inline void try_to_unmap(struct folio *folio, enum ttu_flags flags)
{
}

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f934b93d08ca..4ea22b7319fd 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2283,6 +2283,7 @@ void vma_adjust_trans_huge(struct vm_area_struct *vma,

static void unmap_page(struct page *page)
{
+ struct folio *folio = page_folio(page);
enum ttu_flags ttu_flags = TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD |
TTU_SYNC;

@@ -2296,7 +2297,7 @@ static void unmap_page(struct page *page)
if (PageAnon(page))
try_to_migrate(page, ttu_flags);
else
- try_to_unmap(page, ttu_flags | TTU_IGNORE_MLOCK);
+ try_to_unmap(folio, ttu_flags | TTU_IGNORE_MLOCK);

VM_WARN_ON_ONCE_PAGE(page_mapped(page), page);
}
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 97a9ed8f87a9..1c7a71b5248e 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1347,6 +1347,7 @@ static int get_hwpoison_page(struct page *p, unsigned long flags)
static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
int flags, struct page *hpage)
{
+ struct folio *folio = page_folio(hpage);
enum ttu_flags ttu = TTU_IGNORE_MLOCK | TTU_SYNC;
struct address_space *mapping;
LIST_HEAD(tokill);
@@ -1412,7 +1413,7 @@ static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
collect_procs(hpage, &tokill, flags & MF_ACTION_REQUIRED);

if (!PageHuge(hpage)) {
- try_to_unmap(hpage, ttu);
+ try_to_unmap(folio, ttu);
} else {
if (!PageAnon(hpage)) {
/*
@@ -1424,12 +1425,12 @@ static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
*/
mapping = hugetlb_page_mapping_lock_write(hpage);
if (mapping) {
- try_to_unmap(hpage, ttu|TTU_RMAP_LOCKED);
+ try_to_unmap(folio, ttu|TTU_RMAP_LOCKED);
i_mmap_unlock_write(mapping);
} else
pr_info("Memory failure: %#lx: could not lock mapping for mapped huge page\n", pfn);
} else {
- try_to_unmap(hpage, ttu);
+ try_to_unmap(folio, ttu);
}
}

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 2a9627dc784c..914057da53c7 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1690,10 +1690,13 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
DEFAULT_RATELIMIT_BURST);

for (pfn = start_pfn; pfn < end_pfn; pfn++) {
+ struct folio *folio;
+
if (!pfn_valid(pfn))
continue;
page = pfn_to_page(pfn);
- head = compound_head(page);
+ folio = page_folio(page);
+ head = &folio->page;

if (PageHuge(page)) {
pfn = page_to_pfn(head) + compound_nr(head) - 1;
@@ -1710,10 +1713,10 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
* the unmap as the catch all safety net).
*/
if (PageHWPoison(page)) {
- if (WARN_ON(PageLRU(page)))
- isolate_lru_page(page);
- if (page_mapped(page))
- try_to_unmap(page, TTU_IGNORE_MLOCK);
+ if (WARN_ON(folio_test_lru(folio)))
+ folio_isolate_lru(folio);
+ if (folio_mapped(folio))
+ try_to_unmap(folio, TTU_IGNORE_MLOCK);
continue;
}

diff --git a/mm/rmap.c b/mm/rmap.c
index 42a147746ff8..c598fd667948 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1452,13 +1452,13 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
* For hugetlb, it could be much worse if we need to do pud
* invalidation in the case of pmd sharing.
*
- * Note that the page can not be free in this function as call of
- * try_to_unmap() must hold a reference on the page.
+ * Note that the folio can not be freed in this function as call of
+ * try_to_unmap() must hold a reference on the folio.
*/
range.end = vma_address_end(&pvmw);
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
address, range.end);
- if (PageHuge(page)) {
+ if (folio_test_hugetlb(folio)) {
/*
* If sharing is possible, start and end will be adjusted
* accordingly.
@@ -1470,31 +1470,34 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,

while (page_vma_mapped_walk(&pvmw)) {
/*
- * If the page is mlock()d, we cannot swap it out.
+ * If the folio is mlock()d, we cannot swap it out.
*/
if (!(flags & TTU_IGNORE_MLOCK) &&
(vma->vm_flags & VM_LOCKED)) {
/*
- * PTE-mapped THP are never marked as mlocked: so do
- * not set it on a DoubleMap THP, nor on an Anon THP
+ * PTE-mapped folios are never marked as mlocked: so do
+ * not set it on a DoubleMap folio, nor on an Anon folio
* (which may still be PTE-mapped after DoubleMap was
* cleared). But stop unmapping even in those cases.
*/
- if (!PageTransCompound(page) || (PageHead(page) &&
- !PageDoubleMap(page) && !PageAnon(page)))
- mlock_vma_page(page);
+ if (!folio_test_large(folio) ||
+ (folio_test_large(folio) &&
+ !folio_test_double_map(folio) &&
+ !folio_test_anon(folio)))
+ mlock_vma_folio(folio);
page_vma_mapped_walk_done(&pvmw);
ret = false;
break;
}

/* Unexpected PMD-mapped THP? */
- VM_BUG_ON_PAGE(!pvmw.pte, page);
+ VM_BUG_ON_FOLIO(!pvmw.pte, folio);

- subpage = page - page_to_pfn(page) + pte_pfn(*pvmw.pte);
+ subpage = folio_page(folio,
+ pte_pfn(*pvmw.pte) - folio_pfn(folio));
address = pvmw.address;

- if (PageHuge(page) && !PageAnon(page)) {
+ if (folio_test_hugetlb(folio) && !folio_test_anon(folio)) {
/*
* To call huge_pmd_unshare, i_mmap_rwsem must be
* held in write mode. Caller needs to explicitly
@@ -1533,7 +1536,7 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
if (should_defer_flush(mm, flags)) {
/*
* We clear the PTE but do not flush so potentially
- * a remote CPU could still be writing to the page.
+ * a remote CPU could still be writing to the folio.
* If the entry was previously clean then the
* architecture must guarantee that a clear->dirty
* transition on a cached TLB entry is written through
@@ -1546,22 +1549,22 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
pteval = ptep_clear_flush(vma, address, pvmw.pte);
}

- /* Move the dirty bit to the page. Now the pte is gone. */
+ /* Set the dirty flag on the folio now the pte is gone. */
if (pte_dirty(pteval))
- set_page_dirty(page);
+ folio_mark_dirty(folio);

/* Update high watermark before we lower rss */
update_hiwater_rss(mm);

- if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
+ if (PageHWPoison(subpage) && !(flags & TTU_IGNORE_HWPOISON)) {
pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
- if (PageHuge(page)) {
- hugetlb_count_sub(compound_nr(page), mm);
+ if (folio_test_hugetlb(folio)) {
+ hugetlb_count_sub(folio_nr_pages(folio), mm);
set_huge_swap_pte_at(mm, address,
pvmw.pte, pteval,
vma_mmu_pagesize(vma));
} else {
- dec_mm_counter(mm, mm_counter(page));
+ dec_mm_counter(mm, mm_counter(&folio->page));
set_pte_at(mm, address, pvmw.pte, pteval);
}

@@ -1576,18 +1579,19 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
* migration) will not expect userfaults on already
* copied pages.
*/
- dec_mm_counter(mm, mm_counter(page));
+ dec_mm_counter(mm, mm_counter(&folio->page));
/* We have to invalidate as we cleared the pte */
mmu_notifier_invalidate_range(mm, address,
address + PAGE_SIZE);
- } else if (PageAnon(page)) {
+ } else if (folio_test_anon(folio)) {
swp_entry_t entry = { .val = page_private(subpage) };
pte_t swp_pte;
/*
* Store the swap location in the pte.
* See handle_pte_fault() ...
*/
- if (unlikely(PageSwapBacked(page) != PageSwapCache(page))) {
+ if (unlikely(folio_test_swapbacked(folio) !=
+ folio_test_swapcache(folio))) {
WARN_ON_ONCE(1);
ret = false;
/* We have to invalidate as we cleared the pte */
@@ -1598,8 +1602,8 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
}

/* MADV_FREE page check */
- if (!PageSwapBacked(page)) {
- if (!PageDirty(page)) {
+ if (!folio_test_swapbacked(folio)) {
+ if (!folio_test_dirty(folio)) {
/* Invalidate as we cleared the pte */
mmu_notifier_invalidate_range(mm,
address, address + PAGE_SIZE);
@@ -1608,11 +1612,11 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
}

/*
- * If the page was redirtied, it cannot be
+ * If the folio was redirtied, it cannot be
* discarded. Remap the page to page table.
*/
set_pte_at(mm, address, pvmw.pte, pteval);
- SetPageSwapBacked(page);
+ folio_set_swapbacked(folio);
ret = false;
page_vma_mapped_walk_done(&pvmw);
break;
@@ -1649,16 +1653,17 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
address + PAGE_SIZE);
} else {
/*
- * This is a locked file-backed page, thus it cannot
- * be removed from the page cache and replaced by a new
- * page before mmu_notifier_invalidate_range_end, so no
- * concurrent thread might update its page table to
- * point at new page while a device still is using this
- * page.
+ * This is a locked file-backed folio,
+ * so it cannot be removed from the page
+ * cache and replaced by a new folio before
+ * mmu_notifier_invalidate_range_end, so no
+ * concurrent thread might update its page table
+ * to point at a new folio while a device is
+ * still using this folio.
*
* See Documentation/vm/mmu_notifier.rst
*/
- dec_mm_counter(mm, mm_counter_file(page));
+ dec_mm_counter(mm, mm_counter_file(&folio->page));
}
discard:
/*
@@ -1668,8 +1673,8 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
*
* See Documentation/vm/mmu_notifier.rst
*/
- page_remove_rmap(subpage, PageHuge(page));
- put_page(page);
+ page_remove_rmap(subpage, folio_test_hugetlb(folio));
+ folio_put(folio);
}

mmu_notifier_invalidate_range_end(&range);
@@ -1698,7 +1703,7 @@ static int page_not_mapped(struct page *page)
* It is the caller's responsibility to check if the page is still
* mapped when needed (use TTU_SYNC to prevent accounting races).
*/
-void try_to_unmap(struct page *page, enum ttu_flags flags)
+void try_to_unmap(struct folio *folio, enum ttu_flags flags)
{
struct rmap_walk_control rwc = {
.rmap_one = try_to_unmap_one,
@@ -1708,9 +1713,9 @@ void try_to_unmap(struct page *page, enum ttu_flags flags)
};

if (flags & TTU_RMAP_LOCKED)
- rmap_walk_locked(page, &rwc);
+ rmap_walk_locked(&folio->page, &rwc);
else
- rmap_walk(page, &rwc);
+ rmap_walk(&folio->page, &rwc);
}

/*
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 1e751ba3b4a8..2e94e0b15a76 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1761,7 +1761,7 @@ static unsigned int shrink_page_list(struct list_head *page_list,
if (unlikely(PageTransHuge(page)))
flags |= TTU_SPLIT_HUGE_PMD;

- try_to_unmap(page, flags);
+ try_to_unmap(folio, flags);
if (page_mapped(page)) {
stat->nr_unmap_fail += nr_pages;
if (!was_swapbacked && PageSwapBacked(page))
--
2.34.1



Subject: Re: [PATCH 51/75] mm/rmap: Convert try_to_unmap() to take a folio

Hi Andrew and Matthew,

On Fri, Feb 4, 2022 at 5:00 PM Matthew Wilcox (Oracle)
<[email protected]> wrote:
>
> Change both callers and the worker function try_to_unmap_one().
...
> diff --git a/mm/rmap.c b/mm/rmap.c
...
> @@ -1598,8 +1602,8 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
> }
>
> /* MADV_FREE page check */
> - if (!PageSwapBacked(page)) {
> - if (!PageDirty(page)) {
> + if (!folio_test_swapbacked(folio)) {
> + if (!folio_test_dirty(folio)) {
> /* Invalidate as we cleared the pte */
> mmu_notifier_invalidate_range(mm,
> address, address + PAGE_SIZE);
> @@ -1608,11 +1612,11 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
> }
>
> /*
> - * If the page was redirtied, it cannot be
> + * If the folio was redirtied, it cannot be
> * discarded. Remap the page to page table.
> */
> set_pte_at(mm, address, pvmw.pte, pteval);
> - SetPageSwapBacked(page);
> + folio_set_swapbacked(folio);
> ret = false;
> page_vma_mapped_walk_done(&pvmw);
> break;
...

This conflicts with patch [1], currently in mmotm, and I'll send
another version anyway.
Should that patch be on top of these folio changes, or the other way around?

The latter would help w/ the stable backports that don't have folios
yet, but I can
send backports there as well; not a problem.

Thanks,

[1] https://lkml.kernel.org/r/[email protected]
[PATCH v3] mm: fix race between MADV_FREE reclaim and blkdev direct IO read

--
Mauricio Faria de Oliveira

2022-02-09 18:47:41

by Matthew Wilcox

[permalink] [raw]
Subject: Re: [PATCH 51/75] mm/rmap: Convert try_to_unmap() to take a folio

On Wed, Feb 09, 2022 at 11:24:34AM -0300, Mauricio Faria de Oliveira wrote:
> Hi Andrew and Matthew,
>
> On Fri, Feb 4, 2022 at 5:00 PM Matthew Wilcox (Oracle)
> <[email protected]> wrote:
> >
> > Change both callers and the worker function try_to_unmap_one().
> ...
> > diff --git a/mm/rmap.c b/mm/rmap.c
> ...
> > @@ -1598,8 +1602,8 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
> > }
> >
> > /* MADV_FREE page check */
> > - if (!PageSwapBacked(page)) {
> > - if (!PageDirty(page)) {
> > + if (!folio_test_swapbacked(folio)) {
> > + if (!folio_test_dirty(folio)) {
> > /* Invalidate as we cleared the pte */
> > mmu_notifier_invalidate_range(mm,
> > address, address + PAGE_SIZE);
> > @@ -1608,11 +1612,11 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
> > }
> >
> > /*
> > - * If the page was redirtied, it cannot be
> > + * If the folio was redirtied, it cannot be
> > * discarded. Remap the page to page table.
> > */
> > set_pte_at(mm, address, pvmw.pte, pteval);
> > - SetPageSwapBacked(page);
> > + folio_set_swapbacked(folio);
> > ret = false;
> > page_vma_mapped_walk_done(&pvmw);
> > break;
> ...
>
> This conflicts with patch [1], currently in mmotm, and I'll send
> another version anyway.
> Should that patch be on top of these folio changes, or the other way around?

Andrew and I need to resolve conflicts between this series and other
patches in his tree. You don't need to worry about this.

> The latter would help w/ the stable backports that don't have folios
> yet, but I can
> send backports there as well; not a problem.
>
> Thanks,
>
> [1] https://lkml.kernel.org/r/[email protected]
> [PATCH v3] mm: fix race between MADV_FREE reclaim and blkdev direct IO read
>
> --
> Mauricio Faria de Oliveira
>