[PATCH v9 1/3] madvise: use zap_page_range_single for madvise dontneed

Mike Kravetz
2022-11-11T23:26:54Z

Expose the routine zap_page_range_single to zap a range within a single
vma. The madvise routine madvise_dontneed_single_vma can use this
routine as it explicitly operates on a single vma. Also, update the mmu
notification range in zap_page_range_single to take hugetlb pmd sharing
into account. This is required as MADV_DONTNEED supports hugetlb vmas.

Fixes: 90e7e7f5ef3f ("mm: enable MADV_DONTNEED for hugetlb mappings")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reported-by: Wei Chen <harperchen1110@gmail.com>
Cc: <stable@vger.kernel.org>
---
include/linux/mm.h | 27 +++++++++++++++++++--------
mm/madvise.c | 6 +++---
mm/memory.c | 23 +++++++++++------------
3 files changed, 33 insertions(+), 23 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index e8fc35edaee0..9e7cad65dfde 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1881,6 +1881,23 @@ static void __maybe_unused show_free_areas(unsigned int flags, nodemask_t *nodem
__show_free_areas(flags, nodemask, MAX_NR_ZONES - 1);
}

+/*
+ * Parameter block passed down to zap_pte_range in exceptional cases.
+ */
+struct zap_details {
+ struct folio *single_folio; /* Locked folio to be unmapped */
+ bool even_cows; /* Zap COWed private pages too? */
+ zap_flags_t zap_flags; /* Extra flags for zapping */
+};
+
+/*
+ * Whether to drop the pte markers, for example, the uffd-wp information for
+ * file-backed memory. This should only be specified when we will completely
+ * drop the page in the mm, either by truncation or unmapping of the vma. By
+ * default, the flag is not set.
+ */
+#define ZAP_FLAG_DROP_MARKER ((__force zap_flags_t) BIT(0))
+
#ifdef CONFIG_MMU
extern bool can_do_mlock(void);
#else
@@ -1898,6 +1915,8 @@ void zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
unsigned long size);
void zap_page_range(struct vm_area_struct *vma, unsigned long address,
unsigned long size);
+void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
+ unsigned long size, struct zap_details *details);
void unmap_vmas(struct mmu_gather *tlb, struct maple_tree *mt,
struct vm_area_struct *start_vma, unsigned long start,
unsigned long end);
@@ -3529,12 +3548,4 @@ madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
}
#endif

-/*
- * Whether to drop the pte markers, for example, the uffd-wp information for
- * file-backed memory. This should only be specified when we will completely
- * drop the page in the mm, either by truncation or unmapping of the vma. By
- * default, the flag is not set.
- */
-#define ZAP_FLAG_DROP_MARKER ((__force zap_flags_t) BIT(0))
-
#endif /* _LINUX_MM_H */
diff --git a/mm/madvise.c b/mm/madvise.c
index 68a23104687f..b2f1860a353e 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -785,8 +785,8 @@ static int madvise_free_single_vma(struct vm_area_struct *vma,
* Application no longer needs these pages. If the pages are dirty,
* it's OK to just throw them away. The app will be more careful about
* data it wants to keep. Be sure to free swap resources too. The
- * zap_page_range call sets things up for shrink_active_list to actually free
- * these pages later if no one else has touched them in the meantime,
+ * zap_page_range_single call sets things up for shrink_active_list to actually
+ * free these pages later if no one else has touched them in the meantime,
* although we could add these pages to a global reuse list for
* shrink_active_list to pick up before reclaiming other pages.
*
@@ -803,7 +803,7 @@ static int madvise_free_single_vma(struct vm_area_struct *vma,
static long madvise_dontneed_single_vma(struct vm_area_struct *vma,
unsigned long start, unsigned long end)
{
- zap_page_range(vma, start, end - start);
+ zap_page_range_single(vma, start, end - start, NULL);
return 0;
}

diff --git a/mm/memory.c b/mm/memory.c
index 98ddb91df9a7..ebdbd395cfad 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1294,15 +1294,6 @@ copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma)
return ret;
}

-/*
- * Parameter block passed down to zap_pte_range in exceptional cases.
- */
-struct zap_details {
- struct folio *single_folio; /* Locked folio to be unmapped */
- bool even_cows; /* Zap COWed private pages too? */
- zap_flags_t zap_flags; /* Extra flags for zapping */
-};
-
/* Whether we should zap all COWed (private) pages too */
static inline bool should_zap_cows(struct zap_details *details)
{
@@ -1736,19 +1727,27 @@ void zap_page_range(struct vm_area_struct *vma, unsigned long start,
*
* The range must fit into one VMA.
*/
-static void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
+void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
unsigned long size, struct zap_details *details)
{
+ unsigned long end = address + size;
struct mmu_notifier_range range;
struct mmu_gather tlb;

lru_add_drain();
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
- address, address + size);
+ address, end);
+ if (is_vm_hugetlb_page(vma))
+ adjust_range_if_pmd_sharing_possible(vma, &range.start,
+ &range.end);
tlb_gather_mmu(&tlb, vma->vm_mm);
update_hiwater_rss(vma->vm_mm);
mmu_notifier_invalidate_range_start(&range);
- unmap_single_vma(&tlb, vma, address, range.end, details);
+ /*
+ * unmap 'address-end' not 'range.start-range.end' as range
+ * could have been expanded for hugetlb pmd sharing.
+ */
+ unmap_single_vma(&tlb, vma, address, end, details);
mmu_notifier_invalidate_range_end(&range);
tlb_finish_mmu(&tlb);
}
--
2.37.3