From: Andrei Vagin <avagin@xxxxxxxxx>
Introduce the PAGE_IS_GUARD flag in the PAGEMAP_SCAN ioctl to expose
information about guard regions. This allows userspace tools, such as
CRIU, to detect and handle guard regions.
Signed-off-by: Andrei Vagin <avagin@xxxxxxxxx>
---
Documentation/admin-guide/mm/pagemap.rst | 1 +
fs/proc/task_mmu.c | 8 ++++++--
include/uapi/linux/fs.h | 1 +
3 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst
index a297e824f990..7997b67ffc97 100644
--- a/Documentation/admin-guide/mm/pagemap.rst
+++ b/Documentation/admin-guide/mm/pagemap.rst
@@ -234,6 +234,7 @@ Following flags about pages are currently supported:
- ``PAGE_IS_PFNZERO`` - Page has zero PFN
- ``PAGE_IS_HUGE`` - Page is PMD-mapped THP or Hugetlb backed
- ``PAGE_IS_SOFT_DIRTY`` - Page is soft-dirty
+- ``PAGE_IS_GUARD`` - Page is a guard region
The ``struct pm_scan_arg`` is used as the argument of the IOCTL.
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index c17615e21a5d..698d660bfee4 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -2067,7 +2067,8 @@ static int pagemap_release(struct inode *inode, struct file *file)
#define PM_SCAN_CATEGORIES (PAGE_IS_WPALLOWED | PAGE_IS_WRITTEN | \
PAGE_IS_FILE | PAGE_IS_PRESENT | \
PAGE_IS_SWAPPED | PAGE_IS_PFNZERO | \
- PAGE_IS_HUGE | PAGE_IS_SOFT_DIRTY)
+ PAGE_IS_HUGE | PAGE_IS_SOFT_DIRTY | \
+ PAGE_IS_GUARD)
#define PM_SCAN_FLAGS (PM_SCAN_WP_MATCHING | PM_SCAN_CHECK_WPASYNC)
struct pagemap_scan_private {
@@ -2108,8 +2109,11 @@ static unsigned long pagemap_page_category(struct pagemap_scan_private *p,
if (!pte_swp_uffd_wp_any(pte))
categories |= PAGE_IS_WRITTEN;
+ swp = pte_to_swp_entry(pte);
+ if (is_guard_swp_entry(swp))
+ categories |= PAGE_IS_GUARD;
+
if (p->masks_of_interest & PAGE_IS_FILE) {
- swp = pte_to_swp_entry(pte);
if (is_pfn_swap_entry(swp) &&
!folio_test_anon(pfn_swap_entry_folio(swp)))
categories |= PAGE_IS_FILE;
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index 2bbe00cf1248..8aa66c5f69b7 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -363,6 +363,7 @@ typedef int __bitwise __kernel_rwf_t;
#define PAGE_IS_PFNZERO (1 << 5)
#define PAGE_IS_HUGE (1 << 6)
#define PAGE_IS_SOFT_DIRTY (1 << 7)
+#define PAGE_IS_GUARD (1 << 8)
/*
* struct page_region - Page region with flags
--
2.49.0.rc1.451.g8f38331e32-goog
