apply madv_guard API for CRIU

Author: mihalicyn

fs/proc/task_mmu.c

@@ -1632,6 +1632,7 @@ struct pagemapread {
 #define PM_SOFT_DIRTY		BIT_ULL(55)
 #define PM_MMAP_EXCLUSIVE	BIT_ULL(56)
 #define PM_UFFD_WP		BIT_ULL(57)
+#define PM_GUARD_REGION		BIT_ULL(58)
 #define PM_FILE			BIT_ULL(61)
 #define PM_SWAP			BIT_ULL(62)
 #define PM_PRESENT		BIT_ULL(63)
@@ -1732,6 +1733,8 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
 			page = pfn_swap_entry_to_page(entry);
 		if (pte_marker_entry_uffd_wp(entry))
 			flags |= PM_UFFD_WP;
+		if (is_guard_swp_entry(entry))
+			flags |=  PM_GUARD_REGION;
 	}
 
 	if (page) {
@@ -2063,7 +2066,8 @@ 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 {
@@ -2104,8 +2108,12 @@ 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;

include/uapi/linux/fs.h

@@ -350,6 +350,7 @@ 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