Subject: [RFC PATCH RESEND 13/28] mm: conditionally mark VMA as locked in free_pgtables and unmap_page_range

From: Suren Baghdasaryan <[email-masked]>
Date: Thu, 1 Sep 2022 10:35:01 -0700

free_pgtables and unmap_page_range functions can be called with mmap_lock
held for write (e.g. in mmap_region), held for read (e.g in
madvise_pageout) or not held at all (e.g in madvise_remove might
drop mmap_lock before calling vfs_fallocate, which ends up calling
unmap_page_range).
Provide free_pgtables and unmap_page_range with additional argument
indicating whether to mark the VMA as locked or not based on the usage.
The parameter is set based on whether mmap_lock is held in write mode
during the call. This ensures no change in behavior between mmap_lock
and per-vma locks.

Signed-off-by: Suren Baghdasaryan <[email-masked]>
---
 include/linux/mm.h |  2 +-
 mm/internal.h      |  4 ++--
 mm/memory.c        | 32 +++++++++++++++++++++-----------
 mm/mmap.c          | 17 +++++++++--------
 mm/oom_kill.c      |  3 ++-
 5 files changed, 35 insertions(+), 23 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 476bf936c5f0..dc72be923e5b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1874,7 +1874,7 @@ void zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
 void zap_page_range(struct vm_area_struct *vma, unsigned long address,
 		    unsigned long size);
 void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
-		unsigned long start, unsigned long end);
+		unsigned long start, unsigned long end, bool lock_vma);
 
 struct mmu_notifier_range;
 
diff --git a/mm/internal.h b/mm/internal.h
index 785409805ed7..e6c0f999e0cb 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -85,14 +85,14 @@ bool __folio_end_writeback(struct folio *folio);
 void deactivate_file_folio(struct folio *folio);
 
 void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
-		unsigned long floor, unsigned long ceiling);
+		unsigned long floor, unsigned long ceiling, bool lock_vma);
 void pmd_install(struct mm_struct *mm, pmd_t *pmd, pgtable_t *pte);
 
 struct zap_details;
 void unmap_page_range(struct mmu_gather *tlb,
 			     struct vm_area_struct *vma,
 			     unsigned long addr, unsigned long end,
-			     struct zap_details *details);
+			     struct zap_details *details, bool lock_vma);
 
 void page_cache_ra_order(struct readahead_control *, struct file_ra_state *,
 		unsigned int order);
diff --git a/mm/memory.c b/mm/memory.c
index 4ba73f5aa8bb..9ac9944e8c62 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -403,7 +403,7 @@ void free_pgd_range(struct mmu_gather *tlb,
 }
 
 void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
-		unsigned long floor, unsigned long ceiling)
+		unsigned long floor, unsigned long ceiling, bool lock_vma)
 {
 	while (vma) {
 		struct vm_area_struct *next = vma->vm_next;
@@ -413,6 +413,8 @@ void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
 		 * Hide vma from rmap and truncate_pagecache before freeing
 		 * pgtables
 		 */
+		if (lock_vma)
+			vma_mark_locked(vma);
 		unlink_anon_vmas(vma);
 		unlink_file_vma(vma);
 
@@ -427,6 +429,8 @@ void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
 			       && !is_vm_hugetlb_page(next)) {
 				vma = next;
 				next = vma->vm_next;
+				if (lock_vma)
+					vma_mark_locked(vma);
 				unlink_anon_vmas(vma);
 				unlink_file_vma(vma);
 			}
@@ -1631,12 +1635,16 @@ static inline unsigned long zap_p4d_range(struct mmu_gather *tlb,
 void unmap_page_range(struct mmu_gather *tlb,
 			     struct vm_area_struct *vma,
 			     unsigned long addr, unsigned long end,
-			     struct zap_details *details)
+			     struct zap_details *details,
+			     bool lock_vma)
 {
 	pgd_t *pgd;
 	unsigned long next;
 
 	BUG_ON(addr >= end);
+	if (lock_vma)
+		vma_mark_locked(vma);
+
 	tlb_start_vma(tlb, vma);
 	pgd = pgd_offset(vma->vm_mm, addr);
 	do {
@@ -1652,7 +1660,7 @@ void unmap_page_range(struct mmu_gather *tlb,
 static void unmap_single_vma(struct mmu_gather *tlb,
 		struct vm_area_struct *vma, unsigned long start_addr,
 		unsigned long end_addr,
-		struct zap_details *details)
+		struct zap_details *details, bool lock_vma)
 {
 	unsigned long start = max(vma->vm_start, start_addr);
 	unsigned long end;
@@ -1691,7 +1699,7 @@ static void unmap_single_vma(struct mmu_gather *tlb,
 				i_mmap_unlock_write(vma->vm_file->f_mapping);
 			}
 		} else
-			unmap_page_range(tlb, vma, start, end, details);
+			unmap_page_range(tlb, vma, start, end, details, lock_vma);
 	}
 }
 
@@ -1715,7 +1723,7 @@ static void unmap_single_vma(struct mmu_gather *tlb,
  */
 void unmap_vmas(struct mmu_gather *tlb,
 		struct vm_area_struct *vma, unsigned long start_addr,
-		unsigned long end_addr)
+		unsigned long end_addr, bool lock_vma)
 {
 	struct mmu_notifier_range range;
 	struct zap_details details = {
@@ -1728,7 +1736,8 @@ void unmap_vmas(struct mmu_gather *tlb,
 				start_addr, end_addr);
 	mmu_notifier_invalidate_range_start(&range);
 	for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next)
-		unmap_single_vma(tlb, vma, start_addr, end_addr, &details);
+		unmap_single_vma(tlb, vma, start_addr, end_addr, &details,
+				 lock_vma);
 	mmu_notifier_invalidate_range_end(&range);
 }
 
@@ -1753,7 +1762,7 @@ void zap_page_range(struct vm_area_struct *vma, unsigned long start,
 	update_hiwater_rss(vma->vm_mm);
 	mmu_notifier_invalidate_range_start(&range);
 	for ( ; vma && vma->vm_start < range.end; vma = vma->vm_next)
-		unmap_single_vma(&tlb, vma, start, range.end, NULL);
+		unmap_single_vma(&tlb, vma, start, range.end, NULL, false);
 	mmu_notifier_invalidate_range_end(&range);
 	tlb_finish_mmu(&tlb);
 }
@@ -1768,7 +1777,7 @@ 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,
-		unsigned long size, struct zap_details *details)
+		unsigned long size, struct zap_details *details, bool lock_vma)
 {
 	struct mmu_notifier_range range;
 	struct mmu_gather tlb;
@@ -1779,7 +1788,7 @@ static void zap_page_range_single(struct vm_area_struct *vma, unsigned long addr
 	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_single_vma(&tlb, vma, address, range.end, details, lock_vma);
 	mmu_notifier_invalidate_range_end(&range);
 	tlb_finish_mmu(&tlb);
 }
@@ -1802,7 +1811,7 @@ void zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
 	    		!(vma->vm_flags & VM_PFNMAP))
 		return;
 
-	zap_page_range_single(vma, address, size, NULL);
+	zap_page_range_single(vma, address, size, NULL, true);
 }
 EXPORT_SYMBOL_GPL(zap_vma_ptes);
 
@@ -3483,7 +3492,8 @@ static void unmap_mapping_range_vma(struct vm_area_struct *vma,
 		unsigned long start_addr, unsigned long end_addr,
 		struct zap_details *details)
 {
-	zap_page_range_single(vma, start_addr, end_addr - start_addr, details);
+	zap_page_range_single(vma, start_addr, end_addr - start_addr, details,
+			      false);
 }
 
 static inline void unmap_mapping_range_tree(struct rb_root_cached *root,
diff --git a/mm/mmap.c b/mm/mmap.c
index 121544fd90de..094678b4434b 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -79,7 +79,7 @@ core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644);
 
 static void unmap_region(struct mm_struct *mm,
 		struct vm_area_struct *vma, struct vm_area_struct *prev,
-		unsigned long start, unsigned long end);
+		unsigned long start, unsigned long end, bool lock_vma);
 
 static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
 {
@@ -1866,7 +1866,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 	vma->vm_file = NULL;
 
 	/* Undo any partial mapping done by a device driver. */
-	unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
+	unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end, true);
 	if (vm_flags & VM_SHARED)
 		mapping_unmap_writable(file->f_mapping);
 free_vma:
@@ -2626,7 +2626,7 @@ static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
  */
 static void unmap_region(struct mm_struct *mm,
 		struct vm_area_struct *vma, struct vm_area_struct *prev,
-		unsigned long start, unsigned long end)
+		unsigned long start, unsigned long end, bool lock_vma)
 {
 	struct vm_area_struct *next = vma_next(mm, prev);
 	struct mmu_gather tlb;
@@ -2634,9 +2634,10 @@ static void unmap_region(struct mm_struct *mm,
 	lru_add_drain();
 	tlb_gather_mmu(&tlb, mm);
 	update_hiwater_rss(mm);
-	unmap_vmas(&tlb, vma, start, end);
+	unmap_vmas(&tlb, vma, start, end, lock_vma);
 	free_pgtables(&tlb, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
-				 next ? next->vm_start : USER_PGTABLES_CEILING);
+				 next ? next->vm_start : USER_PGTABLES_CEILING,
+				 lock_vma);
 	tlb_finish_mmu(&tlb);
 }
 
@@ -2849,7 +2850,7 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 	if (downgrade)
 		mmap_write_downgrade(mm);
 
-	unmap_region(mm, vma, prev, start, end);
+	unmap_region(mm, vma, prev, start, end, !downgrade);
 
 	/* Fix up all other VM information */
 	remove_vma_list(mm, vma);
@@ -3129,8 +3130,8 @@ void exit_mmap(struct mm_struct *mm)
 	tlb_gather_mmu_fullmm(&tlb, mm);
 	/* update_hiwater_rss(mm) here? but nobody should be looking */
 	/* Use -1 here to ensure all VMAs in the mm are unmapped */
-	unmap_vmas(&tlb, vma, 0, -1);
-	free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING);
+	unmap_vmas(&tlb, vma, 0, -1, true);
+	free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING, true);
 	tlb_finish_mmu(&tlb);
 
 	/* Walk the list again, actually closing and freeing it. */
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 3c6cf9e3cd66..6ffa7c511aa3 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -549,7 +549,8 @@ bool __oom_reap_task_mm(struct mm_struct *mm)
 				ret = false;
 				continue;
 			}
-			unmap_page_range(&tlb, vma, range.start, range.end, NULL);
+			unmap_page_range(&tlb, vma, range.start, range.end,
+					 NULL, false);
 			mmu_notifier_invalidate_range_end(&range);
 			tlb_finish_mmu(&tlb);
 		}
-- 
2.37.2.789.g6183377224-goog