From: Suren Baghdasaryan <surenb@google.com>
Date: Mon, 27 Feb 2023 17:36:18 +0000 (-0800)
Subject: mm: conditionally write-lock VMA in free_pgtables
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=8b6e12d974dca8b82bf961e2eb75f81d4040debb;p=users%2Fjedix%2Flinux-maple.git

mm: conditionally write-lock VMA in free_pgtables

Normally free_pgtables needs to lock affected VMAs except for the case
when VMAs were isolated under VMA write-lock.  munmap() does just that,
isolating while holding appropriate locks and then downgrading mmap_lock
and dropping per-VMA locks before freeing page tables.  Add a parameter to
free_pgtables for such scenario.

Link: https://lkml.kernel.org/r/20230227173632.3292573-20-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/internal.h b/mm/internal.h
index 08ce56dbb1d9..fce94775819c 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -105,7 +105,7 @@ void folio_activate(struct folio *folio);
 
 void free_pgtables(struct mmu_gather *tlb, struct maple_tree *mt,
 		   struct vm_area_struct *start_vma, unsigned long floor,
-		   unsigned long ceiling);
+		   unsigned long ceiling, bool mm_wr_locked);
 void pmd_install(struct mm_struct *mm, pmd_t *pmd, pgtable_t *pte);
 
 struct zap_details;
diff --git a/mm/memory.c b/mm/memory.c
index 36e8ba43e4d3..d100999bc433 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -348,7 +348,7 @@ void free_pgd_range(struct mmu_gather *tlb,
 
 void free_pgtables(struct mmu_gather *tlb, struct maple_tree *mt,
 		   struct vm_area_struct *vma, unsigned long floor,
-		   unsigned long ceiling)
+		   unsigned long ceiling, bool mm_wr_locked)
 {
 	MA_STATE(mas, mt, vma->vm_end, vma->vm_end);
 
@@ -366,6 +366,8 @@ void free_pgtables(struct mmu_gather *tlb, struct maple_tree *mt,
 		 * Hide vma from rmap and truncate_pagecache before freeing
 		 * pgtables
 		 */
+		if (mm_wr_locked)
+			vma_start_write(vma);
 		unlink_anon_vmas(vma);
 		unlink_file_vma(vma);
 
@@ -380,6 +382,8 @@ void free_pgtables(struct mmu_gather *tlb, struct maple_tree *mt,
 			       && !is_vm_hugetlb_page(next)) {
 				vma = next;
 				next = mas_find(&mas, ceiling - 1);
+				if (mm_wr_locked)
+					vma_start_write(vma);
 				unlink_anon_vmas(vma);
 				unlink_file_vma(vma);
 			}
diff --git a/mm/mmap.c b/mm/mmap.c
index 680aecc1d5b6..36f2e5a37a42 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2151,7 +2151,8 @@ static void unmap_region(struct mm_struct *mm, struct maple_tree *mt,
 	update_hiwater_rss(mm);
 	unmap_vmas(&tlb, mt, vma, start, end, mm_wr_locked);
 	free_pgtables(&tlb, mt, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
-				 next ? next->vm_start : USER_PGTABLES_CEILING);
+				 next ? next->vm_start : USER_PGTABLES_CEILING,
+				 mm_wr_locked);
 	tlb_finish_mmu(&tlb);
 }
 
@@ -3049,7 +3050,7 @@ void exit_mmap(struct mm_struct *mm)
 	mmap_write_lock(mm);
 	mt_clear_in_rcu(&mm->mm_mt);
 	free_pgtables(&tlb, &mm->mm_mt, vma, FIRST_USER_ADDRESS,
-		      USER_PGTABLES_CEILING);
+		      USER_PGTABLES_CEILING, true);
 	tlb_finish_mmu(&tlb);
 
 	/*