[PATCH 04/14] mm: Change do_vmi_align_munmap() side tree index
From: Liam R. Howlett
Date: Wed May 31 2023 - 22:17:03 EST
The majority of the calls to munmap a VMA is for a single vma. The
maple tree is able to store a single entry at 0, with a size of 1 as a
pointer and avoid any allocations. Change do_vmi_align_munmap() to
store the VMAs being munmap()'ed into a tree indexed by the count. This
will leverage the ability to store the first entry without a node
allocation.
Storing the entries into a tree by the count and not the vma start and
end means changing the functions which iterate over the entries. Update
unmap_vmas() and free_pgtables() to take a maple state and a tree end
address to support this functionality.
Passing through the same maple state to unmap_vmas() and free_pgtables()
means the state needs to be reset between calls. This happens in the
static unmap_region() and exit_mmap().
Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
---
mm/internal.h | 8 ++++----
mm/memory.c | 16 +++++++---------
mm/mmap.c | 41 ++++++++++++++++++++++++-----------------
3 files changed, 35 insertions(+), 30 deletions(-)
diff --git a/mm/internal.h b/mm/internal.h
index 9b665c4e5fc0..24437f11d3c2 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -103,7 +103,7 @@ bool __folio_end_writeback(struct folio *folio);
void deactivate_file_folio(struct folio *folio);
void folio_activate(struct folio *folio);
-void free_pgtables(struct mmu_gather *tlb, struct maple_tree *mt,
+void free_pgtables(struct mmu_gather *tlb, struct ma_state *mas,
struct vm_area_struct *start_vma, unsigned long floor,
unsigned long ceiling, bool mm_wr_locked);
void pmd_install(struct mm_struct *mm, pmd_t *pmd, pgtable_t *pte);
@@ -1099,9 +1099,9 @@ static inline int vma_iter_store_gfp(struct vma_iterator *vmi,
return 0;
}
-void unmap_vmas(struct mmu_gather *tlb, struct maple_tree *mt,
- struct vm_area_struct *vma, unsigned long start_addr,
- unsigned long end_addr, bool mm_wr_locked);
+void unmap_vmas(struct mmu_gather *tlb, struct ma_state *mas,
+ struct vm_area_struct *start_vma, unsigned long start,
+ unsigned long end, unsigned long tree_end, bool mm_wr_locked);
/*
* VMA lock generalization
diff --git a/mm/memory.c b/mm/memory.c
index 8358f3b853f2..6737263e17e3 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -360,12 +360,10 @@ void free_pgd_range(struct mmu_gather *tlb,
} while (pgd++, addr = next, addr != end);
}
-void free_pgtables(struct mmu_gather *tlb, struct maple_tree *mt,
+void free_pgtables(struct mmu_gather *tlb, struct ma_state *mas,
struct vm_area_struct *vma, unsigned long floor,
unsigned long ceiling, bool mm_wr_locked)
{
- MA_STATE(mas, mt, vma->vm_end, vma->vm_end);
-
do {
unsigned long addr = vma->vm_start;
struct vm_area_struct *next;
@@ -374,7 +372,7 @@ void free_pgtables(struct mmu_gather *tlb, struct maple_tree *mt,
* Note: USER_PGTABLES_CEILING may be passed as ceiling and may
* be 0. This will underflow and is okay.
*/
- next = mas_find(&mas, ceiling - 1);
+ next = mas_find(mas, ceiling - 1);
/*
* Hide vma from rmap and truncate_pagecache before freeing
@@ -395,7 +393,7 @@ void free_pgtables(struct mmu_gather *tlb, struct maple_tree *mt,
while (next && next->vm_start <= vma->vm_end + PMD_SIZE
&& !is_vm_hugetlb_page(next)) {
vma = next;
- next = mas_find(&mas, ceiling - 1);
+ next = mas_find(mas, ceiling - 1);
if (mm_wr_locked)
vma_start_write(vma);
unlink_anon_vmas(vma);
@@ -1700,9 +1698,10 @@ static void unmap_single_vma(struct mmu_gather *tlb,
* ensure that any thus-far unmapped pages are flushed before unmap_vmas()
* drops the lock and schedules.
*/
-void unmap_vmas(struct mmu_gather *tlb, struct maple_tree *mt,
+void unmap_vmas(struct mmu_gather *tlb, struct ma_state *mas,
struct vm_area_struct *vma, unsigned long start_addr,
- unsigned long end_addr, bool mm_wr_locked)
+ unsigned long end_addr, unsigned long tree_end,
+ bool mm_wr_locked)
{
struct mmu_notifier_range range;
struct zap_details details = {
@@ -1710,7 +1709,6 @@ void unmap_vmas(struct mmu_gather *tlb, struct maple_tree *mt,
/* Careful - we need to zap private pages too! */
.even_cows = true,
};
- MA_STATE(mas, mt, vma->vm_end, vma->vm_end);
mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma->vm_mm,
start_addr, end_addr);
@@ -1718,7 +1716,7 @@ void unmap_vmas(struct mmu_gather *tlb, struct maple_tree *mt,
do {
unmap_single_vma(tlb, vma, start_addr, end_addr, &details,
mm_wr_locked);
- } while ((vma = mas_find(&mas, end_addr - 1)) != NULL);
+ } while ((vma = mas_find(mas, tree_end - 1)) != NULL);
mmu_notifier_invalidate_range_end(&range);
}
diff --git a/mm/mmap.c b/mm/mmap.c
index 1503a7bdb192..8e5563668b18 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -76,10 +76,10 @@ int mmap_rnd_compat_bits __read_mostly = CONFIG_ARCH_MMAP_RND_COMPAT_BITS;
static bool ignore_rlimit_data;
core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644);
-static void unmap_region(struct mm_struct *mm, struct maple_tree *mt,
+static void unmap_region(struct mm_struct *mm, struct ma_state *mas,
struct vm_area_struct *vma, struct vm_area_struct *prev,
struct vm_area_struct *next, unsigned long start,
- unsigned long end, bool mm_wr_locked);
+ unsigned long end, unsigned long tree_end, bool mm_wr_locked);
static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
{
@@ -2221,18 +2221,20 @@ static inline void remove_mt(struct mm_struct *mm, struct ma_state *mas)
*
* Called with the mm semaphore held.
*/
-static void unmap_region(struct mm_struct *mm, struct maple_tree *mt,
+static void unmap_region(struct mm_struct *mm, struct ma_state *mas,
struct vm_area_struct *vma, struct vm_area_struct *prev,
- struct vm_area_struct *next,
- unsigned long start, unsigned long end, bool mm_wr_locked)
+ struct vm_area_struct *next, unsigned long start,
+ unsigned long end, unsigned long tree_end, bool mm_wr_locked)
{
struct mmu_gather tlb;
+ unsigned long mt_start = mas->index;
lru_add_drain();
tlb_gather_mmu(&tlb, mm);
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,
+ unmap_vmas(&tlb, mas, vma, start, end, tree_end, mm_wr_locked);
+ mas_set(mas, mt_start);
+ free_pgtables(&tlb, mas, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
next ? next->vm_start : USER_PGTABLES_CEILING,
mm_wr_locked);
tlb_finish_mmu(&tlb);
@@ -2338,7 +2340,6 @@ static inline int munmap_sidetree(struct vm_area_struct *vma,
struct ma_state *mas_detach)
{
vma_start_write(vma);
- mas_set_range(mas_detach, vma->vm_start, vma->vm_end - 1);
if (mas_store_gfp(mas_detach, vma, GFP_KERNEL))
return -ENOMEM;
@@ -2415,6 +2416,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
if (error)
goto end_split_failed;
}
+ mas_set(&mas_detach, count);
error = munmap_sidetree(next, &mas_detach);
if (error)
goto munmap_sidetree_failed;
@@ -2450,17 +2452,17 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
#if defined(CONFIG_DEBUG_VM_MAPLE_TREE)
/* Make sure no VMAs are about to be lost. */
{
- MA_STATE(test, &mt_detach, start, end - 1);
+ MA_STATE(test, &mt_detach, 0, 0);
struct vm_area_struct *vma_mas, *vma_test;
int test_count = 0;
vma_iter_set(vmi, start);
rcu_read_lock();
- vma_test = mas_find(&test, end - 1);
+ vma_test = mas_find(&test, count - 1);
for_each_vma_range(*vmi, vma_mas, end) {
BUG_ON(vma_mas != vma_test);
test_count++;
- vma_test = mas_next(&test, end - 1);
+ vma_test = mas_next(&test, count - 1);
}
rcu_read_unlock();
BUG_ON(count != test_count);
@@ -2490,9 +2492,11 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
* We can free page tables without write-locking mmap_lock because VMAs
* were isolated before we downgraded mmap_lock.
*/
- unmap_region(mm, &mt_detach, vma, prev, next, start, end, !downgrade);
+ mas_set(&mas_detach, 1);
+ unmap_region(mm, &mas_detach, vma, prev, next, start, end, count,
+ !downgrade);
/* Statistics and freeing VMAs */
- mas_set(&mas_detach, start);
+ mas_set(&mas_detach, 0);
remove_mt(mm, &mas_detach);
__mt_destroy(&mt_detach);
@@ -2800,9 +2804,10 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
fput(vma->vm_file);
vma->vm_file = NULL;
+ vma_iter_set(&vmi, vma->vm_end);
/* Undo any partial mapping done by a device driver. */
- unmap_region(mm, &mm->mm_mt, vma, prev, next, vma->vm_start,
- vma->vm_end, true);
+ unmap_region(mm, &vmi.mas, vma, prev, next, vma->vm_start,
+ vma->vm_end, vma->vm_end, true);
}
if (file && (vm_flags & VM_SHARED))
mapping_unmap_writable(file->f_mapping);
@@ -3131,7 +3136,7 @@ void exit_mmap(struct mm_struct *mm)
tlb_gather_mmu_fullmm(&tlb, mm);
/* update_hiwater_rss(mm) here? but nobody should be looking */
/* Use ULONG_MAX here to ensure all VMAs in the mm are unmapped */
- unmap_vmas(&tlb, &mm->mm_mt, vma, 0, ULONG_MAX, false);
+ unmap_vmas(&tlb, &mas, vma, 0, ULONG_MAX, ULONG_MAX, false);
mmap_read_unlock(mm);
/*
@@ -3141,7 +3146,8 @@ void exit_mmap(struct mm_struct *mm)
set_bit(MMF_OOM_SKIP, &mm->flags);
mmap_write_lock(mm);
mt_clear_in_rcu(&mm->mm_mt);
- free_pgtables(&tlb, &mm->mm_mt, vma, FIRST_USER_ADDRESS,
+ mas_set(&mas, vma->vm_end);
+ free_pgtables(&tlb, &mas, vma, FIRST_USER_ADDRESS,
USER_PGTABLES_CEILING, true);
tlb_finish_mmu(&tlb);
@@ -3150,6 +3156,7 @@ void exit_mmap(struct mm_struct *mm)
* enabled, without holding any MM locks besides the unreachable
* mmap_write_lock.
*/
+ mas_set(&mas, vma->vm_end);
do {
if (vma->vm_flags & VM_ACCOUNT)
nr_accounted += vma_pages(vma);
--
2.39.2