mm: change do_vmi_align_munmap() tracking of VMAs to remove

The majority of the calls to munmap a vm range is within 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().

Link: https://lkml.kernel.org/r/20230724183157.3939892-4-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 7 insertions, 9 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 3e16f0637376..ed4807deec89 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -361,12 +361,10 @@ 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;
@@ -375,7 +373,7 @@ 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
@@ -396,7 +394,7 @@ 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);
@@ -1713,9 +1711,10 @@ 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 = {
@@ -1723,7 +1722,6 @@ 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);
@@ -1731,7 +1729,7 @@ 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);
 }