From: Liam R. Howlett <Liam.Howlett@Oracle.com>
Date: Fri, 20 Nov 2020 03:40:37 +0000 (-0500)
Subject: mm/mmap: __do_munmap() Add maple state support.
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=66b4c64a4bc31474f9f85f7375b0c65c08dcb739;p=users%2Fjedix%2Flinux-maple.git

mm/mmap: __do_munmap() Add maple state support.

Adding ma_state support means costly walks through the tree can be
avoided most of the time.  The write operation can simply store the
value at the location previously searched.

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
---

diff --git a/mm/mmap.c b/mm/mmap.c
index b20a9a18a772..19b809d238ee 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2740,7 +2740,7 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 	struct vm_area_struct *vma, *next, *prev, *last;
 	struct vm_area_struct start_split, end_split;
 	int map_count = 0;
-	//MA_STATE(mas, &mm->mm_mt, start, start);
+	MA_STATE(mas, &mm->mm_mt, start, start);
 
 
 	if ((offset_in_page(start)) || start > TASK_SIZE || len > TASK_SIZE-start)
@@ -2755,10 +2755,11 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 	arch_unmap(mm, start, end);
 
 	/* Find the first overlapping VMA */
-	vma = find_vma_intersection(mm, start, end);
+	vma = mas_find(&mas, end - 1);
 	if (!vma)
 		return 0;
 
+	/* Check for userfaultfd now before altering the mm */
 	if (unlikely(uf)) {
 		int error = userfaultfd_unmap_prep(vma, start, end, uf);
 
@@ -2769,11 +2770,23 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 	if (start > vma->vm_start) {
 		if (unlikely(vma->vm_end > end)) {
 			// adjust the same vma twice requires a split.
-			int error = __split_vma(mm, vma, start, 0);
+			int error;
+			/*
+			 * Make sure that map_count on return from munmap() will
+			 * not exceed its limit; but let map_count go just above
+			 * its limit temporarily, to help free resources as expected.
+			 */
+			if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
+				return -ENOMEM;
+
+			error = __split_vma(mm, vma, start, 0);
 			if (error)
 				return error;
+
 			prev = vma;
-			vma = vma_next(mm, prev);
+			mas_reset(&mas);
+			mas_set(&mas, start);
+			vma = mas_walk(&mas);
 		} else {
 			vma_shorten(vma, vma->vm_start, start, &start_split);
 			prev = vma;
@@ -2800,10 +2813,8 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 		last = &end_split;
 	}
 
-
-
-	/*
-	 * unlock any mlock()ed ranges before detaching vmas
+	/* unlock any mlock()ed VMAs and count the number of VMAs to be
+	 * detached.
 	 */
 	next = vma;
 	while (next && next->vm_start < end) {
@@ -2815,10 +2826,8 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 
 		next = next->vm_next;
 	}
-	//printk("tmp %px, map count is %d\n", tmp, map_count);
-
 
-	/* Detach vmas from the MM linked list and remove from the mm tree*/
+	/* Detach vmas from the MM linked list */
 	vma->vm_prev = NULL;
 	if (prev)
 		prev->vm_next = next;
@@ -2834,22 +2843,28 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 		last = vma;
 
 	last->vm_next = NULL;
+
+	/* Detach VMAs from the maple tree */
+	mas.index = start;
+	mas.last = end - 1;
+	mas_store_gfp(&mas, NULL, GFP_KERNEL);
+
+	/* Update map_count */
 	mm->map_count -= map_count;
-	vma_mt_szero(mm, start, end);
 
+	/* Downgrade the lock, if possible */
 	if (next && (next->vm_flags & VM_GROWSDOWN))
 		downgrade = false;
 	else if (prev && (prev->vm_flags & VM_GROWSUP))
 		downgrade = false;
 
-
 	if (downgrade)
 		mmap_write_downgrade(mm);
 
-	/* vma -> last is a separate lined list.  Add start_split and end_split
-	 * if necessary */
+	/* Actual unmap the region */
 	unmap_region(mm, vma, prev, start, end);
 
+	/* Take care of accounting for orphan VMAs, and remove from the list. */
 	if (vma == &start_split) {
 		if (vma->vm_flags & VM_ACCOUNT) {
 			long nrpages = vma_pages(vma);
@@ -2860,7 +2875,6 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 		vma = vma->vm_next;
 	}
 
-	// Cleanup accounting.
 	if (last == &end_split) {
 		if (last->vm_flags & VM_ACCOUNT) {
 			long nrpages = vma_pages(last);
@@ -2875,7 +2889,7 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 			vma = NULL;
 	}
 
-	/* Fix up all other VM information */
+	/* Clean up accounting and free VMAs */
 	if (vma)
 		remove_vma_list(mm, vma);