From ca3d76b0aa808a06997297d123b66d17b81e5285 Mon Sep 17 00:00:00 2001
From: Jakub Matěna <matenajakub@gmail.com>
Date: Fri, 3 Jun 2022 16:57:19 +0200
Subject: mm: add merging after mremap resize
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When mremap call results in expansion, it might be possible to merge the
VMA with the next VMA which might become adjacent.  This patch adds
vma_merge call after the expansion is done to try and merge.

[akpm@linux-foundation.org: coding-style cleanups]
Link: https://lkml.kernel.org/r/20220603145719.1012094-3-matenajakub@gmail.com
Signed-off-by: Jakub Matěna <matenajakub@gmail.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 mm/mremap.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

(limited to 'mm/mremap.c')

diff --git a/mm/mremap.c b/mm/mremap.c
index 8644ff278f02..e465ffe279bb 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -9,6 +9,7 @@
  */
 
 #include <linux/mm.h>
+#include <linux/mm_inline.h>
 #include <linux/hugetlb.h>
 #include <linux/shm.h>
 #include <linux/ksm.h>
@@ -23,6 +24,7 @@
 #include <linux/mmu_notifier.h>
 #include <linux/uaccess.h>
 #include <linux/userfaultfd_k.h>
+#include <linux/mempolicy.h>
 
 #include <asm/cacheflush.h>
 #include <asm/tlb.h>
@@ -1012,6 +1014,9 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 		/* can we just expand the current mapping? */
 		if (vma_expandable(vma, new_len - old_len)) {
 			long pages = (new_len - old_len) >> PAGE_SHIFT;
+			unsigned long extension_start = addr + old_len;
+			unsigned long extension_end = addr + new_len;
+			pgoff_t extension_pgoff = vma->vm_pgoff + (old_len >> PAGE_SHIFT);
 
 			if (vma->vm_flags & VM_ACCOUNT) {
 				if (security_vm_enough_memory_mm(mm, pages)) {
@@ -1020,8 +1025,18 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 				}
 			}
 
-			if (vma_adjust(vma, vma->vm_start, addr + new_len,
-				       vma->vm_pgoff, NULL)) {
+			/*
+			 * Function vma_merge() is called on the extension we are adding to
+			 * the already existing vma, vma_merge() will merge this extension with
+			 * the already existing vma (expand operation itself) and possibly also
+			 * with the next vma if it becomes adjacent to the expanded vma and
+			 * otherwise compatible.
+			 */
+			vma = vma_merge(mm, vma, extension_start, extension_end,
+					vma->vm_flags, vma->anon_vma, vma->vm_file,
+					extension_pgoff, vma_policy(vma),
+					vma->vm_userfaultfd_ctx, anon_vma_name(vma));
+			if (!vma) {
 				vm_unacct_memory(pages);
 				ret = -ENOMEM;
 				goto out;
-- 
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