linux-kernel - [RFC 11/11] mm/mremap: simplify vma expansion again

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Message-Id: <20230224100022.11268-12-vbabka@suse.cz>
Date:   Fri, 24 Feb 2023 11:00:22 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     linux-mm@...ck.org, "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc:     linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        maple-tree@...ts.infradead.org, Vlastimil Babka <vbabka@...e.cz>
Subject: [RFC 11/11] mm/mremap: simplify vma expansion again

This effectively reverts d014cd7c1c35 ("mm, mremap: fix mremap()
expanding for vma's with vm_ops->close()"). After the recent changes,
vma_merge() is able to handle the expansion properly even when the vma
being expanded has a vm_ops->close operation, so we don't need to
special case it anymore.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/mremap.c | 20 ++++----------------
 1 file changed, 4 insertions(+), 16 deletions(-)

diff --git a/mm/mremap.c b/mm/mremap.c
index 411a85682b58..65f5b545601e 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -1040,23 +1040,11 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 			 * vma (expand operation itself) and possibly also with
 			 * the next vma if it becomes adjacent to the expanded
 			 * vma and  otherwise compatible.
-			 *
-			 * However, vma_merge() can currently fail due to
-			 * is_mergeable_vma() check for vm_ops->close (see the
-			 * comment there). Yet this should not prevent vma
-			 * expanding, so perform a simple expand for such vma.
-			 * Ideally the check for close op should be only done
-			 * when a vma would be actually removed due to a merge.
 			 */
-			if (!vma->vm_ops || !vma->vm_ops->close) {
-				vma = vma_merge(&vmi, 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));
-			} else if (vma_expand(&vmi, vma, vma->vm_start,
-					addr + new_len, vma->vm_pgoff, NULL)) {
-				vma = NULL;
-			}
+			vma = vma_merge(&vmi, 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;
-- 
2.39.2