mm/mremap: simplify vma expansion again

This effectively reverts d014cd7c ("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.

Link: https://lkml.kernel.org/r/20230309111258.24079-11-vbabka@suse.czSigned-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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;