mm/vma: inline munmap operation in mmap_region()

mmap_region is already passed sanitized addr and len, so change the call
to do_vmi_munmap() to do_vmi_align_munmap() and inline the other checks.

The inlining of the function and checks is an intermediate step in the
series so future patches are easier to follow.

Link: https://lkml.kernel.org/r/20240830040101.822209-9-Liam.Howlett@oracle.comSigned-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Bert Karwatzki <spasswolf@web.de>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/mmap.c

@@ -1388,12 +1388,15 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 			return -ENOMEM;
 	}
 
-	/* Unmap any existing mapping in the area */
-	error = do_vmi_munmap(&vmi, mm, addr, len, uf, false);
-	if (error == -EPERM)
-		return error;
-	else if (error)
-		return -ENOMEM;
+	/* Find the first overlapping VMA */
+	vma = vma_find(&vmi, end);
+	if (vma) {
+		/* Unmap any existing mapping in the area */
+		error = do_vmi_align_munmap(&vmi, vma, mm, addr, end, uf, false);
+		if (error)
+			return error;
+		vma = NULL;
+	}
 
 	/*
 	 * Private writable mapping: check memory availability