[PATCH v4 07/15] util/mmap-alloc: Factor out calculation of the pagesize for the guard page

[David Hildenbrand <david@redhat.com>]

Let's factor out calculating the size of the guard page and rename the
variable to make it clearer that this pagesize only applies to the
guard page.

Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>
Cc: Greg Kurz <groug@kaod.org>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 util/mmap-alloc.c | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
index 27dcccd8ec..f0277f9fad 100644
--- a/util/mmap-alloc.c
+++ b/util/mmap-alloc.c
@@ -82,17 +82,27 @@ size_t qemu_mempath_getpagesize(const char *mem_path)
     return qemu_real_host_page_size;
 }
 
+static inline size_t mmap_guard_pagesize(int fd)
+{
+#if defined(__powerpc64__) && defined(__linux__)
+    /* Mappings in the same segment must share the same page size */
+    return qemu_fd_getpagesize(fd);
+#else
+    return qemu_real_host_page_size;
+#endif
+}
+
 void *qemu_ram_mmap(int fd,
                     size_t size,
                     size_t align,
                     bool shared,
                     bool is_pmem)
 {
+    const size_t guard_pagesize = mmap_guard_pagesize(fd);
     int flags;
     int map_sync_flags = 0;
     int guardfd;
     size_t offset;
-    size_t pagesize;
     size_t total;
     void *guardptr;
     void *ptr;
@@ -113,8 +123,7 @@ void *qemu_ram_mmap(int fd,
      * anonymous memory is OK.
      */
     flags = MAP_PRIVATE;
-    pagesize = qemu_fd_getpagesize(fd);
-    if (fd == -1 || pagesize == qemu_real_host_page_size) {
+    if (fd == -1 || guard_pagesize == qemu_real_host_page_size) {
         guardfd = -1;
         flags |= MAP_ANONYMOUS;
     } else {
@@ -123,7 +132,6 @@ void *qemu_ram_mmap(int fd,
     }
 #else
     guardfd = -1;
-    pagesize = qemu_real_host_page_size;
     flags = MAP_PRIVATE | MAP_ANONYMOUS;
 #endif
 
@@ -135,7 +143,7 @@ void *qemu_ram_mmap(int fd,
 
     assert(is_power_of_2(align));
     /* Always align to host page size */
-    assert(align >= pagesize);
+    assert(align >= guard_pagesize);
 
     flags = MAP_FIXED;
     flags |= fd == -1 ? MAP_ANONYMOUS : 0;
@@ -189,8 +197,8 @@ void *qemu_ram_mmap(int fd,
      * a guard page guarding against potential buffer overflows.
      */
     total -= offset;
-    if (total > size + pagesize) {
-        munmap(ptr + size + pagesize, total - size - pagesize);
+    if (total > size + guard_pagesize) {
+        munmap(ptr + size + guard_pagesize, total - size - guard_pagesize);
     }
 
     return ptr;
@@ -198,15 +206,8 @@ void *qemu_ram_mmap(int fd,
 
 void qemu_ram_munmap(int fd, void *ptr, size_t size)
 {
-    size_t pagesize;
-
     if (ptr) {
         /* Unmap both the RAM block and the guard page */
-#if defined(__powerpc64__) && defined(__linux__)
-        pagesize = qemu_fd_getpagesize(fd);
-#else
-        pagesize = qemu_real_host_page_size;
-#endif
-        munmap(ptr, size + pagesize);
+        munmap(ptr, size + mmap_guard_pagesize(fd));
     }
 }
-- 
2.24.1