diff mbox

[PULL,23/31] util/mmap-alloc: refactor a little bit for readability

Message ID c15c23efebc92bfcf886114d06b8e2a1bc8e48bb.1485250702.git.mjt@msgid.tls.msk.ru
State New
Headers show

Commit Message

Michael Tokarev Jan. 24, 2017, 9:39 a.m. UTC 
From: Cao jin <caoj.fnst@cn.fujitsu.com>

1st mmap returns *ptr* which aligns to host page size,

    |             size + align               |
    ------------------------------------------
 ptr

input param *align* could be 1M, or 2M, or host page size. After
QEMU_ALIGN_UP, offset will >= 0

2nd mmap use flag MAP_FIXED, then it return ptr+offset, or else fail.
If it success, then we will have something like:

    | offset |          size             |
    --------------------------------------
 ptr      ptr1

*ptr1* is what we really want to return, it equals ptr+offset.

Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
---
 util/mmap-alloc.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)
diff mbox

Patch

diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
index d713a72..2f55f5e 100644
--- a/util/mmap-alloc.c
+++ b/util/mmap-alloc.c
@@ -84,22 +84,20 @@  void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
         return MAP_FAILED;
     }
 
-    ptr += offset;
-    total -= offset;
-
     if (offset > 0) {
-        munmap(ptr - offset, offset);
+        munmap(ptr, offset);
     }
 
     /*
      * Leave a single PROT_NONE page allocated after the RAM block, to serve as
      * a guard page guarding against potential buffer overflows.
      */
+    total -= offset;
     if (total > size + getpagesize()) {
-        munmap(ptr + size + getpagesize(), total - size - getpagesize());
+        munmap(ptr1 + size + getpagesize(), total - size - getpagesize());
     }
 
-    return ptr;
+    return ptr1;
 }
 
 void qemu_ram_munmap(void *ptr, size_t size)