On Thu, Apr 18, 2019 at 07:05:16PM -0300, Eduardo Habkost wrote:
> Hi,
>
> I found out that this series missed QEMU 4.0 and I was going to
> queue for 4.1, but unfortunately this patch conflicts with:
>
> commit 2044c3e7116eeac0449dcb4a4130cc8f8b9310da
> Author: Murilo Opsfelder Araujo <muri...@linux.ibm.com>
> Date: Wed Jan 30 21:36:04 2019 -0200
>
> mmap-alloc: unfold qemu_ram_mmap()
[...]
> On Fri, Feb 08, 2019 at 06:11:11PM +0800, Zhang, Yi wrote:
> > From: Zhang Yi <yi.z.zh...@linux.intel.com>
> >
> > When a file supporting DAX is used as vNVDIMM backend, mmap it with
> > MAP_SYNC flag in addition which can ensure file system metadata
> > synced in each guest writes to the backend file, without other QEMU
> > actions (e.g., periodic fsync() by QEMU).
> >
> > Current, We have below different possible use cases:
> >
> > 1. pmem=on is set, shared=on is set, MAP_SYNC supported:
> > a: backend is a dax supporting file.
> > - MAP_SYNC will active.
> > b: backend is not a dax supporting file.
> > - mmap will trigger a warning. then MAP_SYNC flag will be ignored
> >
> > 2. The rest of cases:
> > - we will never pass the MAP_SYNC to mmap2
> >
> > Signed-off-by: Haozhong Zhang <haozhong.zh...@intel.com>
> > Signed-off-by: Zhang Yi <yi.z.zh...@linux.intel.com>
Untested patch rebase is below. Can Intel help test it and
submit v14?
Signed-off-by: Haozhong Zhang <haozhong.zh...@intel.com>
Signed-off-by: Zhang Yi <yi.z.zh...@linux.intel.com>
[ehabkost: Rebased patch to latest code on master]
Signed-off-by: Eduardo Habkost <ehabk...@redhat.com>
---
util/mmap-alloc.c | 41 +++++++++++++++++++++++++++++++++++++++--
1 file changed, 39 insertions(+), 2 deletions(-)
diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
index 9713f4b960..7063a44c7d 100644
--- a/util/mmap-alloc.c
+++ b/util/mmap-alloc.c
@@ -10,6 +10,13 @@
* later. See the COPYING file in the top-level directory.
*/
+#ifdef CONFIG_LINUX
+#include <linux/mman.h>
+#else /* !CONFIG_LINUX */
+#define MAP_SYNC 0x0
+#define MAP_SHARED_VALIDATE 0x0
+#endif /* CONFIG_LINUX */
+
#include "qemu/osdep.h"
#include "qemu/mmap-alloc.h"
#include "qemu/host-utils.h"
@@ -82,6 +89,7 @@ void *qemu_ram_mmap(int fd,
bool is_pmem)
{
int flags;
+ int map_sync_flags = 0;
int guardfd;
size_t offset;
size_t pagesize;
@@ -132,10 +140,39 @@ void *qemu_ram_mmap(int fd,
flags = MAP_FIXED;
flags |= fd == -1 ? MAP_ANONYMOUS : 0;
flags |= shared ? MAP_SHARED : MAP_PRIVATE;
+ if (shared && is_pmem) {
+ map_sync_flags = MAP_SYNC | MAP_SHARED_VALIDATE;
+ }
offset = QEMU_ALIGN_UP((uintptr_t)guardptr, align) - (uintptr_t)guardptr;
- ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE, flags, fd, 0);
-
+ ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE,
+ flags | map_sync_flags, fd, 0);
+
+ if (ptr == MAP_FAILED && map_sync_flags) {
+ if (errno == ENOTSUP) {
+ char *proc_link, *file_name;
+ int len;
+ proc_link = g_strdup_printf("/proc/self/fd/%d", fd);
+ file_name = g_malloc0(PATH_MAX);
+ len = readlink(proc_link, file_name, PATH_MAX - 1);
+ if (len < 0) {
+ len = 0;
+ }
+ file_name[len] = '\0';
+ fprintf(stderr, "Warning: requesting persistence across crashes "
+ "for backend file %s failed. Proceeding without "
+ "persistence, data might become corrupted in case of host "
+ "crash.\n", file_name);
+ g_free(proc_link);
+ g_free(file_name);
+ }
+ /*
+ * if map failed with MAP_SHARED_VALIDATE | MAP_SYNC,
+ * we will remove these flags to handle compatibility.
+ */
+ ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE,
+ flags, fd, 0);
+ }
if (ptr == MAP_FAILED) {
munmap(guardptr, total);
return MAP_FAILED;
--
2.18.0.rc1.1.g3f1ff2140
