ivshmem-server: fix hugetlbfs support

As pointed out on the ML by Andrew Jones, glibc no longer permits
creating POSIX shm on hugetlbfs directly. When given a hugetlbfs path,
create a shareable file there.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

contrib/ivshmem-server/ivshmem-server.c

@@ -12,6 +12,9 @@
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <sys/un.h>
+#ifdef CONFIG_LINUX
+#include <sys/vfs.h>
+#endif
 
 #include "ivshmem-server.h"
 
@@ -271,6 +274,31 @@ ivshmem_server_init(IvshmemServer *server, const char *unix_sock_path,
     return 0;
 }
 
+#ifdef CONFIG_LINUX
+
+#define HUGETLBFS_MAGIC       0x958458f6
+
+static long gethugepagesize(const char *path)
+{
+    struct statfs fs;
+    int ret;
+
+    do {
+        ret = statfs(path, &fs);
+    } while (ret != 0 && errno == EINTR);
+
+    if (ret != 0) {
+        return -1;
+    }
+
+    if (fs.f_type != HUGETLBFS_MAGIC) {
+        return -1;
+    }
+
+    return fs.f_bsize;
+}
+#endif
+
 /* open shm, create and bind to the unix socket */
 int
 ivshmem_server_start(IvshmemServer *server)
@@ -279,7 +307,29 @@ ivshmem_server_start(IvshmemServer *server)
     int shm_fd, sock_fd, ret;
 
     /* open shm file */
-    shm_fd = shm_open(server->shm_path, O_CREAT|O_RDWR, S_IRWXU);
+#ifdef CONFIG_LINUX
+    long hpagesize;
+
+    hpagesize = gethugepagesize(server->shm_path);
+    if (hpagesize < 0 && errno != ENOENT) {
+        IVSHMEM_SERVER_DEBUG(server, "cannot stat shm file %s: %s\n",
+                             server->shm_path, strerror(errno));
+    }
+
+    if (hpagesize > 0) {
+        gchar *filename = g_strdup_printf("%s/ivshmem.XXXXXX", server->shm_path);
+        IVSHMEM_SERVER_DEBUG(server, "Using hugepages: %s\n", server->shm_path);
+        shm_fd = mkstemp(filename);
+        unlink(filename);
+        g_free(filename);
+    } else
+#endif
+    {
+        IVSHMEM_SERVER_DEBUG(server, "Using POSIX shared memory: %s\n",
+                             server->shm_path);
+        shm_fd = shm_open(server->shm_path, O_CREAT|O_RDWR, S_IRWXU);
+    }
+
     if (shm_fd < 0) {
         fprintf(stderr, "cannot open shm file %s: %s\n", server->shm_path,
                 strerror(errno));

contrib/ivshmem-server/ivshmem-server.h

@@ -82,8 +82,7 @@ typedef struct IvshmemServer {
  * @server:         A pointer to an uninitialized IvshmemServer structure
  * @unix_sock_path: The pointer to the unix socket file name
  * @shm_path:       Path to the shared memory. The path corresponds to a POSIX
- *                  shm name. To use a real file, for instance in a hugetlbfs,
- *                  it is possible to use /../../abspath/to/file.
+ *                  shm name or a hugetlbfs mount point.
  * @shm_size:       Size of shared memory
  * @n_vectors:      Number of interrupt vectors per client
  * @verbose:        True to enable verbose mode

contrib/ivshmem-server/main.c

@@ -47,9 +47,8 @@ ivshmem_server_usage(const char *name, int code)
                     "     to listen to.\n"
                     "     Default=%s\n", IVSHMEM_SERVER_DEFAULT_UNIX_SOCK_PATH);
     fprintf(stderr, "  -m <shm_path>: path to the shared memory.\n"
-                    "     The path corresponds to a POSIX shm name. To use a\n"
-                    "     real file, for instance in a hugetlbfs, use\n"
-                    "     /../../abspath/to/file.\n"
+                    "     The path corresponds to a POSIX shm name or a\n"
+                    "     hugetlbfs mount point.\n"
                     "     default=%s\n", IVSHMEM_SERVER_DEFAULT_SHM_PATH);
     fprintf(stderr, "  -l <size>: size of shared memory in bytes. The suffix\n"
                     "     K, M and G can be used (ex: 1K means 1024).\n"