[Qemu-devel] [PATCH v2 05/42] ivshmem-server: Don't overload POSIX shmem and file name

[Markus Armbruster <armbru@redhat.com>]

Option -m NAME is interpreted as directory name if we can statfs() it
and its on hugetlbfs.  Else it's interpreted as POSIX shared memory
object name.  This is nuts.

Always interpret -m as directory.  Create new -M for POSIX shared
memory.  Last of -m or -M wins.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 contrib/ivshmem-server/ivshmem-server.c | 56 ++++++---------------------------
 contrib/ivshmem-server/ivshmem-server.h |  4 ++-
 contrib/ivshmem-server/main.c           | 15 +++++++--
 tests/ivshmem-test.c                    |  2 +-
 4 files changed, 27 insertions(+), 50 deletions(-)

diff --git a/contrib/ivshmem-server/ivshmem-server.c b/contrib/ivshmem-server/ivshmem-server.c
index bfd0fad..41aee35 100644
--- a/contrib/ivshmem-server/ivshmem-server.c
+++ b/contrib/ivshmem-server/ivshmem-server.c
@@ -12,9 +12,6 @@
 #include <sys/mman.h>
 #include <sys/socket.h>
 #include <sys/un.h>
-#ifdef CONFIG_LINUX
-#include <sys/vfs.h>
-#endif
 
 #include "ivshmem-server.h"
 
@@ -257,7 +254,8 @@ ivshmem_server_ftruncate(int fd, unsigned shmsize)
 /* Init a new ivshmem server */
 int
 ivshmem_server_init(IvshmemServer *server, const char *unix_sock_path,
-                    const char *shm_path, size_t shm_size, unsigned n_vectors,
+                    const char *shm_path, bool use_shm_open,
+                    size_t shm_size, unsigned n_vectors,
                     bool verbose)
 {
     int ret;
@@ -278,6 +276,7 @@ ivshmem_server_init(IvshmemServer *server, const char *unix_sock_path,
         return -1;
     }
 
+    server->use_shm_open = use_shm_open;
     server->shm_size = shm_size;
     server->n_vectors = n_vectors;
 
@@ -286,31 +285,6 @@ 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)
@@ -319,27 +293,17 @@ ivshmem_server_start(IvshmemServer *server)
     int shm_fd, sock_fd, ret;
 
     /* open shm file */
-#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) {
+    if (server->use_shm_open) {
+        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);
+    } else {
         gchar *filename = g_strdup_printf("%s/ivshmem.XXXXXX", server->shm_path);
-        IVSHMEM_SERVER_DEBUG(server, "Using hugepages: %s\n", server->shm_path);
+        IVSHMEM_SERVER_DEBUG(server, "Using file-backed shared memory: %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) {
diff --git a/contrib/ivshmem-server/ivshmem-server.h b/contrib/ivshmem-server/ivshmem-server.h
index e9de8a3..3851639 100644
--- a/contrib/ivshmem-server/ivshmem-server.h
+++ b/contrib/ivshmem-server/ivshmem-server.h
@@ -66,6 +66,7 @@ typedef struct IvshmemServer {
     char unix_sock_path[PATH_MAX];   /**< path to unix socket */
     int sock_fd;                     /**< unix sock file descriptor */
     char shm_path[PATH_MAX];         /**< path to shm */
+    bool use_shm_open;
     size_t shm_size;                 /**< size of shm */
     int shm_fd;                      /**< shm file descriptor */
     unsigned n_vectors;              /**< number of vectors */
@@ -89,7 +90,8 @@ typedef struct IvshmemServer {
  */
 int
 ivshmem_server_init(IvshmemServer *server, const char *unix_sock_path,
-                    const char *shm_path, size_t shm_size, unsigned n_vectors,
+                    const char *shm_path, bool use_shm_open,
+                    size_t shm_size, unsigned n_vectors,
                     bool verbose);
 
 /**
diff --git a/contrib/ivshmem-server/main.c b/contrib/ivshmem-server/main.c
index e9b4388..2795db5 100644
--- a/contrib/ivshmem-server/main.c
+++ b/contrib/ivshmem-server/main.c
@@ -29,6 +29,7 @@ typedef struct IvshmemServerArgs {
     const char *pid_file;
     const char *unix_socket_path;
     const char *shm_path;
+    bool use_shm_open;
     uint64_t shm_size;
     unsigned n_vectors;
 } IvshmemServerArgs;
@@ -44,8 +45,9 @@ ivshmem_server_usage(const char *progname)
            "     default " IVSHMEM_SERVER_DEFAULT_PID_FILE "\n"
            "  -S <unix_socket_path>: path to the unix socket to listen to\n"
            "     default " IVSHMEM_SERVER_DEFAULT_UNIX_SOCK_PATH "\n"
-           "  -m <shm_path>: POSIX shared memory object name or a hugetlbfs mount point\n"
+           "  -M <name>: POSIX shared memory object to use\n"
            "     default " IVSHMEM_SERVER_DEFAULT_SHM_PATH "\n"
+           "  -m <dirname>: where to create shared memory\n"
            "  -l <size>: size of shared memory in bytes\n"
            "     suffixes K, M and G can be used, e.g. 1K means 1024\n"
            "     default %u\n"
@@ -76,6 +78,7 @@ ivshmem_server_parse_args(IvshmemServerArgs *args, int argc, char *argv[])
                        "p:" /* pid_file */
                        "S:" /* unix_socket_path */
                        "m:" /* shm_path */
+                       "M:" /* shm_path */
                        "l:" /* shm_size */
                        "n:" /* n_vectors */
                       )) != -1) {
@@ -102,8 +105,14 @@ ivshmem_server_parse_args(IvshmemServerArgs *args, int argc, char *argv[])
             args->unix_socket_path = optarg;
             break;
 
+        case 'M': /* shm_path */
+            args->shm_path = optarg;
+            args->use_shm_open = true;
+            break;
+
         case 'm': /* shm_path */
             args->shm_path = optarg;
+            args->use_shm_open = false;
             break;
 
         case 'l': /* shm_size */
@@ -199,6 +208,7 @@ main(int argc, char *argv[])
         .pid_file = IVSHMEM_SERVER_DEFAULT_PID_FILE,
         .unix_socket_path = IVSHMEM_SERVER_DEFAULT_UNIX_SOCK_PATH,
         .shm_path = IVSHMEM_SERVER_DEFAULT_SHM_PATH,
+        .use_shm_open = true,
         .shm_size = IVSHMEM_SERVER_DEFAULT_SHM_SIZE,
         .n_vectors = IVSHMEM_SERVER_DEFAULT_N_VECTORS,
     };
@@ -226,7 +236,8 @@ main(int argc, char *argv[])
     }
 
     /* init the ivshms structure */
-    if (ivshmem_server_init(&server, args.unix_socket_path, args.shm_path,
+    if (ivshmem_server_init(&server, args.unix_socket_path,
+                            args.shm_path, args.use_shm_open,
                             args.shm_size, args.n_vectors, args.verbose) < 0) {
         fprintf(stderr, "cannot init server\n");
         goto err;
diff --git a/tests/ivshmem-test.c b/tests/ivshmem-test.c
index e184c67..4efa433 100644
--- a/tests/ivshmem-test.c
+++ b/tests/ivshmem-test.c
@@ -294,7 +294,7 @@ static void test_ivshmem_server(bool msi)
     guint64 end_time = g_get_monotonic_time() + 5 * G_TIME_SPAN_SECOND;
 
     memset(tmpshmem, 0x42, TMPSHMSIZE);
-    ret = ivshmem_server_init(&server, tmpserver, tmpshm,
+    ret = ivshmem_server_init(&server, tmpserver, tmpshm, true,
                               TMPSHMSIZE, nvectors,
                               g_test_verbose());
     g_assert_cmpint(ret, ==, 0);
-- 
2.4.3