[v3,19/34] memory: move preallocation code out of exec.c

diff --git a/exec.c b/exec.c
index 1e51b2f..710e025 100644
--- a/exec.c
+++ b/exec.c
@@ -1012,13 +1012,6 @@  static long gethugepagesize(const char *path)
     return fs.f_bsize;
 }
 
-static sigjmp_buf sigjump;
-
-static void sigbus_handler(int signal)
-{
-    siglongjmp(sigjump, 1);
-}
-
 static void *file_ram_alloc(RAMBlock *block,
                             ram_addr_t memory,
                             const char *path,
@@ -1088,42 +1081,7 @@  static void *file_ram_alloc(RAMBlock *block,
     }
 
     if (mem_prealloc) {
-        int ret, i;
-        struct sigaction act, oldact;
-        sigset_t set, oldset;
-
-        memset(&act, 0, sizeof(act));
-        act.sa_handler = &sigbus_handler;
-        act.sa_flags = 0;
-
-        ret = sigaction(SIGBUS, &act, &oldact);
-        if (ret) {
-            perror("file_ram_alloc: failed to install signal handler");
-            exit(1);
-        }
-
-        /* unblock SIGBUS */
-        sigemptyset(&set);
-        sigaddset(&set, SIGBUS);
-        pthread_sigmask(SIG_UNBLOCK, &set, &oldset);
-
-        if (sigsetjmp(sigjump, 1)) {
-            fprintf(stderr, "file_ram_alloc: failed to preallocate pages\n");
-            exit(1);
-        }
-
-        /* MAP_POPULATE silently ignores failures */
-        for (i = 0; i < (memory/hpagesize); i++) {
-            memset(area + (hpagesize*i), 0, 1);
-        }
-
-        ret = sigaction(SIGBUS, &oldact, NULL);
-        if (ret) {
-            perror("file_ram_alloc: failed to reinstall signal handler");
-            exit(1);
-        }
-
-        pthread_sigmask(SIG_SETMASK, &oldset, NULL);
+        os_mem_prealloc(fd, area, memory);
     }
 
     block->fd = fd;
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index ffb2966..9c1a119 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -251,4 +251,6 @@  void qemu_init_auxval(char **envp);
 
 void qemu_set_tty_echo(int fd, bool echo);
 
+void os_mem_prealloc(int fd, char *area, size_t sz);
+
 #endif
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 8e9c770..a22c97d 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -46,6 +46,7 @@  extern int daemon(int, int);
 #else
 #  define QEMU_VMALLOC_ALIGN getpagesize()
 #endif
+#define HUGETLBFS_MAGIC       0x958458f6
 
 #include <termios.h>
 #include <unistd.h>
@@ -58,9 +59,12 @@  extern int daemon(int, int);
 #include "qemu/sockets.h"
 #include <sys/mman.h>
 #include <libgen.h>
+#include <setjmp.h>
+#include <sys/signal.h>
 
 #ifdef CONFIG_LINUX
 #include <sys/syscall.h>
+#include <sys/vfs.h>
 #endif
 
 #ifdef __FreeBSD__
@@ -332,3 +336,72 @@  char *qemu_get_exec_dir(void)
 {
     return g_strdup(exec_dir);
 }
+
+static sigjmp_buf sigjump;
+
+static void sigbus_handler(int signal)
+{
+    siglongjmp(sigjump, 1);
+}
+
+static size_t fd_getpagesize(int fd)
+{
+#ifdef CONFIG_LINUX
+    struct statfs fs;
+    int ret;
+
+    if (fd != -1) {
+        do {
+            ret = fstatfs(fd, &fs);
+        } while (ret != 0 && errno == EINTR);
+
+        if (ret == 0 && fs.f_type == HUGETLBFS_MAGIC) {
+            return fs.f_bsize;
+        }
+    }
+#endif
+
+    return getpagesize();
+}
+
+void os_mem_prealloc(int fd, char *area, size_t memory)
+{
+    int ret, i;
+    struct sigaction act, oldact;
+    sigset_t set, oldset;
+    size_t hpagesize = fd_getpagesize(fd);
+
+    memset(&act, 0, sizeof(act));
+    act.sa_handler = &sigbus_handler;
+    act.sa_flags = 0;
+
+    ret = sigaction(SIGBUS, &act, &oldact);
+    if (ret) {
+        perror("file_ram_alloc: failed to install signal handler");
+        exit(1);
+    }
+
+    /* unblock SIGBUS */
+    sigemptyset(&set);
+    sigaddset(&set, SIGBUS);
+    pthread_sigmask(SIG_UNBLOCK, &set, &oldset);
+
+    if (sigsetjmp(sigjump, 1)) {
+        fprintf(stderr, "file_ram_alloc: failed to preallocate pages\n");
+        exit(1);
+    }
+
+    /* MAP_POPULATE silently ignores failures */
+    memory = (memory + hpagesize - 1) & -hpagesize;
+    for (i = 0; i < (memory/hpagesize); i++) {
+        memset(area + (hpagesize*i), 0, 1);
+    }
+
+    ret = sigaction(SIGBUS, &oldact, NULL);
+    if (ret) {
+        perror("file_ram_alloc: failed to reinstall signal handler");
+        exit(1);
+    }
+
+    pthread_sigmask(SIG_SETMASK, &oldset, NULL);
+}