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Re: [Qemu-devel] [PATCH v3 11/32] hostmem-file: use whole file size if p


From: Vladimir Sementsov-Ogievskiy
Subject: Re: [Qemu-devel] [PATCH v3 11/32] hostmem-file: use whole file size if possible
Date: Tue, 13 Oct 2015 14:50:01 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.8.0

On 11.10.2015 06:52, Xiao Guangrong wrote:
Use the whole file size if @size is not specified which is useful
if we want to directly pass a file to guest

Signed-off-by: Xiao Guangrong <address@hidden>
---
  backends/hostmem-file.c | 47 +++++++++++++++++++++++++++++++++++++++++++----
  1 file changed, 43 insertions(+), 4 deletions(-)

diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index 9097a57..adf2835 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -9,6 +9,9 @@
   * This work is licensed under the terms of the GNU GPL, version 2 or later.
   * See the COPYING file in the top-level directory.
   */
+#include <sys/ioctl.h>
+#include <linux/fs.h>
+
  #include "qemu-common.h"
  #include "sysemu/hostmem.h"
  #include "sysemu/sysemu.h"
@@ -33,20 +36,56 @@ struct HostMemoryBackendFile {
      char *mem_path;
  };
+static uint64_t get_file_size(const char *file)
+{
+    struct stat stat_buf;
+    uint64_t size = 0;
+    int fd;
+
+    fd = open(file, O_RDONLY);
+    if (fd < 0) {
+        return 0;
+    }
+
+    if (stat(file, &stat_buf) < 0) {
+        goto exit;
+    }
+
+    if ((S_ISBLK(stat_buf.st_mode)) && !ioctl(fd, BLKGETSIZE64, &size)) {
+        goto exit;
+    }
+
+    size = lseek(fd, 0, SEEK_END);
+    if (size == -1) {
+        size = 0;
+    }
+exit:
+    close(fd);
+    return size;
+}
+
  static void
  file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
  {
      HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(backend);
- if (!backend->size) {
-        error_setg(errp, "can't create backend with size 0");
-        return;
-    }
      if (!fb->mem_path) {
          error_setg(errp, "mem-path property not set");
          return;
      }
+ if (!backend->size) {
+        /*
+         * use the whole file size if @size is not specified.
+         */
+        backend->size = get_file_size(fb->mem_path);
+    }
+
+    if (!backend->size) {
+        error_setg(errp, "can't create backend with size 0");
+        return;
+    }

in case of any error in get_file_size (open, stat, lseek) it will write about "backend with size 0" which may be not appropriate..

+
      backend->force_prealloc = mem_prealloc;
      memory_region_init_ram_from_file(&backend->mr, OBJECT(backend),
                                   object_get_canonical_path(OBJECT(backend)),


--
Best regards,
Vladimir
* now, @virtuozzo.com instead of @parallels.com. Sorry for this inconvenience.




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