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Re: [Qemu-devel] [PATCH v6 07/33] util: introduce qemu_file_get_page_siz


From: Xiao Guangrong
Subject: Re: [Qemu-devel] [PATCH v6 07/33] util: introduce qemu_file_get_page_size()
Date: Sat, 31 Oct 2015 16:09:56 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0



On 10/30/2015 11:54 PM, Eduardo Habkost wrote:
On Fri, Oct 30, 2015 at 01:56:01PM +0800, Xiao Guangrong wrote:
There are three places use the some logic to get the page size on
the file path or file fd

This patch introduces qemu_file_get_page_size() to unify the code

Signed-off-by: Xiao Guangrong <address@hidden>
[...]
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 914cef5..ad94c5a 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -360,6 +360,22 @@ static size_t fd_getpagesize(int fd)
      return getpagesize();
  }

+size_t qemu_file_get_page_size(const char *path)
+{
+    size_t size = 0;
+    int fd = qemu_open(path, O_RDONLY);
+
+    if (fd < 0) {
+        fprintf(stderr, "Could not open %s.\n", path);
+        goto exit;

Have you considered using a Error** argument here?

+    }
+
+    size = fd_getpagesize(fd);
+    qemu_close(fd);
+exit:
+    return size;
+}
+
diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
index ac70f08..c661f1c 100644
--- a/target-ppc/kvm.c
+++ b/target-ppc/kvm.c
@@ -308,28 +308,13 @@ static void kvm_get_smmu_info(PowerPCCPU *cpu, struct 
kvm_ppc_smmu_info *info)

  static long gethugepagesize(const char *mem_path)
  {
-    struct statfs fs;
-    int ret;
-
-    do {
-        ret = statfs(mem_path, &fs);
-    } while (ret != 0 && errno == EINTR);
+    long size = qemu_file_get_page_size(mem_path);

-    if (ret != 0) {
-        fprintf(stderr, "Couldn't statfs() memory path: %s\n",
-                strerror(errno));
+    if (!size) {
          exit(1);
      }

-#define HUGETLBFS_MAGIC       0x958458f6
-
-    if (fs.f_type != HUGETLBFS_MAGIC) {
-        /* Explicit mempath, but it's ordinary pages */
-        return getpagesize();
-    }
-
-    /* It's hugepage, return the huge page size */
-    return fs.f_bsize;
+    return size;
  }

Why are you changing target-ppc/kvm.c:gethugepagesize() to use the new
funtion, but not the copy at exec.c? To make it simpler, we could
eliminate both gethugepagesize() functions completely and replace them
with qemu_file_get_page_size() calls (maybe as part of this patch, maybe
in a separate patch, I'm not sure).


The gethugepagesize() in exec.c will be eliminated in later patch :).

And the gethugepagesize() in ppc platform has error handling logic
and has multiple caller. It's not so bad to keep it.





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