filestore: only warn about disk write cache on kernels <2.6.33

Signed-off-by: Sage Weil <sage@newdream.net>

diff --git a/src/os/FileJournal.cc b/src/os/FileJournal.cc
index c779f0f87817b91efd6b7a1bab45db7ad83a9832..377259f4f227d40c4aa67a4adf686289dad7a6d5 100644 (file)
--- a/src/os/FileJournal.cc
+++ b/src/os/FileJournal.cc
@@ -171,16 +171,33 @@ void FileJournal::_check_disk_write_cache() const
     int on;
     if (sscanf(s, " write-caching =  %d", &on) == 1) {
       if (on) {
-       dout(0) << "WARNING: disk write cache is ON; journaling will not be reliable" << dendl;
-       dout(0) << "         on kernels prior to 2.6.33 (recent kernels are safe)" << dendl;
-       dout(0) << "         disable with 'hdparm -W 0 " << fn << "'" << dendl;
-       cout << TEXT_RED
-            << " ** WARNING: disk write cache is ON on " << fn << ".\n"
-            << "    Journaling will not be reliable on kernels prior to 2.6.33\n"
-            << "    (recent kernels are safe).  You can disable the write cache with\n"
-            << "    'hdparm -W 0 " << fn << "'"
-            << TEXT_NORMAL
-            << std::endl;
+
+       // check kenrel version
+       char buf[40];
+       int fd = ::open("/proc/version", O_RDONLY);
+       ::read(fd, buf, 39);
+       buf[39] = 0;
+       ::close(fd);
+
+       int b, c;
+       int r = sscanf(buf, "Linux version 2.%d.%d", &b, &c);
+       dout(0) << " kernel version is 2." << b << "." << c << dendl;
+       if (r == 2 &&
+           b >= 6 &&
+           c >= 33) {
+         // a-ok
+       } else {
+         dout(0) << "WARNING: disk write cache is ON; journaling will not be reliable" << dendl;
+         dout(0) << "         on kernels prior to 2.6.33 (recent kernels are safe)" << dendl;
+         dout(0) << "         disable with 'hdparm -W 0 " << fn << "'" << dendl;
+         cout << TEXT_RED
+              << " ** WARNING: disk write cache is ON on " << fn << ".\n"
+              << "    Journaling will not be reliable on kernels prior to 2.6.33\n"
+              << "    (recent kernels are safe).  You can disable the write cache with\n"
+              << "    'hdparm -W 0 " << fn << "'"
+              << TEXT_NORMAL
+              << std::endl;
+       }
       } else {
        dout(10) << "_open disk write cache is off (good) on " << fn << dendl;
       }