[libvirt] [PATCH] qemu driver: use lseek64 for setting position in logfile

[Stefan Berger]

While doing some testing with Qemu and creating huge logfiles I 
encountered the case where the VM could not start anymore due to the 
lseek() to the end of the Qemu VM's log file failing. The patch below 
replaces the two occurrences of lseek() in the relevant path with 
lseek64() and solves this problem. It may be a good idea to look at 
other occurrences of lseek() as well whether they should be replaced. 
off_t is 8 bytes long (64 bit), so it doesn't need to be replaced with 
the explicit off64_t.

To reproduce this error, you could do the following:

dd if=/dev/zero of=/var/log/libvirt/qemu/<name of VM>.log bs=1024 
count=$((1024*2048))

and you should get an error like this:

error: Failed to start domain <name of VM>
error: Unable to seek to -2147482651 in /var/log/libvirt/qemu/<name of 
VM>.log: Success

Signed-off-by: Stefan Berger <stefanb at us.ibm.com>

---
  src/qemu/qemu_driver.c |    6 +++---
  1 file changed, 3 insertions(+), 3 deletions(-)

Index: libvirt-acl/src/qemu/qemu_driver.c
===================================================================
--- libvirt-acl.orig/src/qemu/qemu_driver.c
+++ libvirt-acl/src/qemu/qemu_driver.c
@@ -238,7 +238,7 @@ qemudLogReadFD(const char* logDir, const
          VIR_FREE(logfile);
          return -1;
      }
-    if (pos < 0 || lseek(fd, pos, SEEK_SET) < 0) {
+    if (pos < 0 || lseek64(fd, pos, SEEK_SET) < 0) {
          virReportSystemError(pos < 0 ? 0 : errno,
                               _("Unable to seek to %lld in %s"),
                               (long long) pos, logfile);
@@ -2624,7 +2624,7 @@ static int qemudStartVMDaemon(virConnect
                                enum virVMOperationType vmop) {
      int ret;
      unsigned long long qemuCmdFlags;
-    int pos = -1;
+    off_t pos = -1;
      char ebuf[1024];
      char *pidfile = NULL;
      int logfile = -1;
@@ -2839,7 +2839,7 @@ static int qemudStartVMDaemon(virConnect

      virCommandWriteArgLog(cmd, logfile);

-    if ((pos = lseek(logfile, 0, SEEK_END)) < 0)
+    if ((pos = lseek64(logfile, 0, SEEK_END)) < 0)
          VIR_WARN("Unable to seek to end of logfile: %s",
                   virStrerror(errno, ebuf, sizeof ebuf));