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Re: [libvirt] [PATCH 2/4] Avoid create/unlink with block devs used for QEMU save



On 04/22/2010 07:43 AM, Daniel P. Berrange wrote:
It is possible to use block devices with domain save/restore. Upon
failure QEMU unlinks the path being saved to. This isn't good when
it is a block device !

* src/qemu/qemu_driver.c: Don't unlink block devices if save fails
---
  src/qemu/qemu_driver.c |   22 ++++++++++++++++++++--
  1 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 91fe963..41a516c 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -4787,6 +4787,8 @@ static int qemudDomainSaveFlag(virDomainPtr dom, const char *path,
      int rc;
      virDomainEventPtr event = NULL;
      qemuDomainObjPrivatePtr priv;
+    struct stat sb;
+    int is_reg = 0;

      memset(&header, 0, sizeof(header));
      memcpy(header.magic, QEMUD_SAVE_MAGIC, sizeof(header.magic));
@@ -4840,6 +4842,21 @@ static int qemudDomainSaveFlag(virDomainPtr dom, const char *path,
      }
      header.xml_len = strlen(xml) + 1;

+    /* path might be a pre-existing block dev, in which case
+     * we need to skip the create step, and also avoid unlink
+     * in the failure case */
+    if (stat(path,&sb)<  0) {
+        if (errno != ENOENT) {

In the case of a target on a root-squashed NFS server, this stat() will fail if the directory is not marked as w+rx. In this case, it will return EACCES. Changing the if to also check for (errno != EACCES) allows it to pass this point (and shouldn't hurt in any other circumstances). I tried it with this small modification, and save/restore to root-squash NFS works properly.



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