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Re: [libvirt] [PATCH 6/8 v8] qemu: Check if the shared disk's cdbfilter conflicts with others



On 2012年12月15日 05:49, Eric Blake wrote:
On 12/14/2012 08:44 AM, Osier Yang wrote:
This prevents the domain starting if the shared disk's setting
conflicts with other active domain(s), E.g. A domain with
"cdbfilter" set as "yes", however, another active domain is using
it set as "no".
---
  src/qemu/qemu_process.c |   51 +++++++++++++++++++++++++++++++++++++++++++++++
  src/qemu/qemu_process.h |    2 +
  2 files changed, 53 insertions(+), 0 deletions(-)

diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index bcea0ff..1e2baac 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -3385,6 +3385,54 @@ qemuProcessReconnectAll(virConnectPtr conn, virQEMUDriverPtr driver)
      virHashForEach(driver->domains.objs, qemuProcessReconnectHelper,&data);
  }

+/* Check if a shared disk's setting conflicts with the conf
+ * used by other domain(s). Currently only checks the cdbfilter
+ * setting.

Probably worth documenting that this function should only be called on
disks with a block device source...

+ *
+ * Returns 0 if no conflicts, otherwise returns -1.
+ */
+int
+qemuCheckSharedDisk(virHashTablePtr sharedDisks,
+                    virDomainDiskDefPtr disk)
+{
+    int val;
+    size_t *ref = NULL;
+    char *key = NULL;
+    int ret = 0;
+
+    if (!(key = qemuGetSharedDiskKey(disk->src)))
+        return -1;

since you error out on regular files.  (You correctly obey that
restriction for now, but without documentation, it might be possible to
reuse this function from the wrong context in a future patch.)

Okay.


+
+    /* It can't be conflict if no other domain is
+     * is sharing it.
+     */
+    if (!(ref = virHashLookup(sharedDisks, key)))
+        goto cleanup;
+
+    if (ref == (void *)0x1)
+        goto cleanup;
+
+    if (virGetDeviceUnprivSGIO(disk->src, NULL,&val)<  0) {
+        ret = -1;
+        goto cleanup;
+    }
+
+    if ((val == 0&&
+         disk->cdbfilter == VIR_DOMAIN_DISK_CDB_FILTER_YES) ||

Does this do the right thing if disk->cdbfilter ==
VIR_DOMAIN_DISK_CDB_FILTER_DEFAULT (that is, the user didn't specify the
cdbfilter attribute)?

Oh, right, there is problem here. It should be like:

    if (!disk->cdbfilter)
         return 0

in the early beginnng of the function.

As VIR_DOMAIN_DISK_CDB_FILTER_DEFAULT implies it doesn't care
about the SG_IO setting. I.E, It lives with what current setting
is.


Again, this area of code may need tweaks if you
take my suggestion of making rawio a three-value enum.

+        (val == 1&&
+         disk->cdbfilter == VIR_DOMAIN_DISK_CDB_FILTER_NO))
+        goto cleanup;
+
+    virReportError(VIR_ERR_INTERNAL_ERROR,
+                   _("cdbfilter of shared disk '%s' conflicts with other "
+                     "active domains"), disk->src);

INTERNAL_ERROR is wrong.  I think VIR_ERR_OPERATION_INVALID fits better.

Okay, the error number is always fuzzy to use. :-)


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