[Xen-API] [PATCH] cope better with failures while attaching a disk to a VM

[David Scott <dave.scott@xxxxxxxxxxxxx>]

# HG changeset patch
# User David Scott <dave.scott@xxxxxxxxxxxxx>
# Date 1270636506 -3600
# Node ID 9dd35e413e35877280587431cd367f81f4979fa5
# Parent  82aec6e8c78ee0ca31c5bfe887b57484cfab0995
CA-39745: watch /local/domain/%d/error/backend/vbd/%d/%d/error for informative 
errors such as "2 creating vbd structure". This prevents us timing out after 20 
minutes if something goes wrong with a blkback device.

A further patch will be needed to provide some decent error diagnosis.

Signed-off-by: David Scott <dave.scott@xxxxxxxxxxxxx>

diff -r 82aec6e8c78e -r 9dd35e413e35 ocaml/xenops/hotplug.ml
--- a/ocaml/xenops/hotplug.ml   Wed Apr 07 11:34:09 2010 +0100
+++ b/ocaml/xenops/hotplug.ml   Wed Apr 07 11:35:06 2010 +0100
@@ -78,6 +78,10 @@
 let tapdisk_error_node ~xs (x: device) = 
   sprintf "%s/backend/%s/%d/%d/tapdisk-error" (xs.Xs.getdomainpath 
x.backend.domid) (string_of_kind x.backend.kind) x.frontend.domid 
x.frontend.devid
 
+(* CA-39745: node written to by blkback to report an error (eg opening an 
empty CDROM drive) *)
+let blkback_error_node ~xs (x: device) = 
+  sprintf "%s/error/backend/vbd/%d/%d/error" (xs.Xs.getdomainpath 
x.backend.domid) x.backend.domid x.frontend.devid
+
 (* Poll a device to see whether it is instantaneously "online" where "online" 
means
    "currently-attached" in the database. The event thread AND the startup code 
call
    this function to resynchronise the state of the world with the database. 
@@ -134,11 +138,12 @@
   debug "Hotplug.wait_for_frontend_plug: %s" (string_of_device x);
   try
     let ok_watch = Watch.value_to_appear (frontend_status_node x) in
-    let error_watch = Watch.value_to_appear (tapdisk_error_node ~xs x) in
+    let tapdisk_error_watch = Watch.value_to_appear (tapdisk_error_node ~xs x) 
in
+       let blkback_error_watch = Watch.value_to_appear (blkback_error_node ~xs 
x) in
     Stats.time_this "udev frontend add event" 
       (fun () ->
         match Watch.wait_for ~xs ~timeout:hotplug_timeout 
-        (Watch.any_of [ `OK, ok_watch; `Failed, error_watch ]) with
+        (Watch.any_of [ `OK, ok_watch; `Failed, tapdisk_error_watch; `Failed, 
blkback_error_watch ]) with
         | `OK, _ ->
             debug "Synchronised ok with frontend hotplug script: %s" 
(string_of_device x)
         | `Failed, e ->
1 file changed, 7 insertions(+), 2 deletions(-)
ocaml/xenops/hotplug.ml |    9 +++++++--

xen-api.hg.patch
Description: Text Data

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