From: Mark Vitale <mvitale@sinenomine.net>
Date: Fri, 21 Dec 2012 22:56:14 +0000 (-0500)
Subject: dafs: preattach should wait for exclusive states
X-Git-Tag: upstream/1.6.6_pre2^2~133
X-Git-Url: https://git.michaelhowe.org/gitweb/?a=commitdiff_plain;h=ac750113f34bcd03df3350ec9863b7b3c67efa25;p=packages%2Fo%2Fopenafs.git

dafs: preattach should wait for exclusive states

In rare circumstances an FSYNC_VOL_ON operation may fail silently,
leaving the volume in its previous state.  The only clue is a FileLog
message "volume <nnnn> not in quiescent state".

This is caused by a race condition in the volume package: an
FSYNC_VOL_ON operation is attempting to preattach a volume
(in VPreAttachVolumeByVp_r()) at the same time a fileserver RPC
(e.g. FetchStatus) is detaching the volume (in VReleaseVolumeHandles_r())
at the conclusion of attach2() logic.

The fix calls VWaitExclusiveState_r() before calling
VPreAttachVolumeByVp_r().

Change-Id: Ib66859381d29311fda3e08984dcb740eadafb340
Reviewed-on: http://gerrit.openafs.org/8814
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
(cherry picked from commit 1f891b622e9b32a068082087eae9d787057f7f00)
Reviewed-on: http://gerrit.openafs.org/9070
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
---

diff --git a/src/vol/volume.c b/src/vol/volume.c
index d5c45adee..bd407cca1 100644
--- a/src/vol/volume.c
+++ b/src/vol/volume.c
@@ -2146,11 +2146,26 @@ VPreAttachVolumeById_r(Error * ec,
 	return NULL;
     }
 
+    /* ensure that any vp we pass to VPreAttachVolumeByVp_r
+     * is NOT in exclusive state.
+     */
+ retry:
     vp = VLookupVolume_r(ec, volumeId, NULL);
+
     if (*ec) {
 	return NULL;
     }
 
+    if (vp && VIsExclusiveState(V_attachState(vp))) {
+	VCreateReservation_r(vp);
+	VWaitExclusiveState_r(vp);
+	VCancelReservation_r(vp);
+	vp = NULL;
+	goto retry;    /* look up volume again */
+    }
+
+    /* vp == NULL or vp not exclusive both OK */
+
     return VPreAttachVolumeByVp_r(ec, partp, vp, volumeId);
 }
 
@@ -2166,6 +2181,8 @@ VPreAttachVolumeById_r(Error * ec,
  *
  * @pre VOL_LOCK is held.
  *
+ * @pre vp (if specified) must not be in exclusive state.
+ *
  * @warning Returned volume object pointer does not have to
  *          equal the pointer passed in as argument vp.  There
  *          are potential race conditions which can result in
@@ -2190,6 +2207,11 @@ VPreAttachVolumeByVp_r(Error * ec,
 
     *ec = 0;
 
+    /* don't proceed unless it's safe */
+    if (vp) {
+	osi_Assert(!VIsExclusiveState(V_attachState(vp)));
+    }
+
     /* check to see if pre-attach already happened */
     if (vp &&
 	(V_attachState(vp) != VOL_STATE_UNATTACHED) &&