fix stale volume info from vos examine (non-dafs)

A volume examine on a non-dafs volume server/fileserver can show old
information, including old volume update time, for up to about 20
minutes. The non-dafs volume server reads the volume information
from the volume headers, which are updated by the fileserver only
periodically to avoid excessive i/o.

Before dafs, when the volume server performed a volume examine, the
volume server would send a fssync command to the fileserver with the
request FSYNC_NEEDVOLUME and mode V_READONLY. The fileserver writes
the current memory contents to disk on this fssync command. The
volume server would then attach the volume, reading the current
volume data.

The dafs volume/fileserver avoids this extra i/o by using a new set
of fssync commands to retrieve the volume information from the
fileserver. However, the non-dafs volume server does not use the new
fssync commands and reads the volume headers from disk.

Revert the volume attachment processing for the non-dafs volume
server to request the volume with the V_READONLY mode. This causes
the fileserver to update the volume headers, allowing the volume
server to read the up to date volume header data.

Sadly, this adds another dafs ifdef to the already twisty maze of
passages that all look alike.

This changes the volserver to use the V_READONLY attachment mode
only for the case of getting a single volume, as that what was
done in 1.4.x.

Change-Id: Ibee25bfcfb087e73ccbc17e181a99da49a7751ae
Reviewed-on: http://gerrit.openafs.org/8327
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>

diff --git a/src/volser/volprocs.c b/src/volser/volprocs.c
index dd3eb7b..eb003a4 100644 (file)
--- a/src/volser/volprocs.c
+++ b/src/volser/volprocs.c
@@ -2225,8 +2225,15 @@ GetVolInfo(afs_uint32 partId,
     /* Get volume from volserver */
     if (mode == VOL_INFO_LIST_MULTIPLE)
        tv = VAttachVolumeByName(&error, pname, volname, V_PEEK);
-    else
-       tv = VAttachVolumeByName_retry(&error, pname, volname, V_PEEK);
+    else {
+#ifdef AFS_DEMAND_ATTACH_FS
+       int mode = V_PEEK;
+#else
+       int mode = V_READONLY;   /* informs the fileserver to update the volume headers. */
+#endif
+       tv = VAttachVolumeByName_retry(&error, pname, volname, mode);
+    }
+
     if (error) {
        Log("1 Volser: GetVolInfo: Could not attach volume %u (%s:%s) error=%d\n",
            volumeId, pname, volname, error);