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vol: reset nextVnodeUnique when uniquifier rolls over

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The on disk uniquifier counter is set to 200 more than the current
nextVnodeUnique counter when the volume information is updated to disk. When
the nextVnodeUnique is near UINT32_MAX, then the uniquifier counter rolls
over.  This can happen during a volume header update due to
VBumpVolumeUsage_r().

With this change, the nextVnodeUnique customer is reset to 2 and the
uniquifier is reset to 202 when a roll over occurs. (uniquifier of 1 is
reserved for the root vnode.)

With this change, the number of possible uniquifier numbers is limited to
200 less than UINT32_MAX.

The following shows a series of vnode creation/deletions to illustrate
the uniquifier rollover before this commit:

fid = 536870918.4.4294967114, nextVnodeUnique = 4294967115, uniquifier = 4294967295
fid = 536870918.4.4294967115, nextVnodeUnique = 4294967116, uniquifier = 4294967295
fid = 536870918.4.4294967116, nextVnodeUnique = 4294967117, uniquifier = 21
fid = 536870918.4.4294967117, nextVnodeUnique = 4294967118, uniquifier = 22

and after this commit:

fid = 536870918.4.4294967115, nextVnodeUnique = 4294967116, uniquifier = 4294967295
fid = 536870918.4.4294967116, nextVnodeUnique = 2, uniquifier = 202
fid = 536870918.4.2, nextVnodeUnique = 3, uniquifier = 202
fid = 536870918.4.3, nextVnodeUnique = 4, uniquifier = 202

Change-Id: I93c8a7cf47e39b8701265d6507cfc4f8c1352ddc
Reviewed-on: http://gerrit.openafs.org/10617
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
This commit is contained in:
Michael Meffie 2013-12-23 12:10:36 -05:00 committed by Derrick Brashear
parent 1a287c631e
commit 64d7715c02
1 changed files with 20 additions and 4 deletions
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24
src/vol/volume.c
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@ -218,6 +218,12 @@ pthread_t vol_glock_holder = 0;
*/
#define VOLUME_HASH_REORDER_CHAIN_THRESH (VOLUME_HASH_REORDER_THRESHOLD / 2)
/*
* The per volume uniquifier is bumped by 200 and and written to disk
* every 200 file creates.
*/
#define VOLUME_UPDATE_UNIQUIFIER_BUMP 200
#include "rx/rx_queue.h"
@ -4929,10 +4935,20 @@ VUpdateVolume_r(Error * ec, Volume * vp, int flags)
#endif
*ec = 0;
if (programType == fileServer)
V_uniquifier(vp) =
(V_inUse(vp) ? V_nextVnodeUnique(vp) +
200 : V_nextVnodeUnique(vp));
if (programType == fileServer) {
if (!V_inUse(vp)) {
V_uniquifier(vp) = V_nextVnodeUnique(vp);
} else {
V_uniquifier(vp) =
V_nextVnodeUnique(vp) + VOLUME_UPDATE_UNIQUIFIER_BUMP;
if (V_uniquifier(vp) < V_nextVnodeUnique(vp)) {
/* uniquifier rolled over; reset the counters */
V_nextVnodeUnique(vp) = 2; /* 1 is reserved for the root vnode */
V_uniquifier(vp) =
V_nextVnodeUnique(vp) + VOLUME_UPDATE_UNIQUIFIER_BUMP;
}
}
}
#ifdef AFS_DEMAND_ATTACH_FS
state_save = VChangeState_r(vp, VOL_STATE_UPDATING);