From: Michael Meffie Date: Mon, 23 Dec 2013 16:42:19 +0000 (-0500) Subject: vol: fix nextVnodeUnique roll over X-Git-Tag: openafs-stable-1_8_0pre1~847 X-Git-Url: http://git.openafs.org/?p=openafs.git;a=commitdiff_plain;h=1a287c631ead0221828ae70e10c3cfd5563fdfb7 vol: fix nextVnodeUnique roll over Fixes for the per volume nextVnodeUnique counter roll over. Uniquifier number 1 is reserved for the root vnode, so reset the unique count to 2 when the nextVnodeUnique counter rolls over. Update the disk backed V_uniquifier count when the in-memory nextVnodeUnique counter rolls over during the creation of a new vnode. If the nextVnodeUnique rolls over when V_uniquifier is UINT32_MAX, then the V_uniquifier is not updated and remains at UINT32_MAX until the next VUpdateVolume_r() call for the volume. This bug is usually masked by the VBumpVolumeUsage(), which on every 128 volume accesses, bumps the V_uniquifier to be 200 more than the current nextVnodeUnique counter. This causes the V_uniquifier to roll over before reaching UINT32_MAX. (The number of access before updating the headers is set in the usage_threshold volume package option, which is currently set to 128 by default.) The following shows the unique counters for a series of vnode creation/deletions before this commit. The nextVnodeUnique rolls over to 1, and the uniquifier is not reset. The `usage_threshold' was set to a value greater than 200 to avoid the VBumpVolumeUsage() calls during this test run. fid = 536870918.4.4294967294, nextVnodeUnique = 4294967295, uniquifier = 4294967295 fid = 536870918.4.4294967295, nextVnodeUnique = 0, uniquifier = 4294967295 fid = 536870918.4.1, nextVnodeUnique = 2, uniquifier = 4294967295 fid = 536870918.4.2, nextVnodeUnique = 3, uniquifier = 4294967295 The following shows the unique counters after this commit: fid = 536870918.4.4294967294, nextVnodeUnique = 4294967295, uniquifier = 4294967295 fid = 536870918.4.4294967295, nextVnodeUnique = 0, uniquifier = 4294967295 fid = 536870918.4.2, nextVnodeUnique = 3, uniquifier = 203 fid = 536870918.4.3, nextVnodeUnique = 4, uniquifier = 203 Change-Id: I438670200bf97baeac1486eda7df4cf243aabfc4 Reviewed-on: http://gerrit.openafs.org/10616 Tested-by: BuildBot Reviewed-by: Benjamin Kaduk Reviewed-by: Jeffrey Altman Reviewed-by: Derrick Brashear --- diff --git a/src/vol/vnode.c b/src/vol/vnode.c index 6983e8d..9eb120d 100644 --- a/src/vol/vnode.c +++ b/src/vol/vnode.c @@ -651,11 +651,16 @@ VAllocVnode_r(Error * ec, Volume * vp, VnodeType type, VnodeId in_vnode, Unique */ if (!in_vnode) { + int rollover = 0; + unique = vp->nextVnodeUnique++; - if (!unique) + if (unique == 0) { + rollover = 1; /* nextVnodeUnique rolled over */ + vp->nextVnodeUnique = 2; /* 1 is reserved for the root vnode */ unique = vp->nextVnodeUnique++; + } - if (vp->nextVnodeUnique > V_uniquifier(vp)) { + if (vp->nextVnodeUnique > V_uniquifier(vp) || rollover) { VUpdateVolume_r(ec, vp, 0); if (*ec) return NULL;