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ceph: fix snap rebuild condition 

We were rebuilding the snap context when it was not necessary
(i.e. when the realm seq hadn't changed _and_ the parent seq
was still older), which caused page snapc pointers to not match
the realm's snapc pointer (even though the snap context itself
was identical).  This confused begin_write and put it into an
endless loop.

The correct logic is: rebuild snapc if _my_ realm seq changed, or
if my parent realm's seq is newer than mine (and thus mine needs
to be rebuilt too).

Signed-off-by: Sage Weil <sage@newdream.net>
This commit is contained in:
Sage Weil 2010-03-19 13:24:39 -07:00
parent 87b315a5b5
commit ec4318bcb4
1 changed files with 2 additions and 2 deletions
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4
fs/ceph/snap.c
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@ -314,9 +314,9 @@ static int build_snap_context(struct ceph_snap_realm *realm)
because we rebuild_snap_realms() works _downward_ in
hierarchy after each update.) */
if (realm->cached_context &&
realm->cached_context->seq <= realm->seq &&
realm->cached_context->seq == realm->seq &&
(!parent ||
realm->cached_context->seq <= parent->cached_context->seq)) {
realm->cached_context->seq >= parent->cached_context->seq)) {
dout("build_snap_context %llx %p: %p seq %lld (%d snaps)"
" (unchanged)\n",
realm->ino, realm, realm->cached_context,