Commit ec4318bc authored Mar 19, 2010 by Sage Weil

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>

parent 87b315a5

fs/ceph/snap.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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,