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ceph: queue cap_snaps once per realm 

We were forming a dirty list, and then queueing cap_snaps for each realm
_and_ its children, regardless of whether the children were already in the
dirty list.  This meant we did it twice for some realms.  Which in turn
meant we corrupted mdsc->snap_flush_list when the cap_snap was re-added to
the list it was already on, and could trigger an infinite loop.

We were also using recursion to do reach all the children, a no-no when
stack is limited.

Instead, (re)queue any children on the dirty list, avoiding processing
anything twice and avoiding any recursion.

Signed-off-by: Sage Weil <sage@newdream.net>
This commit is contained in:
Sage Weil 2011-02-04 20:45:58 -08:00
parent 42961d2333
commit e8e1ba96b2
1 changed files with 10 additions and 4 deletions
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14
fs/ceph/snap.c
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@ -584,10 +584,14 @@ static void queue_realm_cap_snaps(struct ceph_snap_realm *realm)
if (lastinode)
iput(lastinode);
dout("queue_realm_cap_snaps %p %llx children\n", realm, realm->ino);
list_for_each_entry(child, &realm->children, child_item)
queue_realm_cap_snaps(child);
list_for_each_entry(child, &realm->children, child_item) {
dout("queue_realm_cap_snaps %p %llx queue child %p %llx\n",
realm, realm->ino, child, child->ino);
list_del_init(&child->dirty_item);
list_add(&child->dirty_item, &realm->dirty_item);
}
list_del_init(&realm->dirty_item);
dout("queue_realm_cap_snaps %p %llx done\n", realm, realm->ino);
}
@ -683,7 +687,9 @@ more:
* queue cap snaps _after_ we've built the new snap contexts,
* so that i_head_snapc can be set appropriately.
*/
list_for_each_entry(realm, &dirty_realms, dirty_item) {
while (!list_empty(&dirty_realms)) {
realm = list_first_entry(&dirty_realms, struct ceph_snap_realm,
dirty_item);
queue_realm_cap_snaps(realm);
}