libceph: fix double __remove_osd() problem
It turns out it's possible to get __remove_osd() called twice on the same OSD. That doesn't sit well with rb_erase() - depending on the shape of the tree we can get a NULL dereference, a soft lockup or a random crash at some point in the future as we end up touching freed memory. One scenario that I was able to reproduce is as follows: <osd3 is idle, on the osd lru list> <con reset - osd3> con_fault_finish() osd_reset() <osdmap - osd3 down> ceph_osdc_handle_map() <takes map_sem> kick_requests() <takes request_mutex> reset_changed_osds() __reset_osd() __remove_osd() <releases request_mutex> <releases map_sem> <takes map_sem> <takes request_mutex> __kick_osd_requests() __reset_osd() __remove_osd() <-- !!! A case can be made that osd refcounting is imperfect and reworking it would be a proper resolution, but for now Sage and I decided to fix this by adding a safe guard around __remove_osd(). Fixes: http://tracker.ceph.com/issues/8087 Cc: Sage Weil <sage@redhat.com> Cc: stable@vger.kernel.org # 3.9+: 7c6e6fc53e73: libceph: assert both regular and lingering lists in __remove_osd() Cc: stable@vger.kernel.org # 3.9+: cc9f1f518cec: libceph: change from BUG to WARN for __remove_osd() asserts Cc: stable@vger.kernel.org # 3.9+ Signed-off-by: Ilya Dryomov <idryomov@gmail.com> Reviewed-by: Sage Weil <sage@redhat.com> Reviewed-by: Alex Elder <elder@linaro.org>
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@ -1048,14 +1048,24 @@ static void put_osd(struct ceph_osd *osd)
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*/
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static void __remove_osd(struct ceph_osd_client *osdc, struct ceph_osd *osd)
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{
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dout("__remove_osd %p\n", osd);
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dout("%s %p osd%d\n", __func__, osd, osd->o_osd);
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WARN_ON(!list_empty(&osd->o_requests));
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WARN_ON(!list_empty(&osd->o_linger_requests));
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rb_erase(&osd->o_node, &osdc->osds);
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list_del_init(&osd->o_osd_lru);
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ceph_con_close(&osd->o_con);
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put_osd(osd);
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rb_erase(&osd->o_node, &osdc->osds);
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RB_CLEAR_NODE(&osd->o_node);
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}
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static void remove_osd(struct ceph_osd_client *osdc, struct ceph_osd *osd)
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{
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dout("%s %p osd%d\n", __func__, osd, osd->o_osd);
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if (!RB_EMPTY_NODE(&osd->o_node)) {
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ceph_con_close(&osd->o_con);
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__remove_osd(osdc, osd);
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put_osd(osd);
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}
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}
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static void remove_all_osds(struct ceph_osd_client *osdc)
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@ -1065,7 +1075,7 @@ static void remove_all_osds(struct ceph_osd_client *osdc)
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while (!RB_EMPTY_ROOT(&osdc->osds)) {
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struct ceph_osd *osd = rb_entry(rb_first(&osdc->osds),
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struct ceph_osd, o_node);
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__remove_osd(osdc, osd);
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remove_osd(osdc, osd);
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}
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mutex_unlock(&osdc->request_mutex);
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}
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@ -1106,7 +1116,7 @@ static void remove_old_osds(struct ceph_osd_client *osdc)
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list_for_each_entry_safe(osd, nosd, &osdc->osd_lru, o_osd_lru) {
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if (time_before(jiffies, osd->lru_ttl))
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break;
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__remove_osd(osdc, osd);
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remove_osd(osdc, osd);
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}
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mutex_unlock(&osdc->request_mutex);
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}
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@ -1121,8 +1131,7 @@ static int __reset_osd(struct ceph_osd_client *osdc, struct ceph_osd *osd)
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dout("__reset_osd %p osd%d\n", osd, osd->o_osd);
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if (list_empty(&osd->o_requests) &&
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list_empty(&osd->o_linger_requests)) {
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__remove_osd(osdc, osd);
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remove_osd(osdc, osd);
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return -ENODEV;
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}
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@ -1926,6 +1935,7 @@ static void reset_changed_osds(struct ceph_osd_client *osdc)
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{
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struct rb_node *p, *n;
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dout("%s %p\n", __func__, osdc);
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for (p = rb_first(&osdc->osds); p; p = n) {
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struct ceph_osd *osd = rb_entry(p, struct ceph_osd, o_node);
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