From 64cba025b13aad7fb3020a04930cfa22fbfcb859 Mon Sep 17 00:00:00 2001 From: Pranith Kumar K Date: Tue, 8 Mar 2016 23:05:08 +0530 Subject: cluster/ec: Do not ref dictionary in lookup Problem: 1) dict_for_each loops over the elements without any locks, so the members of the dictionary can be ref/unrefed while dict_for_each is executed by another thread leading to crashes. Basically with distributed ec + disctributed replicate as cold, hot tiers. tier sends a lookup which fails on ec. (By this time dict already contains ec xattrs) After this lookup_everywhere code path is hit in tier which triggers lookup on each of distribute's hash lookup but fails which leads to the cold, hot dht's lookup_everywhere in two parallel epoll threads where in ec when it tries to set trusted.ec.version/dirty/size as keys in the dictionary, the older values against the same key get erased. While this erasing is going on if the thread that is doing lookup on afr's subvolume accesses these keys either in dict_copy_with_ref or client xlator trying to serialize, that can either lead to crash or hang based on if the spin/mutex lock is called on invalid memory. 2) EC deletes GF_CONTENT_KEY from the dictionary, this may lead to extra reads in case of lookup-everwhere for tiered volumes. Fix: Do dict_copy_with_ref() for the lookup-dictionary. This is avoiding the problem and is not actually fixing the 1st problem. 2nd problem will be fixed. Change-Id: I5427aa14c48cb7572977d4de9a28c5ffff2b4b95 BUG: 1315560 Signed-off-by: Pranith Kumar K Reviewed-on: http://review.gluster.org/13680 Smoke: Gluster Build System NetBSD-regression: NetBSD Build System CentOS-regression: Gluster Build System Reviewed-by: Xavier Hernandez --- xlators/cluster/ec/src/ec-generic.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) (limited to 'xlators/cluster/ec') diff --git a/xlators/cluster/ec/src/ec-generic.c b/xlators/cluster/ec/src/ec-generic.c index 3f5856e7a86..375e49e695c 100644 --- a/xlators/cluster/ec/src/ec-generic.c +++ b/xlators/cluster/ec/src/ec-generic.c @@ -906,14 +906,11 @@ void ec_lookup(call_frame_t * frame, xlator_t * this, uintptr_t target, } } if (xdata != NULL) { - fop->xdata = dict_ref(xdata); - if (fop->xdata == NULL) { - gf_msg (this->name, GF_LOG_ERROR, 0, - EC_MSG_DICT_REF_FAIL, "Failed to reference a " - "dictionary."); - + fop->xdata = dict_copy_with_ref (xdata, NULL); + /* Do not log failures here as a memory problem would have already + * been logged by the corresponding alloc functions */ + if (fop->xdata == NULL) goto out; - } } error = 0; -- cgit