From 0031be017dea4d908a8b4a34e809bec88e8b1acc Mon Sep 17 00:00:00 2001
From: Pranith Kumar K <pkarampu@redhat.com>
Date: Tue, 8 Mar 2016 23:05:08 +0530
Subject: [PATCH 66/80] 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 <pkarampu@redhat.com>
 >Reviewed-on: http://review.gluster.org/13680
 >Smoke: Gluster Build System <jenkins@build.gluster.com>
 >NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
 >CentOS-regression: Gluster Build System <jenkins@build.gluster.com>
 >Reviewed-by: Xavier Hernandez <xhernandez@datalab.es>

BUG: 1318428
Change-Id: I91401d978f7bb9d00b7a9c832526f79ad0a30532
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: https://code.engineering.redhat.com/gerrit/71972
---
 xlators/cluster/ec/src/ec-generic.c |   11 ++++-------
 1 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/xlators/cluster/ec/src/ec-generic.c b/xlators/cluster/ec/src/ec-generic.c
index 3f5856e..375e49e 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;
-- 
1.7.1