From: Joao Eduardo Luis <joao.luis@inktank.com>
Date: Sat, 3 May 2014 02:42:19 +0000 (+0100)
Subject: mon: OSDMonitor: disallow nonsensical cache-mode transitions
X-Git-Tag: v0.81~73^2
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=refs%2Fpull%2F1740%2Fhead;p=ceph.git

mon: OSDMonitor: disallow nonsensical cache-mode transitions

Fixes: 8155

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
---

diff --git a/PendingReleaseNotes b/PendingReleaseNotes
index 39d8f4b5fae8..34103ec4ae39 100644
--- a/PendingReleaseNotes
+++ b/PendingReleaseNotes
@@ -2,3 +2,7 @@
 v0.81
 -----
 
+- Disallow nonsensical 'tier cache-mode' transitions.  From this point
+  onward, 'writeback' can only transition to 'forward' and 'forward'
+  can transition to 1) 'writeback' if there are dirty objects, or 2) any if
+  there are no dirty objects.
diff --git a/qa/workunits/cephtool/test.sh b/qa/workunits/cephtool/test.sh
index d5e9cef486f6..8ed6bd12c015 100755
--- a/qa/workunits/cephtool/test.sh
+++ b/qa/workunits/cephtool/test.sh
@@ -58,7 +58,31 @@ ceph osd pool create cache2 2
 ceph osd tier add data cache
 ceph osd tier add data cache2
 expect_false ceph osd tier add metadata cache
+# test some state transitions
 ceph osd tier cache-mode cache writeback
+ceph osd tier cache-mode cache forward
+ceph osd tier cache-mode cache readonly
+ceph osd tier cache-mode cache forward
+ceph osd tier cache-mode cache none
+ceph osd tier cache-mode cache writeback
+expect_false ceph osd tier cache-mode cache none
+expect_false ceph osd tier cache-mode cache readonly
+# test with dirty objects in the tier pool
+# tier pool currently set to 'writeback'
+rados -p cache put /etc/passwd /etc/passwd
+ceph tell osd.* flush_pg_stats || true
+# 1 dirty object in pool 'cache'
+ceph osd tier cache-mode cache forward
+expect_false ceph osd tier cache-mode cache none
+expect_false ceph osd tier cache-mode cache readonly
+ceph osd tier cache-mode cache writeback
+# remove object from tier pool
+rados -p cache rm /etc/passwd
+rados -p cache cache-flush-evict-all
+ceph tell osd.* flush_pg_stats || true
+# no dirty objects in pool 'cache'
+ceph osd tier cache-mode cache forward
+ceph osd tier cache-mode cache none
 ceph osd tier cache-mode cache readonly
 TRIES=0
 while ! ceph osd pool set cache pg_num 3 --yes-i-really-mean-it 2>$TMPFILE
diff --git a/src/mon/OSDMonitor.cc b/src/mon/OSDMonitor.cc
index 5877e4ab9f7c..cc417c4f4355 100644
--- a/src/mon/OSDMonitor.cc
+++ b/src/mon/OSDMonitor.cc
@@ -5140,6 +5140,50 @@ done:
       goto reply;
     }
 
+    /* Mode description:
+     *
+     *  none:       No cache-mode defined
+     *  forward:    Forward all reads and writes to base pool
+     *  writeback:  Cache writes, promote reads from base pool
+     *  readonly:   Forward writes to base pool
+     *
+     * Hence, these are the allowed transitions:
+     *
+     *  none -> any
+     *  forward -> writeback || any IF num_objects_dirty == 0
+     *  writeback -> forward
+     *  readonly -> any
+     */
+
+    // We check if the transition is valid against the current pool mode, as
+    // it is the only committed state thus far.  We will blantly squash
+    // whatever mode is on the pending state.
+
+    if (p->cache_mode == pg_pool_t::CACHEMODE_WRITEBACK &&
+        mode != pg_pool_t::CACHEMODE_FORWARD) {
+      ss << "unable to set cache-mode '" << pg_pool_t::get_cache_mode_name(mode)
+         << "' on a '" << pg_pool_t::get_cache_mode_name(p->cache_mode)
+         << "' pool; only '"
+         << pg_pool_t::get_cache_mode_name(pg_pool_t::CACHEMODE_FORWARD)
+        << "' allowed.";
+      err = -EINVAL;
+      goto reply;
+    }
+    if (p->cache_mode == pg_pool_t::CACHEMODE_FORWARD &&
+               mode != pg_pool_t::CACHEMODE_WRITEBACK) {
+
+      const pool_stat_t& tier_stats =
+        mon->pgmon()->pg_map.get_pg_pool_sum_stat(pool_id);
+
+      if (tier_stats.stats.sum.num_objects_dirty > 0) {
+        ss << "unable to set cache-mode '"
+           << pg_pool_t::get_cache_mode_name(mode) << "' on pool '" << poolstr
+           << "': dirty objects found";
+        err = -EBUSY;
+        goto reply;
+      }
+    }
+
     // go
     pending_inc.get_new_pool(pool_id, p)->cache_mode = mode;
     ss << "set cache-mode for pool '" << poolstr