mds: fix race between scatter gather and dirfrag export

If we gather dirty scatter lock state while corresponding dirfrag
is been exporting, we may receive different dirfrag states from
two MDS and we need to find which one is the newest. The solution
is adding a new variable "migrate seq" to dirfrag, increase it by
one when dirfrag's auth MDS changes. When gathering dirty scatter
lock state, use "migrate seq" to find the newest dirfrag state.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>

7 files changed, 77 insertions, 10 deletions

diff --git a/src/mds/CDir.cc b/src/mds/CDir.cc
index 8c83eba0ad9..2b991d78fde 100644
--- a/src/mds/CDir.cc
+++ b/src/mds/CDir.cc
@@ -154,6 +154,7 @@ ostream& CDir::print_db_line_prefix(ostream& out)
 // CDir
 
 CDir::CDir(CInode *in, frag_t fg, MDCache *mdcache, bool auth) :
+  mseq(0),
   dirty_rstat_inodes(member_offset(CInode, dirty_rstat_item)),
   item_dirty(this), item_new(this),
   pop_me(ceph_clock_now(g_ceph_context)),
@@ -2121,6 +2122,8 @@ void CDir::_committed(version_t v)
 void CDir::encode_export(bufferlist& bl)
 {
   assert(!is_projected());
+  ceph_seq_t seq = mseq + 1;
+  ::encode(seq, bl);
   ::encode(first, bl);
   ::encode(fnode, bl);
   ::encode(dirty_old_rstat, bl);
@@ -2150,6 +2153,7 @@ void CDir::finish_export(utime_t now)
 
 void CDir::decode_import(bufferlist::iterator& blp, utime_t now, LogSegment *ls)
 {
+  ::decode(mseq, blp);
   ::decode(first, blp);
   ::decode(fnode, blp);
   ::decode(dirty_old_rstat, blp);
diff --git a/src/mds/CDir.h b/src/mds/CDir.h
index 87c79c2af1b..11f4a76d047 100644
--- a/src/mds/CDir.h
+++ b/src/mds/CDir.h
@@ -170,6 +170,7 @@ public:
 
   fnode_t fnode;
   snapid_t first;
+  ceph_seq_t mseq; // migrate sequence
   map<snapid_t,old_rstat_t> dirty_old_rstat;  // [value.first,key]
 
   // my inodes with dirty rstat data
@@ -547,7 +548,8 @@ public:
   // -- import/export --
   void encode_export(bufferlist& bl);
   void finish_export(utime_t now);
-  void abort_export() { 
+  void abort_export() {
+    mseq += 2;
     put(PIN_TEMPEXPORTING);
   }
   void decode_import(bufferlist::iterator& blp, utime_t now, LogSegment *ls);
diff --git a/src/mds/CInode.cc b/src/mds/CInode.cc
index 8936acdd5ae..48529948955 100644
--- a/src/mds/CInode.cc
+++ b/src/mds/CInode.cc
@@ -1222,6 +1222,7 @@ void CInode::encode_lock_state(int type, bufferlist& bl)
 	  dout(20) << fg << "           fragstat " << pf->fragstat << dendl;
 	  dout(20) << fg << " accounted_fragstat " << pf->accounted_fragstat << dendl;
 	  ::encode(fg, tmp);
+	  ::encode(dir->mseq, tmp);
 	  ::encode(dir->first, tmp);
 	  ::encode(pf->fragstat, tmp);
 	  ::encode(pf->accounted_fragstat, tmp);
@@ -1255,6 +1256,7 @@ void CInode::encode_lock_state(int type, bufferlist& bl)
 	  dout(10) << fg << " " << pf->rstat << dendl;
 	  dout(10) << fg << " " << dir->dirty_old_rstat << dendl;
 	  ::encode(fg, tmp);
+	  ::encode(dir->mseq, tmp);
 	  ::encode(dir->first, tmp);
 	  ::encode(pf->rstat, tmp);
 	  ::encode(pf->accounted_rstat, tmp);
@@ -1404,10 +1406,12 @@ void CInode::decode_lock_state(int type, bufferlist& bl)
       dout(10) << " ...got " << n << " fragstats on " << *this << dendl;
       while (n--) {
 	frag_t fg;
+	ceph_seq_t mseq;
 	snapid_t fgfirst;
 	frag_info_t fragstat;
 	frag_info_t accounted_fragstat;
 	::decode(fg, p);
+	::decode(mseq, p);
 	::decode(fgfirst, p);
 	::decode(fragstat, p);
 	::decode(accounted_fragstat, p);
@@ -1420,6 +1424,12 @@ void CInode::decode_lock_state(int type, bufferlist& bl)
 	  assert(dir);                // i am auth; i had better have this dir open
 	  dout(10) << fg << " first " << dir->first << " -> " << fgfirst
 		   << " on " << *dir << dendl;
+	  if (dir->fnode.fragstat.version == get_projected_inode()->dirstat.version &&
+	      ceph_seq_cmp(mseq, dir->mseq) < 0) {
+	    dout(10) << " mseq " << mseq << " < " << dir->mseq << ", ignoring" << dendl;
+	    continue;
+	  }
+	  dir->mseq = mseq;
 	  dir->first = fgfirst;
 	  dir->fnode.fragstat = fragstat;
 	  dir->fnode.accounted_fragstat = accounted_fragstat;
@@ -1462,11 +1472,13 @@ void CInode::decode_lock_state(int type, bufferlist& bl)
       ::decode(n, p);
       while (n--) {
 	frag_t fg;
+	ceph_seq_t mseq;
 	snapid_t fgfirst;
 	nest_info_t rstat;
 	nest_info_t accounted_rstat;
 	map<snapid_t,old_rstat_t> dirty_old_rstat;
 	::decode(fg, p);
+	::decode(mseq, p);
 	::decode(fgfirst, p);
 	::decode(rstat, p);
 	::decode(accounted_rstat, p);
@@ -1481,6 +1493,12 @@ void CInode::decode_lock_state(int type, bufferlist& bl)
 	  assert(dir);                // i am auth; i had better have this dir open
 	  dout(10) << fg << " first " << dir->first << " -> " << fgfirst
 		   << " on " << *dir << dendl;
+	  if (dir->fnode.rstat.version == get_projected_inode()->rstat.version &&
+	      ceph_seq_cmp(mseq, dir->mseq) < 0) {
+	    dout(10) << " mseq " << mseq << " < " << dir->mseq << ", ignoring" << dendl;
+	    continue;
+	  }
+	  dir->mseq = mseq;
 	  dir->first = fgfirst;
 	  dir->fnode.rstat = rstat;
 	  dir->fnode.accounted_rstat = accounted_rstat;
@@ -1606,6 +1624,36 @@ void CInode::start_scatter(ScatterLock *lock)
   }
 }
 
+/*
+ * set dirfrag_version to inode_version - 1. so that we can use dirfrag version
+ * to check if we have gathered scatter state for a given dirfrag.
+ */
+void CInode::start_scatter_gather(ScatterLock *lock, int auth)
+{
+  assert(is_auth());
+  inode_t *pi = get_projected_inode();
+
+  for (map<frag_t,CDir*>::iterator p = dirfrags.begin();
+       p != dirfrags.end();
+       ++p) {
+    CDir *dir = p->second;
+
+    if (dir->is_auth())
+      continue;
+    if (auth >= 0 && dir->authority().first != auth)
+      continue;
+
+    switch (lock->get_type()) {
+      case CEPH_LOCK_IFILE:
+	dir->fnode.fragstat.version = pi->dirstat.version - 1;
+	break;
+      case CEPH_LOCK_INEST:
+	dir->fnode.rstat.version = pi->rstat.version - 1;
+	break;
+    }
+  }
+}
+
 struct C_Inode_FragUpdate : public Context {
   CInode *in;
   CDir *dir;
diff --git a/src/mds/CInode.h b/src/mds/CInode.h
index 779bb63f485..82c23474308 100644
--- a/src/mds/CInode.h
+++ b/src/mds/CInode.h
@@ -651,6 +651,7 @@ public:
   void clear_scatter_dirty();  // on rejoin ack
 
   void start_scatter(ScatterLock *lock);
+  void start_scatter_gather(ScatterLock *lock, int auth=-1);
   void finish_scatter_update(ScatterLock *lock, CDir *dir,
 			     version_t inode_version, version_t dir_accounted_version);
   void finish_scatter_gather_update(int type);
diff --git a/src/mds/Locker.cc b/src/mds/Locker.cc
index 8065207011a..30e014ab785 100644
--- a/src/mds/Locker.cc
+++ b/src/mds/Locker.cc
@@ -731,8 +731,9 @@ void Locker::eval_gather(SimpleLock *lock, bool first, bool *pneed_issue, list<C
 	  lock->get_parent()->is_replicated()) {
 	dout(10) << " finished (local) gather for mix->lock, now gathering from replicas" << dendl;
 	send_lock_message(lock, LOCK_AC_LOCK);
-	lock->init_gather();
 	lock->set_state(LOCK_MIX_LOCK2);
+	lock->init_gather();
+	in->start_scatter_gather(static_cast<ScatterLock *>(lock));
 	return;
       }
 
@@ -3430,7 +3431,7 @@ bool Locker::simple_sync(SimpleLock *lock, bool *need_issue)
   assert(lock->is_stable());
 
   CInode *in = 0;
-  if (lock->get_cap_shift())
+  if (lock->get_type() != CEPH_LOCK_DN)
     in = static_cast<CInode *>(lock->get_parent());
 
   int old_state = lock->get_state();
@@ -3453,10 +3454,11 @@ bool Locker::simple_sync(SimpleLock *lock, bool *need_issue)
     if (lock->get_parent()->is_replicated() && old_state == LOCK_MIX) {
       send_lock_message(lock, LOCK_AC_SYNC);
       lock->init_gather();
+      in->start_scatter_gather(static_cast<ScatterLock *>(lock));
       gather++;
     }
     
-    if (in && in->is_head()) {
+    if (lock->get_cap_shift() && in->is_head()) {
       if (in->issued_caps_need_gather(lock)) {
 	if (need_issue)
 	  *need_issue = true;
@@ -3568,7 +3570,7 @@ void Locker::simple_lock(SimpleLock *lock, bool *need_issue)
   assert(lock->get_state() != LOCK_LOCK);
   
   CInode *in = 0;
-  if (lock->get_cap_shift())
+  if (lock->get_type() != CEPH_LOCK_DN)
     in = static_cast<CInode *>(lock->get_parent());
 
   int old_state = lock->get_state();
@@ -3596,7 +3598,7 @@ void Locker::simple_lock(SimpleLock *lock, bool *need_issue)
   }
   if (lock->is_rdlocked())
     gather++;
-  if (in && in->is_head()) {
+  if (lock->get_cap_shift() && in->is_head()) {
     if (in->issued_caps_need_gather(lock)) {
       if (need_issue)
 	*need_issue = true;
@@ -3629,6 +3631,8 @@ void Locker::simple_lock(SimpleLock *lock, bool *need_issue)
       gather++;
       send_lock_message(lock, LOCK_AC_LOCK);
       lock->init_gather();
+      if (lock->get_state() == LOCK_MIX_LOCK2)
+	in->start_scatter_gather(static_cast<ScatterLock *>(lock));
     }
   }
 
@@ -4034,8 +4038,9 @@ void Locker::scatter_tempsync(ScatterLock *lock, bool *need_issue)
 
   if (lock->get_state() == LOCK_MIX_TSYN &&
       in->is_replicated()) {
-    lock->init_gather();
     send_lock_message(lock, LOCK_AC_LOCK);
+    lock->init_gather();
+    in->start_scatter_gather(static_cast<ScatterLock *>(lock));
     gather++;
   }
 
@@ -4364,6 +4369,8 @@ void Locker::file_excl(ScatterLock *lock, bool *need_issue)
       lock->get_state() != LOCK_XSYN_EXCL) {  // if we were lock, replicas are already lock.
     send_lock_message(lock, LOCK_AC_LOCK);
     lock->init_gather();
+    if (lock->get_state() == LOCK_MIX_EXCL)
+      in->start_scatter_gather(static_cast<ScatterLock *>(lock));
     gather++;
   }
   if (lock->is_leased()) {
diff --git a/src/mds/MDCache.cc b/src/mds/MDCache.cc
index 2b0029f90b6..f2068e50e7a 100644
--- a/src/mds/MDCache.cc
+++ b/src/mds/MDCache.cc
@@ -3764,6 +3764,7 @@ void MDCache::rejoin_walk(CDir *dir, MMDSCacheRejoin *rejoin)
     dout(15) << " add_strong_dirfrag " << *dir << dendl;
     rejoin->add_strong_dirfrag(dir->dirfrag(), dir->get_replica_nonce(), dir->get_dir_rep());
     dir->state_set(CDir::STATE_REJOINING);
+    dir->mseq = 0;
 
     for (CDir::map_t::iterator p = dir->items.begin();
 	 p != dir->items.end();
@@ -3913,11 +3914,15 @@ void MDCache::handle_cache_rejoin_weak(MMDSCacheRejoin *weak)
        ++p) {
     CInode *in = get_inode(p->first);
     assert(in);
+    if (survivor) {
+      in->start_scatter_gather(&in->filelock, from);
+      in->start_scatter_gather(&in->nestlock, from);
+    } else {
+      rejoin_potential_updated_scatterlocks.insert(in);
+    }
     in->decode_lock_state(CEPH_LOCK_IFILE, p->second.file);
     in->decode_lock_state(CEPH_LOCK_INEST, p->second.nest);
     in->decode_lock_state(CEPH_LOCK_IDFT, p->second.dft);
-    if (!survivor)
-      rejoin_potential_updated_scatterlocks.insert(in);
   }
 
   // recovering peer may send incorrect dirfrags here.  we need to
diff --git a/src/mds/MDS.h b/src/mds/MDS.h
index 9e3e2dae9c3..b99815dab34 100644
--- a/src/mds/MDS.h
+++ b/src/mds/MDS.h
@@ -35,7 +35,7 @@
 #include "SessionMap.h"
 
 
-#define CEPH_MDS_PROTOCOL    17 /* cluster internal */
+#define CEPH_MDS_PROTOCOL    18 /* cluster internal */
 
 
 enum {