mds: fix issuing redundant reintegrate/migrate_stray requests

Just in cause a CInode's nlink is 1, and then a unlink request comes
and then early replies and submits to the MDLogs, but just before
the MDlogs are flushed a link request comes, and the link request
also succeeds and early replies to client.

Later when the unlink/link requests' MDLog events are flushed and
the callbacks are called, which will fire a stray denty reintegration.
But it will pick the new dentry, which is from the link's request
and is a remote dentry, to do the reintegration. While in the
'rename' code when traversing the path it will trigger to call the
'dn->link_remote()', which later will fire a new stray dentry
reintegration.

The problem is if the first 'rename' request is retried several
times, and in each time it will fire a new reintegration, which
makes no sense and maybe blocked for a very long time dues to some
reasons and then will be reported as slow request warning.

Fixes: https://tracker.ceph.com/issues/62702
Signed-off-by: Xiubo Li <xiubli@redhat.com>

src/include/ceph_fs.h

@@ -550,6 +550,7 @@ union ceph_mds_request_args_legacy {
 #define CEPH_MDS_FLAG_REPLAY        1  /* this is a replayed op */
 #define CEPH_MDS_FLAG_WANT_DENTRY   2  /* want dentry in reply */
 #define CEPH_MDS_FLAG_ASYNC         4  /* request is async */
+#define CEPH_MDS_FLAG_REINTEGRATE   8  /* request is reintegration */
 
 struct ceph_mds_request_head_legacy {
 	__le64 oldest_client_tid;

src/mds/CDentry.cc

@@ -267,7 +267,7 @@ void CDentry::make_path(filepath& fp, bool projected) const
  * active (no longer projected).  if the passed dnl is projected,
  * don't link in, and do that work later in pop_projected_linkage().
  */
-void CDentry::link_remote(CDentry::linkage_t *dnl, CInode *in)
+void CDentry::link_remote(CDentry::linkage_t *dnl, CInode *in, bool reintegrating)
 {
   ceph_assert(dnl->is_remote());
   ceph_assert(in->ino() == dnl->get_remote_ino());
@@ -277,7 +277,9 @@ void CDentry::link_remote(CDentry::linkage_t *dnl, CInode *in)
     in->add_remote_parent(this);
 
   // check for reintegration
-  dir->mdcache->eval_remote(this);
+  if (!reintegrating) {
+    dir->mdcache->eval_remote(this);
+  }
 }
 
 void CDentry::unlink_remote(CDentry::linkage_t *dnl)

src/mds/CDentry.h

@@ -240,7 +240,7 @@ class CDentry : public MDSCacheObject, public LRUObject, public Counter<CDentry>
   int get_num_dir_auth_pins() const;
 
   // remote links
-  void link_remote(linkage_t *dnl, CInode *in);
+  void link_remote(linkage_t *dnl, CInode *in, bool reintegrating=false);
   void unlink_remote(linkage_t *dnl);
 
   // copy cons

src/mds/MDCache.cc

@@ -8495,7 +8495,7 @@ int MDCache::path_traverse(MDRequestRef& mdr, MDSContextFactory& cf,
         in = get_inode(dnl->get_remote_ino());
         if (in) {
 	  dout(7) << "linking in remote in " << *in << dendl;
-	  dn->link_remote(dnl, in);
+	  dn->link_remote(dnl, in, mdr->client_request->is_reintegration());
 	} else {
           dout(7) << "remote link to " << dnl->get_remote_ino() << ", which i don't have" << dendl;
 	  ceph_assert(mdr);  // we shouldn't hit non-primary dentries doing a non-mdr traversal!
@@ -8775,7 +8775,7 @@ CInode *MDCache::get_dentry_inode(CDentry *dn, MDRequestRef& mdr, bool projected
   CInode *in = get_inode(dnl->get_remote_ino());
   if (in) {
     dout(7) << "get_dentry_inode linking in remote in " << *in << dendl;
-    dn->link_remote(dnl, in);
+    dn->link_remote(dnl, in, mdr->client_request->is_reintegration());
     return in;
   } else {
     dout(10) << "get_dentry_inode on remote dn, opening inode for " << *dn << dendl;

src/mds/StrayManager.cc

@@ -693,6 +693,7 @@ void StrayManager::reintegrate_stray(CDentry *straydn, CDentry *rdn)
   ceph_tid_t tid = mds->issue_tid();
 
   auto req = make_message<MClientRequest>(CEPH_MDS_OP_RENAME);
+  req->set_reintegrated_op();
   req->set_filepath(dst);
   req->set_filepath2(src);
   req->set_tid(tid);
@@ -722,6 +723,7 @@ void StrayManager::migrate_stray(CDentry *dn, mds_rank_t to)
   ceph_tid_t tid = mds->issue_tid();
 
   auto req = make_message<MClientRequest>(CEPH_MDS_OP_RENAME);
+  req->set_reintegrated_op();
   req->set_filepath(dst);
   req->set_filepath2(src);
   req->set_tid(tid);

src/messages/MClientRequest.h

@@ -166,6 +166,10 @@ class MClientRequest final : public MMDSOp {
     return get_flags() & CEPH_MDS_FLAG_ASYNC;
   }
 
+  bool is_reintegration() const {
+    return get_flags() & CEPH_MDS_FLAG_REINTEGRATE;
+  }
+
   // normal fields
   void set_stamp(utime_t t) { stamp = t; }
   void set_oldest_client_tid(ceph_tid_t t) { head.oldest_client_tid = t; }
@@ -192,6 +196,10 @@ class MClientRequest final : public MMDSOp {
     head.flags = head.flags | CEPH_MDS_FLAG_ASYNC;
   }
 
+  void set_reintegrated_op() {
+    head.flags = head.flags | CEPH_MDS_FLAG_REINTEGRATE;
+  }
+
   void set_alternate_name(std::string _alternate_name) {
     alternate_name = std::move(_alternate_name);
   }