From: Yan, Zheng <zyan@redhat.com>
Date: Mon, 12 Aug 2019 02:09:02 +0000 (+0800)
Subject: mds: explictly specify if MDCache::path_traverse() needs to check null dentry
X-Git-Tag: v15.1.0~766^2~9
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=7b8e289f0c0cf6040b91a670c03288b18b478fc3;p=ceph.git

mds: explictly specify if MDCache::path_traverse() needs to check null dentry

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
---

diff --git a/src/mds/MDCache.cc b/src/mds/MDCache.cc
index d1333a19fa84..18198b0d8084 100644
--- a/src/mds/MDCache.cc
+++ b/src/mds/MDCache.cc
@@ -8054,6 +8054,7 @@ int MDCache::path_traverse(MDRequestRef& mdr, MDSContextFactory& cf,
   bool discover = (flags & MDS_TRAVERSE_DISCOVER);
   bool forward = !discover;
   bool last_xlocked = (flags & MDS_TRAVERSE_LAST_XLOCKED);
+  bool want_dentry = (flags & MDS_TRAVERSE_WANT_DENTRY);
 
   if (forward)
     ceph_assert(mdr);  // forward requires a request
@@ -8208,19 +8209,14 @@ int MDCache::path_traverse(MDRequestRef& mdr, MDSContextFactory& cf,
       CDentry::linkage_t *dnl = dn->get_projected_linkage();
       // can we conclude ENOENT?
       if (dnl->is_null()) {
-	if (pin)
-	  *pin = nullptr;
-
+	dout(10) << "traverse: null+readable dentry at " << *dn << dendl;
 	if (depth == path.depth() - 1) {
-	  if (last_xlocked) {
-	    dout(10) << "traverse: null+tail+xlocked dentry at " << *dn << dendl;
+	  if (want_dentry)
 	    break;
-	  }
 	} else {
 	  if (pdnvec)
 	    pdnvec->clear();   // do not confuse likes of rdlock_path_pin_ref();
 	}
-	dout(10) << "traverse: null+readable dentry at " << *dn << dendl;
 	return -ENOENT;
       }
 
@@ -8263,6 +8259,8 @@ int MDCache::path_traverse(MDRequestRef& mdr, MDSContextFactory& cf,
       continue;
     }
 
+    ceph_assert(!dn);
+
     // MISS.  dentry doesn't exist.
     dout(12) << "traverse: miss on dentry " << path[depth] << " in " << *curdir << dendl;
 
@@ -8275,24 +8273,26 @@ int MDCache::path_traverse(MDRequestRef& mdr, MDSContextFactory& cf,
         // file not found
 	if (pdnvec) {
 	  // instantiate a null dn?
-	  if (depth < path.depth()-1){
+	  if (depth < path.depth() - 1) {
 	    dout(20) << " didn't traverse full path; not returning pdnvec" << dendl;
-	    dn = NULL;
-	  } else if (dn) {
-	    ceph_abort(); // should have fallen out in ->is_null() check above
-	  } else if (curdir->is_frozen()) {
-	    dout(20) << " not adding null to frozen dir " << dendl;
 	  } else if (snapid < CEPH_MAXSNAP) {
 	    dout(20) << " not adding null for snapid " << snapid << dendl;
+	  } else if (curdir->is_frozen()) {
+	    dout(7) << "traverse: " << *curdir << " is frozen, waiting" << dendl;
+	    curdir->add_waiter(CDir::WAIT_UNFREEZE, cf.build());
+	    return 1;
 	  } else {
 	    // create a null dentry
 	    dn = curdir->add_null_dentry(path[depth]);
 	    dout(20) << " added null " << *dn << dendl;
 	  }
-	  if (dn)
+	  if (dn) {
 	    pdnvec->push_back(dn);
-	  else
+	    if (want_dentry)
+	      break;
+	  } else {
 	    pdnvec->clear();   // do not confuse likes of rdlock_path_pin_ref();
+	  }
 	}
         return -ENOENT;
       } else {
diff --git a/src/mds/MDCache.h b/src/mds/MDCache.h
index d416d0fb9cf5..0e3f781d5f31 100644
--- a/src/mds/MDCache.h
+++ b/src/mds/MDCache.h
@@ -113,6 +113,7 @@ enum {
 // flags for path_traverse();
 static const int MDS_TRAVERSE_DISCOVER		= (1 << 0);
 static const int MDS_TRAVERSE_LAST_XLOCKED	= (1 << 1);
+static const int MDS_TRAVERSE_WANT_DENTRY	= (1 << 2);
 
 // flags for predirty_journal_parents()
 static const int PREDIRTY_PRIMARY = 1; // primary dn, adjust nested accounting
@@ -769,8 +770,10 @@ class MDCache {
    * MDS_TRAVERSE_DISCOVER: Instead of forwarding request, path_traverse()
    * attempts to look up the path from a different MDS (and bring them into
    * its cache as replicas).
-   * MDS_TRAVERSE_LAST_XLOCKED: path_traverse() will succeed on xlocked tail
-   * dentry (return 0 even it's null).
+   * MDS_TRAVERSE_LAST_XLOCKED: path_traverse() will procceed when xlocked tail
+   * dentry is encountered.
+   * MDS_TRAVERSE_WANT_DENTRY: Caller wants tail dentry. Add a null dentry if
+   * tail dentry does not exist. return 0 even tail dentry is null.
    *
    * @param pdnvec Data return parameter -- on success, contains a
    * vector of dentries. On failure, is either empty or contains the
diff --git a/src/mds/Server.cc b/src/mds/Server.cc
index ae83a48d53cb..c2a9c27a4cc1 100644
--- a/src/mds/Server.cc
+++ b/src/mds/Server.cc
@@ -8693,7 +8693,7 @@ void Server::handle_slave_rename_prep(MDRequestRef& mdr)
   vector<CDentry*> trace;
   CF_MDS_MDRContextFactory cf(mdcache, mdr);
   int r = mdcache->path_traverse(mdr, cf, destpath,
-				 MDS_TRAVERSE_DISCOVER | MDS_TRAVERSE_LAST_XLOCKED,
+				 MDS_TRAVERSE_DISCOVER | MDS_TRAVERSE_LAST_XLOCKED | MDS_TRAVERSE_WANT_DENTRY,
 				 &trace);
   if (r > 0) return;
   if (r == -ESTALE) {
@@ -8718,9 +8718,6 @@ void Server::handle_slave_rename_prep(MDRequestRef& mdr)
   if (r > 0) return;
   ceph_assert(r == 0);
 
-  // srcpath must not point to a null dentry
-  ceph_assert(srci != nullptr);
-      
   CDentry *srcdn = trace.back();
   CDentry::linkage_t *srcdnl = srcdn->get_projected_linkage();
   dout(10) << " srcdn " << *srcdn << dendl;