From: Adam C. Emerson <aemerson@redhat.com>
Date: Tue, 9 Feb 2021 23:10:50 +0000 (-0500)
Subject: rgw: Leave the zero'th shard of the zero'th generation for cls_lock
X-Git-Tag: v17.1.0~2399^2~4
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=0d4e0abb8a699417ea75a6cd390786189ab964eb;p=ceph.git

rgw: Leave the zero'th shard of the zero'th generation for cls_lock

Since data sync locks that object, instead of deleting it, truncate
the object and clear the omap.

(cls_lock uses xattrs.)

Signed-off-by: Adam C. Emerson <aemerson@redhat.com>
---

diff --git a/src/rgw/rgw_log_backing.cc b/src/rgw/rgw_log_backing.cc
index eab60e672b9e..67fc92558691 100644
--- a/src/rgw/rgw_log_backing.cc
+++ b/src/rgw/rgw_log_backing.cc
@@ -168,6 +168,7 @@ log_backing_type(librados::IoCtx& ioctx,
 bs::error_code log_remove(librados::IoCtx& ioctx,
 			  int shards,
 			  const fu2::unique_function<std::string(int) const>& get_oid,
+			  bool leave_zero,
 			  optional_yield y)
 {
   bs::error_code ec;
@@ -204,7 +205,16 @@ bs::error_code log_remove(librados::IoCtx& ioctx,
 		 << ", r=" << r << dendl;
     }
     librados::ObjectWriteOperation op;
-    op.remove();
+    if (i == 0 && leave_zero) {
+      // Leave shard 0 in existence, but remove contents and
+      // omap. cls_lock stores things in the xattrs. And sync needs to
+      // rendezvous with locks on generation 0 shard 0.
+      op.omap_set_header({});
+      op.omap_clear();
+      op.truncate(0);
+    } else {
+      op.remove();
+    }
     r = rgw_rados_operate(ioctx, oid, &op, null_yield);
     if (r < 0 && r != -ENOENT) {
       if (!ec)
@@ -291,7 +301,7 @@ bs::error_code logback_generations::setup(log_type def,
 	  auto ec = log_remove(ioctx, shards,
 			       [this](int shard) {
 				 return this->get_oid(0, shard);
-			       }, y);
+			       }, true, y);
 	  if (ec) return ec;
 	}
 	std::unique_lock lock(m);
@@ -631,7 +641,7 @@ bs::error_code logback_generations::remove_empty(optional_yield y) noexcept {
 	auto ec = log_remove(ioctx, shards,
 			     [this, gen_id](int shard) {
 			       return this->get_oid(gen_id, shard);
-			     }, y);
+			     }, (gen_id == 0), y);
 	if (ec) {
 	  return ec;
 	}
diff --git a/src/rgw/rgw_log_backing.h b/src/rgw/rgw_log_backing.h
index cd677764c579..e592bc29b2bc 100644
--- a/src/rgw/rgw_log_backing.h
+++ b/src/rgw/rgw_log_backing.h
@@ -88,6 +88,7 @@ bs::error_code log_remove(librados::IoCtx& ioctx,
 			  /// A function taking a shard number and
 			  /// returning an oid.
 			  const fu2::unique_function<std::string(int) const>& get_oid,
+			  bool leave_zero,
 			  optional_yield y);