From 00e3d9fbc4c1d5d04ce84e8725d0274c847d1743 Mon Sep 17 00:00:00 2001
From: Mykola Golub <mgolub@suse.com>
Date: Tue, 7 May 2019 06:39:25 +0100
Subject: [PATCH] librbd: allow to provide sparse read result

Signed-off-by: Mykola Golub <mgolub@suse.com>
---
 src/librbd/io/ReadResult.cc | 17 +++++++++++++++++
 src/librbd/io/ReadResult.h  | 14 +++++++++++++-
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/src/librbd/io/ReadResult.cc b/src/librbd/io/ReadResult.cc
index 8ce351c618a8d..dbf8ef48c3e3d 100644
--- a/src/librbd/io/ReadResult.cc
+++ b/src/librbd/io/ReadResult.cc
@@ -77,6 +77,18 @@ struct ReadResult::AssembleResultVisitor : public boost::static_visitor<void> {
                    << "bytes to bl " << reinterpret_cast<void*>(bufferlist.bl)
                    << dendl;
   }
+
+  void operator()(SparseBufferlist &sparse_bufferlist) const {
+    sparse_bufferlist.extent_map->clear();
+    sparse_bufferlist.bl->clear();
+    destriper.assemble_result(cct, sparse_bufferlist.extent_map,
+                              sparse_bufferlist.bl);
+
+    ldout(cct, 20) << "moved resulting " << sparse_bufferlist.extent_map->size()
+                   << " extents of total " << sparse_bufferlist.bl->length()
+                   << " bytes to bl "
+                   << reinterpret_cast<void*>(sparse_bufferlist.bl) << dendl;
+  }
 };
 
 ReadResult::C_ImageReadRequest::C_ImageReadRequest(
@@ -157,6 +169,11 @@ ReadResult::ReadResult(ceph::bufferlist *bl)
   : m_buffer(Bufferlist(bl)) {
 }
 
+ReadResult::ReadResult(std::map<uint64_t, uint64_t> *extent_map,
+                       ceph::bufferlist *bl)
+  : m_buffer(SparseBufferlist(extent_map, bl)) {
+}
+
 void ReadResult::set_clip_length(size_t length) {
   boost::apply_visitor(SetClipLengthVisitor(length), m_buffer);
 }
diff --git a/src/librbd/io/ReadResult.h b/src/librbd/io/ReadResult.h
index 6fb5e4a4c18f2..9efdcb0105cd5 100644
--- a/src/librbd/io/ReadResult.h
+++ b/src/librbd/io/ReadResult.h
@@ -55,6 +55,7 @@ public:
   ReadResult(char *buf, size_t buf_len);
   ReadResult(const struct iovec *iov, int iov_count);
   ReadResult(ceph::bufferlist *bl);
+  ReadResult(std::map<uint64_t, uint64_t> *extent_map, ceph::bufferlist *bl);
 
   void set_clip_length(size_t length);
   void assemble_result(CephContext *cct);
@@ -87,10 +88,21 @@ private:
     }
   };
 
+  struct SparseBufferlist {
+    std::map<uint64_t, uint64_t> *extent_map;
+    ceph::bufferlist *bl;
+
+    SparseBufferlist(std::map<uint64_t, uint64_t> *extent_map,
+                     ceph::bufferlist *bl)
+      : extent_map(extent_map), bl(bl) {
+    }
+  };
+
   typedef boost::variant<Empty,
                          Linear,
                          Vector,
-                         Bufferlist> Buffer;
+                         Bufferlist,
+                         SparseBufferlist> Buffer;
   struct SetClipLengthVisitor;
   struct AssembleResultVisitor;
 
-- 
2.39.5