librbd: add ReadRequest to handle read

Signed-off-by: Peterson, Scott <scott.d.peterson@intel.com>
Signed-off-by: Li, Xiaoyan <xiaoyan.li@intel.com>
Signed-off-by: Lu, Yuan <yuan.y.lu@intel.com>
Signed-off-by: Chamarthy, Mahati <mahati.chamarthy@intel.com>

src/librbd/cache/rwl/Request.cc

@@ -403,6 +403,57 @@ std::ostream &operator<<(std::ostream &os,
   return os;
 };
 
+void C_ReadRequest::finish(int r) {
+  ldout(m_cct, 20) << "(" << get_name() << "): r=" << r << dendl;
+  int hits = 0;
+  int misses = 0;
+  int hit_bytes = 0;
+  int miss_bytes = 0;
+  if (r >= 0) {
+    /*
+     * At this point the miss read has completed. We'll iterate through
+     * read_extents and produce *m_out_bl by assembling pieces of miss_bl
+     * and the individual hit extent bufs in the read extents that represent
+     * hits.
+     */
+    uint64_t miss_bl_offset = 0;
+    for (auto &extent : read_extents) {
+      if (extent.m_bl.length()) {
+        /* This was a hit */
+        ceph_assert(extent.second == extent.m_bl.length());
+        ++hits;
+        hit_bytes += extent.second;
+        m_out_bl->claim_append(extent.m_bl);
+      } else {
+        /* This was a miss. */
+        ++misses;
+        miss_bytes += extent.second;
+        bufferlist miss_extent_bl;
+        miss_extent_bl.substr_of(miss_bl, miss_bl_offset, extent.second);
+        /* Add this read miss bufferlist to the output bufferlist */
+        m_out_bl->claim_append(miss_extent_bl);
+        /* Consume these bytes in the read miss bufferlist */
+        miss_bl_offset += extent.second;
+      }
+    }
+  }
+  ldout(m_cct, 20) << "(" << get_name() << "): r=" << r << " bl=" << *m_out_bl << dendl;
+  utime_t now = ceph_clock_now();
+  ceph_assert((int)m_out_bl->length() == hit_bytes + miss_bytes);
+  m_on_finish->complete(r);
+  m_perfcounter->inc(l_librbd_rwl_rd_bytes, hit_bytes + miss_bytes);
+  m_perfcounter->inc(l_librbd_rwl_rd_hit_bytes, hit_bytes);
+  m_perfcounter->tinc(l_librbd_rwl_rd_latency, now - m_arrived_time);
+  if (!misses) {
+    m_perfcounter->inc(l_librbd_rwl_rd_hit_req, 1);
+    m_perfcounter->tinc(l_librbd_rwl_rd_hit_latency, now - m_arrived_time);
+  } else {
+    if (hits) {
+      m_perfcounter->inc(l_librbd_rwl_rd_part_hit_req, 1);
+    }
+  }
+}
+
 std::ostream &operator<<(std::ostream &os,
                          const BlockGuardReqState &r) {
   os << "barrier=" << r.barrier << ", "

src/librbd/cache/rwl/Request.h

@@ -231,6 +231,31 @@ private:
                                   const C_FlushRequest<U> &req);
 };
 
+class C_ReadRequest : public Context {
+public:
+  io::Extents miss_extents; // move back to caller
+  ImageExtentBufs read_extents;
+  bufferlist miss_bl;
+
+  C_ReadRequest(CephContext *cct, utime_t arrived, PerfCounters *perfcounter, bufferlist *out_bl, Context *on_finish)
+    : m_cct(cct), m_on_finish(on_finish), m_out_bl(out_bl),
+      m_arrived_time(arrived), m_perfcounter(perfcounter) {}
+  ~C_ReadRequest() {}
+
+  void finish(int r) override;
+
+  const char *get_name() const {
+    return "C_ReadRequest";
+  }
+
+private:
+  CephContext *m_cct;
+  Context *m_on_finish;
+  bufferlist *m_out_bl;
+  utime_t m_arrived_time;
+  PerfCounters *m_perfcounter;
+};
+
 struct BlockGuardReqState {
   bool barrier = false; /* This is a barrier request */
   bool current_barrier = false; /* This is the currently active barrier */

src/librbd/cache/rwl/Types.h

@@ -141,6 +141,9 @@ namespace librbd {
 namespace cache {
 namespace rwl {
 
+class ImageExtentBuf;
+typedef std::vector<ImageExtentBuf> ImageExtentBufs;
+
 const int IN_FLIGHT_FLUSH_WRITE_LIMIT = 64;
 const int IN_FLIGHT_FLUSH_BYTES_LIMIT = (1 * 1024 * 1024);
 
@@ -265,6 +268,15 @@ BlockExtent block_extent(const io::Extent& image_extent);
 
 Context * override_ctx(int r, Context *ctx);
 
+class ImageExtentBuf : public io::Extent {
+public:
+  bufferlist m_bl;
+  ImageExtentBuf(io::Extent extent)
+    : io::Extent(extent) { }
+  ImageExtentBuf(io::Extent extent, bufferlist bl)
+    : io::Extent(extent), m_bl(bl) { }
+};
+
 } // namespace rwl
 } // namespace cache
 } // namespace librbd