From: Yuan Lu <yuan.y.lu@intel.com>
Date: Thu, 30 Apr 2020 06:10:19 +0000 (+0800)
Subject: librbd: add CompAndWriteRequest
X-Git-Tag: v17.0.0~2429^2~2
X-Git-Url: http://git.apps.os.sepia.ceph.com/?a=commitdiff_plain;h=5d719ff919ef790a235808ed325a7e190e83205f;p=ceph.git

librbd: add CompAndWriteRequest

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>
---

diff --git a/src/librbd/cache/rwl/Request.cc b/src/librbd/cache/rwl/Request.cc
index 8dc6f4c531df6..147fe0cce3d17 100644
--- a/src/librbd/cache/rwl/Request.cc
+++ b/src/librbd/cache/rwl/Request.cc
@@ -622,6 +622,54 @@ std::ostream &operator<<(std::ostream &os,
   return os;
 };
 
+template <typename T>
+C_CompAndWriteRequest<T>::C_CompAndWriteRequest(T &rwl, const utime_t arrived, io::Extents &&image_extents,
+                                                bufferlist&& cmp_bl, bufferlist&& bl, uint64_t *mismatch_offset,
+                                                int fadvise_flags, ceph::mutex &lock, PerfCounters *perfcounter,
+                                                Context *user_req)
+  : C_WriteRequest<T>(rwl, arrived, std::move(image_extents), std::move(bl), fadvise_flags, lock, perfcounter, user_req),
+  mismatch_offset(mismatch_offset), cmp_bl(std::move(cmp_bl)) {
+  ldout(rwl.get_context(), 20) << dendl;
+}
+
+template <typename T>
+C_CompAndWriteRequest<T>::~C_CompAndWriteRequest() {
+  ldout(rwl.get_context(), 20) << dendl;
+}
+
+template <typename T>
+void C_CompAndWriteRequest<T>::finish_req(int r) {
+  if (compare_succeeded) {
+    C_WriteRequest<T>::finish_req(r);
+  } else {
+    utime_t now = ceph_clock_now();
+    update_req_stats(now);
+  }
+}
+
+template <typename T>
+void C_CompAndWriteRequest<T>::update_req_stats(utime_t &now) {
+  /* Compare-and-write stats. Compare-and-write excluded from most write
+   * stats because the read phase will make them look like slow writes in
+   * those histograms. */
+  if (!compare_succeeded) {
+    this->m_perfcounter->inc(l_librbd_rwl_cmp_fails, 1);
+  }
+  utime_t comp_latency = now - this->m_arrived_time;
+  this->m_perfcounter->tinc(l_librbd_rwl_cmp_latency, comp_latency);
+}
+
+template <typename T>
+std::ostream &operator<<(std::ostream &os,
+                         const C_CompAndWriteRequest<T> &req) {
+  os << (C_WriteRequest<T>&)req
+     << "cmp_bl=" << req.cmp_bl << ", "
+     << "read_bl=" << req.read_bl << ", "
+     << "compare_succeeded=" << req.compare_succeeded << ", "
+     << "mismatch_offset=" << req.mismatch_offset;
+  return os;
+};
+
 std::ostream &operator<<(std::ostream &os,
                          const BlockGuardReqState &r) {
   os << "barrier=" << r.barrier << ", "
diff --git a/src/librbd/cache/rwl/Request.h b/src/librbd/cache/rwl/Request.h
index c77ac448f8fd0..bc8ef9327a6f5 100644
--- a/src/librbd/cache/rwl/Request.h
+++ b/src/librbd/cache/rwl/Request.h
@@ -336,6 +336,44 @@ public:
                                   const C_WriteSameRequest<U> &req);
 };
 
+/**
+ * This is the custodian of the BlockGuard cell for this compare and write. The
+ * block guard is acquired before the read begins to guarantee atomicity of this
+ * operation.  If this results in a write, the block guard will be released
+ * when the write completes to all replicas.
+ */
+template <typename T>
+class C_CompAndWriteRequest : public C_WriteRequest<T> {
+public:
+  using C_BlockIORequest<T>::rwl;
+  bool compare_succeeded = false;
+  uint64_t *mismatch_offset;
+  bufferlist cmp_bl;
+  bufferlist read_bl;
+  C_CompAndWriteRequest(T &rwl, const utime_t arrived, io::Extents &&image_extents,
+                        bufferlist&& cmp_bl, bufferlist&& bl, uint64_t *mismatch_offset,
+                        int fadvise_flags, ceph::mutex &lock, PerfCounters *perfcounter,
+                        Context *user_req);
+  ~C_CompAndWriteRequest();
+
+  void finish_req(int r) override;
+
+  void update_req_stats(utime_t &now) override;
+
+  /*
+   * Compare and write doesn't implement alloc_resources(), deferred_handler(),
+   * or dispatch(). We use the implementation in C_WriteRequest(), and only if the
+   * compare phase succeeds and a write is actually performed.
+   */
+
+  const char *get_name() const override {
+    return "C_CompAndWriteRequest";
+  }
+  template <typename U>
+  friend std::ostream &operator<<(std::ostream &os,
+                                  const C_CompAndWriteRequest<U> &req);
+};
+
 struct BlockGuardReqState {
   bool barrier = false; /* This is a barrier request */
   bool current_barrier = false; /* This is the currently active barrier */