Restore zero-copy buffers in OSD fast path.

This change restores volatile sharing semantics in the Message
decode path, and also in the OSD write path for FileStore/FileJournal.

This can be verified with a breakpoint set at the clone/COW case in
buffer::ptr::clone_nonsharable(currently buffer.cc:690).

Signed-off-by: Matt Benjamin <matt@cohortfs.com>

Author: Matt Benjamin

src/msg/Message.h

@@ -314,33 +314,33 @@ class Message : public RefCountedObject {
   void set_payload(bufferlist& bl) {
     if (byte_throttler)
       byte_throttler->put(payload.length());
-    payload.claim(bl);
+    payload.claim(bl, false /* !clone_nonsharable */);
     if (byte_throttler)
       byte_throttler->take(payload.length());
   }
 
   void set_middle(bufferlist& bl) {
     if (byte_throttler)
       byte_throttler->put(payload.length());
-    middle.claim(bl);
+    middle.claim(bl, false /* !clone_nonsharable */);
     if (byte_throttler)
       byte_throttler->take(payload.length());
   }
   bufferlist& get_middle() { return middle; }
 
-  void set_data(const bufferlist &d) {
+  void set_data(bufferlist &bl) {
     if (byte_throttler)
       byte_throttler->put(data.length());
-    data = d;
+    data.claim(bl, false /* !clone_nonsharable */);
     if (byte_throttler)
       byte_throttler->take(data.length());
   }
 
   bufferlist& get_data() { return data; }
-  void claim_data(bufferlist& bl, bool strong=true) {
+  void claim_data(bufferlist& bl, bool clone_nonsharable=true) {
     if (byte_throttler)
       byte_throttler->put(data.length());
-    bl.claim(data, strong);
+    bl.claim(data, clone_nonsharable);
   }
   off_t get_data_len() { return data.length(); }
 

src/os/FileJournal.cc

@@ -913,7 +913,7 @@ int FileJournal::prepare_single_write(bufferlist& bl, off64_t& queue_pos, uint64
     bufferptr bp = buffer::create_static(pre_pad, zero_buf);
     bl.push_back(bp);
   }
-  bl.claim_append(ebl);
+  bl.claim_append(ebl, false /* !clone_nonsharable */); // potential zero-copy
 
   if (h.post_pad) {
     bufferptr bp = buffer::create_static(post_pad, zero_buf);

src/os/FileJournal.h

@@ -54,7 +54,7 @@ class FileJournal : public Journal {
     TrackedOpRef tracked_op;
     write_item(uint64_t s, bufferlist& b, int al, TrackedOpRef opref) :
       seq(s), alignment(al), tracked_op(opref) {
-      bl.claim(b);
+      bl.claim(b, false /* !clone_nonsharable */); // potential zero-copy
     }
     write_item() : seq(0), alignment(0) {}
   };