librados: cleanly define SNAP_HEAD, SNAP_DIR constants

We were using the internal CEPH_NOSNAP and CEPH_SNAPDIR constants, and
defining a clone_info_t::HEAD (with a different value).  The docs were
referrring to the internal constant names.

Instead, define librados constants (C and C++) with the same values as the
internal types.

Note that this changes the clone_info_t::HEAD value from -1 to -2 so that
it now matches the internal type.

Signed-off-by: Sage Weil <sage@inktank.com>

doc/PendingReleaseNotes

@@ -0,0 +1,4 @@
+
+* The librados::clone_info_t::HEAD constant has been replaced with librados::SNAP_HEAD, with
+  a different value that matches the internal constants.  This only affects the brand-new
+  list_snaps() interface that was introduced in v0.59.

src/include/rados/librados.h

@@ -51,6 +51,12 @@ enum {
 /** @endcond */
 /** @} */
 
+/*
+ * snap id contants
+ */
+#define LIBRADOS_SNAP_HEAD  ((uint64_t)(-2))
+#define LIBRADOS_SNAP_DIR   ((uint64_t)(-1))
+
 /**
  * @typedef rados_t
  *
@@ -727,7 +733,7 @@ int rados_rollback(rados_ioctx_t io, const char *oid,
  * snapshot.
  *
  * @param io the io context to change
- * @param snap the id of the snapshot to set, or CEPH_NOSNAP for no
+ * @param snap the id of the snapshot to set, or LIBRADOS_SNAP_HEAD for no
  * snapshot (i.e. normal operation)
  */
 void rados_ioctx_snap_set_read(rados_ioctx_t io, rados_snap_t snap);
@@ -1343,7 +1349,7 @@ void rados_aio_release(rados_completion_t c);
  * @param len length of the data, in bytes
  * @param off byte offset in the object to begin writing at
  * @returns 0 on success, -EROFS if the io context specifies a snap_seq
- * other than CEPH_NOSNAP
+ * other than LIBRADOS_SNAP_HEAD
  */
 int rados_aio_write(rados_ioctx_t io, const char *oid,
 		    rados_completion_t completion,
@@ -1363,7 +1369,7 @@ int rados_aio_write(rados_ioctx_t io, const char *oid,
  * @param buf the data to append
  * @param len length of buf (in bytes)
  * @returns 0 on success, -EROFS if the io context specifies a snap_seq
- * other than CEPH_NOSNAP
+ * other than LIBRADOS_SNAP_HEAD
  */
 int rados_aio_append(rados_ioctx_t io, const char *oid,
 		     rados_completion_t completion,
@@ -1385,7 +1391,7 @@ int rados_aio_append(rados_ioctx_t io, const char *oid,
  * @param buf data to write
  * @param len length of the data, in bytes
  * @returns 0 on success, -EROFS if the io context specifies a snap_seq
- * other than CEPH_NOSNAP
+ * other than LIBRADOS_SNAP_HEAD
  */
 int rados_aio_write_full(rados_ioctx_t io, const char *oid,
 			 rados_completion_t completion,
@@ -1403,7 +1409,7 @@ int rados_aio_write_full(rados_ioctx_t io, const char *oid,
  * @param oid the name of the object
  * @param completion what to do when the remove is safe and complete
  * @returns 0 on success, -EROFS if the io context specifies a snap_seq
- * other than CEPH_NOSNAP
+ * other than LIBRADOS_SNAP_HEAD
  */
 int rados_aio_remove(rados_ioctx_t io, const char *oid,
 		     rados_completion_t completion);

src/include/rados/librados.hpp

@@ -333,12 +333,12 @@ namespace librados
      * list snapshot clones associated with a logical object
      *
      * This will include a record for each version of the object,
-     * include the "HEAD" (which will have a cloneid of
-     * librados::clone_info_t::HEAD).  Each clone includes a vector
-     * of snap ids for which it is defined to exist.
+     * include the "HEAD" (which will have a cloneid of SNAP_HEAD).
+     * Each clone includes a vector of snap ids for which it is
+     * defined to exist.
      *
      * NOTE: this operation must be submitted from an IoCtx with a
-     * read snapid of CEPH_SNAPDIR for reliable results.
+     * read snapid of SNAP_DIR for reliable results.
      *
      * @param out_snaps [out] pointer to resulting snap_set_t
      * @param prval [out] place error code in prval upon completion
@@ -538,7 +538,7 @@ namespace librados
      * @param oid the name of the object
      * @param completion what to do when the remove is safe and complete
      * @returns 0 on success, -EROFS if the io context specifies a snap_seq
-     * other than CEPH_NOSNAP
+     * other than SNAP_HEAD
      */
     int aio_remove(const std::string& oid, AioCompletion *c);
 

src/include/rados/rados_types.hpp

@@ -9,8 +9,12 @@ namespace librados {
 
 typedef uint64_t snap_t;
 
+enum {
+  SNAP_HEAD = (uint64_t)(-2),
+  SNAP_DIR = (uint64_t)(-1)
+};
+
 struct clone_info_t {
-  static const snap_t HEAD = ((snap_t)-1);
   snap_t cloneid;
   std::vector<snap_t> snaps;          // ascending
   std::vector< std::pair<uint64_t,uint64_t> > overlap;  // with next newest

src/librbd/internal.cc

@@ -2387,7 +2387,7 @@ namespace librbd {
 	bool end_exists;
 	calc_snap_set_diff(ictx->cct, snap_set,
 			   from_snap_id,
-			   end_snap_id == CEPH_NOSNAP ? librados::clone_info_t::HEAD : end_snap_id,
+			   end_snap_id,
 			   &diff, &end_exists);
 	ldout(ictx->cct, 20) << "  diff " << diff << " end_exists=" << end_exists << dendl;
 	if (diff.empty())

src/osd/ReplicatedPG.cc

@@ -2373,7 +2373,7 @@ int ReplicatedPG::do_osd_ops(OpContext *ctx, vector<OSDOp>& ops)
         if (ssc->snapset.head_exists) {
           assert(obs.exists);
           clone_info ci;
-          ci.cloneid = clone_info::HEAD;
+          ci.cloneid = CEPH_NOSNAP;
 
           //Size for HEAD is oi.size
           ci.size = oi.size;

src/osd/osd_types.cc

@@ -20,8 +20,6 @@ extern "C" {
 #include "PG.h"
 #include "OSDMap.h"
 
-const snapid_t clone_info::HEAD((uint64_t)-1);
-
 // -- osd_reqid_t --
 void osd_reqid_t::encode(bufferlist &bl) const
 {

src/osd/osd_types.h

@@ -2114,8 +2114,6 @@ struct obj_list_watch_response_t {
 WRITE_CLASS_ENCODER(obj_list_watch_response_t)
 
 struct clone_info {
-  static const snapid_t HEAD;
-
   snapid_t cloneid;
   vector<snapid_t> snaps;  // ascending
   vector< pair<uint64_t,uint64_t> > overlap;
@@ -2140,7 +2138,7 @@ struct clone_info {
     DECODE_FINISH(bl);
   }
   void dump(Formatter *f) const {
-    if (cloneid == HEAD)
+    if (cloneid == CEPH_NOSNAP)
       f->dump_string("cloneid", "HEAD");
     else
       f->dump_unsigned("cloneid", cloneid.val);
@@ -2171,7 +2169,7 @@ struct clone_info {
     o.back()->overlap.push_back(pair<uint64_t,uint64_t>(8192,4096));
     o.back()->size = 16384;
     o.push_back(new clone_info);
-    o.back()->cloneid = HEAD;
+    o.back()->cloneid = CEPH_NOSNAP;
     o.back()->size = 32768;
   }
 };
@@ -2220,7 +2218,7 @@ struct obj_list_snap_response_t {
     cl.overlap.push_back(pair<uint64_t,uint64_t>(8192,4096));
     cl.size = 16384;
     o.back()->clones.push_back(cl);
-    cl.cloneid = clone_info::HEAD;
+    cl.cloneid = CEPH_NOSNAP;
     cl.snaps.clear();
     cl.overlap.clear();
     cl.size = 32768;

src/osdc/snap_set_diff.cc

@@ -31,7 +31,7 @@ void calc_snap_set_diff(CephContext *cct, const librados::snap_set_t& snap_set,
     // include itself in the snaps list
     librados::snap_t a, b;
     b = r->cloneid;
-    if (b == librados::clone_info_t::HEAD) {
+    if (b == librados::SNAP_HEAD) {
       // head is valid starting from right after the last seen seq
       a = snap_set.seq + 1;
     } else {

src/rados.cc

@@ -2061,7 +2061,7 @@ static int rados_tool_common(const std::map < std::string, std::string > &opts,
 
       if (formatter) formatter->open_object_section("clone");
 
-      if (ci->cloneid == clone_info_t::HEAD) {
+      if (ci->cloneid == librados::SNAP_HEAD) {
         if (formatter)
           formatter->dump_string("id", "head");
         else
@@ -2110,7 +2110,7 @@ static int rados_tool_common(const std::map < std::string, std::string > &opts,
         cout << "\t" << ci->size;
       }
 
-      if (ci->cloneid != clone_info_t::HEAD) {
+      if (ci->cloneid != librados::SNAP_HEAD) {
         if (formatter)
           formatter->open_array_section("overlaps");
         else

src/test/librados/snapshots.cc

@@ -332,7 +332,7 @@ TEST(LibRadosSnapshots, SelfManagedSnapRollbackPP) {
 
   snap_set_t ss;
 
-  snap_t head = clone_info_t::HEAD;
+  snap_t head = SNAP_HEAD;
   ASSERT_EQ(0, ioctx.list_snaps("foo", &ss));
   ASSERT_EQ(1u, ss.clones.size());
   ASSERT_EQ(head, ss.clones[0].cloneid);
@@ -415,7 +415,7 @@ TEST(LibRadosSnapshots, SelfManagedSnapOverlapPP) {
   ASSERT_EQ((int)sizeof(buf), ioctx.write("foo", bl1, sizeof(buf), bufsize*8));
 
   snap_set_t ss;
-  snap_t head = clone_info_t::HEAD;
+  snap_t head = SNAP_HEAD;
   ASSERT_EQ(0, ioctx.list_snaps("foo", &ss));
   ASSERT_EQ(1u, ss.clones.size());
   ASSERT_EQ(head, ss.clones[0].cloneid);