librbd: make rename work with any header format

Instead of interpreting the header, just copy all the data and
omap values from the original header to the newly name one.
This will continue working with future header changes.

We can create the new header and write all data and omap values
to it atomically to avoid some races.

Signed-off-by: Josh Durgin <josh.durgin@inktank.com>

diff --git a/src/librbd.cc b/src/librbd.cc
index 1c89b703d7e7b58d700140587975944bfa2c0a40..5e34e1623c4dc71b647f0c62305ad4b37c45d948 100644 (file)
--- a/src/librbd.cc
+++ b/src/librbd.cc
@@ -1026,45 +1026,77 @@ int create(IoCtx& io_ctx, const char *imgname, uint64_t size, int *order)
 int rename(IoCtx& io_ctx, const char *srcname, const char *dstname)
 {
   CephContext *cct = (CephContext *)io_ctx.cct();
-  ldout(cct, 20) << "rename " << &io_ctx << " " << srcname << " -> " << dstname << dendl;
+  ldout(cct, 20) << "rename " << &io_ctx << " " << srcname << " -> "
+                << dstname << dendl;
 
-  string md_oid = srcname;
-  md_oid += RBD_SUFFIX;
-  string dst_md_oid = dstname;
-  dst_md_oid += RBD_SUFFIX;
-  string dstname_str = dstname;
-  string imgname_str = srcname;
-  uint64_t ver;
-  bufferlist header;
-  int r = read_header_bl(io_ctx, md_oid, header, &ver);
+  bool old_format;
+  uint64_t header_size;
+  int r = detect_format(io_ctx, srcname, &old_format, &header_size);
+  if (r < 0) {
+    lderr(cct) << "error finding header: " << cpp_strerror(r) << dendl;
+    return r;
+  }
+
+  string header_oid = md_oid(srcname, old_format);
+  string dst_header_oid = md_oid(dstname, old_format);
+  bufferlist headerbl;
+  map<string, bufferlist> omap_values;
+  r = io_ctx.read(header_oid, headerbl, header_size, 0);
   if (r < 0) {
-    lderr(cct) << "error reading header: " << md_oid << ": " << cpp_strerror(-r) << dendl;
+    lderr(cct) << "error reading header: " << header_oid << ": "
+              << cpp_strerror(-r) << dendl;
     return r;
   }
-  r = io_ctx.stat(dst_md_oid, NULL, NULL);
+
+  int MAX_READ = 1024;
+  string last_read = "";
+  do {
+    map<string, bufferlist> outbl;
+    r = io_ctx.omap_get_vals(header_oid, last_read, MAX_READ, &outbl);
+    if (r < 0) {
+      lderr(cct) << "error reading header omap values: " << cpp_strerror(r)
+                << dendl;
+      return r;
+    }
+    omap_values.insert(outbl.begin(), outbl.end());
+    if (outbl.size() > 0)
+      last_read = outbl.rbegin()->first;
+  } while (r == MAX_READ);
+
+  r = io_ctx.stat(dst_header_oid, NULL, NULL);
   if (r == 0) {
-    lderr(cct) << "rbd image header " << dst_md_oid << " already exists" << dendl;
+    lderr(cct) << "rbd image header " << dst_header_oid
+              << " already exists" << dendl;
     return -EEXIST;
   }
-  r = write_header(io_ctx, dst_md_oid, header);
+  librados::ObjectWriteOperation op;
+  op.create(true);
+  op.write_full(headerbl);
+  op.omap_set(omap_values);
+  r = io_ctx.operate(dst_header_oid, &op);
   if (r < 0) {
-    lderr(cct) << "error writing header: " << dst_md_oid << ": " << cpp_strerror(-r) << dendl;
+    lderr(cct) << "error writing header: " << dst_header_oid << ": "
+              << cpp_strerror(r) << dendl;
     return r;
   }
-  r = tmap_set(io_ctx, dstname_str);
+
+  r = tmap_set(io_ctx, dstname);
   if (r < 0) {
-    io_ctx.remove(dst_md_oid);
-    lderr(cct) << "can't add " << dst_md_oid << " to directory" << dendl;
+    io_ctx.remove(dst_header_oid);
+    lderr(cct) << "couldn't add " << dstname << " to directory: "
+              << cpp_strerror(r) << dendl;
     return r;
   }
-  r = tmap_rm(io_ctx, imgname_str);
+  r = tmap_rm(io_ctx, srcname);
   if (r < 0)
-    lderr(cct) << "warning: couldn't remove old entry from directory (" << imgname_str << ")" << dendl;
+    lderr(cct) << "warning: couldn't remove old entry from directory ("
+              << srcname << ")" << dendl;
 
-  r = io_ctx.remove(md_oid);
+  r = io_ctx.remove(header_oid);
   if (r < 0 && r != -ENOENT)
-    lderr(cct) << "warning: couldn't remove old metadata" << dendl;
-  notify_change(io_ctx, md_oid, NULL, NULL);
+    lderr(cct) << "warning: couldn't remove old header object ("
+              << header_oid << ")" << dendl;
+  notify_change(io_ctx, header_oid, NULL, NULL);
 
   return 0;
 }