osd: trim copy-get backend read to object size

We are passing a big number to the backend to read and it is trimming it
to the stripe boundary, and then setting the cursor at a slightly smaller
offset bound by oi.size.  This is invalid, and will trigger an assert in
the _write_copy_chunk code:

     0> 2014-03-21 15:12:23.761509 7f8dd2324700 -1 osd/ReplicatedPG.cc: In function 'void ReplicatedPG::_write_copy_chunk(ReplicatedPG::CopyOpRef, PGBackend::PGTransaction*)' thread 7f8dd2324700 time 2014-03-21 15:12:23.758866
osd/ReplicatedPG.cc: 5554: FAILED assert(cop->data.length() + cop->temp_cursor.data_offset == cop->cursor.data_offset)

To fix this, trim the buffer to the correct length in the completion
context.

Fixes: #7823
Signed-off-by: Sage Weil <sage@inktank.com>

diff --git a/src/osd/ReplicatedPG.cc b/src/osd/ReplicatedPG.cc
index faf00a720acac08de328df8a5acf0b41401d678b..4004432891e3c7c6e0cc9931a755d9b9bc2a71a8 100644 (file)
--- a/src/osd/ReplicatedPG.cc
+++ b/src/osd/ReplicatedPG.cc
@@ -5202,9 +5202,15 @@ struct C_CopyFrom_AsyncReadCb : public Context {
   OSDOp *osd_op;
   object_copy_data_t reply_obj;
   bool classic;
+  size_t len;
   C_CopyFrom_AsyncReadCb(OSDOp *osd_op, bool classic) :
-    osd_op(osd_op), classic(classic) {}
+    osd_op(osd_op), classic(classic), len(0) {}
   void finish(int r) {
+    assert(len > 0);
+    assert(len <= reply_obj.data.length());
+    bufferlist bl;
+    bl.substr_of(reply_obj.data, 0, len);
+    reply_obj.data.swap(bl);
     if (classic) {
       reply_obj.encode_classic(osd_op->outdata);
     } else {
@@ -5282,6 +5288,7 @@ int ReplicatedPG::fill_in_copy_get(
            make_pair(cursor.data_offset, left),
            make_pair(&bl, cb)));
        result = MIN(oi.size - cursor.data_offset, (uint64_t)left);
+       cb->len = result;
       } else {
        result = pgbackend->objects_read_sync(
          oi.soid, cursor.data_offset, left, &bl);