os/kstore: fix bugs in read stripe logic

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

diff --git a/src/os/kstore/KStore.cc b/src/os/kstore/KStore.cc
index 3b768210877ae1aa5e0b221cbdd144713f4f901c..1151436e99d00c64a34960507606039d9a0b2afe 100644 (file)
--- a/src/os/kstore/KStore.cc
+++ b/src/os/kstore/KStore.cc
@@ -1554,34 +1554,35 @@ int KStore::_do_read(
     db->get(PREFIX_DATA, key, &stripe);
     dout(30) << __func__ << " stripe " << offset - stripe_off << " got "
             << stripe.length() << dendl;
-    unsigned slen = MIN(stripe_size, length);
+    unsigned swant = MIN(stripe_size - stripe_off, length);
     if (stripe.length()) {
-      if (slen == stripe.length()) {
+      if (swant == stripe.length()) {
        bl.claim_append(stripe);
        dout(30) << __func__ << " taking full stripe" << dendl;
       } else {
        unsigned l = 0;
        if (stripe_off < stripe.length()) {
-         assert(bl.length() == 0);
-         l = MIN(stripe.length() - stripe_off, slen);
-         bl.substr_of(stripe, stripe_off, l);
+         l = MIN(stripe.length() - stripe_off, swant);
+         bufferlist t;
+         t.substr_of(stripe, stripe_off, l);
+         bl.claim_append(t);
          dout(30) << __func__ << " taking " << stripe_off << "~" << l << dendl;
        }
-       if (l < slen) {
-         bufferptr z(slen - l);
+       if (l < swant) {
+         bufferptr z(swant - l);
          z.zero();
          bl.append(z);
          dout(30) << __func__ << " adding " << z.length() << " zeros" << dendl;
        }
       }
     } else {
-      dout(30) << __func__ << " generating zeros 0~" << slen << dendl;
-      bufferptr z(slen);
+      dout(30) << __func__ << " generating " << swant << " zeros" << dendl;
+      bufferptr z(swant);
       z.zero();
       bl.append(z);
     }
-    offset += slen;
-    length -= slen;
+    offset += swant;
+    length -= swant;
     stripe_off = 0;
   }
   r = bl.length();