Fix some page-locking bugs.

diff --git a/src/backend/access/conveyor/conveyor.c b/src/backend/access/conveyor/conveyor.c
index 12a188884d8b5b402d9e59473e7d06660f94ba53..090fccc3c0c729546d068332982bc8673b62d69f 100644 (file)
--- a/src/backend/access/conveyor/conveyor.c
+++ b/src/backend/access/conveyor/conveyor.c
@@ -1282,6 +1282,7 @@ ConveyorBeltClearIndexSegmentEntries(ConveyorBelt *cb, Buffer metabuffer,
                                elog(ERROR,
                                         "non-final index segment page at segno %u offset %u should be initialized",
                                         index_segment, segoff);
+                       UnlockReleaseBuffer(indexbuffer);
                        return true;
                }
 
@@ -1302,8 +1303,9 @@ ConveyorBeltClearIndexSegmentEntries(ConveyorBelt *cb, Buffer metabuffer,
                 * Loop over the index entries in this page.
                 *
                 * At the top of each iteration of the loop, the index page is
-                * exclusively locked. The lock may be released and reacquired before
-                * beginning the next iteration.
+                * pinned and exclusively locked. The lock may be released and
+                * reacquired before beginning the next iteration. The pin is retained
+                * the whole time.
                 */
                while (pageoffset < CB_INDEXPAGE_INDEX_ENTRIES)
                {
@@ -1316,7 +1318,6 @@ ConveyorBeltClearIndexSegmentEntries(ConveyorBelt *cb, Buffer metabuffer,
                        if (segno == CB_INVALID_SEGMENT)
                        {
                                /* No items remain in this page. */
-                               UnlockReleaseBuffer(indexbuffer);
                                break;
                        }
                        if (first_page + (cb->cb_pages_per_segment * pageoffset) +
@@ -1422,6 +1423,9 @@ ConveyorBeltClearIndexSegmentEntries(ConveyorBelt *cb, Buffer metabuffer,
                        /* Now we're no longer prepared to clear any segment. */
                        cleared_segno = CB_INVALID_SEGMENT;
                }
+
+               /* Release index page lock and pin. */
+               UnlockReleaseBuffer(indexbuffer);
        }
 
        return true;
@@ -1489,7 +1493,8 @@ ConveyorBeltFreeOldestIndexSegment(ConveyorBelt *cb, Buffer metabuffer,
         * any better.
         */
        LockBuffer(firstindexbuffer, BUFFER_LOCK_EXCLUSIVE);
-       LockBuffer(fsmbuffer, BUFFER_LOCK_EXCLUSIVE);
+       if (fsmblock != InvalidBlockNumber)
+               LockBuffer(fsmbuffer, BUFFER_LOCK_EXCLUSIVE);
        if (ConditionalLockBufferForCleanup(metabuffer))
        {
                oldest_remaining_index_segment =