Check block number against the correct fork in get_raw_page().

get_raw_page tried to validate the supplied block number against
RelationGetNumberOfBlocks(), which of course is only right when
accessing the main fork.  In most cases, the main fork is longer
than the others, so that the check was too weak (allowing a
lower-level error to be reported, but no real harm to be done).
However, very small tables could have an FSM larger than their heap,
in which case the mistake prevented access to some FSM pages.
Per report from Torsten Foertsch.

In passing, make the bad-block-number error into an ereport not elog
(since it's certainly not an internal error); and fix sloppily
maintained comment for RelationGetNumberOfBlocksInFork.

This has been wrong since we invented relation forks, so back-patch
to all supported branches.

diff --git a/contrib/pageinspect/rawpage.c b/contrib/pageinspect/rawpage.c
index 9043fa37bd9bbfce8e15d65a22a75f46aea6871b..d91bcfc1b1cb8b3aceb30d25494b62d8cdee9ad3 100644 (file)
--- a/contrib/pageinspect/rawpage.c
+++ b/contrib/pageinspect/rawpage.c
@@ -24,6 +24,7 @@
 #include "funcapi.h"
 #include "miscadmin.h"
 #include "storage/bufmgr.h"
+#include "storage/smgr.h"
 #include "utils/builtins.h"
 
 PG_MODULE_MAGIC;
@@ -130,9 +131,13 @@ get_raw_page_internal(text *relname, ForkNumber forknum, BlockNumber blkno)
                                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                 errmsg("cannot access temporary tables of other sessions")));
 
-       if (blkno >= RelationGetNumberOfBlocks(rel))
-               elog(ERROR, "block number %u is out of range for relation \"%s\"",
-                        blkno, RelationGetRelationName(rel));
+       RelationOpenSmgr(rel);
+
+       if (blkno >= smgrnblocks(rel->rd_smgr, forknum))
+               ereport(ERROR,
+                               (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+                                errmsg("block number %u is out of range for relation \"%s\"",
+                                               blkno, RelationGetRelationName(rel))));
 
        /* Initialize buffer to copy to */
        raw_page = (bytea *) palloc(BLCKSZ + VARHDRSZ);