In certain cases with BerkleyDB 5.3.x we are getting the error:

db3.c:1443: dbcursor->pget(-30999): BDB0063 DB_BUFFER_SMALL: User memory too small for return value

See https://bugs.launchpad.net/rpm/+bug/934420 for more information.

It appears to be some type of a bug in the BerkleyDB 5.3.x.  In an attempt
to workaround the problem, when we encounter this situation we attempt
to adjust the size of the mmap buffer until the call works, or we
end up trying 25 times.  The new size is either the updated vp->size
from the failed pget call, or the previous size + 4096.

If DBI debugging is enabled, additional diagnostics are printed, otherwise
a basic retry and success message is added to show that the failure was
resolved.

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>

Index: rpm-5.4.9/rpmdb/rpmdb.c
===================================================================
--- rpm-5.4.9.orig/rpmdb/rpmdb.c
+++ rpm-5.4.9/rpmdb/rpmdb.c
@@ -2212,8 +2212,12 @@ static int rpmmiGet(dbiIndex dbi, DBC * 
 	vp->flags |= DB_DBT_USERMEM;
 	rc = dbiGet(dbi, dbcursor, kp, vp, flags);
 	if (rc == DB_BUFFER_SMALL) {
+	    int retry = 0;
+	    size_t origlen = vp->size;
 	    size_t uhlen = vp->size;
-	    void * uh = mmap(NULL, uhlen, _prot, _flags, _fdno, _off);
+	    void * uh;
+retry_get:
+	    uh = mmap(NULL, uhlen, _prot, _flags, _fdno, _off);
 	    if (uh == NULL || uh == (void *)-1)
 		fprintf(stderr,
 		    "==> mmap(%p[%u], 0x%x, 0x%x, %d, 0x%x) error(%d): %s\n",
@@ -2235,6 +2239,25 @@ static int rpmmiGet(dbiIndex dbi, DBC * 
 		if (munmap(uh, uhlen) != 0)
 		    fprintf(stderr, "==> munmap(%p[%u]) error(%d): %s\n",
                 	uh, (unsigned)uhlen, errno, strerror(errno));
+	        /* We want to be sure to limit the number of retry attempts to avoid a loop! */
+	        if (rc == DB_BUFFER_SMALL && retry < 25) {
+		   /* If we got a largr vp-size back, use that, otherwise increment the size by 1k */
+	           uhlen = vp->size > uhlen ? vp->size : uhlen + 4096;
+		   retry++;
+	           if (_rpmmi_debug || (dbi)->dbi_debug)
+	               fprintf(stderr, "==> DB_BUFFER_SMALL orig requested (%d), configured (%d), forcing larger buffer (%d), new size (%d)\n",
+	                    origlen, vp->ulen, uhlen, vp->size);
+	           else
+	               fprintf(stderr, "==> retry (%d) db3cpget (%d)\n", retry, uhlen);
+	           goto retry_get;
+	        }
+	    }
+	    if (retry) {
+	        if (_rpmmi_debug || (dbi)->dbi_debug)
+	           fprintf(stderr, "==> success orig requested (%d), configured buffer (%d), buffer (%d), size after dbiGet (%d)\n",
+			origlen, vp->ulen, uhlen, vp->size);
+	        else
+	           fprintf(stderr, "==> success\n");
 	    }
 	}
     } else
Index: rpm-5.4.9/rpmdb/db3.c
===================================================================
--- rpm-5.4.9.orig/rpmdb/db3.c
+++ rpm-5.4.9/rpmdb/db3.c
@@ -1442,6 +1442,8 @@
 	rc = dbcursor->pget(dbcursor, key, pkey, data, flags);
 	/* XXX DB_NOTFOUND can be returned */
 	_printit = (rc == DB_NOTFOUND ? 0 : _debug);
+//	/* XXX Permit DB_BUFFER_SMALL to be returned (more restrictive?) */
+//	_printit = (rc == DB_BUFFER_SMALL ? 0 : _printit);
 	rc = cvtdberr(dbi, "dbcursor->pget", rc, _printit);
 #else
 	/* XXX db3 does DB_FIRST on uninitialized cursor */
@@ -1452,7 +1452,7 @@ assert(db != NULL);
 #endif
     }
 
-DBIDEBUG(dbi, (stderr, "<-- %s(%p,%p,%p,%p,%p,0x%x) rc %d %s%s\n", __FUNCTION__, dbi, dbcursor, key, pkey, data, flags, rc, _DBCFLAGS(flags), _KEYDATA(key, pkey, data, NULL)));
+DBIDEBUG(dbi, (stderr, "<-- %s(%p,%p,%p,%p,%p,0x%x) rc %d %s%s\n", __FUNCTION__, dbi, dbcursor, key, pkey, data, flags, rc, _DBCFLAGS(flags), _KEYDATA(key, pkey, rc == DB_BUFFER_SMALL ? NULL : data, NULL)));
     return rc;
 }
 /*@=mustmod@*/