From: Daniel Gustafsson <dgustafsson@postgresql.org>
Date: Tue, 4 Aug 2026 10:16:55 +0000 (+0200)
Subject: Do not reuse rd_smgr in fork loop when enabling data checksums
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=ab918a4fab0a6a8855b230d140bbf89fb090ad3e;p=thirdparty%2Fpostgresql.git

Do not reuse rd_smgr in fork loop when enabling data checksums

ProcessSingleRelationByOid called RelationGetSmgr(rel), discarded the
result, and then read rel->rd_smgr directly when looping over forks.
Only RelationGetSmgr is authorized to read that field since a relcache
invalidation resets rd_smgr to NULL.

Backpatch to v19 where online checksums were introduced.

Author: Mihail Nikalayeu <mihailnikalayeu@gmail.com>
Reviewed-by: ChangAo Chen <cca5507@qq.com>
Reviewed-by: Fujii Masao <masao.fujii@gmail.com>
Discussion: https://postgr.es/m/CADzfLwXGvb4Y-mqy8T+O0f_tkXR1sTDBGzP5Z=V_qcGnZ46rWg@mail.gmail.com
Backpatch-through: 19
---

diff --git a/src/backend/postmaster/datachecksum_state.c b/src/backend/postmaster/datachecksum_state.c
index 569399fb2b1..be308a282d5 100644
--- a/src/backend/postmaster/datachecksum_state.c
+++ b/src/backend/postmaster/datachecksum_state.c
@@ -841,11 +841,10 @@ ProcessSingleRelationByOid(Oid relationId, BufferAccessStrategy strategy)
 		pgstat_report_activity(STATE_IDLE, NULL);
 		return true;
 	}
-	RelationGetSmgr(rel);
 
 	for (ForkNumber fnum = 0; fnum <= MAX_FORKNUM; fnum++)
 	{
-		if (smgrexists(rel->rd_smgr, fnum))
+		if (smgrexists(RelationGetSmgr(rel), fnum))
 		{
 			if (!ProcessSingleRelationFork(rel, fnum, strategy))
 			{