Allow I/O reliability checks using 16-bit checksums

Checksums are set immediately prior to flush out of shared buffers
and checked when pages are read in again. Hint bit setting will
require full page write when block is dirtied, which causes various
infrastructure changes. Extensive comments, docs and README.

WARNING message thrown if checksum fails on non-all zeroes page;
ERROR thrown but can be disabled with ignore_checksum_failure = on.

Feature enabled by an initdb option, since transition from option off
to option on is long and complex and has not yet been implemented.
Default is not to use checksums.

Checksum used is WAL CRC-32 truncated to 16-bits.

Simon Riggs, Jeff Davis, Greg Smith
Wide input and assistance from many community members. Thank you.

4 files changed, 12 insertions, 8 deletions

diff --git a/src/backend/commands/matview.c b/src/backend/commands/matview.c
index e20fedaeaf7..1d2b3478289 100644
--- a/src/backend/commands/matview.c
+++ b/src/backend/commands/matview.c
@@ -76,6 +76,8 @@ SetRelationIsScannable(Relation relation)
 		log_newpage(&(relation->rd_node), MAIN_FORKNUM, 0, page);
 
 	RelationOpenSmgr(relation);
+
+	PageSetChecksumInplace(page, 0);
 	smgrextend(relation->rd_smgr, MAIN_FORKNUM, 0, (char *) page, true);
 
 	pfree(page);
diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index a360be4daaf..c6add68b9f2 100644
--- a/src/backend/commands/sequence.c
+++ b/src/backend/commands/sequence.c
@@ -1118,7 +1118,7 @@ read_seq_tuple(SeqTable elm, Relation rel, Buffer *buf, HeapTuple seqtuple)
 		HeapTupleHeaderSetXmax(seqtuple->t_data, InvalidTransactionId);
 		seqtuple->t_data->t_infomask &= ~HEAP_XMAX_COMMITTED;
 		seqtuple->t_data->t_infomask |= HEAP_XMAX_INVALID;
-		SetBufferCommitInfoNeedsSave(*buf);
+		MarkBufferDirtyHint(*buf);
 	}
 
 	seq = (Form_pg_sequence) GETSTRUCT(seqtuple);
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 51bf13944b2..57cf0a07b51 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8902,6 +8902,8 @@ copy_relation_data(SMgrRelation src, SMgrRelation dst,
 
 		smgrread(src, forkNum, blkno, buf);
 
+		PageSetChecksumInplace(page, blkno);
+
 		/* XLOG stuff */
 		if (use_wal)
 			log_newpage(&dst->smgr_rnode.node, forkNum, blkno, page);
diff --git a/src/backend/commands/vacuumlazy.c b/src/backend/commands/vacuumlazy.c
index 4d3364aeff0..d39269897a5 100644
--- a/src/backend/commands/vacuumlazy.c
+++ b/src/backend/commands/vacuumlazy.c
@@ -672,8 +672,8 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
 			{
 				PageSetAllVisible(page);
 				MarkBufferDirty(buf);
-				visibilitymap_set(onerel, blkno, InvalidXLogRecPtr, vmbuffer,
-								  InvalidTransactionId);
+				visibilitymap_set(onerel, blkno, buf, InvalidXLogRecPtr,
+								  vmbuffer, InvalidTransactionId);
 			}
 
 			UnlockReleaseBuffer(buf);
@@ -907,8 +907,8 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
 			{
 				PageSetAllVisible(page);
 				MarkBufferDirty(buf);
-				visibilitymap_set(onerel, blkno, InvalidXLogRecPtr, vmbuffer,
-								  visibility_cutoff_xid);
+				visibilitymap_set(onerel, blkno, buf, InvalidXLogRecPtr,
+								  vmbuffer, visibility_cutoff_xid);
 			}
 			else if (!all_visible_according_to_vm)
 			{
@@ -918,8 +918,8 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
 				 * allowed.  Set the visibility map bit as well so that we get
 				 * back in sync.
 				 */
-				visibilitymap_set(onerel, blkno, InvalidXLogRecPtr, vmbuffer,
-								  visibility_cutoff_xid);
+				visibilitymap_set(onerel, blkno, buf, InvalidXLogRecPtr,
+								  vmbuffer, visibility_cutoff_xid);
 			}
 		}
 
@@ -1154,7 +1154,7 @@ lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer,
 	{
 		Assert(BufferIsValid(*vmbuffer));
 		PageSetAllVisible(page);
-		visibilitymap_set(onerel, blkno, InvalidXLogRecPtr, *vmbuffer,
+		visibilitymap_set(onerel, blkno, buffer, InvalidXLogRecPtr, *vmbuffer,
 				visibility_cutoff_xid);
 	}