Extend PageIsVerified() to handle more custom options

This is useful for checks of relation pages without having to load the
pages into the shared buffers, and two cases can make use of that: page
verification in base backups and the online, lock-safe, flavor.

Compatibility is kept with past versions using a routine that calls the
new extended routine with the set of options compatible with the
original version.  Contrary to d401c576, a macro cannot be used as there
may be external code relying on the presence of the original routine.

This is applied down to 11, where this will be used by a follow-up
commit addressing a set of issues with page verification in base
backups.

Extracted from a larger patch by the same author.

Author: Anastasia Lubennikova
Reviewed-by: Michael Paquier, Julien Rouhaud
Discussion: https://postgr.es/m/608f3476-0598-2514-2c03-e05c7d2b0cbd@postgrespro.ru
Backpatch-through: 11

Author: michaelpq

src/backend/catalog/storage.c

@@ -443,7 +443,8 @@ RelationCopyStorage(SMgrRelation src, SMgrRelation dst,
 
 		smgrread(src, forkNum, blkno, buf.data);
 
-		if (!PageIsVerified(page, blkno))
+		if (!PageIsVerifiedExtended(page, blkno,
+									PIV_LOG_WARNING | PIV_REPORT_STAT))
 			ereport(ERROR,
 					(errcode(ERRCODE_DATA_CORRUPTED),
 					 errmsg("invalid page in block %u of relation %s",

src/backend/storage/buffer/bufmgr.c

@@ -624,7 +624,8 @@ ReadBuffer(Relation reln, BlockNumber blockNum)
  *
  * In RBM_NORMAL mode, the page is read from disk, and the page header is
  * validated.  An error is thrown if the page header is not valid.  (But
- * note that an all-zero page is considered "valid"; see PageIsVerified().)
+ * note that an all-zero page is considered "valid"; see
+ * PageIsVerifiedExtended().)
  *
  * RBM_ZERO_ON_ERROR is like the normal mode, but if the page header is not
  * valid, the page is zeroed instead of throwing an error. This is intended
@@ -916,7 +917,8 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
 			}
 
 			/* check for garbage data */
-			if (!PageIsVerified((Page) bufBlock, blockNum))
+			if (!PageIsVerifiedExtended((Page) bufBlock, blockNum,
+										PIV_LOG_WARNING | PIV_REPORT_STAT))
 			{
 				if (mode == RBM_ZERO_ON_ERROR || zero_damaged_pages)
 				{

src/backend/storage/page/bufpage.c

@@ -62,6 +62,18 @@ PageInit(Page page, Size pageSize, Size specialSize)
 
 /*
  * PageIsVerified
+ *		Utility wrapper for PageIsVerifiedExtended().
+ */
+bool
+PageIsVerified(Page page, BlockNumber blkno)
+{
+	return PageIsVerifiedExtended(page, blkno,
+								  PIV_LOG_WARNING | PIV_REPORT_STAT);
+}
+
+
+/*
+ * PageIsVerifiedExtended
  *		Check that the page header and checksum (if any) appear valid.
  *
  * This is called when a page has just been read in from disk.  The idea is
@@ -77,9 +89,15 @@ PageInit(Page page, Size pageSize, Size specialSize)
  * allow zeroed pages here, and are careful that the page access macros
  * treat such a page as empty and without free space.  Eventually, VACUUM
  * will clean up such a page and make it usable.
+ *
+ * If flag PIV_LOG_WARNING is set, a WARNING is logged in the event of
+ * a checksum failure.
+ *
+ * If flag PIV_REPORT_STAT is set, a checksum failure is reported directly
+ * to pgstat.
  */
 bool
-PageIsVerified(Page page, BlockNumber blkno)
+PageIsVerifiedExtended(Page page, BlockNumber blkno, int flags)
 {
 	PageHeader	p = (PageHeader) page;
 	size_t	   *pagebytes;
@@ -140,12 +158,14 @@ PageIsVerified(Page page, BlockNumber blkno)
 	 */
 	if (checksum_failure)
 	{
-		ereport(WARNING,
-				(errcode(ERRCODE_DATA_CORRUPTED),
-				 errmsg("page verification failed, calculated checksum %u but expected %u",
-						checksum, p->pd_checksum)));
+		if ((flags & PIV_LOG_WARNING) != 0)
+			ereport(WARNING,
+					(errcode(ERRCODE_DATA_CORRUPTED),
+					 errmsg("page verification failed, calculated checksum %u but expected %u",
+							checksum, p->pd_checksum)));
 
-		pgstat_report_checksum_failure();
+		if ((flags & PIV_REPORT_STAT) != 0)
+			pgstat_report_checksum_failure();
 
 		if (header_sane && ignore_checksum_failure)
 			return true;

src/include/storage/bufpage.h

@@ -410,26 +410,33 @@ do { \
  *		extern declarations
  * ----------------------------------------------------------------
  */
+
+/* flags for PageAddItemExtended() */
 #define PAI_OVERWRITE			(1 << 0)
 #define PAI_IS_HEAP				(1 << 1)
 
+/* flags for PageIsVerifiedExtended() */
+#define PIV_LOG_WARNING			(1 << 0)
+#define PIV_REPORT_STAT			(1 << 1)
+
 #define PageAddItem(page, item, size, offsetNumber, overwrite, is_heap) \
 	PageAddItemExtended(page, item, size, offsetNumber, \
 						((overwrite) ? PAI_OVERWRITE : 0) | \
 						((is_heap) ? PAI_IS_HEAP : 0))
 
 /*
- * Check that BLCKSZ is a multiple of sizeof(size_t).  In PageIsVerified(),
- * it is much faster to check if a page is full of zeroes using the native
- * word size.  Note that this assertion is kept within a header to make
- * sure that StaticAssertDecl() works across various combinations of
- * platforms and compilers.
+ * Check that BLCKSZ is a multiple of sizeof(size_t).  In
+ * PageIsVerifiedExtended(), it is much faster to check if a page is
+ * full of zeroes using the native word size.  Note that this assertion
+ * is kept within a header to make sure that StaticAssertDecl() works
+ * across various combinations of platforms and compilers.
  */
 StaticAssertDecl(BLCKSZ == ((BLCKSZ / sizeof(size_t)) * sizeof(size_t)),
 				 "BLCKSZ has to be a multiple of sizeof(size_t)");
 
 extern void PageInit(Page page, Size pageSize, Size specialSize);
 extern bool PageIsVerified(Page page, BlockNumber blkno);
+extern bool PageIsVerifiedExtended(Page page, BlockNumber blkno, int flags);
 extern OffsetNumber PageAddItemExtended(Page page, Item item, Size size,
 										OffsetNumber offsetNumber, int flags);
 extern Page PageGetTempPage(Page page);