From c780a7a90a8e7b074405ea2007e34f94e227e695 Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Wed, 28 Oct 2020 11:12:46 +0900 Subject: Add CheckBuffer() to check on-disk pages without shared buffer loading CheckBuffer() is designed to be a concurrent-safe function able to run sanity checks on a relation page without loading it into the shared buffers. The operation is done using a lock on the partition involved in the shared buffer mapping hashtable and an I/O lock for the buffer itself, preventing the risk of false positives due to any concurrent activity. The primary use of this function is the detection of on-disk corruptions for relation pages. If a page is found in shared buffers, the on-disk page is checked if not dirty (a follow-up checkpoint would flush a valid version of the page if dirty anyway), as it could be possible that a page was present for a long time in shared buffers with its on-disk version corrupted. Such a scenario could lead to a corrupted cluster if a host is plugged off for example. If the page is not found in shared buffers, its on-disk state is checked. PageIsVerifiedExtended() is used to apply the same sanity checks as when a page gets loaded into shared buffers. This function will be used by an upcoming patch able to check the state of on-disk relation pages using a SQL function. Author: Julien Rouhaud, Michael Paquier Reviewed-by: Masahiko Sawada Discussion: https://postgr.es/m/CAOBaU_aVvMjQn=ge5qPiJOPMmOj5=ii3st5Q0Y+WuLML5sR17w@mail.gmail.com --- src/include/storage/bufmgr.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'src/include') diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index ee91b8fa26c..a21cab2eaf8 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -240,6 +240,9 @@ extern void AtProcExit_LocalBuffers(void); extern void TestForOldSnapshot_impl(Snapshot snapshot, Relation relation); +extern bool CheckBuffer(struct SMgrRelationData *smgr, ForkNumber forknum, + BlockNumber blkno); + /* in freelist.c */ extern BufferAccessStrategy GetAccessStrategy(BufferAccessStrategyType btype); extern void FreeAccessStrategy(BufferAccessStrategy strategy); -- cgit v1.2.3