From 8fe728b0094e8364e82b4a58c92265c00f4a2d1b Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 4 Apr 2003 00:32:57 +0000 Subject: [PATCH] Back-patch changes to validate page header fields immediately after reading in any page. Also back-port the zero_damaged_pages boolean that determines what to do about it. --- doc/src/sgml/runtime.sgml | 28 ++++++++++++++--- src/backend/storage/buffer/bufmgr.c | 21 ++++++++++++- src/backend/storage/page/bufpage.c | 49 +++++++++++++++++++++++++++-- src/backend/utils/misc/guc.c | 6 +++- src/include/storage/bufmgr.h | 5 ++- src/include/storage/bufpage.h | 3 +- 6 files changed, 101 insertions(+), 11 deletions(-) diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml index 10507b81ff0..f77ee8e035a 100644 --- a/doc/src/sgml/runtime.sgml +++ b/doc/src/sgml/runtime.sgml @@ -1,5 +1,5 @@ @@ -1525,10 +1525,10 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir' - It should be noted that the performance penalty of doing - fsyncs is considerably less in + It should be noted that the performance penalty of having + fsync on is considerably less in PostgreSQL version 7.1 and later. If you - previously suppressed fsyncs for performance + previously suppressed fsync for performance reasons, you may wish to reconsider your choice. @@ -2057,6 +2057,26 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir' + + ZERO_DAMAGED_PAGES (boolean) + + + Detection of a damaged page header normally causes + PostgreSQL to report an error, aborting the current + transaction. Setting zero_damaged_pages to true causes + the system to instead report a warning, zero out the damaged page, + and continue processing. This behavior will destroy data, + namely all the rows on the damaged page. But it allows you to get + past the error and retrieve rows from any undamaged pages that may + be present in the table. So it is useful for recovering data if + corruption has occurred due to hardware or software error. You should + generally not set this true until you have given up hope of recovering + data from the damaged page(s) of a table. The + default setting is off, and it can only be changed by a superuser. + + + + diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c index 6d1e52d5220..35b1db79e84 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.133 2002/09/14 19:59:20 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.133.2.1 2003/04/04 00:32:57 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -49,6 +49,7 @@ #include "miscadmin.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/bufpage.h" #include "storage/proc.h" #include "storage/smgr.h" #include "utils/relcache.h" @@ -59,6 +60,10 @@ (*((XLogRecPtr*) MAKE_PTR((bufHdr)->data))) +/* GUC variable */ +bool zero_damaged_pages = false; + + static void WaitIO(BufferDesc *buf); static void StartBufferIO(BufferDesc *buf, bool forInput); static void TerminateBufferIO(BufferDesc *buf); @@ -217,6 +222,20 @@ ReadBufferInternal(Relation reln, BlockNumber blockNum, { status = smgrread(DEFAULT_SMGR, reln, blockNum, (char *) MAKE_PTR(bufHdr->data)); + /* check for garbage data */ + if (status == SM_SUCCESS && + !PageHeaderIsValid((PageHeader) MAKE_PTR(bufHdr->data))) + { + if (zero_damaged_pages) + { + elog(WARNING, "Invalid page header in block %u of %s; zeroing out page", + blockNum, RelationGetRelationName(reln)); + MemSet((char *) MAKE_PTR(bufHdr->data), 0, BLCKSZ); + } + else + elog(ERROR, "Invalid page header in block %u of %s", + blockNum, RelationGetRelationName(reln)); + } } if (isLocalBuf) diff --git a/src/backend/storage/page/bufpage.c b/src/backend/storage/page/bufpage.c index 83e0c337228..c57ebf2fbdc 100644 --- a/src/backend/storage/page/bufpage.c +++ b/src/backend/storage/page/bufpage.c @@ -8,14 +8,12 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/storage/page/bufpage.c,v 1.50 2002/09/04 20:31:26 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/storage/page/bufpage.c,v 1.50.2.1 2003/04/04 00:32:57 tgl Exp $ * *------------------------------------------------------------------------- */ #include "postgres.h" -#include - #include "storage/bufpage.h" @@ -48,6 +46,51 @@ PageInit(Page page, Size pageSize, Size specialSize) } +/* + * PageHeaderIsValid + * Check that the header fields of a page appear valid. + * + * This is called when a page has just been read in from disk. The idea is + * to cheaply detect trashed pages before we go nuts following bogus item + * pointers, testing invalid transaction identifiers, etc. + * + * It turns out to be necessary to allow zeroed pages here too. Even though + * this routine is *not* called when deliberately adding a page to a relation, + * there are scenarios in which a zeroed page might be found in a table. + * (Example: a backend extends a relation, then crashes before it can write + * any WAL entry about the new page. The kernel will already have the + * zeroed page in the file, and it will stay that way after restart.) So we + * 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. + */ +bool +PageHeaderIsValid(PageHeader page) +{ + char *pagebytes; + int i; + + /* Check normal case */ + if (PageGetPageSize(page) == BLCKSZ && + PageGetPageLayoutVersion(page) == PG_PAGE_LAYOUT_VERSION && + page->pd_lower >= SizeOfPageHeaderData && + page->pd_lower <= page->pd_upper && + page->pd_upper <= page->pd_special && + page->pd_special <= BLCKSZ && + page->pd_special == MAXALIGN(page->pd_special)) + return true; + + /* Check all-zeroes case */ + pagebytes = (char *) page; + for (i = 0; i < BLCKSZ; i++) + { + if (pagebytes[i] != 0) + return false; + } + return true; +} + + /* ---------------- * PageAddItem * diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index edb5e353644..b49b36565e6 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -5,7 +5,7 @@ * command, configuration file, and command line options. * See src/backend/utils/misc/README for more information. * - * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.99.2.4 2003/01/28 18:04:13 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.99.2.5 2003/04/04 00:32:57 tgl Exp $ * * Copyright 2000 by PostgreSQL Global Development Group * Written by Peter Eisentraut . @@ -352,6 +352,10 @@ static struct config_bool {"fsync", PGC_SIGHUP}, &enableFsync, true, NULL, NULL }, + { + {"zero_damaged_pages", PGC_SUSET}, &zero_damaged_pages, + false, NULL, NULL + }, { {"silent_mode", PGC_POSTMASTER}, &SilentMode, false, NULL, NULL diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 5fcc354849d..c2f970c0b6c 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $Id: bufmgr.h,v 1.66 2002/10/22 20:00:48 petere Exp $ + * $Id: bufmgr.h,v 1.66.2.1 2003/04/04 00:32:57 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -25,6 +25,9 @@ typedef void *Block; /* in globals.c ... this duplicates miscadmin.h */ extern DLLIMPORT int NBuffers; +/* in bufmgr.c */ +extern bool zero_damaged_pages; + /* in buf_init.c */ extern DLLIMPORT Block *BufferBlockPointers; extern long *PrivateRefCount; diff --git a/src/include/storage/bufpage.h b/src/include/storage/bufpage.h index 159a82a0228..fc589c18f9d 100644 --- a/src/include/storage/bufpage.h +++ b/src/include/storage/bufpage.h @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $Id: bufpage.h,v 1.53 2002/09/04 20:31:45 momjian Exp $ + * $Id: bufpage.h,v 1.53.2.1 2003/04/04 00:32:57 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -339,6 +339,7 @@ typedef PageHeaderData *PageHeader; */ extern void PageInit(Page page, Size pageSize, Size specialSize); +extern bool PageHeaderIsValid(PageHeader page); extern OffsetNumber PageAddItem(Page page, Item item, Size size, OffsetNumber offsetNumber, ItemIdFlags flags); extern Page PageGetTempPage(Page page, Size specialSize); -- 2.39.5