From 31633f992568ffca9a7927a9f474ad8516840b2c Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Thu, 8 May 2014 14:43:04 +0300 Subject: [PATCH] Protect against torn pages when deleting GIN list pages. To-be-deleted list pages contain no useful information, as they are being deleted, but we must still protect the writes from being torn by a crash after a partial write. To do that, re-initialize the pages on WAL replay. Jeff Janes caught this with a test program to test partial writes. Backpatch to all supported versions. --- src/backend/access/gin/ginxlog.c | 28 ++++++++++++++-------------- 1 file changed, 14 insertions(+), 14 deletions(-) diff --git a/src/backend/access/gin/ginxlog.c b/src/backend/access/gin/ginxlog.c index 386bcb3af6..6603649615 100644 --- a/src/backend/access/gin/ginxlog.c +++ b/src/backend/access/gin/ginxlog.c @@ -698,26 +698,26 @@ ginRedoDeleteListPages(XLogRecPtr lsn, XLogRecord *record) * cannot get past a reader that is on, or due to visit, any page we are * going to delete. New incoming readers will block behind our metapage * lock and then see a fully updated page list. + * + * No full-page images are taken of the deleted pages. Instead, they are + * re-initialized as empty, deleted pages. Their right-links don't need to + * be preserved, because no new readers can see the pages, as explained + * above. */ for (i = 0; i < data->ndeleted; i++) { - Buffer buffer = XLogReadBuffer(data->node, data->toDelete[i], false); + Buffer buffer; + Page page; - if (BufferIsValid(buffer)) - { - Page page = BufferGetPage(buffer); - - if (!XLByteLE(lsn, PageGetLSN(page))) - { - GinPageGetOpaque(page)->flags = GIN_DELETED; + buffer = XLogReadBuffer(data->node, data->toDelete[i], true); + page = BufferGetPage(buffer); + GinInitBuffer(buffer, GIN_DELETED); - PageSetLSN(page, lsn); - PageSetTLI(page, ThisTimeLineID); - MarkBufferDirty(buffer); - } + PageSetLSN(page, lsn); + PageSetTLI(page, ThisTimeLineID); + MarkBufferDirty(buffer); - UnlockReleaseBuffer(buffer); - } + UnlockReleaseBuffer(buffer); } UnlockReleaseBuffer(metabuffer); } -- 2.40.0