From 31633f992568ffca9a7927a9f474ad8516840b2c Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
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 386bcb3af6f..66036496153 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);
}
--
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