From 04e298b826d452ceb838d9fda884a29f229d484d Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Thu, 3 Apr 2014 15:09:37 +0300 Subject: Avoid palloc in critical section in GiST WAL-logging. Memory allocation can fail if you run out of memory, and inside a critical section that will lead to a PANIC. Use conservatively-sized arrays in stack instead. There was previously no explicit limit on the number of pages a GiST split can produce, it was only limited by the number of LWLocks that can be held simultaneously (100 at the moment). This patch adds an explicit limit of 75 pages. That should be plenty, a typical split shouldn't produce more than 2-3 page halves. The bug has been there forever, but only backpatch down to 9.1. The code was changed significantly in 9.1, and it doesn't seem worth the risk or trouble to adapt this for 9.0 and 8.4. --- src/backend/access/gist/gistxlog.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) (limited to 'src/backend/access/gist/gistxlog.c') diff --git a/src/backend/access/gist/gistxlog.c b/src/backend/access/gist/gistxlog.c index d6fdc04cf28..7cc64aeb490 100644 --- a/src/backend/access/gist/gistxlog.c +++ b/src/backend/access/gist/gistxlog.c @@ -379,7 +379,7 @@ gistXLogSplit(RelFileNode node, BlockNumber blkno, bool page_is_leaf, BlockNumber origrlink, GistNSN orignsn, Buffer leftchildbuf, bool markfollowright) { - XLogRecData *rdata; + XLogRecData rdata[GIST_MAX_SPLIT_PAGES * 2 + 2]; gistxlogPageSplit xlrec; SplitedPageLayout *ptr; int npage = 0, @@ -388,8 +388,12 @@ gistXLogSplit(RelFileNode node, BlockNumber blkno, bool page_is_leaf, for (ptr = dist; ptr; ptr = ptr->next) npage++; - - rdata = (XLogRecData *) palloc(sizeof(XLogRecData) * (npage * 2 + 2)); + /* + * the caller should've checked this already, but doesn't hurt to check + * again. + */ + if (npage > GIST_MAX_SPLIT_PAGES) + elog(ERROR, "GiST page split into too many halves"); xlrec.node = node; xlrec.origblkno = blkno; @@ -439,7 +443,6 @@ gistXLogSplit(RelFileNode node, BlockNumber blkno, bool page_is_leaf, recptr = XLogInsert(RM_GIST_ID, XLOG_GIST_PAGE_SPLIT, rdata); - pfree(rdata); return recptr; } @@ -462,14 +465,12 @@ gistXLogUpdate(RelFileNode node, Buffer buffer, IndexTuple *itup, int ituplen, Buffer leftchildbuf) { - XLogRecData *rdata; + XLogRecData rdata[MaxIndexTuplesPerPage + 3]; gistxlogPageUpdate xlrec; int cur, i; XLogRecPtr recptr; - rdata = (XLogRecData *) palloc(sizeof(XLogRecData) * (3 + ituplen)); - xlrec.node = node; xlrec.blkno = BufferGetBlockNumber(buffer); xlrec.ntodelete = ntodelete; @@ -516,6 +517,5 @@ gistXLogUpdate(RelFileNode node, Buffer buffer, recptr = XLogInsert(RM_GIST_ID, XLOG_GIST_PAGE_UPDATE, rdata); - pfree(rdata); return recptr; } -- cgit v1.2.3