Avoid allocations in critical sections.

If a palloc in a critical section fails, it becomes a PANIC.

2 files changed, 34 insertions, 31 deletions

diff --git a/src/backend/access/nbtree/nbtinsert.c b/src/backend/access/nbtree/nbtinsert.c
index d758659c314..735291f342e 100644
--- a/src/backend/access/nbtree/nbtinsert.c
+++ b/src/backend/access/nbtree/nbtinsert.c
@@ -1840,8 +1840,10 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
 	BTPageOpaque rootopaque;
 	ItemId		itemid;
 	IndexTuple	item;
-	Size		itemsz;
-	IndexTuple	new_item;
+	IndexTuple	left_item;
+	Size		left_item_sz;
+	IndexTuple	right_item;
+	Size		right_item_sz;
 	Buffer		metabuf;
 	Page		metapg;
 	BTMetaPageData *metad;
@@ -1860,6 +1862,26 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
 	metapg = BufferGetPage(metabuf);
 	metad = BTPageGetMeta(metapg);
 
+	/*
+	 * Create downlink item for left page (old root).  Since this will be the
+	 * first item in a non-leaf page, it implicitly has minus-infinity key
+	 * value, so we need not store any actual key in it.
+	 */
+	left_item_sz = sizeof(IndexTupleData);
+	left_item = (IndexTuple) palloc(left_item_sz);
+	left_item->t_info = left_item_sz;
+	ItemPointerSet(&(left_item->t_tid), lbkno, P_HIKEY);
+
+	/*
+	 * Create downlink item for right page.  The key for it is obtained from
+	 * the "high key" position in the left page.
+	 */
+	itemid = PageGetItemId(lpage, P_HIKEY);
+	right_item_sz = ItemIdGetLength(itemid);
+	item = (IndexTuple) PageGetItem(lpage, itemid);
+	right_item = CopyIndexTuple(item);
+	ItemPointerSet(&(right_item->t_tid), rbkno, P_HIKEY);
+
 	/* NO EREPORT(ERROR) from here till newroot op is logged */
 	START_CRIT_SECTION();
 
@@ -1878,16 +1900,6 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
 	metad->btm_fastlevel = rootopaque->btpo.level;
 
 	/*
-	 * Create downlink item for left page (old root).  Since this will be the
-	 * first item in a non-leaf page, it implicitly has minus-infinity key
-	 * value, so we need not store any actual key in it.
-	 */
-	itemsz = sizeof(IndexTupleData);
-	new_item = (IndexTuple) palloc(itemsz);
-	new_item->t_info = itemsz;
-	ItemPointerSet(&(new_item->t_tid), lbkno, P_HIKEY);
-
-	/*
 	 * Insert the left page pointer into the new root page.  The root page is
 	 * the rightmost page on its level so there is no "high key" in it; the
 	 * two items will go into positions P_HIKEY and P_FIRSTKEY.
@@ -1895,32 +1907,20 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
 	 * Note: we *must* insert the two items in item-number order, for the
 	 * benefit of _bt_restore_page().
 	 */
-	if (PageAddItem(rootpage, (Item) new_item, itemsz, P_HIKEY,
+	if (PageAddItem(rootpage, (Item) left_item, left_item_sz, P_HIKEY,
 					false, false) == InvalidOffsetNumber)
 		elog(PANIC, "failed to add leftkey to new root page"
 			 " while splitting block %u of index \"%s\"",
 			 BufferGetBlockNumber(lbuf), RelationGetRelationName(rel));
-	pfree(new_item);
-
-	/*
-	 * Create downlink item for right page.  The key for it is obtained from
-	 * the "high key" position in the left page.
-	 */
-	itemid = PageGetItemId(lpage, P_HIKEY);
-	itemsz = ItemIdGetLength(itemid);
-	item = (IndexTuple) PageGetItem(lpage, itemid);
-	new_item = CopyIndexTuple(item);
-	ItemPointerSet(&(new_item->t_tid), rbkno, P_HIKEY);
 
 	/*
 	 * insert the right page pointer into the new root page.
 	 */
-	if (PageAddItem(rootpage, (Item) new_item, itemsz, P_FIRSTKEY,
+	if (PageAddItem(rootpage, (Item) right_item, right_item_sz, P_FIRSTKEY,
 					false, false) == InvalidOffsetNumber)
 		elog(PANIC, "failed to add rightkey to new root page"
 			 " while splitting block %u of index \"%s\"",
 			 BufferGetBlockNumber(lbuf), RelationGetRelationName(rel));
-	pfree(new_item);
 
 	MarkBufferDirty(rootbuf);
 	MarkBufferDirty(metabuf);
@@ -1968,6 +1968,9 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
 	/* done with metapage */
 	_bt_relbuf(rel, metabuf);
 
+	pfree(left_item);
+	pfree(right_item);
+
 	return rootbuf;
 }
 
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 42ec2fe71de..6b9209d882a 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -2348,6 +2348,7 @@ XLogFileInit(uint32 log, uint32 seg,
 {
 	char		path[MAXPGPATH];
 	char		tmppath[MAXPGPATH];
+	char		zbuffer_raw[BLCKSZ + MAXIMUM_ALIGNOF];
 	char	   *zbuffer;
 	uint32		installed_log;
 	uint32		installed_seg;
@@ -2405,11 +2406,11 @@ XLogFileInit(uint32 log, uint32 seg,
 	 * fdatasync(2) or O_DSYNC will be sufficient to sync future writes to the
 	 * log file.
 	 *
-	 * Note: palloc zbuffer, instead of just using a local char array, to
-	 * ensure it is reasonably well-aligned; this may save a few cycles
-	 * transferring data to the kernel.
+	 * Note: ensure the buffer is reasonably well-aligned; this may save a few
+	 * cycles transferring data to the kernel.
 	 */
-	zbuffer = (char *) palloc0(XLOG_BLCKSZ);
+	zbuffer = (char *) MAXALIGN(zbuffer_raw);
+	memset(zbuffer, 0, BLCKSZ);
 	for (nbytes = 0; nbytes < XLogSegSize; nbytes += XLOG_BLCKSZ)
 	{
 		errno = 0;
@@ -2429,7 +2430,6 @@ XLogFileInit(uint32 log, uint32 seg,
 					 errmsg("could not write to file \"%s\": %m", tmppath)));
 		}
 	}
-	pfree(zbuffer);
 
 	if (pg_fsync(fd) != 0)
 		ereport(ERROR,