Avoid allocations in critical sections.

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

diff --git a/src/backend/access/nbtree/nbtinsert.c b/src/backend/access/nbtree/nbtinsert.c
index f866143e59bb7a741131cbbfa5bd853879f1ee0b..e8cdadfebd5c379075a197d19fbf4d2999388952 100644 (file)
--- a/src/backend/access/nbtree/nbtinsert.c
+++ b/src/backend/access/nbtree/nbtinsert.c
@@ -1726,8 +1726,10 @@ _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;
@@ -1746,6 +1748,26 @@ _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();
 
@@ -1763,16 +1785,6 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
        metad->btm_fastroot = rootblknum;
        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
@@ -1781,32 +1793,20 @@ _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);
@@ -1854,6 +1854,9 @@ _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 b8ca6857afb88a3fa6bd7c6b6c1e528907b5786c..35904f4b2c20ca8f5f1f5d77921f8cfbb7c57dcf 100644 (file)
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -2167,6 +2167,7 @@ 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;
@@ -2224,11 +2225,11 @@ 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;
@@ -2248,7 +2249,6 @@ XLogFileInit(uint32 log, uint32 seg,
                                         errmsg("could not write to file \"%s\": %m", tmppath)));
                }
        }
-       pfree(zbuffer);
 
        if (pg_fsync(fd) != 0)
                ereport(ERROR,

diff --git a/src/backend/storage/page/bufpage.c b/src/backend/storage/page/bufpage.c
index b59602ec1289d93825608d19ed6085e718e97767..70784cf35a74575b396dff72c0e71c65a3fdfb39 100644 (file)
--- a/src/backend/storage/page/bufpage.c
+++ b/src/backend/storage/page/bufpage.c
@@ -15,6 +15,7 @@
 #include "postgres.h"
 
 #include "access/htup.h"
+#include "access/itup.h"
 #include "storage/bufpage.h"
 
 
@@ -363,8 +364,6 @@ PageRepairFragmentation(Page page)
        Offset          pd_lower = ((PageHeader) page)->pd_lower;
        Offset          pd_upper = ((PageHeader) page)->pd_upper;
        Offset          pd_special = ((PageHeader) page)->pd_special;
-       itemIdSort      itemidbase,
-                               itemidptr;
        ItemId          lp;
        int                     nline,
                                nstorage,
@@ -414,10 +413,11 @@ PageRepairFragmentation(Page page)
                ((PageHeader) page)->pd_upper = pd_special;
        }
        else
-       {                                                       /* nstorage != 0 */
+       {
                /* Need to compact the page the hard way */
-               itemidbase = (itemIdSort) palloc(sizeof(itemIdSortData) * nstorage);
-               itemidptr = itemidbase;
+               itemIdSortData itemidbase[MaxHeapTuplesPerPage];
+               itemIdSort      itemidptr = itemidbase;
+
                totallen = 0;
                for (i = 0; i < nline; i++)
                {
@@ -462,8 +462,6 @@ PageRepairFragmentation(Page page)
                }
 
                ((PageHeader) page)->pd_upper = upper;
-
-               pfree(itemidbase);
        }
 
        /* Set hint bit for PageAddItem */
@@ -712,8 +710,8 @@ PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems)
        Offset          pd_lower = phdr->pd_lower;
        Offset          pd_upper = phdr->pd_upper;
        Offset          pd_special = phdr->pd_special;
-       itemIdSort      itemidbase,
-                               itemidptr;
+       itemIdSortData  itemidbase[MaxIndexTuplesPerPage];
+       itemIdSort      itemidptr;
        ItemId          lp;
        int                     nline,
                                nused;
@@ -725,6 +723,8 @@ PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems)
        int                     nextitm;
        OffsetNumber offnum;
 
+       Assert(nitems < MaxIndexTuplesPerPage);
+
        /*
         * If there aren't very many items to delete, then retail
         * PageIndexTupleDelete is the best way.  Delete the items in reverse
@@ -759,7 +759,6 @@ PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems)
         * still validity-checking.
         */
        nline = PageGetMaxOffsetNumber(page);
-       itemidbase = (itemIdSort) palloc(sizeof(itemIdSortData) * nline);
        itemidptr = itemidbase;
        totallen = 0;
        nused = 0;
@@ -825,6 +824,4 @@ PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems)
 
        phdr->pd_lower = SizeOfPageHeaderData + nused * sizeof(ItemIdData);
        phdr->pd_upper = upper;
-
-       pfree(itemidbase);
 }