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Replace RelationOpenSmgr() with RelationGetSmgr().

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The idea behind this patch is to design out bugs like the one fixed
by commit 9d523119f.  Previously, once one did RelationOpenSmgr(rel),
it was considered okay to access rel->rd_smgr directly for some
not-very-clear interval.  But since that pointer will be cleared by
relcache flushes, we had bugs arising from overreliance on a previous
RelationOpenSmgr call still being effective.

Now, very little code except that in rel.h and relcache.c should ever
touch the rd_smgr field directly.  The normal coding rule is to use
RelationGetSmgr(rel) and not expect the result to be valid for longer
than one smgr function call.  There are a couple of places where using
the function every single time seemed like overkill, but they are now
annotated with large warning comments.

Amul Sul, after an idea of mine.

Discussion: https://postgr.es/m/CANiYTQsU7yMFpQYnv=BrcRVqK_3U3mtAzAsJCaqtzsDHfsUbdQ@mail.gmail.com
This commit is contained in:
Tom Lane
2021-07-12 17:01:29 -04:00
parent 5b60cf35f5
commit f10f0ae420
21 changed files with 164 additions and 165 deletions
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6
src/backend/access/nbtree/nbtree.c
View File

@@ -163,9 +163,9 @@ btbuildempty(Relation index)
* this even when wal_level=minimal.
*/
PageSetChecksumInplace(metapage, BTREE_METAPAGE);
smgrwrite(index->rd_smgr, INIT_FORKNUM, BTREE_METAPAGE,
smgrwrite(RelationGetSmgr(index), INIT_FORKNUM, BTREE_METAPAGE,
(char *) metapage, true);
log_newpage(&index->rd_smgr->smgr_rnode.node, INIT_FORKNUM,
log_newpage(&RelationGetSmgr(index)->smgr_rnode.node, INIT_FORKNUM,
BTREE_METAPAGE, metapage, true);
/*
@@ -173,7 +173,7 @@ btbuildempty(Relation index)
* write did not go through shared_buffers and therefore a concurrent
* checkpoint may have moved the redo pointer past our xlog record.
*/
smgrimmedsync(index->rd_smgr, INIT_FORKNUM);
smgrimmedsync(RelationGetSmgr(index), INIT_FORKNUM);
}
/*

14
src/backend/access/nbtree/nbtsort.c
View File

@@ -637,9 +637,6 @@ _bt_blnewpage(uint32 level)
static void
_bt_blwritepage(BTWriteState *wstate, Page page, BlockNumber blkno)
{
/* Ensure rd_smgr is open (could have been closed by relcache flush!) */
RelationOpenSmgr(wstate->index);
/* XLOG stuff */
if (wstate->btws_use_wal)
{
@@ -659,7 +656,7 @@ _bt_blwritepage(BTWriteState *wstate, Page page, BlockNumber blkno)
if (!wstate->btws_zeropage)
wstate->btws_zeropage = (Page) palloc0(BLCKSZ);
/* don't set checksum for all-zero page */
smgrextend(wstate->index->rd_smgr, MAIN_FORKNUM,
smgrextend(RelationGetSmgr(wstate->index), MAIN_FORKNUM,
wstate->btws_pages_written++,
(char *) wstate->btws_zeropage,
true);
@@ -674,14 +671,14 @@ _bt_blwritepage(BTWriteState *wstate, Page page, BlockNumber blkno)
if (blkno == wstate->btws_pages_written)
{
/* extending the file... */
smgrextend(wstate->index->rd_smgr, MAIN_FORKNUM, blkno,
smgrextend(RelationGetSmgr(wstate->index), MAIN_FORKNUM, blkno,
(char *) page, true);
wstate->btws_pages_written++;
}
else
{
/* overwriting a block we zero-filled before */
smgrwrite(wstate->index->rd_smgr, MAIN_FORKNUM, blkno,
smgrwrite(RelationGetSmgr(wstate->index), MAIN_FORKNUM, blkno,
(char *) page, true);
}
@@ -1428,10 +1425,7 @@ _bt_load(BTWriteState *wstate, BTSpool *btspool, BTSpool *btspool2)
* still not be on disk when the crash occurs.
*/
if (wstate->btws_use_wal)
{
RelationOpenSmgr(wstate->index);
smgrimmedsync(wstate->index->rd_smgr, MAIN_FORKNUM);
}
smgrimmedsync(RelationGetSmgr(wstate->index), MAIN_FORKNUM);
}
/*