From 98758f3774484f54f010d4bec663ac60b764170f Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Wed, 13 Jan 2021 12:21:28 +0200 Subject: [PATCH v10 1/3] Move a few ResourceOwnerEnlarge() calls for safety and clarity. These are functions where quite a lot of things happen between the ResourceOwnerEnlarge and ResourceOwnerRemember calls. It's important that there are no unrelated ResourceOwnerRemember() calls in the code inbetween, otherwise the entry reserved by the ResourceOwnerEnlarge() call might be used up by the intervening ResourceOwnerRemember() and not be available at the intended ResourceOwnerRemember() call anymore. The longer the code path between them is, the harder it is to verify that. In bufmgr.c, there is a function similar to ResourceOwnerEnlarge(), to ensure that the private refcount array has enough space. The ReservePrivateRefCountEntry() calls, analogous to ResourceOwnerEnlarge(), were made at different places than the ResourceOwnerEnlarge() calls. Move the ResourceOwnerEnlarge() calls together with the ReservePrivateRefCountEntry() calls for consistency. --- src/backend/storage/buffer/bufmgr.c | 39 +++++++++++---------------- src/backend/storage/buffer/localbuf.c | 3 +++ src/backend/utils/cache/catcache.c | 13 ++++++--- 3 files changed, 28 insertions(+), 27 deletions(-) diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c index e88e4e918b0..cde9184c7d6 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -810,9 +810,6 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum, *hit = false; - /* Make sure we will have room to remember the buffer pin */ - ResourceOwnerEnlargeBuffers(CurrentResourceOwner); - isExtend = (blockNum == P_NEW); TRACE_POSTGRESQL_BUFFER_READ_START(forkNum, blockNum, @@ -1174,9 +1171,11 @@ BufferAlloc(SMgrRelation smgr, char relpersistence, ForkNumber forkNum, { /* * Ensure, while the spinlock's not yet held, that there's a free - * refcount entry. + * refcount entry and that the resoure owner has room to remember the + * pin. */ ReservePrivateRefCountEntry(); + ResourceOwnerEnlargeBuffers(CurrentResourceOwner); /* * Select a victim buffer. The buffer is returned with its header @@ -1677,8 +1676,6 @@ ReleaseAndReadBuffer(Buffer buffer, * taking the buffer header lock; instead update the state variable in loop of * CAS operations. Hopefully it's just a single CAS. * - * Note that ResourceOwnerEnlargeBuffers must have been done already. - * * Returns true if buffer is BM_VALID, else false. This provision allows * some callers to avoid an extra spinlock cycle. */ @@ -1689,6 +1686,8 @@ PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy) bool result; PrivateRefCountEntry *ref; + ResourceOwnerEnlargeBuffers(CurrentResourceOwner); + ref = GetPrivateRefCountEntry(b, true); if (ref == NULL) @@ -1769,7 +1768,8 @@ PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy) * The spinlock is released before return. * * As this function is called with the spinlock held, the caller has to - * previously call ReservePrivateRefCountEntry(). + * previously call ReservePrivateRefCountEntry() and + * ResourceOwnerEnlargeBuffers(CurrentResourceOwner); * * Currently, no callers of this function want to modify the buffer's * usage_count at all, so there's no need for a strategy parameter. @@ -1945,9 +1945,6 @@ BufferSync(int flags) int mask = BM_DIRTY; WritebackContext wb_context; - /* Make sure we can handle the pin inside SyncOneBuffer */ - ResourceOwnerEnlargeBuffers(CurrentResourceOwner); - /* * Unless this is a shutdown checkpoint or we have been explicitly told, * we write only permanent, dirty buffers. But at shutdown or end of @@ -2421,9 +2418,6 @@ BgBufferSync(WritebackContext *wb_context) * requirements, or hit the bgwriter_lru_maxpages limit. */ - /* Make sure we can handle the pin inside SyncOneBuffer */ - ResourceOwnerEnlargeBuffers(CurrentResourceOwner); - num_to_scan = bufs_to_lap; num_written = 0; reusable_buffers = reusable_buffers_est; @@ -2505,8 +2499,6 @@ BgBufferSync(WritebackContext *wb_context) * * (BUF_WRITTEN could be set in error if FlushBuffer finds the buffer clean * after locking it, but we don't care all that much.) - * - * Note: caller must have done ResourceOwnerEnlargeBuffers. */ static int SyncOneBuffer(int buf_id, bool skip_recently_used, WritebackContext *wb_context) @@ -2516,7 +2508,9 @@ SyncOneBuffer(int buf_id, bool skip_recently_used, WritebackContext *wb_context) uint32 buf_state; BufferTag tag; + /* Make sure we can handle the pin */ ReservePrivateRefCountEntry(); + ResourceOwnerEnlargeBuffers(CurrentResourceOwner); /* * Check whether buffer needs writing. @@ -3555,9 +3549,6 @@ FlushRelationBuffers(Relation rel) return; } - /* Make sure we can handle the pin inside the loop */ - ResourceOwnerEnlargeBuffers(CurrentResourceOwner); - for (i = 0; i < NBuffers; i++) { uint32 buf_state; @@ -3571,7 +3562,9 @@ FlushRelationBuffers(Relation rel) if (!RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node)) continue; + /* Make sure we can handle the pin */ ReservePrivateRefCountEntry(); + ResourceOwnerEnlargeBuffers(CurrentResourceOwner); buf_state = LockBufHdr(bufHdr); if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node) && @@ -3628,9 +3621,6 @@ FlushRelationsAllBuffers(SMgrRelation *smgrs, int nrels) if (use_bsearch) pg_qsort(srels, nrels, sizeof(SMgrSortArray), rnode_comparator); - /* Make sure we can handle the pin inside the loop */ - ResourceOwnerEnlargeBuffers(CurrentResourceOwner); - for (i = 0; i < NBuffers; i++) { SMgrSortArray *srelent = NULL; @@ -3667,7 +3657,9 @@ FlushRelationsAllBuffers(SMgrRelation *smgrs, int nrels) if (srelent == NULL) continue; + /* Make sure we can handle the pin */ ReservePrivateRefCountEntry(); + ResourceOwnerEnlargeBuffers(CurrentResourceOwner); buf_state = LockBufHdr(bufHdr); if (RelFileNodeEquals(bufHdr->tag.rnode, srelent->rnode) && @@ -3707,9 +3699,6 @@ FlushDatabaseBuffers(Oid dbid) int i; BufferDesc *bufHdr; - /* Make sure we can handle the pin inside the loop */ - ResourceOwnerEnlargeBuffers(CurrentResourceOwner); - for (i = 0; i < NBuffers; i++) { uint32 buf_state; @@ -3723,7 +3712,9 @@ FlushDatabaseBuffers(Oid dbid) if (bufHdr->tag.rnode.dbNode != dbid) continue; + /* Make sure we can handle the pin */ ReservePrivateRefCountEntry(); + ResourceOwnerEnlargeBuffers(CurrentResourceOwner); buf_state = LockBufHdr(bufHdr); if (bufHdr->tag.rnode.dbNode == dbid && diff --git a/src/backend/storage/buffer/localbuf.c b/src/backend/storage/buffer/localbuf.c index 04b3558ea33..f7c15ea8a44 100644 --- a/src/backend/storage/buffer/localbuf.c +++ b/src/backend/storage/buffer/localbuf.c @@ -123,6 +123,9 @@ LocalBufferAlloc(SMgrRelation smgr, ForkNumber forkNum, BlockNumber blockNum, if (LocalBufHash == NULL) InitLocalBuffers(); + /* Make sure we will have room to remember the buffer pin */ + ResourceOwnerEnlargeBuffers(CurrentResourceOwner); + /* See if the desired buffer already exists */ hresult = (LocalBufferLookupEnt *) hash_search(LocalBufHash, (void *) &newTag, HASH_FIND, NULL); diff --git a/src/backend/utils/cache/catcache.c b/src/backend/utils/cache/catcache.c index 4fbdc62d8c7..13eed587601 100644 --- a/src/backend/utils/cache/catcache.c +++ b/src/backend/utils/cache/catcache.c @@ -1609,8 +1609,6 @@ SearchCatCacheList(CatCache *cache, * block to ensure we can undo those refcounts if we get an error before * we finish constructing the CatCList. */ - ResourceOwnerEnlargeCatCacheListRefs(CurrentResourceOwner); - ctlist = NIL; PG_TRY(); @@ -1698,13 +1696,22 @@ SearchCatCacheList(CatCache *cache, table_close(relation, AccessShareLock); + /* Make sure the resource owner has room to remember this entry. */ + ResourceOwnerEnlargeCatCacheListRefs(CurrentResourceOwner); + /* Now we can build the CatCList entry. */ oldcxt = MemoryContextSwitchTo(CacheMemoryContext); nmembers = list_length(ctlist); cl = (CatCList *) palloc(offsetof(CatCList, members) + nmembers * sizeof(CatCTup *)); - /* Extract key values */ + /* + * Extract key values. + * + * XXX: If we run out of memory while copying the key values, we will + * leak any allocations we had already made in the CacheMemoryContext. + * That is unlikely enough that we just accept the risk. + */ CatCacheCopyKeys(cache->cc_tupdesc, nkeys, cache->cc_keyno, arguments, cl->keys); MemoryContextSwitchTo(oldcxt); -- 2.30.2