From 10b9af3ebbedfcbe696bf93d4db861db8de0de32 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sat, 1 Sep 2018 15:27:13 -0400 Subject: [PATCH] Avoid using potentially-under-aligned page buffers. There's a project policy against using plain "char buf[BLCKSZ]" local or static variables as page buffers; preferred style is to palloc or malloc each buffer to ensure it is MAXALIGN'd. However, that policy's been ignored in an increasing number of places. We've apparently got away with it so far, probably because (a) relatively few people use platforms on which misalignment causes core dumps and/or (b) the variables chance to be sufficiently aligned anyway. But this is not something to rely on. Moreover, even if we don't get a core dump, we might be paying a lot of cycles for misaligned accesses. To fix, invent new union types PGAlignedBlock and PGAlignedXLogBlock that the compiler must allocate with sufficient alignment, and use those in place of plain char arrays. I used these types even for variables where there's no risk of a misaligned access, since ensuring proper alignment should make kernel data transfers faster. I also changed some places where we had been palloc'ing short-lived buffers, for coding style uniformity and to save palloc/pfree overhead. Since this seems to be a live portability hazard (despite the lack of field reports), back-patch to all supported versions. Patch by me; thanks to Michael Paquier for review. Discussion: https://postgr.es/m/1535618100.1286.3.camel@credativ.de --- contrib/bloom/blinsert.c | 12 ++++----- contrib/pg_prewarm/pg_prewarm.c | 4 +-- src/backend/access/gin/ginentrypage.c | 6 ++--- src/backend/access/gin/ginfast.c | 11 +++----- src/backend/access/hash/hashpage.c | 8 +++--- src/backend/access/heap/heapam.c | 16 +++--------- src/backend/access/heap/visibilitymap.c | 11 +++----- src/backend/access/transam/generic_xlog.c | 21 +++++++-------- src/backend/access/transam/xlog.c | 26 +++++++++---------- src/backend/access/transam/xloginsert.c | 14 +++++----- src/backend/access/transam/xlogreader.c | 6 ++--- src/backend/commands/tablecmds.c | 17 +++---------- src/backend/replication/walsender.c | 6 ++--- src/backend/storage/file/buffile.c | 10 ++++---- src/backend/storage/freespace/freespace.c | 11 +++----- src/backend/utils/sort/logtape.c | 6 ++--- src/bin/pg_basebackup/walmethods.c | 20 +++++---------- src/bin/pg_resetwal/pg_resetwal.c | 14 +++++----- src/bin/pg_rewind/copy_fetch.c | 6 ++--- src/bin/pg_upgrade/file.c | 31 ++++++++--------------- src/include/c.h | 26 +++++++++++++++++++ 21 files changed, 129 insertions(+), 153 deletions(-) diff --git a/contrib/bloom/blinsert.c b/contrib/bloom/blinsert.c index 28c6c0ba6fc..0039c4785fe 100644 --- a/contrib/bloom/blinsert.c +++ b/contrib/bloom/blinsert.c @@ -36,7 +36,7 @@ typedef struct int64 indtuples; /* total number of tuples indexed */ MemoryContext tmpCtx; /* temporary memory context reset after each * tuple */ - char data[BLCKSZ]; /* cached page */ + PGAlignedBlock data; /* cached page */ int count; /* number of tuples in cached page */ } BloomBuildState; @@ -52,7 +52,7 @@ flushCachedPage(Relation index, BloomBuildState *buildstate) state = GenericXLogStart(index); page = GenericXLogRegisterBuffer(state, buffer, GENERIC_XLOG_FULL_IMAGE); - memcpy(page, buildstate->data, BLCKSZ); + memcpy(page, buildstate->data.data, BLCKSZ); GenericXLogFinish(state); UnlockReleaseBuffer(buffer); } @@ -63,8 +63,8 @@ flushCachedPage(Relation index, BloomBuildState *buildstate) static void initCachedPage(BloomBuildState *buildstate) { - memset(buildstate->data, 0, BLCKSZ); - BloomInitPage(buildstate->data, 0); + memset(buildstate->data.data, 0, BLCKSZ); + BloomInitPage(buildstate->data.data, 0); buildstate->count = 0; } @@ -84,7 +84,7 @@ bloomBuildCallback(Relation index, HeapTuple htup, Datum *values, itup = BloomFormTuple(&buildstate->blstate, &htup->t_self, values, isnull); /* Try to add next item to cached page */ - if (BloomPageAddItem(&buildstate->blstate, buildstate->data, itup)) + if (BloomPageAddItem(&buildstate->blstate, buildstate->data.data, itup)) { /* Next item was added successfully */ buildstate->count++; @@ -98,7 +98,7 @@ bloomBuildCallback(Relation index, HeapTuple htup, Datum *values, initCachedPage(buildstate); - if (!BloomPageAddItem(&buildstate->blstate, buildstate->data, itup)) + if (!BloomPageAddItem(&buildstate->blstate, buildstate->data.data, itup)) { /* We shouldn't be here since we're inserting to the empty page */ elog(ERROR, "could not add new bloom tuple to empty page"); diff --git a/contrib/pg_prewarm/pg_prewarm.c b/contrib/pg_prewarm/pg_prewarm.c index fec62b1a542..d0714025127 100644 --- a/contrib/pg_prewarm/pg_prewarm.c +++ b/contrib/pg_prewarm/pg_prewarm.c @@ -37,7 +37,7 @@ typedef enum PREWARM_BUFFER } PrewarmType; -static char blockbuffer[BLCKSZ]; +static PGAlignedBlock blockbuffer; /* * pg_prewarm(regclass, mode text, fork text, @@ -179,7 +179,7 @@ pg_prewarm(PG_FUNCTION_ARGS) for (block = first_block; block <= last_block; ++block) { CHECK_FOR_INTERRUPTS(); - smgrread(rel->rd_smgr, forkNumber, block, blockbuffer); + smgrread(rel->rd_smgr, forkNumber, block, blockbuffer.data); ++blocks_done; } } diff --git a/src/backend/access/gin/ginentrypage.c b/src/backend/access/gin/ginentrypage.c index d5cc70258ac..264f219d357 100644 --- a/src/backend/access/gin/ginentrypage.c +++ b/src/backend/access/gin/ginentrypage.c @@ -616,7 +616,7 @@ entrySplitPage(GinBtree btree, Buffer origbuf, Page lpage = PageGetTempPageCopy(BufferGetPage(origbuf)); Page rpage = PageGetTempPageCopy(BufferGetPage(origbuf)); Size pageSize = PageGetPageSize(lpage); - char tupstore[2 * BLCKSZ]; + PGAlignedBlock tupstore[2]; /* could need 2 pages' worth of tuples */ entryPreparePage(btree, lpage, off, insertData, updateblkno); @@ -625,7 +625,7 @@ entrySplitPage(GinBtree btree, Buffer origbuf, * one after another in a temporary workspace. */ maxoff = PageGetMaxOffsetNumber(lpage); - ptr = tupstore; + ptr = tupstore[0].data; for (i = FirstOffsetNumber; i <= maxoff; i++) { if (i == off) @@ -658,7 +658,7 @@ entrySplitPage(GinBtree btree, Buffer origbuf, GinInitPage(rpage, GinPageGetOpaque(lpage)->flags, pageSize); GinInitPage(lpage, GinPageGetOpaque(rpage)->flags, pageSize); - ptr = tupstore; + ptr = tupstore[0].data; maxoff++; lsize = 0; diff --git a/src/backend/access/gin/ginfast.c b/src/backend/access/gin/ginfast.c index ff610ef2184..144ca8b8e77 100644 --- a/src/backend/access/gin/ginfast.c +++ b/src/backend/access/gin/ginfast.c @@ -63,18 +63,15 @@ writeListPage(Relation index, Buffer buffer, size = 0; OffsetNumber l, off; - char *workspace; + PGAlignedBlock workspace; char *ptr; - /* workspace could be a local array; we use palloc for alignment */ - workspace = palloc(BLCKSZ); - START_CRIT_SECTION(); GinInitBuffer(buffer, GIN_LIST); off = FirstOffsetNumber; - ptr = workspace; + ptr = workspace.data; for (i = 0; i < ntuples; i++) { @@ -126,7 +123,7 @@ writeListPage(Relation index, Buffer buffer, XLogRegisterData((char *) &data, sizeof(ginxlogInsertListPage)); XLogRegisterBuffer(0, buffer, REGBUF_WILL_INIT); - XLogRegisterBufData(0, workspace, size); + XLogRegisterBufData(0, workspace.data, size); recptr = XLogInsert(RM_GIN_ID, XLOG_GIN_INSERT_LISTPAGE); PageSetLSN(page, recptr); @@ -139,8 +136,6 @@ writeListPage(Relation index, Buffer buffer, END_CRIT_SECTION(); - pfree(workspace); - return freesize; } diff --git a/src/backend/access/hash/hashpage.c b/src/backend/access/hash/hashpage.c index 7b2906b0ca9..bbf98de35ac 100644 --- a/src/backend/access/hash/hashpage.c +++ b/src/backend/access/hash/hashpage.c @@ -998,7 +998,7 @@ static bool _hash_alloc_buckets(Relation rel, BlockNumber firstblock, uint32 nblocks) { BlockNumber lastblock; - char zerobuf[BLCKSZ]; + PGAlignedBlock zerobuf; Page page; HashPageOpaque ovflopaque; @@ -1011,7 +1011,7 @@ _hash_alloc_buckets(Relation rel, BlockNumber firstblock, uint32 nblocks) if (lastblock < firstblock || lastblock == InvalidBlockNumber) return false; - page = (Page) zerobuf; + page = (Page) zerobuf.data; /* * Initialize the page. Just zeroing the page won't work; see @@ -1032,11 +1032,11 @@ _hash_alloc_buckets(Relation rel, BlockNumber firstblock, uint32 nblocks) log_newpage(&rel->rd_node, MAIN_FORKNUM, lastblock, - zerobuf, + zerobuf.data, true); RelationOpenSmgr(rel); - smgrextend(rel->rd_smgr, MAIN_FORKNUM, lastblock, zerobuf, false); + smgrextend(rel->rd_smgr, MAIN_FORKNUM, lastblock, zerobuf.data, false); return true; } diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c index 608dc5a77f0..44d150f706f 100644 --- a/src/backend/access/heap/heapam.c +++ b/src/backend/access/heap/heapam.c @@ -2662,7 +2662,7 @@ heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples, HeapTuple *heaptuples; int i; int ndone; - char *scratch = NULL; + PGAlignedBlock scratch; Page page; bool needwal; Size saveFreeSpace; @@ -2679,14 +2679,6 @@ heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples, heaptuples[i] = heap_prepare_insert(relation, tuples[i], xid, cid, options); - /* - * Allocate some memory to use for constructing the WAL record. Using - * palloc() within a critical section is not safe, so we allocate this - * beforehand. - */ - if (needwal) - scratch = palloc(BLCKSZ); - /* * We're about to do the actual inserts -- but check for conflict first, * to minimize the possibility of having to roll back work we've just @@ -2779,7 +2771,7 @@ heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples, uint8 info = XLOG_HEAP2_MULTI_INSERT; char *tupledata; int totaldatalen; - char *scratchptr = scratch; + char *scratchptr = scratch.data; bool init; int bufflags = 0; @@ -2838,7 +2830,7 @@ heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples, scratchptr += datalen; } totaldatalen = scratchptr - tupledata; - Assert((scratchptr - scratch) < BLCKSZ); + Assert((scratchptr - scratch.data) < BLCKSZ); if (need_tuple_data) xlrec->flags |= XLH_INSERT_CONTAINS_NEW_TUPLE; @@ -2865,7 +2857,7 @@ heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples, bufflags |= REGBUF_KEEP_DATA; XLogBeginInsert(); - XLogRegisterData((char *) xlrec, tupledata - scratch); + XLogRegisterData((char *) xlrec, tupledata - scratch.data); XLogRegisterBuffer(0, buffer, REGBUF_STANDARD | bufflags); XLogRegisterBufData(0, tupledata, totaldatalen); diff --git a/src/backend/access/heap/visibilitymap.c b/src/backend/access/heap/visibilitymap.c index fc3ea13b5bd..aa8cdec3505 100644 --- a/src/backend/access/heap/visibilitymap.c +++ b/src/backend/access/heap/visibilitymap.c @@ -645,10 +645,9 @@ static void vm_extend(Relation rel, BlockNumber vm_nblocks) { BlockNumber vm_nblocks_now; - Page pg; + PGAlignedBlock pg; - pg = (Page) palloc(BLCKSZ); - PageInit(pg, BLCKSZ, 0); + PageInit((Page) pg.data, BLCKSZ, 0); /* * We use the relation extension lock to lock out other backends trying to @@ -679,10 +678,10 @@ vm_extend(Relation rel, BlockNumber vm_nblocks) /* Now extend the file */ while (vm_nblocks_now < vm_nblocks) { - PageSetChecksumInplace(pg, vm_nblocks_now); + PageSetChecksumInplace((Page) pg.data, vm_nblocks_now); smgrextend(rel->rd_smgr, VISIBILITYMAP_FORKNUM, vm_nblocks_now, - (char *) pg, false); + pg.data, false); vm_nblocks_now++; } @@ -699,6 +698,4 @@ vm_extend(Relation rel, BlockNumber vm_nblocks) rel->rd_smgr->smgr_vm_nblocks = vm_nblocks_now; UnlockRelationForExtension(rel, ExclusiveLock); - - pfree(pg); } diff --git a/src/backend/access/transam/generic_xlog.c b/src/backend/access/transam/generic_xlog.c index 3adbf7b9494..470ed887ce4 100644 --- a/src/backend/access/transam/generic_xlog.c +++ b/src/backend/access/transam/generic_xlog.c @@ -61,14 +61,11 @@ typedef struct /* State of generic xlog record construction */ struct GenericXLogState { - /* - * page's images. Should be first in this struct to have MAXALIGN'ed - * images addresses, because some code working with pages directly aligns - * addresses, not offsets from beginning of page - */ - char images[MAX_GENERIC_XLOG_PAGES * BLCKSZ]; + /* Info about each page, see above */ PageData pages[MAX_GENERIC_XLOG_PAGES]; bool isLogged; + /* Page images (properly aligned) */ + PGAlignedBlock images[MAX_GENERIC_XLOG_PAGES]; }; static void writeFragment(PageData *pageData, OffsetNumber offset, @@ -251,12 +248,12 @@ computeDelta(PageData *pageData, Page curpage, Page targetpage) #ifdef WAL_DEBUG if (XLOG_DEBUG) { - char tmp[BLCKSZ]; + PGAlignedBlock tmp; - memcpy(tmp, curpage, BLCKSZ); - applyPageRedo(tmp, pageData->delta, pageData->deltaLen); - if (memcmp(tmp, targetpage, targetLower) != 0 || - memcmp(tmp + targetUpper, targetpage + targetUpper, + memcpy(tmp.data, curpage, BLCKSZ); + applyPageRedo(tmp.data, pageData->delta, pageData->deltaLen); + if (memcmp(tmp.data, targetpage, targetLower) != 0 || + memcmp(tmp.data + targetUpper, targetpage + targetUpper, BLCKSZ - targetUpper) != 0) elog(ERROR, "result of generic xlog apply does not match"); } @@ -277,7 +274,7 @@ GenericXLogStart(Relation relation) for (i = 0; i < MAX_GENERIC_XLOG_PAGES; i++) { - state->pages[i].image = state->images + BLCKSZ * i; + state->pages[i].image = state->images[i].data; state->pages[i].buffer = InvalidBuffer; } diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index e9a66aa7062..651b0f3a84d 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -3182,8 +3182,7 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock) { char path[MAXPGPATH]; char tmppath[MAXPGPATH]; - char zbuffer_raw[XLOG_BLCKSZ + MAXIMUM_ALIGNOF]; - char *zbuffer; + PGAlignedXLogBlock zbuffer; XLogSegNo installed_segno; XLogSegNo max_segno; int fd; @@ -3237,17 +3236,13 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock) * fsync below) that all the indirect blocks are down on disk. Therefore, * fdatasync(2) or O_DSYNC will be sufficient to sync future writes to the * log file. - * - * Note: ensure the buffer is reasonably well-aligned; this may save a few - * cycles transferring data to the kernel. */ - zbuffer = (char *) MAXALIGN(zbuffer_raw); - memset(zbuffer, 0, XLOG_BLCKSZ); + memset(zbuffer.data, 0, XLOG_BLCKSZ); for (nbytes = 0; nbytes < XLogSegSize; nbytes += XLOG_BLCKSZ) { errno = 0; pgstat_report_wait_start(WAIT_EVENT_WAL_INIT_WRITE); - if ((int) write(fd, zbuffer, XLOG_BLCKSZ) != (int) XLOG_BLCKSZ) + if ((int) write(fd, zbuffer.data, XLOG_BLCKSZ) != (int) XLOG_BLCKSZ) { int save_errno = errno; @@ -3355,7 +3350,7 @@ XLogFileCopy(XLogSegNo destsegno, TimeLineID srcTLI, XLogSegNo srcsegno, { char path[MAXPGPATH]; char tmppath[MAXPGPATH]; - char buffer[XLOG_BLCKSZ]; + PGAlignedXLogBlock buffer; int srcfd; int fd; int nbytes; @@ -3399,7 +3394,7 @@ XLogFileCopy(XLogSegNo destsegno, TimeLineID srcTLI, XLogSegNo srcsegno, * zeros. */ if (nread < sizeof(buffer)) - memset(buffer, 0, sizeof(buffer)); + memset(buffer.data, 0, sizeof(buffer)); if (nread > 0) { @@ -3407,7 +3402,7 @@ XLogFileCopy(XLogSegNo destsegno, TimeLineID srcTLI, XLogSegNo srcsegno, nread = sizeof(buffer); errno = 0; pgstat_report_wait_start(WAIT_EVENT_WAL_COPY_READ); - if (read(srcfd, buffer, nread) != nread) + if (read(srcfd, buffer.data, nread) != nread) { if (errno != 0) ereport(ERROR, @@ -3423,7 +3418,7 @@ XLogFileCopy(XLogSegNo destsegno, TimeLineID srcTLI, XLogSegNo srcsegno, } errno = 0; pgstat_report_wait_start(WAIT_EVENT_WAL_COPY_WRITE); - if ((int) write(fd, buffer, sizeof(buffer)) != (int) sizeof(buffer)) + if ((int) write(fd, buffer.data, sizeof(buffer)) != (int) sizeof(buffer)) { int save_errno = errno; @@ -6410,8 +6405,11 @@ StartupXLOG(void) xlogreader->system_identifier = ControlFile->system_identifier; /* - * Allocate pages dedicated to WAL consistency checks, those had better be - * aligned. + * Allocate two page buffers dedicated to WAL consistency checks. We do + * it this way, rather than just making static arrays, for two reasons: + * (1) no need to waste the storage in most instantiations of the backend; + * (2) a static char array isn't guaranteed to have any particular + * alignment, whereas palloc() will provide MAXALIGN'd storage. */ replay_image_masked = (char *) palloc(BLCKSZ); master_image_masked = (char *) palloc(BLCKSZ); diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c index 3af03ecdb12..1f86c907598 100644 --- a/src/backend/access/transam/xloginsert.c +++ b/src/backend/access/transam/xloginsert.c @@ -809,12 +809,12 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length, int32 len; int32 extra_bytes = 0; char *source; - char tmp[BLCKSZ]; + PGAlignedBlock tmp; if (hole_length != 0) { /* must skip the hole */ - source = tmp; + source = tmp.data; memcpy(source, page, hole_offset); memcpy(source + hole_offset, page + (hole_offset + hole_length), @@ -917,7 +917,7 @@ XLogSaveBufferForHint(Buffer buffer, bool buffer_std) if (lsn <= RedoRecPtr) { int flags; - char copied_buffer[BLCKSZ]; + PGAlignedBlock copied_buffer; char *origdata = (char *) BufferGetBlock(buffer); RelFileNode rnode; ForkNumber forkno; @@ -935,11 +935,11 @@ XLogSaveBufferForHint(Buffer buffer, bool buffer_std) uint16 lower = ((PageHeader) page)->pd_lower; uint16 upper = ((PageHeader) page)->pd_upper; - memcpy(copied_buffer, origdata, lower); - memcpy(copied_buffer + upper, origdata + upper, BLCKSZ - upper); + memcpy(copied_buffer.data, origdata, lower); + memcpy(copied_buffer.data + upper, origdata + upper, BLCKSZ - upper); } else - memcpy(copied_buffer, origdata, BLCKSZ); + memcpy(copied_buffer.data, origdata, BLCKSZ); XLogBeginInsert(); @@ -948,7 +948,7 @@ XLogSaveBufferForHint(Buffer buffer, bool buffer_std) flags |= REGBUF_STANDARD; BufferGetTag(buffer, &rnode, &forkno, &blkno); - XLogRegisterBlock(0, &rnode, forkno, blkno, copied_buffer, flags); + XLogRegisterBlock(0, &rnode, forkno, blkno, copied_buffer.data, flags); recptr = XLogInsert(RM_XLOG_ID, XLOG_FPI_FOR_HINT); } diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c index 8e83de6de52..2a2cbfb3fc8 100644 --- a/src/backend/access/transam/xlogreader.c +++ b/src/backend/access/transam/xlogreader.c @@ -1404,7 +1404,7 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page) { DecodedBkpBlock *bkpb; char *ptr; - char tmp[BLCKSZ]; + PGAlignedBlock tmp; if (!record->blocks[block_id].in_use) return false; @@ -1417,7 +1417,7 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page) if (bkpb->bimg_info & BKPIMAGE_IS_COMPRESSED) { /* If a backup block image is compressed, decompress it */ - if (pglz_decompress(ptr, bkpb->bimg_len, tmp, + if (pglz_decompress(ptr, bkpb->bimg_len, tmp.data, BLCKSZ - bkpb->hole_length) < 0) { report_invalid_record(record, "invalid compressed image at %X/%X, block %d", @@ -1426,7 +1426,7 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page) block_id); return false; } - ptr = tmp; + ptr = tmp.data; } /* generate page, taking into account hole if necessary */ diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c index 6f1a429c7e5..0b518cf6721 100644 --- a/src/backend/commands/tablecmds.c +++ b/src/backend/commands/tablecmds.c @@ -10820,21 +10820,14 @@ static void copy_relation_data(SMgrRelation src, SMgrRelation dst, ForkNumber forkNum, char relpersistence) { - char *buf; + PGAlignedBlock buf; Page page; bool use_wal; bool copying_initfork; BlockNumber nblocks; BlockNumber blkno; - /* - * palloc the buffer so that it's MAXALIGN'd. If it were just a local - * char[] array, the compiler might align it on any byte boundary, which - * can seriously hurt transfer speed to and from the kernel; not to - * mention possibly making log_newpage's accesses to the page header fail. - */ - buf = (char *) palloc(BLCKSZ); - page = (Page) buf; + page = (Page) buf.data; /* * The init fork for an unlogged relation in many respects has to be @@ -10858,7 +10851,7 @@ copy_relation_data(SMgrRelation src, SMgrRelation dst, /* If we got a cancel signal during the copy of the data, quit */ CHECK_FOR_INTERRUPTS(); - smgrread(src, forkNum, blkno, buf); + smgrread(src, forkNum, blkno, buf.data); if (!PageIsVerified(page, blkno)) ereport(ERROR, @@ -10884,11 +10877,9 @@ copy_relation_data(SMgrRelation src, SMgrRelation dst, * rel, because there's no need for smgr to schedule an fsync for this * write; we'll do it ourselves below. */ - smgrextend(dst, forkNum, blkno, buf, true); + smgrextend(dst, forkNum, blkno, buf.data, true); } - pfree(buf); - /* * If the rel is WAL-logged, must fsync before commit. We use heap_sync * to ensure that the toast table gets fsync'd too. (For a temp or diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c index 3256db203e0..37e44bd7f23 100644 --- a/src/backend/replication/walsender.c +++ b/src/backend/replication/walsender.c @@ -498,18 +498,18 @@ SendTimeLineHistory(TimeLineHistoryCmd *cmd) bytesleft = histfilelen; while (bytesleft > 0) { - char rbuf[BLCKSZ]; + PGAlignedBlock rbuf; int nread; pgstat_report_wait_start(WAIT_EVENT_WALSENDER_TIMELINE_HISTORY_READ); - nread = read(fd, rbuf, sizeof(rbuf)); + nread = read(fd, rbuf.data, sizeof(rbuf)); pgstat_report_wait_end(); if (nread <= 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not read file \"%s\": %m", path))); - pq_sendbytes(&buf, rbuf, nread); + pq_sendbytes(&buf, rbuf.data, nread); bytesleft -= nread; } CloseTransientFile(fd); diff --git a/src/backend/storage/file/buffile.c b/src/backend/storage/file/buffile.c index 4ca0ea4f2a3..01546da7cff 100644 --- a/src/backend/storage/file/buffile.c +++ b/src/backend/storage/file/buffile.c @@ -87,7 +87,7 @@ struct BufFile off_t curOffset; /* offset part of current pos */ int pos; /* next read/write position in buffer */ int nbytes; /* total # of valid bytes in buffer */ - char buffer[BLCKSZ]; + PGAlignedBlock buffer; }; static BufFile *makeBufFile(File firstfile); @@ -256,7 +256,7 @@ BufFileLoadBuffer(BufFile *file) * Read whatever we can get, up to a full bufferload. */ file->nbytes = FileRead(thisfile, - file->buffer, + file->buffer.data, sizeof(file->buffer), WAIT_EVENT_BUFFILE_READ); if (file->nbytes < 0) @@ -322,7 +322,7 @@ BufFileDumpBuffer(BufFile *file) file->offsets[file->curFile] = file->curOffset; } bytestowrite = FileWrite(thisfile, - file->buffer + wpos, + file->buffer.data + wpos, bytestowrite, WAIT_EVENT_BUFFILE_WRITE); if (bytestowrite <= 0) @@ -392,7 +392,7 @@ BufFileRead(BufFile *file, void *ptr, size_t size) nthistime = size; Assert(nthistime > 0); - memcpy(ptr, file->buffer + file->pos, nthistime); + memcpy(ptr, file->buffer.data + file->pos, nthistime); file->pos += nthistime; ptr = (void *) ((char *) ptr + nthistime); @@ -439,7 +439,7 @@ BufFileWrite(BufFile *file, void *ptr, size_t size) nthistime = size; Assert(nthistime > 0); - memcpy(file->buffer + file->pos, ptr, nthistime); + memcpy(file->buffer.data + file->pos, ptr, nthistime); file->dirty = true; file->pos += nthistime; diff --git a/src/backend/storage/freespace/freespace.c b/src/backend/storage/freespace/freespace.c index 3eee5b31aaa..42d2016570f 100644 --- a/src/backend/storage/freespace/freespace.c +++ b/src/backend/storage/freespace/freespace.c @@ -628,10 +628,9 @@ static void fsm_extend(Relation rel, BlockNumber fsm_nblocks) { BlockNumber fsm_nblocks_now; - Page pg; + PGAlignedBlock pg; - pg = (Page) palloc(BLCKSZ); - PageInit(pg, BLCKSZ, 0); + PageInit((Page) pg.data, BLCKSZ, 0); /* * We use the relation extension lock to lock out other backends trying to @@ -661,10 +660,10 @@ fsm_extend(Relation rel, BlockNumber fsm_nblocks) while (fsm_nblocks_now < fsm_nblocks) { - PageSetChecksumInplace(pg, fsm_nblocks_now); + PageSetChecksumInplace((Page) pg.data, fsm_nblocks_now); smgrextend(rel->rd_smgr, FSM_FORKNUM, fsm_nblocks_now, - (char *) pg, false); + pg.data, false); fsm_nblocks_now++; } @@ -672,8 +671,6 @@ fsm_extend(Relation rel, BlockNumber fsm_nblocks) rel->rd_smgr->smgr_fsm_nblocks = fsm_nblocks_now; UnlockRelationForExtension(rel, ExclusiveLock); - - pfree(pg); } /* diff --git a/src/backend/utils/sort/logtape.c b/src/backend/utils/sort/logtape.c index d454fd1939f..4b946e1b496 100644 --- a/src/backend/utils/sort/logtape.c +++ b/src/backend/utils/sort/logtape.c @@ -215,11 +215,11 @@ ltsWriteBlock(LogicalTapeSet *lts, long blocknum, void *buffer) */ while (blocknum > lts->nBlocksWritten) { - char zerobuf[BLCKSZ]; + PGAlignedBlock zerobuf; - MemSet(zerobuf, 0, sizeof(zerobuf)); + MemSet(zerobuf.data, 0, sizeof(zerobuf)); - ltsWriteBlock(lts, lts->nBlocksWritten, zerobuf); + ltsWriteBlock(lts, lts->nBlocksWritten, zerobuf.data); } /* Write the requested block */ diff --git a/src/bin/pg_basebackup/walmethods.c b/src/bin/pg_basebackup/walmethods.c index 870b6d085e8..2953ba463dd 100644 --- a/src/bin/pg_basebackup/walmethods.c +++ b/src/bin/pg_basebackup/walmethods.c @@ -115,18 +115,17 @@ dir_open_for_write(const char *pathname, const char *temp_suffix, size_t pad_to_ /* Do pre-padding on non-compressed files */ if (pad_to_size && dir_data->compression == 0) { - char *zerobuf; + PGAlignedXLogBlock zerobuf; int bytes; - zerobuf = pg_malloc0(XLOG_BLCKSZ); + memset(zerobuf.data, 0, XLOG_BLCKSZ); for (bytes = 0; bytes < pad_to_size; bytes += XLOG_BLCKSZ) { errno = 0; - if (write(fd, zerobuf, XLOG_BLCKSZ) != XLOG_BLCKSZ) + if (write(fd, zerobuf.data, XLOG_BLCKSZ) != XLOG_BLCKSZ) { int save_errno = errno; - pg_free(zerobuf); close(fd); /* @@ -136,7 +135,6 @@ dir_open_for_write(const char *pathname, const char *temp_suffix, size_t pad_to_ return NULL; } } - pg_free(zerobuf); if (lseek(fd, 0, SEEK_SET) != 0) { @@ -512,24 +510,20 @@ tar_write(Walfile f, const void *buf, size_t count) static bool tar_write_padding_data(TarMethodFile *f, size_t bytes) { - char *zerobuf = pg_malloc0(XLOG_BLCKSZ); + PGAlignedXLogBlock zerobuf; size_t bytesleft = bytes; + memset(zerobuf.data, 0, XLOG_BLCKSZ); while (bytesleft) { - size_t bytestowrite = bytesleft > XLOG_BLCKSZ ? XLOG_BLCKSZ : bytesleft; - - ssize_t r = tar_write(f, zerobuf, bytestowrite); + size_t bytestowrite = Min(bytesleft, XLOG_BLCKSZ); + ssize_t r = tar_write(f, zerobuf.data, bytestowrite); if (r < 0) - { - pg_free(zerobuf); return false; - } bytesleft -= r; } - pg_free(zerobuf); return true; } diff --git a/src/bin/pg_resetwal/pg_resetwal.c b/src/bin/pg_resetwal/pg_resetwal.c index ac678317795..0e6d790246f 100644 --- a/src/bin/pg_resetwal/pg_resetwal.c +++ b/src/bin/pg_resetwal/pg_resetwal.c @@ -1129,7 +1129,7 @@ KillExistingArchiveStatus(void) static void WriteEmptyXLOG(void) { - char *buffer; + PGAlignedXLogBlock buffer; XLogPageHeader page; XLogLongPageHeader longpage; XLogRecord *record; @@ -1139,12 +1139,10 @@ WriteEmptyXLOG(void) int nbytes; char *recptr; - /* Use malloc() to ensure buffer is MAXALIGNED */ - buffer = (char *) pg_malloc(XLOG_BLCKSZ); - page = (XLogPageHeader) buffer; - memset(buffer, 0, XLOG_BLCKSZ); + memset(buffer.data, 0, XLOG_BLCKSZ); /* Set up the XLOG page header */ + page = (XLogPageHeader) buffer.data; page->xlp_magic = XLOG_PAGE_MAGIC; page->xlp_info = XLP_LONG_HEADER; page->xlp_tli = ControlFile.checkPointCopy.ThisTimeLineID; @@ -1190,7 +1188,7 @@ WriteEmptyXLOG(void) } errno = 0; - if (write(fd, buffer, XLOG_BLCKSZ) != XLOG_BLCKSZ) + if (write(fd, buffer.data, XLOG_BLCKSZ) != XLOG_BLCKSZ) { /* if write didn't set errno, assume problem is no disk space */ if (errno == 0) @@ -1201,11 +1199,11 @@ WriteEmptyXLOG(void) } /* Fill the rest of the file with zeroes */ - memset(buffer, 0, XLOG_BLCKSZ); + memset(buffer.data, 0, XLOG_BLCKSZ); for (nbytes = XLOG_BLCKSZ; nbytes < XLogSegSize; nbytes += XLOG_BLCKSZ) { errno = 0; - if (write(fd, buffer, XLOG_BLCKSZ) != XLOG_BLCKSZ) + if (write(fd, buffer.data, XLOG_BLCKSZ) != XLOG_BLCKSZ) { if (errno == 0) errno = ENOSPC; diff --git a/src/bin/pg_rewind/copy_fetch.c b/src/bin/pg_rewind/copy_fetch.c index a1b85f7706f..ad8e407da22 100644 --- a/src/bin/pg_rewind/copy_fetch.c +++ b/src/bin/pg_rewind/copy_fetch.c @@ -158,7 +158,7 @@ recurse_dir(const char *datadir, const char *parentpath, static void rewind_copy_file_range(const char *path, off_t begin, off_t end, bool trunc) { - char buf[BLCKSZ]; + PGAlignedBlock buf; char srcpath[MAXPGPATH]; int srcfd; @@ -184,7 +184,7 @@ rewind_copy_file_range(const char *path, off_t begin, off_t end, bool trunc) else len = end - begin; - readlen = read(srcfd, buf, len); + readlen = read(srcfd, buf.data, len); if (readlen < 0) pg_fatal("could not read file \"%s\": %s\n", @@ -192,7 +192,7 @@ rewind_copy_file_range(const char *path, off_t begin, off_t end, bool trunc) else if (readlen == 0) pg_fatal("unexpected EOF while reading file \"%s\"\n", srcpath); - write_target_range(buf, begin, readlen); + write_target_range(buf.data, begin, readlen); begin += readlen; } diff --git a/src/bin/pg_upgrade/file.c b/src/bin/pg_upgrade/file.c index b8be9a5bda0..c9fd0316565 100644 --- a/src/bin/pg_upgrade/file.c +++ b/src/bin/pg_upgrade/file.c @@ -131,8 +131,8 @@ rewriteVisibilityMap(const char *fromfile, const char *tofile, { int src_fd; int dst_fd; - char *buffer; - char *new_vmbuf; + PGAlignedBlock buffer; + PGAlignedBlock new_vmbuf; ssize_t totalBytesRead = 0; ssize_t src_filesize; int rewriteVmBytesPerPage; @@ -158,13 +158,6 @@ rewriteVisibilityMap(const char *fromfile, const char *tofile, /* Save old file size */ src_filesize = statbuf.st_size; - /* - * Malloc the work buffers, rather than making them local arrays, to - * ensure adequate alignment. - */ - buffer = (char *) pg_malloc(BLCKSZ); - new_vmbuf = (char *) pg_malloc(BLCKSZ); - /* * Turn each visibility map page into 2 pages one by one. Each new page * has the same page header as the old one. If the last section of the @@ -180,7 +173,7 @@ rewriteVisibilityMap(const char *fromfile, const char *tofile, PageHeaderData pageheader; bool old_lastblk; - if ((bytesRead = read(src_fd, buffer, BLCKSZ)) != BLCKSZ) + if ((bytesRead = read(src_fd, buffer.data, BLCKSZ)) != BLCKSZ) { if (bytesRead < 0) pg_fatal("error while copying relation \"%s.%s\": could not read file \"%s\": %s\n", @@ -194,7 +187,7 @@ rewriteVisibilityMap(const char *fromfile, const char *tofile, old_lastblk = (totalBytesRead == src_filesize); /* Save the page header data */ - memcpy(&pageheader, buffer, SizeOfPageHeaderData); + memcpy(&pageheader, buffer.data, SizeOfPageHeaderData); /* * These old_* variables point to old visibility map page. old_cur @@ -202,8 +195,8 @@ rewriteVisibilityMap(const char *fromfile, const char *tofile, * old block. old_break is the end+1 position on the old page for the * data that will be transferred to the current new page. */ - old_cur = buffer + SizeOfPageHeaderData; - old_blkend = buffer + bytesRead; + old_cur = buffer.data + SizeOfPageHeaderData; + old_blkend = buffer.data + bytesRead; old_break = old_cur + rewriteVmBytesPerPage; while (old_break <= old_blkend) @@ -213,12 +206,12 @@ rewriteVisibilityMap(const char *fromfile, const char *tofile, bool old_lastpart; /* First, copy old page header to new page */ - memcpy(new_vmbuf, &pageheader, SizeOfPageHeaderData); + memcpy(new_vmbuf.data, &pageheader, SizeOfPageHeaderData); /* Rewriting the last part of the last old page? */ old_lastpart = old_lastblk && (old_break == old_blkend); - new_cur = new_vmbuf + SizeOfPageHeaderData; + new_cur = new_vmbuf.data + SizeOfPageHeaderData; /* Process old page bytes one by one, and turn it into new page. */ while (old_cur < old_break) @@ -252,11 +245,11 @@ rewriteVisibilityMap(const char *fromfile, const char *tofile, /* Set new checksum for visibility map page, if enabled */ if (new_cluster.controldata.data_checksum_version != 0) - ((PageHeader) new_vmbuf)->pd_checksum = - pg_checksum_page(new_vmbuf, new_blkno); + ((PageHeader) new_vmbuf.data)->pd_checksum = + pg_checksum_page(new_vmbuf.data, new_blkno); errno = 0; - if (write(dst_fd, new_vmbuf, BLCKSZ) != BLCKSZ) + if (write(dst_fd, new_vmbuf.data, BLCKSZ) != BLCKSZ) { /* if write didn't set errno, assume problem is no disk space */ if (errno == 0) @@ -272,8 +265,6 @@ rewriteVisibilityMap(const char *fromfile, const char *tofile, } /* Clean up */ - pg_free(buffer); - pg_free(new_vmbuf); close(dst_fd); close(src_fd); } diff --git a/src/include/c.h b/src/include/c.h index d9f26fb6d0b..59b2e18cb7f 100644 --- a/src/include/c.h +++ b/src/include/c.h @@ -969,6 +969,32 @@ typedef NameData *Name; * ---------------------------------------------------------------- */ +/* + * Use this, not "char buf[BLCKSZ]", to declare a field or local variable + * holding a page buffer, if that page might be accessed as a page and not + * just a string of bytes. Otherwise the variable might be under-aligned, + * causing problems on alignment-picky hardware. (In some places, we use + * this to declare buffers even though we only pass them to read() and + * write(), because copying to/from aligned buffers is usually faster than + * using unaligned buffers.) We include both "double" and "int64" in the + * union to ensure that the compiler knows the value must be MAXALIGN'ed + * (cf. configure's computation of MAXIMUM_ALIGNOF). + */ +typedef union PGAlignedBlock +{ + char data[BLCKSZ]; + double force_align_d; + int64 force_align_i64; +} PGAlignedBlock; + +/* Same, but for an XLOG_BLCKSZ-sized buffer */ +typedef union PGAlignedXLogBlock +{ + char data[XLOG_BLCKSZ]; + double force_align_d; + int64 force_align_i64; +} PGAlignedXLogBlock; + /* msb for char */ #define HIGHBIT (0x80) #define IS_HIGHBIT_SET(ch) ((unsigned char)(ch) & HIGHBIT)