1 /*-------------------------------------------------------------------------
2 *
3 * xloginsert.c
4 * Functions for constructing WAL records
5 *
6 * Constructing a WAL record begins with a call to XLogBeginInsert,
7 * followed by a number of XLogRegister* calls. The registered data is
8 * collected in private working memory, and finally assembled into a chain
9 * of XLogRecData structs by a call to XLogRecordAssemble(). See
10 * access/transam/README for details.
11 *
12 * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
13 * Portions Copyright (c) 1994, Regents of the University of California
14 *
15 * src/backend/access/transam/xloginsert.c
16 *
17 *-------------------------------------------------------------------------
18 */
19
20 #include "postgres.h"
21
22 #include "access/xact.h"
23 #include "access/xlog.h"
24 #include "access/xlog_internal.h"
25 #include "access/xloginsert.h"
26 #include "catalog/pg_control.h"
27 #include "common/pg_lzcompress.h"
28 #include "miscadmin.h"
29 #include "replication/origin.h"
30 #include "storage/bufmgr.h"
31 #include "storage/proc.h"
32 #include "utils/memutils.h"
33 #include "pg_trace.h"
34
35 /* Buffer size required to store a compressed version of backup block image */
36 #define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
37
38 /*
39 * For each block reference registered with XLogRegisterBuffer, we fill in
40 * a registered_buffer struct.
41 */
42 typedef struct
43 {
44 bool in_use; /* is this slot in use? */
45 uint8 flags; /* REGBUF_* flags */
46 RelFileNode rnode; /* identifies the relation and block */
47 ForkNumber forkno;
48 BlockNumber block;
49 Page page; /* page content */
50 uint32 rdata_len; /* total length of data in rdata chain */
51 XLogRecData *rdata_head; /* head of the chain of data registered with
52 * this block */
53 XLogRecData *rdata_tail; /* last entry in the chain, or &rdata_head if
54 * empty */
55
56 XLogRecData bkp_rdatas[2]; /* temporary rdatas used to hold references to
57 * backup block data in XLogRecordAssemble() */
58
59 /* buffer to store a compressed version of backup block image */
60 char compressed_page[PGLZ_MAX_BLCKSZ];
61 } registered_buffer;
62
63 static registered_buffer *registered_buffers;
64 static int max_registered_buffers; /* allocated size */
65 static int max_registered_block_id = 0; /* highest block_id + 1
66 * currently registered */
67
68 /*
69 * A chain of XLogRecDatas to hold the "main data" of a WAL record, registered
70 * with XLogRegisterData(...).
71 */
72 static XLogRecData *mainrdata_head;
73 static XLogRecData *mainrdata_last = (XLogRecData *) &mainrdata_head;
74 static uint32 mainrdata_len; /* total # of bytes in chain */
75
76 /* Should the in-progress insertion log the origin? */
77 static bool include_origin = false;
78
79 /*
80 * These are used to hold the record header while constructing a record.
81 * 'hdr_scratch' is not a plain variable, but is palloc'd at initialization,
82 * because we want it to be MAXALIGNed and padding bytes zeroed.
83 *
84 * For simplicity, it's allocated large enough to hold the headers for any
85 * WAL record.
86 */
87 static XLogRecData hdr_rdt;
88 static char *hdr_scratch = NULL;
89
90 #define SizeOfXlogOrigin (sizeof(RepOriginId) + sizeof(char))
91
92 #define HEADER_SCRATCH_SIZE \
93 (SizeOfXLogRecord + \
94 MaxSizeOfXLogRecordBlockHeader * (XLR_MAX_BLOCK_ID + 1) + \
95 SizeOfXLogRecordDataHeaderLong + SizeOfXlogOrigin)
96
97 /*
98 * An array of XLogRecData structs, to hold registered data.
99 */
100 static XLogRecData *rdatas;
101 static int num_rdatas; /* entries currently used */
102 static int max_rdatas; /* allocated size */
103
104 static bool begininsert_called = false;
105
106 /* Memory context to hold the registered buffer and data references. */
107 static MemoryContext xloginsert_cxt;
108
109 static XLogRecData *XLogRecordAssemble(RmgrId rmid, uint8 info,
110 XLogRecPtr RedoRecPtr, bool doPageWrites,
111 XLogRecPtr *fpw_lsn);
112 static bool XLogCompressBackupBlock(char *page, uint16 hole_offset,
113 uint16 hole_length, char *dest, uint16 *dlen);
114
115 /*
116 * Begin constructing a WAL record. This must be called before the
117 * XLogRegister* functions and XLogInsert().
118 */
119 void
XLogBeginInsert(void)120 XLogBeginInsert(void)
121 {
122 Assert(max_registered_block_id == 0);
123 Assert(mainrdata_last == (XLogRecData *) &mainrdata_head);
124 Assert(mainrdata_len == 0);
125
126 /* cross-check on whether we should be here or not */
127 if (!XLogInsertAllowed())
128 elog(ERROR, "cannot make new WAL entries during recovery");
129
130 if (begininsert_called)
131 elog(ERROR, "XLogBeginInsert was already called");
132
133 begininsert_called = true;
134 }
135
136 /*
137 * Ensure that there are enough buffer and data slots in the working area,
138 * for subsequent XLogRegisterBuffer, XLogRegisterData and XLogRegisterBufData
139 * calls.
140 *
141 * There is always space for a small number of buffers and data chunks, enough
142 * for most record types. This function is for the exceptional cases that need
143 * more.
144 */
145 void
XLogEnsureRecordSpace(int max_block_id,int ndatas)146 XLogEnsureRecordSpace(int max_block_id, int ndatas)
147 {
148 int nbuffers;
149
150 /*
151 * This must be called before entering a critical section, because
152 * allocating memory inside a critical section can fail. repalloc() will
153 * check the same, but better to check it here too so that we fail
154 * consistently even if the arrays happen to be large enough already.
155 */
156 Assert(CritSectionCount == 0);
157
158 /* the minimum values can't be decreased */
159 if (max_block_id < XLR_NORMAL_MAX_BLOCK_ID)
160 max_block_id = XLR_NORMAL_MAX_BLOCK_ID;
161 if (ndatas < XLR_NORMAL_RDATAS)
162 ndatas = XLR_NORMAL_RDATAS;
163
164 if (max_block_id > XLR_MAX_BLOCK_ID)
165 elog(ERROR, "maximum number of WAL record block references exceeded");
166 nbuffers = max_block_id + 1;
167
168 if (nbuffers > max_registered_buffers)
169 {
170 registered_buffers = (registered_buffer *)
171 repalloc(registered_buffers, sizeof(registered_buffer) * nbuffers);
172
173 /*
174 * At least the padding bytes in the structs must be zeroed, because
175 * they are included in WAL data, but initialize it all for tidiness.
176 */
177 MemSet(®istered_buffers[max_registered_buffers], 0,
178 (nbuffers - max_registered_buffers) * sizeof(registered_buffer));
179 max_registered_buffers = nbuffers;
180 }
181
182 if (ndatas > max_rdatas)
183 {
184 rdatas = (XLogRecData *) repalloc(rdatas, sizeof(XLogRecData) * ndatas);
185 max_rdatas = ndatas;
186 }
187 }
188
189 /*
190 * Reset WAL record construction buffers.
191 */
192 void
XLogResetInsertion(void)193 XLogResetInsertion(void)
194 {
195 int i;
196
197 for (i = 0; i < max_registered_block_id; i++)
198 registered_buffers[i].in_use = false;
199
200 num_rdatas = 0;
201 max_registered_block_id = 0;
202 mainrdata_len = 0;
203 mainrdata_last = (XLogRecData *) &mainrdata_head;
204 include_origin = false;
205 begininsert_called = false;
206 }
207
208 /*
209 * Register a reference to a buffer with the WAL record being constructed.
210 * This must be called for every page that the WAL-logged operation modifies.
211 */
212 void
XLogRegisterBuffer(uint8 block_id,Buffer buffer,uint8 flags)213 XLogRegisterBuffer(uint8 block_id, Buffer buffer, uint8 flags)
214 {
215 registered_buffer *regbuf;
216
217 /* NO_IMAGE doesn't make sense with FORCE_IMAGE */
218 Assert(!((flags & REGBUF_FORCE_IMAGE) && (flags & (REGBUF_NO_IMAGE))));
219 Assert(begininsert_called);
220
221 if (block_id >= max_registered_block_id)
222 {
223 if (block_id >= max_registered_buffers)
224 elog(ERROR, "too many registered buffers");
225 max_registered_block_id = block_id + 1;
226 }
227
228 regbuf = ®istered_buffers[block_id];
229
230 BufferGetTag(buffer, ®buf->rnode, ®buf->forkno, ®buf->block);
231 regbuf->page = BufferGetPage(buffer);
232 regbuf->flags = flags;
233 regbuf->rdata_tail = (XLogRecData *) ®buf->rdata_head;
234 regbuf->rdata_len = 0;
235
236 /*
237 * Check that this page hasn't already been registered with some other
238 * block_id.
239 */
240 #ifdef USE_ASSERT_CHECKING
241 {
242 int i;
243
244 for (i = 0; i < max_registered_block_id; i++)
245 {
246 registered_buffer *regbuf_old = ®istered_buffers[i];
247
248 if (i == block_id || !regbuf_old->in_use)
249 continue;
250
251 Assert(!RelFileNodeEquals(regbuf_old->rnode, regbuf->rnode) ||
252 regbuf_old->forkno != regbuf->forkno ||
253 regbuf_old->block != regbuf->block);
254 }
255 }
256 #endif
257
258 regbuf->in_use = true;
259 }
260
261 /*
262 * Like XLogRegisterBuffer, but for registering a block that's not in the
263 * shared buffer pool (i.e. when you don't have a Buffer for it).
264 */
265 void
XLogRegisterBlock(uint8 block_id,RelFileNode * rnode,ForkNumber forknum,BlockNumber blknum,Page page,uint8 flags)266 XLogRegisterBlock(uint8 block_id, RelFileNode *rnode, ForkNumber forknum,
267 BlockNumber blknum, Page page, uint8 flags)
268 {
269 registered_buffer *regbuf;
270
271 /* This is currently only used to WAL-log a full-page image of a page */
272 Assert(flags & REGBUF_FORCE_IMAGE);
273 Assert(begininsert_called);
274
275 if (block_id >= max_registered_block_id)
276 max_registered_block_id = block_id + 1;
277
278 if (block_id >= max_registered_buffers)
279 elog(ERROR, "too many registered buffers");
280
281 regbuf = ®istered_buffers[block_id];
282
283 regbuf->rnode = *rnode;
284 regbuf->forkno = forknum;
285 regbuf->block = blknum;
286 regbuf->page = page;
287 regbuf->flags = flags;
288 regbuf->rdata_tail = (XLogRecData *) ®buf->rdata_head;
289 regbuf->rdata_len = 0;
290
291 /*
292 * Check that this page hasn't already been registered with some other
293 * block_id.
294 */
295 #ifdef USE_ASSERT_CHECKING
296 {
297 int i;
298
299 for (i = 0; i < max_registered_block_id; i++)
300 {
301 registered_buffer *regbuf_old = ®istered_buffers[i];
302
303 if (i == block_id || !regbuf_old->in_use)
304 continue;
305
306 Assert(!RelFileNodeEquals(regbuf_old->rnode, regbuf->rnode) ||
307 regbuf_old->forkno != regbuf->forkno ||
308 regbuf_old->block != regbuf->block);
309 }
310 }
311 #endif
312
313 regbuf->in_use = true;
314 }
315
316 /*
317 * Add data to the WAL record that's being constructed.
318 *
319 * The data is appended to the "main chunk", available at replay with
320 * XLogRecGetData().
321 */
322 void
XLogRegisterData(char * data,int len)323 XLogRegisterData(char *data, int len)
324 {
325 XLogRecData *rdata;
326
327 Assert(begininsert_called);
328
329 if (num_rdatas >= max_rdatas)
330 elog(ERROR, "too much WAL data");
331 rdata = &rdatas[num_rdatas++];
332
333 rdata->data = data;
334 rdata->len = len;
335
336 /*
337 * we use the mainrdata_last pointer to track the end of the chain, so no
338 * need to clear 'next' here.
339 */
340
341 mainrdata_last->next = rdata;
342 mainrdata_last = rdata;
343
344 mainrdata_len += len;
345 }
346
347 /*
348 * Add buffer-specific data to the WAL record that's being constructed.
349 *
350 * Block_id must reference a block previously registered with
351 * XLogRegisterBuffer(). If this is called more than once for the same
352 * block_id, the data is appended.
353 *
354 * The maximum amount of data that can be registered per block is 65535
355 * bytes. That should be plenty; if you need more than BLCKSZ bytes to
356 * reconstruct the changes to the page, you might as well just log a full
357 * copy of it. (the "main data" that's not associated with a block is not
358 * limited)
359 */
360 void
XLogRegisterBufData(uint8 block_id,char * data,int len)361 XLogRegisterBufData(uint8 block_id, char *data, int len)
362 {
363 registered_buffer *regbuf;
364 XLogRecData *rdata;
365
366 Assert(begininsert_called);
367
368 /* find the registered buffer struct */
369 regbuf = ®istered_buffers[block_id];
370 if (!regbuf->in_use)
371 elog(ERROR, "no block with id %d registered with WAL insertion",
372 block_id);
373
374 if (num_rdatas >= max_rdatas)
375 elog(ERROR, "too much WAL data");
376 rdata = &rdatas[num_rdatas++];
377
378 rdata->data = data;
379 rdata->len = len;
380
381 regbuf->rdata_tail->next = rdata;
382 regbuf->rdata_tail = rdata;
383 regbuf->rdata_len += len;
384 }
385
386 /*
387 * Should this record include the replication origin if one is set up?
388 */
389 void
XLogIncludeOrigin(void)390 XLogIncludeOrigin(void)
391 {
392 Assert(begininsert_called);
393 include_origin = true;
394 }
395
396 /*
397 * Insert an XLOG record having the specified RMID and info bytes, with the
398 * body of the record being the data and buffer references registered earlier
399 * with XLogRegister* calls.
400 *
401 * Returns XLOG pointer to end of record (beginning of next record).
402 * This can be used as LSN for data pages affected by the logged action.
403 * (LSN is the XLOG point up to which the XLOG must be flushed to disk
404 * before the data page can be written out. This implements the basic
405 * WAL rule "write the log before the data".)
406 */
407 XLogRecPtr
XLogInsert(RmgrId rmid,uint8 info)408 XLogInsert(RmgrId rmid, uint8 info)
409 {
410 XLogRecPtr EndPos;
411
412 /* XLogBeginInsert() must have been called. */
413 if (!begininsert_called)
414 elog(ERROR, "XLogBeginInsert was not called");
415
416 /*
417 * The caller can set rmgr bits and XLR_SPECIAL_REL_UPDATE; the rest are
418 * reserved for use by me.
419 */
420 if ((info & ~(XLR_RMGR_INFO_MASK | XLR_SPECIAL_REL_UPDATE)) != 0)
421 elog(PANIC, "invalid xlog info mask %02X", info);
422
423 TRACE_POSTGRESQL_XLOG_INSERT(rmid, info);
424
425 /*
426 * In bootstrap mode, we don't actually log anything but XLOG resources;
427 * return a phony record pointer.
428 */
429 if (IsBootstrapProcessingMode() && rmid != RM_XLOG_ID)
430 {
431 XLogResetInsertion();
432 EndPos = SizeOfXLogLongPHD; /* start of 1st chkpt record */
433 return EndPos;
434 }
435
436 do
437 {
438 XLogRecPtr RedoRecPtr;
439 bool doPageWrites;
440 XLogRecPtr fpw_lsn;
441 XLogRecData *rdt;
442
443 /*
444 * Get values needed to decide whether to do full-page writes. Since
445 * we don't yet have an insertion lock, these could change under us,
446 * but XLogInsertRecord will recheck them once it has a lock.
447 */
448 GetFullPageWriteInfo(&RedoRecPtr, &doPageWrites);
449
450 rdt = XLogRecordAssemble(rmid, info, RedoRecPtr, doPageWrites,
451 &fpw_lsn);
452
453 EndPos = XLogInsertRecord(rdt, fpw_lsn);
454 } while (EndPos == InvalidXLogRecPtr);
455
456 XLogResetInsertion();
457
458 return EndPos;
459 }
460
461 /*
462 * Assemble a WAL record from the registered data and buffers into an
463 * XLogRecData chain, ready for insertion with XLogInsertRecord().
464 *
465 * The record header fields are filled in, except for the xl_prev field. The
466 * calculated CRC does not include the record header yet.
467 *
468 * If there are any registered buffers, and a full-page image was not taken
469 * of all of them, *fpw_lsn is set to the lowest LSN among such pages. This
470 * signals that the assembled record is only good for insertion on the
471 * assumption that the RedoRecPtr and doPageWrites values were up-to-date.
472 */
473 static XLogRecData *
XLogRecordAssemble(RmgrId rmid,uint8 info,XLogRecPtr RedoRecPtr,bool doPageWrites,XLogRecPtr * fpw_lsn)474 XLogRecordAssemble(RmgrId rmid, uint8 info,
475 XLogRecPtr RedoRecPtr, bool doPageWrites,
476 XLogRecPtr *fpw_lsn)
477 {
478 XLogRecData *rdt;
479 uint32 total_len = 0;
480 int block_id;
481 pg_crc32c rdata_crc;
482 registered_buffer *prev_regbuf = NULL;
483 XLogRecData *rdt_datas_last;
484 XLogRecord *rechdr;
485 char *scratch = hdr_scratch;
486
487 /*
488 * Note: this function can be called multiple times for the same record.
489 * All the modifications we do to the rdata chains below must handle that.
490 */
491
492 /* The record begins with the fixed-size header */
493 rechdr = (XLogRecord *) scratch;
494 scratch += SizeOfXLogRecord;
495
496 hdr_rdt.next = NULL;
497 rdt_datas_last = &hdr_rdt;
498 hdr_rdt.data = hdr_scratch;
499
500 /*
501 * Make an rdata chain containing all the data portions of all block
502 * references. This includes the data for full-page images. Also append
503 * the headers for the block references in the scratch buffer.
504 */
505 *fpw_lsn = InvalidXLogRecPtr;
506 for (block_id = 0; block_id < max_registered_block_id; block_id++)
507 {
508 registered_buffer *regbuf = ®istered_buffers[block_id];
509 bool needs_backup;
510 bool needs_data;
511 XLogRecordBlockHeader bkpb;
512 XLogRecordBlockImageHeader bimg;
513 XLogRecordBlockCompressHeader cbimg = {0};
514 bool samerel;
515 bool is_compressed = false;
516
517 if (!regbuf->in_use)
518 continue;
519
520 /* Determine if this block needs to be backed up */
521 if (regbuf->flags & REGBUF_FORCE_IMAGE)
522 needs_backup = true;
523 else if (regbuf->flags & REGBUF_NO_IMAGE)
524 needs_backup = false;
525 else if (!doPageWrites)
526 needs_backup = false;
527 else
528 {
529 /*
530 * We assume page LSN is first data on *every* page that can be
531 * passed to XLogInsert, whether it has the standard page layout
532 * or not.
533 */
534 XLogRecPtr page_lsn = PageGetLSN(regbuf->page);
535
536 needs_backup = (page_lsn <= RedoRecPtr);
537 if (!needs_backup)
538 {
539 if (*fpw_lsn == InvalidXLogRecPtr || page_lsn < *fpw_lsn)
540 *fpw_lsn = page_lsn;
541 }
542 }
543
544 /* Determine if the buffer data needs to included */
545 if (regbuf->rdata_len == 0)
546 needs_data = false;
547 else if ((regbuf->flags & REGBUF_KEEP_DATA) != 0)
548 needs_data = true;
549 else
550 needs_data = !needs_backup;
551
552 bkpb.id = block_id;
553 bkpb.fork_flags = regbuf->forkno;
554 bkpb.data_length = 0;
555
556 if ((regbuf->flags & REGBUF_WILL_INIT) == REGBUF_WILL_INIT)
557 bkpb.fork_flags |= BKPBLOCK_WILL_INIT;
558
559 if (needs_backup)
560 {
561 Page page = regbuf->page;
562 uint16 compressed_len;
563
564 /*
565 * The page needs to be backed up, so calculate its hole length
566 * and offset.
567 */
568 if (regbuf->flags & REGBUF_STANDARD)
569 {
570 /* Assume we can omit data between pd_lower and pd_upper */
571 uint16 lower = ((PageHeader) page)->pd_lower;
572 uint16 upper = ((PageHeader) page)->pd_upper;
573
574 if (lower >= SizeOfPageHeaderData &&
575 upper > lower &&
576 upper <= BLCKSZ)
577 {
578 bimg.hole_offset = lower;
579 cbimg.hole_length = upper - lower;
580 }
581 else
582 {
583 /* No "hole" to compress out */
584 bimg.hole_offset = 0;
585 cbimg.hole_length = 0;
586 }
587 }
588 else
589 {
590 /* Not a standard page header, don't try to eliminate "hole" */
591 bimg.hole_offset = 0;
592 cbimg.hole_length = 0;
593 }
594
595 /*
596 * Try to compress a block image if wal_compression is enabled
597 */
598 if (wal_compression)
599 {
600 is_compressed =
601 XLogCompressBackupBlock(page, bimg.hole_offset,
602 cbimg.hole_length,
603 regbuf->compressed_page,
604 &compressed_len);
605 }
606
607 /*
608 * Fill in the remaining fields in the XLogRecordBlockHeader
609 * struct
610 */
611 bkpb.fork_flags |= BKPBLOCK_HAS_IMAGE;
612
613 /*
614 * Construct XLogRecData entries for the page content.
615 */
616 rdt_datas_last->next = ®buf->bkp_rdatas[0];
617 rdt_datas_last = rdt_datas_last->next;
618
619 bimg.bimg_info = (cbimg.hole_length == 0) ? 0 : BKPIMAGE_HAS_HOLE;
620
621 if (is_compressed)
622 {
623 bimg.length = compressed_len;
624 bimg.bimg_info |= BKPIMAGE_IS_COMPRESSED;
625
626 rdt_datas_last->data = regbuf->compressed_page;
627 rdt_datas_last->len = compressed_len;
628 }
629 else
630 {
631 bimg.length = BLCKSZ - cbimg.hole_length;
632
633 if (cbimg.hole_length == 0)
634 {
635 rdt_datas_last->data = page;
636 rdt_datas_last->len = BLCKSZ;
637 }
638 else
639 {
640 /* must skip the hole */
641 rdt_datas_last->data = page;
642 rdt_datas_last->len = bimg.hole_offset;
643
644 rdt_datas_last->next = ®buf->bkp_rdatas[1];
645 rdt_datas_last = rdt_datas_last->next;
646
647 rdt_datas_last->data =
648 page + (bimg.hole_offset + cbimg.hole_length);
649 rdt_datas_last->len =
650 BLCKSZ - (bimg.hole_offset + cbimg.hole_length);
651 }
652 }
653
654 total_len += bimg.length;
655 }
656
657 if (needs_data)
658 {
659 /*
660 * Link the caller-supplied rdata chain for this buffer to the
661 * overall list.
662 */
663 bkpb.fork_flags |= BKPBLOCK_HAS_DATA;
664 bkpb.data_length = regbuf->rdata_len;
665 total_len += regbuf->rdata_len;
666
667 rdt_datas_last->next = regbuf->rdata_head;
668 rdt_datas_last = regbuf->rdata_tail;
669 }
670
671 if (prev_regbuf && RelFileNodeEquals(regbuf->rnode, prev_regbuf->rnode))
672 {
673 samerel = true;
674 bkpb.fork_flags |= BKPBLOCK_SAME_REL;
675 }
676 else
677 samerel = false;
678 prev_regbuf = regbuf;
679
680 /* Ok, copy the header to the scratch buffer */
681 memcpy(scratch, &bkpb, SizeOfXLogRecordBlockHeader);
682 scratch += SizeOfXLogRecordBlockHeader;
683 if (needs_backup)
684 {
685 memcpy(scratch, &bimg, SizeOfXLogRecordBlockImageHeader);
686 scratch += SizeOfXLogRecordBlockImageHeader;
687 if (cbimg.hole_length != 0 && is_compressed)
688 {
689 memcpy(scratch, &cbimg,
690 SizeOfXLogRecordBlockCompressHeader);
691 scratch += SizeOfXLogRecordBlockCompressHeader;
692 }
693 }
694 if (!samerel)
695 {
696 memcpy(scratch, ®buf->rnode, sizeof(RelFileNode));
697 scratch += sizeof(RelFileNode);
698 }
699 memcpy(scratch, ®buf->block, sizeof(BlockNumber));
700 scratch += sizeof(BlockNumber);
701 }
702
703 /* followed by the record's origin, if any */
704 if (include_origin && replorigin_session_origin != InvalidRepOriginId)
705 {
706 *(scratch++) = (char) XLR_BLOCK_ID_ORIGIN;
707 memcpy(scratch, &replorigin_session_origin, sizeof(replorigin_session_origin));
708 scratch += sizeof(replorigin_session_origin);
709 }
710
711 /* followed by main data, if any */
712 if (mainrdata_len > 0)
713 {
714 if (mainrdata_len > 255)
715 {
716 *(scratch++) = (char) XLR_BLOCK_ID_DATA_LONG;
717 memcpy(scratch, &mainrdata_len, sizeof(uint32));
718 scratch += sizeof(uint32);
719 }
720 else
721 {
722 *(scratch++) = (char) XLR_BLOCK_ID_DATA_SHORT;
723 *(scratch++) = (uint8) mainrdata_len;
724 }
725 rdt_datas_last->next = mainrdata_head;
726 rdt_datas_last = mainrdata_last;
727 total_len += mainrdata_len;
728 }
729 rdt_datas_last->next = NULL;
730
731 hdr_rdt.len = (scratch - hdr_scratch);
732 total_len += hdr_rdt.len;
733
734 /*
735 * Calculate CRC of the data
736 *
737 * Note that the record header isn't added into the CRC initially since we
738 * don't know the prev-link yet. Thus, the CRC will represent the CRC of
739 * the whole record in the order: rdata, then backup blocks, then record
740 * header.
741 */
742 INIT_CRC32C(rdata_crc);
743 COMP_CRC32C(rdata_crc, hdr_scratch + SizeOfXLogRecord, hdr_rdt.len - SizeOfXLogRecord);
744 for (rdt = hdr_rdt.next; rdt != NULL; rdt = rdt->next)
745 COMP_CRC32C(rdata_crc, rdt->data, rdt->len);
746
747 /*
748 * Fill in the fields in the record header. Prev-link is filled in later,
749 * once we know where in the WAL the record will be inserted. The CRC does
750 * not include the record header yet.
751 */
752 rechdr->xl_xid = GetCurrentTransactionIdIfAny();
753 rechdr->xl_tot_len = total_len;
754 rechdr->xl_info = info;
755 rechdr->xl_rmid = rmid;
756 rechdr->xl_prev = InvalidXLogRecPtr;
757 rechdr->xl_crc = rdata_crc;
758
759 return &hdr_rdt;
760 }
761
762 /*
763 * Create a compressed version of a backup block image.
764 *
765 * Returns FALSE if compression fails (i.e., compressed result is actually
766 * bigger than original). Otherwise, returns TRUE and sets 'dlen' to
767 * the length of compressed block image.
768 */
769 static bool
XLogCompressBackupBlock(char * page,uint16 hole_offset,uint16 hole_length,char * dest,uint16 * dlen)770 XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
771 char *dest, uint16 *dlen)
772 {
773 int32 orig_len = BLCKSZ - hole_length;
774 int32 len;
775 int32 extra_bytes = 0;
776 char *source;
777 PGAlignedBlock tmp;
778
779 if (hole_length != 0)
780 {
781 /* must skip the hole */
782 source = tmp.data;
783 memcpy(source, page, hole_offset);
784 memcpy(source + hole_offset,
785 page + (hole_offset + hole_length),
786 BLCKSZ - (hole_length + hole_offset));
787
788 /*
789 * Extra data needs to be stored in WAL record for the compressed
790 * version of block image if the hole exists.
791 */
792 extra_bytes = SizeOfXLogRecordBlockCompressHeader;
793 }
794 else
795 source = page;
796
797 /*
798 * We recheck the actual size even if pglz_compress() reports success and
799 * see if the number of bytes saved by compression is larger than the
800 * length of extra data needed for the compressed version of block image.
801 */
802 len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
803 if (len >= 0 &&
804 len + extra_bytes < orig_len)
805 {
806 *dlen = (uint16) len; /* successful compression */
807 return true;
808 }
809 return false;
810 }
811
812 /*
813 * Determine whether the buffer referenced has to be backed up.
814 *
815 * Since we don't yet have the insert lock, fullPageWrites and forcePageWrites
816 * could change later, so the result should be used for optimization purposes
817 * only.
818 */
819 bool
XLogCheckBufferNeedsBackup(Buffer buffer)820 XLogCheckBufferNeedsBackup(Buffer buffer)
821 {
822 XLogRecPtr RedoRecPtr;
823 bool doPageWrites;
824 Page page;
825
826 GetFullPageWriteInfo(&RedoRecPtr, &doPageWrites);
827
828 page = BufferGetPage(buffer);
829
830 if (doPageWrites && PageGetLSN(page) <= RedoRecPtr)
831 return true; /* buffer requires backup */
832
833 return false; /* buffer does not need to be backed up */
834 }
835
836 /*
837 * Write a backup block if needed when we are setting a hint. Note that
838 * this may be called for a variety of page types, not just heaps.
839 *
840 * Callable while holding just share lock on the buffer content.
841 *
842 * We can't use the plain backup block mechanism since that relies on the
843 * Buffer being exclusively locked. Since some modifications (setting LSN, hint
844 * bits) are allowed in a sharelocked buffer that can lead to wal checksum
845 * failures. So instead we copy the page and insert the copied data as normal
846 * record data.
847 *
848 * We only need to do something if page has not yet been full page written in
849 * this checkpoint round. The LSN of the inserted wal record is returned if we
850 * had to write, InvalidXLogRecPtr otherwise.
851 *
852 * It is possible that multiple concurrent backends could attempt to write WAL
853 * records. In that case, multiple copies of the same block would be recorded
854 * in separate WAL records by different backends, though that is still OK from
855 * a correctness perspective.
856 */
857 XLogRecPtr
XLogSaveBufferForHint(Buffer buffer,bool buffer_std)858 XLogSaveBufferForHint(Buffer buffer, bool buffer_std)
859 {
860 XLogRecPtr recptr = InvalidXLogRecPtr;
861 XLogRecPtr lsn;
862 XLogRecPtr RedoRecPtr;
863
864 /*
865 * Ensure no checkpoint can change our view of RedoRecPtr.
866 */
867 Assert(MyPgXact->delayChkpt);
868
869 /*
870 * Update RedoRecPtr so that we can make the right decision
871 */
872 RedoRecPtr = GetRedoRecPtr();
873
874 /*
875 * We assume page LSN is first data on *every* page that can be passed to
876 * XLogInsert, whether it has the standard page layout or not. Since we're
877 * only holding a share-lock on the page, we must take the buffer header
878 * lock when we look at the LSN.
879 */
880 lsn = BufferGetLSNAtomic(buffer);
881
882 if (lsn <= RedoRecPtr)
883 {
884 int flags;
885 PGAlignedBlock copied_buffer;
886 char *origdata = (char *) BufferGetBlock(buffer);
887 RelFileNode rnode;
888 ForkNumber forkno;
889 BlockNumber blkno;
890
891 /*
892 * Copy buffer so we don't have to worry about concurrent hint bit or
893 * lsn updates. We assume pd_lower/upper cannot be changed without an
894 * exclusive lock, so the contents bkp are not racy.
895 */
896 if (buffer_std)
897 {
898 /* Assume we can omit data between pd_lower and pd_upper */
899 Page page = BufferGetPage(buffer);
900 uint16 lower = ((PageHeader) page)->pd_lower;
901 uint16 upper = ((PageHeader) page)->pd_upper;
902
903 memcpy(copied_buffer.data, origdata, lower);
904 memcpy(copied_buffer.data + upper, origdata + upper, BLCKSZ - upper);
905 }
906 else
907 memcpy(copied_buffer.data, origdata, BLCKSZ);
908
909 XLogBeginInsert();
910
911 flags = REGBUF_FORCE_IMAGE;
912 if (buffer_std)
913 flags |= REGBUF_STANDARD;
914
915 BufferGetTag(buffer, &rnode, &forkno, &blkno);
916 XLogRegisterBlock(0, &rnode, forkno, blkno, copied_buffer.data, flags);
917
918 recptr = XLogInsert(RM_XLOG_ID, XLOG_FPI_FOR_HINT);
919 }
920
921 return recptr;
922 }
923
924 /*
925 * Write a WAL record containing a full image of a page. Caller is responsible
926 * for writing the page to disk after calling this routine.
927 *
928 * Note: If you're using this function, you should be building pages in private
929 * memory and writing them directly to smgr. If you're using buffers, call
930 * log_newpage_buffer instead.
931 *
932 * If the page follows the standard page layout, with a PageHeader and unused
933 * space between pd_lower and pd_upper, set 'page_std' to TRUE. That allows
934 * the unused space to be left out from the WAL record, making it smaller.
935 */
936 XLogRecPtr
log_newpage(RelFileNode * rnode,ForkNumber forkNum,BlockNumber blkno,Page page,bool page_std)937 log_newpage(RelFileNode *rnode, ForkNumber forkNum, BlockNumber blkno,
938 Page page, bool page_std)
939 {
940 int flags;
941 XLogRecPtr recptr;
942
943 flags = REGBUF_FORCE_IMAGE;
944 if (page_std)
945 flags |= REGBUF_STANDARD;
946
947 XLogBeginInsert();
948 XLogRegisterBlock(0, rnode, forkNum, blkno, page, flags);
949 recptr = XLogInsert(RM_XLOG_ID, XLOG_FPI);
950
951 /*
952 * The page may be uninitialized. If so, we can't set the LSN because that
953 * would corrupt the page.
954 */
955 if (!PageIsNew(page))
956 {
957 PageSetLSN(page, recptr);
958 }
959
960 return recptr;
961 }
962
963 /*
964 * Write a WAL record containing a full image of a page.
965 *
966 * Caller should initialize the buffer and mark it dirty before calling this
967 * function. This function will set the page LSN.
968 *
969 * If the page follows the standard page layout, with a PageHeader and unused
970 * space between pd_lower and pd_upper, set 'page_std' to TRUE. That allows
971 * the unused space to be left out from the WAL record, making it smaller.
972 */
973 XLogRecPtr
log_newpage_buffer(Buffer buffer,bool page_std)974 log_newpage_buffer(Buffer buffer, bool page_std)
975 {
976 Page page = BufferGetPage(buffer);
977 RelFileNode rnode;
978 ForkNumber forkNum;
979 BlockNumber blkno;
980
981 /* Shared buffers should be modified in a critical section. */
982 Assert(CritSectionCount > 0);
983
984 BufferGetTag(buffer, &rnode, &forkNum, &blkno);
985
986 return log_newpage(&rnode, forkNum, blkno, page, page_std);
987 }
988
989 /*
990 * WAL-log a range of blocks in a relation.
991 *
992 * An image of all pages with block numbers 'startblk' <= X < 'endblk' is
993 * written to the WAL. If the range is large, this is done in multiple WAL
994 * records.
995 *
996 * If all page follows the standard page layout, with a PageHeader and unused
997 * space between pd_lower and pd_upper, set 'page_std' to true. That allows
998 * the unused space to be left out from the WAL records, making them smaller.
999 *
1000 * NOTE: This function acquires exclusive-locks on the pages. Typically, this
1001 * is used on a newly-built relation, and the caller is holding a
1002 * AccessExclusiveLock on it, so no other backend can be accessing it at the
1003 * same time. If that's not the case, you must ensure that this does not
1004 * cause a deadlock through some other means.
1005 */
1006 void
log_newpage_range(Relation rel,ForkNumber forkNum,BlockNumber startblk,BlockNumber endblk,bool page_std)1007 log_newpage_range(Relation rel, ForkNumber forkNum,
1008 BlockNumber startblk, BlockNumber endblk,
1009 bool page_std)
1010 {
1011 int flags;
1012 BlockNumber blkno;
1013
1014 flags = REGBUF_FORCE_IMAGE;
1015 if (page_std)
1016 flags |= REGBUF_STANDARD;
1017
1018 /*
1019 * Iterate over all the pages in the range. They are collected into
1020 * batches of XLR_MAX_BLOCK_ID pages, and a single WAL-record is written
1021 * for each batch.
1022 */
1023 XLogEnsureRecordSpace(XLR_MAX_BLOCK_ID - 1, 0);
1024
1025 blkno = startblk;
1026 while (blkno < endblk)
1027 {
1028 Buffer bufpack[XLR_MAX_BLOCK_ID];
1029 XLogRecPtr recptr;
1030 int nbufs;
1031 int i;
1032
1033 CHECK_FOR_INTERRUPTS();
1034
1035 /* Collect a batch of blocks. */
1036 nbufs = 0;
1037 while (nbufs < XLR_MAX_BLOCK_ID && blkno < endblk)
1038 {
1039 Buffer buf = ReadBufferExtended(rel, forkNum, blkno,
1040 RBM_NORMAL, NULL);
1041
1042 LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
1043
1044 /*
1045 * Completely empty pages are not WAL-logged. Writing a WAL record
1046 * would change the LSN, and we don't want that. We want the page
1047 * to stay empty.
1048 */
1049 if (!PageIsNew(BufferGetPage(buf)))
1050 bufpack[nbufs++] = buf;
1051 else
1052 UnlockReleaseBuffer(buf);
1053 blkno++;
1054 }
1055
1056 /* Write WAL record for this batch. */
1057 XLogBeginInsert();
1058
1059 START_CRIT_SECTION();
1060 for (i = 0; i < nbufs; i++)
1061 {
1062 XLogRegisterBuffer(i, bufpack[i], flags);
1063 MarkBufferDirty(bufpack[i]);
1064 }
1065
1066 recptr = XLogInsert(RM_XLOG_ID, XLOG_FPI_MULTI);
1067
1068 for (i = 0; i < nbufs; i++)
1069 {
1070 PageSetLSN(BufferGetPage(bufpack[i]), recptr);
1071 UnlockReleaseBuffer(bufpack[i]);
1072 }
1073 END_CRIT_SECTION();
1074 }
1075 }
1076
1077 /*
1078 * Allocate working buffers needed for WAL record construction.
1079 */
1080 void
InitXLogInsert(void)1081 InitXLogInsert(void)
1082 {
1083 /* Initialize the working areas */
1084 if (xloginsert_cxt == NULL)
1085 {
1086 xloginsert_cxt = AllocSetContextCreate(TopMemoryContext,
1087 "WAL record construction",
1088 ALLOCSET_DEFAULT_SIZES);
1089 }
1090
1091 if (registered_buffers == NULL)
1092 {
1093 registered_buffers = (registered_buffer *)
1094 MemoryContextAllocZero(xloginsert_cxt,
1095 sizeof(registered_buffer) * (XLR_NORMAL_MAX_BLOCK_ID + 1));
1096 max_registered_buffers = XLR_NORMAL_MAX_BLOCK_ID + 1;
1097 }
1098 if (rdatas == NULL)
1099 {
1100 rdatas = MemoryContextAlloc(xloginsert_cxt,
1101 sizeof(XLogRecData) * XLR_NORMAL_RDATAS);
1102 max_rdatas = XLR_NORMAL_RDATAS;
1103 }
1104
1105 /*
1106 * Allocate a buffer to hold the header information for a WAL record.
1107 */
1108 if (hdr_scratch == NULL)
1109 hdr_scratch = MemoryContextAllocZero(xloginsert_cxt,
1110 HEADER_SCRATCH_SIZE);
1111 }
1112