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1/*
2 * Copyright (c) 2010 Red Hat, Inc. All Rights Reserved.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License as
6 * published by the Free Software Foundation.
7 *
8 * This program is distributed in the hope that it would be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 * GNU General Public License for more details.
12 *
13 * You should have received a copy of the GNU General Public License
14 * along with this program; if not, write the Free Software Foundation,
15 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
16 */
17
18#include "xfs.h"
19#include "xfs_fs.h"
20#include "xfs_types.h"
21#include "xfs_bit.h"
22#include "xfs_log.h"
23#include "xfs_inum.h"
24#include "xfs_trans.h"
25#include "xfs_trans_priv.h"
26#include "xfs_log_priv.h"
27#include "xfs_sb.h"
28#include "xfs_ag.h"
29#include "xfs_mount.h"
30#include "xfs_error.h"
31#include "xfs_alloc.h"
32#include "xfs_discard.h"
33
34/*
35 * Perform initial CIL structure initialisation. If the CIL is not
36 * enabled in this filesystem, ensure the log->l_cilp is null so
37 * we can check this conditional to determine if we are doing delayed
38 * logging or not.
39 */
40int
41xlog_cil_init(
42 struct log *log)
43{
44 struct xfs_cil *cil;
45 struct xfs_cil_ctx *ctx;
46
47 log->l_cilp = NULL;
48 if (!(log->l_mp->m_flags & XFS_MOUNT_DELAYLOG))
49 return 0;
50
51 cil = kmem_zalloc(sizeof(*cil), KM_SLEEP|KM_MAYFAIL);
52 if (!cil)
53 return ENOMEM;
54
55 ctx = kmem_zalloc(sizeof(*ctx), KM_SLEEP|KM_MAYFAIL);
56 if (!ctx) {
57 kmem_free(cil);
58 return ENOMEM;
59 }
60
61 INIT_LIST_HEAD(&cil->xc_cil);
62 INIT_LIST_HEAD(&cil->xc_committing);
63 spin_lock_init(&cil->xc_cil_lock);
64 init_rwsem(&cil->xc_ctx_lock);
65 init_waitqueue_head(&cil->xc_commit_wait);
66
67 INIT_LIST_HEAD(&ctx->committing);
68 INIT_LIST_HEAD(&ctx->busy_extents);
69 ctx->sequence = 1;
70 ctx->cil = cil;
71 cil->xc_ctx = ctx;
72 cil->xc_current_sequence = ctx->sequence;
73
74 cil->xc_log = log;
75 log->l_cilp = cil;
76 return 0;
77}
78
79void
80xlog_cil_destroy(
81 struct log *log)
82{
83 if (!log->l_cilp)
84 return;
85
86 if (log->l_cilp->xc_ctx) {
87 if (log->l_cilp->xc_ctx->ticket)
88 xfs_log_ticket_put(log->l_cilp->xc_ctx->ticket);
89 kmem_free(log->l_cilp->xc_ctx);
90 }
91
92 ASSERT(list_empty(&log->l_cilp->xc_cil));
93 kmem_free(log->l_cilp);
94}
95
96/*
97 * Allocate a new ticket. Failing to get a new ticket makes it really hard to
98 * recover, so we don't allow failure here. Also, we allocate in a context that
99 * we don't want to be issuing transactions from, so we need to tell the
100 * allocation code this as well.
101 *
102 * We don't reserve any space for the ticket - we are going to steal whatever
103 * space we require from transactions as they commit. To ensure we reserve all
104 * the space required, we need to set the current reservation of the ticket to
105 * zero so that we know to steal the initial transaction overhead from the
106 * first transaction commit.
107 */
108static struct xlog_ticket *
109xlog_cil_ticket_alloc(
110 struct log *log)
111{
112 struct xlog_ticket *tic;
113
114 tic = xlog_ticket_alloc(log, 0, 1, XFS_TRANSACTION, 0,
115 KM_SLEEP|KM_NOFS);
116 tic->t_trans_type = XFS_TRANS_CHECKPOINT;
117
118 /*
119 * set the current reservation to zero so we know to steal the basic
120 * transaction overhead reservation from the first transaction commit.
121 */
122 tic->t_curr_res = 0;
123 return tic;
124}
125
126/*
127 * After the first stage of log recovery is done, we know where the head and
128 * tail of the log are. We need this log initialisation done before we can
129 * initialise the first CIL checkpoint context.
130 *
131 * Here we allocate a log ticket to track space usage during a CIL push. This
132 * ticket is passed to xlog_write() directly so that we don't slowly leak log
133 * space by failing to account for space used by log headers and additional
134 * region headers for split regions.
135 */
136void
137xlog_cil_init_post_recovery(
138 struct log *log)
139{
140 if (!log->l_cilp)
141 return;
142
143 log->l_cilp->xc_ctx->ticket = xlog_cil_ticket_alloc(log);
144 log->l_cilp->xc_ctx->sequence = 1;
145 log->l_cilp->xc_ctx->commit_lsn = xlog_assign_lsn(log->l_curr_cycle,
146 log->l_curr_block);
147}
148
149/*
150 * Format log item into a flat buffers
151 *
152 * For delayed logging, we need to hold a formatted buffer containing all the
153 * changes on the log item. This enables us to relog the item in memory and
154 * write it out asynchronously without needing to relock the object that was
155 * modified at the time it gets written into the iclog.
156 *
157 * This function builds a vector for the changes in each log item in the
158 * transaction. It then works out the length of the buffer needed for each log
159 * item, allocates them and formats the vector for the item into the buffer.
160 * The buffer is then attached to the log item are then inserted into the
161 * Committed Item List for tracking until the next checkpoint is written out.
162 *
163 * We don't set up region headers during this process; we simply copy the
164 * regions into the flat buffer. We can do this because we still have to do a
165 * formatting step to write the regions into the iclog buffer. Writing the
166 * ophdrs during the iclog write means that we can support splitting large
167 * regions across iclog boundares without needing a change in the format of the
168 * item/region encapsulation.
169 *
170 * Hence what we need to do now is change the rewrite the vector array to point
171 * to the copied region inside the buffer we just allocated. This allows us to
172 * format the regions into the iclog as though they are being formatted
173 * directly out of the objects themselves.
174 */
175static void
176xlog_cil_format_items(
177 struct log *log,
178 struct xfs_log_vec *log_vector)
179{
180 struct xfs_log_vec *lv;
181
182 ASSERT(log_vector);
183 for (lv = log_vector; lv; lv = lv->lv_next) {
184 void *ptr;
185 int index;
186 int len = 0;
187
188 /* build the vector array and calculate it's length */
189 IOP_FORMAT(lv->lv_item, lv->lv_iovecp);
190 for (index = 0; index < lv->lv_niovecs; index++)
191 len += lv->lv_iovecp[index].i_len;
192
193 lv->lv_buf_len = len;
194 lv->lv_buf = kmem_alloc(lv->lv_buf_len, KM_SLEEP|KM_NOFS);
195 ptr = lv->lv_buf;
196
197 for (index = 0; index < lv->lv_niovecs; index++) {
198 struct xfs_log_iovec *vec = &lv->lv_iovecp[index];
199
200 memcpy(ptr, vec->i_addr, vec->i_len);
201 vec->i_addr = ptr;
202 ptr += vec->i_len;
203 }
204 ASSERT(ptr == lv->lv_buf + lv->lv_buf_len);
205 }
206}
207
208/*
209 * Prepare the log item for insertion into the CIL. Calculate the difference in
210 * log space and vectors it will consume, and if it is a new item pin it as
211 * well.
212 */
213STATIC void
214xfs_cil_prepare_item(
215 struct log *log,
216 struct xfs_log_vec *lv,
217 int *len,
218 int *diff_iovecs)
219{
220 struct xfs_log_vec *old = lv->lv_item->li_lv;
221
222 if (old) {
223 /* existing lv on log item, space used is a delta */
224 ASSERT(!list_empty(&lv->lv_item->li_cil));
225 ASSERT(old->lv_buf && old->lv_buf_len && old->lv_niovecs);
226
227 *len += lv->lv_buf_len - old->lv_buf_len;
228 *diff_iovecs += lv->lv_niovecs - old->lv_niovecs;
229 kmem_free(old->lv_buf);
230 kmem_free(old);
231 } else {
232 /* new lv, must pin the log item */
233 ASSERT(!lv->lv_item->li_lv);
234 ASSERT(list_empty(&lv->lv_item->li_cil));
235
236 *len += lv->lv_buf_len;
237 *diff_iovecs += lv->lv_niovecs;
238 IOP_PIN(lv->lv_item);
239
240 }
241
242 /* attach new log vector to log item */
243 lv->lv_item->li_lv = lv;
244
245 /*
246 * If this is the first time the item is being committed to the
247 * CIL, store the sequence number on the log item so we can
248 * tell in future commits whether this is the first checkpoint
249 * the item is being committed into.
250 */
251 if (!lv->lv_item->li_seq)
252 lv->lv_item->li_seq = log->l_cilp->xc_ctx->sequence;
253}
254
255/*
256 * Insert the log items into the CIL and calculate the difference in space
257 * consumed by the item. Add the space to the checkpoint ticket and calculate
258 * if the change requires additional log metadata. If it does, take that space
259 * as well. Remove the amount of space we addded to the checkpoint ticket from
260 * the current transaction ticket so that the accounting works out correctly.
261 */
262static void
263xlog_cil_insert_items(
264 struct log *log,
265 struct xfs_log_vec *log_vector,
266 struct xlog_ticket *ticket)
267{
268 struct xfs_cil *cil = log->l_cilp;
269 struct xfs_cil_ctx *ctx = cil->xc_ctx;
270 struct xfs_log_vec *lv;
271 int len = 0;
272 int diff_iovecs = 0;
273 int iclog_space;
274
275 ASSERT(log_vector);
276
277 /*
278 * Do all the accounting aggregation and switching of log vectors
279 * around in a separate loop to the insertion of items into the CIL.
280 * Then we can do a separate loop to update the CIL within a single
281 * lock/unlock pair. This reduces the number of round trips on the CIL
282 * lock from O(nr_logvectors) to O(1) and greatly reduces the overall
283 * hold time for the transaction commit.
284 *
285 * If this is the first time the item is being placed into the CIL in
286 * this context, pin it so it can't be written to disk until the CIL is
287 * flushed to the iclog and the iclog written to disk.
288 *
289 * We can do this safely because the context can't checkpoint until we
290 * are done so it doesn't matter exactly how we update the CIL.
291 */
292 for (lv = log_vector; lv; lv = lv->lv_next)
293 xfs_cil_prepare_item(log, lv, &len, &diff_iovecs);
294
295 /* account for space used by new iovec headers */
296 len += diff_iovecs * sizeof(xlog_op_header_t);
297
298 spin_lock(&cil->xc_cil_lock);
299
300 /* move the items to the tail of the CIL */
301 for (lv = log_vector; lv; lv = lv->lv_next)
302 list_move_tail(&lv->lv_item->li_cil, &cil->xc_cil);
303
304 ctx->nvecs += diff_iovecs;
305
306 /*
307 * Now transfer enough transaction reservation to the context ticket
308 * for the checkpoint. The context ticket is special - the unit
309 * reservation has to grow as well as the current reservation as we
310 * steal from tickets so we can correctly determine the space used
311 * during the transaction commit.
312 */
313 if (ctx->ticket->t_curr_res == 0) {
314 /* first commit in checkpoint, steal the header reservation */
315 ASSERT(ticket->t_curr_res >= ctx->ticket->t_unit_res + len);
316 ctx->ticket->t_curr_res = ctx->ticket->t_unit_res;
317 ticket->t_curr_res -= ctx->ticket->t_unit_res;
318 }
319
320 /* do we need space for more log record headers? */
321 iclog_space = log->l_iclog_size - log->l_iclog_hsize;
322 if (len > 0 && (ctx->space_used / iclog_space !=
323 (ctx->space_used + len) / iclog_space)) {
324 int hdrs;
325
326 hdrs = (len + iclog_space - 1) / iclog_space;
327 /* need to take into account split region headers, too */
328 hdrs *= log->l_iclog_hsize + sizeof(struct xlog_op_header);
329 ctx->ticket->t_unit_res += hdrs;
330 ctx->ticket->t_curr_res += hdrs;
331 ticket->t_curr_res -= hdrs;
332 ASSERT(ticket->t_curr_res >= len);
333 }
334 ticket->t_curr_res -= len;
335 ctx->space_used += len;
336
337 spin_unlock(&cil->xc_cil_lock);
338}
339
340static void
341xlog_cil_free_logvec(
342 struct xfs_log_vec *log_vector)
343{
344 struct xfs_log_vec *lv;
345
346 for (lv = log_vector; lv; ) {
347 struct xfs_log_vec *next = lv->lv_next;
348 kmem_free(lv->lv_buf);
349 kmem_free(lv);
350 lv = next;
351 }
352}
353
354/*
355 * Mark all items committed and clear busy extents. We free the log vector
356 * chains in a separate pass so that we unpin the log items as quickly as
357 * possible.
358 */
359static void
360xlog_cil_committed(
361 void *args,
362 int abort)
363{
364 struct xfs_cil_ctx *ctx = args;
365 struct xfs_mount *mp = ctx->cil->xc_log->l_mp;
366
367 xfs_trans_committed_bulk(ctx->cil->xc_log->l_ailp, ctx->lv_chain,
368 ctx->start_lsn, abort);
369
370 xfs_alloc_busy_sort(&ctx->busy_extents);
371 xfs_alloc_busy_clear(mp, &ctx->busy_extents,
372 (mp->m_flags & XFS_MOUNT_DISCARD) && !abort);
373
374 spin_lock(&ctx->cil->xc_cil_lock);
375 list_del(&ctx->committing);
376 spin_unlock(&ctx->cil->xc_cil_lock);
377
378 xlog_cil_free_logvec(ctx->lv_chain);
379
380 if (!list_empty(&ctx->busy_extents)) {
381 ASSERT(mp->m_flags & XFS_MOUNT_DISCARD);
382
383 xfs_discard_extents(mp, &ctx->busy_extents);
384 xfs_alloc_busy_clear(mp, &ctx->busy_extents, false);
385 }
386
387 kmem_free(ctx);
388}
389
390/*
391 * Push the Committed Item List to the log. If @push_seq flag is zero, then it
392 * is a background flush and so we can chose to ignore it. Otherwise, if the
393 * current sequence is the same as @push_seq we need to do a flush. If
394 * @push_seq is less than the current sequence, then it has already been
395 * flushed and we don't need to do anything - the caller will wait for it to
396 * complete if necessary.
397 *
398 * @push_seq is a value rather than a flag because that allows us to do an
399 * unlocked check of the sequence number for a match. Hence we can allows log
400 * forces to run racily and not issue pushes for the same sequence twice. If we
401 * get a race between multiple pushes for the same sequence they will block on
402 * the first one and then abort, hence avoiding needless pushes.
403 */
404STATIC int
405xlog_cil_push(
406 struct log *log,
407 xfs_lsn_t push_seq)
408{
409 struct xfs_cil *cil = log->l_cilp;
410 struct xfs_log_vec *lv;
411 struct xfs_cil_ctx *ctx;
412 struct xfs_cil_ctx *new_ctx;
413 struct xlog_in_core *commit_iclog;
414 struct xlog_ticket *tic;
415 int num_lv;
416 int num_iovecs;
417 int len;
418 int error = 0;
419 struct xfs_trans_header thdr;
420 struct xfs_log_iovec lhdr;
421 struct xfs_log_vec lvhdr = { NULL };
422 xfs_lsn_t commit_lsn;
423
424 if (!cil)
425 return 0;
426
427 ASSERT(!push_seq || push_seq <= cil->xc_ctx->sequence);
428
429 new_ctx = kmem_zalloc(sizeof(*new_ctx), KM_SLEEP|KM_NOFS);
430 new_ctx->ticket = xlog_cil_ticket_alloc(log);
431
432 /*
433 * Lock out transaction commit, but don't block for background pushes
434 * unless we are well over the CIL space limit. See the definition of
435 * XLOG_CIL_HARD_SPACE_LIMIT() for the full explanation of the logic
436 * used here.
437 */
438 if (!down_write_trylock(&cil->xc_ctx_lock)) {
439 if (!push_seq &&
440 cil->xc_ctx->space_used < XLOG_CIL_HARD_SPACE_LIMIT(log))
441 goto out_free_ticket;
442 down_write(&cil->xc_ctx_lock);
443 }
444 ctx = cil->xc_ctx;
445
446 /* check if we've anything to push */
447 if (list_empty(&cil->xc_cil))
448 goto out_skip;
449
450 /* check for spurious background flush */
451 if (!push_seq && cil->xc_ctx->space_used < XLOG_CIL_SPACE_LIMIT(log))
452 goto out_skip;
453
454 /* check for a previously pushed seqeunce */
455 if (push_seq && push_seq < cil->xc_ctx->sequence)
456 goto out_skip;
457
458 /*
459 * pull all the log vectors off the items in the CIL, and
460 * remove the items from the CIL. We don't need the CIL lock
461 * here because it's only needed on the transaction commit
462 * side which is currently locked out by the flush lock.
463 */
464 lv = NULL;
465 num_lv = 0;
466 num_iovecs = 0;
467 len = 0;
468 while (!list_empty(&cil->xc_cil)) {
469 struct xfs_log_item *item;
470 int i;
471
472 item = list_first_entry(&cil->xc_cil,
473 struct xfs_log_item, li_cil);
474 list_del_init(&item->li_cil);
475 if (!ctx->lv_chain)
476 ctx->lv_chain = item->li_lv;
477 else
478 lv->lv_next = item->li_lv;
479 lv = item->li_lv;
480 item->li_lv = NULL;
481
482 num_lv++;
483 num_iovecs += lv->lv_niovecs;
484 for (i = 0; i < lv->lv_niovecs; i++)
485 len += lv->lv_iovecp[i].i_len;
486 }
487
488 /*
489 * initialise the new context and attach it to the CIL. Then attach
490 * the current context to the CIL committing lsit so it can be found
491 * during log forces to extract the commit lsn of the sequence that
492 * needs to be forced.
493 */
494 INIT_LIST_HEAD(&new_ctx->committing);
495 INIT_LIST_HEAD(&new_ctx->busy_extents);
496 new_ctx->sequence = ctx->sequence + 1;
497 new_ctx->cil = cil;
498 cil->xc_ctx = new_ctx;
499
500 /*
501 * mirror the new sequence into the cil structure so that we can do
502 * unlocked checks against the current sequence in log forces without
503 * risking deferencing a freed context pointer.
504 */
505 cil->xc_current_sequence = new_ctx->sequence;
506
507 /*
508 * The switch is now done, so we can drop the context lock and move out
509 * of a shared context. We can't just go straight to the commit record,
510 * though - we need to synchronise with previous and future commits so
511 * that the commit records are correctly ordered in the log to ensure
512 * that we process items during log IO completion in the correct order.
513 *
514 * For example, if we get an EFI in one checkpoint and the EFD in the
515 * next (e.g. due to log forces), we do not want the checkpoint with
516 * the EFD to be committed before the checkpoint with the EFI. Hence
517 * we must strictly order the commit records of the checkpoints so
518 * that: a) the checkpoint callbacks are attached to the iclogs in the
519 * correct order; and b) the checkpoints are replayed in correct order
520 * in log recovery.
521 *
522 * Hence we need to add this context to the committing context list so
523 * that higher sequences will wait for us to write out a commit record
524 * before they do.
525 */
526 spin_lock(&cil->xc_cil_lock);
527 list_add(&ctx->committing, &cil->xc_committing);
528 spin_unlock(&cil->xc_cil_lock);
529 up_write(&cil->xc_ctx_lock);
530
531 /*
532 * Build a checkpoint transaction header and write it to the log to
533 * begin the transaction. We need to account for the space used by the
534 * transaction header here as it is not accounted for in xlog_write().
535 *
536 * The LSN we need to pass to the log items on transaction commit is
537 * the LSN reported by the first log vector write. If we use the commit
538 * record lsn then we can move the tail beyond the grant write head.
539 */
540 tic = ctx->ticket;
541 thdr.th_magic = XFS_TRANS_HEADER_MAGIC;
542 thdr.th_type = XFS_TRANS_CHECKPOINT;
543 thdr.th_tid = tic->t_tid;
544 thdr.th_num_items = num_iovecs;
545 lhdr.i_addr = &thdr;
546 lhdr.i_len = sizeof(xfs_trans_header_t);
547 lhdr.i_type = XLOG_REG_TYPE_TRANSHDR;
548 tic->t_curr_res -= lhdr.i_len + sizeof(xlog_op_header_t);
549
550 lvhdr.lv_niovecs = 1;
551 lvhdr.lv_iovecp = &lhdr;
552 lvhdr.lv_next = ctx->lv_chain;
553
554 error = xlog_write(log, &lvhdr, tic, &ctx->start_lsn, NULL, 0);
555 if (error)
556 goto out_abort_free_ticket;
557
558 /*
559 * now that we've written the checkpoint into the log, strictly
560 * order the commit records so replay will get them in the right order.
561 */
562restart:
563 spin_lock(&cil->xc_cil_lock);
564 list_for_each_entry(new_ctx, &cil->xc_committing, committing) {
565 /*
566 * Higher sequences will wait for this one so skip them.
567 * Don't wait for own own sequence, either.
568 */
569 if (new_ctx->sequence >= ctx->sequence)
570 continue;
571 if (!new_ctx->commit_lsn) {
572 /*
573 * It is still being pushed! Wait for the push to
574 * complete, then start again from the beginning.
575 */
576 xlog_wait(&cil->xc_commit_wait, &cil->xc_cil_lock);
577 goto restart;
578 }
579 }
580 spin_unlock(&cil->xc_cil_lock);
581
582 /* xfs_log_done always frees the ticket on error. */
583 commit_lsn = xfs_log_done(log->l_mp, tic, &commit_iclog, 0);
584 if (commit_lsn == -1)
585 goto out_abort;
586
587 /* attach all the transactions w/ busy extents to iclog */
588 ctx->log_cb.cb_func = xlog_cil_committed;
589 ctx->log_cb.cb_arg = ctx;
590 error = xfs_log_notify(log->l_mp, commit_iclog, &ctx->log_cb);
591 if (error)
592 goto out_abort;
593
594 /*
595 * now the checkpoint commit is complete and we've attached the
596 * callbacks to the iclog we can assign the commit LSN to the context
597 * and wake up anyone who is waiting for the commit to complete.
598 */
599 spin_lock(&cil->xc_cil_lock);
600 ctx->commit_lsn = commit_lsn;
601 wake_up_all(&cil->xc_commit_wait);
602 spin_unlock(&cil->xc_cil_lock);
603
604 /* release the hounds! */
605 return xfs_log_release_iclog(log->l_mp, commit_iclog);
606
607out_skip:
608 up_write(&cil->xc_ctx_lock);
609out_free_ticket:
610 xfs_log_ticket_put(new_ctx->ticket);
611 kmem_free(new_ctx);
612 return 0;
613
614out_abort_free_ticket:
615 xfs_log_ticket_put(tic);
616out_abort:
617 xlog_cil_committed(ctx, XFS_LI_ABORTED);
618 return XFS_ERROR(EIO);
619}
620
621/*
622 * Commit a transaction with the given vector to the Committed Item List.
623 *
624 * To do this, we need to format the item, pin it in memory if required and
625 * account for the space used by the transaction. Once we have done that we
626 * need to release the unused reservation for the transaction, attach the
627 * transaction to the checkpoint context so we carry the busy extents through
628 * to checkpoint completion, and then unlock all the items in the transaction.
629 *
630 * For more specific information about the order of operations in
631 * xfs_log_commit_cil() please refer to the comments in
632 * xfs_trans_commit_iclog().
633 *
634 * Called with the context lock already held in read mode to lock out
635 * background commit, returns without it held once background commits are
636 * allowed again.
637 */
638void
639xfs_log_commit_cil(
640 struct xfs_mount *mp,
641 struct xfs_trans *tp,
642 struct xfs_log_vec *log_vector,
643 xfs_lsn_t *commit_lsn,
644 int flags)
645{
646 struct log *log = mp->m_log;
647 int log_flags = 0;
648 int push = 0;
649
650 if (flags & XFS_TRANS_RELEASE_LOG_RES)
651 log_flags = XFS_LOG_REL_PERM_RESERV;
652
653 /*
654 * do all the hard work of formatting items (including memory
655 * allocation) outside the CIL context lock. This prevents stalling CIL
656 * pushes when we are low on memory and a transaction commit spends a
657 * lot of time in memory reclaim.
658 */
659 xlog_cil_format_items(log, log_vector);
660
661 /* lock out background commit */
662 down_read(&log->l_cilp->xc_ctx_lock);
663 if (commit_lsn)
664 *commit_lsn = log->l_cilp->xc_ctx->sequence;
665
666 xlog_cil_insert_items(log, log_vector, tp->t_ticket);
667
668 /* check we didn't blow the reservation */
669 if (tp->t_ticket->t_curr_res < 0)
670 xlog_print_tic_res(log->l_mp, tp->t_ticket);
671
672 /* attach the transaction to the CIL if it has any busy extents */
673 if (!list_empty(&tp->t_busy)) {
674 spin_lock(&log->l_cilp->xc_cil_lock);
675 list_splice_init(&tp->t_busy,
676 &log->l_cilp->xc_ctx->busy_extents);
677 spin_unlock(&log->l_cilp->xc_cil_lock);
678 }
679
680 tp->t_commit_lsn = *commit_lsn;
681 xfs_log_done(mp, tp->t_ticket, NULL, log_flags);
682 xfs_trans_unreserve_and_mod_sb(tp);
683
684 /*
685 * Once all the items of the transaction have been copied to the CIL,
686 * the items can be unlocked and freed.
687 *
688 * This needs to be done before we drop the CIL context lock because we
689 * have to update state in the log items and unlock them before they go
690 * to disk. If we don't, then the CIL checkpoint can race with us and
691 * we can run checkpoint completion before we've updated and unlocked
692 * the log items. This affects (at least) processing of stale buffers,
693 * inodes and EFIs.
694 */
695 xfs_trans_free_items(tp, *commit_lsn, 0);
696
697 /* check for background commit before unlock */
698 if (log->l_cilp->xc_ctx->space_used > XLOG_CIL_SPACE_LIMIT(log))
699 push = 1;
700
701 up_read(&log->l_cilp->xc_ctx_lock);
702
703 /*
704 * We need to push CIL every so often so we don't cache more than we
705 * can fit in the log. The limit really is that a checkpoint can't be
706 * more than half the log (the current checkpoint is not allowed to
707 * overwrite the previous checkpoint), but commit latency and memory
708 * usage limit this to a smaller size in most cases.
709 */
710 if (push)
711 xlog_cil_push(log, 0);
712}
713
714/*
715 * Conditionally push the CIL based on the sequence passed in.
716 *
717 * We only need to push if we haven't already pushed the sequence
718 * number given. Hence the only time we will trigger a push here is
719 * if the push sequence is the same as the current context.
720 *
721 * We return the current commit lsn to allow the callers to determine if a
722 * iclog flush is necessary following this call.
723 *
724 * XXX: Initially, just push the CIL unconditionally and return whatever
725 * commit lsn is there. It'll be empty, so this is broken for now.
726 */
727xfs_lsn_t
728xlog_cil_force_lsn(
729 struct log *log,
730 xfs_lsn_t sequence)
731{
732 struct xfs_cil *cil = log->l_cilp;
733 struct xfs_cil_ctx *ctx;
734 xfs_lsn_t commit_lsn = NULLCOMMITLSN;
735
736 ASSERT(sequence <= cil->xc_current_sequence);
737
738 /*
739 * check to see if we need to force out the current context.
740 * xlog_cil_push() handles racing pushes for the same sequence,
741 * so no need to deal with it here.
742 */
743 if (sequence == cil->xc_current_sequence)
744 xlog_cil_push(log, sequence);
745
746 /*
747 * See if we can find a previous sequence still committing.
748 * We need to wait for all previous sequence commits to complete
749 * before allowing the force of push_seq to go ahead. Hence block
750 * on commits for those as well.
751 */
752restart:
753 spin_lock(&cil->xc_cil_lock);
754 list_for_each_entry(ctx, &cil->xc_committing, committing) {
755 if (ctx->sequence > sequence)
756 continue;
757 if (!ctx->commit_lsn) {
758 /*
759 * It is still being pushed! Wait for the push to
760 * complete, then start again from the beginning.
761 */
762 xlog_wait(&cil->xc_commit_wait, &cil->xc_cil_lock);
763 goto restart;
764 }
765 if (ctx->sequence != sequence)
766 continue;
767 /* found it! */
768 commit_lsn = ctx->commit_lsn;
769 }
770 spin_unlock(&cil->xc_cil_lock);
771 return commit_lsn;
772}
773
774/*
775 * Check if the current log item was first committed in this sequence.
776 * We can't rely on just the log item being in the CIL, we have to check
777 * the recorded commit sequence number.
778 *
779 * Note: for this to be used in a non-racy manner, it has to be called with
780 * CIL flushing locked out. As a result, it should only be used during the
781 * transaction commit process when deciding what to format into the item.
782 */
783bool
784xfs_log_item_in_current_chkpt(
785 struct xfs_log_item *lip)
786{
787 struct xfs_cil_ctx *ctx;
788
789 if (!(lip->li_mountp->m_flags & XFS_MOUNT_DELAYLOG))
790 return false;
791 if (list_empty(&lip->li_cil))
792 return false;
793
794 ctx = lip->li_mountp->m_log->l_cilp->xc_ctx;
795
796 /*
797 * li_seq is written on the first commit of a log item to record the
798 * first checkpoint it is written to. Hence if it is different to the
799 * current sequence, we're in a new checkpoint.
800 */
801 if (XFS_LSN_CMP(lip->li_seq, ctx->sequence) != 0)
802 return false;
803 return true;
804}
1/*
2 * Copyright (c) 2010 Red Hat, Inc. All Rights Reserved.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License as
6 * published by the Free Software Foundation.
7 *
8 * This program is distributed in the hope that it would be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 * GNU General Public License for more details.
12 *
13 * You should have received a copy of the GNU General Public License
14 * along with this program; if not, write the Free Software Foundation,
15 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
16 */
17
18#include "xfs.h"
19#include "xfs_fs.h"
20#include "xfs_format.h"
21#include "xfs_log_format.h"
22#include "xfs_shared.h"
23#include "xfs_trans_resv.h"
24#include "xfs_mount.h"
25#include "xfs_error.h"
26#include "xfs_alloc.h"
27#include "xfs_extent_busy.h"
28#include "xfs_discard.h"
29#include "xfs_trans.h"
30#include "xfs_trans_priv.h"
31#include "xfs_log.h"
32#include "xfs_log_priv.h"
33
34/*
35 * Allocate a new ticket. Failing to get a new ticket makes it really hard to
36 * recover, so we don't allow failure here. Also, we allocate in a context that
37 * we don't want to be issuing transactions from, so we need to tell the
38 * allocation code this as well.
39 *
40 * We don't reserve any space for the ticket - we are going to steal whatever
41 * space we require from transactions as they commit. To ensure we reserve all
42 * the space required, we need to set the current reservation of the ticket to
43 * zero so that we know to steal the initial transaction overhead from the
44 * first transaction commit.
45 */
46static struct xlog_ticket *
47xlog_cil_ticket_alloc(
48 struct xlog *log)
49{
50 struct xlog_ticket *tic;
51
52 tic = xlog_ticket_alloc(log, 0, 1, XFS_TRANSACTION, 0,
53 KM_SLEEP|KM_NOFS);
54
55 /*
56 * set the current reservation to zero so we know to steal the basic
57 * transaction overhead reservation from the first transaction commit.
58 */
59 tic->t_curr_res = 0;
60 return tic;
61}
62
63/*
64 * After the first stage of log recovery is done, we know where the head and
65 * tail of the log are. We need this log initialisation done before we can
66 * initialise the first CIL checkpoint context.
67 *
68 * Here we allocate a log ticket to track space usage during a CIL push. This
69 * ticket is passed to xlog_write() directly so that we don't slowly leak log
70 * space by failing to account for space used by log headers and additional
71 * region headers for split regions.
72 */
73void
74xlog_cil_init_post_recovery(
75 struct xlog *log)
76{
77 log->l_cilp->xc_ctx->ticket = xlog_cil_ticket_alloc(log);
78 log->l_cilp->xc_ctx->sequence = 1;
79}
80
81static inline int
82xlog_cil_iovec_space(
83 uint niovecs)
84{
85 return round_up((sizeof(struct xfs_log_vec) +
86 niovecs * sizeof(struct xfs_log_iovec)),
87 sizeof(uint64_t));
88}
89
90/*
91 * Allocate or pin log vector buffers for CIL insertion.
92 *
93 * The CIL currently uses disposable buffers for copying a snapshot of the
94 * modified items into the log during a push. The biggest problem with this is
95 * the requirement to allocate the disposable buffer during the commit if:
96 * a) does not exist; or
97 * b) it is too small
98 *
99 * If we do this allocation within xlog_cil_insert_format_items(), it is done
100 * under the xc_ctx_lock, which means that a CIL push cannot occur during
101 * the memory allocation. This means that we have a potential deadlock situation
102 * under low memory conditions when we have lots of dirty metadata pinned in
103 * the CIL and we need a CIL commit to occur to free memory.
104 *
105 * To avoid this, we need to move the memory allocation outside the
106 * xc_ctx_lock, but because the log vector buffers are disposable, that opens
107 * up a TOCTOU race condition w.r.t. the CIL committing and removing the log
108 * vector buffers between the check and the formatting of the item into the
109 * log vector buffer within the xc_ctx_lock.
110 *
111 * Because the log vector buffer needs to be unchanged during the CIL push
112 * process, we cannot share the buffer between the transaction commit (which
113 * modifies the buffer) and the CIL push context that is writing the changes
114 * into the log. This means skipping preallocation of buffer space is
115 * unreliable, but we most definitely do not want to be allocating and freeing
116 * buffers unnecessarily during commits when overwrites can be done safely.
117 *
118 * The simplest solution to this problem is to allocate a shadow buffer when a
119 * log item is committed for the second time, and then to only use this buffer
120 * if necessary. The buffer can remain attached to the log item until such time
121 * it is needed, and this is the buffer that is reallocated to match the size of
122 * the incoming modification. Then during the formatting of the item we can swap
123 * the active buffer with the new one if we can't reuse the existing buffer. We
124 * don't free the old buffer as it may be reused on the next modification if
125 * it's size is right, otherwise we'll free and reallocate it at that point.
126 *
127 * This function builds a vector for the changes in each log item in the
128 * transaction. It then works out the length of the buffer needed for each log
129 * item, allocates them and attaches the vector to the log item in preparation
130 * for the formatting step which occurs under the xc_ctx_lock.
131 *
132 * While this means the memory footprint goes up, it avoids the repeated
133 * alloc/free pattern that repeated modifications of an item would otherwise
134 * cause, and hence minimises the CPU overhead of such behaviour.
135 */
136static void
137xlog_cil_alloc_shadow_bufs(
138 struct xlog *log,
139 struct xfs_trans *tp)
140{
141 struct xfs_log_item_desc *lidp;
142
143 list_for_each_entry(lidp, &tp->t_items, lid_trans) {
144 struct xfs_log_item *lip = lidp->lid_item;
145 struct xfs_log_vec *lv;
146 int niovecs = 0;
147 int nbytes = 0;
148 int buf_size;
149 bool ordered = false;
150
151 /* Skip items which aren't dirty in this transaction. */
152 if (!(lidp->lid_flags & XFS_LID_DIRTY))
153 continue;
154
155 /* get number of vecs and size of data to be stored */
156 lip->li_ops->iop_size(lip, &niovecs, &nbytes);
157
158 /*
159 * Ordered items need to be tracked but we do not wish to write
160 * them. We need a logvec to track the object, but we do not
161 * need an iovec or buffer to be allocated for copying data.
162 */
163 if (niovecs == XFS_LOG_VEC_ORDERED) {
164 ordered = true;
165 niovecs = 0;
166 nbytes = 0;
167 }
168
169 /*
170 * We 64-bit align the length of each iovec so that the start
171 * of the next one is naturally aligned. We'll need to
172 * account for that slack space here. Then round nbytes up
173 * to 64-bit alignment so that the initial buffer alignment is
174 * easy to calculate and verify.
175 */
176 nbytes += niovecs * sizeof(uint64_t);
177 nbytes = round_up(nbytes, sizeof(uint64_t));
178
179 /*
180 * The data buffer needs to start 64-bit aligned, so round up
181 * that space to ensure we can align it appropriately and not
182 * overrun the buffer.
183 */
184 buf_size = nbytes + xlog_cil_iovec_space(niovecs);
185
186 /*
187 * if we have no shadow buffer, or it is too small, we need to
188 * reallocate it.
189 */
190 if (!lip->li_lv_shadow ||
191 buf_size > lip->li_lv_shadow->lv_size) {
192
193 /*
194 * We free and allocate here as a realloc would copy
195 * unecessary data. We don't use kmem_zalloc() for the
196 * same reason - we don't need to zero the data area in
197 * the buffer, only the log vector header and the iovec
198 * storage.
199 */
200 kmem_free(lip->li_lv_shadow);
201
202 lv = kmem_alloc(buf_size, KM_SLEEP|KM_NOFS);
203 memset(lv, 0, xlog_cil_iovec_space(niovecs));
204
205 lv->lv_item = lip;
206 lv->lv_size = buf_size;
207 if (ordered)
208 lv->lv_buf_len = XFS_LOG_VEC_ORDERED;
209 else
210 lv->lv_iovecp = (struct xfs_log_iovec *)&lv[1];
211 lip->li_lv_shadow = lv;
212 } else {
213 /* same or smaller, optimise common overwrite case */
214 lv = lip->li_lv_shadow;
215 if (ordered)
216 lv->lv_buf_len = XFS_LOG_VEC_ORDERED;
217 else
218 lv->lv_buf_len = 0;
219 lv->lv_bytes = 0;
220 lv->lv_next = NULL;
221 }
222
223 /* Ensure the lv is set up according to ->iop_size */
224 lv->lv_niovecs = niovecs;
225
226 /* The allocated data region lies beyond the iovec region */
227 lv->lv_buf = (char *)lv + xlog_cil_iovec_space(niovecs);
228 }
229
230}
231
232/*
233 * Prepare the log item for insertion into the CIL. Calculate the difference in
234 * log space and vectors it will consume, and if it is a new item pin it as
235 * well.
236 */
237STATIC void
238xfs_cil_prepare_item(
239 struct xlog *log,
240 struct xfs_log_vec *lv,
241 struct xfs_log_vec *old_lv,
242 int *diff_len,
243 int *diff_iovecs)
244{
245 /* Account for the new LV being passed in */
246 if (lv->lv_buf_len != XFS_LOG_VEC_ORDERED) {
247 *diff_len += lv->lv_bytes;
248 *diff_iovecs += lv->lv_niovecs;
249 }
250
251 /*
252 * If there is no old LV, this is the first time we've seen the item in
253 * this CIL context and so we need to pin it. If we are replacing the
254 * old_lv, then remove the space it accounts for and make it the shadow
255 * buffer for later freeing. In both cases we are now switching to the
256 * shadow buffer, so update the the pointer to it appropriately.
257 */
258 if (!old_lv) {
259 lv->lv_item->li_ops->iop_pin(lv->lv_item);
260 lv->lv_item->li_lv_shadow = NULL;
261 } else if (old_lv != lv) {
262 ASSERT(lv->lv_buf_len != XFS_LOG_VEC_ORDERED);
263
264 *diff_len -= old_lv->lv_bytes;
265 *diff_iovecs -= old_lv->lv_niovecs;
266 lv->lv_item->li_lv_shadow = old_lv;
267 }
268
269 /* attach new log vector to log item */
270 lv->lv_item->li_lv = lv;
271
272 /*
273 * If this is the first time the item is being committed to the
274 * CIL, store the sequence number on the log item so we can
275 * tell in future commits whether this is the first checkpoint
276 * the item is being committed into.
277 */
278 if (!lv->lv_item->li_seq)
279 lv->lv_item->li_seq = log->l_cilp->xc_ctx->sequence;
280}
281
282/*
283 * Format log item into a flat buffers
284 *
285 * For delayed logging, we need to hold a formatted buffer containing all the
286 * changes on the log item. This enables us to relog the item in memory and
287 * write it out asynchronously without needing to relock the object that was
288 * modified at the time it gets written into the iclog.
289 *
290 * This function takes the prepared log vectors attached to each log item, and
291 * formats the changes into the log vector buffer. The buffer it uses is
292 * dependent on the current state of the vector in the CIL - the shadow lv is
293 * guaranteed to be large enough for the current modification, but we will only
294 * use that if we can't reuse the existing lv. If we can't reuse the existing
295 * lv, then simple swap it out for the shadow lv. We don't free it - that is
296 * done lazily either by th enext modification or the freeing of the log item.
297 *
298 * We don't set up region headers during this process; we simply copy the
299 * regions into the flat buffer. We can do this because we still have to do a
300 * formatting step to write the regions into the iclog buffer. Writing the
301 * ophdrs during the iclog write means that we can support splitting large
302 * regions across iclog boundares without needing a change in the format of the
303 * item/region encapsulation.
304 *
305 * Hence what we need to do now is change the rewrite the vector array to point
306 * to the copied region inside the buffer we just allocated. This allows us to
307 * format the regions into the iclog as though they are being formatted
308 * directly out of the objects themselves.
309 */
310static void
311xlog_cil_insert_format_items(
312 struct xlog *log,
313 struct xfs_trans *tp,
314 int *diff_len,
315 int *diff_iovecs)
316{
317 struct xfs_log_item_desc *lidp;
318
319
320 /* Bail out if we didn't find a log item. */
321 if (list_empty(&tp->t_items)) {
322 ASSERT(0);
323 return;
324 }
325
326 list_for_each_entry(lidp, &tp->t_items, lid_trans) {
327 struct xfs_log_item *lip = lidp->lid_item;
328 struct xfs_log_vec *lv;
329 struct xfs_log_vec *old_lv = NULL;
330 struct xfs_log_vec *shadow;
331 bool ordered = false;
332
333 /* Skip items which aren't dirty in this transaction. */
334 if (!(lidp->lid_flags & XFS_LID_DIRTY))
335 continue;
336
337 /*
338 * The formatting size information is already attached to
339 * the shadow lv on the log item.
340 */
341 shadow = lip->li_lv_shadow;
342 if (shadow->lv_buf_len == XFS_LOG_VEC_ORDERED)
343 ordered = true;
344
345 /* Skip items that do not have any vectors for writing */
346 if (!shadow->lv_niovecs && !ordered)
347 continue;
348
349 /* compare to existing item size */
350 old_lv = lip->li_lv;
351 if (lip->li_lv && shadow->lv_size <= lip->li_lv->lv_size) {
352 /* same or smaller, optimise common overwrite case */
353 lv = lip->li_lv;
354 lv->lv_next = NULL;
355
356 if (ordered)
357 goto insert;
358
359 /*
360 * set the item up as though it is a new insertion so
361 * that the space reservation accounting is correct.
362 */
363 *diff_iovecs -= lv->lv_niovecs;
364 *diff_len -= lv->lv_bytes;
365
366 /* Ensure the lv is set up according to ->iop_size */
367 lv->lv_niovecs = shadow->lv_niovecs;
368
369 /* reset the lv buffer information for new formatting */
370 lv->lv_buf_len = 0;
371 lv->lv_bytes = 0;
372 lv->lv_buf = (char *)lv +
373 xlog_cil_iovec_space(lv->lv_niovecs);
374 } else {
375 /* switch to shadow buffer! */
376 lv = shadow;
377 lv->lv_item = lip;
378 if (ordered) {
379 /* track as an ordered logvec */
380 ASSERT(lip->li_lv == NULL);
381 goto insert;
382 }
383 }
384
385 ASSERT(IS_ALIGNED((unsigned long)lv->lv_buf, sizeof(uint64_t)));
386 lip->li_ops->iop_format(lip, lv);
387insert:
388 xfs_cil_prepare_item(log, lv, old_lv, diff_len, diff_iovecs);
389 }
390}
391
392/*
393 * Insert the log items into the CIL and calculate the difference in space
394 * consumed by the item. Add the space to the checkpoint ticket and calculate
395 * if the change requires additional log metadata. If it does, take that space
396 * as well. Remove the amount of space we added to the checkpoint ticket from
397 * the current transaction ticket so that the accounting works out correctly.
398 */
399static void
400xlog_cil_insert_items(
401 struct xlog *log,
402 struct xfs_trans *tp)
403{
404 struct xfs_cil *cil = log->l_cilp;
405 struct xfs_cil_ctx *ctx = cil->xc_ctx;
406 struct xfs_log_item_desc *lidp;
407 int len = 0;
408 int diff_iovecs = 0;
409 int iclog_space;
410
411 ASSERT(tp);
412
413 /*
414 * We can do this safely because the context can't checkpoint until we
415 * are done so it doesn't matter exactly how we update the CIL.
416 */
417 xlog_cil_insert_format_items(log, tp, &len, &diff_iovecs);
418
419 /*
420 * Now (re-)position everything modified at the tail of the CIL.
421 * We do this here so we only need to take the CIL lock once during
422 * the transaction commit.
423 */
424 spin_lock(&cil->xc_cil_lock);
425 list_for_each_entry(lidp, &tp->t_items, lid_trans) {
426 struct xfs_log_item *lip = lidp->lid_item;
427
428 /* Skip items which aren't dirty in this transaction. */
429 if (!(lidp->lid_flags & XFS_LID_DIRTY))
430 continue;
431
432 /*
433 * Only move the item if it isn't already at the tail. This is
434 * to prevent a transient list_empty() state when reinserting
435 * an item that is already the only item in the CIL.
436 */
437 if (!list_is_last(&lip->li_cil, &cil->xc_cil))
438 list_move_tail(&lip->li_cil, &cil->xc_cil);
439 }
440
441 /* account for space used by new iovec headers */
442 len += diff_iovecs * sizeof(xlog_op_header_t);
443 ctx->nvecs += diff_iovecs;
444
445 /* attach the transaction to the CIL if it has any busy extents */
446 if (!list_empty(&tp->t_busy))
447 list_splice_init(&tp->t_busy, &ctx->busy_extents);
448
449 /*
450 * Now transfer enough transaction reservation to the context ticket
451 * for the checkpoint. The context ticket is special - the unit
452 * reservation has to grow as well as the current reservation as we
453 * steal from tickets so we can correctly determine the space used
454 * during the transaction commit.
455 */
456 if (ctx->ticket->t_curr_res == 0) {
457 ctx->ticket->t_curr_res = ctx->ticket->t_unit_res;
458 tp->t_ticket->t_curr_res -= ctx->ticket->t_unit_res;
459 }
460
461 /* do we need space for more log record headers? */
462 iclog_space = log->l_iclog_size - log->l_iclog_hsize;
463 if (len > 0 && (ctx->space_used / iclog_space !=
464 (ctx->space_used + len) / iclog_space)) {
465 int hdrs;
466
467 hdrs = (len + iclog_space - 1) / iclog_space;
468 /* need to take into account split region headers, too */
469 hdrs *= log->l_iclog_hsize + sizeof(struct xlog_op_header);
470 ctx->ticket->t_unit_res += hdrs;
471 ctx->ticket->t_curr_res += hdrs;
472 tp->t_ticket->t_curr_res -= hdrs;
473 ASSERT(tp->t_ticket->t_curr_res >= len);
474 }
475 tp->t_ticket->t_curr_res -= len;
476 ctx->space_used += len;
477
478 spin_unlock(&cil->xc_cil_lock);
479}
480
481static void
482xlog_cil_free_logvec(
483 struct xfs_log_vec *log_vector)
484{
485 struct xfs_log_vec *lv;
486
487 for (lv = log_vector; lv; ) {
488 struct xfs_log_vec *next = lv->lv_next;
489 kmem_free(lv);
490 lv = next;
491 }
492}
493
494/*
495 * Mark all items committed and clear busy extents. We free the log vector
496 * chains in a separate pass so that we unpin the log items as quickly as
497 * possible.
498 */
499static void
500xlog_cil_committed(
501 void *args,
502 int abort)
503{
504 struct xfs_cil_ctx *ctx = args;
505 struct xfs_mount *mp = ctx->cil->xc_log->l_mp;
506
507 xfs_trans_committed_bulk(ctx->cil->xc_log->l_ailp, ctx->lv_chain,
508 ctx->start_lsn, abort);
509
510 xfs_extent_busy_sort(&ctx->busy_extents);
511 xfs_extent_busy_clear(mp, &ctx->busy_extents,
512 (mp->m_flags & XFS_MOUNT_DISCARD) && !abort);
513
514 /*
515 * If we are aborting the commit, wake up anyone waiting on the
516 * committing list. If we don't, then a shutdown we can leave processes
517 * waiting in xlog_cil_force_lsn() waiting on a sequence commit that
518 * will never happen because we aborted it.
519 */
520 spin_lock(&ctx->cil->xc_push_lock);
521 if (abort)
522 wake_up_all(&ctx->cil->xc_commit_wait);
523 list_del(&ctx->committing);
524 spin_unlock(&ctx->cil->xc_push_lock);
525
526 xlog_cil_free_logvec(ctx->lv_chain);
527
528 if (!list_empty(&ctx->busy_extents)) {
529 ASSERT(mp->m_flags & XFS_MOUNT_DISCARD);
530
531 xfs_discard_extents(mp, &ctx->busy_extents);
532 xfs_extent_busy_clear(mp, &ctx->busy_extents, false);
533 }
534
535 kmem_free(ctx);
536}
537
538/*
539 * Push the Committed Item List to the log. If @push_seq flag is zero, then it
540 * is a background flush and so we can chose to ignore it. Otherwise, if the
541 * current sequence is the same as @push_seq we need to do a flush. If
542 * @push_seq is less than the current sequence, then it has already been
543 * flushed and we don't need to do anything - the caller will wait for it to
544 * complete if necessary.
545 *
546 * @push_seq is a value rather than a flag because that allows us to do an
547 * unlocked check of the sequence number for a match. Hence we can allows log
548 * forces to run racily and not issue pushes for the same sequence twice. If we
549 * get a race between multiple pushes for the same sequence they will block on
550 * the first one and then abort, hence avoiding needless pushes.
551 */
552STATIC int
553xlog_cil_push(
554 struct xlog *log)
555{
556 struct xfs_cil *cil = log->l_cilp;
557 struct xfs_log_vec *lv;
558 struct xfs_cil_ctx *ctx;
559 struct xfs_cil_ctx *new_ctx;
560 struct xlog_in_core *commit_iclog;
561 struct xlog_ticket *tic;
562 int num_iovecs;
563 int error = 0;
564 struct xfs_trans_header thdr;
565 struct xfs_log_iovec lhdr;
566 struct xfs_log_vec lvhdr = { NULL };
567 xfs_lsn_t commit_lsn;
568 xfs_lsn_t push_seq;
569
570 if (!cil)
571 return 0;
572
573 new_ctx = kmem_zalloc(sizeof(*new_ctx), KM_SLEEP|KM_NOFS);
574 new_ctx->ticket = xlog_cil_ticket_alloc(log);
575
576 down_write(&cil->xc_ctx_lock);
577 ctx = cil->xc_ctx;
578
579 spin_lock(&cil->xc_push_lock);
580 push_seq = cil->xc_push_seq;
581 ASSERT(push_seq <= ctx->sequence);
582
583 /*
584 * Check if we've anything to push. If there is nothing, then we don't
585 * move on to a new sequence number and so we have to be able to push
586 * this sequence again later.
587 */
588 if (list_empty(&cil->xc_cil)) {
589 cil->xc_push_seq = 0;
590 spin_unlock(&cil->xc_push_lock);
591 goto out_skip;
592 }
593
594
595 /* check for a previously pushed seqeunce */
596 if (push_seq < cil->xc_ctx->sequence) {
597 spin_unlock(&cil->xc_push_lock);
598 goto out_skip;
599 }
600
601 /*
602 * We are now going to push this context, so add it to the committing
603 * list before we do anything else. This ensures that anyone waiting on
604 * this push can easily detect the difference between a "push in
605 * progress" and "CIL is empty, nothing to do".
606 *
607 * IOWs, a wait loop can now check for:
608 * the current sequence not being found on the committing list;
609 * an empty CIL; and
610 * an unchanged sequence number
611 * to detect a push that had nothing to do and therefore does not need
612 * waiting on. If the CIL is not empty, we get put on the committing
613 * list before emptying the CIL and bumping the sequence number. Hence
614 * an empty CIL and an unchanged sequence number means we jumped out
615 * above after doing nothing.
616 *
617 * Hence the waiter will either find the commit sequence on the
618 * committing list or the sequence number will be unchanged and the CIL
619 * still dirty. In that latter case, the push has not yet started, and
620 * so the waiter will have to continue trying to check the CIL
621 * committing list until it is found. In extreme cases of delay, the
622 * sequence may fully commit between the attempts the wait makes to wait
623 * on the commit sequence.
624 */
625 list_add(&ctx->committing, &cil->xc_committing);
626 spin_unlock(&cil->xc_push_lock);
627
628 /*
629 * pull all the log vectors off the items in the CIL, and
630 * remove the items from the CIL. We don't need the CIL lock
631 * here because it's only needed on the transaction commit
632 * side which is currently locked out by the flush lock.
633 */
634 lv = NULL;
635 num_iovecs = 0;
636 while (!list_empty(&cil->xc_cil)) {
637 struct xfs_log_item *item;
638
639 item = list_first_entry(&cil->xc_cil,
640 struct xfs_log_item, li_cil);
641 list_del_init(&item->li_cil);
642 if (!ctx->lv_chain)
643 ctx->lv_chain = item->li_lv;
644 else
645 lv->lv_next = item->li_lv;
646 lv = item->li_lv;
647 item->li_lv = NULL;
648 num_iovecs += lv->lv_niovecs;
649 }
650
651 /*
652 * initialise the new context and attach it to the CIL. Then attach
653 * the current context to the CIL committing lsit so it can be found
654 * during log forces to extract the commit lsn of the sequence that
655 * needs to be forced.
656 */
657 INIT_LIST_HEAD(&new_ctx->committing);
658 INIT_LIST_HEAD(&new_ctx->busy_extents);
659 new_ctx->sequence = ctx->sequence + 1;
660 new_ctx->cil = cil;
661 cil->xc_ctx = new_ctx;
662
663 /*
664 * The switch is now done, so we can drop the context lock and move out
665 * of a shared context. We can't just go straight to the commit record,
666 * though - we need to synchronise with previous and future commits so
667 * that the commit records are correctly ordered in the log to ensure
668 * that we process items during log IO completion in the correct order.
669 *
670 * For example, if we get an EFI in one checkpoint and the EFD in the
671 * next (e.g. due to log forces), we do not want the checkpoint with
672 * the EFD to be committed before the checkpoint with the EFI. Hence
673 * we must strictly order the commit records of the checkpoints so
674 * that: a) the checkpoint callbacks are attached to the iclogs in the
675 * correct order; and b) the checkpoints are replayed in correct order
676 * in log recovery.
677 *
678 * Hence we need to add this context to the committing context list so
679 * that higher sequences will wait for us to write out a commit record
680 * before they do.
681 *
682 * xfs_log_force_lsn requires us to mirror the new sequence into the cil
683 * structure atomically with the addition of this sequence to the
684 * committing list. This also ensures that we can do unlocked checks
685 * against the current sequence in log forces without risking
686 * deferencing a freed context pointer.
687 */
688 spin_lock(&cil->xc_push_lock);
689 cil->xc_current_sequence = new_ctx->sequence;
690 spin_unlock(&cil->xc_push_lock);
691 up_write(&cil->xc_ctx_lock);
692
693 /*
694 * Build a checkpoint transaction header and write it to the log to
695 * begin the transaction. We need to account for the space used by the
696 * transaction header here as it is not accounted for in xlog_write().
697 *
698 * The LSN we need to pass to the log items on transaction commit is
699 * the LSN reported by the first log vector write. If we use the commit
700 * record lsn then we can move the tail beyond the grant write head.
701 */
702 tic = ctx->ticket;
703 thdr.th_magic = XFS_TRANS_HEADER_MAGIC;
704 thdr.th_type = XFS_TRANS_CHECKPOINT;
705 thdr.th_tid = tic->t_tid;
706 thdr.th_num_items = num_iovecs;
707 lhdr.i_addr = &thdr;
708 lhdr.i_len = sizeof(xfs_trans_header_t);
709 lhdr.i_type = XLOG_REG_TYPE_TRANSHDR;
710 tic->t_curr_res -= lhdr.i_len + sizeof(xlog_op_header_t);
711
712 lvhdr.lv_niovecs = 1;
713 lvhdr.lv_iovecp = &lhdr;
714 lvhdr.lv_next = ctx->lv_chain;
715
716 error = xlog_write(log, &lvhdr, tic, &ctx->start_lsn, NULL, 0);
717 if (error)
718 goto out_abort_free_ticket;
719
720 /*
721 * now that we've written the checkpoint into the log, strictly
722 * order the commit records so replay will get them in the right order.
723 */
724restart:
725 spin_lock(&cil->xc_push_lock);
726 list_for_each_entry(new_ctx, &cil->xc_committing, committing) {
727 /*
728 * Avoid getting stuck in this loop because we were woken by the
729 * shutdown, but then went back to sleep once already in the
730 * shutdown state.
731 */
732 if (XLOG_FORCED_SHUTDOWN(log)) {
733 spin_unlock(&cil->xc_push_lock);
734 goto out_abort_free_ticket;
735 }
736
737 /*
738 * Higher sequences will wait for this one so skip them.
739 * Don't wait for our own sequence, either.
740 */
741 if (new_ctx->sequence >= ctx->sequence)
742 continue;
743 if (!new_ctx->commit_lsn) {
744 /*
745 * It is still being pushed! Wait for the push to
746 * complete, then start again from the beginning.
747 */
748 xlog_wait(&cil->xc_commit_wait, &cil->xc_push_lock);
749 goto restart;
750 }
751 }
752 spin_unlock(&cil->xc_push_lock);
753
754 /* xfs_log_done always frees the ticket on error. */
755 commit_lsn = xfs_log_done(log->l_mp, tic, &commit_iclog, false);
756 if (commit_lsn == -1)
757 goto out_abort;
758
759 /* attach all the transactions w/ busy extents to iclog */
760 ctx->log_cb.cb_func = xlog_cil_committed;
761 ctx->log_cb.cb_arg = ctx;
762 error = xfs_log_notify(log->l_mp, commit_iclog, &ctx->log_cb);
763 if (error)
764 goto out_abort;
765
766 /*
767 * now the checkpoint commit is complete and we've attached the
768 * callbacks to the iclog we can assign the commit LSN to the context
769 * and wake up anyone who is waiting for the commit to complete.
770 */
771 spin_lock(&cil->xc_push_lock);
772 ctx->commit_lsn = commit_lsn;
773 wake_up_all(&cil->xc_commit_wait);
774 spin_unlock(&cil->xc_push_lock);
775
776 /* release the hounds! */
777 return xfs_log_release_iclog(log->l_mp, commit_iclog);
778
779out_skip:
780 up_write(&cil->xc_ctx_lock);
781 xfs_log_ticket_put(new_ctx->ticket);
782 kmem_free(new_ctx);
783 return 0;
784
785out_abort_free_ticket:
786 xfs_log_ticket_put(tic);
787out_abort:
788 xlog_cil_committed(ctx, XFS_LI_ABORTED);
789 return -EIO;
790}
791
792static void
793xlog_cil_push_work(
794 struct work_struct *work)
795{
796 struct xfs_cil *cil = container_of(work, struct xfs_cil,
797 xc_push_work);
798 xlog_cil_push(cil->xc_log);
799}
800
801/*
802 * We need to push CIL every so often so we don't cache more than we can fit in
803 * the log. The limit really is that a checkpoint can't be more than half the
804 * log (the current checkpoint is not allowed to overwrite the previous
805 * checkpoint), but commit latency and memory usage limit this to a smaller
806 * size.
807 */
808static void
809xlog_cil_push_background(
810 struct xlog *log)
811{
812 struct xfs_cil *cil = log->l_cilp;
813
814 /*
815 * The cil won't be empty because we are called while holding the
816 * context lock so whatever we added to the CIL will still be there
817 */
818 ASSERT(!list_empty(&cil->xc_cil));
819
820 /*
821 * don't do a background push if we haven't used up all the
822 * space available yet.
823 */
824 if (cil->xc_ctx->space_used < XLOG_CIL_SPACE_LIMIT(log))
825 return;
826
827 spin_lock(&cil->xc_push_lock);
828 if (cil->xc_push_seq < cil->xc_current_sequence) {
829 cil->xc_push_seq = cil->xc_current_sequence;
830 queue_work(log->l_mp->m_cil_workqueue, &cil->xc_push_work);
831 }
832 spin_unlock(&cil->xc_push_lock);
833
834}
835
836/*
837 * xlog_cil_push_now() is used to trigger an immediate CIL push to the sequence
838 * number that is passed. When it returns, the work will be queued for
839 * @push_seq, but it won't be completed. The caller is expected to do any
840 * waiting for push_seq to complete if it is required.
841 */
842static void
843xlog_cil_push_now(
844 struct xlog *log,
845 xfs_lsn_t push_seq)
846{
847 struct xfs_cil *cil = log->l_cilp;
848
849 if (!cil)
850 return;
851
852 ASSERT(push_seq && push_seq <= cil->xc_current_sequence);
853
854 /* start on any pending background push to minimise wait time on it */
855 flush_work(&cil->xc_push_work);
856
857 /*
858 * If the CIL is empty or we've already pushed the sequence then
859 * there's no work we need to do.
860 */
861 spin_lock(&cil->xc_push_lock);
862 if (list_empty(&cil->xc_cil) || push_seq <= cil->xc_push_seq) {
863 spin_unlock(&cil->xc_push_lock);
864 return;
865 }
866
867 cil->xc_push_seq = push_seq;
868 queue_work(log->l_mp->m_cil_workqueue, &cil->xc_push_work);
869 spin_unlock(&cil->xc_push_lock);
870}
871
872bool
873xlog_cil_empty(
874 struct xlog *log)
875{
876 struct xfs_cil *cil = log->l_cilp;
877 bool empty = false;
878
879 spin_lock(&cil->xc_push_lock);
880 if (list_empty(&cil->xc_cil))
881 empty = true;
882 spin_unlock(&cil->xc_push_lock);
883 return empty;
884}
885
886/*
887 * Commit a transaction with the given vector to the Committed Item List.
888 *
889 * To do this, we need to format the item, pin it in memory if required and
890 * account for the space used by the transaction. Once we have done that we
891 * need to release the unused reservation for the transaction, attach the
892 * transaction to the checkpoint context so we carry the busy extents through
893 * to checkpoint completion, and then unlock all the items in the transaction.
894 *
895 * Called with the context lock already held in read mode to lock out
896 * background commit, returns without it held once background commits are
897 * allowed again.
898 */
899void
900xfs_log_commit_cil(
901 struct xfs_mount *mp,
902 struct xfs_trans *tp,
903 xfs_lsn_t *commit_lsn,
904 bool regrant)
905{
906 struct xlog *log = mp->m_log;
907 struct xfs_cil *cil = log->l_cilp;
908
909 /*
910 * Do all necessary memory allocation before we lock the CIL.
911 * This ensures the allocation does not deadlock with a CIL
912 * push in memory reclaim (e.g. from kswapd).
913 */
914 xlog_cil_alloc_shadow_bufs(log, tp);
915
916 /* lock out background commit */
917 down_read(&cil->xc_ctx_lock);
918
919 xlog_cil_insert_items(log, tp);
920
921 /* check we didn't blow the reservation */
922 if (tp->t_ticket->t_curr_res < 0)
923 xlog_print_tic_res(mp, tp->t_ticket);
924
925 tp->t_commit_lsn = cil->xc_ctx->sequence;
926 if (commit_lsn)
927 *commit_lsn = tp->t_commit_lsn;
928
929 xfs_log_done(mp, tp->t_ticket, NULL, regrant);
930 xfs_trans_unreserve_and_mod_sb(tp);
931
932 /*
933 * Once all the items of the transaction have been copied to the CIL,
934 * the items can be unlocked and freed.
935 *
936 * This needs to be done before we drop the CIL context lock because we
937 * have to update state in the log items and unlock them before they go
938 * to disk. If we don't, then the CIL checkpoint can race with us and
939 * we can run checkpoint completion before we've updated and unlocked
940 * the log items. This affects (at least) processing of stale buffers,
941 * inodes and EFIs.
942 */
943 xfs_trans_free_items(tp, tp->t_commit_lsn, false);
944
945 xlog_cil_push_background(log);
946
947 up_read(&cil->xc_ctx_lock);
948}
949
950/*
951 * Conditionally push the CIL based on the sequence passed in.
952 *
953 * We only need to push if we haven't already pushed the sequence
954 * number given. Hence the only time we will trigger a push here is
955 * if the push sequence is the same as the current context.
956 *
957 * We return the current commit lsn to allow the callers to determine if a
958 * iclog flush is necessary following this call.
959 */
960xfs_lsn_t
961xlog_cil_force_lsn(
962 struct xlog *log,
963 xfs_lsn_t sequence)
964{
965 struct xfs_cil *cil = log->l_cilp;
966 struct xfs_cil_ctx *ctx;
967 xfs_lsn_t commit_lsn = NULLCOMMITLSN;
968
969 ASSERT(sequence <= cil->xc_current_sequence);
970
971 /*
972 * check to see if we need to force out the current context.
973 * xlog_cil_push() handles racing pushes for the same sequence,
974 * so no need to deal with it here.
975 */
976restart:
977 xlog_cil_push_now(log, sequence);
978
979 /*
980 * See if we can find a previous sequence still committing.
981 * We need to wait for all previous sequence commits to complete
982 * before allowing the force of push_seq to go ahead. Hence block
983 * on commits for those as well.
984 */
985 spin_lock(&cil->xc_push_lock);
986 list_for_each_entry(ctx, &cil->xc_committing, committing) {
987 /*
988 * Avoid getting stuck in this loop because we were woken by the
989 * shutdown, but then went back to sleep once already in the
990 * shutdown state.
991 */
992 if (XLOG_FORCED_SHUTDOWN(log))
993 goto out_shutdown;
994 if (ctx->sequence > sequence)
995 continue;
996 if (!ctx->commit_lsn) {
997 /*
998 * It is still being pushed! Wait for the push to
999 * complete, then start again from the beginning.
1000 */
1001 xlog_wait(&cil->xc_commit_wait, &cil->xc_push_lock);
1002 goto restart;
1003 }
1004 if (ctx->sequence != sequence)
1005 continue;
1006 /* found it! */
1007 commit_lsn = ctx->commit_lsn;
1008 }
1009
1010 /*
1011 * The call to xlog_cil_push_now() executes the push in the background.
1012 * Hence by the time we have got here it our sequence may not have been
1013 * pushed yet. This is true if the current sequence still matches the
1014 * push sequence after the above wait loop and the CIL still contains
1015 * dirty objects. This is guaranteed by the push code first adding the
1016 * context to the committing list before emptying the CIL.
1017 *
1018 * Hence if we don't find the context in the committing list and the
1019 * current sequence number is unchanged then the CIL contents are
1020 * significant. If the CIL is empty, if means there was nothing to push
1021 * and that means there is nothing to wait for. If the CIL is not empty,
1022 * it means we haven't yet started the push, because if it had started
1023 * we would have found the context on the committing list.
1024 */
1025 if (sequence == cil->xc_current_sequence &&
1026 !list_empty(&cil->xc_cil)) {
1027 spin_unlock(&cil->xc_push_lock);
1028 goto restart;
1029 }
1030
1031 spin_unlock(&cil->xc_push_lock);
1032 return commit_lsn;
1033
1034 /*
1035 * We detected a shutdown in progress. We need to trigger the log force
1036 * to pass through it's iclog state machine error handling, even though
1037 * we are already in a shutdown state. Hence we can't return
1038 * NULLCOMMITLSN here as that has special meaning to log forces (i.e.
1039 * LSN is already stable), so we return a zero LSN instead.
1040 */
1041out_shutdown:
1042 spin_unlock(&cil->xc_push_lock);
1043 return 0;
1044}
1045
1046/*
1047 * Check if the current log item was first committed in this sequence.
1048 * We can't rely on just the log item being in the CIL, we have to check
1049 * the recorded commit sequence number.
1050 *
1051 * Note: for this to be used in a non-racy manner, it has to be called with
1052 * CIL flushing locked out. As a result, it should only be used during the
1053 * transaction commit process when deciding what to format into the item.
1054 */
1055bool
1056xfs_log_item_in_current_chkpt(
1057 struct xfs_log_item *lip)
1058{
1059 struct xfs_cil_ctx *ctx;
1060
1061 if (list_empty(&lip->li_cil))
1062 return false;
1063
1064 ctx = lip->li_mountp->m_log->l_cilp->xc_ctx;
1065
1066 /*
1067 * li_seq is written on the first commit of a log item to record the
1068 * first checkpoint it is written to. Hence if it is different to the
1069 * current sequence, we're in a new checkpoint.
1070 */
1071 if (XFS_LSN_CMP(lip->li_seq, ctx->sequence) != 0)
1072 return false;
1073 return true;
1074}
1075
1076/*
1077 * Perform initial CIL structure initialisation.
1078 */
1079int
1080xlog_cil_init(
1081 struct xlog *log)
1082{
1083 struct xfs_cil *cil;
1084 struct xfs_cil_ctx *ctx;
1085
1086 cil = kmem_zalloc(sizeof(*cil), KM_SLEEP|KM_MAYFAIL);
1087 if (!cil)
1088 return -ENOMEM;
1089
1090 ctx = kmem_zalloc(sizeof(*ctx), KM_SLEEP|KM_MAYFAIL);
1091 if (!ctx) {
1092 kmem_free(cil);
1093 return -ENOMEM;
1094 }
1095
1096 INIT_WORK(&cil->xc_push_work, xlog_cil_push_work);
1097 INIT_LIST_HEAD(&cil->xc_cil);
1098 INIT_LIST_HEAD(&cil->xc_committing);
1099 spin_lock_init(&cil->xc_cil_lock);
1100 spin_lock_init(&cil->xc_push_lock);
1101 init_rwsem(&cil->xc_ctx_lock);
1102 init_waitqueue_head(&cil->xc_commit_wait);
1103
1104 INIT_LIST_HEAD(&ctx->committing);
1105 INIT_LIST_HEAD(&ctx->busy_extents);
1106 ctx->sequence = 1;
1107 ctx->cil = cil;
1108 cil->xc_ctx = ctx;
1109 cil->xc_current_sequence = ctx->sequence;
1110
1111 cil->xc_log = log;
1112 log->l_cilp = cil;
1113 return 0;
1114}
1115
1116void
1117xlog_cil_destroy(
1118 struct xlog *log)
1119{
1120 if (log->l_cilp->xc_ctx) {
1121 if (log->l_cilp->xc_ctx->ticket)
1122 xfs_log_ticket_put(log->l_cilp->xc_ctx->ticket);
1123 kmem_free(log->l_cilp->xc_ctx);
1124 }
1125
1126 ASSERT(list_empty(&log->l_cilp->xc_cil));
1127 kmem_free(log->l_cilp);
1128}
1129