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1/*
2 * linux/fs/jbd2/checkpoint.c
3 *
4 * Written by Stephen C. Tweedie <sct@redhat.com>, 1999
5 *
6 * Copyright 1999 Red Hat Software --- All Rights Reserved
7 *
8 * This file is part of the Linux kernel and is made available under
9 * the terms of the GNU General Public License, version 2, or at your
10 * option, any later version, incorporated herein by reference.
11 *
12 * Checkpoint routines for the generic filesystem journaling code.
13 * Part of the ext2fs journaling system.
14 *
15 * Checkpointing is the process of ensuring that a section of the log is
16 * committed fully to disk, so that that portion of the log can be
17 * reused.
18 */
19
20#include <linux/time.h>
21#include <linux/fs.h>
22#include <linux/jbd2.h>
23#include <linux/errno.h>
24#include <linux/slab.h>
25#include <linux/blkdev.h>
26#include <trace/events/jbd2.h>
27
28/*
29 * Unlink a buffer from a transaction checkpoint list.
30 *
31 * Called with j_list_lock held.
32 */
33static inline void __buffer_unlink_first(struct journal_head *jh)
34{
35 transaction_t *transaction = jh->b_cp_transaction;
36
37 jh->b_cpnext->b_cpprev = jh->b_cpprev;
38 jh->b_cpprev->b_cpnext = jh->b_cpnext;
39 if (transaction->t_checkpoint_list == jh) {
40 transaction->t_checkpoint_list = jh->b_cpnext;
41 if (transaction->t_checkpoint_list == jh)
42 transaction->t_checkpoint_list = NULL;
43 }
44}
45
46/*
47 * Unlink a buffer from a transaction checkpoint(io) list.
48 *
49 * Called with j_list_lock held.
50 */
51static inline void __buffer_unlink(struct journal_head *jh)
52{
53 transaction_t *transaction = jh->b_cp_transaction;
54
55 __buffer_unlink_first(jh);
56 if (transaction->t_checkpoint_io_list == jh) {
57 transaction->t_checkpoint_io_list = jh->b_cpnext;
58 if (transaction->t_checkpoint_io_list == jh)
59 transaction->t_checkpoint_io_list = NULL;
60 }
61}
62
63/*
64 * Move a buffer from the checkpoint list to the checkpoint io list
65 *
66 * Called with j_list_lock held
67 */
68static inline void __buffer_relink_io(struct journal_head *jh)
69{
70 transaction_t *transaction = jh->b_cp_transaction;
71
72 __buffer_unlink_first(jh);
73
74 if (!transaction->t_checkpoint_io_list) {
75 jh->b_cpnext = jh->b_cpprev = jh;
76 } else {
77 jh->b_cpnext = transaction->t_checkpoint_io_list;
78 jh->b_cpprev = transaction->t_checkpoint_io_list->b_cpprev;
79 jh->b_cpprev->b_cpnext = jh;
80 jh->b_cpnext->b_cpprev = jh;
81 }
82 transaction->t_checkpoint_io_list = jh;
83}
84
85/*
86 * Try to release a checkpointed buffer from its transaction.
87 * Returns 1 if we released it and 2 if we also released the
88 * whole transaction.
89 *
90 * Requires j_list_lock
91 */
92static int __try_to_free_cp_buf(struct journal_head *jh)
93{
94 int ret = 0;
95 struct buffer_head *bh = jh2bh(jh);
96
97 if (jh->b_transaction == NULL && !buffer_locked(bh) &&
98 !buffer_dirty(bh) && !buffer_write_io_error(bh)) {
99 /*
100 * Get our reference so that bh cannot be freed before
101 * we unlock it
102 */
103 get_bh(bh);
104 JBUFFER_TRACE(jh, "remove from checkpoint list");
105 ret = __jbd2_journal_remove_checkpoint(jh) + 1;
106 BUFFER_TRACE(bh, "release");
107 __brelse(bh);
108 }
109 return ret;
110}
111
112/*
113 * __jbd2_log_wait_for_space: wait until there is space in the journal.
114 *
115 * Called under j-state_lock *only*. It will be unlocked if we have to wait
116 * for a checkpoint to free up some space in the log.
117 */
118void __jbd2_log_wait_for_space(journal_t *journal)
119{
120 int nblocks, space_left;
121 /* assert_spin_locked(&journal->j_state_lock); */
122
123 nblocks = jbd_space_needed(journal);
124 while (__jbd2_log_space_left(journal) < nblocks) {
125 if (journal->j_flags & JBD2_ABORT)
126 return;
127 write_unlock(&journal->j_state_lock);
128 mutex_lock(&journal->j_checkpoint_mutex);
129
130 /*
131 * Test again, another process may have checkpointed while we
132 * were waiting for the checkpoint lock. If there are no
133 * transactions ready to be checkpointed, try to recover
134 * journal space by calling cleanup_journal_tail(), and if
135 * that doesn't work, by waiting for the currently committing
136 * transaction to complete. If there is absolutely no way
137 * to make progress, this is either a BUG or corrupted
138 * filesystem, so abort the journal and leave a stack
139 * trace for forensic evidence.
140 */
141 write_lock(&journal->j_state_lock);
142 spin_lock(&journal->j_list_lock);
143 nblocks = jbd_space_needed(journal);
144 space_left = __jbd2_log_space_left(journal);
145 if (space_left < nblocks) {
146 int chkpt = journal->j_checkpoint_transactions != NULL;
147 tid_t tid = 0;
148
149 if (journal->j_committing_transaction)
150 tid = journal->j_committing_transaction->t_tid;
151 spin_unlock(&journal->j_list_lock);
152 write_unlock(&journal->j_state_lock);
153 if (chkpt) {
154 jbd2_log_do_checkpoint(journal);
155 } else if (jbd2_cleanup_journal_tail(journal) == 0) {
156 /* We were able to recover space; yay! */
157 ;
158 } else if (tid) {
159 jbd2_log_wait_commit(journal, tid);
160 } else {
161 printk(KERN_ERR "%s: needed %d blocks and "
162 "only had %d space available\n",
163 __func__, nblocks, space_left);
164 printk(KERN_ERR "%s: no way to get more "
165 "journal space in %s\n", __func__,
166 journal->j_devname);
167 WARN_ON(1);
168 jbd2_journal_abort(journal, 0);
169 }
170 write_lock(&journal->j_state_lock);
171 } else {
172 spin_unlock(&journal->j_list_lock);
173 }
174 mutex_unlock(&journal->j_checkpoint_mutex);
175 }
176}
177
178/*
179 * Clean up transaction's list of buffers submitted for io.
180 * We wait for any pending IO to complete and remove any clean
181 * buffers. Note that we take the buffers in the opposite ordering
182 * from the one in which they were submitted for IO.
183 *
184 * Return 0 on success, and return <0 if some buffers have failed
185 * to be written out.
186 *
187 * Called with j_list_lock held.
188 */
189static int __wait_cp_io(journal_t *journal, transaction_t *transaction)
190{
191 struct journal_head *jh;
192 struct buffer_head *bh;
193 tid_t this_tid;
194 int released = 0;
195 int ret = 0;
196
197 this_tid = transaction->t_tid;
198restart:
199 /* Did somebody clean up the transaction in the meanwhile? */
200 if (journal->j_checkpoint_transactions != transaction ||
201 transaction->t_tid != this_tid)
202 return ret;
203 while (!released && transaction->t_checkpoint_io_list) {
204 jh = transaction->t_checkpoint_io_list;
205 bh = jh2bh(jh);
206 get_bh(bh);
207 if (buffer_locked(bh)) {
208 spin_unlock(&journal->j_list_lock);
209 wait_on_buffer(bh);
210 /* the journal_head may have gone by now */
211 BUFFER_TRACE(bh, "brelse");
212 __brelse(bh);
213 spin_lock(&journal->j_list_lock);
214 goto restart;
215 }
216 if (unlikely(buffer_write_io_error(bh)))
217 ret = -EIO;
218
219 /*
220 * Now in whatever state the buffer currently is, we know that
221 * it has been written out and so we can drop it from the list
222 */
223 released = __jbd2_journal_remove_checkpoint(jh);
224 __brelse(bh);
225 }
226
227 return ret;
228}
229
230static void
231__flush_batch(journal_t *journal, int *batch_count)
232{
233 int i;
234 struct blk_plug plug;
235
236 blk_start_plug(&plug);
237 for (i = 0; i < *batch_count; i++)
238 write_dirty_buffer(journal->j_chkpt_bhs[i], WRITE_SYNC);
239 blk_finish_plug(&plug);
240
241 for (i = 0; i < *batch_count; i++) {
242 struct buffer_head *bh = journal->j_chkpt_bhs[i];
243 BUFFER_TRACE(bh, "brelse");
244 __brelse(bh);
245 }
246 *batch_count = 0;
247}
248
249/*
250 * Try to flush one buffer from the checkpoint list to disk.
251 *
252 * Return 1 if something happened which requires us to abort the current
253 * scan of the checkpoint list. Return <0 if the buffer has failed to
254 * be written out.
255 *
256 * Called with j_list_lock held and drops it if 1 is returned
257 */
258static int __process_buffer(journal_t *journal, struct journal_head *jh,
259 int *batch_count, transaction_t *transaction)
260{
261 struct buffer_head *bh = jh2bh(jh);
262 int ret = 0;
263
264 if (buffer_locked(bh)) {
265 get_bh(bh);
266 spin_unlock(&journal->j_list_lock);
267 wait_on_buffer(bh);
268 /* the journal_head may have gone by now */
269 BUFFER_TRACE(bh, "brelse");
270 __brelse(bh);
271 ret = 1;
272 } else if (jh->b_transaction != NULL) {
273 transaction_t *t = jh->b_transaction;
274 tid_t tid = t->t_tid;
275
276 transaction->t_chp_stats.cs_forced_to_close++;
277 spin_unlock(&journal->j_list_lock);
278 if (unlikely(journal->j_flags & JBD2_UNMOUNT))
279 /*
280 * The journal thread is dead; so starting and
281 * waiting for a commit to finish will cause
282 * us to wait for a _very_ long time.
283 */
284 printk(KERN_ERR "JBD2: %s: "
285 "Waiting for Godot: block %llu\n",
286 journal->j_devname,
287 (unsigned long long) bh->b_blocknr);
288 jbd2_log_start_commit(journal, tid);
289 jbd2_log_wait_commit(journal, tid);
290 ret = 1;
291 } else if (!buffer_dirty(bh)) {
292 ret = 1;
293 if (unlikely(buffer_write_io_error(bh)))
294 ret = -EIO;
295 get_bh(bh);
296 BUFFER_TRACE(bh, "remove from checkpoint");
297 __jbd2_journal_remove_checkpoint(jh);
298 spin_unlock(&journal->j_list_lock);
299 __brelse(bh);
300 } else {
301 /*
302 * Important: we are about to write the buffer, and
303 * possibly block, while still holding the journal lock.
304 * We cannot afford to let the transaction logic start
305 * messing around with this buffer before we write it to
306 * disk, as that would break recoverability.
307 */
308 BUFFER_TRACE(bh, "queue");
309 get_bh(bh);
310 J_ASSERT_BH(bh, !buffer_jwrite(bh));
311 journal->j_chkpt_bhs[*batch_count] = bh;
312 __buffer_relink_io(jh);
313 transaction->t_chp_stats.cs_written++;
314 (*batch_count)++;
315 if (*batch_count == JBD2_NR_BATCH) {
316 spin_unlock(&journal->j_list_lock);
317 __flush_batch(journal, batch_count);
318 ret = 1;
319 }
320 }
321 return ret;
322}
323
324/*
325 * Perform an actual checkpoint. We take the first transaction on the
326 * list of transactions to be checkpointed and send all its buffers
327 * to disk. We submit larger chunks of data at once.
328 *
329 * The journal should be locked before calling this function.
330 * Called with j_checkpoint_mutex held.
331 */
332int jbd2_log_do_checkpoint(journal_t *journal)
333{
334 transaction_t *transaction;
335 tid_t this_tid;
336 int result;
337
338 jbd_debug(1, "Start checkpoint\n");
339
340 /*
341 * First thing: if there are any transactions in the log which
342 * don't need checkpointing, just eliminate them from the
343 * journal straight away.
344 */
345 result = jbd2_cleanup_journal_tail(journal);
346 trace_jbd2_checkpoint(journal, result);
347 jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
348 if (result <= 0)
349 return result;
350
351 /*
352 * OK, we need to start writing disk blocks. Take one transaction
353 * and write it.
354 */
355 result = 0;
356 spin_lock(&journal->j_list_lock);
357 if (!journal->j_checkpoint_transactions)
358 goto out;
359 transaction = journal->j_checkpoint_transactions;
360 if (transaction->t_chp_stats.cs_chp_time == 0)
361 transaction->t_chp_stats.cs_chp_time = jiffies;
362 this_tid = transaction->t_tid;
363restart:
364 /*
365 * If someone cleaned up this transaction while we slept, we're
366 * done (maybe it's a new transaction, but it fell at the same
367 * address).
368 */
369 if (journal->j_checkpoint_transactions == transaction &&
370 transaction->t_tid == this_tid) {
371 int batch_count = 0;
372 struct journal_head *jh;
373 int retry = 0, err;
374
375 while (!retry && transaction->t_checkpoint_list) {
376 jh = transaction->t_checkpoint_list;
377 retry = __process_buffer(journal, jh, &batch_count,
378 transaction);
379 if (retry < 0 && !result)
380 result = retry;
381 if (!retry && (need_resched() ||
382 spin_needbreak(&journal->j_list_lock))) {
383 spin_unlock(&journal->j_list_lock);
384 retry = 1;
385 break;
386 }
387 }
388
389 if (batch_count) {
390 if (!retry) {
391 spin_unlock(&journal->j_list_lock);
392 retry = 1;
393 }
394 __flush_batch(journal, &batch_count);
395 }
396
397 if (retry) {
398 spin_lock(&journal->j_list_lock);
399 goto restart;
400 }
401 /*
402 * Now we have cleaned up the first transaction's checkpoint
403 * list. Let's clean up the second one
404 */
405 err = __wait_cp_io(journal, transaction);
406 if (!result)
407 result = err;
408 }
409out:
410 spin_unlock(&journal->j_list_lock);
411 if (result < 0)
412 jbd2_journal_abort(journal, result);
413 else
414 result = jbd2_cleanup_journal_tail(journal);
415
416 return (result < 0) ? result : 0;
417}
418
419/*
420 * Check the list of checkpoint transactions for the journal to see if
421 * we have already got rid of any since the last update of the log tail
422 * in the journal superblock. If so, we can instantly roll the
423 * superblock forward to remove those transactions from the log.
424 *
425 * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
426 *
427 * Called with the journal lock held.
428 *
429 * This is the only part of the journaling code which really needs to be
430 * aware of transaction aborts. Checkpointing involves writing to the
431 * main filesystem area rather than to the journal, so it can proceed
432 * even in abort state, but we must not update the super block if
433 * checkpointing may have failed. Otherwise, we would lose some metadata
434 * buffers which should be written-back to the filesystem.
435 */
436
437int jbd2_cleanup_journal_tail(journal_t *journal)
438{
439 tid_t first_tid;
440 unsigned long blocknr;
441
442 if (is_journal_aborted(journal))
443 return 1;
444
445 if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
446 return 1;
447 J_ASSERT(blocknr != 0);
448
449 /*
450 * We need to make sure that any blocks that were recently written out
451 * --- perhaps by jbd2_log_do_checkpoint() --- are flushed out before
452 * we drop the transactions from the journal. It's unlikely this will
453 * be necessary, especially with an appropriately sized journal, but we
454 * need this to guarantee correctness. Fortunately
455 * jbd2_cleanup_journal_tail() doesn't get called all that often.
456 */
457 if (journal->j_flags & JBD2_BARRIER)
458 blkdev_issue_flush(journal->j_fs_dev, GFP_KERNEL, NULL);
459
460 __jbd2_update_log_tail(journal, first_tid, blocknr);
461 return 0;
462}
463
464
465/* Checkpoint list management */
466
467/*
468 * journal_clean_one_cp_list
469 *
470 * Find all the written-back checkpoint buffers in the given list and
471 * release them.
472 *
473 * Called with the journal locked.
474 * Called with j_list_lock held.
475 * Returns number of buffers reaped (for debug)
476 */
477
478static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
479{
480 struct journal_head *last_jh;
481 struct journal_head *next_jh = jh;
482 int ret, freed = 0;
483
484 *released = 0;
485 if (!jh)
486 return 0;
487
488 last_jh = jh->b_cpprev;
489 do {
490 jh = next_jh;
491 next_jh = jh->b_cpnext;
492 ret = __try_to_free_cp_buf(jh);
493 if (ret) {
494 freed++;
495 if (ret == 2) {
496 *released = 1;
497 return freed;
498 }
499 }
500 /*
501 * This function only frees up some memory
502 * if possible so we dont have an obligation
503 * to finish processing. Bail out if preemption
504 * requested:
505 */
506 if (need_resched())
507 return freed;
508 } while (jh != last_jh);
509
510 return freed;
511}
512
513/*
514 * journal_clean_checkpoint_list
515 *
516 * Find all the written-back checkpoint buffers in the journal and release them.
517 *
518 * Called with the journal locked.
519 * Called with j_list_lock held.
520 * Returns number of buffers reaped (for debug)
521 */
522
523int __jbd2_journal_clean_checkpoint_list(journal_t *journal)
524{
525 transaction_t *transaction, *last_transaction, *next_transaction;
526 int ret = 0;
527 int released;
528
529 transaction = journal->j_checkpoint_transactions;
530 if (!transaction)
531 goto out;
532
533 last_transaction = transaction->t_cpprev;
534 next_transaction = transaction;
535 do {
536 transaction = next_transaction;
537 next_transaction = transaction->t_cpnext;
538 ret += journal_clean_one_cp_list(transaction->
539 t_checkpoint_list, &released);
540 /*
541 * This function only frees up some memory if possible so we
542 * dont have an obligation to finish processing. Bail out if
543 * preemption requested:
544 */
545 if (need_resched())
546 goto out;
547 if (released)
548 continue;
549 /*
550 * It is essential that we are as careful as in the case of
551 * t_checkpoint_list with removing the buffer from the list as
552 * we can possibly see not yet submitted buffers on io_list
553 */
554 ret += journal_clean_one_cp_list(transaction->
555 t_checkpoint_io_list, &released);
556 if (need_resched())
557 goto out;
558 } while (transaction != last_transaction);
559out:
560 return ret;
561}
562
563/*
564 * journal_remove_checkpoint: called after a buffer has been committed
565 * to disk (either by being write-back flushed to disk, or being
566 * committed to the log).
567 *
568 * We cannot safely clean a transaction out of the log until all of the
569 * buffer updates committed in that transaction have safely been stored
570 * elsewhere on disk. To achieve this, all of the buffers in a
571 * transaction need to be maintained on the transaction's checkpoint
572 * lists until they have been rewritten, at which point this function is
573 * called to remove the buffer from the existing transaction's
574 * checkpoint lists.
575 *
576 * The function returns 1 if it frees the transaction, 0 otherwise.
577 * The function can free jh and bh.
578 *
579 * This function is called with j_list_lock held.
580 */
581int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
582{
583 struct transaction_chp_stats_s *stats;
584 transaction_t *transaction;
585 journal_t *journal;
586 int ret = 0;
587
588 JBUFFER_TRACE(jh, "entry");
589
590 if ((transaction = jh->b_cp_transaction) == NULL) {
591 JBUFFER_TRACE(jh, "not on transaction");
592 goto out;
593 }
594 journal = transaction->t_journal;
595
596 JBUFFER_TRACE(jh, "removing from transaction");
597 __buffer_unlink(jh);
598 jh->b_cp_transaction = NULL;
599 jbd2_journal_put_journal_head(jh);
600
601 if (transaction->t_checkpoint_list != NULL ||
602 transaction->t_checkpoint_io_list != NULL)
603 goto out;
604
605 /*
606 * There is one special case to worry about: if we have just pulled the
607 * buffer off a running or committing transaction's checkpoing list,
608 * then even if the checkpoint list is empty, the transaction obviously
609 * cannot be dropped!
610 *
611 * The locking here around t_state is a bit sleazy.
612 * See the comment at the end of jbd2_journal_commit_transaction().
613 */
614 if (transaction->t_state != T_FINISHED)
615 goto out;
616
617 /* OK, that was the last buffer for the transaction: we can now
618 safely remove this transaction from the log */
619 stats = &transaction->t_chp_stats;
620 if (stats->cs_chp_time)
621 stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
622 jiffies);
623 trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
624 transaction->t_tid, stats);
625
626 __jbd2_journal_drop_transaction(journal, transaction);
627 jbd2_journal_free_transaction(transaction);
628
629 /* Just in case anybody was waiting for more transactions to be
630 checkpointed... */
631 wake_up(&journal->j_wait_logspace);
632 ret = 1;
633out:
634 return ret;
635}
636
637/*
638 * journal_insert_checkpoint: put a committed buffer onto a checkpoint
639 * list so that we know when it is safe to clean the transaction out of
640 * the log.
641 *
642 * Called with the journal locked.
643 * Called with j_list_lock held.
644 */
645void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
646 transaction_t *transaction)
647{
648 JBUFFER_TRACE(jh, "entry");
649 J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
650 J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
651
652 /* Get reference for checkpointing transaction */
653 jbd2_journal_grab_journal_head(jh2bh(jh));
654 jh->b_cp_transaction = transaction;
655
656 if (!transaction->t_checkpoint_list) {
657 jh->b_cpnext = jh->b_cpprev = jh;
658 } else {
659 jh->b_cpnext = transaction->t_checkpoint_list;
660 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
661 jh->b_cpprev->b_cpnext = jh;
662 jh->b_cpnext->b_cpprev = jh;
663 }
664 transaction->t_checkpoint_list = jh;
665}
666
667/*
668 * We've finished with this transaction structure: adios...
669 *
670 * The transaction must have no links except for the checkpoint by this
671 * point.
672 *
673 * Called with the journal locked.
674 * Called with j_list_lock held.
675 */
676
677void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
678{
679 assert_spin_locked(&journal->j_list_lock);
680 if (transaction->t_cpnext) {
681 transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
682 transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
683 if (journal->j_checkpoint_transactions == transaction)
684 journal->j_checkpoint_transactions =
685 transaction->t_cpnext;
686 if (journal->j_checkpoint_transactions == transaction)
687 journal->j_checkpoint_transactions = NULL;
688 }
689
690 J_ASSERT(transaction->t_state == T_FINISHED);
691 J_ASSERT(transaction->t_buffers == NULL);
692 J_ASSERT(transaction->t_forget == NULL);
693 J_ASSERT(transaction->t_iobuf_list == NULL);
694 J_ASSERT(transaction->t_shadow_list == NULL);
695 J_ASSERT(transaction->t_log_list == NULL);
696 J_ASSERT(transaction->t_checkpoint_list == NULL);
697 J_ASSERT(transaction->t_checkpoint_io_list == NULL);
698 J_ASSERT(atomic_read(&transaction->t_updates) == 0);
699 J_ASSERT(journal->j_committing_transaction != transaction);
700 J_ASSERT(journal->j_running_transaction != transaction);
701
702 trace_jbd2_drop_transaction(journal, transaction);
703
704 jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
705}
1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * linux/fs/jbd2/checkpoint.c
4 *
5 * Written by Stephen C. Tweedie <sct@redhat.com>, 1999
6 *
7 * Copyright 1999 Red Hat Software --- All Rights Reserved
8 *
9 * Checkpoint routines for the generic filesystem journaling code.
10 * Part of the ext2fs journaling system.
11 *
12 * Checkpointing is the process of ensuring that a section of the log is
13 * committed fully to disk, so that that portion of the log can be
14 * reused.
15 */
16
17#include <linux/time.h>
18#include <linux/fs.h>
19#include <linux/jbd2.h>
20#include <linux/errno.h>
21#include <linux/slab.h>
22#include <linux/blkdev.h>
23#include <trace/events/jbd2.h>
24
25/*
26 * Unlink a buffer from a transaction checkpoint list.
27 *
28 * Called with j_list_lock held.
29 */
30static inline void __buffer_unlink(struct journal_head *jh)
31{
32 transaction_t *transaction = jh->b_cp_transaction;
33
34 jh->b_cpnext->b_cpprev = jh->b_cpprev;
35 jh->b_cpprev->b_cpnext = jh->b_cpnext;
36 if (transaction->t_checkpoint_list == jh) {
37 transaction->t_checkpoint_list = jh->b_cpnext;
38 if (transaction->t_checkpoint_list == jh)
39 transaction->t_checkpoint_list = NULL;
40 }
41}
42
43/*
44 * __jbd2_log_wait_for_space: wait until there is space in the journal.
45 *
46 * Called under j-state_lock *only*. It will be unlocked if we have to wait
47 * for a checkpoint to free up some space in the log.
48 */
49void __jbd2_log_wait_for_space(journal_t *journal)
50__acquires(&journal->j_state_lock)
51__releases(&journal->j_state_lock)
52{
53 int nblocks, space_left;
54 /* assert_spin_locked(&journal->j_state_lock); */
55
56 nblocks = journal->j_max_transaction_buffers;
57 while (jbd2_log_space_left(journal) < nblocks) {
58 write_unlock(&journal->j_state_lock);
59 mutex_lock_io(&journal->j_checkpoint_mutex);
60
61 /*
62 * Test again, another process may have checkpointed while we
63 * were waiting for the checkpoint lock. If there are no
64 * transactions ready to be checkpointed, try to recover
65 * journal space by calling cleanup_journal_tail(), and if
66 * that doesn't work, by waiting for the currently committing
67 * transaction to complete. If there is absolutely no way
68 * to make progress, this is either a BUG or corrupted
69 * filesystem, so abort the journal and leave a stack
70 * trace for forensic evidence.
71 */
72 write_lock(&journal->j_state_lock);
73 if (journal->j_flags & JBD2_ABORT) {
74 mutex_unlock(&journal->j_checkpoint_mutex);
75 return;
76 }
77 spin_lock(&journal->j_list_lock);
78 space_left = jbd2_log_space_left(journal);
79 if (space_left < nblocks) {
80 int chkpt = journal->j_checkpoint_transactions != NULL;
81 tid_t tid = 0;
82
83 if (journal->j_committing_transaction)
84 tid = journal->j_committing_transaction->t_tid;
85 spin_unlock(&journal->j_list_lock);
86 write_unlock(&journal->j_state_lock);
87 if (chkpt) {
88 jbd2_log_do_checkpoint(journal);
89 } else if (jbd2_cleanup_journal_tail(journal) == 0) {
90 /* We were able to recover space; yay! */
91 ;
92 } else if (tid) {
93 /*
94 * jbd2_journal_commit_transaction() may want
95 * to take the checkpoint_mutex if JBD2_FLUSHED
96 * is set. So we need to temporarily drop it.
97 */
98 mutex_unlock(&journal->j_checkpoint_mutex);
99 jbd2_log_wait_commit(journal, tid);
100 write_lock(&journal->j_state_lock);
101 continue;
102 } else {
103 printk(KERN_ERR "%s: needed %d blocks and "
104 "only had %d space available\n",
105 __func__, nblocks, space_left);
106 printk(KERN_ERR "%s: no way to get more "
107 "journal space in %s\n", __func__,
108 journal->j_devname);
109 WARN_ON(1);
110 jbd2_journal_abort(journal, -EIO);
111 }
112 write_lock(&journal->j_state_lock);
113 } else {
114 spin_unlock(&journal->j_list_lock);
115 }
116 mutex_unlock(&journal->j_checkpoint_mutex);
117 }
118}
119
120static void
121__flush_batch(journal_t *journal, int *batch_count)
122{
123 int i;
124 struct blk_plug plug;
125
126 blk_start_plug(&plug);
127 for (i = 0; i < *batch_count; i++)
128 write_dirty_buffer(journal->j_chkpt_bhs[i], REQ_SYNC);
129 blk_finish_plug(&plug);
130
131 for (i = 0; i < *batch_count; i++) {
132 struct buffer_head *bh = journal->j_chkpt_bhs[i];
133 BUFFER_TRACE(bh, "brelse");
134 __brelse(bh);
135 journal->j_chkpt_bhs[i] = NULL;
136 }
137 *batch_count = 0;
138}
139
140/*
141 * Perform an actual checkpoint. We take the first transaction on the
142 * list of transactions to be checkpointed and send all its buffers
143 * to disk. We submit larger chunks of data at once.
144 *
145 * The journal should be locked before calling this function.
146 * Called with j_checkpoint_mutex held.
147 */
148int jbd2_log_do_checkpoint(journal_t *journal)
149{
150 struct journal_head *jh;
151 struct buffer_head *bh;
152 transaction_t *transaction;
153 tid_t this_tid;
154 int result, batch_count = 0;
155
156 jbd2_debug(1, "Start checkpoint\n");
157
158 /*
159 * First thing: if there are any transactions in the log which
160 * don't need checkpointing, just eliminate them from the
161 * journal straight away.
162 */
163 result = jbd2_cleanup_journal_tail(journal);
164 trace_jbd2_checkpoint(journal, result);
165 jbd2_debug(1, "cleanup_journal_tail returned %d\n", result);
166 if (result <= 0)
167 return result;
168
169 /*
170 * OK, we need to start writing disk blocks. Take one transaction
171 * and write it.
172 */
173 spin_lock(&journal->j_list_lock);
174 if (!journal->j_checkpoint_transactions)
175 goto out;
176 transaction = journal->j_checkpoint_transactions;
177 if (transaction->t_chp_stats.cs_chp_time == 0)
178 transaction->t_chp_stats.cs_chp_time = jiffies;
179 this_tid = transaction->t_tid;
180restart:
181 /*
182 * If someone cleaned up this transaction while we slept, we're
183 * done (maybe it's a new transaction, but it fell at the same
184 * address).
185 */
186 if (journal->j_checkpoint_transactions != transaction ||
187 transaction->t_tid != this_tid)
188 goto out;
189
190 /* checkpoint all of the transaction's buffers */
191 while (transaction->t_checkpoint_list) {
192 jh = transaction->t_checkpoint_list;
193 bh = jh2bh(jh);
194
195 if (jh->b_transaction != NULL) {
196 transaction_t *t = jh->b_transaction;
197 tid_t tid = t->t_tid;
198
199 transaction->t_chp_stats.cs_forced_to_close++;
200 spin_unlock(&journal->j_list_lock);
201 if (unlikely(journal->j_flags & JBD2_UNMOUNT))
202 /*
203 * The journal thread is dead; so
204 * starting and waiting for a commit
205 * to finish will cause us to wait for
206 * a _very_ long time.
207 */
208 printk(KERN_ERR
209 "JBD2: %s: Waiting for Godot: block %llu\n",
210 journal->j_devname, (unsigned long long) bh->b_blocknr);
211
212 if (batch_count)
213 __flush_batch(journal, &batch_count);
214 jbd2_log_start_commit(journal, tid);
215 /*
216 * jbd2_journal_commit_transaction() may want
217 * to take the checkpoint_mutex if JBD2_FLUSHED
218 * is set, jbd2_update_log_tail() called by
219 * jbd2_journal_commit_transaction() may also take
220 * checkpoint_mutex. So we need to temporarily
221 * drop it.
222 */
223 mutex_unlock(&journal->j_checkpoint_mutex);
224 jbd2_log_wait_commit(journal, tid);
225 mutex_lock_io(&journal->j_checkpoint_mutex);
226 spin_lock(&journal->j_list_lock);
227 goto restart;
228 }
229 if (!trylock_buffer(bh)) {
230 /*
231 * The buffer is locked, it may be writing back, or
232 * flushing out in the last couple of cycles, or
233 * re-adding into a new transaction, need to check
234 * it again until it's unlocked.
235 */
236 get_bh(bh);
237 spin_unlock(&journal->j_list_lock);
238 wait_on_buffer(bh);
239 /* the journal_head may have gone by now */
240 BUFFER_TRACE(bh, "brelse");
241 __brelse(bh);
242 goto retry;
243 } else if (!buffer_dirty(bh)) {
244 unlock_buffer(bh);
245 BUFFER_TRACE(bh, "remove from checkpoint");
246 /*
247 * If the transaction was released or the checkpoint
248 * list was empty, we're done.
249 */
250 if (__jbd2_journal_remove_checkpoint(jh) ||
251 !transaction->t_checkpoint_list)
252 goto out;
253 } else {
254 unlock_buffer(bh);
255 /*
256 * We are about to write the buffer, it could be
257 * raced by some other transaction shrink or buffer
258 * re-log logic once we release the j_list_lock,
259 * leave it on the checkpoint list and check status
260 * again to make sure it's clean.
261 */
262 BUFFER_TRACE(bh, "queue");
263 get_bh(bh);
264 J_ASSERT_BH(bh, !buffer_jwrite(bh));
265 journal->j_chkpt_bhs[batch_count++] = bh;
266 transaction->t_chp_stats.cs_written++;
267 transaction->t_checkpoint_list = jh->b_cpnext;
268 }
269
270 if ((batch_count == JBD2_NR_BATCH) ||
271 need_resched() || spin_needbreak(&journal->j_list_lock) ||
272 jh2bh(transaction->t_checkpoint_list) == journal->j_chkpt_bhs[0])
273 goto unlock_and_flush;
274 }
275
276 if (batch_count) {
277 unlock_and_flush:
278 spin_unlock(&journal->j_list_lock);
279 retry:
280 if (batch_count)
281 __flush_batch(journal, &batch_count);
282 spin_lock(&journal->j_list_lock);
283 goto restart;
284 }
285
286out:
287 spin_unlock(&journal->j_list_lock);
288 result = jbd2_cleanup_journal_tail(journal);
289
290 return (result < 0) ? result : 0;
291}
292
293/*
294 * Check the list of checkpoint transactions for the journal to see if
295 * we have already got rid of any since the last update of the log tail
296 * in the journal superblock. If so, we can instantly roll the
297 * superblock forward to remove those transactions from the log.
298 *
299 * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
300 *
301 * Called with the journal lock held.
302 *
303 * This is the only part of the journaling code which really needs to be
304 * aware of transaction aborts. Checkpointing involves writing to the
305 * main filesystem area rather than to the journal, so it can proceed
306 * even in abort state, but we must not update the super block if
307 * checkpointing may have failed. Otherwise, we would lose some metadata
308 * buffers which should be written-back to the filesystem.
309 */
310
311int jbd2_cleanup_journal_tail(journal_t *journal)
312{
313 tid_t first_tid;
314 unsigned long blocknr;
315
316 if (is_journal_aborted(journal))
317 return -EIO;
318
319 if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
320 return 1;
321 J_ASSERT(blocknr != 0);
322
323 /*
324 * We need to make sure that any blocks that were recently written out
325 * --- perhaps by jbd2_log_do_checkpoint() --- are flushed out before
326 * we drop the transactions from the journal. It's unlikely this will
327 * be necessary, especially with an appropriately sized journal, but we
328 * need this to guarantee correctness. Fortunately
329 * jbd2_cleanup_journal_tail() doesn't get called all that often.
330 */
331 if (journal->j_flags & JBD2_BARRIER)
332 blkdev_issue_flush(journal->j_fs_dev);
333
334 return __jbd2_update_log_tail(journal, first_tid, blocknr);
335}
336
337
338/* Checkpoint list management */
339
340enum shrink_type {SHRINK_DESTROY, SHRINK_BUSY_STOP, SHRINK_BUSY_SKIP};
341
342/*
343 * journal_shrink_one_cp_list
344 *
345 * Find all the written-back checkpoint buffers in the given list
346 * and try to release them. If the whole transaction is released, set
347 * the 'released' parameter. Return the number of released checkpointed
348 * buffers.
349 *
350 * Called with j_list_lock held.
351 */
352static unsigned long journal_shrink_one_cp_list(struct journal_head *jh,
353 enum shrink_type type,
354 bool *released)
355{
356 struct journal_head *last_jh;
357 struct journal_head *next_jh = jh;
358 unsigned long nr_freed = 0;
359 int ret;
360
361 *released = false;
362 if (!jh)
363 return 0;
364
365 last_jh = jh->b_cpprev;
366 do {
367 jh = next_jh;
368 next_jh = jh->b_cpnext;
369
370 if (type == SHRINK_DESTROY) {
371 ret = __jbd2_journal_remove_checkpoint(jh);
372 } else {
373 ret = jbd2_journal_try_remove_checkpoint(jh);
374 if (ret < 0) {
375 if (type == SHRINK_BUSY_SKIP)
376 continue;
377 break;
378 }
379 }
380
381 nr_freed++;
382 if (ret) {
383 *released = true;
384 break;
385 }
386
387 if (need_resched())
388 break;
389 } while (jh != last_jh);
390
391 return nr_freed;
392}
393
394/*
395 * jbd2_journal_shrink_checkpoint_list
396 *
397 * Find 'nr_to_scan' written-back checkpoint buffers in the journal
398 * and try to release them. Return the number of released checkpointed
399 * buffers.
400 *
401 * Called with j_list_lock held.
402 */
403unsigned long jbd2_journal_shrink_checkpoint_list(journal_t *journal,
404 unsigned long *nr_to_scan)
405{
406 transaction_t *transaction, *last_transaction, *next_transaction;
407 bool __maybe_unused released;
408 tid_t first_tid = 0, last_tid = 0, next_tid = 0;
409 tid_t tid = 0;
410 unsigned long nr_freed = 0;
411 unsigned long freed;
412
413again:
414 spin_lock(&journal->j_list_lock);
415 if (!journal->j_checkpoint_transactions) {
416 spin_unlock(&journal->j_list_lock);
417 goto out;
418 }
419
420 /*
421 * Get next shrink transaction, resume previous scan or start
422 * over again. If some others do checkpoint and drop transaction
423 * from the checkpoint list, we ignore saved j_shrink_transaction
424 * and start over unconditionally.
425 */
426 if (journal->j_shrink_transaction)
427 transaction = journal->j_shrink_transaction;
428 else
429 transaction = journal->j_checkpoint_transactions;
430
431 if (!first_tid)
432 first_tid = transaction->t_tid;
433 last_transaction = journal->j_checkpoint_transactions->t_cpprev;
434 next_transaction = transaction;
435 last_tid = last_transaction->t_tid;
436 do {
437 transaction = next_transaction;
438 next_transaction = transaction->t_cpnext;
439 tid = transaction->t_tid;
440
441 freed = journal_shrink_one_cp_list(transaction->t_checkpoint_list,
442 SHRINK_BUSY_SKIP, &released);
443 nr_freed += freed;
444 (*nr_to_scan) -= min(*nr_to_scan, freed);
445 if (*nr_to_scan == 0)
446 break;
447 if (need_resched() || spin_needbreak(&journal->j_list_lock))
448 break;
449 } while (transaction != last_transaction);
450
451 if (transaction != last_transaction) {
452 journal->j_shrink_transaction = next_transaction;
453 next_tid = next_transaction->t_tid;
454 } else {
455 journal->j_shrink_transaction = NULL;
456 next_tid = 0;
457 }
458
459 spin_unlock(&journal->j_list_lock);
460 cond_resched();
461
462 if (*nr_to_scan && next_tid)
463 goto again;
464out:
465 trace_jbd2_shrink_checkpoint_list(journal, first_tid, tid, last_tid,
466 nr_freed, next_tid);
467
468 return nr_freed;
469}
470
471/*
472 * journal_clean_checkpoint_list
473 *
474 * Find all the written-back checkpoint buffers in the journal and release them.
475 * If 'destroy' is set, release all buffers unconditionally.
476 *
477 * Called with j_list_lock held.
478 */
479void __jbd2_journal_clean_checkpoint_list(journal_t *journal, bool destroy)
480{
481 transaction_t *transaction, *last_transaction, *next_transaction;
482 enum shrink_type type;
483 bool released;
484
485 transaction = journal->j_checkpoint_transactions;
486 if (!transaction)
487 return;
488
489 type = destroy ? SHRINK_DESTROY : SHRINK_BUSY_STOP;
490 last_transaction = transaction->t_cpprev;
491 next_transaction = transaction;
492 do {
493 transaction = next_transaction;
494 next_transaction = transaction->t_cpnext;
495 journal_shrink_one_cp_list(transaction->t_checkpoint_list,
496 type, &released);
497 /*
498 * This function only frees up some memory if possible so we
499 * dont have an obligation to finish processing. Bail out if
500 * preemption requested:
501 */
502 if (need_resched())
503 return;
504 /*
505 * Stop scanning if we couldn't free the transaction. This
506 * avoids pointless scanning of transactions which still
507 * weren't checkpointed.
508 */
509 if (!released)
510 return;
511 } while (transaction != last_transaction);
512}
513
514/*
515 * Remove buffers from all checkpoint lists as journal is aborted and we just
516 * need to free memory
517 */
518void jbd2_journal_destroy_checkpoint(journal_t *journal)
519{
520 /*
521 * We loop because __jbd2_journal_clean_checkpoint_list() may abort
522 * early due to a need of rescheduling.
523 */
524 while (1) {
525 spin_lock(&journal->j_list_lock);
526 if (!journal->j_checkpoint_transactions) {
527 spin_unlock(&journal->j_list_lock);
528 break;
529 }
530 __jbd2_journal_clean_checkpoint_list(journal, true);
531 spin_unlock(&journal->j_list_lock);
532 cond_resched();
533 }
534}
535
536/*
537 * journal_remove_checkpoint: called after a buffer has been committed
538 * to disk (either by being write-back flushed to disk, or being
539 * committed to the log).
540 *
541 * We cannot safely clean a transaction out of the log until all of the
542 * buffer updates committed in that transaction have safely been stored
543 * elsewhere on disk. To achieve this, all of the buffers in a
544 * transaction need to be maintained on the transaction's checkpoint
545 * lists until they have been rewritten, at which point this function is
546 * called to remove the buffer from the existing transaction's
547 * checkpoint lists.
548 *
549 * The function returns 1 if it frees the transaction, 0 otherwise.
550 * The function can free jh and bh.
551 *
552 * This function is called with j_list_lock held.
553 */
554int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
555{
556 struct transaction_chp_stats_s *stats;
557 transaction_t *transaction;
558 journal_t *journal;
559
560 JBUFFER_TRACE(jh, "entry");
561
562 transaction = jh->b_cp_transaction;
563 if (!transaction) {
564 JBUFFER_TRACE(jh, "not on transaction");
565 return 0;
566 }
567 journal = transaction->t_journal;
568
569 JBUFFER_TRACE(jh, "removing from transaction");
570
571 __buffer_unlink(jh);
572 jh->b_cp_transaction = NULL;
573 percpu_counter_dec(&journal->j_checkpoint_jh_count);
574 jbd2_journal_put_journal_head(jh);
575
576 /* Is this transaction empty? */
577 if (transaction->t_checkpoint_list)
578 return 0;
579
580 /*
581 * There is one special case to worry about: if we have just pulled the
582 * buffer off a running or committing transaction's checkpoing list,
583 * then even if the checkpoint list is empty, the transaction obviously
584 * cannot be dropped!
585 *
586 * The locking here around t_state is a bit sleazy.
587 * See the comment at the end of jbd2_journal_commit_transaction().
588 */
589 if (transaction->t_state != T_FINISHED)
590 return 0;
591
592 /*
593 * OK, that was the last buffer for the transaction, we can now
594 * safely remove this transaction from the log.
595 */
596 stats = &transaction->t_chp_stats;
597 if (stats->cs_chp_time)
598 stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
599 jiffies);
600 trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
601 transaction->t_tid, stats);
602
603 __jbd2_journal_drop_transaction(journal, transaction);
604 jbd2_journal_free_transaction(transaction);
605 return 1;
606}
607
608/*
609 * Check the checkpoint buffer and try to remove it from the checkpoint
610 * list if it's clean. Returns -EBUSY if it is not clean, returns 1 if
611 * it frees the transaction, 0 otherwise.
612 *
613 * This function is called with j_list_lock held.
614 */
615int jbd2_journal_try_remove_checkpoint(struct journal_head *jh)
616{
617 struct buffer_head *bh = jh2bh(jh);
618
619 if (jh->b_transaction)
620 return -EBUSY;
621 if (!trylock_buffer(bh))
622 return -EBUSY;
623 if (buffer_dirty(bh)) {
624 unlock_buffer(bh);
625 return -EBUSY;
626 }
627 unlock_buffer(bh);
628
629 /*
630 * Buffer is clean and the IO has finished (we held the buffer
631 * lock) so the checkpoint is done. We can safely remove the
632 * buffer from this transaction.
633 */
634 JBUFFER_TRACE(jh, "remove from checkpoint list");
635 return __jbd2_journal_remove_checkpoint(jh);
636}
637
638/*
639 * journal_insert_checkpoint: put a committed buffer onto a checkpoint
640 * list so that we know when it is safe to clean the transaction out of
641 * the log.
642 *
643 * Called with the journal locked.
644 * Called with j_list_lock held.
645 */
646void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
647 transaction_t *transaction)
648{
649 JBUFFER_TRACE(jh, "entry");
650 J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
651 J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
652
653 /* Get reference for checkpointing transaction */
654 jbd2_journal_grab_journal_head(jh2bh(jh));
655 jh->b_cp_transaction = transaction;
656
657 if (!transaction->t_checkpoint_list) {
658 jh->b_cpnext = jh->b_cpprev = jh;
659 } else {
660 jh->b_cpnext = transaction->t_checkpoint_list;
661 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
662 jh->b_cpprev->b_cpnext = jh;
663 jh->b_cpnext->b_cpprev = jh;
664 }
665 transaction->t_checkpoint_list = jh;
666 percpu_counter_inc(&transaction->t_journal->j_checkpoint_jh_count);
667}
668
669/*
670 * We've finished with this transaction structure: adios...
671 *
672 * The transaction must have no links except for the checkpoint by this
673 * point.
674 *
675 * Called with the journal locked.
676 * Called with j_list_lock held.
677 */
678
679void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
680{
681 assert_spin_locked(&journal->j_list_lock);
682
683 journal->j_shrink_transaction = NULL;
684 if (transaction->t_cpnext) {
685 transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
686 transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
687 if (journal->j_checkpoint_transactions == transaction)
688 journal->j_checkpoint_transactions =
689 transaction->t_cpnext;
690 if (journal->j_checkpoint_transactions == transaction)
691 journal->j_checkpoint_transactions = NULL;
692 }
693
694 J_ASSERT(transaction->t_state == T_FINISHED);
695 J_ASSERT(transaction->t_buffers == NULL);
696 J_ASSERT(transaction->t_forget == NULL);
697 J_ASSERT(transaction->t_shadow_list == NULL);
698 J_ASSERT(transaction->t_checkpoint_list == NULL);
699 J_ASSERT(atomic_read(&transaction->t_updates) == 0);
700 J_ASSERT(journal->j_committing_transaction != transaction);
701 J_ASSERT(journal->j_running_transaction != transaction);
702
703 trace_jbd2_drop_transaction(journal, transaction);
704
705 jbd2_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
706}