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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_first(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 * Unlink a buffer from a transaction checkpoint(io) list.
45 *
46 * Called with j_list_lock held.
47 */
48static inline void __buffer_unlink(struct journal_head *jh)
49{
50 transaction_t *transaction = jh->b_cp_transaction;
51
52 __buffer_unlink_first(jh);
53 if (transaction->t_checkpoint_io_list == jh) {
54 transaction->t_checkpoint_io_list = jh->b_cpnext;
55 if (transaction->t_checkpoint_io_list == jh)
56 transaction->t_checkpoint_io_list = NULL;
57 }
58}
59
60/*
61 * Move a buffer from the checkpoint list to the checkpoint io list
62 *
63 * Called with j_list_lock held
64 */
65static inline void __buffer_relink_io(struct journal_head *jh)
66{
67 transaction_t *transaction = jh->b_cp_transaction;
68
69 __buffer_unlink_first(jh);
70
71 if (!transaction->t_checkpoint_io_list) {
72 jh->b_cpnext = jh->b_cpprev = jh;
73 } else {
74 jh->b_cpnext = transaction->t_checkpoint_io_list;
75 jh->b_cpprev = transaction->t_checkpoint_io_list->b_cpprev;
76 jh->b_cpprev->b_cpnext = jh;
77 jh->b_cpnext->b_cpprev = jh;
78 }
79 transaction->t_checkpoint_io_list = jh;
80}
81
82/*
83 * Try to release a checkpointed buffer from its transaction.
84 * Returns 1 if we released it and 2 if we also released the
85 * whole transaction.
86 *
87 * Requires j_list_lock
88 */
89static int __try_to_free_cp_buf(struct journal_head *jh)
90{
91 int ret = 0;
92 struct buffer_head *bh = jh2bh(jh);
93
94 if (jh->b_transaction == NULL && !buffer_locked(bh) &&
95 !buffer_dirty(bh) && !buffer_write_io_error(bh)) {
96 JBUFFER_TRACE(jh, "remove from checkpoint list");
97 ret = __jbd2_journal_remove_checkpoint(jh) + 1;
98 }
99 return ret;
100}
101
102/*
103 * __jbd2_log_wait_for_space: wait until there is space in the journal.
104 *
105 * Called under j-state_lock *only*. It will be unlocked if we have to wait
106 * for a checkpoint to free up some space in the log.
107 */
108void __jbd2_log_wait_for_space(journal_t *journal)
109{
110 int nblocks, space_left;
111 /* assert_spin_locked(&journal->j_state_lock); */
112
113 nblocks = journal->j_max_transaction_buffers;
114 while (jbd2_log_space_left(journal) < nblocks) {
115 write_unlock(&journal->j_state_lock);
116 mutex_lock_io(&journal->j_checkpoint_mutex);
117
118 /*
119 * Test again, another process may have checkpointed while we
120 * were waiting for the checkpoint lock. If there are no
121 * transactions ready to be checkpointed, try to recover
122 * journal space by calling cleanup_journal_tail(), and if
123 * that doesn't work, by waiting for the currently committing
124 * transaction to complete. If there is absolutely no way
125 * to make progress, this is either a BUG or corrupted
126 * filesystem, so abort the journal and leave a stack
127 * trace for forensic evidence.
128 */
129 write_lock(&journal->j_state_lock);
130 if (journal->j_flags & JBD2_ABORT) {
131 mutex_unlock(&journal->j_checkpoint_mutex);
132 return;
133 }
134 spin_lock(&journal->j_list_lock);
135 space_left = jbd2_log_space_left(journal);
136 if (space_left < nblocks) {
137 int chkpt = journal->j_checkpoint_transactions != NULL;
138 tid_t tid = 0;
139
140 if (journal->j_committing_transaction)
141 tid = journal->j_committing_transaction->t_tid;
142 spin_unlock(&journal->j_list_lock);
143 write_unlock(&journal->j_state_lock);
144 if (chkpt) {
145 jbd2_log_do_checkpoint(journal);
146 } else if (jbd2_cleanup_journal_tail(journal) == 0) {
147 /* We were able to recover space; yay! */
148 ;
149 } else if (tid) {
150 /*
151 * jbd2_journal_commit_transaction() may want
152 * to take the checkpoint_mutex if JBD2_FLUSHED
153 * is set. So we need to temporarily drop it.
154 */
155 mutex_unlock(&journal->j_checkpoint_mutex);
156 jbd2_log_wait_commit(journal, tid);
157 write_lock(&journal->j_state_lock);
158 continue;
159 } else {
160 printk(KERN_ERR "%s: needed %d blocks and "
161 "only had %d space available\n",
162 __func__, nblocks, space_left);
163 printk(KERN_ERR "%s: no way to get more "
164 "journal space in %s\n", __func__,
165 journal->j_devname);
166 WARN_ON(1);
167 jbd2_journal_abort(journal, -EIO);
168 }
169 write_lock(&journal->j_state_lock);
170 } else {
171 spin_unlock(&journal->j_list_lock);
172 }
173 mutex_unlock(&journal->j_checkpoint_mutex);
174 }
175}
176
177static void
178__flush_batch(journal_t *journal, int *batch_count)
179{
180 int i;
181 struct blk_plug plug;
182
183 blk_start_plug(&plug);
184 for (i = 0; i < *batch_count; i++)
185 write_dirty_buffer(journal->j_chkpt_bhs[i], REQ_SYNC);
186 blk_finish_plug(&plug);
187
188 for (i = 0; i < *batch_count; i++) {
189 struct buffer_head *bh = journal->j_chkpt_bhs[i];
190 BUFFER_TRACE(bh, "brelse");
191 __brelse(bh);
192 }
193 *batch_count = 0;
194}
195
196/*
197 * Perform an actual checkpoint. We take the first transaction on the
198 * list of transactions to be checkpointed and send all its buffers
199 * to disk. We submit larger chunks of data at once.
200 *
201 * The journal should be locked before calling this function.
202 * Called with j_checkpoint_mutex held.
203 */
204int jbd2_log_do_checkpoint(journal_t *journal)
205{
206 struct journal_head *jh;
207 struct buffer_head *bh;
208 transaction_t *transaction;
209 tid_t this_tid;
210 int result, batch_count = 0;
211
212 jbd_debug(1, "Start checkpoint\n");
213
214 /*
215 * First thing: if there are any transactions in the log which
216 * don't need checkpointing, just eliminate them from the
217 * journal straight away.
218 */
219 result = jbd2_cleanup_journal_tail(journal);
220 trace_jbd2_checkpoint(journal, result);
221 jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
222 if (result <= 0)
223 return result;
224
225 /*
226 * OK, we need to start writing disk blocks. Take one transaction
227 * and write it.
228 */
229 result = 0;
230 spin_lock(&journal->j_list_lock);
231 if (!journal->j_checkpoint_transactions)
232 goto out;
233 transaction = journal->j_checkpoint_transactions;
234 if (transaction->t_chp_stats.cs_chp_time == 0)
235 transaction->t_chp_stats.cs_chp_time = jiffies;
236 this_tid = transaction->t_tid;
237restart:
238 /*
239 * If someone cleaned up this transaction while we slept, we're
240 * done (maybe it's a new transaction, but it fell at the same
241 * address).
242 */
243 if (journal->j_checkpoint_transactions != transaction ||
244 transaction->t_tid != this_tid)
245 goto out;
246
247 /* checkpoint all of the transaction's buffers */
248 while (transaction->t_checkpoint_list) {
249 jh = transaction->t_checkpoint_list;
250 bh = jh2bh(jh);
251
252 if (buffer_locked(bh)) {
253 get_bh(bh);
254 spin_unlock(&journal->j_list_lock);
255 wait_on_buffer(bh);
256 /* the journal_head may have gone by now */
257 BUFFER_TRACE(bh, "brelse");
258 __brelse(bh);
259 goto retry;
260 }
261 if (jh->b_transaction != NULL) {
262 transaction_t *t = jh->b_transaction;
263 tid_t tid = t->t_tid;
264
265 transaction->t_chp_stats.cs_forced_to_close++;
266 spin_unlock(&journal->j_list_lock);
267 if (unlikely(journal->j_flags & JBD2_UNMOUNT))
268 /*
269 * The journal thread is dead; so
270 * starting and waiting for a commit
271 * to finish will cause us to wait for
272 * a _very_ long time.
273 */
274 printk(KERN_ERR
275 "JBD2: %s: Waiting for Godot: block %llu\n",
276 journal->j_devname, (unsigned long long) bh->b_blocknr);
277
278 if (batch_count)
279 __flush_batch(journal, &batch_count);
280 jbd2_log_start_commit(journal, tid);
281 /*
282 * jbd2_journal_commit_transaction() may want
283 * to take the checkpoint_mutex if JBD2_FLUSHED
284 * is set, jbd2_update_log_tail() called by
285 * jbd2_journal_commit_transaction() may also take
286 * checkpoint_mutex. So we need to temporarily
287 * drop it.
288 */
289 mutex_unlock(&journal->j_checkpoint_mutex);
290 jbd2_log_wait_commit(journal, tid);
291 mutex_lock_io(&journal->j_checkpoint_mutex);
292 spin_lock(&journal->j_list_lock);
293 goto restart;
294 }
295 if (!buffer_dirty(bh)) {
296 if (unlikely(buffer_write_io_error(bh)) && !result)
297 result = -EIO;
298 BUFFER_TRACE(bh, "remove from checkpoint");
299 if (__jbd2_journal_remove_checkpoint(jh))
300 /* The transaction was released; we're done */
301 goto out;
302 continue;
303 }
304 /*
305 * Important: we are about to write the buffer, and
306 * possibly block, while still holding the journal
307 * lock. We cannot afford to let the transaction
308 * logic start messing around with this buffer before
309 * we write it to disk, as that would break
310 * recoverability.
311 */
312 BUFFER_TRACE(bh, "queue");
313 get_bh(bh);
314 J_ASSERT_BH(bh, !buffer_jwrite(bh));
315 journal->j_chkpt_bhs[batch_count++] = bh;
316 __buffer_relink_io(jh);
317 transaction->t_chp_stats.cs_written++;
318 if ((batch_count == JBD2_NR_BATCH) ||
319 need_resched() ||
320 spin_needbreak(&journal->j_list_lock))
321 goto unlock_and_flush;
322 }
323
324 if (batch_count) {
325 unlock_and_flush:
326 spin_unlock(&journal->j_list_lock);
327 retry:
328 if (batch_count)
329 __flush_batch(journal, &batch_count);
330 spin_lock(&journal->j_list_lock);
331 goto restart;
332 }
333
334 /*
335 * Now we issued all of the transaction's buffers, let's deal
336 * with the buffers that are out for I/O.
337 */
338restart2:
339 /* Did somebody clean up the transaction in the meanwhile? */
340 if (journal->j_checkpoint_transactions != transaction ||
341 transaction->t_tid != this_tid)
342 goto out;
343
344 while (transaction->t_checkpoint_io_list) {
345 jh = transaction->t_checkpoint_io_list;
346 bh = jh2bh(jh);
347 if (buffer_locked(bh)) {
348 get_bh(bh);
349 spin_unlock(&journal->j_list_lock);
350 wait_on_buffer(bh);
351 /* the journal_head may have gone by now */
352 BUFFER_TRACE(bh, "brelse");
353 __brelse(bh);
354 spin_lock(&journal->j_list_lock);
355 goto restart2;
356 }
357 if (unlikely(buffer_write_io_error(bh)) && !result)
358 result = -EIO;
359
360 /*
361 * Now in whatever state the buffer currently is, we
362 * know that it has been written out and so we can
363 * drop it from the list
364 */
365 if (__jbd2_journal_remove_checkpoint(jh))
366 break;
367 }
368out:
369 spin_unlock(&journal->j_list_lock);
370 if (result < 0)
371 jbd2_journal_abort(journal, result);
372 else
373 result = jbd2_cleanup_journal_tail(journal);
374
375 return (result < 0) ? result : 0;
376}
377
378/*
379 * Check the list of checkpoint transactions for the journal to see if
380 * we have already got rid of any since the last update of the log tail
381 * in the journal superblock. If so, we can instantly roll the
382 * superblock forward to remove those transactions from the log.
383 *
384 * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
385 *
386 * Called with the journal lock held.
387 *
388 * This is the only part of the journaling code which really needs to be
389 * aware of transaction aborts. Checkpointing involves writing to the
390 * main filesystem area rather than to the journal, so it can proceed
391 * even in abort state, but we must not update the super block if
392 * checkpointing may have failed. Otherwise, we would lose some metadata
393 * buffers which should be written-back to the filesystem.
394 */
395
396int jbd2_cleanup_journal_tail(journal_t *journal)
397{
398 tid_t first_tid;
399 unsigned long blocknr;
400
401 if (is_journal_aborted(journal))
402 return -EIO;
403
404 if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
405 return 1;
406 J_ASSERT(blocknr != 0);
407
408 /*
409 * We need to make sure that any blocks that were recently written out
410 * --- perhaps by jbd2_log_do_checkpoint() --- are flushed out before
411 * we drop the transactions from the journal. It's unlikely this will
412 * be necessary, especially with an appropriately sized journal, but we
413 * need this to guarantee correctness. Fortunately
414 * jbd2_cleanup_journal_tail() doesn't get called all that often.
415 */
416 if (journal->j_flags & JBD2_BARRIER)
417 blkdev_issue_flush(journal->j_fs_dev, GFP_NOFS);
418
419 return __jbd2_update_log_tail(journal, first_tid, blocknr);
420}
421
422
423/* Checkpoint list management */
424
425/*
426 * journal_clean_one_cp_list
427 *
428 * Find all the written-back checkpoint buffers in the given list and
429 * release them. If 'destroy' is set, clean all buffers unconditionally.
430 *
431 * Called with j_list_lock held.
432 * Returns 1 if we freed the transaction, 0 otherwise.
433 */
434static int journal_clean_one_cp_list(struct journal_head *jh, bool destroy)
435{
436 struct journal_head *last_jh;
437 struct journal_head *next_jh = jh;
438 int ret;
439
440 if (!jh)
441 return 0;
442
443 last_jh = jh->b_cpprev;
444 do {
445 jh = next_jh;
446 next_jh = jh->b_cpnext;
447 if (!destroy)
448 ret = __try_to_free_cp_buf(jh);
449 else
450 ret = __jbd2_journal_remove_checkpoint(jh) + 1;
451 if (!ret)
452 return 0;
453 if (ret == 2)
454 return 1;
455 /*
456 * This function only frees up some memory
457 * if possible so we dont have an obligation
458 * to finish processing. Bail out if preemption
459 * requested:
460 */
461 if (need_resched())
462 return 0;
463 } while (jh != last_jh);
464
465 return 0;
466}
467
468/*
469 * journal_clean_checkpoint_list
470 *
471 * Find all the written-back checkpoint buffers in the journal and release them.
472 * If 'destroy' is set, release all buffers unconditionally.
473 *
474 * Called with j_list_lock held.
475 */
476void __jbd2_journal_clean_checkpoint_list(journal_t *journal, bool destroy)
477{
478 transaction_t *transaction, *last_transaction, *next_transaction;
479 int ret;
480
481 transaction = journal->j_checkpoint_transactions;
482 if (!transaction)
483 return;
484
485 last_transaction = transaction->t_cpprev;
486 next_transaction = transaction;
487 do {
488 transaction = next_transaction;
489 next_transaction = transaction->t_cpnext;
490 ret = journal_clean_one_cp_list(transaction->t_checkpoint_list,
491 destroy);
492 /*
493 * This function only frees up some memory if possible so we
494 * dont have an obligation to finish processing. Bail out if
495 * preemption requested:
496 */
497 if (need_resched())
498 return;
499 if (ret)
500 continue;
501 /*
502 * It is essential that we are as careful as in the case of
503 * t_checkpoint_list with removing the buffer from the list as
504 * we can possibly see not yet submitted buffers on io_list
505 */
506 ret = journal_clean_one_cp_list(transaction->
507 t_checkpoint_io_list, destroy);
508 if (need_resched())
509 return;
510 /*
511 * Stop scanning if we couldn't free the transaction. This
512 * avoids pointless scanning of transactions which still
513 * weren't checkpointed.
514 */
515 if (!ret)
516 return;
517 } while (transaction != last_transaction);
518}
519
520/*
521 * Remove buffers from all checkpoint lists as journal is aborted and we just
522 * need to free memory
523 */
524void jbd2_journal_destroy_checkpoint(journal_t *journal)
525{
526 /*
527 * We loop because __jbd2_journal_clean_checkpoint_list() may abort
528 * early due to a need of rescheduling.
529 */
530 while (1) {
531 spin_lock(&journal->j_list_lock);
532 if (!journal->j_checkpoint_transactions) {
533 spin_unlock(&journal->j_list_lock);
534 break;
535 }
536 __jbd2_journal_clean_checkpoint_list(journal, true);
537 spin_unlock(&journal->j_list_lock);
538 cond_resched();
539 }
540}
541
542/*
543 * journal_remove_checkpoint: called after a buffer has been committed
544 * to disk (either by being write-back flushed to disk, or being
545 * committed to the log).
546 *
547 * We cannot safely clean a transaction out of the log until all of the
548 * buffer updates committed in that transaction have safely been stored
549 * elsewhere on disk. To achieve this, all of the buffers in a
550 * transaction need to be maintained on the transaction's checkpoint
551 * lists until they have been rewritten, at which point this function is
552 * called to remove the buffer from the existing transaction's
553 * checkpoint lists.
554 *
555 * The function returns 1 if it frees the transaction, 0 otherwise.
556 * The function can free jh and bh.
557 *
558 * This function is called with j_list_lock held.
559 */
560int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
561{
562 struct transaction_chp_stats_s *stats;
563 transaction_t *transaction;
564 journal_t *journal;
565 int ret = 0;
566
567 JBUFFER_TRACE(jh, "entry");
568
569 if ((transaction = jh->b_cp_transaction) == NULL) {
570 JBUFFER_TRACE(jh, "not on transaction");
571 goto out;
572 }
573 journal = transaction->t_journal;
574
575 JBUFFER_TRACE(jh, "removing from transaction");
576 __buffer_unlink(jh);
577 jh->b_cp_transaction = NULL;
578 jbd2_journal_put_journal_head(jh);
579
580 if (transaction->t_checkpoint_list != NULL ||
581 transaction->t_checkpoint_io_list != NULL)
582 goto out;
583
584 /*
585 * There is one special case to worry about: if we have just pulled the
586 * buffer off a running or committing transaction's checkpoing list,
587 * then even if the checkpoint list is empty, the transaction obviously
588 * cannot be dropped!
589 *
590 * The locking here around t_state is a bit sleazy.
591 * See the comment at the end of jbd2_journal_commit_transaction().
592 */
593 if (transaction->t_state != T_FINISHED)
594 goto out;
595
596 /* OK, that was the last buffer for the transaction: we can now
597 safely remove this transaction from the log */
598 stats = &transaction->t_chp_stats;
599 if (stats->cs_chp_time)
600 stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
601 jiffies);
602 trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
603 transaction->t_tid, stats);
604
605 __jbd2_journal_drop_transaction(journal, transaction);
606 jbd2_journal_free_transaction(transaction);
607 ret = 1;
608out:
609 return ret;
610}
611
612/*
613 * journal_insert_checkpoint: put a committed buffer onto a checkpoint
614 * list so that we know when it is safe to clean the transaction out of
615 * the log.
616 *
617 * Called with the journal locked.
618 * Called with j_list_lock held.
619 */
620void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
621 transaction_t *transaction)
622{
623 JBUFFER_TRACE(jh, "entry");
624 J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
625 J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
626
627 /* Get reference for checkpointing transaction */
628 jbd2_journal_grab_journal_head(jh2bh(jh));
629 jh->b_cp_transaction = transaction;
630
631 if (!transaction->t_checkpoint_list) {
632 jh->b_cpnext = jh->b_cpprev = jh;
633 } else {
634 jh->b_cpnext = transaction->t_checkpoint_list;
635 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
636 jh->b_cpprev->b_cpnext = jh;
637 jh->b_cpnext->b_cpprev = jh;
638 }
639 transaction->t_checkpoint_list = jh;
640}
641
642/*
643 * We've finished with this transaction structure: adios...
644 *
645 * The transaction must have no links except for the checkpoint by this
646 * point.
647 *
648 * Called with the journal locked.
649 * Called with j_list_lock held.
650 */
651
652void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
653{
654 assert_spin_locked(&journal->j_list_lock);
655 if (transaction->t_cpnext) {
656 transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
657 transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
658 if (journal->j_checkpoint_transactions == transaction)
659 journal->j_checkpoint_transactions =
660 transaction->t_cpnext;
661 if (journal->j_checkpoint_transactions == transaction)
662 journal->j_checkpoint_transactions = NULL;
663 }
664
665 J_ASSERT(transaction->t_state == T_FINISHED);
666 J_ASSERT(transaction->t_buffers == NULL);
667 J_ASSERT(transaction->t_forget == NULL);
668 J_ASSERT(transaction->t_shadow_list == NULL);
669 J_ASSERT(transaction->t_checkpoint_list == NULL);
670 J_ASSERT(transaction->t_checkpoint_io_list == NULL);
671 J_ASSERT(atomic_read(&transaction->t_updates) == 0);
672 J_ASSERT(journal->j_committing_transaction != transaction);
673 J_ASSERT(journal->j_running_transaction != transaction);
674
675 trace_jbd2_drop_transaction(journal, transaction);
676
677 jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
678}