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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/*
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 = jbd2_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 = jbd2_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 /*
160 * jbd2_journal_commit_transaction() may want
161 * to take the checkpoint_mutex if JBD2_FLUSHED
162 * is set. So we need to temporarily drop it.
163 */
164 mutex_unlock(&journal->j_checkpoint_mutex);
165 jbd2_log_wait_commit(journal, tid);
166 write_lock(&journal->j_state_lock);
167 continue;
168 } else {
169 printk(KERN_ERR "%s: needed %d blocks and "
170 "only had %d space available\n",
171 __func__, nblocks, space_left);
172 printk(KERN_ERR "%s: no way to get more "
173 "journal space in %s\n", __func__,
174 journal->j_devname);
175 WARN_ON(1);
176 jbd2_journal_abort(journal, 0);
177 }
178 write_lock(&journal->j_state_lock);
179 } else {
180 spin_unlock(&journal->j_list_lock);
181 }
182 mutex_unlock(&journal->j_checkpoint_mutex);
183 }
184}
185
186/*
187 * Clean up transaction's list of buffers submitted for io.
188 * We wait for any pending IO to complete and remove any clean
189 * buffers. Note that we take the buffers in the opposite ordering
190 * from the one in which they were submitted for IO.
191 *
192 * Return 0 on success, and return <0 if some buffers have failed
193 * to be written out.
194 *
195 * Called with j_list_lock held.
196 */
197static int __wait_cp_io(journal_t *journal, transaction_t *transaction)
198{
199 struct journal_head *jh;
200 struct buffer_head *bh;
201 tid_t this_tid;
202 int released = 0;
203 int ret = 0;
204
205 this_tid = transaction->t_tid;
206restart:
207 /* Did somebody clean up the transaction in the meanwhile? */
208 if (journal->j_checkpoint_transactions != transaction ||
209 transaction->t_tid != this_tid)
210 return ret;
211 while (!released && transaction->t_checkpoint_io_list) {
212 jh = transaction->t_checkpoint_io_list;
213 bh = jh2bh(jh);
214 get_bh(bh);
215 if (buffer_locked(bh)) {
216 spin_unlock(&journal->j_list_lock);
217 wait_on_buffer(bh);
218 /* the journal_head may have gone by now */
219 BUFFER_TRACE(bh, "brelse");
220 __brelse(bh);
221 spin_lock(&journal->j_list_lock);
222 goto restart;
223 }
224 if (unlikely(buffer_write_io_error(bh)))
225 ret = -EIO;
226
227 /*
228 * Now in whatever state the buffer currently is, we know that
229 * it has been written out and so we can drop it from the list
230 */
231 released = __jbd2_journal_remove_checkpoint(jh);
232 __brelse(bh);
233 }
234
235 return ret;
236}
237
238static void
239__flush_batch(journal_t *journal, int *batch_count)
240{
241 int i;
242 struct blk_plug plug;
243
244 blk_start_plug(&plug);
245 for (i = 0; i < *batch_count; i++)
246 write_dirty_buffer(journal->j_chkpt_bhs[i], WRITE_SYNC);
247 blk_finish_plug(&plug);
248
249 for (i = 0; i < *batch_count; i++) {
250 struct buffer_head *bh = journal->j_chkpt_bhs[i];
251 BUFFER_TRACE(bh, "brelse");
252 __brelse(bh);
253 }
254 *batch_count = 0;
255}
256
257/*
258 * Try to flush one buffer from the checkpoint list to disk.
259 *
260 * Return 1 if something happened which requires us to abort the current
261 * scan of the checkpoint list. Return <0 if the buffer has failed to
262 * be written out.
263 *
264 * Called with j_list_lock held and drops it if 1 is returned
265 */
266static int __process_buffer(journal_t *journal, struct journal_head *jh,
267 int *batch_count, transaction_t *transaction)
268{
269 struct buffer_head *bh = jh2bh(jh);
270 int ret = 0;
271
272 if (buffer_locked(bh)) {
273 get_bh(bh);
274 spin_unlock(&journal->j_list_lock);
275 wait_on_buffer(bh);
276 /* the journal_head may have gone by now */
277 BUFFER_TRACE(bh, "brelse");
278 __brelse(bh);
279 ret = 1;
280 } else if (jh->b_transaction != NULL) {
281 transaction_t *t = jh->b_transaction;
282 tid_t tid = t->t_tid;
283
284 transaction->t_chp_stats.cs_forced_to_close++;
285 spin_unlock(&journal->j_list_lock);
286 if (unlikely(journal->j_flags & JBD2_UNMOUNT))
287 /*
288 * The journal thread is dead; so starting and
289 * waiting for a commit to finish will cause
290 * us to wait for a _very_ long time.
291 */
292 printk(KERN_ERR "JBD2: %s: "
293 "Waiting for Godot: block %llu\n",
294 journal->j_devname,
295 (unsigned long long) bh->b_blocknr);
296 jbd2_log_start_commit(journal, tid);
297 jbd2_log_wait_commit(journal, tid);
298 ret = 1;
299 } else if (!buffer_dirty(bh)) {
300 ret = 1;
301 if (unlikely(buffer_write_io_error(bh)))
302 ret = -EIO;
303 get_bh(bh);
304 BUFFER_TRACE(bh, "remove from checkpoint");
305 __jbd2_journal_remove_checkpoint(jh);
306 spin_unlock(&journal->j_list_lock);
307 __brelse(bh);
308 } else {
309 /*
310 * Important: we are about to write the buffer, and
311 * possibly block, while still holding the journal lock.
312 * We cannot afford to let the transaction logic start
313 * messing around with this buffer before we write it to
314 * disk, as that would break recoverability.
315 */
316 BUFFER_TRACE(bh, "queue");
317 get_bh(bh);
318 J_ASSERT_BH(bh, !buffer_jwrite(bh));
319 journal->j_chkpt_bhs[*batch_count] = bh;
320 __buffer_relink_io(jh);
321 transaction->t_chp_stats.cs_written++;
322 (*batch_count)++;
323 if (*batch_count == JBD2_NR_BATCH) {
324 spin_unlock(&journal->j_list_lock);
325 __flush_batch(journal, batch_count);
326 ret = 1;
327 }
328 }
329 return ret;
330}
331
332/*
333 * Perform an actual checkpoint. We take the first transaction on the
334 * list of transactions to be checkpointed and send all its buffers
335 * to disk. We submit larger chunks of data at once.
336 *
337 * The journal should be locked before calling this function.
338 * Called with j_checkpoint_mutex held.
339 */
340int jbd2_log_do_checkpoint(journal_t *journal)
341{
342 transaction_t *transaction;
343 tid_t this_tid;
344 int result;
345
346 jbd_debug(1, "Start checkpoint\n");
347
348 /*
349 * First thing: if there are any transactions in the log which
350 * don't need checkpointing, just eliminate them from the
351 * journal straight away.
352 */
353 result = jbd2_cleanup_journal_tail(journal);
354 trace_jbd2_checkpoint(journal, result);
355 jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
356 if (result <= 0)
357 return result;
358
359 /*
360 * OK, we need to start writing disk blocks. Take one transaction
361 * and write it.
362 */
363 result = 0;
364 spin_lock(&journal->j_list_lock);
365 if (!journal->j_checkpoint_transactions)
366 goto out;
367 transaction = journal->j_checkpoint_transactions;
368 if (transaction->t_chp_stats.cs_chp_time == 0)
369 transaction->t_chp_stats.cs_chp_time = jiffies;
370 this_tid = transaction->t_tid;
371restart:
372 /*
373 * If someone cleaned up this transaction while we slept, we're
374 * done (maybe it's a new transaction, but it fell at the same
375 * address).
376 */
377 if (journal->j_checkpoint_transactions == transaction &&
378 transaction->t_tid == this_tid) {
379 int batch_count = 0;
380 struct journal_head *jh;
381 int retry = 0, err;
382
383 while (!retry && transaction->t_checkpoint_list) {
384 jh = transaction->t_checkpoint_list;
385 retry = __process_buffer(journal, jh, &batch_count,
386 transaction);
387 if (retry < 0 && !result)
388 result = retry;
389 if (!retry && (need_resched() ||
390 spin_needbreak(&journal->j_list_lock))) {
391 spin_unlock(&journal->j_list_lock);
392 retry = 1;
393 break;
394 }
395 }
396
397 if (batch_count) {
398 if (!retry) {
399 spin_unlock(&journal->j_list_lock);
400 retry = 1;
401 }
402 __flush_batch(journal, &batch_count);
403 }
404
405 if (retry) {
406 spin_lock(&journal->j_list_lock);
407 goto restart;
408 }
409 /*
410 * Now we have cleaned up the first transaction's checkpoint
411 * list. Let's clean up the second one
412 */
413 err = __wait_cp_io(journal, transaction);
414 if (!result)
415 result = err;
416 }
417out:
418 spin_unlock(&journal->j_list_lock);
419 if (result < 0)
420 jbd2_journal_abort(journal, result);
421 else
422 result = jbd2_cleanup_journal_tail(journal);
423
424 return (result < 0) ? result : 0;
425}
426
427/*
428 * Check the list of checkpoint transactions for the journal to see if
429 * we have already got rid of any since the last update of the log tail
430 * in the journal superblock. If so, we can instantly roll the
431 * superblock forward to remove those transactions from the log.
432 *
433 * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
434 *
435 * Called with the journal lock held.
436 *
437 * This is the only part of the journaling code which really needs to be
438 * aware of transaction aborts. Checkpointing involves writing to the
439 * main filesystem area rather than to the journal, so it can proceed
440 * even in abort state, but we must not update the super block if
441 * checkpointing may have failed. Otherwise, we would lose some metadata
442 * buffers which should be written-back to the filesystem.
443 */
444
445int jbd2_cleanup_journal_tail(journal_t *journal)
446{
447 tid_t first_tid;
448 unsigned long blocknr;
449
450 if (is_journal_aborted(journal))
451 return 1;
452
453 if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
454 return 1;
455 J_ASSERT(blocknr != 0);
456
457 /*
458 * We need to make sure that any blocks that were recently written out
459 * --- perhaps by jbd2_log_do_checkpoint() --- are flushed out before
460 * we drop the transactions from the journal. It's unlikely this will
461 * be necessary, especially with an appropriately sized journal, but we
462 * need this to guarantee correctness. Fortunately
463 * jbd2_cleanup_journal_tail() doesn't get called all that often.
464 */
465 if (journal->j_flags & JBD2_BARRIER)
466 blkdev_issue_flush(journal->j_fs_dev, GFP_KERNEL, NULL);
467
468 __jbd2_update_log_tail(journal, first_tid, blocknr);
469 return 0;
470}
471
472
473/* Checkpoint list management */
474
475/*
476 * journal_clean_one_cp_list
477 *
478 * Find all the written-back checkpoint buffers in the given list and
479 * release them.
480 *
481 * Called with the journal locked.
482 * Called with j_list_lock held.
483 * Returns number of buffers reaped (for debug)
484 */
485
486static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
487{
488 struct journal_head *last_jh;
489 struct journal_head *next_jh = jh;
490 int ret, freed = 0;
491
492 *released = 0;
493 if (!jh)
494 return 0;
495
496 last_jh = jh->b_cpprev;
497 do {
498 jh = next_jh;
499 next_jh = jh->b_cpnext;
500 ret = __try_to_free_cp_buf(jh);
501 if (ret) {
502 freed++;
503 if (ret == 2) {
504 *released = 1;
505 return freed;
506 }
507 }
508 /*
509 * This function only frees up some memory
510 * if possible so we dont have an obligation
511 * to finish processing. Bail out if preemption
512 * requested:
513 */
514 if (need_resched())
515 return freed;
516 } while (jh != last_jh);
517
518 return freed;
519}
520
521/*
522 * journal_clean_checkpoint_list
523 *
524 * Find all the written-back checkpoint buffers in the journal and release them.
525 *
526 * Called with the journal locked.
527 * Called with j_list_lock held.
528 * Returns number of buffers reaped (for debug)
529 */
530
531int __jbd2_journal_clean_checkpoint_list(journal_t *journal)
532{
533 transaction_t *transaction, *last_transaction, *next_transaction;
534 int ret = 0;
535 int released;
536
537 transaction = journal->j_checkpoint_transactions;
538 if (!transaction)
539 goto out;
540
541 last_transaction = transaction->t_cpprev;
542 next_transaction = transaction;
543 do {
544 transaction = next_transaction;
545 next_transaction = transaction->t_cpnext;
546 ret += journal_clean_one_cp_list(transaction->
547 t_checkpoint_list, &released);
548 /*
549 * This function only frees up some memory if possible so we
550 * dont have an obligation to finish processing. Bail out if
551 * preemption requested:
552 */
553 if (need_resched())
554 goto out;
555 if (released)
556 continue;
557 /*
558 * It is essential that we are as careful as in the case of
559 * t_checkpoint_list with removing the buffer from the list as
560 * we can possibly see not yet submitted buffers on io_list
561 */
562 ret += journal_clean_one_cp_list(transaction->
563 t_checkpoint_io_list, &released);
564 if (need_resched())
565 goto out;
566 } while (transaction != last_transaction);
567out:
568 return ret;
569}
570
571/*
572 * journal_remove_checkpoint: called after a buffer has been committed
573 * to disk (either by being write-back flushed to disk, or being
574 * committed to the log).
575 *
576 * We cannot safely clean a transaction out of the log until all of the
577 * buffer updates committed in that transaction have safely been stored
578 * elsewhere on disk. To achieve this, all of the buffers in a
579 * transaction need to be maintained on the transaction's checkpoint
580 * lists until they have been rewritten, at which point this function is
581 * called to remove the buffer from the existing transaction's
582 * checkpoint lists.
583 *
584 * The function returns 1 if it frees the transaction, 0 otherwise.
585 * The function can free jh and bh.
586 *
587 * This function is called with j_list_lock held.
588 */
589int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
590{
591 struct transaction_chp_stats_s *stats;
592 transaction_t *transaction;
593 journal_t *journal;
594 int ret = 0;
595
596 JBUFFER_TRACE(jh, "entry");
597
598 if ((transaction = jh->b_cp_transaction) == NULL) {
599 JBUFFER_TRACE(jh, "not on transaction");
600 goto out;
601 }
602 journal = transaction->t_journal;
603
604 JBUFFER_TRACE(jh, "removing from transaction");
605 __buffer_unlink(jh);
606 jh->b_cp_transaction = NULL;
607 jbd2_journal_put_journal_head(jh);
608
609 if (transaction->t_checkpoint_list != NULL ||
610 transaction->t_checkpoint_io_list != NULL)
611 goto out;
612
613 /*
614 * There is one special case to worry about: if we have just pulled the
615 * buffer off a running or committing transaction's checkpoing list,
616 * then even if the checkpoint list is empty, the transaction obviously
617 * cannot be dropped!
618 *
619 * The locking here around t_state is a bit sleazy.
620 * See the comment at the end of jbd2_journal_commit_transaction().
621 */
622 if (transaction->t_state != T_FINISHED)
623 goto out;
624
625 /* OK, that was the last buffer for the transaction: we can now
626 safely remove this transaction from the log */
627 stats = &transaction->t_chp_stats;
628 if (stats->cs_chp_time)
629 stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
630 jiffies);
631 trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
632 transaction->t_tid, stats);
633
634 __jbd2_journal_drop_transaction(journal, transaction);
635 jbd2_journal_free_transaction(transaction);
636 ret = 1;
637out:
638 return ret;
639}
640
641/*
642 * journal_insert_checkpoint: put a committed buffer onto a checkpoint
643 * list so that we know when it is safe to clean the transaction out of
644 * the log.
645 *
646 * Called with the journal locked.
647 * Called with j_list_lock held.
648 */
649void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
650 transaction_t *transaction)
651{
652 JBUFFER_TRACE(jh, "entry");
653 J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
654 J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
655
656 /* Get reference for checkpointing transaction */
657 jbd2_journal_grab_journal_head(jh2bh(jh));
658 jh->b_cp_transaction = transaction;
659
660 if (!transaction->t_checkpoint_list) {
661 jh->b_cpnext = jh->b_cpprev = jh;
662 } else {
663 jh->b_cpnext = transaction->t_checkpoint_list;
664 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
665 jh->b_cpprev->b_cpnext = jh;
666 jh->b_cpnext->b_cpprev = jh;
667 }
668 transaction->t_checkpoint_list = jh;
669}
670
671/*
672 * We've finished with this transaction structure: adios...
673 *
674 * The transaction must have no links except for the checkpoint by this
675 * point.
676 *
677 * Called with the journal locked.
678 * Called with j_list_lock held.
679 */
680
681void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
682{
683 assert_spin_locked(&journal->j_list_lock);
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(transaction->t_checkpoint_io_list == NULL);
700 J_ASSERT(atomic_read(&transaction->t_updates) == 0);
701 J_ASSERT(journal->j_committing_transaction != transaction);
702 J_ASSERT(journal->j_running_transaction != transaction);
703
704 trace_jbd2_drop_transaction(journal, transaction);
705
706 jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
707}