Loading...
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 JBUFFER_TRACE(jh, "remove from checkpoint list");
100 ret = __jbd2_journal_remove_checkpoint(jh) + 1;
101 }
102 return ret;
103}
104
105/*
106 * __jbd2_log_wait_for_space: wait until there is space in the journal.
107 *
108 * Called under j-state_lock *only*. It will be unlocked if we have to wait
109 * for a checkpoint to free up some space in the log.
110 */
111void __jbd2_log_wait_for_space(journal_t *journal)
112{
113 int nblocks, space_left;
114 /* assert_spin_locked(&journal->j_state_lock); */
115
116 nblocks = jbd2_space_needed(journal);
117 while (jbd2_log_space_left(journal) < nblocks) {
118 write_unlock(&journal->j_state_lock);
119 mutex_lock(&journal->j_checkpoint_mutex);
120
121 /*
122 * Test again, another process may have checkpointed while we
123 * were waiting for the checkpoint lock. If there are no
124 * transactions ready to be checkpointed, try to recover
125 * journal space by calling cleanup_journal_tail(), and if
126 * that doesn't work, by waiting for the currently committing
127 * transaction to complete. If there is absolutely no way
128 * to make progress, this is either a BUG or corrupted
129 * filesystem, so abort the journal and leave a stack
130 * trace for forensic evidence.
131 */
132 write_lock(&journal->j_state_lock);
133 if (journal->j_flags & JBD2_ABORT) {
134 mutex_unlock(&journal->j_checkpoint_mutex);
135 return;
136 }
137 spin_lock(&journal->j_list_lock);
138 nblocks = jbd2_space_needed(journal);
139 space_left = jbd2_log_space_left(journal);
140 if (space_left < nblocks) {
141 int chkpt = journal->j_checkpoint_transactions != NULL;
142 tid_t tid = 0;
143
144 if (journal->j_committing_transaction)
145 tid = journal->j_committing_transaction->t_tid;
146 spin_unlock(&journal->j_list_lock);
147 write_unlock(&journal->j_state_lock);
148 if (chkpt) {
149 jbd2_log_do_checkpoint(journal);
150 } else if (jbd2_cleanup_journal_tail(journal) == 0) {
151 /* We were able to recover space; yay! */
152 ;
153 } else if (tid) {
154 /*
155 * jbd2_journal_commit_transaction() may want
156 * to take the checkpoint_mutex if JBD2_FLUSHED
157 * is set. So we need to temporarily drop it.
158 */
159 mutex_unlock(&journal->j_checkpoint_mutex);
160 jbd2_log_wait_commit(journal, tid);
161 write_lock(&journal->j_state_lock);
162 continue;
163 } else {
164 printk(KERN_ERR "%s: needed %d blocks and "
165 "only had %d space available\n",
166 __func__, nblocks, space_left);
167 printk(KERN_ERR "%s: no way to get more "
168 "journal space in %s\n", __func__,
169 journal->j_devname);
170 WARN_ON(1);
171 jbd2_journal_abort(journal, 0);
172 }
173 write_lock(&journal->j_state_lock);
174 } else {
175 spin_unlock(&journal->j_list_lock);
176 }
177 mutex_unlock(&journal->j_checkpoint_mutex);
178 }
179}
180
181static void
182__flush_batch(journal_t *journal, int *batch_count)
183{
184 int i;
185 struct blk_plug plug;
186
187 blk_start_plug(&plug);
188 for (i = 0; i < *batch_count; i++)
189 write_dirty_buffer(journal->j_chkpt_bhs[i], WRITE_SYNC);
190 blk_finish_plug(&plug);
191
192 for (i = 0; i < *batch_count; i++) {
193 struct buffer_head *bh = journal->j_chkpt_bhs[i];
194 BUFFER_TRACE(bh, "brelse");
195 __brelse(bh);
196 }
197 *batch_count = 0;
198}
199
200/*
201 * Perform an actual checkpoint. We take the first transaction on the
202 * list of transactions to be checkpointed and send all its buffers
203 * to disk. We submit larger chunks of data at once.
204 *
205 * The journal should be locked before calling this function.
206 * Called with j_checkpoint_mutex held.
207 */
208int jbd2_log_do_checkpoint(journal_t *journal)
209{
210 struct journal_head *jh;
211 struct buffer_head *bh;
212 transaction_t *transaction;
213 tid_t this_tid;
214 int result, batch_count = 0;
215
216 jbd_debug(1, "Start checkpoint\n");
217
218 /*
219 * First thing: if there are any transactions in the log which
220 * don't need checkpointing, just eliminate them from the
221 * journal straight away.
222 */
223 result = jbd2_cleanup_journal_tail(journal);
224 trace_jbd2_checkpoint(journal, result);
225 jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
226 if (result <= 0)
227 return result;
228
229 /*
230 * OK, we need to start writing disk blocks. Take one transaction
231 * and write it.
232 */
233 result = 0;
234 spin_lock(&journal->j_list_lock);
235 if (!journal->j_checkpoint_transactions)
236 goto out;
237 transaction = journal->j_checkpoint_transactions;
238 if (transaction->t_chp_stats.cs_chp_time == 0)
239 transaction->t_chp_stats.cs_chp_time = jiffies;
240 this_tid = transaction->t_tid;
241restart:
242 /*
243 * If someone cleaned up this transaction while we slept, we're
244 * done (maybe it's a new transaction, but it fell at the same
245 * address).
246 */
247 if (journal->j_checkpoint_transactions != transaction ||
248 transaction->t_tid != this_tid)
249 goto out;
250
251 /* checkpoint all of the transaction's buffers */
252 while (transaction->t_checkpoint_list) {
253 jh = transaction->t_checkpoint_list;
254 bh = jh2bh(jh);
255
256 if (buffer_locked(bh)) {
257 spin_unlock(&journal->j_list_lock);
258 get_bh(bh);
259 wait_on_buffer(bh);
260 /* the journal_head may have gone by now */
261 BUFFER_TRACE(bh, "brelse");
262 __brelse(bh);
263 goto retry;
264 }
265 if (jh->b_transaction != NULL) {
266 transaction_t *t = jh->b_transaction;
267 tid_t tid = t->t_tid;
268
269 transaction->t_chp_stats.cs_forced_to_close++;
270 spin_unlock(&journal->j_list_lock);
271 if (unlikely(journal->j_flags & JBD2_UNMOUNT))
272 /*
273 * The journal thread is dead; so
274 * starting and waiting for a commit
275 * to finish will cause us to wait for
276 * a _very_ long time.
277 */
278 printk(KERN_ERR
279 "JBD2: %s: Waiting for Godot: block %llu\n",
280 journal->j_devname, (unsigned long long) bh->b_blocknr);
281
282 jbd2_log_start_commit(journal, tid);
283 jbd2_log_wait_commit(journal, tid);
284 goto retry;
285 }
286 if (!buffer_dirty(bh)) {
287 if (unlikely(buffer_write_io_error(bh)) && !result)
288 result = -EIO;
289 BUFFER_TRACE(bh, "remove from checkpoint");
290 if (__jbd2_journal_remove_checkpoint(jh))
291 /* The transaction was released; we're done */
292 goto out;
293 continue;
294 }
295 /*
296 * Important: we are about to write the buffer, and
297 * possibly block, while still holding the journal
298 * lock. We cannot afford to let the transaction
299 * logic start messing around with this buffer before
300 * we write it to disk, as that would break
301 * recoverability.
302 */
303 BUFFER_TRACE(bh, "queue");
304 get_bh(bh);
305 J_ASSERT_BH(bh, !buffer_jwrite(bh));
306 journal->j_chkpt_bhs[batch_count++] = bh;
307 __buffer_relink_io(jh);
308 transaction->t_chp_stats.cs_written++;
309 if ((batch_count == JBD2_NR_BATCH) ||
310 need_resched() ||
311 spin_needbreak(&journal->j_list_lock))
312 goto unlock_and_flush;
313 }
314
315 if (batch_count) {
316 unlock_and_flush:
317 spin_unlock(&journal->j_list_lock);
318 retry:
319 if (batch_count)
320 __flush_batch(journal, &batch_count);
321 spin_lock(&journal->j_list_lock);
322 goto restart;
323 }
324
325 /*
326 * Now we issued all of the transaction's buffers, let's deal
327 * with the buffers that are out for I/O.
328 */
329restart2:
330 /* Did somebody clean up the transaction in the meanwhile? */
331 if (journal->j_checkpoint_transactions != transaction ||
332 transaction->t_tid != this_tid)
333 goto out;
334
335 while (transaction->t_checkpoint_io_list) {
336 jh = transaction->t_checkpoint_io_list;
337 bh = jh2bh(jh);
338 if (buffer_locked(bh)) {
339 spin_unlock(&journal->j_list_lock);
340 get_bh(bh);
341 wait_on_buffer(bh);
342 /* the journal_head may have gone by now */
343 BUFFER_TRACE(bh, "brelse");
344 __brelse(bh);
345 spin_lock(&journal->j_list_lock);
346 goto restart2;
347 }
348 if (unlikely(buffer_write_io_error(bh)) && !result)
349 result = -EIO;
350
351 /*
352 * Now in whatever state the buffer currently is, we
353 * know that it has been written out and so we can
354 * drop it from the list
355 */
356 if (__jbd2_journal_remove_checkpoint(jh))
357 break;
358 }
359out:
360 spin_unlock(&journal->j_list_lock);
361 if (result < 0)
362 jbd2_journal_abort(journal, result);
363 else
364 result = jbd2_cleanup_journal_tail(journal);
365
366 return (result < 0) ? result : 0;
367}
368
369/*
370 * Check the list of checkpoint transactions for the journal to see if
371 * we have already got rid of any since the last update of the log tail
372 * in the journal superblock. If so, we can instantly roll the
373 * superblock forward to remove those transactions from the log.
374 *
375 * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
376 *
377 * Called with the journal lock held.
378 *
379 * This is the only part of the journaling code which really needs to be
380 * aware of transaction aborts. Checkpointing involves writing to the
381 * main filesystem area rather than to the journal, so it can proceed
382 * even in abort state, but we must not update the super block if
383 * checkpointing may have failed. Otherwise, we would lose some metadata
384 * buffers which should be written-back to the filesystem.
385 */
386
387int jbd2_cleanup_journal_tail(journal_t *journal)
388{
389 tid_t first_tid;
390 unsigned long blocknr;
391
392 if (is_journal_aborted(journal))
393 return -EIO;
394
395 if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
396 return 1;
397 J_ASSERT(blocknr != 0);
398
399 /*
400 * We need to make sure that any blocks that were recently written out
401 * --- perhaps by jbd2_log_do_checkpoint() --- are flushed out before
402 * we drop the transactions from the journal. It's unlikely this will
403 * be necessary, especially with an appropriately sized journal, but we
404 * need this to guarantee correctness. Fortunately
405 * jbd2_cleanup_journal_tail() doesn't get called all that often.
406 */
407 if (journal->j_flags & JBD2_BARRIER)
408 blkdev_issue_flush(journal->j_fs_dev, GFP_NOFS, NULL);
409
410 return __jbd2_update_log_tail(journal, first_tid, blocknr);
411}
412
413
414/* Checkpoint list management */
415
416/*
417 * journal_clean_one_cp_list
418 *
419 * Find all the written-back checkpoint buffers in the given list and
420 * release them. If 'destroy' is set, clean all buffers unconditionally.
421 *
422 * Called with j_list_lock held.
423 * Returns 1 if we freed the transaction, 0 otherwise.
424 */
425static int journal_clean_one_cp_list(struct journal_head *jh, bool destroy)
426{
427 struct journal_head *last_jh;
428 struct journal_head *next_jh = jh;
429 int ret;
430
431 if (!jh)
432 return 0;
433
434 last_jh = jh->b_cpprev;
435 do {
436 jh = next_jh;
437 next_jh = jh->b_cpnext;
438 if (!destroy)
439 ret = __try_to_free_cp_buf(jh);
440 else
441 ret = __jbd2_journal_remove_checkpoint(jh) + 1;
442 if (!ret)
443 return 0;
444 if (ret == 2)
445 return 1;
446 /*
447 * This function only frees up some memory
448 * if possible so we dont have an obligation
449 * to finish processing. Bail out if preemption
450 * requested:
451 */
452 if (need_resched())
453 return 0;
454 } while (jh != last_jh);
455
456 return 0;
457}
458
459/*
460 * journal_clean_checkpoint_list
461 *
462 * Find all the written-back checkpoint buffers in the journal and release them.
463 * If 'destroy' is set, release all buffers unconditionally.
464 *
465 * Called with j_list_lock held.
466 */
467void __jbd2_journal_clean_checkpoint_list(journal_t *journal, bool destroy)
468{
469 transaction_t *transaction, *last_transaction, *next_transaction;
470 int ret;
471
472 transaction = journal->j_checkpoint_transactions;
473 if (!transaction)
474 return;
475
476 last_transaction = transaction->t_cpprev;
477 next_transaction = transaction;
478 do {
479 transaction = next_transaction;
480 next_transaction = transaction->t_cpnext;
481 ret = journal_clean_one_cp_list(transaction->t_checkpoint_list,
482 destroy);
483 /*
484 * This function only frees up some memory if possible so we
485 * dont have an obligation to finish processing. Bail out if
486 * preemption requested:
487 */
488 if (need_resched())
489 return;
490 if (ret)
491 continue;
492 /*
493 * It is essential that we are as careful as in the case of
494 * t_checkpoint_list with removing the buffer from the list as
495 * we can possibly see not yet submitted buffers on io_list
496 */
497 ret = journal_clean_one_cp_list(transaction->
498 t_checkpoint_io_list, destroy);
499 if (need_resched())
500 return;
501 /*
502 * Stop scanning if we couldn't free the transaction. This
503 * avoids pointless scanning of transactions which still
504 * weren't checkpointed.
505 */
506 if (!ret)
507 return;
508 } while (transaction != last_transaction);
509}
510
511/*
512 * Remove buffers from all checkpoint lists as journal is aborted and we just
513 * need to free memory
514 */
515void jbd2_journal_destroy_checkpoint(journal_t *journal)
516{
517 /*
518 * We loop because __jbd2_journal_clean_checkpoint_list() may abort
519 * early due to a need of rescheduling.
520 */
521 while (1) {
522 spin_lock(&journal->j_list_lock);
523 if (!journal->j_checkpoint_transactions) {
524 spin_unlock(&journal->j_list_lock);
525 break;
526 }
527 __jbd2_journal_clean_checkpoint_list(journal, true);
528 spin_unlock(&journal->j_list_lock);
529 cond_resched();
530 }
531}
532
533/*
534 * journal_remove_checkpoint: called after a buffer has been committed
535 * to disk (either by being write-back flushed to disk, or being
536 * committed to the log).
537 *
538 * We cannot safely clean a transaction out of the log until all of the
539 * buffer updates committed in that transaction have safely been stored
540 * elsewhere on disk. To achieve this, all of the buffers in a
541 * transaction need to be maintained on the transaction's checkpoint
542 * lists until they have been rewritten, at which point this function is
543 * called to remove the buffer from the existing transaction's
544 * checkpoint lists.
545 *
546 * The function returns 1 if it frees the transaction, 0 otherwise.
547 * The function can free jh and bh.
548 *
549 * This function is called with j_list_lock held.
550 */
551int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
552{
553 struct transaction_chp_stats_s *stats;
554 transaction_t *transaction;
555 journal_t *journal;
556 int ret = 0;
557
558 JBUFFER_TRACE(jh, "entry");
559
560 if ((transaction = jh->b_cp_transaction) == NULL) {
561 JBUFFER_TRACE(jh, "not on transaction");
562 goto out;
563 }
564 journal = transaction->t_journal;
565
566 JBUFFER_TRACE(jh, "removing from transaction");
567 __buffer_unlink(jh);
568 jh->b_cp_transaction = NULL;
569 jbd2_journal_put_journal_head(jh);
570
571 if (transaction->t_checkpoint_list != NULL ||
572 transaction->t_checkpoint_io_list != NULL)
573 goto out;
574
575 /*
576 * There is one special case to worry about: if we have just pulled the
577 * buffer off a running or committing transaction's checkpoing list,
578 * then even if the checkpoint list is empty, the transaction obviously
579 * cannot be dropped!
580 *
581 * The locking here around t_state is a bit sleazy.
582 * See the comment at the end of jbd2_journal_commit_transaction().
583 */
584 if (transaction->t_state != T_FINISHED)
585 goto out;
586
587 /* OK, that was the last buffer for the transaction: we can now
588 safely remove this transaction from the log */
589 stats = &transaction->t_chp_stats;
590 if (stats->cs_chp_time)
591 stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
592 jiffies);
593 trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
594 transaction->t_tid, stats);
595
596 __jbd2_journal_drop_transaction(journal, transaction);
597 jbd2_journal_free_transaction(transaction);
598 ret = 1;
599out:
600 return ret;
601}
602
603/*
604 * journal_insert_checkpoint: put a committed buffer onto a checkpoint
605 * list so that we know when it is safe to clean the transaction out of
606 * the log.
607 *
608 * Called with the journal locked.
609 * Called with j_list_lock held.
610 */
611void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
612 transaction_t *transaction)
613{
614 JBUFFER_TRACE(jh, "entry");
615 J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
616 J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
617
618 /* Get reference for checkpointing transaction */
619 jbd2_journal_grab_journal_head(jh2bh(jh));
620 jh->b_cp_transaction = transaction;
621
622 if (!transaction->t_checkpoint_list) {
623 jh->b_cpnext = jh->b_cpprev = jh;
624 } else {
625 jh->b_cpnext = transaction->t_checkpoint_list;
626 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
627 jh->b_cpprev->b_cpnext = jh;
628 jh->b_cpnext->b_cpprev = jh;
629 }
630 transaction->t_checkpoint_list = jh;
631}
632
633/*
634 * We've finished with this transaction structure: adios...
635 *
636 * The transaction must have no links except for the checkpoint by this
637 * point.
638 *
639 * Called with the journal locked.
640 * Called with j_list_lock held.
641 */
642
643void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
644{
645 assert_spin_locked(&journal->j_list_lock);
646 if (transaction->t_cpnext) {
647 transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
648 transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
649 if (journal->j_checkpoint_transactions == transaction)
650 journal->j_checkpoint_transactions =
651 transaction->t_cpnext;
652 if (journal->j_checkpoint_transactions == transaction)
653 journal->j_checkpoint_transactions = NULL;
654 }
655
656 J_ASSERT(transaction->t_state == T_FINISHED);
657 J_ASSERT(transaction->t_buffers == NULL);
658 J_ASSERT(transaction->t_forget == NULL);
659 J_ASSERT(transaction->t_shadow_list == NULL);
660 J_ASSERT(transaction->t_checkpoint_list == NULL);
661 J_ASSERT(transaction->t_checkpoint_io_list == NULL);
662 J_ASSERT(atomic_read(&transaction->t_updates) == 0);
663 J_ASSERT(journal->j_committing_transaction != transaction);
664 J_ASSERT(journal->j_running_transaction != transaction);
665
666 trace_jbd2_drop_transaction(journal, transaction);
667
668 jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
669}
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 bool has_transaction = false;
83
84 if (journal->j_committing_transaction) {
85 tid = journal->j_committing_transaction->t_tid;
86 has_transaction = true;
87 }
88 spin_unlock(&journal->j_list_lock);
89 write_unlock(&journal->j_state_lock);
90 if (chkpt) {
91 jbd2_log_do_checkpoint(journal);
92 } else if (jbd2_cleanup_journal_tail(journal) <= 0) {
93 /*
94 * We were able to recover space or the
95 * journal was aborted due to an error.
96 */
97 ;
98 } else if (has_transaction) {
99 /*
100 * jbd2_journal_commit_transaction() may want
101 * to take the checkpoint_mutex if JBD2_FLUSHED
102 * is set. So we need to temporarily drop it.
103 */
104 mutex_unlock(&journal->j_checkpoint_mutex);
105 jbd2_log_wait_commit(journal, tid);
106 write_lock(&journal->j_state_lock);
107 continue;
108 } else {
109 printk(KERN_ERR "%s: needed %d blocks and "
110 "only had %d space available\n",
111 __func__, nblocks, space_left);
112 printk(KERN_ERR "%s: no way to get more "
113 "journal space in %s\n", __func__,
114 journal->j_devname);
115 WARN_ON(1);
116 jbd2_journal_abort(journal, -EIO);
117 }
118 write_lock(&journal->j_state_lock);
119 } else {
120 spin_unlock(&journal->j_list_lock);
121 }
122 mutex_unlock(&journal->j_checkpoint_mutex);
123 }
124}
125
126static void
127__flush_batch(journal_t *journal, int *batch_count)
128{
129 int i;
130 struct blk_plug plug;
131
132 blk_start_plug(&plug);
133 for (i = 0; i < *batch_count; i++)
134 write_dirty_buffer(journal->j_chkpt_bhs[i], REQ_SYNC);
135 blk_finish_plug(&plug);
136
137 for (i = 0; i < *batch_count; i++) {
138 struct buffer_head *bh = journal->j_chkpt_bhs[i];
139 BUFFER_TRACE(bh, "brelse");
140 __brelse(bh);
141 journal->j_chkpt_bhs[i] = NULL;
142 }
143 *batch_count = 0;
144}
145
146/*
147 * Perform an actual checkpoint. We take the first transaction on the
148 * list of transactions to be checkpointed and send all its buffers
149 * to disk. We submit larger chunks of data at once.
150 *
151 * The journal should be locked before calling this function.
152 * Called with j_checkpoint_mutex held.
153 */
154int jbd2_log_do_checkpoint(journal_t *journal)
155{
156 struct journal_head *jh;
157 struct buffer_head *bh;
158 transaction_t *transaction;
159 tid_t this_tid;
160 int result, batch_count = 0;
161
162 jbd2_debug(1, "Start checkpoint\n");
163
164 /*
165 * First thing: if there are any transactions in the log which
166 * don't need checkpointing, just eliminate them from the
167 * journal straight away.
168 */
169 result = jbd2_cleanup_journal_tail(journal);
170 trace_jbd2_checkpoint(journal, result);
171 jbd2_debug(1, "cleanup_journal_tail returned %d\n", result);
172 if (result <= 0)
173 return result;
174
175 /*
176 * OK, we need to start writing disk blocks. Take one transaction
177 * and write it.
178 */
179 spin_lock(&journal->j_list_lock);
180 if (!journal->j_checkpoint_transactions)
181 goto out;
182 transaction = journal->j_checkpoint_transactions;
183 if (transaction->t_chp_stats.cs_chp_time == 0)
184 transaction->t_chp_stats.cs_chp_time = jiffies;
185 this_tid = transaction->t_tid;
186restart:
187 /*
188 * If someone cleaned up this transaction while we slept, we're
189 * done (maybe it's a new transaction, but it fell at the same
190 * address).
191 */
192 if (journal->j_checkpoint_transactions != transaction ||
193 transaction->t_tid != this_tid)
194 goto out;
195
196 /* checkpoint all of the transaction's buffers */
197 while (transaction->t_checkpoint_list) {
198 jh = transaction->t_checkpoint_list;
199 bh = jh2bh(jh);
200
201 if (jh->b_transaction != NULL) {
202 transaction_t *t = jh->b_transaction;
203 tid_t tid = t->t_tid;
204
205 transaction->t_chp_stats.cs_forced_to_close++;
206 spin_unlock(&journal->j_list_lock);
207 if (unlikely(journal->j_flags & JBD2_UNMOUNT))
208 /*
209 * The journal thread is dead; so
210 * starting and waiting for a commit
211 * to finish will cause us to wait for
212 * a _very_ long time.
213 */
214 printk(KERN_ERR
215 "JBD2: %s: Waiting for Godot: block %llu\n",
216 journal->j_devname, (unsigned long long) bh->b_blocknr);
217
218 if (batch_count)
219 __flush_batch(journal, &batch_count);
220 jbd2_log_start_commit(journal, tid);
221 /*
222 * jbd2_journal_commit_transaction() may want
223 * to take the checkpoint_mutex if JBD2_FLUSHED
224 * is set, jbd2_update_log_tail() called by
225 * jbd2_journal_commit_transaction() may also take
226 * checkpoint_mutex. So we need to temporarily
227 * drop it.
228 */
229 mutex_unlock(&journal->j_checkpoint_mutex);
230 jbd2_log_wait_commit(journal, tid);
231 mutex_lock_io(&journal->j_checkpoint_mutex);
232 spin_lock(&journal->j_list_lock);
233 goto restart;
234 }
235 if (!trylock_buffer(bh)) {
236 /*
237 * The buffer is locked, it may be writing back, or
238 * flushing out in the last couple of cycles, or
239 * re-adding into a new transaction, need to check
240 * it again until it's unlocked.
241 */
242 get_bh(bh);
243 spin_unlock(&journal->j_list_lock);
244 wait_on_buffer(bh);
245 /* the journal_head may have gone by now */
246 BUFFER_TRACE(bh, "brelse");
247 __brelse(bh);
248 goto retry;
249 } else if (!buffer_dirty(bh)) {
250 unlock_buffer(bh);
251 BUFFER_TRACE(bh, "remove from checkpoint");
252 /*
253 * If the transaction was released or the checkpoint
254 * list was empty, we're done.
255 */
256 if (__jbd2_journal_remove_checkpoint(jh) ||
257 !transaction->t_checkpoint_list)
258 goto out;
259 } else {
260 unlock_buffer(bh);
261 /*
262 * We are about to write the buffer, it could be
263 * raced by some other transaction shrink or buffer
264 * re-log logic once we release the j_list_lock,
265 * leave it on the checkpoint list and check status
266 * again to make sure it's clean.
267 */
268 BUFFER_TRACE(bh, "queue");
269 get_bh(bh);
270 J_ASSERT_BH(bh, !buffer_jwrite(bh));
271 journal->j_chkpt_bhs[batch_count++] = bh;
272 transaction->t_chp_stats.cs_written++;
273 transaction->t_checkpoint_list = jh->b_cpnext;
274 }
275
276 if ((batch_count == JBD2_NR_BATCH) ||
277 need_resched() || spin_needbreak(&journal->j_list_lock) ||
278 jh2bh(transaction->t_checkpoint_list) == journal->j_chkpt_bhs[0])
279 goto unlock_and_flush;
280 }
281
282 if (batch_count) {
283 unlock_and_flush:
284 spin_unlock(&journal->j_list_lock);
285 retry:
286 if (batch_count)
287 __flush_batch(journal, &batch_count);
288 spin_lock(&journal->j_list_lock);
289 goto restart;
290 }
291
292out:
293 spin_unlock(&journal->j_list_lock);
294 result = jbd2_cleanup_journal_tail(journal);
295
296 return (result < 0) ? result : 0;
297}
298
299/*
300 * Check the list of checkpoint transactions for the journal to see if
301 * we have already got rid of any since the last update of the log tail
302 * in the journal superblock. If so, we can instantly roll the
303 * superblock forward to remove those transactions from the log.
304 *
305 * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
306 *
307 * Called with the journal lock held.
308 *
309 * This is the only part of the journaling code which really needs to be
310 * aware of transaction aborts. Checkpointing involves writing to the
311 * main filesystem area rather than to the journal, so it can proceed
312 * even in abort state, but we must not update the super block if
313 * checkpointing may have failed. Otherwise, we would lose some metadata
314 * buffers which should be written-back to the filesystem.
315 */
316
317int jbd2_cleanup_journal_tail(journal_t *journal)
318{
319 tid_t first_tid;
320 unsigned long blocknr;
321
322 if (is_journal_aborted(journal))
323 return -EIO;
324
325 if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
326 return 1;
327 J_ASSERT(blocknr != 0);
328
329 /*
330 * We need to make sure that any blocks that were recently written out
331 * --- perhaps by jbd2_log_do_checkpoint() --- are flushed out before
332 * we drop the transactions from the journal. It's unlikely this will
333 * be necessary, especially with an appropriately sized journal, but we
334 * need this to guarantee correctness. Fortunately
335 * jbd2_cleanup_journal_tail() doesn't get called all that often.
336 */
337 if (journal->j_flags & JBD2_BARRIER)
338 blkdev_issue_flush(journal->j_fs_dev);
339
340 return __jbd2_update_log_tail(journal, first_tid, blocknr);
341}
342
343
344/* Checkpoint list management */
345
346/*
347 * journal_shrink_one_cp_list
348 *
349 * Find all the written-back checkpoint buffers in the given list
350 * and try to release them. If the whole transaction is released, set
351 * the 'released' parameter. Return the number of released checkpointed
352 * buffers.
353 *
354 * Called with j_list_lock held.
355 */
356static unsigned long journal_shrink_one_cp_list(struct journal_head *jh,
357 enum jbd2_shrink_type type,
358 bool *released)
359{
360 struct journal_head *last_jh;
361 struct journal_head *next_jh = jh;
362 unsigned long nr_freed = 0;
363 int ret;
364
365 *released = false;
366 if (!jh)
367 return 0;
368
369 last_jh = jh->b_cpprev;
370 do {
371 jh = next_jh;
372 next_jh = jh->b_cpnext;
373
374 if (type == JBD2_SHRINK_DESTROY) {
375 ret = __jbd2_journal_remove_checkpoint(jh);
376 } else {
377 ret = jbd2_journal_try_remove_checkpoint(jh);
378 if (ret < 0) {
379 if (type == JBD2_SHRINK_BUSY_SKIP)
380 continue;
381 break;
382 }
383 }
384
385 nr_freed++;
386 if (ret) {
387 *released = true;
388 break;
389 }
390
391 if (need_resched())
392 break;
393 } while (jh != last_jh);
394
395 return nr_freed;
396}
397
398/*
399 * jbd2_journal_shrink_checkpoint_list
400 *
401 * Find 'nr_to_scan' written-back checkpoint buffers in the journal
402 * and try to release them. Return the number of released checkpointed
403 * buffers.
404 *
405 * Called with j_list_lock held.
406 */
407unsigned long jbd2_journal_shrink_checkpoint_list(journal_t *journal,
408 unsigned long *nr_to_scan)
409{
410 transaction_t *transaction, *last_transaction, *next_transaction;
411 bool __maybe_unused released;
412 tid_t first_tid = 0, last_tid = 0, next_tid = 0;
413 tid_t tid = 0;
414 unsigned long nr_freed = 0;
415 unsigned long freed;
416 bool first_set = false;
417
418again:
419 spin_lock(&journal->j_list_lock);
420 if (!journal->j_checkpoint_transactions) {
421 spin_unlock(&journal->j_list_lock);
422 goto out;
423 }
424
425 /*
426 * Get next shrink transaction, resume previous scan or start
427 * over again. If some others do checkpoint and drop transaction
428 * from the checkpoint list, we ignore saved j_shrink_transaction
429 * and start over unconditionally.
430 */
431 if (journal->j_shrink_transaction)
432 transaction = journal->j_shrink_transaction;
433 else
434 transaction = journal->j_checkpoint_transactions;
435
436 if (!first_set) {
437 first_tid = transaction->t_tid;
438 first_set = true;
439 }
440 last_transaction = journal->j_checkpoint_transactions->t_cpprev;
441 next_transaction = transaction;
442 last_tid = last_transaction->t_tid;
443 do {
444 transaction = next_transaction;
445 next_transaction = transaction->t_cpnext;
446 tid = transaction->t_tid;
447
448 freed = journal_shrink_one_cp_list(transaction->t_checkpoint_list,
449 JBD2_SHRINK_BUSY_SKIP, &released);
450 nr_freed += freed;
451 (*nr_to_scan) -= min(*nr_to_scan, freed);
452 if (*nr_to_scan == 0)
453 break;
454 if (need_resched() || spin_needbreak(&journal->j_list_lock))
455 break;
456 } while (transaction != last_transaction);
457
458 if (transaction != last_transaction) {
459 journal->j_shrink_transaction = next_transaction;
460 next_tid = next_transaction->t_tid;
461 } else {
462 journal->j_shrink_transaction = NULL;
463 next_tid = 0;
464 }
465
466 spin_unlock(&journal->j_list_lock);
467 cond_resched();
468
469 if (*nr_to_scan && journal->j_shrink_transaction)
470 goto again;
471out:
472 trace_jbd2_shrink_checkpoint_list(journal, first_tid, tid, last_tid,
473 nr_freed, next_tid);
474
475 return nr_freed;
476}
477
478/*
479 * journal_clean_checkpoint_list
480 *
481 * Find all the written-back checkpoint buffers in the journal and release them.
482 * If 'type' is JBD2_SHRINK_DESTROY, release all buffers unconditionally. If
483 * 'type' is JBD2_SHRINK_BUSY_STOP, will stop release buffers if encounters a
484 * busy buffer. To avoid wasting CPU cycles scanning the buffer list in some
485 * cases, don't pass JBD2_SHRINK_BUSY_SKIP 'type' for this function.
486 *
487 * Called with j_list_lock held.
488 */
489void __jbd2_journal_clean_checkpoint_list(journal_t *journal,
490 enum jbd2_shrink_type type)
491{
492 transaction_t *transaction, *last_transaction, *next_transaction;
493 bool released;
494
495 WARN_ON_ONCE(type == JBD2_SHRINK_BUSY_SKIP);
496
497 transaction = journal->j_checkpoint_transactions;
498 if (!transaction)
499 return;
500
501 last_transaction = transaction->t_cpprev;
502 next_transaction = transaction;
503 do {
504 transaction = next_transaction;
505 next_transaction = transaction->t_cpnext;
506 journal_shrink_one_cp_list(transaction->t_checkpoint_list,
507 type, &released);
508 /*
509 * This function only frees up some memory if possible so we
510 * dont have an obligation to finish processing. Bail out if
511 * preemption requested:
512 */
513 if (need_resched())
514 return;
515 /*
516 * Stop scanning if we couldn't free the transaction. This
517 * avoids pointless scanning of transactions which still
518 * weren't checkpointed.
519 */
520 if (!released)
521 return;
522 } while (transaction != last_transaction);
523}
524
525/*
526 * Remove buffers from all checkpoint lists as journal is aborted and we just
527 * need to free memory
528 */
529void jbd2_journal_destroy_checkpoint(journal_t *journal)
530{
531 /*
532 * We loop because __jbd2_journal_clean_checkpoint_list() may abort
533 * early due to a need of rescheduling.
534 */
535 while (1) {
536 spin_lock(&journal->j_list_lock);
537 if (!journal->j_checkpoint_transactions) {
538 spin_unlock(&journal->j_list_lock);
539 break;
540 }
541 __jbd2_journal_clean_checkpoint_list(journal, JBD2_SHRINK_DESTROY);
542 spin_unlock(&journal->j_list_lock);
543 cond_resched();
544 }
545}
546
547/*
548 * journal_remove_checkpoint: called after a buffer has been committed
549 * to disk (either by being write-back flushed to disk, or being
550 * committed to the log).
551 *
552 * We cannot safely clean a transaction out of the log until all of the
553 * buffer updates committed in that transaction have safely been stored
554 * elsewhere on disk. To achieve this, all of the buffers in a
555 * transaction need to be maintained on the transaction's checkpoint
556 * lists until they have been rewritten, at which point this function is
557 * called to remove the buffer from the existing transaction's
558 * checkpoint lists.
559 *
560 * The function returns 1 if it frees the transaction, 0 otherwise.
561 * The function can free jh and bh.
562 *
563 * This function is called with j_list_lock held.
564 */
565int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
566{
567 struct transaction_chp_stats_s *stats;
568 transaction_t *transaction;
569 journal_t *journal;
570
571 JBUFFER_TRACE(jh, "entry");
572
573 transaction = jh->b_cp_transaction;
574 if (!transaction) {
575 JBUFFER_TRACE(jh, "not on transaction");
576 return 0;
577 }
578 journal = transaction->t_journal;
579
580 JBUFFER_TRACE(jh, "removing from transaction");
581
582 __buffer_unlink(jh);
583 jh->b_cp_transaction = NULL;
584 percpu_counter_dec(&journal->j_checkpoint_jh_count);
585 jbd2_journal_put_journal_head(jh);
586
587 /* Is this transaction empty? */
588 if (transaction->t_checkpoint_list)
589 return 0;
590
591 /*
592 * There is one special case to worry about: if we have just pulled the
593 * buffer off a running or committing transaction's checkpoing list,
594 * then even if the checkpoint list is empty, the transaction obviously
595 * cannot be dropped!
596 *
597 * The locking here around t_state is a bit sleazy.
598 * See the comment at the end of jbd2_journal_commit_transaction().
599 */
600 if (transaction->t_state != T_FINISHED)
601 return 0;
602
603 /*
604 * OK, that was the last buffer for the transaction, we can now
605 * safely remove this transaction from the log.
606 */
607 stats = &transaction->t_chp_stats;
608 if (stats->cs_chp_time)
609 stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
610 jiffies);
611 trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
612 transaction->t_tid, stats);
613
614 __jbd2_journal_drop_transaction(journal, transaction);
615 jbd2_journal_free_transaction(transaction);
616 return 1;
617}
618
619/*
620 * Check the checkpoint buffer and try to remove it from the checkpoint
621 * list if it's clean. Returns -EBUSY if it is not clean, returns 1 if
622 * it frees the transaction, 0 otherwise.
623 *
624 * This function is called with j_list_lock held.
625 */
626int jbd2_journal_try_remove_checkpoint(struct journal_head *jh)
627{
628 struct buffer_head *bh = jh2bh(jh);
629
630 if (jh->b_transaction)
631 return -EBUSY;
632 if (!trylock_buffer(bh))
633 return -EBUSY;
634 if (buffer_dirty(bh)) {
635 unlock_buffer(bh);
636 return -EBUSY;
637 }
638 unlock_buffer(bh);
639
640 /*
641 * Buffer is clean and the IO has finished (we held the buffer
642 * lock) so the checkpoint is done. We can safely remove the
643 * buffer from this transaction.
644 */
645 JBUFFER_TRACE(jh, "remove from checkpoint list");
646 return __jbd2_journal_remove_checkpoint(jh);
647}
648
649/*
650 * journal_insert_checkpoint: put a committed buffer onto a checkpoint
651 * list so that we know when it is safe to clean the transaction out of
652 * the log.
653 *
654 * Called with the journal locked.
655 * Called with j_list_lock held.
656 */
657void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
658 transaction_t *transaction)
659{
660 JBUFFER_TRACE(jh, "entry");
661 J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
662 J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
663
664 /* Get reference for checkpointing transaction */
665 jbd2_journal_grab_journal_head(jh2bh(jh));
666 jh->b_cp_transaction = transaction;
667
668 if (!transaction->t_checkpoint_list) {
669 jh->b_cpnext = jh->b_cpprev = jh;
670 } else {
671 jh->b_cpnext = transaction->t_checkpoint_list;
672 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
673 jh->b_cpprev->b_cpnext = jh;
674 jh->b_cpnext->b_cpprev = jh;
675 }
676 transaction->t_checkpoint_list = jh;
677 percpu_counter_inc(&transaction->t_journal->j_checkpoint_jh_count);
678}
679
680/*
681 * We've finished with this transaction structure: adios...
682 *
683 * The transaction must have no links except for the checkpoint by this
684 * point.
685 *
686 * Called with the journal locked.
687 * Called with j_list_lock held.
688 */
689
690void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
691{
692 assert_spin_locked(&journal->j_list_lock);
693
694 journal->j_shrink_transaction = NULL;
695 if (transaction->t_cpnext) {
696 transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
697 transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
698 if (journal->j_checkpoint_transactions == transaction)
699 journal->j_checkpoint_transactions =
700 transaction->t_cpnext;
701 if (journal->j_checkpoint_transactions == transaction)
702 journal->j_checkpoint_transactions = NULL;
703 }
704
705 J_ASSERT(transaction->t_state == T_FINISHED);
706 J_ASSERT(transaction->t_buffers == NULL);
707 J_ASSERT(transaction->t_forget == NULL);
708 J_ASSERT(transaction->t_shadow_list == NULL);
709 J_ASSERT(transaction->t_checkpoint_list == NULL);
710 J_ASSERT(atomic_read(&transaction->t_updates) == 0);
711 J_ASSERT(journal->j_committing_transaction != transaction);
712 J_ASSERT(journal->j_running_transaction != transaction);
713
714 trace_jbd2_drop_transaction(journal, transaction);
715
716 jbd2_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
717}