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