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1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * linux/fs/jbd2/checkpoint.c
4 *
5 * Written by Stephen C. Tweedie <sct@redhat.com>, 1999
6 *
7 * Copyright 1999 Red Hat Software --- All Rights Reserved
8 *
9 * Checkpoint routines for the generic filesystem journaling code.
10 * Part of the ext2fs journaling system.
11 *
12 * Checkpointing is the process of ensuring that a section of the log is
13 * committed fully to disk, so that that portion of the log can be
14 * reused.
15 */
16
17#include <linux/time.h>
18#include <linux/fs.h>
19#include <linux/jbd2.h>
20#include <linux/errno.h>
21#include <linux/slab.h>
22#include <linux/blkdev.h>
23#include <trace/events/jbd2.h>
24
25/*
26 * Unlink a buffer from a transaction checkpoint list.
27 *
28 * Called with j_list_lock held.
29 */
30static inline void __buffer_unlink_first(struct journal_head *jh)
31{
32 transaction_t *transaction = jh->b_cp_transaction;
33
34 jh->b_cpnext->b_cpprev = jh->b_cpprev;
35 jh->b_cpprev->b_cpnext = jh->b_cpnext;
36 if (transaction->t_checkpoint_list == jh) {
37 transaction->t_checkpoint_list = jh->b_cpnext;
38 if (transaction->t_checkpoint_list == jh)
39 transaction->t_checkpoint_list = NULL;
40 }
41}
42
43/*
44 * Unlink a buffer from a transaction checkpoint(io) list.
45 *
46 * Called with j_list_lock held.
47 */
48static inline void __buffer_unlink(struct journal_head *jh)
49{
50 transaction_t *transaction = jh->b_cp_transaction;
51
52 __buffer_unlink_first(jh);
53 if (transaction->t_checkpoint_io_list == jh) {
54 transaction->t_checkpoint_io_list = jh->b_cpnext;
55 if (transaction->t_checkpoint_io_list == jh)
56 transaction->t_checkpoint_io_list = NULL;
57 }
58}
59
60/*
61 * Move a buffer from the checkpoint list to the checkpoint io list
62 *
63 * Called with j_list_lock held
64 */
65static inline void __buffer_relink_io(struct journal_head *jh)
66{
67 transaction_t *transaction = jh->b_cp_transaction;
68
69 __buffer_unlink_first(jh);
70
71 if (!transaction->t_checkpoint_io_list) {
72 jh->b_cpnext = jh->b_cpprev = jh;
73 } else {
74 jh->b_cpnext = transaction->t_checkpoint_io_list;
75 jh->b_cpprev = transaction->t_checkpoint_io_list->b_cpprev;
76 jh->b_cpprev->b_cpnext = jh;
77 jh->b_cpnext->b_cpprev = jh;
78 }
79 transaction->t_checkpoint_io_list = jh;
80}
81
82/*
83 * Try to release a checkpointed buffer from its transaction.
84 * Returns 1 if we released it and 2 if we also released the
85 * whole transaction.
86 *
87 * Requires j_list_lock
88 */
89static int __try_to_free_cp_buf(struct journal_head *jh)
90{
91 int ret = 0;
92 struct buffer_head *bh = jh2bh(jh);
93
94 if (jh->b_transaction == NULL && !buffer_locked(bh) &&
95 !buffer_dirty(bh) && !buffer_write_io_error(bh)) {
96 JBUFFER_TRACE(jh, "remove from checkpoint list");
97 ret = __jbd2_journal_remove_checkpoint(jh) + 1;
98 }
99 return ret;
100}
101
102/*
103 * __jbd2_log_wait_for_space: wait until there is space in the journal.
104 *
105 * Called under j-state_lock *only*. It will be unlocked if we have to wait
106 * for a checkpoint to free up some space in the log.
107 */
108void __jbd2_log_wait_for_space(journal_t *journal)
109{
110 int nblocks, space_left;
111 /* assert_spin_locked(&journal->j_state_lock); */
112
113 nblocks = jbd2_space_needed(journal);
114 while (jbd2_log_space_left(journal) < nblocks) {
115 write_unlock(&journal->j_state_lock);
116 mutex_lock(&journal->j_checkpoint_mutex);
117
118 /*
119 * Test again, another process may have checkpointed while we
120 * were waiting for the checkpoint lock. If there are no
121 * transactions ready to be checkpointed, try to recover
122 * journal space by calling cleanup_journal_tail(), and if
123 * that doesn't work, by waiting for the currently committing
124 * transaction to complete. If there is absolutely no way
125 * to make progress, this is either a BUG or corrupted
126 * filesystem, so abort the journal and leave a stack
127 * trace for forensic evidence.
128 */
129 write_lock(&journal->j_state_lock);
130 if (journal->j_flags & JBD2_ABORT) {
131 mutex_unlock(&journal->j_checkpoint_mutex);
132 return;
133 }
134 spin_lock(&journal->j_list_lock);
135 nblocks = jbd2_space_needed(journal);
136 space_left = jbd2_log_space_left(journal);
137 if (space_left < nblocks) {
138 int chkpt = journal->j_checkpoint_transactions != NULL;
139 tid_t tid = 0;
140
141 if (journal->j_committing_transaction)
142 tid = journal->j_committing_transaction->t_tid;
143 spin_unlock(&journal->j_list_lock);
144 write_unlock(&journal->j_state_lock);
145 if (chkpt) {
146 jbd2_log_do_checkpoint(journal);
147 } else if (jbd2_cleanup_journal_tail(journal) == 0) {
148 /* We were able to recover space; yay! */
149 ;
150 } else if (tid) {
151 /*
152 * jbd2_journal_commit_transaction() may want
153 * to take the checkpoint_mutex if JBD2_FLUSHED
154 * is set. So we need to temporarily drop it.
155 */
156 mutex_unlock(&journal->j_checkpoint_mutex);
157 jbd2_log_wait_commit(journal, tid);
158 write_lock(&journal->j_state_lock);
159 continue;
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
178static void
179__flush_batch(journal_t *journal, int *batch_count)
180{
181 int i;
182 struct blk_plug plug;
183
184 blk_start_plug(&plug);
185 for (i = 0; i < *batch_count; i++)
186 write_dirty_buffer(journal->j_chkpt_bhs[i], REQ_SYNC);
187 blk_finish_plug(&plug);
188
189 for (i = 0; i < *batch_count; i++) {
190 struct buffer_head *bh = journal->j_chkpt_bhs[i];
191 BUFFER_TRACE(bh, "brelse");
192 __brelse(bh);
193 }
194 *batch_count = 0;
195}
196
197/*
198 * Perform an actual checkpoint. We take the first transaction on the
199 * list of transactions to be checkpointed and send all its buffers
200 * to disk. We submit larger chunks of data at once.
201 *
202 * The journal should be locked before calling this function.
203 * Called with j_checkpoint_mutex held.
204 */
205int jbd2_log_do_checkpoint(journal_t *journal)
206{
207 struct journal_head *jh;
208 struct buffer_head *bh;
209 transaction_t *transaction;
210 tid_t this_tid;
211 int result, batch_count = 0;
212
213 jbd_debug(1, "Start checkpoint\n");
214
215 /*
216 * First thing: if there are any transactions in the log which
217 * don't need checkpointing, just eliminate them from the
218 * journal straight away.
219 */
220 result = jbd2_cleanup_journal_tail(journal);
221 trace_jbd2_checkpoint(journal, result);
222 jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
223 if (result <= 0)
224 return result;
225
226 /*
227 * OK, we need to start writing disk blocks. Take one transaction
228 * and write it.
229 */
230 result = 0;
231 spin_lock(&journal->j_list_lock);
232 if (!journal->j_checkpoint_transactions)
233 goto out;
234 transaction = journal->j_checkpoint_transactions;
235 if (transaction->t_chp_stats.cs_chp_time == 0)
236 transaction->t_chp_stats.cs_chp_time = jiffies;
237 this_tid = transaction->t_tid;
238restart:
239 /*
240 * If someone cleaned up this transaction while we slept, we're
241 * done (maybe it's a new transaction, but it fell at the same
242 * address).
243 */
244 if (journal->j_checkpoint_transactions != transaction ||
245 transaction->t_tid != this_tid)
246 goto out;
247
248 /* checkpoint all of the transaction's buffers */
249 while (transaction->t_checkpoint_list) {
250 jh = transaction->t_checkpoint_list;
251 bh = jh2bh(jh);
252
253 if (buffer_locked(bh)) {
254 spin_unlock(&journal->j_list_lock);
255 get_bh(bh);
256 wait_on_buffer(bh);
257 /* the journal_head may have gone by now */
258 BUFFER_TRACE(bh, "brelse");
259 __brelse(bh);
260 goto retry;
261 }
262 if (jh->b_transaction != NULL) {
263 transaction_t *t = jh->b_transaction;
264 tid_t tid = t->t_tid;
265
266 transaction->t_chp_stats.cs_forced_to_close++;
267 spin_unlock(&journal->j_list_lock);
268 if (unlikely(journal->j_flags & JBD2_UNMOUNT))
269 /*
270 * The journal thread is dead; so
271 * starting and waiting for a commit
272 * to finish will cause us to wait for
273 * a _very_ long time.
274 */
275 printk(KERN_ERR
276 "JBD2: %s: Waiting for Godot: block %llu\n",
277 journal->j_devname, (unsigned long long) bh->b_blocknr);
278
279 jbd2_log_start_commit(journal, tid);
280 jbd2_log_wait_commit(journal, tid);
281 goto retry;
282 }
283 if (!buffer_dirty(bh)) {
284 if (unlikely(buffer_write_io_error(bh)) && !result)
285 result = -EIO;
286 BUFFER_TRACE(bh, "remove from checkpoint");
287 if (__jbd2_journal_remove_checkpoint(jh))
288 /* The transaction was released; we're done */
289 goto out;
290 continue;
291 }
292 /*
293 * Important: we are about to write the buffer, and
294 * possibly block, while still holding the journal
295 * lock. We cannot afford to let the transaction
296 * logic start messing around with this buffer before
297 * we write it to disk, as that would break
298 * recoverability.
299 */
300 BUFFER_TRACE(bh, "queue");
301 get_bh(bh);
302 J_ASSERT_BH(bh, !buffer_jwrite(bh));
303 journal->j_chkpt_bhs[batch_count++] = bh;
304 __buffer_relink_io(jh);
305 transaction->t_chp_stats.cs_written++;
306 if ((batch_count == JBD2_NR_BATCH) ||
307 need_resched() ||
308 spin_needbreak(&journal->j_list_lock))
309 goto unlock_and_flush;
310 }
311
312 if (batch_count) {
313 unlock_and_flush:
314 spin_unlock(&journal->j_list_lock);
315 retry:
316 if (batch_count)
317 __flush_batch(journal, &batch_count);
318 spin_lock(&journal->j_list_lock);
319 goto restart;
320 }
321
322 /*
323 * Now we issued all of the transaction's buffers, let's deal
324 * with the buffers that are out for I/O.
325 */
326restart2:
327 /* Did somebody clean up the transaction in the meanwhile? */
328 if (journal->j_checkpoint_transactions != transaction ||
329 transaction->t_tid != this_tid)
330 goto out;
331
332 while (transaction->t_checkpoint_io_list) {
333 jh = transaction->t_checkpoint_io_list;
334 bh = jh2bh(jh);
335 if (buffer_locked(bh)) {
336 spin_unlock(&journal->j_list_lock);
337 get_bh(bh);
338 wait_on_buffer(bh);
339 /* the journal_head may have gone by now */
340 BUFFER_TRACE(bh, "brelse");
341 __brelse(bh);
342 spin_lock(&journal->j_list_lock);
343 goto restart2;
344 }
345 if (unlikely(buffer_write_io_error(bh)) && !result)
346 result = -EIO;
347
348 /*
349 * Now in whatever state the buffer currently is, we
350 * know that it has been written out and so we can
351 * drop it from the list
352 */
353 if (__jbd2_journal_remove_checkpoint(jh))
354 break;
355 }
356out:
357 spin_unlock(&journal->j_list_lock);
358 if (result < 0)
359 jbd2_journal_abort(journal, result);
360 else
361 result = jbd2_cleanup_journal_tail(journal);
362
363 return (result < 0) ? result : 0;
364}
365
366/*
367 * Check the list of checkpoint transactions for the journal to see if
368 * we have already got rid of any since the last update of the log tail
369 * in the journal superblock. If so, we can instantly roll the
370 * superblock forward to remove those transactions from the log.
371 *
372 * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
373 *
374 * Called with the journal lock held.
375 *
376 * This is the only part of the journaling code which really needs to be
377 * aware of transaction aborts. Checkpointing involves writing to the
378 * main filesystem area rather than to the journal, so it can proceed
379 * even in abort state, but we must not update the super block if
380 * checkpointing may have failed. Otherwise, we would lose some metadata
381 * buffers which should be written-back to the filesystem.
382 */
383
384int jbd2_cleanup_journal_tail(journal_t *journal)
385{
386 tid_t first_tid;
387 unsigned long blocknr;
388
389 if (is_journal_aborted(journal))
390 return -EIO;
391
392 if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
393 return 1;
394 J_ASSERT(blocknr != 0);
395
396 /*
397 * We need to make sure that any blocks that were recently written out
398 * --- perhaps by jbd2_log_do_checkpoint() --- are flushed out before
399 * we drop the transactions from the journal. It's unlikely this will
400 * be necessary, especially with an appropriately sized journal, but we
401 * need this to guarantee correctness. Fortunately
402 * jbd2_cleanup_journal_tail() doesn't get called all that often.
403 */
404 if (journal->j_flags & JBD2_BARRIER)
405 blkdev_issue_flush(journal->j_fs_dev, GFP_NOFS, NULL);
406
407 return __jbd2_update_log_tail(journal, first_tid, blocknr);
408}
409
410
411/* Checkpoint list management */
412
413/*
414 * journal_clean_one_cp_list
415 *
416 * Find all the written-back checkpoint buffers in the given list and
417 * release them. If 'destroy' is set, clean all buffers unconditionally.
418 *
419 * Called with j_list_lock held.
420 * Returns 1 if we freed the transaction, 0 otherwise.
421 */
422static int journal_clean_one_cp_list(struct journal_head *jh, bool destroy)
423{
424 struct journal_head *last_jh;
425 struct journal_head *next_jh = jh;
426 int ret;
427
428 if (!jh)
429 return 0;
430
431 last_jh = jh->b_cpprev;
432 do {
433 jh = next_jh;
434 next_jh = jh->b_cpnext;
435 if (!destroy)
436 ret = __try_to_free_cp_buf(jh);
437 else
438 ret = __jbd2_journal_remove_checkpoint(jh) + 1;
439 if (!ret)
440 return 0;
441 if (ret == 2)
442 return 1;
443 /*
444 * This function only frees up some memory
445 * if possible so we dont have an obligation
446 * to finish processing. Bail out if preemption
447 * requested:
448 */
449 if (need_resched())
450 return 0;
451 } while (jh != last_jh);
452
453 return 0;
454}
455
456/*
457 * journal_clean_checkpoint_list
458 *
459 * Find all the written-back checkpoint buffers in the journal and release them.
460 * If 'destroy' is set, release all buffers unconditionally.
461 *
462 * Called with j_list_lock held.
463 */
464void __jbd2_journal_clean_checkpoint_list(journal_t *journal, bool destroy)
465{
466 transaction_t *transaction, *last_transaction, *next_transaction;
467 int ret;
468
469 transaction = journal->j_checkpoint_transactions;
470 if (!transaction)
471 return;
472
473 last_transaction = transaction->t_cpprev;
474 next_transaction = transaction;
475 do {
476 transaction = next_transaction;
477 next_transaction = transaction->t_cpnext;
478 ret = journal_clean_one_cp_list(transaction->t_checkpoint_list,
479 destroy);
480 /*
481 * This function only frees up some memory if possible so we
482 * dont have an obligation to finish processing. Bail out if
483 * preemption requested:
484 */
485 if (need_resched())
486 return;
487 if (ret)
488 continue;
489 /*
490 * It is essential that we are as careful as in the case of
491 * t_checkpoint_list with removing the buffer from the list as
492 * we can possibly see not yet submitted buffers on io_list
493 */
494 ret = journal_clean_one_cp_list(transaction->
495 t_checkpoint_io_list, destroy);
496 if (need_resched())
497 return;
498 /*
499 * Stop scanning if we couldn't free the transaction. This
500 * avoids pointless scanning of transactions which still
501 * weren't checkpointed.
502 */
503 if (!ret)
504 return;
505 } while (transaction != last_transaction);
506}
507
508/*
509 * Remove buffers from all checkpoint lists as journal is aborted and we just
510 * need to free memory
511 */
512void jbd2_journal_destroy_checkpoint(journal_t *journal)
513{
514 /*
515 * We loop because __jbd2_journal_clean_checkpoint_list() may abort
516 * early due to a need of rescheduling.
517 */
518 while (1) {
519 spin_lock(&journal->j_list_lock);
520 if (!journal->j_checkpoint_transactions) {
521 spin_unlock(&journal->j_list_lock);
522 break;
523 }
524 __jbd2_journal_clean_checkpoint_list(journal, true);
525 spin_unlock(&journal->j_list_lock);
526 cond_resched();
527 }
528}
529
530/*
531 * journal_remove_checkpoint: called after a buffer has been committed
532 * to disk (either by being write-back flushed to disk, or being
533 * committed to the log).
534 *
535 * We cannot safely clean a transaction out of the log until all of the
536 * buffer updates committed in that transaction have safely been stored
537 * elsewhere on disk. To achieve this, all of the buffers in a
538 * transaction need to be maintained on the transaction's checkpoint
539 * lists until they have been rewritten, at which point this function is
540 * called to remove the buffer from the existing transaction's
541 * checkpoint lists.
542 *
543 * The function returns 1 if it frees the transaction, 0 otherwise.
544 * The function can free jh and bh.
545 *
546 * This function is called with j_list_lock held.
547 */
548int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
549{
550 struct transaction_chp_stats_s *stats;
551 transaction_t *transaction;
552 journal_t *journal;
553 int ret = 0;
554
555 JBUFFER_TRACE(jh, "entry");
556
557 if ((transaction = jh->b_cp_transaction) == NULL) {
558 JBUFFER_TRACE(jh, "not on transaction");
559 goto out;
560 }
561 journal = transaction->t_journal;
562
563 JBUFFER_TRACE(jh, "removing from transaction");
564 __buffer_unlink(jh);
565 jh->b_cp_transaction = NULL;
566 jbd2_journal_put_journal_head(jh);
567
568 if (transaction->t_checkpoint_list != NULL ||
569 transaction->t_checkpoint_io_list != NULL)
570 goto out;
571
572 /*
573 * There is one special case to worry about: if we have just pulled the
574 * buffer off a running or committing transaction's checkpoing list,
575 * then even if the checkpoint list is empty, the transaction obviously
576 * cannot be dropped!
577 *
578 * The locking here around t_state is a bit sleazy.
579 * See the comment at the end of jbd2_journal_commit_transaction().
580 */
581 if (transaction->t_state != T_FINISHED)
582 goto out;
583
584 /* OK, that was the last buffer for the transaction: we can now
585 safely remove this transaction from the log */
586 stats = &transaction->t_chp_stats;
587 if (stats->cs_chp_time)
588 stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
589 jiffies);
590 trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
591 transaction->t_tid, stats);
592
593 __jbd2_journal_drop_transaction(journal, transaction);
594 jbd2_journal_free_transaction(transaction);
595 ret = 1;
596out:
597 return ret;
598}
599
600/*
601 * journal_insert_checkpoint: put a committed buffer onto a checkpoint
602 * list so that we know when it is safe to clean the transaction out of
603 * the log.
604 *
605 * Called with the journal locked.
606 * Called with j_list_lock held.
607 */
608void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
609 transaction_t *transaction)
610{
611 JBUFFER_TRACE(jh, "entry");
612 J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
613 J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
614
615 /* Get reference for checkpointing transaction */
616 jbd2_journal_grab_journal_head(jh2bh(jh));
617 jh->b_cp_transaction = transaction;
618
619 if (!transaction->t_checkpoint_list) {
620 jh->b_cpnext = jh->b_cpprev = jh;
621 } else {
622 jh->b_cpnext = transaction->t_checkpoint_list;
623 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
624 jh->b_cpprev->b_cpnext = jh;
625 jh->b_cpnext->b_cpprev = jh;
626 }
627 transaction->t_checkpoint_list = jh;
628}
629
630/*
631 * We've finished with this transaction structure: adios...
632 *
633 * The transaction must have no links except for the checkpoint by this
634 * point.
635 *
636 * Called with the journal locked.
637 * Called with j_list_lock held.
638 */
639
640void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
641{
642 assert_spin_locked(&journal->j_list_lock);
643 if (transaction->t_cpnext) {
644 transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
645 transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
646 if (journal->j_checkpoint_transactions == transaction)
647 journal->j_checkpoint_transactions =
648 transaction->t_cpnext;
649 if (journal->j_checkpoint_transactions == transaction)
650 journal->j_checkpoint_transactions = NULL;
651 }
652
653 J_ASSERT(transaction->t_state == T_FINISHED);
654 J_ASSERT(transaction->t_buffers == NULL);
655 J_ASSERT(transaction->t_forget == NULL);
656 J_ASSERT(transaction->t_shadow_list == NULL);
657 J_ASSERT(transaction->t_checkpoint_list == NULL);
658 J_ASSERT(transaction->t_checkpoint_io_list == NULL);
659 J_ASSERT(atomic_read(&transaction->t_updates) == 0);
660 J_ASSERT(journal->j_committing_transaction != transaction);
661 J_ASSERT(journal->j_running_transaction != transaction);
662
663 trace_jbd2_drop_transaction(journal, transaction);
664
665 jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
666}
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}