xref: /openbmc/linux/fs/jbd2/transaction.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
1 /*
2  * linux/fs/jbd2/transaction.c
3  *
4  * Written by Stephen C. Tweedie <sct@redhat.com>, 1998
5  *
6  * Copyright 1998 Red Hat corp --- 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  * Generic filesystem transaction handling code; part of the ext2fs
13  * journaling system.
14  *
15  * This file manages transactions (compound commits managed by the
16  * journaling code) and handles (individual atomic operations by the
17  * filesystem).
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/timer.h>
26 #include <linux/mm.h>
27 #include <linux/highmem.h>
28 
29 static void __jbd2_journal_temp_unlink_buffer(struct journal_head *jh);
30 
31 /*
32  * jbd2_get_transaction: obtain a new transaction_t object.
33  *
34  * Simply allocate and initialise a new transaction.  Create it in
35  * RUNNING state and add it to the current journal (which should not
36  * have an existing running transaction: we only make a new transaction
37  * once we have started to commit the old one).
38  *
39  * Preconditions:
40  *	The journal MUST be locked.  We don't perform atomic mallocs on the
41  *	new transaction	and we can't block without protecting against other
42  *	processes trying to touch the journal while it is in transition.
43  *
44  * Called under j_state_lock
45  */
46 
47 static transaction_t *
48 jbd2_get_transaction(journal_t *journal, transaction_t *transaction)
49 {
50 	transaction->t_journal = journal;
51 	transaction->t_state = T_RUNNING;
52 	transaction->t_tid = journal->j_transaction_sequence++;
53 	transaction->t_expires = jiffies + journal->j_commit_interval;
54 	spin_lock_init(&transaction->t_handle_lock);
55 
56 	/* Set up the commit timer for the new transaction. */
57 	journal->j_commit_timer.expires = transaction->t_expires;
58 	add_timer(&journal->j_commit_timer);
59 
60 	J_ASSERT(journal->j_running_transaction == NULL);
61 	journal->j_running_transaction = transaction;
62 
63 	return transaction;
64 }
65 
66 /*
67  * Handle management.
68  *
69  * A handle_t is an object which represents a single atomic update to a
70  * filesystem, and which tracks all of the modifications which form part
71  * of that one update.
72  */
73 
74 /*
75  * start_this_handle: Given a handle, deal with any locking or stalling
76  * needed to make sure that there is enough journal space for the handle
77  * to begin.  Attach the handle to a transaction and set up the
78  * transaction's buffer credits.
79  */
80 
81 static int start_this_handle(journal_t *journal, handle_t *handle)
82 {
83 	transaction_t *transaction;
84 	int needed;
85 	int nblocks = handle->h_buffer_credits;
86 	transaction_t *new_transaction = NULL;
87 	int ret = 0;
88 
89 	if (nblocks > journal->j_max_transaction_buffers) {
90 		printk(KERN_ERR "JBD: %s wants too many credits (%d > %d)\n",
91 		       current->comm, nblocks,
92 		       journal->j_max_transaction_buffers);
93 		ret = -ENOSPC;
94 		goto out;
95 	}
96 
97 alloc_transaction:
98 	if (!journal->j_running_transaction) {
99 		new_transaction = jbd_kmalloc(sizeof(*new_transaction),
100 						GFP_NOFS);
101 		if (!new_transaction) {
102 			ret = -ENOMEM;
103 			goto out;
104 		}
105 		memset(new_transaction, 0, sizeof(*new_transaction));
106 	}
107 
108 	jbd_debug(3, "New handle %p going live.\n", handle);
109 
110 repeat:
111 
112 	/*
113 	 * We need to hold j_state_lock until t_updates has been incremented,
114 	 * for proper journal barrier handling
115 	 */
116 	spin_lock(&journal->j_state_lock);
117 repeat_locked:
118 	if (is_journal_aborted(journal) ||
119 	    (journal->j_errno != 0 && !(journal->j_flags & JBD2_ACK_ERR))) {
120 		spin_unlock(&journal->j_state_lock);
121 		ret = -EROFS;
122 		goto out;
123 	}
124 
125 	/* Wait on the journal's transaction barrier if necessary */
126 	if (journal->j_barrier_count) {
127 		spin_unlock(&journal->j_state_lock);
128 		wait_event(journal->j_wait_transaction_locked,
129 				journal->j_barrier_count == 0);
130 		goto repeat;
131 	}
132 
133 	if (!journal->j_running_transaction) {
134 		if (!new_transaction) {
135 			spin_unlock(&journal->j_state_lock);
136 			goto alloc_transaction;
137 		}
138 		jbd2_get_transaction(journal, new_transaction);
139 		new_transaction = NULL;
140 	}
141 
142 	transaction = journal->j_running_transaction;
143 
144 	/*
145 	 * If the current transaction is locked down for commit, wait for the
146 	 * lock to be released.
147 	 */
148 	if (transaction->t_state == T_LOCKED) {
149 		DEFINE_WAIT(wait);
150 
151 		prepare_to_wait(&journal->j_wait_transaction_locked,
152 					&wait, TASK_UNINTERRUPTIBLE);
153 		spin_unlock(&journal->j_state_lock);
154 		schedule();
155 		finish_wait(&journal->j_wait_transaction_locked, &wait);
156 		goto repeat;
157 	}
158 
159 	/*
160 	 * If there is not enough space left in the log to write all potential
161 	 * buffers requested by this operation, we need to stall pending a log
162 	 * checkpoint to free some more log space.
163 	 */
164 	spin_lock(&transaction->t_handle_lock);
165 	needed = transaction->t_outstanding_credits + nblocks;
166 
167 	if (needed > journal->j_max_transaction_buffers) {
168 		/*
169 		 * If the current transaction is already too large, then start
170 		 * to commit it: we can then go back and attach this handle to
171 		 * a new transaction.
172 		 */
173 		DEFINE_WAIT(wait);
174 
175 		jbd_debug(2, "Handle %p starting new commit...\n", handle);
176 		spin_unlock(&transaction->t_handle_lock);
177 		prepare_to_wait(&journal->j_wait_transaction_locked, &wait,
178 				TASK_UNINTERRUPTIBLE);
179 		__jbd2_log_start_commit(journal, transaction->t_tid);
180 		spin_unlock(&journal->j_state_lock);
181 		schedule();
182 		finish_wait(&journal->j_wait_transaction_locked, &wait);
183 		goto repeat;
184 	}
185 
186 	/*
187 	 * The commit code assumes that it can get enough log space
188 	 * without forcing a checkpoint.  This is *critical* for
189 	 * correctness: a checkpoint of a buffer which is also
190 	 * associated with a committing transaction creates a deadlock,
191 	 * so commit simply cannot force through checkpoints.
192 	 *
193 	 * We must therefore ensure the necessary space in the journal
194 	 * *before* starting to dirty potentially checkpointed buffers
195 	 * in the new transaction.
196 	 *
197 	 * The worst part is, any transaction currently committing can
198 	 * reduce the free space arbitrarily.  Be careful to account for
199 	 * those buffers when checkpointing.
200 	 */
201 
202 	/*
203 	 * @@@ AKPM: This seems rather over-defensive.  We're giving commit
204 	 * a _lot_ of headroom: 1/4 of the journal plus the size of
205 	 * the committing transaction.  Really, we only need to give it
206 	 * committing_transaction->t_outstanding_credits plus "enough" for
207 	 * the log control blocks.
208 	 * Also, this test is inconsitent with the matching one in
209 	 * jbd2_journal_extend().
210 	 */
211 	if (__jbd2_log_space_left(journal) < jbd_space_needed(journal)) {
212 		jbd_debug(2, "Handle %p waiting for checkpoint...\n", handle);
213 		spin_unlock(&transaction->t_handle_lock);
214 		__jbd2_log_wait_for_space(journal);
215 		goto repeat_locked;
216 	}
217 
218 	/* OK, account for the buffers that this operation expects to
219 	 * use and add the handle to the running transaction. */
220 
221 	handle->h_transaction = transaction;
222 	transaction->t_outstanding_credits += nblocks;
223 	transaction->t_updates++;
224 	transaction->t_handle_count++;
225 	jbd_debug(4, "Handle %p given %d credits (total %d, free %d)\n",
226 		  handle, nblocks, transaction->t_outstanding_credits,
227 		  __jbd2_log_space_left(journal));
228 	spin_unlock(&transaction->t_handle_lock);
229 	spin_unlock(&journal->j_state_lock);
230 out:
231 	if (unlikely(new_transaction))		/* It's usually NULL */
232 		kfree(new_transaction);
233 	return ret;
234 }
235 
236 /* Allocate a new handle.  This should probably be in a slab... */
237 static handle_t *new_handle(int nblocks)
238 {
239 	handle_t *handle = jbd_alloc_handle(GFP_NOFS);
240 	if (!handle)
241 		return NULL;
242 	memset(handle, 0, sizeof(*handle));
243 	handle->h_buffer_credits = nblocks;
244 	handle->h_ref = 1;
245 
246 	return handle;
247 }
248 
249 /**
250  * handle_t *jbd2_journal_start() - Obtain a new handle.
251  * @journal: Journal to start transaction on.
252  * @nblocks: number of block buffer we might modify
253  *
254  * We make sure that the transaction can guarantee at least nblocks of
255  * modified buffers in the log.  We block until the log can guarantee
256  * that much space.
257  *
258  * This function is visible to journal users (like ext3fs), so is not
259  * called with the journal already locked.
260  *
261  * Return a pointer to a newly allocated handle, or NULL on failure
262  */
263 handle_t *jbd2_journal_start(journal_t *journal, int nblocks)
264 {
265 	handle_t *handle = journal_current_handle();
266 	int err;
267 
268 	if (!journal)
269 		return ERR_PTR(-EROFS);
270 
271 	if (handle) {
272 		J_ASSERT(handle->h_transaction->t_journal == journal);
273 		handle->h_ref++;
274 		return handle;
275 	}
276 
277 	handle = new_handle(nblocks);
278 	if (!handle)
279 		return ERR_PTR(-ENOMEM);
280 
281 	current->journal_info = handle;
282 
283 	err = start_this_handle(journal, handle);
284 	if (err < 0) {
285 		jbd_free_handle(handle);
286 		current->journal_info = NULL;
287 		handle = ERR_PTR(err);
288 	}
289 	return handle;
290 }
291 
292 /**
293  * int jbd2_journal_extend() - extend buffer credits.
294  * @handle:  handle to 'extend'
295  * @nblocks: nr blocks to try to extend by.
296  *
297  * Some transactions, such as large extends and truncates, can be done
298  * atomically all at once or in several stages.  The operation requests
299  * a credit for a number of buffer modications in advance, but can
300  * extend its credit if it needs more.
301  *
302  * jbd2_journal_extend tries to give the running handle more buffer credits.
303  * It does not guarantee that allocation - this is a best-effort only.
304  * The calling process MUST be able to deal cleanly with a failure to
305  * extend here.
306  *
307  * Return 0 on success, non-zero on failure.
308  *
309  * return code < 0 implies an error
310  * return code > 0 implies normal transaction-full status.
311  */
312 int jbd2_journal_extend(handle_t *handle, int nblocks)
313 {
314 	transaction_t *transaction = handle->h_transaction;
315 	journal_t *journal = transaction->t_journal;
316 	int result;
317 	int wanted;
318 
319 	result = -EIO;
320 	if (is_handle_aborted(handle))
321 		goto out;
322 
323 	result = 1;
324 
325 	spin_lock(&journal->j_state_lock);
326 
327 	/* Don't extend a locked-down transaction! */
328 	if (handle->h_transaction->t_state != T_RUNNING) {
329 		jbd_debug(3, "denied handle %p %d blocks: "
330 			  "transaction not running\n", handle, nblocks);
331 		goto error_out;
332 	}
333 
334 	spin_lock(&transaction->t_handle_lock);
335 	wanted = transaction->t_outstanding_credits + nblocks;
336 
337 	if (wanted > journal->j_max_transaction_buffers) {
338 		jbd_debug(3, "denied handle %p %d blocks: "
339 			  "transaction too large\n", handle, nblocks);
340 		goto unlock;
341 	}
342 
343 	if (wanted > __jbd2_log_space_left(journal)) {
344 		jbd_debug(3, "denied handle %p %d blocks: "
345 			  "insufficient log space\n", handle, nblocks);
346 		goto unlock;
347 	}
348 
349 	handle->h_buffer_credits += nblocks;
350 	transaction->t_outstanding_credits += nblocks;
351 	result = 0;
352 
353 	jbd_debug(3, "extended handle %p by %d\n", handle, nblocks);
354 unlock:
355 	spin_unlock(&transaction->t_handle_lock);
356 error_out:
357 	spin_unlock(&journal->j_state_lock);
358 out:
359 	return result;
360 }
361 
362 
363 /**
364  * int jbd2_journal_restart() - restart a handle .
365  * @handle:  handle to restart
366  * @nblocks: nr credits requested
367  *
368  * Restart a handle for a multi-transaction filesystem
369  * operation.
370  *
371  * If the jbd2_journal_extend() call above fails to grant new buffer credits
372  * to a running handle, a call to jbd2_journal_restart will commit the
373  * handle's transaction so far and reattach the handle to a new
374  * transaction capabable of guaranteeing the requested number of
375  * credits.
376  */
377 
378 int jbd2_journal_restart(handle_t *handle, int nblocks)
379 {
380 	transaction_t *transaction = handle->h_transaction;
381 	journal_t *journal = transaction->t_journal;
382 	int ret;
383 
384 	/* If we've had an abort of any type, don't even think about
385 	 * actually doing the restart! */
386 	if (is_handle_aborted(handle))
387 		return 0;
388 
389 	/*
390 	 * First unlink the handle from its current transaction, and start the
391 	 * commit on that.
392 	 */
393 	J_ASSERT(transaction->t_updates > 0);
394 	J_ASSERT(journal_current_handle() == handle);
395 
396 	spin_lock(&journal->j_state_lock);
397 	spin_lock(&transaction->t_handle_lock);
398 	transaction->t_outstanding_credits -= handle->h_buffer_credits;
399 	transaction->t_updates--;
400 
401 	if (!transaction->t_updates)
402 		wake_up(&journal->j_wait_updates);
403 	spin_unlock(&transaction->t_handle_lock);
404 
405 	jbd_debug(2, "restarting handle %p\n", handle);
406 	__jbd2_log_start_commit(journal, transaction->t_tid);
407 	spin_unlock(&journal->j_state_lock);
408 
409 	handle->h_buffer_credits = nblocks;
410 	ret = start_this_handle(journal, handle);
411 	return ret;
412 }
413 
414 
415 /**
416  * void jbd2_journal_lock_updates () - establish a transaction barrier.
417  * @journal:  Journal to establish a barrier on.
418  *
419  * This locks out any further updates from being started, and blocks
420  * until all existing updates have completed, returning only once the
421  * journal is in a quiescent state with no updates running.
422  *
423  * The journal lock should not be held on entry.
424  */
425 void jbd2_journal_lock_updates(journal_t *journal)
426 {
427 	DEFINE_WAIT(wait);
428 
429 	spin_lock(&journal->j_state_lock);
430 	++journal->j_barrier_count;
431 
432 	/* Wait until there are no running updates */
433 	while (1) {
434 		transaction_t *transaction = journal->j_running_transaction;
435 
436 		if (!transaction)
437 			break;
438 
439 		spin_lock(&transaction->t_handle_lock);
440 		if (!transaction->t_updates) {
441 			spin_unlock(&transaction->t_handle_lock);
442 			break;
443 		}
444 		prepare_to_wait(&journal->j_wait_updates, &wait,
445 				TASK_UNINTERRUPTIBLE);
446 		spin_unlock(&transaction->t_handle_lock);
447 		spin_unlock(&journal->j_state_lock);
448 		schedule();
449 		finish_wait(&journal->j_wait_updates, &wait);
450 		spin_lock(&journal->j_state_lock);
451 	}
452 	spin_unlock(&journal->j_state_lock);
453 
454 	/*
455 	 * We have now established a barrier against other normal updates, but
456 	 * we also need to barrier against other jbd2_journal_lock_updates() calls
457 	 * to make sure that we serialise special journal-locked operations
458 	 * too.
459 	 */
460 	mutex_lock(&journal->j_barrier);
461 }
462 
463 /**
464  * void jbd2_journal_unlock_updates (journal_t* journal) - release barrier
465  * @journal:  Journal to release the barrier on.
466  *
467  * Release a transaction barrier obtained with jbd2_journal_lock_updates().
468  *
469  * Should be called without the journal lock held.
470  */
471 void jbd2_journal_unlock_updates (journal_t *journal)
472 {
473 	J_ASSERT(journal->j_barrier_count != 0);
474 
475 	mutex_unlock(&journal->j_barrier);
476 	spin_lock(&journal->j_state_lock);
477 	--journal->j_barrier_count;
478 	spin_unlock(&journal->j_state_lock);
479 	wake_up(&journal->j_wait_transaction_locked);
480 }
481 
482 /*
483  * Report any unexpected dirty buffers which turn up.  Normally those
484  * indicate an error, but they can occur if the user is running (say)
485  * tune2fs to modify the live filesystem, so we need the option of
486  * continuing as gracefully as possible.  #
487  *
488  * The caller should already hold the journal lock and
489  * j_list_lock spinlock: most callers will need those anyway
490  * in order to probe the buffer's journaling state safely.
491  */
492 static void jbd_unexpected_dirty_buffer(struct journal_head *jh)
493 {
494 	int jlist;
495 
496 	/* If this buffer is one which might reasonably be dirty
497 	 * --- ie. data, or not part of this journal --- then
498 	 * we're OK to leave it alone, but otherwise we need to
499 	 * move the dirty bit to the journal's own internal
500 	 * JBDDirty bit. */
501 	jlist = jh->b_jlist;
502 
503 	if (jlist == BJ_Metadata || jlist == BJ_Reserved ||
504 	    jlist == BJ_Shadow || jlist == BJ_Forget) {
505 		struct buffer_head *bh = jh2bh(jh);
506 
507 		if (test_clear_buffer_dirty(bh))
508 			set_buffer_jbddirty(bh);
509 	}
510 }
511 
512 /*
513  * If the buffer is already part of the current transaction, then there
514  * is nothing we need to do.  If it is already part of a prior
515  * transaction which we are still committing to disk, then we need to
516  * make sure that we do not overwrite the old copy: we do copy-out to
517  * preserve the copy going to disk.  We also account the buffer against
518  * the handle's metadata buffer credits (unless the buffer is already
519  * part of the transaction, that is).
520  *
521  */
522 static int
523 do_get_write_access(handle_t *handle, struct journal_head *jh,
524 			int force_copy)
525 {
526 	struct buffer_head *bh;
527 	transaction_t *transaction;
528 	journal_t *journal;
529 	int error;
530 	char *frozen_buffer = NULL;
531 	int need_copy = 0;
532 
533 	if (is_handle_aborted(handle))
534 		return -EROFS;
535 
536 	transaction = handle->h_transaction;
537 	journal = transaction->t_journal;
538 
539 	jbd_debug(5, "buffer_head %p, force_copy %d\n", jh, force_copy);
540 
541 	JBUFFER_TRACE(jh, "entry");
542 repeat:
543 	bh = jh2bh(jh);
544 
545 	/* @@@ Need to check for errors here at some point. */
546 
547 	lock_buffer(bh);
548 	jbd_lock_bh_state(bh);
549 
550 	/* We now hold the buffer lock so it is safe to query the buffer
551 	 * state.  Is the buffer dirty?
552 	 *
553 	 * If so, there are two possibilities.  The buffer may be
554 	 * non-journaled, and undergoing a quite legitimate writeback.
555 	 * Otherwise, it is journaled, and we don't expect dirty buffers
556 	 * in that state (the buffers should be marked JBD_Dirty
557 	 * instead.)  So either the IO is being done under our own
558 	 * control and this is a bug, or it's a third party IO such as
559 	 * dump(8) (which may leave the buffer scheduled for read ---
560 	 * ie. locked but not dirty) or tune2fs (which may actually have
561 	 * the buffer dirtied, ugh.)  */
562 
563 	if (buffer_dirty(bh)) {
564 		/*
565 		 * First question: is this buffer already part of the current
566 		 * transaction or the existing committing transaction?
567 		 */
568 		if (jh->b_transaction) {
569 			J_ASSERT_JH(jh,
570 				jh->b_transaction == transaction ||
571 				jh->b_transaction ==
572 					journal->j_committing_transaction);
573 			if (jh->b_next_transaction)
574 				J_ASSERT_JH(jh, jh->b_next_transaction ==
575 							transaction);
576 		}
577 		/*
578 		 * In any case we need to clean the dirty flag and we must
579 		 * do it under the buffer lock to be sure we don't race
580 		 * with running write-out.
581 		 */
582 		JBUFFER_TRACE(jh, "Unexpected dirty buffer");
583 		jbd_unexpected_dirty_buffer(jh);
584 	}
585 
586 	unlock_buffer(bh);
587 
588 	error = -EROFS;
589 	if (is_handle_aborted(handle)) {
590 		jbd_unlock_bh_state(bh);
591 		goto out;
592 	}
593 	error = 0;
594 
595 	/*
596 	 * The buffer is already part of this transaction if b_transaction or
597 	 * b_next_transaction points to it
598 	 */
599 	if (jh->b_transaction == transaction ||
600 	    jh->b_next_transaction == transaction)
601 		goto done;
602 
603 	/*
604 	 * If there is already a copy-out version of this buffer, then we don't
605 	 * need to make another one
606 	 */
607 	if (jh->b_frozen_data) {
608 		JBUFFER_TRACE(jh, "has frozen data");
609 		J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
610 		jh->b_next_transaction = transaction;
611 		goto done;
612 	}
613 
614 	/* Is there data here we need to preserve? */
615 
616 	if (jh->b_transaction && jh->b_transaction != transaction) {
617 		JBUFFER_TRACE(jh, "owned by older transaction");
618 		J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
619 		J_ASSERT_JH(jh, jh->b_transaction ==
620 					journal->j_committing_transaction);
621 
622 		/* There is one case we have to be very careful about.
623 		 * If the committing transaction is currently writing
624 		 * this buffer out to disk and has NOT made a copy-out,
625 		 * then we cannot modify the buffer contents at all
626 		 * right now.  The essence of copy-out is that it is the
627 		 * extra copy, not the primary copy, which gets
628 		 * journaled.  If the primary copy is already going to
629 		 * disk then we cannot do copy-out here. */
630 
631 		if (jh->b_jlist == BJ_Shadow) {
632 			DEFINE_WAIT_BIT(wait, &bh->b_state, BH_Unshadow);
633 			wait_queue_head_t *wqh;
634 
635 			wqh = bit_waitqueue(&bh->b_state, BH_Unshadow);
636 
637 			JBUFFER_TRACE(jh, "on shadow: sleep");
638 			jbd_unlock_bh_state(bh);
639 			/* commit wakes up all shadow buffers after IO */
640 			for ( ; ; ) {
641 				prepare_to_wait(wqh, &wait.wait,
642 						TASK_UNINTERRUPTIBLE);
643 				if (jh->b_jlist != BJ_Shadow)
644 					break;
645 				schedule();
646 			}
647 			finish_wait(wqh, &wait.wait);
648 			goto repeat;
649 		}
650 
651 		/* Only do the copy if the currently-owning transaction
652 		 * still needs it.  If it is on the Forget list, the
653 		 * committing transaction is past that stage.  The
654 		 * buffer had better remain locked during the kmalloc,
655 		 * but that should be true --- we hold the journal lock
656 		 * still and the buffer is already on the BUF_JOURNAL
657 		 * list so won't be flushed.
658 		 *
659 		 * Subtle point, though: if this is a get_undo_access,
660 		 * then we will be relying on the frozen_data to contain
661 		 * the new value of the committed_data record after the
662 		 * transaction, so we HAVE to force the frozen_data copy
663 		 * in that case. */
664 
665 		if (jh->b_jlist != BJ_Forget || force_copy) {
666 			JBUFFER_TRACE(jh, "generate frozen data");
667 			if (!frozen_buffer) {
668 				JBUFFER_TRACE(jh, "allocate memory for buffer");
669 				jbd_unlock_bh_state(bh);
670 				frozen_buffer =
671 					jbd2_slab_alloc(jh2bh(jh)->b_size,
672 							 GFP_NOFS);
673 				if (!frozen_buffer) {
674 					printk(KERN_EMERG
675 					       "%s: OOM for frozen_buffer\n",
676 					       __FUNCTION__);
677 					JBUFFER_TRACE(jh, "oom!");
678 					error = -ENOMEM;
679 					jbd_lock_bh_state(bh);
680 					goto done;
681 				}
682 				goto repeat;
683 			}
684 			jh->b_frozen_data = frozen_buffer;
685 			frozen_buffer = NULL;
686 			need_copy = 1;
687 		}
688 		jh->b_next_transaction = transaction;
689 	}
690 
691 
692 	/*
693 	 * Finally, if the buffer is not journaled right now, we need to make
694 	 * sure it doesn't get written to disk before the caller actually
695 	 * commits the new data
696 	 */
697 	if (!jh->b_transaction) {
698 		JBUFFER_TRACE(jh, "no transaction");
699 		J_ASSERT_JH(jh, !jh->b_next_transaction);
700 		jh->b_transaction = transaction;
701 		JBUFFER_TRACE(jh, "file as BJ_Reserved");
702 		spin_lock(&journal->j_list_lock);
703 		__jbd2_journal_file_buffer(jh, transaction, BJ_Reserved);
704 		spin_unlock(&journal->j_list_lock);
705 	}
706 
707 done:
708 	if (need_copy) {
709 		struct page *page;
710 		int offset;
711 		char *source;
712 
713 		J_EXPECT_JH(jh, buffer_uptodate(jh2bh(jh)),
714 			    "Possible IO failure.\n");
715 		page = jh2bh(jh)->b_page;
716 		offset = ((unsigned long) jh2bh(jh)->b_data) & ~PAGE_MASK;
717 		source = kmap_atomic(page, KM_USER0);
718 		memcpy(jh->b_frozen_data, source+offset, jh2bh(jh)->b_size);
719 		kunmap_atomic(source, KM_USER0);
720 	}
721 	jbd_unlock_bh_state(bh);
722 
723 	/*
724 	 * If we are about to journal a buffer, then any revoke pending on it is
725 	 * no longer valid
726 	 */
727 	jbd2_journal_cancel_revoke(handle, jh);
728 
729 out:
730 	if (unlikely(frozen_buffer))	/* It's usually NULL */
731 		jbd2_slab_free(frozen_buffer, bh->b_size);
732 
733 	JBUFFER_TRACE(jh, "exit");
734 	return error;
735 }
736 
737 /**
738  * int jbd2_journal_get_write_access() - notify intent to modify a buffer for metadata (not data) update.
739  * @handle: transaction to add buffer modifications to
740  * @bh:     bh to be used for metadata writes
741  * @credits: variable that will receive credits for the buffer
742  *
743  * Returns an error code or 0 on success.
744  *
745  * In full data journalling mode the buffer may be of type BJ_AsyncData,
746  * because we're write()ing a buffer which is also part of a shared mapping.
747  */
748 
749 int jbd2_journal_get_write_access(handle_t *handle, struct buffer_head *bh)
750 {
751 	struct journal_head *jh = jbd2_journal_add_journal_head(bh);
752 	int rc;
753 
754 	/* We do not want to get caught playing with fields which the
755 	 * log thread also manipulates.  Make sure that the buffer
756 	 * completes any outstanding IO before proceeding. */
757 	rc = do_get_write_access(handle, jh, 0);
758 	jbd2_journal_put_journal_head(jh);
759 	return rc;
760 }
761 
762 
763 /*
764  * When the user wants to journal a newly created buffer_head
765  * (ie. getblk() returned a new buffer and we are going to populate it
766  * manually rather than reading off disk), then we need to keep the
767  * buffer_head locked until it has been completely filled with new
768  * data.  In this case, we should be able to make the assertion that
769  * the bh is not already part of an existing transaction.
770  *
771  * The buffer should already be locked by the caller by this point.
772  * There is no lock ranking violation: it was a newly created,
773  * unlocked buffer beforehand. */
774 
775 /**
776  * int jbd2_journal_get_create_access () - notify intent to use newly created bh
777  * @handle: transaction to new buffer to
778  * @bh: new buffer.
779  *
780  * Call this if you create a new bh.
781  */
782 int jbd2_journal_get_create_access(handle_t *handle, struct buffer_head *bh)
783 {
784 	transaction_t *transaction = handle->h_transaction;
785 	journal_t *journal = transaction->t_journal;
786 	struct journal_head *jh = jbd2_journal_add_journal_head(bh);
787 	int err;
788 
789 	jbd_debug(5, "journal_head %p\n", jh);
790 	err = -EROFS;
791 	if (is_handle_aborted(handle))
792 		goto out;
793 	err = 0;
794 
795 	JBUFFER_TRACE(jh, "entry");
796 	/*
797 	 * The buffer may already belong to this transaction due to pre-zeroing
798 	 * in the filesystem's new_block code.  It may also be on the previous,
799 	 * committing transaction's lists, but it HAS to be in Forget state in
800 	 * that case: the transaction must have deleted the buffer for it to be
801 	 * reused here.
802 	 */
803 	jbd_lock_bh_state(bh);
804 	spin_lock(&journal->j_list_lock);
805 	J_ASSERT_JH(jh, (jh->b_transaction == transaction ||
806 		jh->b_transaction == NULL ||
807 		(jh->b_transaction == journal->j_committing_transaction &&
808 			  jh->b_jlist == BJ_Forget)));
809 
810 	J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
811 	J_ASSERT_JH(jh, buffer_locked(jh2bh(jh)));
812 
813 	if (jh->b_transaction == NULL) {
814 		jh->b_transaction = transaction;
815 		JBUFFER_TRACE(jh, "file as BJ_Reserved");
816 		__jbd2_journal_file_buffer(jh, transaction, BJ_Reserved);
817 	} else if (jh->b_transaction == journal->j_committing_transaction) {
818 		JBUFFER_TRACE(jh, "set next transaction");
819 		jh->b_next_transaction = transaction;
820 	}
821 	spin_unlock(&journal->j_list_lock);
822 	jbd_unlock_bh_state(bh);
823 
824 	/*
825 	 * akpm: I added this.  ext3_alloc_branch can pick up new indirect
826 	 * blocks which contain freed but then revoked metadata.  We need
827 	 * to cancel the revoke in case we end up freeing it yet again
828 	 * and the reallocating as data - this would cause a second revoke,
829 	 * which hits an assertion error.
830 	 */
831 	JBUFFER_TRACE(jh, "cancelling revoke");
832 	jbd2_journal_cancel_revoke(handle, jh);
833 	jbd2_journal_put_journal_head(jh);
834 out:
835 	return err;
836 }
837 
838 /**
839  * int jbd2_journal_get_undo_access() -  Notify intent to modify metadata with
840  *     non-rewindable consequences
841  * @handle: transaction
842  * @bh: buffer to undo
843  * @credits: store the number of taken credits here (if not NULL)
844  *
845  * Sometimes there is a need to distinguish between metadata which has
846  * been committed to disk and that which has not.  The ext3fs code uses
847  * this for freeing and allocating space, we have to make sure that we
848  * do not reuse freed space until the deallocation has been committed,
849  * since if we overwrote that space we would make the delete
850  * un-rewindable in case of a crash.
851  *
852  * To deal with that, jbd2_journal_get_undo_access requests write access to a
853  * buffer for parts of non-rewindable operations such as delete
854  * operations on the bitmaps.  The journaling code must keep a copy of
855  * the buffer's contents prior to the undo_access call until such time
856  * as we know that the buffer has definitely been committed to disk.
857  *
858  * We never need to know which transaction the committed data is part
859  * of, buffers touched here are guaranteed to be dirtied later and so
860  * will be committed to a new transaction in due course, at which point
861  * we can discard the old committed data pointer.
862  *
863  * Returns error number or 0 on success.
864  */
865 int jbd2_journal_get_undo_access(handle_t *handle, struct buffer_head *bh)
866 {
867 	int err;
868 	struct journal_head *jh = jbd2_journal_add_journal_head(bh);
869 	char *committed_data = NULL;
870 
871 	JBUFFER_TRACE(jh, "entry");
872 
873 	/*
874 	 * Do this first --- it can drop the journal lock, so we want to
875 	 * make sure that obtaining the committed_data is done
876 	 * atomically wrt. completion of any outstanding commits.
877 	 */
878 	err = do_get_write_access(handle, jh, 1);
879 	if (err)
880 		goto out;
881 
882 repeat:
883 	if (!jh->b_committed_data) {
884 		committed_data = jbd2_slab_alloc(jh2bh(jh)->b_size, GFP_NOFS);
885 		if (!committed_data) {
886 			printk(KERN_EMERG "%s: No memory for committed data\n",
887 				__FUNCTION__);
888 			err = -ENOMEM;
889 			goto out;
890 		}
891 	}
892 
893 	jbd_lock_bh_state(bh);
894 	if (!jh->b_committed_data) {
895 		/* Copy out the current buffer contents into the
896 		 * preserved, committed copy. */
897 		JBUFFER_TRACE(jh, "generate b_committed data");
898 		if (!committed_data) {
899 			jbd_unlock_bh_state(bh);
900 			goto repeat;
901 		}
902 
903 		jh->b_committed_data = committed_data;
904 		committed_data = NULL;
905 		memcpy(jh->b_committed_data, bh->b_data, bh->b_size);
906 	}
907 	jbd_unlock_bh_state(bh);
908 out:
909 	jbd2_journal_put_journal_head(jh);
910 	if (unlikely(committed_data))
911 		jbd2_slab_free(committed_data, bh->b_size);
912 	return err;
913 }
914 
915 /**
916  * int jbd2_journal_dirty_data() -  mark a buffer as containing dirty data which
917  *                             needs to be flushed before we can commit the
918  *                             current transaction.
919  * @handle: transaction
920  * @bh: bufferhead to mark
921  *
922  * The buffer is placed on the transaction's data list and is marked as
923  * belonging to the transaction.
924  *
925  * Returns error number or 0 on success.
926  *
927  * jbd2_journal_dirty_data() can be called via page_launder->ext3_writepage
928  * by kswapd.
929  */
930 int jbd2_journal_dirty_data(handle_t *handle, struct buffer_head *bh)
931 {
932 	journal_t *journal = handle->h_transaction->t_journal;
933 	int need_brelse = 0;
934 	struct journal_head *jh;
935 
936 	if (is_handle_aborted(handle))
937 		return 0;
938 
939 	jh = jbd2_journal_add_journal_head(bh);
940 	JBUFFER_TRACE(jh, "entry");
941 
942 	/*
943 	 * The buffer could *already* be dirty.  Writeout can start
944 	 * at any time.
945 	 */
946 	jbd_debug(4, "jh: %p, tid:%d\n", jh, handle->h_transaction->t_tid);
947 
948 	/*
949 	 * What if the buffer is already part of a running transaction?
950 	 *
951 	 * There are two cases:
952 	 * 1) It is part of the current running transaction.  Refile it,
953 	 *    just in case we have allocated it as metadata, deallocated
954 	 *    it, then reallocated it as data.
955 	 * 2) It is part of the previous, still-committing transaction.
956 	 *    If all we want to do is to guarantee that the buffer will be
957 	 *    written to disk before this new transaction commits, then
958 	 *    being sure that the *previous* transaction has this same
959 	 *    property is sufficient for us!  Just leave it on its old
960 	 *    transaction.
961 	 *
962 	 * In case (2), the buffer must not already exist as metadata
963 	 * --- that would violate write ordering (a transaction is free
964 	 * to write its data at any point, even before the previous
965 	 * committing transaction has committed).  The caller must
966 	 * never, ever allow this to happen: there's nothing we can do
967 	 * about it in this layer.
968 	 */
969 	jbd_lock_bh_state(bh);
970 	spin_lock(&journal->j_list_lock);
971 
972 	/* Now that we have bh_state locked, are we really still mapped? */
973 	if (!buffer_mapped(bh)) {
974 		JBUFFER_TRACE(jh, "unmapped buffer, bailing out");
975 		goto no_journal;
976 	}
977 
978 	if (jh->b_transaction) {
979 		JBUFFER_TRACE(jh, "has transaction");
980 		if (jh->b_transaction != handle->h_transaction) {
981 			JBUFFER_TRACE(jh, "belongs to older transaction");
982 			J_ASSERT_JH(jh, jh->b_transaction ==
983 					journal->j_committing_transaction);
984 
985 			/* @@@ IS THIS TRUE  ? */
986 			/*
987 			 * Not any more.  Scenario: someone does a write()
988 			 * in data=journal mode.  The buffer's transaction has
989 			 * moved into commit.  Then someone does another
990 			 * write() to the file.  We do the frozen data copyout
991 			 * and set b_next_transaction to point to j_running_t.
992 			 * And while we're in that state, someone does a
993 			 * writepage() in an attempt to pageout the same area
994 			 * of the file via a shared mapping.  At present that
995 			 * calls jbd2_journal_dirty_data(), and we get right here.
996 			 * It may be too late to journal the data.  Simply
997 			 * falling through to the next test will suffice: the
998 			 * data will be dirty and wil be checkpointed.  The
999 			 * ordering comments in the next comment block still
1000 			 * apply.
1001 			 */
1002 			//J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
1003 
1004 			/*
1005 			 * If we're journalling data, and this buffer was
1006 			 * subject to a write(), it could be metadata, forget
1007 			 * or shadow against the committing transaction.  Now,
1008 			 * someone has dirtied the same darn page via a mapping
1009 			 * and it is being writepage()'d.
1010 			 * We *could* just steal the page from commit, with some
1011 			 * fancy locking there.  Instead, we just skip it -
1012 			 * don't tie the page's buffers to the new transaction
1013 			 * at all.
1014 			 * Implication: if we crash before the writepage() data
1015 			 * is written into the filesystem, recovery will replay
1016 			 * the write() data.
1017 			 */
1018 			if (jh->b_jlist != BJ_None &&
1019 					jh->b_jlist != BJ_SyncData &&
1020 					jh->b_jlist != BJ_Locked) {
1021 				JBUFFER_TRACE(jh, "Not stealing");
1022 				goto no_journal;
1023 			}
1024 
1025 			/*
1026 			 * This buffer may be undergoing writeout in commit.  We
1027 			 * can't return from here and let the caller dirty it
1028 			 * again because that can cause the write-out loop in
1029 			 * commit to never terminate.
1030 			 */
1031 			if (buffer_dirty(bh)) {
1032 				get_bh(bh);
1033 				spin_unlock(&journal->j_list_lock);
1034 				jbd_unlock_bh_state(bh);
1035 				need_brelse = 1;
1036 				sync_dirty_buffer(bh);
1037 				jbd_lock_bh_state(bh);
1038 				spin_lock(&journal->j_list_lock);
1039 				/* Since we dropped the lock... */
1040 				if (!buffer_mapped(bh)) {
1041 					JBUFFER_TRACE(jh, "buffer got unmapped");
1042 					goto no_journal;
1043 				}
1044 				/* The buffer may become locked again at any
1045 				   time if it is redirtied */
1046 			}
1047 
1048 			/* journal_clean_data_list() may have got there first */
1049 			if (jh->b_transaction != NULL) {
1050 				JBUFFER_TRACE(jh, "unfile from commit");
1051 				__jbd2_journal_temp_unlink_buffer(jh);
1052 				/* It still points to the committing
1053 				 * transaction; move it to this one so
1054 				 * that the refile assert checks are
1055 				 * happy. */
1056 				jh->b_transaction = handle->h_transaction;
1057 			}
1058 			/* The buffer will be refiled below */
1059 
1060 		}
1061 		/*
1062 		 * Special case --- the buffer might actually have been
1063 		 * allocated and then immediately deallocated in the previous,
1064 		 * committing transaction, so might still be left on that
1065 		 * transaction's metadata lists.
1066 		 */
1067 		if (jh->b_jlist != BJ_SyncData && jh->b_jlist != BJ_Locked) {
1068 			JBUFFER_TRACE(jh, "not on correct data list: unfile");
1069 			J_ASSERT_JH(jh, jh->b_jlist != BJ_Shadow);
1070 			__jbd2_journal_temp_unlink_buffer(jh);
1071 			jh->b_transaction = handle->h_transaction;
1072 			JBUFFER_TRACE(jh, "file as data");
1073 			__jbd2_journal_file_buffer(jh, handle->h_transaction,
1074 						BJ_SyncData);
1075 		}
1076 	} else {
1077 		JBUFFER_TRACE(jh, "not on a transaction");
1078 		__jbd2_journal_file_buffer(jh, handle->h_transaction, BJ_SyncData);
1079 	}
1080 no_journal:
1081 	spin_unlock(&journal->j_list_lock);
1082 	jbd_unlock_bh_state(bh);
1083 	if (need_brelse) {
1084 		BUFFER_TRACE(bh, "brelse");
1085 		__brelse(bh);
1086 	}
1087 	JBUFFER_TRACE(jh, "exit");
1088 	jbd2_journal_put_journal_head(jh);
1089 	return 0;
1090 }
1091 
1092 /**
1093  * int jbd2_journal_dirty_metadata() -  mark a buffer as containing dirty metadata
1094  * @handle: transaction to add buffer to.
1095  * @bh: buffer to mark
1096  *
1097  * mark dirty metadata which needs to be journaled as part of the current
1098  * transaction.
1099  *
1100  * The buffer is placed on the transaction's metadata list and is marked
1101  * as belonging to the transaction.
1102  *
1103  * Returns error number or 0 on success.
1104  *
1105  * Special care needs to be taken if the buffer already belongs to the
1106  * current committing transaction (in which case we should have frozen
1107  * data present for that commit).  In that case, we don't relink the
1108  * buffer: that only gets done when the old transaction finally
1109  * completes its commit.
1110  */
1111 int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
1112 {
1113 	transaction_t *transaction = handle->h_transaction;
1114 	journal_t *journal = transaction->t_journal;
1115 	struct journal_head *jh = bh2jh(bh);
1116 
1117 	jbd_debug(5, "journal_head %p\n", jh);
1118 	JBUFFER_TRACE(jh, "entry");
1119 	if (is_handle_aborted(handle))
1120 		goto out;
1121 
1122 	jbd_lock_bh_state(bh);
1123 
1124 	if (jh->b_modified == 0) {
1125 		/*
1126 		 * This buffer's got modified and becoming part
1127 		 * of the transaction. This needs to be done
1128 		 * once a transaction -bzzz
1129 		 */
1130 		jh->b_modified = 1;
1131 		J_ASSERT_JH(jh, handle->h_buffer_credits > 0);
1132 		handle->h_buffer_credits--;
1133 	}
1134 
1135 	/*
1136 	 * fastpath, to avoid expensive locking.  If this buffer is already
1137 	 * on the running transaction's metadata list there is nothing to do.
1138 	 * Nobody can take it off again because there is a handle open.
1139 	 * I _think_ we're OK here with SMP barriers - a mistaken decision will
1140 	 * result in this test being false, so we go in and take the locks.
1141 	 */
1142 	if (jh->b_transaction == transaction && jh->b_jlist == BJ_Metadata) {
1143 		JBUFFER_TRACE(jh, "fastpath");
1144 		J_ASSERT_JH(jh, jh->b_transaction ==
1145 					journal->j_running_transaction);
1146 		goto out_unlock_bh;
1147 	}
1148 
1149 	set_buffer_jbddirty(bh);
1150 
1151 	/*
1152 	 * Metadata already on the current transaction list doesn't
1153 	 * need to be filed.  Metadata on another transaction's list must
1154 	 * be committing, and will be refiled once the commit completes:
1155 	 * leave it alone for now.
1156 	 */
1157 	if (jh->b_transaction != transaction) {
1158 		JBUFFER_TRACE(jh, "already on other transaction");
1159 		J_ASSERT_JH(jh, jh->b_transaction ==
1160 					journal->j_committing_transaction);
1161 		J_ASSERT_JH(jh, jh->b_next_transaction == transaction);
1162 		/* And this case is illegal: we can't reuse another
1163 		 * transaction's data buffer, ever. */
1164 		goto out_unlock_bh;
1165 	}
1166 
1167 	/* That test should have eliminated the following case: */
1168 	J_ASSERT_JH(jh, jh->b_frozen_data == 0);
1169 
1170 	JBUFFER_TRACE(jh, "file as BJ_Metadata");
1171 	spin_lock(&journal->j_list_lock);
1172 	__jbd2_journal_file_buffer(jh, handle->h_transaction, BJ_Metadata);
1173 	spin_unlock(&journal->j_list_lock);
1174 out_unlock_bh:
1175 	jbd_unlock_bh_state(bh);
1176 out:
1177 	JBUFFER_TRACE(jh, "exit");
1178 	return 0;
1179 }
1180 
1181 /*
1182  * jbd2_journal_release_buffer: undo a get_write_access without any buffer
1183  * updates, if the update decided in the end that it didn't need access.
1184  *
1185  */
1186 void
1187 jbd2_journal_release_buffer(handle_t *handle, struct buffer_head *bh)
1188 {
1189 	BUFFER_TRACE(bh, "entry");
1190 }
1191 
1192 /**
1193  * void jbd2_journal_forget() - bforget() for potentially-journaled buffers.
1194  * @handle: transaction handle
1195  * @bh:     bh to 'forget'
1196  *
1197  * We can only do the bforget if there are no commits pending against the
1198  * buffer.  If the buffer is dirty in the current running transaction we
1199  * can safely unlink it.
1200  *
1201  * bh may not be a journalled buffer at all - it may be a non-JBD
1202  * buffer which came off the hashtable.  Check for this.
1203  *
1204  * Decrements bh->b_count by one.
1205  *
1206  * Allow this call even if the handle has aborted --- it may be part of
1207  * the caller's cleanup after an abort.
1208  */
1209 int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh)
1210 {
1211 	transaction_t *transaction = handle->h_transaction;
1212 	journal_t *journal = transaction->t_journal;
1213 	struct journal_head *jh;
1214 	int drop_reserve = 0;
1215 	int err = 0;
1216 
1217 	BUFFER_TRACE(bh, "entry");
1218 
1219 	jbd_lock_bh_state(bh);
1220 	spin_lock(&journal->j_list_lock);
1221 
1222 	if (!buffer_jbd(bh))
1223 		goto not_jbd;
1224 	jh = bh2jh(bh);
1225 
1226 	/* Critical error: attempting to delete a bitmap buffer, maybe?
1227 	 * Don't do any jbd operations, and return an error. */
1228 	if (!J_EXPECT_JH(jh, !jh->b_committed_data,
1229 			 "inconsistent data on disk")) {
1230 		err = -EIO;
1231 		goto not_jbd;
1232 	}
1233 
1234 	/*
1235 	 * The buffer's going from the transaction, we must drop
1236 	 * all references -bzzz
1237 	 */
1238 	jh->b_modified = 0;
1239 
1240 	if (jh->b_transaction == handle->h_transaction) {
1241 		J_ASSERT_JH(jh, !jh->b_frozen_data);
1242 
1243 		/* If we are forgetting a buffer which is already part
1244 		 * of this transaction, then we can just drop it from
1245 		 * the transaction immediately. */
1246 		clear_buffer_dirty(bh);
1247 		clear_buffer_jbddirty(bh);
1248 
1249 		JBUFFER_TRACE(jh, "belongs to current transaction: unfile");
1250 
1251 		drop_reserve = 1;
1252 
1253 		/*
1254 		 * We are no longer going to journal this buffer.
1255 		 * However, the commit of this transaction is still
1256 		 * important to the buffer: the delete that we are now
1257 		 * processing might obsolete an old log entry, so by
1258 		 * committing, we can satisfy the buffer's checkpoint.
1259 		 *
1260 		 * So, if we have a checkpoint on the buffer, we should
1261 		 * now refile the buffer on our BJ_Forget list so that
1262 		 * we know to remove the checkpoint after we commit.
1263 		 */
1264 
1265 		if (jh->b_cp_transaction) {
1266 			__jbd2_journal_temp_unlink_buffer(jh);
1267 			__jbd2_journal_file_buffer(jh, transaction, BJ_Forget);
1268 		} else {
1269 			__jbd2_journal_unfile_buffer(jh);
1270 			jbd2_journal_remove_journal_head(bh);
1271 			__brelse(bh);
1272 			if (!buffer_jbd(bh)) {
1273 				spin_unlock(&journal->j_list_lock);
1274 				jbd_unlock_bh_state(bh);
1275 				__bforget(bh);
1276 				goto drop;
1277 			}
1278 		}
1279 	} else if (jh->b_transaction) {
1280 		J_ASSERT_JH(jh, (jh->b_transaction ==
1281 				 journal->j_committing_transaction));
1282 		/* However, if the buffer is still owned by a prior
1283 		 * (committing) transaction, we can't drop it yet... */
1284 		JBUFFER_TRACE(jh, "belongs to older transaction");
1285 		/* ... but we CAN drop it from the new transaction if we
1286 		 * have also modified it since the original commit. */
1287 
1288 		if (jh->b_next_transaction) {
1289 			J_ASSERT(jh->b_next_transaction == transaction);
1290 			jh->b_next_transaction = NULL;
1291 			drop_reserve = 1;
1292 		}
1293 	}
1294 
1295 not_jbd:
1296 	spin_unlock(&journal->j_list_lock);
1297 	jbd_unlock_bh_state(bh);
1298 	__brelse(bh);
1299 drop:
1300 	if (drop_reserve) {
1301 		/* no need to reserve log space for this block -bzzz */
1302 		handle->h_buffer_credits++;
1303 	}
1304 	return err;
1305 }
1306 
1307 /**
1308  * int jbd2_journal_stop() - complete a transaction
1309  * @handle: tranaction to complete.
1310  *
1311  * All done for a particular handle.
1312  *
1313  * There is not much action needed here.  We just return any remaining
1314  * buffer credits to the transaction and remove the handle.  The only
1315  * complication is that we need to start a commit operation if the
1316  * filesystem is marked for synchronous update.
1317  *
1318  * jbd2_journal_stop itself will not usually return an error, but it may
1319  * do so in unusual circumstances.  In particular, expect it to
1320  * return -EIO if a jbd2_journal_abort has been executed since the
1321  * transaction began.
1322  */
1323 int jbd2_journal_stop(handle_t *handle)
1324 {
1325 	transaction_t *transaction = handle->h_transaction;
1326 	journal_t *journal = transaction->t_journal;
1327 	int old_handle_count, err;
1328 	pid_t pid;
1329 
1330 	J_ASSERT(journal_current_handle() == handle);
1331 
1332 	if (is_handle_aborted(handle))
1333 		err = -EIO;
1334 	else {
1335 		J_ASSERT(transaction->t_updates > 0);
1336 		err = 0;
1337 	}
1338 
1339 	if (--handle->h_ref > 0) {
1340 		jbd_debug(4, "h_ref %d -> %d\n", handle->h_ref + 1,
1341 			  handle->h_ref);
1342 		return err;
1343 	}
1344 
1345 	jbd_debug(4, "Handle %p going down\n", handle);
1346 
1347 	/*
1348 	 * Implement synchronous transaction batching.  If the handle
1349 	 * was synchronous, don't force a commit immediately.  Let's
1350 	 * yield and let another thread piggyback onto this transaction.
1351 	 * Keep doing that while new threads continue to arrive.
1352 	 * It doesn't cost much - we're about to run a commit and sleep
1353 	 * on IO anyway.  Speeds up many-threaded, many-dir operations
1354 	 * by 30x or more...
1355 	 *
1356 	 * But don't do this if this process was the most recent one to
1357 	 * perform a synchronous write.  We do this to detect the case where a
1358 	 * single process is doing a stream of sync writes.  No point in waiting
1359 	 * for joiners in that case.
1360 	 */
1361 	pid = current->pid;
1362 	if (handle->h_sync && journal->j_last_sync_writer != pid) {
1363 		journal->j_last_sync_writer = pid;
1364 		do {
1365 			old_handle_count = transaction->t_handle_count;
1366 			schedule_timeout_uninterruptible(1);
1367 		} while (old_handle_count != transaction->t_handle_count);
1368 	}
1369 
1370 	current->journal_info = NULL;
1371 	spin_lock(&journal->j_state_lock);
1372 	spin_lock(&transaction->t_handle_lock);
1373 	transaction->t_outstanding_credits -= handle->h_buffer_credits;
1374 	transaction->t_updates--;
1375 	if (!transaction->t_updates) {
1376 		wake_up(&journal->j_wait_updates);
1377 		if (journal->j_barrier_count)
1378 			wake_up(&journal->j_wait_transaction_locked);
1379 	}
1380 
1381 	/*
1382 	 * If the handle is marked SYNC, we need to set another commit
1383 	 * going!  We also want to force a commit if the current
1384 	 * transaction is occupying too much of the log, or if the
1385 	 * transaction is too old now.
1386 	 */
1387 	if (handle->h_sync ||
1388 			transaction->t_outstanding_credits >
1389 				journal->j_max_transaction_buffers ||
1390 			time_after_eq(jiffies, transaction->t_expires)) {
1391 		/* Do this even for aborted journals: an abort still
1392 		 * completes the commit thread, it just doesn't write
1393 		 * anything to disk. */
1394 		tid_t tid = transaction->t_tid;
1395 
1396 		spin_unlock(&transaction->t_handle_lock);
1397 		jbd_debug(2, "transaction too old, requesting commit for "
1398 					"handle %p\n", handle);
1399 		/* This is non-blocking */
1400 		__jbd2_log_start_commit(journal, transaction->t_tid);
1401 		spin_unlock(&journal->j_state_lock);
1402 
1403 		/*
1404 		 * Special case: JBD2_SYNC synchronous updates require us
1405 		 * to wait for the commit to complete.
1406 		 */
1407 		if (handle->h_sync && !(current->flags & PF_MEMALLOC))
1408 			err = jbd2_log_wait_commit(journal, tid);
1409 	} else {
1410 		spin_unlock(&transaction->t_handle_lock);
1411 		spin_unlock(&journal->j_state_lock);
1412 	}
1413 
1414 	jbd_free_handle(handle);
1415 	return err;
1416 }
1417 
1418 /**int jbd2_journal_force_commit() - force any uncommitted transactions
1419  * @journal: journal to force
1420  *
1421  * For synchronous operations: force any uncommitted transactions
1422  * to disk.  May seem kludgy, but it reuses all the handle batching
1423  * code in a very simple manner.
1424  */
1425 int jbd2_journal_force_commit(journal_t *journal)
1426 {
1427 	handle_t *handle;
1428 	int ret;
1429 
1430 	handle = jbd2_journal_start(journal, 1);
1431 	if (IS_ERR(handle)) {
1432 		ret = PTR_ERR(handle);
1433 	} else {
1434 		handle->h_sync = 1;
1435 		ret = jbd2_journal_stop(handle);
1436 	}
1437 	return ret;
1438 }
1439 
1440 /*
1441  *
1442  * List management code snippets: various functions for manipulating the
1443  * transaction buffer lists.
1444  *
1445  */
1446 
1447 /*
1448  * Append a buffer to a transaction list, given the transaction's list head
1449  * pointer.
1450  *
1451  * j_list_lock is held.
1452  *
1453  * jbd_lock_bh_state(jh2bh(jh)) is held.
1454  */
1455 
1456 static inline void
1457 __blist_add_buffer(struct journal_head **list, struct journal_head *jh)
1458 {
1459 	if (!*list) {
1460 		jh->b_tnext = jh->b_tprev = jh;
1461 		*list = jh;
1462 	} else {
1463 		/* Insert at the tail of the list to preserve order */
1464 		struct journal_head *first = *list, *last = first->b_tprev;
1465 		jh->b_tprev = last;
1466 		jh->b_tnext = first;
1467 		last->b_tnext = first->b_tprev = jh;
1468 	}
1469 }
1470 
1471 /*
1472  * Remove a buffer from a transaction list, given the transaction's list
1473  * head pointer.
1474  *
1475  * Called with j_list_lock held, and the journal may not be locked.
1476  *
1477  * jbd_lock_bh_state(jh2bh(jh)) is held.
1478  */
1479 
1480 static inline void
1481 __blist_del_buffer(struct journal_head **list, struct journal_head *jh)
1482 {
1483 	if (*list == jh) {
1484 		*list = jh->b_tnext;
1485 		if (*list == jh)
1486 			*list = NULL;
1487 	}
1488 	jh->b_tprev->b_tnext = jh->b_tnext;
1489 	jh->b_tnext->b_tprev = jh->b_tprev;
1490 }
1491 
1492 /*
1493  * Remove a buffer from the appropriate transaction list.
1494  *
1495  * Note that this function can *change* the value of
1496  * bh->b_transaction->t_sync_datalist, t_buffers, t_forget,
1497  * t_iobuf_list, t_shadow_list, t_log_list or t_reserved_list.  If the caller
1498  * is holding onto a copy of one of thee pointers, it could go bad.
1499  * Generally the caller needs to re-read the pointer from the transaction_t.
1500  *
1501  * Called under j_list_lock.  The journal may not be locked.
1502  */
1503 void __jbd2_journal_temp_unlink_buffer(struct journal_head *jh)
1504 {
1505 	struct journal_head **list = NULL;
1506 	transaction_t *transaction;
1507 	struct buffer_head *bh = jh2bh(jh);
1508 
1509 	J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
1510 	transaction = jh->b_transaction;
1511 	if (transaction)
1512 		assert_spin_locked(&transaction->t_journal->j_list_lock);
1513 
1514 	J_ASSERT_JH(jh, jh->b_jlist < BJ_Types);
1515 	if (jh->b_jlist != BJ_None)
1516 		J_ASSERT_JH(jh, transaction != 0);
1517 
1518 	switch (jh->b_jlist) {
1519 	case BJ_None:
1520 		return;
1521 	case BJ_SyncData:
1522 		list = &transaction->t_sync_datalist;
1523 		break;
1524 	case BJ_Metadata:
1525 		transaction->t_nr_buffers--;
1526 		J_ASSERT_JH(jh, transaction->t_nr_buffers >= 0);
1527 		list = &transaction->t_buffers;
1528 		break;
1529 	case BJ_Forget:
1530 		list = &transaction->t_forget;
1531 		break;
1532 	case BJ_IO:
1533 		list = &transaction->t_iobuf_list;
1534 		break;
1535 	case BJ_Shadow:
1536 		list = &transaction->t_shadow_list;
1537 		break;
1538 	case BJ_LogCtl:
1539 		list = &transaction->t_log_list;
1540 		break;
1541 	case BJ_Reserved:
1542 		list = &transaction->t_reserved_list;
1543 		break;
1544 	case BJ_Locked:
1545 		list = &transaction->t_locked_list;
1546 		break;
1547 	}
1548 
1549 	__blist_del_buffer(list, jh);
1550 	jh->b_jlist = BJ_None;
1551 	if (test_clear_buffer_jbddirty(bh))
1552 		mark_buffer_dirty(bh);	/* Expose it to the VM */
1553 }
1554 
1555 void __jbd2_journal_unfile_buffer(struct journal_head *jh)
1556 {
1557 	__jbd2_journal_temp_unlink_buffer(jh);
1558 	jh->b_transaction = NULL;
1559 }
1560 
1561 void jbd2_journal_unfile_buffer(journal_t *journal, struct journal_head *jh)
1562 {
1563 	jbd_lock_bh_state(jh2bh(jh));
1564 	spin_lock(&journal->j_list_lock);
1565 	__jbd2_journal_unfile_buffer(jh);
1566 	spin_unlock(&journal->j_list_lock);
1567 	jbd_unlock_bh_state(jh2bh(jh));
1568 }
1569 
1570 /*
1571  * Called from jbd2_journal_try_to_free_buffers().
1572  *
1573  * Called under jbd_lock_bh_state(bh)
1574  */
1575 static void
1576 __journal_try_to_free_buffer(journal_t *journal, struct buffer_head *bh)
1577 {
1578 	struct journal_head *jh;
1579 
1580 	jh = bh2jh(bh);
1581 
1582 	if (buffer_locked(bh) || buffer_dirty(bh))
1583 		goto out;
1584 
1585 	if (jh->b_next_transaction != 0)
1586 		goto out;
1587 
1588 	spin_lock(&journal->j_list_lock);
1589 	if (jh->b_transaction != 0 && jh->b_cp_transaction == 0) {
1590 		if (jh->b_jlist == BJ_SyncData || jh->b_jlist == BJ_Locked) {
1591 			/* A written-back ordered data buffer */
1592 			JBUFFER_TRACE(jh, "release data");
1593 			__jbd2_journal_unfile_buffer(jh);
1594 			jbd2_journal_remove_journal_head(bh);
1595 			__brelse(bh);
1596 		}
1597 	} else if (jh->b_cp_transaction != 0 && jh->b_transaction == 0) {
1598 		/* written-back checkpointed metadata buffer */
1599 		if (jh->b_jlist == BJ_None) {
1600 			JBUFFER_TRACE(jh, "remove from checkpoint list");
1601 			__jbd2_journal_remove_checkpoint(jh);
1602 			jbd2_journal_remove_journal_head(bh);
1603 			__brelse(bh);
1604 		}
1605 	}
1606 	spin_unlock(&journal->j_list_lock);
1607 out:
1608 	return;
1609 }
1610 
1611 
1612 /**
1613  * int jbd2_journal_try_to_free_buffers() - try to free page buffers.
1614  * @journal: journal for operation
1615  * @page: to try and free
1616  * @unused_gfp_mask: unused
1617  *
1618  *
1619  * For all the buffers on this page,
1620  * if they are fully written out ordered data, move them onto BUF_CLEAN
1621  * so try_to_free_buffers() can reap them.
1622  *
1623  * This function returns non-zero if we wish try_to_free_buffers()
1624  * to be called. We do this if the page is releasable by try_to_free_buffers().
1625  * We also do it if the page has locked or dirty buffers and the caller wants
1626  * us to perform sync or async writeout.
1627  *
1628  * This complicates JBD locking somewhat.  We aren't protected by the
1629  * BKL here.  We wish to remove the buffer from its committing or
1630  * running transaction's ->t_datalist via __jbd2_journal_unfile_buffer.
1631  *
1632  * This may *change* the value of transaction_t->t_datalist, so anyone
1633  * who looks at t_datalist needs to lock against this function.
1634  *
1635  * Even worse, someone may be doing a jbd2_journal_dirty_data on this
1636  * buffer.  So we need to lock against that.  jbd2_journal_dirty_data()
1637  * will come out of the lock with the buffer dirty, which makes it
1638  * ineligible for release here.
1639  *
1640  * Who else is affected by this?  hmm...  Really the only contender
1641  * is do_get_write_access() - it could be looking at the buffer while
1642  * journal_try_to_free_buffer() is changing its state.  But that
1643  * cannot happen because we never reallocate freed data as metadata
1644  * while the data is part of a transaction.  Yes?
1645  */
1646 int jbd2_journal_try_to_free_buffers(journal_t *journal,
1647 				struct page *page, gfp_t unused_gfp_mask)
1648 {
1649 	struct buffer_head *head;
1650 	struct buffer_head *bh;
1651 	int ret = 0;
1652 
1653 	J_ASSERT(PageLocked(page));
1654 
1655 	head = page_buffers(page);
1656 	bh = head;
1657 	do {
1658 		struct journal_head *jh;
1659 
1660 		/*
1661 		 * We take our own ref against the journal_head here to avoid
1662 		 * having to add tons of locking around each instance of
1663 		 * jbd2_journal_remove_journal_head() and jbd2_journal_put_journal_head().
1664 		 */
1665 		jh = jbd2_journal_grab_journal_head(bh);
1666 		if (!jh)
1667 			continue;
1668 
1669 		jbd_lock_bh_state(bh);
1670 		__journal_try_to_free_buffer(journal, bh);
1671 		jbd2_journal_put_journal_head(jh);
1672 		jbd_unlock_bh_state(bh);
1673 		if (buffer_jbd(bh))
1674 			goto busy;
1675 	} while ((bh = bh->b_this_page) != head);
1676 	ret = try_to_free_buffers(page);
1677 busy:
1678 	return ret;
1679 }
1680 
1681 /*
1682  * This buffer is no longer needed.  If it is on an older transaction's
1683  * checkpoint list we need to record it on this transaction's forget list
1684  * to pin this buffer (and hence its checkpointing transaction) down until
1685  * this transaction commits.  If the buffer isn't on a checkpoint list, we
1686  * release it.
1687  * Returns non-zero if JBD no longer has an interest in the buffer.
1688  *
1689  * Called under j_list_lock.
1690  *
1691  * Called under jbd_lock_bh_state(bh).
1692  */
1693 static int __dispose_buffer(struct journal_head *jh, transaction_t *transaction)
1694 {
1695 	int may_free = 1;
1696 	struct buffer_head *bh = jh2bh(jh);
1697 
1698 	__jbd2_journal_unfile_buffer(jh);
1699 
1700 	if (jh->b_cp_transaction) {
1701 		JBUFFER_TRACE(jh, "on running+cp transaction");
1702 		__jbd2_journal_file_buffer(jh, transaction, BJ_Forget);
1703 		clear_buffer_jbddirty(bh);
1704 		may_free = 0;
1705 	} else {
1706 		JBUFFER_TRACE(jh, "on running transaction");
1707 		jbd2_journal_remove_journal_head(bh);
1708 		__brelse(bh);
1709 	}
1710 	return may_free;
1711 }
1712 
1713 /*
1714  * jbd2_journal_invalidatepage
1715  *
1716  * This code is tricky.  It has a number of cases to deal with.
1717  *
1718  * There are two invariants which this code relies on:
1719  *
1720  * i_size must be updated on disk before we start calling invalidatepage on the
1721  * data.
1722  *
1723  *  This is done in ext3 by defining an ext3_setattr method which
1724  *  updates i_size before truncate gets going.  By maintaining this
1725  *  invariant, we can be sure that it is safe to throw away any buffers
1726  *  attached to the current transaction: once the transaction commits,
1727  *  we know that the data will not be needed.
1728  *
1729  *  Note however that we can *not* throw away data belonging to the
1730  *  previous, committing transaction!
1731  *
1732  * Any disk blocks which *are* part of the previous, committing
1733  * transaction (and which therefore cannot be discarded immediately) are
1734  * not going to be reused in the new running transaction
1735  *
1736  *  The bitmap committed_data images guarantee this: any block which is
1737  *  allocated in one transaction and removed in the next will be marked
1738  *  as in-use in the committed_data bitmap, so cannot be reused until
1739  *  the next transaction to delete the block commits.  This means that
1740  *  leaving committing buffers dirty is quite safe: the disk blocks
1741  *  cannot be reallocated to a different file and so buffer aliasing is
1742  *  not possible.
1743  *
1744  *
1745  * The above applies mainly to ordered data mode.  In writeback mode we
1746  * don't make guarantees about the order in which data hits disk --- in
1747  * particular we don't guarantee that new dirty data is flushed before
1748  * transaction commit --- so it is always safe just to discard data
1749  * immediately in that mode.  --sct
1750  */
1751 
1752 /*
1753  * The journal_unmap_buffer helper function returns zero if the buffer
1754  * concerned remains pinned as an anonymous buffer belonging to an older
1755  * transaction.
1756  *
1757  * We're outside-transaction here.  Either or both of j_running_transaction
1758  * and j_committing_transaction may be NULL.
1759  */
1760 static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh)
1761 {
1762 	transaction_t *transaction;
1763 	struct journal_head *jh;
1764 	int may_free = 1;
1765 	int ret;
1766 
1767 	BUFFER_TRACE(bh, "entry");
1768 
1769 	/*
1770 	 * It is safe to proceed here without the j_list_lock because the
1771 	 * buffers cannot be stolen by try_to_free_buffers as long as we are
1772 	 * holding the page lock. --sct
1773 	 */
1774 
1775 	if (!buffer_jbd(bh))
1776 		goto zap_buffer_unlocked;
1777 
1778 	spin_lock(&journal->j_state_lock);
1779 	jbd_lock_bh_state(bh);
1780 	spin_lock(&journal->j_list_lock);
1781 
1782 	jh = jbd2_journal_grab_journal_head(bh);
1783 	if (!jh)
1784 		goto zap_buffer_no_jh;
1785 
1786 	transaction = jh->b_transaction;
1787 	if (transaction == NULL) {
1788 		/* First case: not on any transaction.  If it
1789 		 * has no checkpoint link, then we can zap it:
1790 		 * it's a writeback-mode buffer so we don't care
1791 		 * if it hits disk safely. */
1792 		if (!jh->b_cp_transaction) {
1793 			JBUFFER_TRACE(jh, "not on any transaction: zap");
1794 			goto zap_buffer;
1795 		}
1796 
1797 		if (!buffer_dirty(bh)) {
1798 			/* bdflush has written it.  We can drop it now */
1799 			goto zap_buffer;
1800 		}
1801 
1802 		/* OK, it must be in the journal but still not
1803 		 * written fully to disk: it's metadata or
1804 		 * journaled data... */
1805 
1806 		if (journal->j_running_transaction) {
1807 			/* ... and once the current transaction has
1808 			 * committed, the buffer won't be needed any
1809 			 * longer. */
1810 			JBUFFER_TRACE(jh, "checkpointed: add to BJ_Forget");
1811 			ret = __dispose_buffer(jh,
1812 					journal->j_running_transaction);
1813 			jbd2_journal_put_journal_head(jh);
1814 			spin_unlock(&journal->j_list_lock);
1815 			jbd_unlock_bh_state(bh);
1816 			spin_unlock(&journal->j_state_lock);
1817 			return ret;
1818 		} else {
1819 			/* There is no currently-running transaction. So the
1820 			 * orphan record which we wrote for this file must have
1821 			 * passed into commit.  We must attach this buffer to
1822 			 * the committing transaction, if it exists. */
1823 			if (journal->j_committing_transaction) {
1824 				JBUFFER_TRACE(jh, "give to committing trans");
1825 				ret = __dispose_buffer(jh,
1826 					journal->j_committing_transaction);
1827 				jbd2_journal_put_journal_head(jh);
1828 				spin_unlock(&journal->j_list_lock);
1829 				jbd_unlock_bh_state(bh);
1830 				spin_unlock(&journal->j_state_lock);
1831 				return ret;
1832 			} else {
1833 				/* The orphan record's transaction has
1834 				 * committed.  We can cleanse this buffer */
1835 				clear_buffer_jbddirty(bh);
1836 				goto zap_buffer;
1837 			}
1838 		}
1839 	} else if (transaction == journal->j_committing_transaction) {
1840 		JBUFFER_TRACE(jh, "on committing transaction");
1841 		if (jh->b_jlist == BJ_Locked) {
1842 			/*
1843 			 * The buffer is on the committing transaction's locked
1844 			 * list.  We have the buffer locked, so I/O has
1845 			 * completed.  So we can nail the buffer now.
1846 			 */
1847 			may_free = __dispose_buffer(jh, transaction);
1848 			goto zap_buffer;
1849 		}
1850 		/*
1851 		 * If it is committing, we simply cannot touch it.  We
1852 		 * can remove it's next_transaction pointer from the
1853 		 * running transaction if that is set, but nothing
1854 		 * else. */
1855 		set_buffer_freed(bh);
1856 		if (jh->b_next_transaction) {
1857 			J_ASSERT(jh->b_next_transaction ==
1858 					journal->j_running_transaction);
1859 			jh->b_next_transaction = NULL;
1860 		}
1861 		jbd2_journal_put_journal_head(jh);
1862 		spin_unlock(&journal->j_list_lock);
1863 		jbd_unlock_bh_state(bh);
1864 		spin_unlock(&journal->j_state_lock);
1865 		return 0;
1866 	} else {
1867 		/* Good, the buffer belongs to the running transaction.
1868 		 * We are writing our own transaction's data, not any
1869 		 * previous one's, so it is safe to throw it away
1870 		 * (remember that we expect the filesystem to have set
1871 		 * i_size already for this truncate so recovery will not
1872 		 * expose the disk blocks we are discarding here.) */
1873 		J_ASSERT_JH(jh, transaction == journal->j_running_transaction);
1874 		JBUFFER_TRACE(jh, "on running transaction");
1875 		may_free = __dispose_buffer(jh, transaction);
1876 	}
1877 
1878 zap_buffer:
1879 	jbd2_journal_put_journal_head(jh);
1880 zap_buffer_no_jh:
1881 	spin_unlock(&journal->j_list_lock);
1882 	jbd_unlock_bh_state(bh);
1883 	spin_unlock(&journal->j_state_lock);
1884 zap_buffer_unlocked:
1885 	clear_buffer_dirty(bh);
1886 	J_ASSERT_BH(bh, !buffer_jbddirty(bh));
1887 	clear_buffer_mapped(bh);
1888 	clear_buffer_req(bh);
1889 	clear_buffer_new(bh);
1890 	bh->b_bdev = NULL;
1891 	return may_free;
1892 }
1893 
1894 /**
1895  * void jbd2_journal_invalidatepage()
1896  * @journal: journal to use for flush...
1897  * @page:    page to flush
1898  * @offset:  length of page to invalidate.
1899  *
1900  * Reap page buffers containing data after offset in page.
1901  *
1902  */
1903 void jbd2_journal_invalidatepage(journal_t *journal,
1904 		      struct page *page,
1905 		      unsigned long offset)
1906 {
1907 	struct buffer_head *head, *bh, *next;
1908 	unsigned int curr_off = 0;
1909 	int may_free = 1;
1910 
1911 	if (!PageLocked(page))
1912 		BUG();
1913 	if (!page_has_buffers(page))
1914 		return;
1915 
1916 	/* We will potentially be playing with lists other than just the
1917 	 * data lists (especially for journaled data mode), so be
1918 	 * cautious in our locking. */
1919 
1920 	head = bh = page_buffers(page);
1921 	do {
1922 		unsigned int next_off = curr_off + bh->b_size;
1923 		next = bh->b_this_page;
1924 
1925 		if (offset <= curr_off) {
1926 			/* This block is wholly outside the truncation point */
1927 			lock_buffer(bh);
1928 			may_free &= journal_unmap_buffer(journal, bh);
1929 			unlock_buffer(bh);
1930 		}
1931 		curr_off = next_off;
1932 		bh = next;
1933 
1934 	} while (bh != head);
1935 
1936 	if (!offset) {
1937 		if (may_free && try_to_free_buffers(page))
1938 			J_ASSERT(!page_has_buffers(page));
1939 	}
1940 }
1941 
1942 /*
1943  * File a buffer on the given transaction list.
1944  */
1945 void __jbd2_journal_file_buffer(struct journal_head *jh,
1946 			transaction_t *transaction, int jlist)
1947 {
1948 	struct journal_head **list = NULL;
1949 	int was_dirty = 0;
1950 	struct buffer_head *bh = jh2bh(jh);
1951 
1952 	J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
1953 	assert_spin_locked(&transaction->t_journal->j_list_lock);
1954 
1955 	J_ASSERT_JH(jh, jh->b_jlist < BJ_Types);
1956 	J_ASSERT_JH(jh, jh->b_transaction == transaction ||
1957 				jh->b_transaction == 0);
1958 
1959 	if (jh->b_transaction && jh->b_jlist == jlist)
1960 		return;
1961 
1962 	/* The following list of buffer states needs to be consistent
1963 	 * with __jbd_unexpected_dirty_buffer()'s handling of dirty
1964 	 * state. */
1965 
1966 	if (jlist == BJ_Metadata || jlist == BJ_Reserved ||
1967 	    jlist == BJ_Shadow || jlist == BJ_Forget) {
1968 		if (test_clear_buffer_dirty(bh) ||
1969 		    test_clear_buffer_jbddirty(bh))
1970 			was_dirty = 1;
1971 	}
1972 
1973 	if (jh->b_transaction)
1974 		__jbd2_journal_temp_unlink_buffer(jh);
1975 	jh->b_transaction = transaction;
1976 
1977 	switch (jlist) {
1978 	case BJ_None:
1979 		J_ASSERT_JH(jh, !jh->b_committed_data);
1980 		J_ASSERT_JH(jh, !jh->b_frozen_data);
1981 		return;
1982 	case BJ_SyncData:
1983 		list = &transaction->t_sync_datalist;
1984 		break;
1985 	case BJ_Metadata:
1986 		transaction->t_nr_buffers++;
1987 		list = &transaction->t_buffers;
1988 		break;
1989 	case BJ_Forget:
1990 		list = &transaction->t_forget;
1991 		break;
1992 	case BJ_IO:
1993 		list = &transaction->t_iobuf_list;
1994 		break;
1995 	case BJ_Shadow:
1996 		list = &transaction->t_shadow_list;
1997 		break;
1998 	case BJ_LogCtl:
1999 		list = &transaction->t_log_list;
2000 		break;
2001 	case BJ_Reserved:
2002 		list = &transaction->t_reserved_list;
2003 		break;
2004 	case BJ_Locked:
2005 		list =  &transaction->t_locked_list;
2006 		break;
2007 	}
2008 
2009 	__blist_add_buffer(list, jh);
2010 	jh->b_jlist = jlist;
2011 
2012 	if (was_dirty)
2013 		set_buffer_jbddirty(bh);
2014 }
2015 
2016 void jbd2_journal_file_buffer(struct journal_head *jh,
2017 				transaction_t *transaction, int jlist)
2018 {
2019 	jbd_lock_bh_state(jh2bh(jh));
2020 	spin_lock(&transaction->t_journal->j_list_lock);
2021 	__jbd2_journal_file_buffer(jh, transaction, jlist);
2022 	spin_unlock(&transaction->t_journal->j_list_lock);
2023 	jbd_unlock_bh_state(jh2bh(jh));
2024 }
2025 
2026 /*
2027  * Remove a buffer from its current buffer list in preparation for
2028  * dropping it from its current transaction entirely.  If the buffer has
2029  * already started to be used by a subsequent transaction, refile the
2030  * buffer on that transaction's metadata list.
2031  *
2032  * Called under journal->j_list_lock
2033  *
2034  * Called under jbd_lock_bh_state(jh2bh(jh))
2035  */
2036 void __jbd2_journal_refile_buffer(struct journal_head *jh)
2037 {
2038 	int was_dirty;
2039 	struct buffer_head *bh = jh2bh(jh);
2040 
2041 	J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
2042 	if (jh->b_transaction)
2043 		assert_spin_locked(&jh->b_transaction->t_journal->j_list_lock);
2044 
2045 	/* If the buffer is now unused, just drop it. */
2046 	if (jh->b_next_transaction == NULL) {
2047 		__jbd2_journal_unfile_buffer(jh);
2048 		return;
2049 	}
2050 
2051 	/*
2052 	 * It has been modified by a later transaction: add it to the new
2053 	 * transaction's metadata list.
2054 	 */
2055 
2056 	was_dirty = test_clear_buffer_jbddirty(bh);
2057 	__jbd2_journal_temp_unlink_buffer(jh);
2058 	jh->b_transaction = jh->b_next_transaction;
2059 	jh->b_next_transaction = NULL;
2060 	__jbd2_journal_file_buffer(jh, jh->b_transaction,
2061 				was_dirty ? BJ_Metadata : BJ_Reserved);
2062 	J_ASSERT_JH(jh, jh->b_transaction->t_state == T_RUNNING);
2063 
2064 	if (was_dirty)
2065 		set_buffer_jbddirty(bh);
2066 }
2067 
2068 /*
2069  * For the unlocked version of this call, also make sure that any
2070  * hanging journal_head is cleaned up if necessary.
2071  *
2072  * __jbd2_journal_refile_buffer is usually called as part of a single locked
2073  * operation on a buffer_head, in which the caller is probably going to
2074  * be hooking the journal_head onto other lists.  In that case it is up
2075  * to the caller to remove the journal_head if necessary.  For the
2076  * unlocked jbd2_journal_refile_buffer call, the caller isn't going to be
2077  * doing anything else to the buffer so we need to do the cleanup
2078  * ourselves to avoid a jh leak.
2079  *
2080  * *** The journal_head may be freed by this call! ***
2081  */
2082 void jbd2_journal_refile_buffer(journal_t *journal, struct journal_head *jh)
2083 {
2084 	struct buffer_head *bh = jh2bh(jh);
2085 
2086 	jbd_lock_bh_state(bh);
2087 	spin_lock(&journal->j_list_lock);
2088 
2089 	__jbd2_journal_refile_buffer(jh);
2090 	jbd_unlock_bh_state(bh);
2091 	jbd2_journal_remove_journal_head(bh);
2092 
2093 	spin_unlock(&journal->j_list_lock);
2094 	__brelse(bh);
2095 }
2096