xref: /openbmc/linux/fs/jbd2/journal.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
1 /*
2  * linux/fs/jbd2/journal.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 journal-writing code; part of the ext2fs
13  * journaling system.
14  *
15  * This file manages journals: areas of disk reserved for logging
16  * transactional updates.  This includes the kernel journaling thread
17  * which is responsible for scheduling updates to the log.
18  *
19  * We do not actually manage the physical storage of the journal in this
20  * file: that is left to a per-journal policy function, which allows us
21  * to store the journal within a filesystem-specified area for ext2
22  * journaling (ext2 can use a reserved inode for storing the log).
23  */
24 
25 #include <linux/module.h>
26 #include <linux/time.h>
27 #include <linux/fs.h>
28 #include <linux/jbd2.h>
29 #include <linux/errno.h>
30 #include <linux/slab.h>
31 #include <linux/init.h>
32 #include <linux/mm.h>
33 #include <linux/freezer.h>
34 #include <linux/pagemap.h>
35 #include <linux/kthread.h>
36 #include <linux/poison.h>
37 #include <linux/proc_fs.h>
38 
39 #include <asm/uaccess.h>
40 #include <asm/page.h>
41 
42 EXPORT_SYMBOL(jbd2_journal_start);
43 EXPORT_SYMBOL(jbd2_journal_restart);
44 EXPORT_SYMBOL(jbd2_journal_extend);
45 EXPORT_SYMBOL(jbd2_journal_stop);
46 EXPORT_SYMBOL(jbd2_journal_lock_updates);
47 EXPORT_SYMBOL(jbd2_journal_unlock_updates);
48 EXPORT_SYMBOL(jbd2_journal_get_write_access);
49 EXPORT_SYMBOL(jbd2_journal_get_create_access);
50 EXPORT_SYMBOL(jbd2_journal_get_undo_access);
51 EXPORT_SYMBOL(jbd2_journal_dirty_data);
52 EXPORT_SYMBOL(jbd2_journal_dirty_metadata);
53 EXPORT_SYMBOL(jbd2_journal_release_buffer);
54 EXPORT_SYMBOL(jbd2_journal_forget);
55 #if 0
56 EXPORT_SYMBOL(journal_sync_buffer);
57 #endif
58 EXPORT_SYMBOL(jbd2_journal_flush);
59 EXPORT_SYMBOL(jbd2_journal_revoke);
60 
61 EXPORT_SYMBOL(jbd2_journal_init_dev);
62 EXPORT_SYMBOL(jbd2_journal_init_inode);
63 EXPORT_SYMBOL(jbd2_journal_update_format);
64 EXPORT_SYMBOL(jbd2_journal_check_used_features);
65 EXPORT_SYMBOL(jbd2_journal_check_available_features);
66 EXPORT_SYMBOL(jbd2_journal_set_features);
67 EXPORT_SYMBOL(jbd2_journal_create);
68 EXPORT_SYMBOL(jbd2_journal_load);
69 EXPORT_SYMBOL(jbd2_journal_destroy);
70 EXPORT_SYMBOL(jbd2_journal_update_superblock);
71 EXPORT_SYMBOL(jbd2_journal_abort);
72 EXPORT_SYMBOL(jbd2_journal_errno);
73 EXPORT_SYMBOL(jbd2_journal_ack_err);
74 EXPORT_SYMBOL(jbd2_journal_clear_err);
75 EXPORT_SYMBOL(jbd2_log_wait_commit);
76 EXPORT_SYMBOL(jbd2_journal_start_commit);
77 EXPORT_SYMBOL(jbd2_journal_force_commit_nested);
78 EXPORT_SYMBOL(jbd2_journal_wipe);
79 EXPORT_SYMBOL(jbd2_journal_blocks_per_page);
80 EXPORT_SYMBOL(jbd2_journal_invalidatepage);
81 EXPORT_SYMBOL(jbd2_journal_try_to_free_buffers);
82 EXPORT_SYMBOL(jbd2_journal_force_commit);
83 
84 static int journal_convert_superblock_v1(journal_t *, journal_superblock_t *);
85 static void __journal_abort_soft (journal_t *journal, int errno);
86 static int jbd2_journal_create_jbd_slab(size_t slab_size);
87 
88 /*
89  * Helper function used to manage commit timeouts
90  */
91 
92 static void commit_timeout(unsigned long __data)
93 {
94 	struct task_struct * p = (struct task_struct *) __data;
95 
96 	wake_up_process(p);
97 }
98 
99 /*
100  * kjournald2: The main thread function used to manage a logging device
101  * journal.
102  *
103  * This kernel thread is responsible for two things:
104  *
105  * 1) COMMIT:  Every so often we need to commit the current state of the
106  *    filesystem to disk.  The journal thread is responsible for writing
107  *    all of the metadata buffers to disk.
108  *
109  * 2) CHECKPOINT: We cannot reuse a used section of the log file until all
110  *    of the data in that part of the log has been rewritten elsewhere on
111  *    the disk.  Flushing these old buffers to reclaim space in the log is
112  *    known as checkpointing, and this thread is responsible for that job.
113  */
114 
115 static int kjournald2(void *arg)
116 {
117 	journal_t *journal = arg;
118 	transaction_t *transaction;
119 
120 	/*
121 	 * Set up an interval timer which can be used to trigger a commit wakeup
122 	 * after the commit interval expires
123 	 */
124 	setup_timer(&journal->j_commit_timer, commit_timeout,
125 			(unsigned long)current);
126 
127 	/* Record that the journal thread is running */
128 	journal->j_task = current;
129 	wake_up(&journal->j_wait_done_commit);
130 
131 	printk(KERN_INFO "kjournald2 starting.  Commit interval %ld seconds\n",
132 			journal->j_commit_interval / HZ);
133 
134 	/*
135 	 * And now, wait forever for commit wakeup events.
136 	 */
137 	spin_lock(&journal->j_state_lock);
138 
139 loop:
140 	if (journal->j_flags & JBD2_UNMOUNT)
141 		goto end_loop;
142 
143 	jbd_debug(1, "commit_sequence=%d, commit_request=%d\n",
144 		journal->j_commit_sequence, journal->j_commit_request);
145 
146 	if (journal->j_commit_sequence != journal->j_commit_request) {
147 		jbd_debug(1, "OK, requests differ\n");
148 		spin_unlock(&journal->j_state_lock);
149 		del_timer_sync(&journal->j_commit_timer);
150 		jbd2_journal_commit_transaction(journal);
151 		spin_lock(&journal->j_state_lock);
152 		goto loop;
153 	}
154 
155 	wake_up(&journal->j_wait_done_commit);
156 	if (freezing(current)) {
157 		/*
158 		 * The simpler the better. Flushing journal isn't a
159 		 * good idea, because that depends on threads that may
160 		 * be already stopped.
161 		 */
162 		jbd_debug(1, "Now suspending kjournald2\n");
163 		spin_unlock(&journal->j_state_lock);
164 		refrigerator();
165 		spin_lock(&journal->j_state_lock);
166 	} else {
167 		/*
168 		 * We assume on resume that commits are already there,
169 		 * so we don't sleep
170 		 */
171 		DEFINE_WAIT(wait);
172 		int should_sleep = 1;
173 
174 		prepare_to_wait(&journal->j_wait_commit, &wait,
175 				TASK_INTERRUPTIBLE);
176 		if (journal->j_commit_sequence != journal->j_commit_request)
177 			should_sleep = 0;
178 		transaction = journal->j_running_transaction;
179 		if (transaction && time_after_eq(jiffies,
180 						transaction->t_expires))
181 			should_sleep = 0;
182 		if (journal->j_flags & JBD2_UNMOUNT)
183 			should_sleep = 0;
184 		if (should_sleep) {
185 			spin_unlock(&journal->j_state_lock);
186 			schedule();
187 			spin_lock(&journal->j_state_lock);
188 		}
189 		finish_wait(&journal->j_wait_commit, &wait);
190 	}
191 
192 	jbd_debug(1, "kjournald2 wakes\n");
193 
194 	/*
195 	 * Were we woken up by a commit wakeup event?
196 	 */
197 	transaction = journal->j_running_transaction;
198 	if (transaction && time_after_eq(jiffies, transaction->t_expires)) {
199 		journal->j_commit_request = transaction->t_tid;
200 		jbd_debug(1, "woke because of timeout\n");
201 	}
202 	goto loop;
203 
204 end_loop:
205 	spin_unlock(&journal->j_state_lock);
206 	del_timer_sync(&journal->j_commit_timer);
207 	journal->j_task = NULL;
208 	wake_up(&journal->j_wait_done_commit);
209 	jbd_debug(1, "Journal thread exiting.\n");
210 	return 0;
211 }
212 
213 static int jbd2_journal_start_thread(journal_t *journal)
214 {
215 	struct task_struct *t;
216 
217 	t = kthread_run(kjournald2, journal, "kjournald2");
218 	if (IS_ERR(t))
219 		return PTR_ERR(t);
220 
221 	wait_event(journal->j_wait_done_commit, journal->j_task != 0);
222 	return 0;
223 }
224 
225 static void journal_kill_thread(journal_t *journal)
226 {
227 	spin_lock(&journal->j_state_lock);
228 	journal->j_flags |= JBD2_UNMOUNT;
229 
230 	while (journal->j_task) {
231 		wake_up(&journal->j_wait_commit);
232 		spin_unlock(&journal->j_state_lock);
233 		wait_event(journal->j_wait_done_commit, journal->j_task == 0);
234 		spin_lock(&journal->j_state_lock);
235 	}
236 	spin_unlock(&journal->j_state_lock);
237 }
238 
239 /*
240  * jbd2_journal_write_metadata_buffer: write a metadata buffer to the journal.
241  *
242  * Writes a metadata buffer to a given disk block.  The actual IO is not
243  * performed but a new buffer_head is constructed which labels the data
244  * to be written with the correct destination disk block.
245  *
246  * Any magic-number escaping which needs to be done will cause a
247  * copy-out here.  If the buffer happens to start with the
248  * JBD2_MAGIC_NUMBER, then we can't write it to the log directly: the
249  * magic number is only written to the log for descripter blocks.  In
250  * this case, we copy the data and replace the first word with 0, and we
251  * return a result code which indicates that this buffer needs to be
252  * marked as an escaped buffer in the corresponding log descriptor
253  * block.  The missing word can then be restored when the block is read
254  * during recovery.
255  *
256  * If the source buffer has already been modified by a new transaction
257  * since we took the last commit snapshot, we use the frozen copy of
258  * that data for IO.  If we end up using the existing buffer_head's data
259  * for the write, then we *have* to lock the buffer to prevent anyone
260  * else from using and possibly modifying it while the IO is in
261  * progress.
262  *
263  * The function returns a pointer to the buffer_heads to be used for IO.
264  *
265  * We assume that the journal has already been locked in this function.
266  *
267  * Return value:
268  *  <0: Error
269  * >=0: Finished OK
270  *
271  * On success:
272  * Bit 0 set == escape performed on the data
273  * Bit 1 set == buffer copy-out performed (kfree the data after IO)
274  */
275 
276 int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
277 				  struct journal_head  *jh_in,
278 				  struct journal_head **jh_out,
279 				  unsigned long long blocknr)
280 {
281 	int need_copy_out = 0;
282 	int done_copy_out = 0;
283 	int do_escape = 0;
284 	char *mapped_data;
285 	struct buffer_head *new_bh;
286 	struct journal_head *new_jh;
287 	struct page *new_page;
288 	unsigned int new_offset;
289 	struct buffer_head *bh_in = jh2bh(jh_in);
290 
291 	/*
292 	 * The buffer really shouldn't be locked: only the current committing
293 	 * transaction is allowed to write it, so nobody else is allowed
294 	 * to do any IO.
295 	 *
296 	 * akpm: except if we're journalling data, and write() output is
297 	 * also part of a shared mapping, and another thread has
298 	 * decided to launch a writepage() against this buffer.
299 	 */
300 	J_ASSERT_BH(bh_in, buffer_jbddirty(bh_in));
301 
302 	new_bh = alloc_buffer_head(GFP_NOFS|__GFP_NOFAIL);
303 
304 	/*
305 	 * If a new transaction has already done a buffer copy-out, then
306 	 * we use that version of the data for the commit.
307 	 */
308 	jbd_lock_bh_state(bh_in);
309 repeat:
310 	if (jh_in->b_frozen_data) {
311 		done_copy_out = 1;
312 		new_page = virt_to_page(jh_in->b_frozen_data);
313 		new_offset = offset_in_page(jh_in->b_frozen_data);
314 	} else {
315 		new_page = jh2bh(jh_in)->b_page;
316 		new_offset = offset_in_page(jh2bh(jh_in)->b_data);
317 	}
318 
319 	mapped_data = kmap_atomic(new_page, KM_USER0);
320 	/*
321 	 * Check for escaping
322 	 */
323 	if (*((__be32 *)(mapped_data + new_offset)) ==
324 				cpu_to_be32(JBD2_MAGIC_NUMBER)) {
325 		need_copy_out = 1;
326 		do_escape = 1;
327 	}
328 	kunmap_atomic(mapped_data, KM_USER0);
329 
330 	/*
331 	 * Do we need to do a data copy?
332 	 */
333 	if (need_copy_out && !done_copy_out) {
334 		char *tmp;
335 
336 		jbd_unlock_bh_state(bh_in);
337 		tmp = jbd2_slab_alloc(bh_in->b_size, GFP_NOFS);
338 		jbd_lock_bh_state(bh_in);
339 		if (jh_in->b_frozen_data) {
340 			jbd2_slab_free(tmp, bh_in->b_size);
341 			goto repeat;
342 		}
343 
344 		jh_in->b_frozen_data = tmp;
345 		mapped_data = kmap_atomic(new_page, KM_USER0);
346 		memcpy(tmp, mapped_data + new_offset, jh2bh(jh_in)->b_size);
347 		kunmap_atomic(mapped_data, KM_USER0);
348 
349 		new_page = virt_to_page(tmp);
350 		new_offset = offset_in_page(tmp);
351 		done_copy_out = 1;
352 	}
353 
354 	/*
355 	 * Did we need to do an escaping?  Now we've done all the
356 	 * copying, we can finally do so.
357 	 */
358 	if (do_escape) {
359 		mapped_data = kmap_atomic(new_page, KM_USER0);
360 		*((unsigned int *)(mapped_data + new_offset)) = 0;
361 		kunmap_atomic(mapped_data, KM_USER0);
362 	}
363 
364 	/* keep subsequent assertions sane */
365 	new_bh->b_state = 0;
366 	init_buffer(new_bh, NULL, NULL);
367 	atomic_set(&new_bh->b_count, 1);
368 	jbd_unlock_bh_state(bh_in);
369 
370 	new_jh = jbd2_journal_add_journal_head(new_bh);	/* This sleeps */
371 
372 	set_bh_page(new_bh, new_page, new_offset);
373 	new_jh->b_transaction = NULL;
374 	new_bh->b_size = jh2bh(jh_in)->b_size;
375 	new_bh->b_bdev = transaction->t_journal->j_dev;
376 	new_bh->b_blocknr = blocknr;
377 	set_buffer_mapped(new_bh);
378 	set_buffer_dirty(new_bh);
379 
380 	*jh_out = new_jh;
381 
382 	/*
383 	 * The to-be-written buffer needs to get moved to the io queue,
384 	 * and the original buffer whose contents we are shadowing or
385 	 * copying is moved to the transaction's shadow queue.
386 	 */
387 	JBUFFER_TRACE(jh_in, "file as BJ_Shadow");
388 	jbd2_journal_file_buffer(jh_in, transaction, BJ_Shadow);
389 	JBUFFER_TRACE(new_jh, "file as BJ_IO");
390 	jbd2_journal_file_buffer(new_jh, transaction, BJ_IO);
391 
392 	return do_escape | (done_copy_out << 1);
393 }
394 
395 /*
396  * Allocation code for the journal file.  Manage the space left in the
397  * journal, so that we can begin checkpointing when appropriate.
398  */
399 
400 /*
401  * __jbd2_log_space_left: Return the number of free blocks left in the journal.
402  *
403  * Called with the journal already locked.
404  *
405  * Called under j_state_lock
406  */
407 
408 int __jbd2_log_space_left(journal_t *journal)
409 {
410 	int left = journal->j_free;
411 
412 	assert_spin_locked(&journal->j_state_lock);
413 
414 	/*
415 	 * Be pessimistic here about the number of those free blocks which
416 	 * might be required for log descriptor control blocks.
417 	 */
418 
419 #define MIN_LOG_RESERVED_BLOCKS 32 /* Allow for rounding errors */
420 
421 	left -= MIN_LOG_RESERVED_BLOCKS;
422 
423 	if (left <= 0)
424 		return 0;
425 	left -= (left >> 3);
426 	return left;
427 }
428 
429 /*
430  * Called under j_state_lock.  Returns true if a transaction was started.
431  */
432 int __jbd2_log_start_commit(journal_t *journal, tid_t target)
433 {
434 	/*
435 	 * Are we already doing a recent enough commit?
436 	 */
437 	if (!tid_geq(journal->j_commit_request, target)) {
438 		/*
439 		 * We want a new commit: OK, mark the request and wakup the
440 		 * commit thread.  We do _not_ do the commit ourselves.
441 		 */
442 
443 		journal->j_commit_request = target;
444 		jbd_debug(1, "JBD: requesting commit %d/%d\n",
445 			  journal->j_commit_request,
446 			  journal->j_commit_sequence);
447 		wake_up(&journal->j_wait_commit);
448 		return 1;
449 	}
450 	return 0;
451 }
452 
453 int jbd2_log_start_commit(journal_t *journal, tid_t tid)
454 {
455 	int ret;
456 
457 	spin_lock(&journal->j_state_lock);
458 	ret = __jbd2_log_start_commit(journal, tid);
459 	spin_unlock(&journal->j_state_lock);
460 	return ret;
461 }
462 
463 /*
464  * Force and wait upon a commit if the calling process is not within
465  * transaction.  This is used for forcing out undo-protected data which contains
466  * bitmaps, when the fs is running out of space.
467  *
468  * We can only force the running transaction if we don't have an active handle;
469  * otherwise, we will deadlock.
470  *
471  * Returns true if a transaction was started.
472  */
473 int jbd2_journal_force_commit_nested(journal_t *journal)
474 {
475 	transaction_t *transaction = NULL;
476 	tid_t tid;
477 
478 	spin_lock(&journal->j_state_lock);
479 	if (journal->j_running_transaction && !current->journal_info) {
480 		transaction = journal->j_running_transaction;
481 		__jbd2_log_start_commit(journal, transaction->t_tid);
482 	} else if (journal->j_committing_transaction)
483 		transaction = journal->j_committing_transaction;
484 
485 	if (!transaction) {
486 		spin_unlock(&journal->j_state_lock);
487 		return 0;	/* Nothing to retry */
488 	}
489 
490 	tid = transaction->t_tid;
491 	spin_unlock(&journal->j_state_lock);
492 	jbd2_log_wait_commit(journal, tid);
493 	return 1;
494 }
495 
496 /*
497  * Start a commit of the current running transaction (if any).  Returns true
498  * if a transaction was started, and fills its tid in at *ptid
499  */
500 int jbd2_journal_start_commit(journal_t *journal, tid_t *ptid)
501 {
502 	int ret = 0;
503 
504 	spin_lock(&journal->j_state_lock);
505 	if (journal->j_running_transaction) {
506 		tid_t tid = journal->j_running_transaction->t_tid;
507 
508 		ret = __jbd2_log_start_commit(journal, tid);
509 		if (ret && ptid)
510 			*ptid = tid;
511 	} else if (journal->j_committing_transaction && ptid) {
512 		/*
513 		 * If ext3_write_super() recently started a commit, then we
514 		 * have to wait for completion of that transaction
515 		 */
516 		*ptid = journal->j_committing_transaction->t_tid;
517 		ret = 1;
518 	}
519 	spin_unlock(&journal->j_state_lock);
520 	return ret;
521 }
522 
523 /*
524  * Wait for a specified commit to complete.
525  * The caller may not hold the journal lock.
526  */
527 int jbd2_log_wait_commit(journal_t *journal, tid_t tid)
528 {
529 	int err = 0;
530 
531 #ifdef CONFIG_JBD_DEBUG
532 	spin_lock(&journal->j_state_lock);
533 	if (!tid_geq(journal->j_commit_request, tid)) {
534 		printk(KERN_EMERG
535 		       "%s: error: j_commit_request=%d, tid=%d\n",
536 		       __FUNCTION__, journal->j_commit_request, tid);
537 	}
538 	spin_unlock(&journal->j_state_lock);
539 #endif
540 	spin_lock(&journal->j_state_lock);
541 	while (tid_gt(tid, journal->j_commit_sequence)) {
542 		jbd_debug(1, "JBD: want %d, j_commit_sequence=%d\n",
543 				  tid, journal->j_commit_sequence);
544 		wake_up(&journal->j_wait_commit);
545 		spin_unlock(&journal->j_state_lock);
546 		wait_event(journal->j_wait_done_commit,
547 				!tid_gt(tid, journal->j_commit_sequence));
548 		spin_lock(&journal->j_state_lock);
549 	}
550 	spin_unlock(&journal->j_state_lock);
551 
552 	if (unlikely(is_journal_aborted(journal))) {
553 		printk(KERN_EMERG "journal commit I/O error\n");
554 		err = -EIO;
555 	}
556 	return err;
557 }
558 
559 /*
560  * Log buffer allocation routines:
561  */
562 
563 int jbd2_journal_next_log_block(journal_t *journal, unsigned long long *retp)
564 {
565 	unsigned long blocknr;
566 
567 	spin_lock(&journal->j_state_lock);
568 	J_ASSERT(journal->j_free > 1);
569 
570 	blocknr = journal->j_head;
571 	journal->j_head++;
572 	journal->j_free--;
573 	if (journal->j_head == journal->j_last)
574 		journal->j_head = journal->j_first;
575 	spin_unlock(&journal->j_state_lock);
576 	return jbd2_journal_bmap(journal, blocknr, retp);
577 }
578 
579 /*
580  * Conversion of logical to physical block numbers for the journal
581  *
582  * On external journals the journal blocks are identity-mapped, so
583  * this is a no-op.  If needed, we can use j_blk_offset - everything is
584  * ready.
585  */
586 int jbd2_journal_bmap(journal_t *journal, unsigned long blocknr,
587 		 unsigned long long *retp)
588 {
589 	int err = 0;
590 	unsigned long long ret;
591 
592 	if (journal->j_inode) {
593 		ret = bmap(journal->j_inode, blocknr);
594 		if (ret)
595 			*retp = ret;
596 		else {
597 			char b[BDEVNAME_SIZE];
598 
599 			printk(KERN_ALERT "%s: journal block not found "
600 					"at offset %lu on %s\n",
601 				__FUNCTION__,
602 				blocknr,
603 				bdevname(journal->j_dev, b));
604 			err = -EIO;
605 			__journal_abort_soft(journal, err);
606 		}
607 	} else {
608 		*retp = blocknr; /* +journal->j_blk_offset */
609 	}
610 	return err;
611 }
612 
613 /*
614  * We play buffer_head aliasing tricks to write data/metadata blocks to
615  * the journal without copying their contents, but for journal
616  * descriptor blocks we do need to generate bona fide buffers.
617  *
618  * After the caller of jbd2_journal_get_descriptor_buffer() has finished modifying
619  * the buffer's contents they really should run flush_dcache_page(bh->b_page).
620  * But we don't bother doing that, so there will be coherency problems with
621  * mmaps of blockdevs which hold live JBD-controlled filesystems.
622  */
623 struct journal_head *jbd2_journal_get_descriptor_buffer(journal_t *journal)
624 {
625 	struct buffer_head *bh;
626 	unsigned long long blocknr;
627 	int err;
628 
629 	err = jbd2_journal_next_log_block(journal, &blocknr);
630 
631 	if (err)
632 		return NULL;
633 
634 	bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
635 	lock_buffer(bh);
636 	memset(bh->b_data, 0, journal->j_blocksize);
637 	set_buffer_uptodate(bh);
638 	unlock_buffer(bh);
639 	BUFFER_TRACE(bh, "return this buffer");
640 	return jbd2_journal_add_journal_head(bh);
641 }
642 
643 /*
644  * Management for journal control blocks: functions to create and
645  * destroy journal_t structures, and to initialise and read existing
646  * journal blocks from disk.  */
647 
648 /* First: create and setup a journal_t object in memory.  We initialise
649  * very few fields yet: that has to wait until we have created the
650  * journal structures from from scratch, or loaded them from disk. */
651 
652 static journal_t * journal_init_common (void)
653 {
654 	journal_t *journal;
655 	int err;
656 
657 	journal = jbd_kmalloc(sizeof(*journal), GFP_KERNEL);
658 	if (!journal)
659 		goto fail;
660 	memset(journal, 0, sizeof(*journal));
661 
662 	init_waitqueue_head(&journal->j_wait_transaction_locked);
663 	init_waitqueue_head(&journal->j_wait_logspace);
664 	init_waitqueue_head(&journal->j_wait_done_commit);
665 	init_waitqueue_head(&journal->j_wait_checkpoint);
666 	init_waitqueue_head(&journal->j_wait_commit);
667 	init_waitqueue_head(&journal->j_wait_updates);
668 	mutex_init(&journal->j_barrier);
669 	mutex_init(&journal->j_checkpoint_mutex);
670 	spin_lock_init(&journal->j_revoke_lock);
671 	spin_lock_init(&journal->j_list_lock);
672 	spin_lock_init(&journal->j_state_lock);
673 
674 	journal->j_commit_interval = (HZ * JBD_DEFAULT_MAX_COMMIT_AGE);
675 
676 	/* The journal is marked for error until we succeed with recovery! */
677 	journal->j_flags = JBD2_ABORT;
678 
679 	/* Set up a default-sized revoke table for the new mount. */
680 	err = jbd2_journal_init_revoke(journal, JOURNAL_REVOKE_DEFAULT_HASH);
681 	if (err) {
682 		kfree(journal);
683 		goto fail;
684 	}
685 	return journal;
686 fail:
687 	return NULL;
688 }
689 
690 /* jbd2_journal_init_dev and jbd2_journal_init_inode:
691  *
692  * Create a journal structure assigned some fixed set of disk blocks to
693  * the journal.  We don't actually touch those disk blocks yet, but we
694  * need to set up all of the mapping information to tell the journaling
695  * system where the journal blocks are.
696  *
697  */
698 
699 /**
700  *  journal_t * jbd2_journal_init_dev() - creates an initialises a journal structure
701  *  @bdev: Block device on which to create the journal
702  *  @fs_dev: Device which hold journalled filesystem for this journal.
703  *  @start: Block nr Start of journal.
704  *  @len:  Length of the journal in blocks.
705  *  @blocksize: blocksize of journalling device
706  *  @returns: a newly created journal_t *
707  *
708  *  jbd2_journal_init_dev creates a journal which maps a fixed contiguous
709  *  range of blocks on an arbitrary block device.
710  *
711  */
712 journal_t * jbd2_journal_init_dev(struct block_device *bdev,
713 			struct block_device *fs_dev,
714 			unsigned long long start, int len, int blocksize)
715 {
716 	journal_t *journal = journal_init_common();
717 	struct buffer_head *bh;
718 	int n;
719 
720 	if (!journal)
721 		return NULL;
722 
723 	/* journal descriptor can store up to n blocks -bzzz */
724 	journal->j_blocksize = blocksize;
725 	n = journal->j_blocksize / sizeof(journal_block_tag_t);
726 	journal->j_wbufsize = n;
727 	journal->j_wbuf = kmalloc(n * sizeof(struct buffer_head*), GFP_KERNEL);
728 	if (!journal->j_wbuf) {
729 		printk(KERN_ERR "%s: Cant allocate bhs for commit thread\n",
730 			__FUNCTION__);
731 		kfree(journal);
732 		journal = NULL;
733 		goto out;
734 	}
735 	journal->j_dev = bdev;
736 	journal->j_fs_dev = fs_dev;
737 	journal->j_blk_offset = start;
738 	journal->j_maxlen = len;
739 
740 	bh = __getblk(journal->j_dev, start, journal->j_blocksize);
741 	J_ASSERT(bh != NULL);
742 	journal->j_sb_buffer = bh;
743 	journal->j_superblock = (journal_superblock_t *)bh->b_data;
744 out:
745 	return journal;
746 }
747 
748 /**
749  *  journal_t * jbd2_journal_init_inode () - creates a journal which maps to a inode.
750  *  @inode: An inode to create the journal in
751  *
752  * jbd2_journal_init_inode creates a journal which maps an on-disk inode as
753  * the journal.  The inode must exist already, must support bmap() and
754  * must have all data blocks preallocated.
755  */
756 journal_t * jbd2_journal_init_inode (struct inode *inode)
757 {
758 	struct buffer_head *bh;
759 	journal_t *journal = journal_init_common();
760 	int err;
761 	int n;
762 	unsigned long long blocknr;
763 
764 	if (!journal)
765 		return NULL;
766 
767 	journal->j_dev = journal->j_fs_dev = inode->i_sb->s_bdev;
768 	journal->j_inode = inode;
769 	jbd_debug(1,
770 		  "journal %p: inode %s/%ld, size %Ld, bits %d, blksize %ld\n",
771 		  journal, inode->i_sb->s_id, inode->i_ino,
772 		  (long long) inode->i_size,
773 		  inode->i_sb->s_blocksize_bits, inode->i_sb->s_blocksize);
774 
775 	journal->j_maxlen = inode->i_size >> inode->i_sb->s_blocksize_bits;
776 	journal->j_blocksize = inode->i_sb->s_blocksize;
777 
778 	/* journal descriptor can store up to n blocks -bzzz */
779 	n = journal->j_blocksize / sizeof(journal_block_tag_t);
780 	journal->j_wbufsize = n;
781 	journal->j_wbuf = kmalloc(n * sizeof(struct buffer_head*), GFP_KERNEL);
782 	if (!journal->j_wbuf) {
783 		printk(KERN_ERR "%s: Cant allocate bhs for commit thread\n",
784 			__FUNCTION__);
785 		kfree(journal);
786 		return NULL;
787 	}
788 
789 	err = jbd2_journal_bmap(journal, 0, &blocknr);
790 	/* If that failed, give up */
791 	if (err) {
792 		printk(KERN_ERR "%s: Cannnot locate journal superblock\n",
793 		       __FUNCTION__);
794 		kfree(journal);
795 		return NULL;
796 	}
797 
798 	bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
799 	J_ASSERT(bh != NULL);
800 	journal->j_sb_buffer = bh;
801 	journal->j_superblock = (journal_superblock_t *)bh->b_data;
802 
803 	return journal;
804 }
805 
806 /*
807  * If the journal init or create aborts, we need to mark the journal
808  * superblock as being NULL to prevent the journal destroy from writing
809  * back a bogus superblock.
810  */
811 static void journal_fail_superblock (journal_t *journal)
812 {
813 	struct buffer_head *bh = journal->j_sb_buffer;
814 	brelse(bh);
815 	journal->j_sb_buffer = NULL;
816 }
817 
818 /*
819  * Given a journal_t structure, initialise the various fields for
820  * startup of a new journaling session.  We use this both when creating
821  * a journal, and after recovering an old journal to reset it for
822  * subsequent use.
823  */
824 
825 static int journal_reset(journal_t *journal)
826 {
827 	journal_superblock_t *sb = journal->j_superblock;
828 	unsigned long long first, last;
829 
830 	first = be32_to_cpu(sb->s_first);
831 	last = be32_to_cpu(sb->s_maxlen);
832 
833 	journal->j_first = first;
834 	journal->j_last = last;
835 
836 	journal->j_head = first;
837 	journal->j_tail = first;
838 	journal->j_free = last - first;
839 
840 	journal->j_tail_sequence = journal->j_transaction_sequence;
841 	journal->j_commit_sequence = journal->j_transaction_sequence - 1;
842 	journal->j_commit_request = journal->j_commit_sequence;
843 
844 	journal->j_max_transaction_buffers = journal->j_maxlen / 4;
845 
846 	/* Add the dynamic fields and write it to disk. */
847 	jbd2_journal_update_superblock(journal, 1);
848 	return jbd2_journal_start_thread(journal);
849 }
850 
851 /**
852  * int jbd2_journal_create() - Initialise the new journal file
853  * @journal: Journal to create. This structure must have been initialised
854  *
855  * Given a journal_t structure which tells us which disk blocks we can
856  * use, create a new journal superblock and initialise all of the
857  * journal fields from scratch.
858  **/
859 int jbd2_journal_create(journal_t *journal)
860 {
861 	unsigned long long blocknr;
862 	struct buffer_head *bh;
863 	journal_superblock_t *sb;
864 	int i, err;
865 
866 	if (journal->j_maxlen < JBD2_MIN_JOURNAL_BLOCKS) {
867 		printk (KERN_ERR "Journal length (%d blocks) too short.\n",
868 			journal->j_maxlen);
869 		journal_fail_superblock(journal);
870 		return -EINVAL;
871 	}
872 
873 	if (journal->j_inode == NULL) {
874 		/*
875 		 * We don't know what block to start at!
876 		 */
877 		printk(KERN_EMERG
878 		       "%s: creation of journal on external device!\n",
879 		       __FUNCTION__);
880 		BUG();
881 	}
882 
883 	/* Zero out the entire journal on disk.  We cannot afford to
884 	   have any blocks on disk beginning with JBD2_MAGIC_NUMBER. */
885 	jbd_debug(1, "JBD: Zeroing out journal blocks...\n");
886 	for (i = 0; i < journal->j_maxlen; i++) {
887 		err = jbd2_journal_bmap(journal, i, &blocknr);
888 		if (err)
889 			return err;
890 		bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
891 		lock_buffer(bh);
892 		memset (bh->b_data, 0, journal->j_blocksize);
893 		BUFFER_TRACE(bh, "marking dirty");
894 		mark_buffer_dirty(bh);
895 		BUFFER_TRACE(bh, "marking uptodate");
896 		set_buffer_uptodate(bh);
897 		unlock_buffer(bh);
898 		__brelse(bh);
899 	}
900 
901 	sync_blockdev(journal->j_dev);
902 	jbd_debug(1, "JBD: journal cleared.\n");
903 
904 	/* OK, fill in the initial static fields in the new superblock */
905 	sb = journal->j_superblock;
906 
907 	sb->s_header.h_magic	 = cpu_to_be32(JBD2_MAGIC_NUMBER);
908 	sb->s_header.h_blocktype = cpu_to_be32(JBD2_SUPERBLOCK_V2);
909 
910 	sb->s_blocksize	= cpu_to_be32(journal->j_blocksize);
911 	sb->s_maxlen	= cpu_to_be32(journal->j_maxlen);
912 	sb->s_first	= cpu_to_be32(1);
913 
914 	journal->j_transaction_sequence = 1;
915 
916 	journal->j_flags &= ~JBD2_ABORT;
917 	journal->j_format_version = 2;
918 
919 	return journal_reset(journal);
920 }
921 
922 /**
923  * void jbd2_journal_update_superblock() - Update journal sb on disk.
924  * @journal: The journal to update.
925  * @wait: Set to '0' if you don't want to wait for IO completion.
926  *
927  * Update a journal's dynamic superblock fields and write it to disk,
928  * optionally waiting for the IO to complete.
929  */
930 void jbd2_journal_update_superblock(journal_t *journal, int wait)
931 {
932 	journal_superblock_t *sb = journal->j_superblock;
933 	struct buffer_head *bh = journal->j_sb_buffer;
934 
935 	/*
936 	 * As a special case, if the on-disk copy is already marked as needing
937 	 * no recovery (s_start == 0) and there are no outstanding transactions
938 	 * in the filesystem, then we can safely defer the superblock update
939 	 * until the next commit by setting JBD2_FLUSHED.  This avoids
940 	 * attempting a write to a potential-readonly device.
941 	 */
942 	if (sb->s_start == 0 && journal->j_tail_sequence ==
943 				journal->j_transaction_sequence) {
944 		jbd_debug(1,"JBD: Skipping superblock update on recovered sb "
945 			"(start %ld, seq %d, errno %d)\n",
946 			journal->j_tail, journal->j_tail_sequence,
947 			journal->j_errno);
948 		goto out;
949 	}
950 
951 	spin_lock(&journal->j_state_lock);
952 	jbd_debug(1,"JBD: updating superblock (start %ld, seq %d, errno %d)\n",
953 		  journal->j_tail, journal->j_tail_sequence, journal->j_errno);
954 
955 	sb->s_sequence = cpu_to_be32(journal->j_tail_sequence);
956 	sb->s_start    = cpu_to_be32(journal->j_tail);
957 	sb->s_errno    = cpu_to_be32(journal->j_errno);
958 	spin_unlock(&journal->j_state_lock);
959 
960 	BUFFER_TRACE(bh, "marking dirty");
961 	mark_buffer_dirty(bh);
962 	if (wait)
963 		sync_dirty_buffer(bh);
964 	else
965 		ll_rw_block(SWRITE, 1, &bh);
966 
967 out:
968 	/* If we have just flushed the log (by marking s_start==0), then
969 	 * any future commit will have to be careful to update the
970 	 * superblock again to re-record the true start of the log. */
971 
972 	spin_lock(&journal->j_state_lock);
973 	if (sb->s_start)
974 		journal->j_flags &= ~JBD2_FLUSHED;
975 	else
976 		journal->j_flags |= JBD2_FLUSHED;
977 	spin_unlock(&journal->j_state_lock);
978 }
979 
980 /*
981  * Read the superblock for a given journal, performing initial
982  * validation of the format.
983  */
984 
985 static int journal_get_superblock(journal_t *journal)
986 {
987 	struct buffer_head *bh;
988 	journal_superblock_t *sb;
989 	int err = -EIO;
990 
991 	bh = journal->j_sb_buffer;
992 
993 	J_ASSERT(bh != NULL);
994 	if (!buffer_uptodate(bh)) {
995 		ll_rw_block(READ, 1, &bh);
996 		wait_on_buffer(bh);
997 		if (!buffer_uptodate(bh)) {
998 			printk (KERN_ERR
999 				"JBD: IO error reading journal superblock\n");
1000 			goto out;
1001 		}
1002 	}
1003 
1004 	sb = journal->j_superblock;
1005 
1006 	err = -EINVAL;
1007 
1008 	if (sb->s_header.h_magic != cpu_to_be32(JBD2_MAGIC_NUMBER) ||
1009 	    sb->s_blocksize != cpu_to_be32(journal->j_blocksize)) {
1010 		printk(KERN_WARNING "JBD: no valid journal superblock found\n");
1011 		goto out;
1012 	}
1013 
1014 	switch(be32_to_cpu(sb->s_header.h_blocktype)) {
1015 	case JBD2_SUPERBLOCK_V1:
1016 		journal->j_format_version = 1;
1017 		break;
1018 	case JBD2_SUPERBLOCK_V2:
1019 		journal->j_format_version = 2;
1020 		break;
1021 	default:
1022 		printk(KERN_WARNING "JBD: unrecognised superblock format ID\n");
1023 		goto out;
1024 	}
1025 
1026 	if (be32_to_cpu(sb->s_maxlen) < journal->j_maxlen)
1027 		journal->j_maxlen = be32_to_cpu(sb->s_maxlen);
1028 	else if (be32_to_cpu(sb->s_maxlen) > journal->j_maxlen) {
1029 		printk (KERN_WARNING "JBD: journal file too short\n");
1030 		goto out;
1031 	}
1032 
1033 	return 0;
1034 
1035 out:
1036 	journal_fail_superblock(journal);
1037 	return err;
1038 }
1039 
1040 /*
1041  * Load the on-disk journal superblock and read the key fields into the
1042  * journal_t.
1043  */
1044 
1045 static int load_superblock(journal_t *journal)
1046 {
1047 	int err;
1048 	journal_superblock_t *sb;
1049 
1050 	err = journal_get_superblock(journal);
1051 	if (err)
1052 		return err;
1053 
1054 	sb = journal->j_superblock;
1055 
1056 	journal->j_tail_sequence = be32_to_cpu(sb->s_sequence);
1057 	journal->j_tail = be32_to_cpu(sb->s_start);
1058 	journal->j_first = be32_to_cpu(sb->s_first);
1059 	journal->j_last = be32_to_cpu(sb->s_maxlen);
1060 	journal->j_errno = be32_to_cpu(sb->s_errno);
1061 
1062 	return 0;
1063 }
1064 
1065 
1066 /**
1067  * int jbd2_journal_load() - Read journal from disk.
1068  * @journal: Journal to act on.
1069  *
1070  * Given a journal_t structure which tells us which disk blocks contain
1071  * a journal, read the journal from disk to initialise the in-memory
1072  * structures.
1073  */
1074 int jbd2_journal_load(journal_t *journal)
1075 {
1076 	int err;
1077 	journal_superblock_t *sb;
1078 
1079 	err = load_superblock(journal);
1080 	if (err)
1081 		return err;
1082 
1083 	sb = journal->j_superblock;
1084 	/* If this is a V2 superblock, then we have to check the
1085 	 * features flags on it. */
1086 
1087 	if (journal->j_format_version >= 2) {
1088 		if ((sb->s_feature_ro_compat &
1089 		     ~cpu_to_be32(JBD2_KNOWN_ROCOMPAT_FEATURES)) ||
1090 		    (sb->s_feature_incompat &
1091 		     ~cpu_to_be32(JBD2_KNOWN_INCOMPAT_FEATURES))) {
1092 			printk (KERN_WARNING
1093 				"JBD: Unrecognised features on journal\n");
1094 			return -EINVAL;
1095 		}
1096 	}
1097 
1098 	/*
1099 	 * Create a slab for this blocksize
1100 	 */
1101 	err = jbd2_journal_create_jbd_slab(be32_to_cpu(sb->s_blocksize));
1102 	if (err)
1103 		return err;
1104 
1105 	/* Let the recovery code check whether it needs to recover any
1106 	 * data from the journal. */
1107 	if (jbd2_journal_recover(journal))
1108 		goto recovery_error;
1109 
1110 	/* OK, we've finished with the dynamic journal bits:
1111 	 * reinitialise the dynamic contents of the superblock in memory
1112 	 * and reset them on disk. */
1113 	if (journal_reset(journal))
1114 		goto recovery_error;
1115 
1116 	journal->j_flags &= ~JBD2_ABORT;
1117 	journal->j_flags |= JBD2_LOADED;
1118 	return 0;
1119 
1120 recovery_error:
1121 	printk (KERN_WARNING "JBD: recovery failed\n");
1122 	return -EIO;
1123 }
1124 
1125 /**
1126  * void jbd2_journal_destroy() - Release a journal_t structure.
1127  * @journal: Journal to act on.
1128  *
1129  * Release a journal_t structure once it is no longer in use by the
1130  * journaled object.
1131  */
1132 void jbd2_journal_destroy(journal_t *journal)
1133 {
1134 	/* Wait for the commit thread to wake up and die. */
1135 	journal_kill_thread(journal);
1136 
1137 	/* Force a final log commit */
1138 	if (journal->j_running_transaction)
1139 		jbd2_journal_commit_transaction(journal);
1140 
1141 	/* Force any old transactions to disk */
1142 
1143 	/* Totally anal locking here... */
1144 	spin_lock(&journal->j_list_lock);
1145 	while (journal->j_checkpoint_transactions != NULL) {
1146 		spin_unlock(&journal->j_list_lock);
1147 		jbd2_log_do_checkpoint(journal);
1148 		spin_lock(&journal->j_list_lock);
1149 	}
1150 
1151 	J_ASSERT(journal->j_running_transaction == NULL);
1152 	J_ASSERT(journal->j_committing_transaction == NULL);
1153 	J_ASSERT(journal->j_checkpoint_transactions == NULL);
1154 	spin_unlock(&journal->j_list_lock);
1155 
1156 	/* We can now mark the journal as empty. */
1157 	journal->j_tail = 0;
1158 	journal->j_tail_sequence = ++journal->j_transaction_sequence;
1159 	if (journal->j_sb_buffer) {
1160 		jbd2_journal_update_superblock(journal, 1);
1161 		brelse(journal->j_sb_buffer);
1162 	}
1163 
1164 	if (journal->j_inode)
1165 		iput(journal->j_inode);
1166 	if (journal->j_revoke)
1167 		jbd2_journal_destroy_revoke(journal);
1168 	kfree(journal->j_wbuf);
1169 	kfree(journal);
1170 }
1171 
1172 
1173 /**
1174  *int jbd2_journal_check_used_features () - Check if features specified are used.
1175  * @journal: Journal to check.
1176  * @compat: bitmask of compatible features
1177  * @ro: bitmask of features that force read-only mount
1178  * @incompat: bitmask of incompatible features
1179  *
1180  * Check whether the journal uses all of a given set of
1181  * features.  Return true (non-zero) if it does.
1182  **/
1183 
1184 int jbd2_journal_check_used_features (journal_t *journal, unsigned long compat,
1185 				 unsigned long ro, unsigned long incompat)
1186 {
1187 	journal_superblock_t *sb;
1188 
1189 	if (!compat && !ro && !incompat)
1190 		return 1;
1191 	if (journal->j_format_version == 1)
1192 		return 0;
1193 
1194 	sb = journal->j_superblock;
1195 
1196 	if (((be32_to_cpu(sb->s_feature_compat) & compat) == compat) &&
1197 	    ((be32_to_cpu(sb->s_feature_ro_compat) & ro) == ro) &&
1198 	    ((be32_to_cpu(sb->s_feature_incompat) & incompat) == incompat))
1199 		return 1;
1200 
1201 	return 0;
1202 }
1203 
1204 /**
1205  * int jbd2_journal_check_available_features() - Check feature set in journalling layer
1206  * @journal: Journal to check.
1207  * @compat: bitmask of compatible features
1208  * @ro: bitmask of features that force read-only mount
1209  * @incompat: bitmask of incompatible features
1210  *
1211  * Check whether the journaling code supports the use of
1212  * all of a given set of features on this journal.  Return true
1213  * (non-zero) if it can. */
1214 
1215 int jbd2_journal_check_available_features (journal_t *journal, unsigned long compat,
1216 				      unsigned long ro, unsigned long incompat)
1217 {
1218 	journal_superblock_t *sb;
1219 
1220 	if (!compat && !ro && !incompat)
1221 		return 1;
1222 
1223 	sb = journal->j_superblock;
1224 
1225 	/* We can support any known requested features iff the
1226 	 * superblock is in version 2.  Otherwise we fail to support any
1227 	 * extended sb features. */
1228 
1229 	if (journal->j_format_version != 2)
1230 		return 0;
1231 
1232 	if ((compat   & JBD2_KNOWN_COMPAT_FEATURES) == compat &&
1233 	    (ro       & JBD2_KNOWN_ROCOMPAT_FEATURES) == ro &&
1234 	    (incompat & JBD2_KNOWN_INCOMPAT_FEATURES) == incompat)
1235 		return 1;
1236 
1237 	return 0;
1238 }
1239 
1240 /**
1241  * int jbd2_journal_set_features () - Mark a given journal feature in the superblock
1242  * @journal: Journal to act on.
1243  * @compat: bitmask of compatible features
1244  * @ro: bitmask of features that force read-only mount
1245  * @incompat: bitmask of incompatible features
1246  *
1247  * Mark a given journal feature as present on the
1248  * superblock.  Returns true if the requested features could be set.
1249  *
1250  */
1251 
1252 int jbd2_journal_set_features (journal_t *journal, unsigned long compat,
1253 			  unsigned long ro, unsigned long incompat)
1254 {
1255 	journal_superblock_t *sb;
1256 
1257 	if (jbd2_journal_check_used_features(journal, compat, ro, incompat))
1258 		return 1;
1259 
1260 	if (!jbd2_journal_check_available_features(journal, compat, ro, incompat))
1261 		return 0;
1262 
1263 	jbd_debug(1, "Setting new features 0x%lx/0x%lx/0x%lx\n",
1264 		  compat, ro, incompat);
1265 
1266 	sb = journal->j_superblock;
1267 
1268 	sb->s_feature_compat    |= cpu_to_be32(compat);
1269 	sb->s_feature_ro_compat |= cpu_to_be32(ro);
1270 	sb->s_feature_incompat  |= cpu_to_be32(incompat);
1271 
1272 	return 1;
1273 }
1274 
1275 
1276 /**
1277  * int jbd2_journal_update_format () - Update on-disk journal structure.
1278  * @journal: Journal to act on.
1279  *
1280  * Given an initialised but unloaded journal struct, poke about in the
1281  * on-disk structure to update it to the most recent supported version.
1282  */
1283 int jbd2_journal_update_format (journal_t *journal)
1284 {
1285 	journal_superblock_t *sb;
1286 	int err;
1287 
1288 	err = journal_get_superblock(journal);
1289 	if (err)
1290 		return err;
1291 
1292 	sb = journal->j_superblock;
1293 
1294 	switch (be32_to_cpu(sb->s_header.h_blocktype)) {
1295 	case JBD2_SUPERBLOCK_V2:
1296 		return 0;
1297 	case JBD2_SUPERBLOCK_V1:
1298 		return journal_convert_superblock_v1(journal, sb);
1299 	default:
1300 		break;
1301 	}
1302 	return -EINVAL;
1303 }
1304 
1305 static int journal_convert_superblock_v1(journal_t *journal,
1306 					 journal_superblock_t *sb)
1307 {
1308 	int offset, blocksize;
1309 	struct buffer_head *bh;
1310 
1311 	printk(KERN_WARNING
1312 		"JBD: Converting superblock from version 1 to 2.\n");
1313 
1314 	/* Pre-initialise new fields to zero */
1315 	offset = ((char *) &(sb->s_feature_compat)) - ((char *) sb);
1316 	blocksize = be32_to_cpu(sb->s_blocksize);
1317 	memset(&sb->s_feature_compat, 0, blocksize-offset);
1318 
1319 	sb->s_nr_users = cpu_to_be32(1);
1320 	sb->s_header.h_blocktype = cpu_to_be32(JBD2_SUPERBLOCK_V2);
1321 	journal->j_format_version = 2;
1322 
1323 	bh = journal->j_sb_buffer;
1324 	BUFFER_TRACE(bh, "marking dirty");
1325 	mark_buffer_dirty(bh);
1326 	sync_dirty_buffer(bh);
1327 	return 0;
1328 }
1329 
1330 
1331 /**
1332  * int jbd2_journal_flush () - Flush journal
1333  * @journal: Journal to act on.
1334  *
1335  * Flush all data for a given journal to disk and empty the journal.
1336  * Filesystems can use this when remounting readonly to ensure that
1337  * recovery does not need to happen on remount.
1338  */
1339 
1340 int jbd2_journal_flush(journal_t *journal)
1341 {
1342 	int err = 0;
1343 	transaction_t *transaction = NULL;
1344 	unsigned long old_tail;
1345 
1346 	spin_lock(&journal->j_state_lock);
1347 
1348 	/* Force everything buffered to the log... */
1349 	if (journal->j_running_transaction) {
1350 		transaction = journal->j_running_transaction;
1351 		__jbd2_log_start_commit(journal, transaction->t_tid);
1352 	} else if (journal->j_committing_transaction)
1353 		transaction = journal->j_committing_transaction;
1354 
1355 	/* Wait for the log commit to complete... */
1356 	if (transaction) {
1357 		tid_t tid = transaction->t_tid;
1358 
1359 		spin_unlock(&journal->j_state_lock);
1360 		jbd2_log_wait_commit(journal, tid);
1361 	} else {
1362 		spin_unlock(&journal->j_state_lock);
1363 	}
1364 
1365 	/* ...and flush everything in the log out to disk. */
1366 	spin_lock(&journal->j_list_lock);
1367 	while (!err && journal->j_checkpoint_transactions != NULL) {
1368 		spin_unlock(&journal->j_list_lock);
1369 		err = jbd2_log_do_checkpoint(journal);
1370 		spin_lock(&journal->j_list_lock);
1371 	}
1372 	spin_unlock(&journal->j_list_lock);
1373 	jbd2_cleanup_journal_tail(journal);
1374 
1375 	/* Finally, mark the journal as really needing no recovery.
1376 	 * This sets s_start==0 in the underlying superblock, which is
1377 	 * the magic code for a fully-recovered superblock.  Any future
1378 	 * commits of data to the journal will restore the current
1379 	 * s_start value. */
1380 	spin_lock(&journal->j_state_lock);
1381 	old_tail = journal->j_tail;
1382 	journal->j_tail = 0;
1383 	spin_unlock(&journal->j_state_lock);
1384 	jbd2_journal_update_superblock(journal, 1);
1385 	spin_lock(&journal->j_state_lock);
1386 	journal->j_tail = old_tail;
1387 
1388 	J_ASSERT(!journal->j_running_transaction);
1389 	J_ASSERT(!journal->j_committing_transaction);
1390 	J_ASSERT(!journal->j_checkpoint_transactions);
1391 	J_ASSERT(journal->j_head == journal->j_tail);
1392 	J_ASSERT(journal->j_tail_sequence == journal->j_transaction_sequence);
1393 	spin_unlock(&journal->j_state_lock);
1394 	return err;
1395 }
1396 
1397 /**
1398  * int jbd2_journal_wipe() - Wipe journal contents
1399  * @journal: Journal to act on.
1400  * @write: flag (see below)
1401  *
1402  * Wipe out all of the contents of a journal, safely.  This will produce
1403  * a warning if the journal contains any valid recovery information.
1404  * Must be called between journal_init_*() and jbd2_journal_load().
1405  *
1406  * If 'write' is non-zero, then we wipe out the journal on disk; otherwise
1407  * we merely suppress recovery.
1408  */
1409 
1410 int jbd2_journal_wipe(journal_t *journal, int write)
1411 {
1412 	journal_superblock_t *sb;
1413 	int err = 0;
1414 
1415 	J_ASSERT (!(journal->j_flags & JBD2_LOADED));
1416 
1417 	err = load_superblock(journal);
1418 	if (err)
1419 		return err;
1420 
1421 	sb = journal->j_superblock;
1422 
1423 	if (!journal->j_tail)
1424 		goto no_recovery;
1425 
1426 	printk (KERN_WARNING "JBD: %s recovery information on journal\n",
1427 		write ? "Clearing" : "Ignoring");
1428 
1429 	err = jbd2_journal_skip_recovery(journal);
1430 	if (write)
1431 		jbd2_journal_update_superblock(journal, 1);
1432 
1433  no_recovery:
1434 	return err;
1435 }
1436 
1437 /*
1438  * journal_dev_name: format a character string to describe on what
1439  * device this journal is present.
1440  */
1441 
1442 static const char *journal_dev_name(journal_t *journal, char *buffer)
1443 {
1444 	struct block_device *bdev;
1445 
1446 	if (journal->j_inode)
1447 		bdev = journal->j_inode->i_sb->s_bdev;
1448 	else
1449 		bdev = journal->j_dev;
1450 
1451 	return bdevname(bdev, buffer);
1452 }
1453 
1454 /*
1455  * Journal abort has very specific semantics, which we describe
1456  * for journal abort.
1457  *
1458  * Two internal function, which provide abort to te jbd layer
1459  * itself are here.
1460  */
1461 
1462 /*
1463  * Quick version for internal journal use (doesn't lock the journal).
1464  * Aborts hard --- we mark the abort as occurred, but do _nothing_ else,
1465  * and don't attempt to make any other journal updates.
1466  */
1467 void __jbd2_journal_abort_hard(journal_t *journal)
1468 {
1469 	transaction_t *transaction;
1470 	char b[BDEVNAME_SIZE];
1471 
1472 	if (journal->j_flags & JBD2_ABORT)
1473 		return;
1474 
1475 	printk(KERN_ERR "Aborting journal on device %s.\n",
1476 		journal_dev_name(journal, b));
1477 
1478 	spin_lock(&journal->j_state_lock);
1479 	journal->j_flags |= JBD2_ABORT;
1480 	transaction = journal->j_running_transaction;
1481 	if (transaction)
1482 		__jbd2_log_start_commit(journal, transaction->t_tid);
1483 	spin_unlock(&journal->j_state_lock);
1484 }
1485 
1486 /* Soft abort: record the abort error status in the journal superblock,
1487  * but don't do any other IO. */
1488 static void __journal_abort_soft (journal_t *journal, int errno)
1489 {
1490 	if (journal->j_flags & JBD2_ABORT)
1491 		return;
1492 
1493 	if (!journal->j_errno)
1494 		journal->j_errno = errno;
1495 
1496 	__jbd2_journal_abort_hard(journal);
1497 
1498 	if (errno)
1499 		jbd2_journal_update_superblock(journal, 1);
1500 }
1501 
1502 /**
1503  * void jbd2_journal_abort () - Shutdown the journal immediately.
1504  * @journal: the journal to shutdown.
1505  * @errno:   an error number to record in the journal indicating
1506  *           the reason for the shutdown.
1507  *
1508  * Perform a complete, immediate shutdown of the ENTIRE
1509  * journal (not of a single transaction).  This operation cannot be
1510  * undone without closing and reopening the journal.
1511  *
1512  * The jbd2_journal_abort function is intended to support higher level error
1513  * recovery mechanisms such as the ext2/ext3 remount-readonly error
1514  * mode.
1515  *
1516  * Journal abort has very specific semantics.  Any existing dirty,
1517  * unjournaled buffers in the main filesystem will still be written to
1518  * disk by bdflush, but the journaling mechanism will be suspended
1519  * immediately and no further transaction commits will be honoured.
1520  *
1521  * Any dirty, journaled buffers will be written back to disk without
1522  * hitting the journal.  Atomicity cannot be guaranteed on an aborted
1523  * filesystem, but we _do_ attempt to leave as much data as possible
1524  * behind for fsck to use for cleanup.
1525  *
1526  * Any attempt to get a new transaction handle on a journal which is in
1527  * ABORT state will just result in an -EROFS error return.  A
1528  * jbd2_journal_stop on an existing handle will return -EIO if we have
1529  * entered abort state during the update.
1530  *
1531  * Recursive transactions are not disturbed by journal abort until the
1532  * final jbd2_journal_stop, which will receive the -EIO error.
1533  *
1534  * Finally, the jbd2_journal_abort call allows the caller to supply an errno
1535  * which will be recorded (if possible) in the journal superblock.  This
1536  * allows a client to record failure conditions in the middle of a
1537  * transaction without having to complete the transaction to record the
1538  * failure to disk.  ext3_error, for example, now uses this
1539  * functionality.
1540  *
1541  * Errors which originate from within the journaling layer will NOT
1542  * supply an errno; a null errno implies that absolutely no further
1543  * writes are done to the journal (unless there are any already in
1544  * progress).
1545  *
1546  */
1547 
1548 void jbd2_journal_abort(journal_t *journal, int errno)
1549 {
1550 	__journal_abort_soft(journal, errno);
1551 }
1552 
1553 /**
1554  * int jbd2_journal_errno () - returns the journal's error state.
1555  * @journal: journal to examine.
1556  *
1557  * This is the errno numbet set with jbd2_journal_abort(), the last
1558  * time the journal was mounted - if the journal was stopped
1559  * without calling abort this will be 0.
1560  *
1561  * If the journal has been aborted on this mount time -EROFS will
1562  * be returned.
1563  */
1564 int jbd2_journal_errno(journal_t *journal)
1565 {
1566 	int err;
1567 
1568 	spin_lock(&journal->j_state_lock);
1569 	if (journal->j_flags & JBD2_ABORT)
1570 		err = -EROFS;
1571 	else
1572 		err = journal->j_errno;
1573 	spin_unlock(&journal->j_state_lock);
1574 	return err;
1575 }
1576 
1577 /**
1578  * int jbd2_journal_clear_err () - clears the journal's error state
1579  * @journal: journal to act on.
1580  *
1581  * An error must be cleared or Acked to take a FS out of readonly
1582  * mode.
1583  */
1584 int jbd2_journal_clear_err(journal_t *journal)
1585 {
1586 	int err = 0;
1587 
1588 	spin_lock(&journal->j_state_lock);
1589 	if (journal->j_flags & JBD2_ABORT)
1590 		err = -EROFS;
1591 	else
1592 		journal->j_errno = 0;
1593 	spin_unlock(&journal->j_state_lock);
1594 	return err;
1595 }
1596 
1597 /**
1598  * void jbd2_journal_ack_err() - Ack journal err.
1599  * @journal: journal to act on.
1600  *
1601  * An error must be cleared or Acked to take a FS out of readonly
1602  * mode.
1603  */
1604 void jbd2_journal_ack_err(journal_t *journal)
1605 {
1606 	spin_lock(&journal->j_state_lock);
1607 	if (journal->j_errno)
1608 		journal->j_flags |= JBD2_ACK_ERR;
1609 	spin_unlock(&journal->j_state_lock);
1610 }
1611 
1612 int jbd2_journal_blocks_per_page(struct inode *inode)
1613 {
1614 	return 1 << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);
1615 }
1616 
1617 /*
1618  * helper functions to deal with 32 or 64bit block numbers.
1619  */
1620 size_t journal_tag_bytes(journal_t *journal)
1621 {
1622 	if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_64BIT))
1623 		return JBD_TAG_SIZE64;
1624 	else
1625 		return JBD_TAG_SIZE32;
1626 }
1627 
1628 /*
1629  * Simple support for retrying memory allocations.  Introduced to help to
1630  * debug different VM deadlock avoidance strategies.
1631  */
1632 void * __jbd2_kmalloc (const char *where, size_t size, gfp_t flags, int retry)
1633 {
1634 	return kmalloc(size, flags | (retry ? __GFP_NOFAIL : 0));
1635 }
1636 
1637 /*
1638  * jbd slab management: create 1k, 2k, 4k, 8k slabs as needed
1639  * and allocate frozen and commit buffers from these slabs.
1640  *
1641  * Reason for doing this is to avoid, SLAB_DEBUG - since it could
1642  * cause bh to cross page boundary.
1643  */
1644 
1645 #define JBD_MAX_SLABS 5
1646 #define JBD_SLAB_INDEX(size)  (size >> 11)
1647 
1648 static struct kmem_cache *jbd_slab[JBD_MAX_SLABS];
1649 static const char *jbd_slab_names[JBD_MAX_SLABS] = {
1650 	"jbd2_1k", "jbd2_2k", "jbd2_4k", NULL, "jbd2_8k"
1651 };
1652 
1653 static void jbd2_journal_destroy_jbd_slabs(void)
1654 {
1655 	int i;
1656 
1657 	for (i = 0; i < JBD_MAX_SLABS; i++) {
1658 		if (jbd_slab[i])
1659 			kmem_cache_destroy(jbd_slab[i]);
1660 		jbd_slab[i] = NULL;
1661 	}
1662 }
1663 
1664 static int jbd2_journal_create_jbd_slab(size_t slab_size)
1665 {
1666 	int i = JBD_SLAB_INDEX(slab_size);
1667 
1668 	BUG_ON(i >= JBD_MAX_SLABS);
1669 
1670 	/*
1671 	 * Check if we already have a slab created for this size
1672 	 */
1673 	if (jbd_slab[i])
1674 		return 0;
1675 
1676 	/*
1677 	 * Create a slab and force alignment to be same as slabsize -
1678 	 * this will make sure that allocations won't cross the page
1679 	 * boundary.
1680 	 */
1681 	jbd_slab[i] = kmem_cache_create(jbd_slab_names[i],
1682 				slab_size, slab_size, 0, NULL, NULL);
1683 	if (!jbd_slab[i]) {
1684 		printk(KERN_EMERG "JBD: no memory for jbd_slab cache\n");
1685 		return -ENOMEM;
1686 	}
1687 	return 0;
1688 }
1689 
1690 void * jbd2_slab_alloc(size_t size, gfp_t flags)
1691 {
1692 	int idx;
1693 
1694 	idx = JBD_SLAB_INDEX(size);
1695 	BUG_ON(jbd_slab[idx] == NULL);
1696 	return kmem_cache_alloc(jbd_slab[idx], flags | __GFP_NOFAIL);
1697 }
1698 
1699 void jbd2_slab_free(void *ptr,  size_t size)
1700 {
1701 	int idx;
1702 
1703 	idx = JBD_SLAB_INDEX(size);
1704 	BUG_ON(jbd_slab[idx] == NULL);
1705 	kmem_cache_free(jbd_slab[idx], ptr);
1706 }
1707 
1708 /*
1709  * Journal_head storage management
1710  */
1711 static struct kmem_cache *jbd2_journal_head_cache;
1712 #ifdef CONFIG_JBD_DEBUG
1713 static atomic_t nr_journal_heads = ATOMIC_INIT(0);
1714 #endif
1715 
1716 static int journal_init_jbd2_journal_head_cache(void)
1717 {
1718 	int retval;
1719 
1720 	J_ASSERT(jbd2_journal_head_cache == 0);
1721 	jbd2_journal_head_cache = kmem_cache_create("jbd2_journal_head",
1722 				sizeof(struct journal_head),
1723 				0,		/* offset */
1724 				0,		/* flags */
1725 				NULL,		/* ctor */
1726 				NULL);		/* dtor */
1727 	retval = 0;
1728 	if (jbd2_journal_head_cache == 0) {
1729 		retval = -ENOMEM;
1730 		printk(KERN_EMERG "JBD: no memory for journal_head cache\n");
1731 	}
1732 	return retval;
1733 }
1734 
1735 static void jbd2_journal_destroy_jbd2_journal_head_cache(void)
1736 {
1737 	J_ASSERT(jbd2_journal_head_cache != NULL);
1738 	kmem_cache_destroy(jbd2_journal_head_cache);
1739 	jbd2_journal_head_cache = NULL;
1740 }
1741 
1742 /*
1743  * journal_head splicing and dicing
1744  */
1745 static struct journal_head *journal_alloc_journal_head(void)
1746 {
1747 	struct journal_head *ret;
1748 	static unsigned long last_warning;
1749 
1750 #ifdef CONFIG_JBD_DEBUG
1751 	atomic_inc(&nr_journal_heads);
1752 #endif
1753 	ret = kmem_cache_alloc(jbd2_journal_head_cache, GFP_NOFS);
1754 	if (ret == 0) {
1755 		jbd_debug(1, "out of memory for journal_head\n");
1756 		if (time_after(jiffies, last_warning + 5*HZ)) {
1757 			printk(KERN_NOTICE "ENOMEM in %s, retrying.\n",
1758 			       __FUNCTION__);
1759 			last_warning = jiffies;
1760 		}
1761 		while (ret == 0) {
1762 			yield();
1763 			ret = kmem_cache_alloc(jbd2_journal_head_cache, GFP_NOFS);
1764 		}
1765 	}
1766 	return ret;
1767 }
1768 
1769 static void journal_free_journal_head(struct journal_head *jh)
1770 {
1771 #ifdef CONFIG_JBD_DEBUG
1772 	atomic_dec(&nr_journal_heads);
1773 	memset(jh, JBD_POISON_FREE, sizeof(*jh));
1774 #endif
1775 	kmem_cache_free(jbd2_journal_head_cache, jh);
1776 }
1777 
1778 /*
1779  * A journal_head is attached to a buffer_head whenever JBD has an
1780  * interest in the buffer.
1781  *
1782  * Whenever a buffer has an attached journal_head, its ->b_state:BH_JBD bit
1783  * is set.  This bit is tested in core kernel code where we need to take
1784  * JBD-specific actions.  Testing the zeroness of ->b_private is not reliable
1785  * there.
1786  *
1787  * When a buffer has its BH_JBD bit set, its ->b_count is elevated by one.
1788  *
1789  * When a buffer has its BH_JBD bit set it is immune from being released by
1790  * core kernel code, mainly via ->b_count.
1791  *
1792  * A journal_head may be detached from its buffer_head when the journal_head's
1793  * b_transaction, b_cp_transaction and b_next_transaction pointers are NULL.
1794  * Various places in JBD call jbd2_journal_remove_journal_head() to indicate that the
1795  * journal_head can be dropped if needed.
1796  *
1797  * Various places in the kernel want to attach a journal_head to a buffer_head
1798  * _before_ attaching the journal_head to a transaction.  To protect the
1799  * journal_head in this situation, jbd2_journal_add_journal_head elevates the
1800  * journal_head's b_jcount refcount by one.  The caller must call
1801  * jbd2_journal_put_journal_head() to undo this.
1802  *
1803  * So the typical usage would be:
1804  *
1805  *	(Attach a journal_head if needed.  Increments b_jcount)
1806  *	struct journal_head *jh = jbd2_journal_add_journal_head(bh);
1807  *	...
1808  *	jh->b_transaction = xxx;
1809  *	jbd2_journal_put_journal_head(jh);
1810  *
1811  * Now, the journal_head's b_jcount is zero, but it is safe from being released
1812  * because it has a non-zero b_transaction.
1813  */
1814 
1815 /*
1816  * Give a buffer_head a journal_head.
1817  *
1818  * Doesn't need the journal lock.
1819  * May sleep.
1820  */
1821 struct journal_head *jbd2_journal_add_journal_head(struct buffer_head *bh)
1822 {
1823 	struct journal_head *jh;
1824 	struct journal_head *new_jh = NULL;
1825 
1826 repeat:
1827 	if (!buffer_jbd(bh)) {
1828 		new_jh = journal_alloc_journal_head();
1829 		memset(new_jh, 0, sizeof(*new_jh));
1830 	}
1831 
1832 	jbd_lock_bh_journal_head(bh);
1833 	if (buffer_jbd(bh)) {
1834 		jh = bh2jh(bh);
1835 	} else {
1836 		J_ASSERT_BH(bh,
1837 			(atomic_read(&bh->b_count) > 0) ||
1838 			(bh->b_page && bh->b_page->mapping));
1839 
1840 		if (!new_jh) {
1841 			jbd_unlock_bh_journal_head(bh);
1842 			goto repeat;
1843 		}
1844 
1845 		jh = new_jh;
1846 		new_jh = NULL;		/* We consumed it */
1847 		set_buffer_jbd(bh);
1848 		bh->b_private = jh;
1849 		jh->b_bh = bh;
1850 		get_bh(bh);
1851 		BUFFER_TRACE(bh, "added journal_head");
1852 	}
1853 	jh->b_jcount++;
1854 	jbd_unlock_bh_journal_head(bh);
1855 	if (new_jh)
1856 		journal_free_journal_head(new_jh);
1857 	return bh->b_private;
1858 }
1859 
1860 /*
1861  * Grab a ref against this buffer_head's journal_head.  If it ended up not
1862  * having a journal_head, return NULL
1863  */
1864 struct journal_head *jbd2_journal_grab_journal_head(struct buffer_head *bh)
1865 {
1866 	struct journal_head *jh = NULL;
1867 
1868 	jbd_lock_bh_journal_head(bh);
1869 	if (buffer_jbd(bh)) {
1870 		jh = bh2jh(bh);
1871 		jh->b_jcount++;
1872 	}
1873 	jbd_unlock_bh_journal_head(bh);
1874 	return jh;
1875 }
1876 
1877 static void __journal_remove_journal_head(struct buffer_head *bh)
1878 {
1879 	struct journal_head *jh = bh2jh(bh);
1880 
1881 	J_ASSERT_JH(jh, jh->b_jcount >= 0);
1882 
1883 	get_bh(bh);
1884 	if (jh->b_jcount == 0) {
1885 		if (jh->b_transaction == NULL &&
1886 				jh->b_next_transaction == NULL &&
1887 				jh->b_cp_transaction == NULL) {
1888 			J_ASSERT_JH(jh, jh->b_jlist == BJ_None);
1889 			J_ASSERT_BH(bh, buffer_jbd(bh));
1890 			J_ASSERT_BH(bh, jh2bh(jh) == bh);
1891 			BUFFER_TRACE(bh, "remove journal_head");
1892 			if (jh->b_frozen_data) {
1893 				printk(KERN_WARNING "%s: freeing "
1894 						"b_frozen_data\n",
1895 						__FUNCTION__);
1896 				jbd2_slab_free(jh->b_frozen_data, bh->b_size);
1897 			}
1898 			if (jh->b_committed_data) {
1899 				printk(KERN_WARNING "%s: freeing "
1900 						"b_committed_data\n",
1901 						__FUNCTION__);
1902 				jbd2_slab_free(jh->b_committed_data, bh->b_size);
1903 			}
1904 			bh->b_private = NULL;
1905 			jh->b_bh = NULL;	/* debug, really */
1906 			clear_buffer_jbd(bh);
1907 			__brelse(bh);
1908 			journal_free_journal_head(jh);
1909 		} else {
1910 			BUFFER_TRACE(bh, "journal_head was locked");
1911 		}
1912 	}
1913 }
1914 
1915 /*
1916  * jbd2_journal_remove_journal_head(): if the buffer isn't attached to a transaction
1917  * and has a zero b_jcount then remove and release its journal_head.   If we did
1918  * see that the buffer is not used by any transaction we also "logically"
1919  * decrement ->b_count.
1920  *
1921  * We in fact take an additional increment on ->b_count as a convenience,
1922  * because the caller usually wants to do additional things with the bh
1923  * after calling here.
1924  * The caller of jbd2_journal_remove_journal_head() *must* run __brelse(bh) at some
1925  * time.  Once the caller has run __brelse(), the buffer is eligible for
1926  * reaping by try_to_free_buffers().
1927  */
1928 void jbd2_journal_remove_journal_head(struct buffer_head *bh)
1929 {
1930 	jbd_lock_bh_journal_head(bh);
1931 	__journal_remove_journal_head(bh);
1932 	jbd_unlock_bh_journal_head(bh);
1933 }
1934 
1935 /*
1936  * Drop a reference on the passed journal_head.  If it fell to zero then try to
1937  * release the journal_head from the buffer_head.
1938  */
1939 void jbd2_journal_put_journal_head(struct journal_head *jh)
1940 {
1941 	struct buffer_head *bh = jh2bh(jh);
1942 
1943 	jbd_lock_bh_journal_head(bh);
1944 	J_ASSERT_JH(jh, jh->b_jcount > 0);
1945 	--jh->b_jcount;
1946 	if (!jh->b_jcount && !jh->b_transaction) {
1947 		__journal_remove_journal_head(bh);
1948 		__brelse(bh);
1949 	}
1950 	jbd_unlock_bh_journal_head(bh);
1951 }
1952 
1953 /*
1954  * /proc tunables
1955  */
1956 #if defined(CONFIG_JBD_DEBUG)
1957 int jbd2_journal_enable_debug;
1958 EXPORT_SYMBOL(jbd2_journal_enable_debug);
1959 #endif
1960 
1961 #if defined(CONFIG_JBD_DEBUG) && defined(CONFIG_PROC_FS)
1962 
1963 static struct proc_dir_entry *proc_jbd_debug;
1964 
1965 static int read_jbd_debug(char *page, char **start, off_t off,
1966 			  int count, int *eof, void *data)
1967 {
1968 	int ret;
1969 
1970 	ret = sprintf(page + off, "%d\n", jbd2_journal_enable_debug);
1971 	*eof = 1;
1972 	return ret;
1973 }
1974 
1975 static int write_jbd_debug(struct file *file, const char __user *buffer,
1976 			   unsigned long count, void *data)
1977 {
1978 	char buf[32];
1979 
1980 	if (count > ARRAY_SIZE(buf) - 1)
1981 		count = ARRAY_SIZE(buf) - 1;
1982 	if (copy_from_user(buf, buffer, count))
1983 		return -EFAULT;
1984 	buf[ARRAY_SIZE(buf) - 1] = '\0';
1985 	jbd2_journal_enable_debug = simple_strtoul(buf, NULL, 10);
1986 	return count;
1987 }
1988 
1989 #define JBD_PROC_NAME "sys/fs/jbd2-debug"
1990 
1991 static void __init create_jbd_proc_entry(void)
1992 {
1993 	proc_jbd_debug = create_proc_entry(JBD_PROC_NAME, 0644, NULL);
1994 	if (proc_jbd_debug) {
1995 		/* Why is this so hard? */
1996 		proc_jbd_debug->read_proc = read_jbd_debug;
1997 		proc_jbd_debug->write_proc = write_jbd_debug;
1998 	}
1999 }
2000 
2001 static void __exit jbd2_remove_jbd_proc_entry(void)
2002 {
2003 	if (proc_jbd_debug)
2004 		remove_proc_entry(JBD_PROC_NAME, NULL);
2005 }
2006 
2007 #else
2008 
2009 #define create_jbd_proc_entry() do {} while (0)
2010 #define jbd2_remove_jbd_proc_entry() do {} while (0)
2011 
2012 #endif
2013 
2014 struct kmem_cache *jbd2_handle_cache;
2015 
2016 static int __init journal_init_handle_cache(void)
2017 {
2018 	jbd2_handle_cache = kmem_cache_create("jbd2_journal_handle",
2019 				sizeof(handle_t),
2020 				0,		/* offset */
2021 				0,		/* flags */
2022 				NULL,		/* ctor */
2023 				NULL);		/* dtor */
2024 	if (jbd2_handle_cache == NULL) {
2025 		printk(KERN_EMERG "JBD: failed to create handle cache\n");
2026 		return -ENOMEM;
2027 	}
2028 	return 0;
2029 }
2030 
2031 static void jbd2_journal_destroy_handle_cache(void)
2032 {
2033 	if (jbd2_handle_cache)
2034 		kmem_cache_destroy(jbd2_handle_cache);
2035 }
2036 
2037 /*
2038  * Module startup and shutdown
2039  */
2040 
2041 static int __init journal_init_caches(void)
2042 {
2043 	int ret;
2044 
2045 	ret = jbd2_journal_init_revoke_caches();
2046 	if (ret == 0)
2047 		ret = journal_init_jbd2_journal_head_cache();
2048 	if (ret == 0)
2049 		ret = journal_init_handle_cache();
2050 	return ret;
2051 }
2052 
2053 static void jbd2_journal_destroy_caches(void)
2054 {
2055 	jbd2_journal_destroy_revoke_caches();
2056 	jbd2_journal_destroy_jbd2_journal_head_cache();
2057 	jbd2_journal_destroy_handle_cache();
2058 	jbd2_journal_destroy_jbd_slabs();
2059 }
2060 
2061 static int __init journal_init(void)
2062 {
2063 	int ret;
2064 
2065 	BUILD_BUG_ON(sizeof(struct journal_superblock_s) != 1024);
2066 
2067 	ret = journal_init_caches();
2068 	if (ret != 0)
2069 		jbd2_journal_destroy_caches();
2070 	create_jbd_proc_entry();
2071 	return ret;
2072 }
2073 
2074 static void __exit journal_exit(void)
2075 {
2076 #ifdef CONFIG_JBD_DEBUG
2077 	int n = atomic_read(&nr_journal_heads);
2078 	if (n)
2079 		printk(KERN_EMERG "JBD: leaked %d journal_heads!\n", n);
2080 #endif
2081 	jbd2_remove_jbd_proc_entry();
2082 	jbd2_journal_destroy_caches();
2083 }
2084 
2085 MODULE_LICENSE("GPL");
2086 module_init(journal_init);
2087 module_exit(journal_exit);
2088 
2089