2 * linux/fs/jbd/journal.c
4 * Written by Stephen C. Tweedie <sct@redhat.com>, 1998
6 * Copyright 1998 Red Hat corp --- All Rights Reserved
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.
12 * Generic filesystem journal-writing code; part of the ext2fs
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.
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).
25 #include <linux/module.h>
26 #include <linux/time.h>
28 #include <linux/jbd.h>
29 #include <linux/errno.h>
30 #include <linux/slab.h>
31 #include <linux/init.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>
39 #include <asm/uaccess.h>
42 EXPORT_SYMBOL(journal_start);
43 EXPORT_SYMBOL(journal_restart);
44 EXPORT_SYMBOL(journal_extend);
45 EXPORT_SYMBOL(journal_stop);
46 EXPORT_SYMBOL(journal_lock_updates);
47 EXPORT_SYMBOL(journal_unlock_updates);
48 EXPORT_SYMBOL(journal_get_write_access);
49 EXPORT_SYMBOL(journal_get_create_access);
50 EXPORT_SYMBOL(journal_get_undo_access);
51 EXPORT_SYMBOL(journal_dirty_data);
52 EXPORT_SYMBOL(journal_dirty_metadata);
53 EXPORT_SYMBOL(journal_release_buffer);
54 EXPORT_SYMBOL(journal_forget);
56 EXPORT_SYMBOL(journal_sync_buffer);
58 EXPORT_SYMBOL(journal_flush);
59 EXPORT_SYMBOL(journal_revoke);
61 EXPORT_SYMBOL(journal_init_dev);
62 EXPORT_SYMBOL(journal_init_inode);
63 EXPORT_SYMBOL(journal_update_format);
64 EXPORT_SYMBOL(journal_check_used_features);
65 EXPORT_SYMBOL(journal_check_available_features);
66 EXPORT_SYMBOL(journal_set_features);
67 EXPORT_SYMBOL(journal_create);
68 EXPORT_SYMBOL(journal_load);
69 EXPORT_SYMBOL(journal_destroy);
70 EXPORT_SYMBOL(journal_update_superblock);
71 EXPORT_SYMBOL(journal_abort);
72 EXPORT_SYMBOL(journal_errno);
73 EXPORT_SYMBOL(journal_ack_err);
74 EXPORT_SYMBOL(journal_clear_err);
75 EXPORT_SYMBOL(log_wait_commit);
76 EXPORT_SYMBOL(journal_start_commit);
77 EXPORT_SYMBOL(journal_force_commit_nested);
78 EXPORT_SYMBOL(journal_wipe);
79 EXPORT_SYMBOL(journal_blocks_per_page);
80 EXPORT_SYMBOL(journal_invalidatepage);
81 EXPORT_SYMBOL(journal_try_to_free_buffers);
82 EXPORT_SYMBOL(journal_force_commit);
84 static int journal_convert_superblock_v1(journal_t *, journal_superblock_t *);
85 static void __journal_abort_soft (journal_t *journal, int errno);
88 * Helper function used to manage commit timeouts
91 static void commit_timeout(unsigned long __data)
93 struct task_struct * p = (struct task_struct *) __data;
99 * kjournald: The main thread function used to manage a logging device
102 * This kernel thread is responsible for two things:
104 * 1) COMMIT: Every so often we need to commit the current state of the
105 * filesystem to disk. The journal thread is responsible for writing
106 * all of the metadata buffers to disk.
108 * 2) CHECKPOINT: We cannot reuse a used section of the log file until all
109 * of the data in that part of the log has been rewritten elsewhere on
110 * the disk. Flushing these old buffers to reclaim space in the log is
111 * known as checkpointing, and this thread is responsible for that job.
114 static int kjournald(void *arg)
116 journal_t *journal = arg;
117 transaction_t *transaction;
120 * Set up an interval timer which can be used to trigger a commit wakeup
121 * after the commit interval expires
123 setup_timer(&journal->j_commit_timer, commit_timeout,
124 (unsigned long)current);
126 /* Record that the journal thread is running */
127 journal->j_task = current;
128 wake_up(&journal->j_wait_done_commit);
130 printk(KERN_INFO "kjournald starting. Commit interval %ld seconds\n",
131 journal->j_commit_interval / HZ);
134 * And now, wait forever for commit wakeup events.
136 spin_lock(&journal->j_state_lock);
139 if (journal->j_flags & JFS_UNMOUNT)
142 jbd_debug(1, "commit_sequence=%d, commit_request=%d\n",
143 journal->j_commit_sequence, journal->j_commit_request);
145 if (journal->j_commit_sequence != journal->j_commit_request) {
146 jbd_debug(1, "OK, requests differ\n");
147 spin_unlock(&journal->j_state_lock);
148 del_timer_sync(&journal->j_commit_timer);
149 journal_commit_transaction(journal);
150 spin_lock(&journal->j_state_lock);
154 wake_up(&journal->j_wait_done_commit);
155 if (freezing(current)) {
157 * The simpler the better. Flushing journal isn't a
158 * good idea, because that depends on threads that may
159 * be already stopped.
161 jbd_debug(1, "Now suspending kjournald\n");
162 spin_unlock(&journal->j_state_lock);
164 spin_lock(&journal->j_state_lock);
167 * We assume on resume that commits are already there,
171 int should_sleep = 1;
173 prepare_to_wait(&journal->j_wait_commit, &wait,
175 if (journal->j_commit_sequence != journal->j_commit_request)
177 transaction = journal->j_running_transaction;
178 if (transaction && time_after_eq(jiffies,
179 transaction->t_expires))
181 if (journal->j_flags & JFS_UNMOUNT)
184 spin_unlock(&journal->j_state_lock);
186 spin_lock(&journal->j_state_lock);
188 finish_wait(&journal->j_wait_commit, &wait);
191 jbd_debug(1, "kjournald wakes\n");
194 * Were we woken up by a commit wakeup event?
196 transaction = journal->j_running_transaction;
197 if (transaction && time_after_eq(jiffies, transaction->t_expires)) {
198 journal->j_commit_request = transaction->t_tid;
199 jbd_debug(1, "woke because of timeout\n");
204 spin_unlock(&journal->j_state_lock);
205 del_timer_sync(&journal->j_commit_timer);
206 journal->j_task = NULL;
207 wake_up(&journal->j_wait_done_commit);
208 jbd_debug(1, "Journal thread exiting.\n");
212 static int journal_start_thread(journal_t *journal)
214 struct task_struct *t;
216 t = kthread_run(kjournald, journal, "kjournald");
220 wait_event(journal->j_wait_done_commit, journal->j_task != 0);
224 static void journal_kill_thread(journal_t *journal)
226 spin_lock(&journal->j_state_lock);
227 journal->j_flags |= JFS_UNMOUNT;
229 while (journal->j_task) {
230 wake_up(&journal->j_wait_commit);
231 spin_unlock(&journal->j_state_lock);
232 wait_event(journal->j_wait_done_commit, journal->j_task == 0);
233 spin_lock(&journal->j_state_lock);
235 spin_unlock(&journal->j_state_lock);
239 * journal_write_metadata_buffer: write a metadata buffer to the journal.
241 * Writes a metadata buffer to a given disk block. The actual IO is not
242 * performed but a new buffer_head is constructed which labels the data
243 * to be written with the correct destination disk block.
245 * Any magic-number escaping which needs to be done will cause a
246 * copy-out here. If the buffer happens to start with the
247 * JFS_MAGIC_NUMBER, then we can't write it to the log directly: the
248 * magic number is only written to the log for descripter blocks. In
249 * this case, we copy the data and replace the first word with 0, and we
250 * return a result code which indicates that this buffer needs to be
251 * marked as an escaped buffer in the corresponding log descriptor
252 * block. The missing word can then be restored when the block is read
255 * If the source buffer has already been modified by a new transaction
256 * since we took the last commit snapshot, we use the frozen copy of
257 * that data for IO. If we end up using the existing buffer_head's data
258 * for the write, then we *have* to lock the buffer to prevent anyone
259 * else from using and possibly modifying it while the IO is in
262 * The function returns a pointer to the buffer_heads to be used for IO.
264 * We assume that the journal has already been locked in this function.
271 * Bit 0 set == escape performed on the data
272 * Bit 1 set == buffer copy-out performed (kfree the data after IO)
275 int journal_write_metadata_buffer(transaction_t *transaction,
276 struct journal_head *jh_in,
277 struct journal_head **jh_out,
278 unsigned long blocknr)
280 int need_copy_out = 0;
281 int done_copy_out = 0;
284 struct buffer_head *new_bh;
285 struct journal_head *new_jh;
286 struct page *new_page;
287 unsigned int new_offset;
288 struct buffer_head *bh_in = jh2bh(jh_in);
291 * The buffer really shouldn't be locked: only the current committing
292 * transaction is allowed to write it, so nobody else is allowed
295 * akpm: except if we're journalling data, and write() output is
296 * also part of a shared mapping, and another thread has
297 * decided to launch a writepage() against this buffer.
299 J_ASSERT_BH(bh_in, buffer_jbddirty(bh_in));
301 new_bh = alloc_buffer_head(GFP_NOFS|__GFP_NOFAIL);
304 * If a new transaction has already done a buffer copy-out, then
305 * we use that version of the data for the commit.
307 jbd_lock_bh_state(bh_in);
309 if (jh_in->b_frozen_data) {
311 new_page = virt_to_page(jh_in->b_frozen_data);
312 new_offset = offset_in_page(jh_in->b_frozen_data);
314 new_page = jh2bh(jh_in)->b_page;
315 new_offset = offset_in_page(jh2bh(jh_in)->b_data);
318 mapped_data = kmap_atomic(new_page, KM_USER0);
322 if (*((__be32 *)(mapped_data + new_offset)) ==
323 cpu_to_be32(JFS_MAGIC_NUMBER)) {
327 kunmap_atomic(mapped_data, KM_USER0);
330 * Do we need to do a data copy?
332 if (need_copy_out && !done_copy_out) {
335 jbd_unlock_bh_state(bh_in);
336 tmp = jbd_alloc(bh_in->b_size, GFP_NOFS);
337 jbd_lock_bh_state(bh_in);
338 if (jh_in->b_frozen_data) {
339 jbd_free(tmp, bh_in->b_size);
343 jh_in->b_frozen_data = tmp;
344 mapped_data = kmap_atomic(new_page, KM_USER0);
345 memcpy(tmp, mapped_data + new_offset, jh2bh(jh_in)->b_size);
346 kunmap_atomic(mapped_data, KM_USER0);
348 new_page = virt_to_page(tmp);
349 new_offset = offset_in_page(tmp);
354 * Did we need to do an escaping? Now we've done all the
355 * copying, we can finally do so.
358 mapped_data = kmap_atomic(new_page, KM_USER0);
359 *((unsigned int *)(mapped_data + new_offset)) = 0;
360 kunmap_atomic(mapped_data, KM_USER0);
363 /* keep subsequent assertions sane */
365 init_buffer(new_bh, NULL, NULL);
366 atomic_set(&new_bh->b_count, 1);
367 jbd_unlock_bh_state(bh_in);
369 new_jh = journal_add_journal_head(new_bh); /* This sleeps */
371 set_bh_page(new_bh, new_page, new_offset);
372 new_jh->b_transaction = NULL;
373 new_bh->b_size = jh2bh(jh_in)->b_size;
374 new_bh->b_bdev = transaction->t_journal->j_dev;
375 new_bh->b_blocknr = blocknr;
376 set_buffer_mapped(new_bh);
377 set_buffer_dirty(new_bh);
382 * The to-be-written buffer needs to get moved to the io queue,
383 * and the original buffer whose contents we are shadowing or
384 * copying is moved to the transaction's shadow queue.
386 JBUFFER_TRACE(jh_in, "file as BJ_Shadow");
387 journal_file_buffer(jh_in, transaction, BJ_Shadow);
388 JBUFFER_TRACE(new_jh, "file as BJ_IO");
389 journal_file_buffer(new_jh, transaction, BJ_IO);
391 return do_escape | (done_copy_out << 1);
395 * Allocation code for the journal file. Manage the space left in the
396 * journal, so that we can begin checkpointing when appropriate.
400 * __log_space_left: Return the number of free blocks left in the journal.
402 * Called with the journal already locked.
404 * Called under j_state_lock
407 int __log_space_left(journal_t *journal)
409 int left = journal->j_free;
411 assert_spin_locked(&journal->j_state_lock);
414 * Be pessimistic here about the number of those free blocks which
415 * might be required for log descriptor control blocks.
418 #define MIN_LOG_RESERVED_BLOCKS 32 /* Allow for rounding errors */
420 left -= MIN_LOG_RESERVED_BLOCKS;
429 * Called under j_state_lock. Returns true if a transaction was started.
431 int __log_start_commit(journal_t *journal, tid_t target)
434 * Are we already doing a recent enough commit?
436 if (!tid_geq(journal->j_commit_request, target)) {
438 * We want a new commit: OK, mark the request and wakup the
439 * commit thread. We do _not_ do the commit ourselves.
442 journal->j_commit_request = target;
443 jbd_debug(1, "JBD: requesting commit %d/%d\n",
444 journal->j_commit_request,
445 journal->j_commit_sequence);
446 wake_up(&journal->j_wait_commit);
452 int log_start_commit(journal_t *journal, tid_t tid)
456 spin_lock(&journal->j_state_lock);
457 ret = __log_start_commit(journal, tid);
458 spin_unlock(&journal->j_state_lock);
463 * Force and wait upon a commit if the calling process is not within
464 * transaction. This is used for forcing out undo-protected data which contains
465 * bitmaps, when the fs is running out of space.
467 * We can only force the running transaction if we don't have an active handle;
468 * otherwise, we will deadlock.
470 * Returns true if a transaction was started.
472 int journal_force_commit_nested(journal_t *journal)
474 transaction_t *transaction = NULL;
477 spin_lock(&journal->j_state_lock);
478 if (journal->j_running_transaction && !current->journal_info) {
479 transaction = journal->j_running_transaction;
480 __log_start_commit(journal, transaction->t_tid);
481 } else if (journal->j_committing_transaction)
482 transaction = journal->j_committing_transaction;
485 spin_unlock(&journal->j_state_lock);
486 return 0; /* Nothing to retry */
489 tid = transaction->t_tid;
490 spin_unlock(&journal->j_state_lock);
491 log_wait_commit(journal, tid);
496 * Start a commit of the current running transaction (if any). Returns true
497 * if a transaction was started, and fills its tid in at *ptid
499 int journal_start_commit(journal_t *journal, tid_t *ptid)
503 spin_lock(&journal->j_state_lock);
504 if (journal->j_running_transaction) {
505 tid_t tid = journal->j_running_transaction->t_tid;
507 ret = __log_start_commit(journal, tid);
510 } else if (journal->j_committing_transaction && ptid) {
512 * If ext3_write_super() recently started a commit, then we
513 * have to wait for completion of that transaction
515 *ptid = journal->j_committing_transaction->t_tid;
518 spin_unlock(&journal->j_state_lock);
523 * Wait for a specified commit to complete.
524 * The caller may not hold the journal lock.
526 int log_wait_commit(journal_t *journal, tid_t tid)
530 #ifdef CONFIG_JBD_DEBUG
531 spin_lock(&journal->j_state_lock);
532 if (!tid_geq(journal->j_commit_request, tid)) {
534 "%s: error: j_commit_request=%d, tid=%d\n",
535 __FUNCTION__, journal->j_commit_request, tid);
537 spin_unlock(&journal->j_state_lock);
539 spin_lock(&journal->j_state_lock);
540 while (tid_gt(tid, journal->j_commit_sequence)) {
541 jbd_debug(1, "JBD: want %d, j_commit_sequence=%d\n",
542 tid, journal->j_commit_sequence);
543 wake_up(&journal->j_wait_commit);
544 spin_unlock(&journal->j_state_lock);
545 wait_event(journal->j_wait_done_commit,
546 !tid_gt(tid, journal->j_commit_sequence));
547 spin_lock(&journal->j_state_lock);
549 spin_unlock(&journal->j_state_lock);
551 if (unlikely(is_journal_aborted(journal))) {
552 printk(KERN_EMERG "journal commit I/O error\n");
559 * Log buffer allocation routines:
562 int journal_next_log_block(journal_t *journal, unsigned long *retp)
564 unsigned long blocknr;
566 spin_lock(&journal->j_state_lock);
567 J_ASSERT(journal->j_free > 1);
569 blocknr = journal->j_head;
572 if (journal->j_head == journal->j_last)
573 journal->j_head = journal->j_first;
574 spin_unlock(&journal->j_state_lock);
575 return journal_bmap(journal, blocknr, retp);
579 * Conversion of logical to physical block numbers for the journal
581 * On external journals the journal blocks are identity-mapped, so
582 * this is a no-op. If needed, we can use j_blk_offset - everything is
585 int journal_bmap(journal_t *journal, unsigned long blocknr,
591 if (journal->j_inode) {
592 ret = bmap(journal->j_inode, blocknr);
596 char b[BDEVNAME_SIZE];
598 printk(KERN_ALERT "%s: journal block not found "
599 "at offset %lu on %s\n",
602 bdevname(journal->j_dev, b));
604 __journal_abort_soft(journal, err);
607 *retp = blocknr; /* +journal->j_blk_offset */
613 * We play buffer_head aliasing tricks to write data/metadata blocks to
614 * the journal without copying their contents, but for journal
615 * descriptor blocks we do need to generate bona fide buffers.
617 * After the caller of journal_get_descriptor_buffer() has finished modifying
618 * the buffer's contents they really should run flush_dcache_page(bh->b_page).
619 * But we don't bother doing that, so there will be coherency problems with
620 * mmaps of blockdevs which hold live JBD-controlled filesystems.
622 struct journal_head *journal_get_descriptor_buffer(journal_t *journal)
624 struct buffer_head *bh;
625 unsigned long blocknr;
628 err = journal_next_log_block(journal, &blocknr);
633 bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
635 memset(bh->b_data, 0, journal->j_blocksize);
636 set_buffer_uptodate(bh);
638 BUFFER_TRACE(bh, "return this buffer");
639 return journal_add_journal_head(bh);
643 * Management for journal control blocks: functions to create and
644 * destroy journal_t structures, and to initialise and read existing
645 * journal blocks from disk. */
647 /* First: create and setup a journal_t object in memory. We initialise
648 * very few fields yet: that has to wait until we have created the
649 * journal structures from from scratch, or loaded them from disk. */
651 static journal_t * journal_init_common (void)
656 journal = jbd_kmalloc(sizeof(*journal), GFP_KERNEL);
659 memset(journal, 0, sizeof(*journal));
661 init_waitqueue_head(&journal->j_wait_transaction_locked);
662 init_waitqueue_head(&journal->j_wait_logspace);
663 init_waitqueue_head(&journal->j_wait_done_commit);
664 init_waitqueue_head(&journal->j_wait_checkpoint);
665 init_waitqueue_head(&journal->j_wait_commit);
666 init_waitqueue_head(&journal->j_wait_updates);
667 mutex_init(&journal->j_barrier);
668 mutex_init(&journal->j_checkpoint_mutex);
669 spin_lock_init(&journal->j_revoke_lock);
670 spin_lock_init(&journal->j_list_lock);
671 spin_lock_init(&journal->j_state_lock);
673 journal->j_commit_interval = (HZ * JBD_DEFAULT_MAX_COMMIT_AGE);
675 /* The journal is marked for error until we succeed with recovery! */
676 journal->j_flags = JFS_ABORT;
678 /* Set up a default-sized revoke table for the new mount. */
679 err = journal_init_revoke(journal, JOURNAL_REVOKE_DEFAULT_HASH);
689 /* journal_init_dev and journal_init_inode:
691 * Create a journal structure assigned some fixed set of disk blocks to
692 * the journal. We don't actually touch those disk blocks yet, but we
693 * need to set up all of the mapping information to tell the journaling
694 * system where the journal blocks are.
699 * journal_t * journal_init_dev() - creates an initialises a journal structure
700 * @bdev: Block device on which to create the journal
701 * @fs_dev: Device which hold journalled filesystem for this journal.
702 * @start: Block nr Start of journal.
703 * @len: Length of the journal in blocks.
704 * @blocksize: blocksize of journalling device
705 * @returns: a newly created journal_t *
707 * journal_init_dev creates a journal which maps a fixed contiguous
708 * range of blocks on an arbitrary block device.
711 journal_t * journal_init_dev(struct block_device *bdev,
712 struct block_device *fs_dev,
713 int start, int len, int blocksize)
715 journal_t *journal = journal_init_common();
716 struct buffer_head *bh;
722 /* journal descriptor can store up to n blocks -bzzz */
723 journal->j_blocksize = blocksize;
724 n = journal->j_blocksize / sizeof(journal_block_tag_t);
725 journal->j_wbufsize = n;
726 journal->j_wbuf = kmalloc(n * sizeof(struct buffer_head*), GFP_KERNEL);
727 if (!journal->j_wbuf) {
728 printk(KERN_ERR "%s: Cant allocate bhs for commit thread\n",
734 journal->j_dev = bdev;
735 journal->j_fs_dev = fs_dev;
736 journal->j_blk_offset = start;
737 journal->j_maxlen = len;
739 bh = __getblk(journal->j_dev, start, journal->j_blocksize);
740 J_ASSERT(bh != NULL);
741 journal->j_sb_buffer = bh;
742 journal->j_superblock = (journal_superblock_t *)bh->b_data;
748 * journal_t * journal_init_inode () - creates a journal which maps to a inode.
749 * @inode: An inode to create the journal in
751 * journal_init_inode creates a journal which maps an on-disk inode as
752 * the journal. The inode must exist already, must support bmap() and
753 * must have all data blocks preallocated.
755 journal_t * journal_init_inode (struct inode *inode)
757 struct buffer_head *bh;
758 journal_t *journal = journal_init_common();
761 unsigned long blocknr;
766 journal->j_dev = journal->j_fs_dev = inode->i_sb->s_bdev;
767 journal->j_inode = inode;
769 "journal %p: inode %s/%ld, size %Ld, bits %d, blksize %ld\n",
770 journal, inode->i_sb->s_id, inode->i_ino,
771 (long long) inode->i_size,
772 inode->i_sb->s_blocksize_bits, inode->i_sb->s_blocksize);
774 journal->j_maxlen = inode->i_size >> inode->i_sb->s_blocksize_bits;
775 journal->j_blocksize = inode->i_sb->s_blocksize;
777 /* journal descriptor can store up to n blocks -bzzz */
778 n = journal->j_blocksize / sizeof(journal_block_tag_t);
779 journal->j_wbufsize = n;
780 journal->j_wbuf = kmalloc(n * sizeof(struct buffer_head*), GFP_KERNEL);
781 if (!journal->j_wbuf) {
782 printk(KERN_ERR "%s: Cant allocate bhs for commit thread\n",
788 err = journal_bmap(journal, 0, &blocknr);
789 /* If that failed, give up */
791 printk(KERN_ERR "%s: Cannnot locate journal superblock\n",
797 bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
798 J_ASSERT(bh != NULL);
799 journal->j_sb_buffer = bh;
800 journal->j_superblock = (journal_superblock_t *)bh->b_data;
806 * If the journal init or create aborts, we need to mark the journal
807 * superblock as being NULL to prevent the journal destroy from writing
808 * back a bogus superblock.
810 static void journal_fail_superblock (journal_t *journal)
812 struct buffer_head *bh = journal->j_sb_buffer;
814 journal->j_sb_buffer = NULL;
818 * Given a journal_t structure, initialise the various fields for
819 * startup of a new journaling session. We use this both when creating
820 * a journal, and after recovering an old journal to reset it for
824 static int journal_reset(journal_t *journal)
826 journal_superblock_t *sb = journal->j_superblock;
827 unsigned long first, last;
829 first = be32_to_cpu(sb->s_first);
830 last = be32_to_cpu(sb->s_maxlen);
832 journal->j_first = first;
833 journal->j_last = last;
835 journal->j_head = first;
836 journal->j_tail = first;
837 journal->j_free = last - first;
839 journal->j_tail_sequence = journal->j_transaction_sequence;
840 journal->j_commit_sequence = journal->j_transaction_sequence - 1;
841 journal->j_commit_request = journal->j_commit_sequence;
843 journal->j_max_transaction_buffers = journal->j_maxlen / 4;
845 /* Add the dynamic fields and write it to disk. */
846 journal_update_superblock(journal, 1);
847 return journal_start_thread(journal);
851 * int journal_create() - Initialise the new journal file
852 * @journal: Journal to create. This structure must have been initialised
854 * Given a journal_t structure which tells us which disk blocks we can
855 * use, create a new journal superblock and initialise all of the
856 * journal fields from scratch.
858 int journal_create(journal_t *journal)
860 unsigned long blocknr;
861 struct buffer_head *bh;
862 journal_superblock_t *sb;
865 if (journal->j_maxlen < JFS_MIN_JOURNAL_BLOCKS) {
866 printk (KERN_ERR "Journal length (%d blocks) too short.\n",
868 journal_fail_superblock(journal);
872 if (journal->j_inode == NULL) {
874 * We don't know what block to start at!
877 "%s: creation of journal on external device!\n",
882 /* Zero out the entire journal on disk. We cannot afford to
883 have any blocks on disk beginning with JFS_MAGIC_NUMBER. */
884 jbd_debug(1, "JBD: Zeroing out journal blocks...\n");
885 for (i = 0; i < journal->j_maxlen; i++) {
886 err = journal_bmap(journal, i, &blocknr);
889 bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
891 memset (bh->b_data, 0, journal->j_blocksize);
892 BUFFER_TRACE(bh, "marking dirty");
893 mark_buffer_dirty(bh);
894 BUFFER_TRACE(bh, "marking uptodate");
895 set_buffer_uptodate(bh);
900 sync_blockdev(journal->j_dev);
901 jbd_debug(1, "JBD: journal cleared.\n");
903 /* OK, fill in the initial static fields in the new superblock */
904 sb = journal->j_superblock;
906 sb->s_header.h_magic = cpu_to_be32(JFS_MAGIC_NUMBER);
907 sb->s_header.h_blocktype = cpu_to_be32(JFS_SUPERBLOCK_V2);
909 sb->s_blocksize = cpu_to_be32(journal->j_blocksize);
910 sb->s_maxlen = cpu_to_be32(journal->j_maxlen);
911 sb->s_first = cpu_to_be32(1);
913 journal->j_transaction_sequence = 1;
915 journal->j_flags &= ~JFS_ABORT;
916 journal->j_format_version = 2;
918 return journal_reset(journal);
922 * void journal_update_superblock() - Update journal sb on disk.
923 * @journal: The journal to update.
924 * @wait: Set to '0' if you don't want to wait for IO completion.
926 * Update a journal's dynamic superblock fields and write it to disk,
927 * optionally waiting for the IO to complete.
929 void journal_update_superblock(journal_t *journal, int wait)
931 journal_superblock_t *sb = journal->j_superblock;
932 struct buffer_head *bh = journal->j_sb_buffer;
935 * As a special case, if the on-disk copy is already marked as needing
936 * no recovery (s_start == 0) and there are no outstanding transactions
937 * in the filesystem, then we can safely defer the superblock update
938 * until the next commit by setting JFS_FLUSHED. This avoids
939 * attempting a write to a potential-readonly device.
941 if (sb->s_start == 0 && journal->j_tail_sequence ==
942 journal->j_transaction_sequence) {
943 jbd_debug(1,"JBD: Skipping superblock update on recovered sb "
944 "(start %ld, seq %d, errno %d)\n",
945 journal->j_tail, journal->j_tail_sequence,
950 spin_lock(&journal->j_state_lock);
951 jbd_debug(1,"JBD: updating superblock (start %ld, seq %d, errno %d)\n",
952 journal->j_tail, journal->j_tail_sequence, journal->j_errno);
954 sb->s_sequence = cpu_to_be32(journal->j_tail_sequence);
955 sb->s_start = cpu_to_be32(journal->j_tail);
956 sb->s_errno = cpu_to_be32(journal->j_errno);
957 spin_unlock(&journal->j_state_lock);
959 BUFFER_TRACE(bh, "marking dirty");
960 mark_buffer_dirty(bh);
962 sync_dirty_buffer(bh);
964 ll_rw_block(SWRITE, 1, &bh);
967 /* If we have just flushed the log (by marking s_start==0), then
968 * any future commit will have to be careful to update the
969 * superblock again to re-record the true start of the log. */
971 spin_lock(&journal->j_state_lock);
973 journal->j_flags &= ~JFS_FLUSHED;
975 journal->j_flags |= JFS_FLUSHED;
976 spin_unlock(&journal->j_state_lock);
980 * Read the superblock for a given journal, performing initial
981 * validation of the format.
984 static int journal_get_superblock(journal_t *journal)
986 struct buffer_head *bh;
987 journal_superblock_t *sb;
990 bh = journal->j_sb_buffer;
992 J_ASSERT(bh != NULL);
993 if (!buffer_uptodate(bh)) {
994 ll_rw_block(READ, 1, &bh);
996 if (!buffer_uptodate(bh)) {
998 "JBD: IO error reading journal superblock\n");
1003 sb = journal->j_superblock;
1007 if (sb->s_header.h_magic != cpu_to_be32(JFS_MAGIC_NUMBER) ||
1008 sb->s_blocksize != cpu_to_be32(journal->j_blocksize)) {
1009 printk(KERN_WARNING "JBD: no valid journal superblock found\n");
1013 switch(be32_to_cpu(sb->s_header.h_blocktype)) {
1014 case JFS_SUPERBLOCK_V1:
1015 journal->j_format_version = 1;
1017 case JFS_SUPERBLOCK_V2:
1018 journal->j_format_version = 2;
1021 printk(KERN_WARNING "JBD: unrecognised superblock format ID\n");
1025 if (be32_to_cpu(sb->s_maxlen) < journal->j_maxlen)
1026 journal->j_maxlen = be32_to_cpu(sb->s_maxlen);
1027 else if (be32_to_cpu(sb->s_maxlen) > journal->j_maxlen) {
1028 printk (KERN_WARNING "JBD: journal file too short\n");
1035 journal_fail_superblock(journal);
1040 * Load the on-disk journal superblock and read the key fields into the
1044 static int load_superblock(journal_t *journal)
1047 journal_superblock_t *sb;
1049 err = journal_get_superblock(journal);
1053 sb = journal->j_superblock;
1055 journal->j_tail_sequence = be32_to_cpu(sb->s_sequence);
1056 journal->j_tail = be32_to_cpu(sb->s_start);
1057 journal->j_first = be32_to_cpu(sb->s_first);
1058 journal->j_last = be32_to_cpu(sb->s_maxlen);
1059 journal->j_errno = be32_to_cpu(sb->s_errno);
1066 * int journal_load() - Read journal from disk.
1067 * @journal: Journal to act on.
1069 * Given a journal_t structure which tells us which disk blocks contain
1070 * a journal, read the journal from disk to initialise the in-memory
1073 int journal_load(journal_t *journal)
1076 journal_superblock_t *sb;
1078 err = load_superblock(journal);
1082 sb = journal->j_superblock;
1083 /* If this is a V2 superblock, then we have to check the
1084 * features flags on it. */
1086 if (journal->j_format_version >= 2) {
1087 if ((sb->s_feature_ro_compat &
1088 ~cpu_to_be32(JFS_KNOWN_ROCOMPAT_FEATURES)) ||
1089 (sb->s_feature_incompat &
1090 ~cpu_to_be32(JFS_KNOWN_INCOMPAT_FEATURES))) {
1091 printk (KERN_WARNING
1092 "JBD: Unrecognised features on journal\n");
1097 /* Let the recovery code check whether it needs to recover any
1098 * data from the journal. */
1099 if (journal_recover(journal))
1100 goto recovery_error;
1102 /* OK, we've finished with the dynamic journal bits:
1103 * reinitialise the dynamic contents of the superblock in memory
1104 * and reset them on disk. */
1105 if (journal_reset(journal))
1106 goto recovery_error;
1108 journal->j_flags &= ~JFS_ABORT;
1109 journal->j_flags |= JFS_LOADED;
1113 printk (KERN_WARNING "JBD: recovery failed\n");
1118 * void journal_destroy() - Release a journal_t structure.
1119 * @journal: Journal to act on.
1121 * Release a journal_t structure once it is no longer in use by the
1124 void journal_destroy(journal_t *journal)
1126 /* Wait for the commit thread to wake up and die. */
1127 journal_kill_thread(journal);
1129 /* Force a final log commit */
1130 if (journal->j_running_transaction)
1131 journal_commit_transaction(journal);
1133 /* Force any old transactions to disk */
1135 /* Totally anal locking here... */
1136 spin_lock(&journal->j_list_lock);
1137 while (journal->j_checkpoint_transactions != NULL) {
1138 spin_unlock(&journal->j_list_lock);
1139 log_do_checkpoint(journal);
1140 spin_lock(&journal->j_list_lock);
1143 J_ASSERT(journal->j_running_transaction == NULL);
1144 J_ASSERT(journal->j_committing_transaction == NULL);
1145 J_ASSERT(journal->j_checkpoint_transactions == NULL);
1146 spin_unlock(&journal->j_list_lock);
1148 /* We can now mark the journal as empty. */
1149 journal->j_tail = 0;
1150 journal->j_tail_sequence = ++journal->j_transaction_sequence;
1151 if (journal->j_sb_buffer) {
1152 journal_update_superblock(journal, 1);
1153 brelse(journal->j_sb_buffer);
1156 if (journal->j_inode)
1157 iput(journal->j_inode);
1158 if (journal->j_revoke)
1159 journal_destroy_revoke(journal);
1160 kfree(journal->j_wbuf);
1166 *int journal_check_used_features () - Check if features specified are used.
1167 * @journal: Journal to check.
1168 * @compat: bitmask of compatible features
1169 * @ro: bitmask of features that force read-only mount
1170 * @incompat: bitmask of incompatible features
1172 * Check whether the journal uses all of a given set of
1173 * features. Return true (non-zero) if it does.
1176 int journal_check_used_features (journal_t *journal, unsigned long compat,
1177 unsigned long ro, unsigned long incompat)
1179 journal_superblock_t *sb;
1181 if (!compat && !ro && !incompat)
1183 if (journal->j_format_version == 1)
1186 sb = journal->j_superblock;
1188 if (((be32_to_cpu(sb->s_feature_compat) & compat) == compat) &&
1189 ((be32_to_cpu(sb->s_feature_ro_compat) & ro) == ro) &&
1190 ((be32_to_cpu(sb->s_feature_incompat) & incompat) == incompat))
1197 * int journal_check_available_features() - Check feature set in journalling layer
1198 * @journal: Journal to check.
1199 * @compat: bitmask of compatible features
1200 * @ro: bitmask of features that force read-only mount
1201 * @incompat: bitmask of incompatible features
1203 * Check whether the journaling code supports the use of
1204 * all of a given set of features on this journal. Return true
1205 * (non-zero) if it can. */
1207 int journal_check_available_features (journal_t *journal, unsigned long compat,
1208 unsigned long ro, unsigned long incompat)
1210 journal_superblock_t *sb;
1212 if (!compat && !ro && !incompat)
1215 sb = journal->j_superblock;
1217 /* We can support any known requested features iff the
1218 * superblock is in version 2. Otherwise we fail to support any
1219 * extended sb features. */
1221 if (journal->j_format_version != 2)
1224 if ((compat & JFS_KNOWN_COMPAT_FEATURES) == compat &&
1225 (ro & JFS_KNOWN_ROCOMPAT_FEATURES) == ro &&
1226 (incompat & JFS_KNOWN_INCOMPAT_FEATURES) == incompat)
1233 * int journal_set_features () - Mark a given journal feature in the superblock
1234 * @journal: Journal to act on.
1235 * @compat: bitmask of compatible features
1236 * @ro: bitmask of features that force read-only mount
1237 * @incompat: bitmask of incompatible features
1239 * Mark a given journal feature as present on the
1240 * superblock. Returns true if the requested features could be set.
1244 int journal_set_features (journal_t *journal, unsigned long compat,
1245 unsigned long ro, unsigned long incompat)
1247 journal_superblock_t *sb;
1249 if (journal_check_used_features(journal, compat, ro, incompat))
1252 if (!journal_check_available_features(journal, compat, ro, incompat))
1255 jbd_debug(1, "Setting new features 0x%lx/0x%lx/0x%lx\n",
1256 compat, ro, incompat);
1258 sb = journal->j_superblock;
1260 sb->s_feature_compat |= cpu_to_be32(compat);
1261 sb->s_feature_ro_compat |= cpu_to_be32(ro);
1262 sb->s_feature_incompat |= cpu_to_be32(incompat);
1269 * int journal_update_format () - Update on-disk journal structure.
1270 * @journal: Journal to act on.
1272 * Given an initialised but unloaded journal struct, poke about in the
1273 * on-disk structure to update it to the most recent supported version.
1275 int journal_update_format (journal_t *journal)
1277 journal_superblock_t *sb;
1280 err = journal_get_superblock(journal);
1284 sb = journal->j_superblock;
1286 switch (be32_to_cpu(sb->s_header.h_blocktype)) {
1287 case JFS_SUPERBLOCK_V2:
1289 case JFS_SUPERBLOCK_V1:
1290 return journal_convert_superblock_v1(journal, sb);
1297 static int journal_convert_superblock_v1(journal_t *journal,
1298 journal_superblock_t *sb)
1300 int offset, blocksize;
1301 struct buffer_head *bh;
1304 "JBD: Converting superblock from version 1 to 2.\n");
1306 /* Pre-initialise new fields to zero */
1307 offset = ((char *) &(sb->s_feature_compat)) - ((char *) sb);
1308 blocksize = be32_to_cpu(sb->s_blocksize);
1309 memset(&sb->s_feature_compat, 0, blocksize-offset);
1311 sb->s_nr_users = cpu_to_be32(1);
1312 sb->s_header.h_blocktype = cpu_to_be32(JFS_SUPERBLOCK_V2);
1313 journal->j_format_version = 2;
1315 bh = journal->j_sb_buffer;
1316 BUFFER_TRACE(bh, "marking dirty");
1317 mark_buffer_dirty(bh);
1318 sync_dirty_buffer(bh);
1324 * int journal_flush () - Flush journal
1325 * @journal: Journal to act on.
1327 * Flush all data for a given journal to disk and empty the journal.
1328 * Filesystems can use this when remounting readonly to ensure that
1329 * recovery does not need to happen on remount.
1332 int journal_flush(journal_t *journal)
1335 transaction_t *transaction = NULL;
1336 unsigned long old_tail;
1338 spin_lock(&journal->j_state_lock);
1340 /* Force everything buffered to the log... */
1341 if (journal->j_running_transaction) {
1342 transaction = journal->j_running_transaction;
1343 __log_start_commit(journal, transaction->t_tid);
1344 } else if (journal->j_committing_transaction)
1345 transaction = journal->j_committing_transaction;
1347 /* Wait for the log commit to complete... */
1349 tid_t tid = transaction->t_tid;
1351 spin_unlock(&journal->j_state_lock);
1352 log_wait_commit(journal, tid);
1354 spin_unlock(&journal->j_state_lock);
1357 /* ...and flush everything in the log out to disk. */
1358 spin_lock(&journal->j_list_lock);
1359 while (!err && journal->j_checkpoint_transactions != NULL) {
1360 spin_unlock(&journal->j_list_lock);
1361 err = log_do_checkpoint(journal);
1362 spin_lock(&journal->j_list_lock);
1364 spin_unlock(&journal->j_list_lock);
1365 cleanup_journal_tail(journal);
1367 /* Finally, mark the journal as really needing no recovery.
1368 * This sets s_start==0 in the underlying superblock, which is
1369 * the magic code for a fully-recovered superblock. Any future
1370 * commits of data to the journal will restore the current
1372 spin_lock(&journal->j_state_lock);
1373 old_tail = journal->j_tail;
1374 journal->j_tail = 0;
1375 spin_unlock(&journal->j_state_lock);
1376 journal_update_superblock(journal, 1);
1377 spin_lock(&journal->j_state_lock);
1378 journal->j_tail = old_tail;
1380 J_ASSERT(!journal->j_running_transaction);
1381 J_ASSERT(!journal->j_committing_transaction);
1382 J_ASSERT(!journal->j_checkpoint_transactions);
1383 J_ASSERT(journal->j_head == journal->j_tail);
1384 J_ASSERT(journal->j_tail_sequence == journal->j_transaction_sequence);
1385 spin_unlock(&journal->j_state_lock);
1390 * int journal_wipe() - Wipe journal contents
1391 * @journal: Journal to act on.
1392 * @write: flag (see below)
1394 * Wipe out all of the contents of a journal, safely. This will produce
1395 * a warning if the journal contains any valid recovery information.
1396 * Must be called between journal_init_*() and journal_load().
1398 * If 'write' is non-zero, then we wipe out the journal on disk; otherwise
1399 * we merely suppress recovery.
1402 int journal_wipe(journal_t *journal, int write)
1404 journal_superblock_t *sb;
1407 J_ASSERT (!(journal->j_flags & JFS_LOADED));
1409 err = load_superblock(journal);
1413 sb = journal->j_superblock;
1415 if (!journal->j_tail)
1418 printk (KERN_WARNING "JBD: %s recovery information on journal\n",
1419 write ? "Clearing" : "Ignoring");
1421 err = journal_skip_recovery(journal);
1423 journal_update_superblock(journal, 1);
1430 * journal_dev_name: format a character string to describe on what
1431 * device this journal is present.
1434 static const char *journal_dev_name(journal_t *journal, char *buffer)
1436 struct block_device *bdev;
1438 if (journal->j_inode)
1439 bdev = journal->j_inode->i_sb->s_bdev;
1441 bdev = journal->j_dev;
1443 return bdevname(bdev, buffer);
1447 * Journal abort has very specific semantics, which we describe
1448 * for journal abort.
1450 * Two internal function, which provide abort to te jbd layer
1455 * Quick version for internal journal use (doesn't lock the journal).
1456 * Aborts hard --- we mark the abort as occurred, but do _nothing_ else,
1457 * and don't attempt to make any other journal updates.
1459 void __journal_abort_hard(journal_t *journal)
1461 transaction_t *transaction;
1462 char b[BDEVNAME_SIZE];
1464 if (journal->j_flags & JFS_ABORT)
1467 printk(KERN_ERR "Aborting journal on device %s.\n",
1468 journal_dev_name(journal, b));
1470 spin_lock(&journal->j_state_lock);
1471 journal->j_flags |= JFS_ABORT;
1472 transaction = journal->j_running_transaction;
1474 __log_start_commit(journal, transaction->t_tid);
1475 spin_unlock(&journal->j_state_lock);
1478 /* Soft abort: record the abort error status in the journal superblock,
1479 * but don't do any other IO. */
1480 static void __journal_abort_soft (journal_t *journal, int errno)
1482 if (journal->j_flags & JFS_ABORT)
1485 if (!journal->j_errno)
1486 journal->j_errno = errno;
1488 __journal_abort_hard(journal);
1491 journal_update_superblock(journal, 1);
1495 * void journal_abort () - Shutdown the journal immediately.
1496 * @journal: the journal to shutdown.
1497 * @errno: an error number to record in the journal indicating
1498 * the reason for the shutdown.
1500 * Perform a complete, immediate shutdown of the ENTIRE
1501 * journal (not of a single transaction). This operation cannot be
1502 * undone without closing and reopening the journal.
1504 * The journal_abort function is intended to support higher level error
1505 * recovery mechanisms such as the ext2/ext3 remount-readonly error
1508 * Journal abort has very specific semantics. Any existing dirty,
1509 * unjournaled buffers in the main filesystem will still be written to
1510 * disk by bdflush, but the journaling mechanism will be suspended
1511 * immediately and no further transaction commits will be honoured.
1513 * Any dirty, journaled buffers will be written back to disk without
1514 * hitting the journal. Atomicity cannot be guaranteed on an aborted
1515 * filesystem, but we _do_ attempt to leave as much data as possible
1516 * behind for fsck to use for cleanup.
1518 * Any attempt to get a new transaction handle on a journal which is in
1519 * ABORT state will just result in an -EROFS error return. A
1520 * journal_stop on an existing handle will return -EIO if we have
1521 * entered abort state during the update.
1523 * Recursive transactions are not disturbed by journal abort until the
1524 * final journal_stop, which will receive the -EIO error.
1526 * Finally, the journal_abort call allows the caller to supply an errno
1527 * which will be recorded (if possible) in the journal superblock. This
1528 * allows a client to record failure conditions in the middle of a
1529 * transaction without having to complete the transaction to record the
1530 * failure to disk. ext3_error, for example, now uses this
1533 * Errors which originate from within the journaling layer will NOT
1534 * supply an errno; a null errno implies that absolutely no further
1535 * writes are done to the journal (unless there are any already in
1540 void journal_abort(journal_t *journal, int errno)
1542 __journal_abort_soft(journal, errno);
1546 * int journal_errno () - returns the journal's error state.
1547 * @journal: journal to examine.
1549 * This is the errno numbet set with journal_abort(), the last
1550 * time the journal was mounted - if the journal was stopped
1551 * without calling abort this will be 0.
1553 * If the journal has been aborted on this mount time -EROFS will
1556 int journal_errno(journal_t *journal)
1560 spin_lock(&journal->j_state_lock);
1561 if (journal->j_flags & JFS_ABORT)
1564 err = journal->j_errno;
1565 spin_unlock(&journal->j_state_lock);
1570 * int journal_clear_err () - clears the journal's error state
1571 * @journal: journal to act on.
1573 * An error must be cleared or Acked to take a FS out of readonly
1576 int journal_clear_err(journal_t *journal)
1580 spin_lock(&journal->j_state_lock);
1581 if (journal->j_flags & JFS_ABORT)
1584 journal->j_errno = 0;
1585 spin_unlock(&journal->j_state_lock);
1590 * void journal_ack_err() - Ack journal err.
1591 * @journal: journal to act on.
1593 * An error must be cleared or Acked to take a FS out of readonly
1596 void journal_ack_err(journal_t *journal)
1598 spin_lock(&journal->j_state_lock);
1599 if (journal->j_errno)
1600 journal->j_flags |= JFS_ACK_ERR;
1601 spin_unlock(&journal->j_state_lock);
1604 int journal_blocks_per_page(struct inode *inode)
1606 return 1 << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);
1610 * Simple support for retrying memory allocations. Introduced to help to
1611 * debug different VM deadlock avoidance strategies.
1613 void * __jbd_kmalloc (const char *where, size_t size, gfp_t flags, int retry)
1615 return kmalloc(size, flags | (retry ? __GFP_NOFAIL : 0));
1619 * Journal_head storage management
1621 static struct kmem_cache *journal_head_cache;
1622 #ifdef CONFIG_JBD_DEBUG
1623 static atomic_t nr_journal_heads = ATOMIC_INIT(0);
1626 static int journal_init_journal_head_cache(void)
1630 J_ASSERT(journal_head_cache == 0);
1631 journal_head_cache = kmem_cache_create("journal_head",
1632 sizeof(struct journal_head),
1634 SLAB_TEMPORARY, /* flags */
1637 if (journal_head_cache == 0) {
1639 printk(KERN_EMERG "JBD: no memory for journal_head cache\n");
1644 static void journal_destroy_journal_head_cache(void)
1646 J_ASSERT(journal_head_cache != NULL);
1647 kmem_cache_destroy(journal_head_cache);
1648 journal_head_cache = NULL;
1652 * journal_head splicing and dicing
1654 static struct journal_head *journal_alloc_journal_head(void)
1656 struct journal_head *ret;
1657 static unsigned long last_warning;
1659 #ifdef CONFIG_JBD_DEBUG
1660 atomic_inc(&nr_journal_heads);
1662 ret = kmem_cache_alloc(journal_head_cache, GFP_NOFS);
1664 jbd_debug(1, "out of memory for journal_head\n");
1665 if (time_after(jiffies, last_warning + 5*HZ)) {
1666 printk(KERN_NOTICE "ENOMEM in %s, retrying.\n",
1668 last_warning = jiffies;
1672 ret = kmem_cache_alloc(journal_head_cache, GFP_NOFS);
1678 static void journal_free_journal_head(struct journal_head *jh)
1680 #ifdef CONFIG_JBD_DEBUG
1681 atomic_dec(&nr_journal_heads);
1682 memset(jh, JBD_POISON_FREE, sizeof(*jh));
1684 kmem_cache_free(journal_head_cache, jh);
1688 * A journal_head is attached to a buffer_head whenever JBD has an
1689 * interest in the buffer.
1691 * Whenever a buffer has an attached journal_head, its ->b_state:BH_JBD bit
1692 * is set. This bit is tested in core kernel code where we need to take
1693 * JBD-specific actions. Testing the zeroness of ->b_private is not reliable
1696 * When a buffer has its BH_JBD bit set, its ->b_count is elevated by one.
1698 * When a buffer has its BH_JBD bit set it is immune from being released by
1699 * core kernel code, mainly via ->b_count.
1701 * A journal_head may be detached from its buffer_head when the journal_head's
1702 * b_transaction, b_cp_transaction and b_next_transaction pointers are NULL.
1703 * Various places in JBD call journal_remove_journal_head() to indicate that the
1704 * journal_head can be dropped if needed.
1706 * Various places in the kernel want to attach a journal_head to a buffer_head
1707 * _before_ attaching the journal_head to a transaction. To protect the
1708 * journal_head in this situation, journal_add_journal_head elevates the
1709 * journal_head's b_jcount refcount by one. The caller must call
1710 * journal_put_journal_head() to undo this.
1712 * So the typical usage would be:
1714 * (Attach a journal_head if needed. Increments b_jcount)
1715 * struct journal_head *jh = journal_add_journal_head(bh);
1717 * jh->b_transaction = xxx;
1718 * journal_put_journal_head(jh);
1720 * Now, the journal_head's b_jcount is zero, but it is safe from being released
1721 * because it has a non-zero b_transaction.
1725 * Give a buffer_head a journal_head.
1727 * Doesn't need the journal lock.
1730 struct journal_head *journal_add_journal_head(struct buffer_head *bh)
1732 struct journal_head *jh;
1733 struct journal_head *new_jh = NULL;
1736 if (!buffer_jbd(bh)) {
1737 new_jh = journal_alloc_journal_head();
1738 memset(new_jh, 0, sizeof(*new_jh));
1741 jbd_lock_bh_journal_head(bh);
1742 if (buffer_jbd(bh)) {
1746 (atomic_read(&bh->b_count) > 0) ||
1747 (bh->b_page && bh->b_page->mapping));
1750 jbd_unlock_bh_journal_head(bh);
1755 new_jh = NULL; /* We consumed it */
1760 BUFFER_TRACE(bh, "added journal_head");
1763 jbd_unlock_bh_journal_head(bh);
1765 journal_free_journal_head(new_jh);
1766 return bh->b_private;
1770 * Grab a ref against this buffer_head's journal_head. If it ended up not
1771 * having a journal_head, return NULL
1773 struct journal_head *journal_grab_journal_head(struct buffer_head *bh)
1775 struct journal_head *jh = NULL;
1777 jbd_lock_bh_journal_head(bh);
1778 if (buffer_jbd(bh)) {
1782 jbd_unlock_bh_journal_head(bh);
1786 static void __journal_remove_journal_head(struct buffer_head *bh)
1788 struct journal_head *jh = bh2jh(bh);
1790 J_ASSERT_JH(jh, jh->b_jcount >= 0);
1793 if (jh->b_jcount == 0) {
1794 if (jh->b_transaction == NULL &&
1795 jh->b_next_transaction == NULL &&
1796 jh->b_cp_transaction == NULL) {
1797 J_ASSERT_JH(jh, jh->b_jlist == BJ_None);
1798 J_ASSERT_BH(bh, buffer_jbd(bh));
1799 J_ASSERT_BH(bh, jh2bh(jh) == bh);
1800 BUFFER_TRACE(bh, "remove journal_head");
1801 if (jh->b_frozen_data) {
1802 printk(KERN_WARNING "%s: freeing "
1805 jbd_free(jh->b_frozen_data, bh->b_size);
1807 if (jh->b_committed_data) {
1808 printk(KERN_WARNING "%s: freeing "
1809 "b_committed_data\n",
1811 jbd_free(jh->b_committed_data, bh->b_size);
1813 bh->b_private = NULL;
1814 jh->b_bh = NULL; /* debug, really */
1815 clear_buffer_jbd(bh);
1817 journal_free_journal_head(jh);
1819 BUFFER_TRACE(bh, "journal_head was locked");
1825 * journal_remove_journal_head(): if the buffer isn't attached to a transaction
1826 * and has a zero b_jcount then remove and release its journal_head. If we did
1827 * see that the buffer is not used by any transaction we also "logically"
1828 * decrement ->b_count.
1830 * We in fact take an additional increment on ->b_count as a convenience,
1831 * because the caller usually wants to do additional things with the bh
1832 * after calling here.
1833 * The caller of journal_remove_journal_head() *must* run __brelse(bh) at some
1834 * time. Once the caller has run __brelse(), the buffer is eligible for
1835 * reaping by try_to_free_buffers().
1837 void journal_remove_journal_head(struct buffer_head *bh)
1839 jbd_lock_bh_journal_head(bh);
1840 __journal_remove_journal_head(bh);
1841 jbd_unlock_bh_journal_head(bh);
1845 * Drop a reference on the passed journal_head. If it fell to zero then try to
1846 * release the journal_head from the buffer_head.
1848 void journal_put_journal_head(struct journal_head *jh)
1850 struct buffer_head *bh = jh2bh(jh);
1852 jbd_lock_bh_journal_head(bh);
1853 J_ASSERT_JH(jh, jh->b_jcount > 0);
1855 if (!jh->b_jcount && !jh->b_transaction) {
1856 __journal_remove_journal_head(bh);
1859 jbd_unlock_bh_journal_head(bh);
1865 #if defined(CONFIG_JBD_DEBUG)
1866 int journal_enable_debug;
1867 EXPORT_SYMBOL(journal_enable_debug);
1870 #if defined(CONFIG_JBD_DEBUG) && defined(CONFIG_PROC_FS)
1872 static struct proc_dir_entry *proc_jbd_debug;
1874 static int read_jbd_debug(char *page, char **start, off_t off,
1875 int count, int *eof, void *data)
1879 ret = sprintf(page + off, "%d\n", journal_enable_debug);
1884 static int write_jbd_debug(struct file *file, const char __user *buffer,
1885 unsigned long count, void *data)
1889 if (count > ARRAY_SIZE(buf) - 1)
1890 count = ARRAY_SIZE(buf) - 1;
1891 if (copy_from_user(buf, buffer, count))
1893 buf[ARRAY_SIZE(buf) - 1] = '\0';
1894 journal_enable_debug = simple_strtoul(buf, NULL, 10);
1898 #define JBD_PROC_NAME "sys/fs/jbd-debug"
1900 static void __init create_jbd_proc_entry(void)
1902 proc_jbd_debug = create_proc_entry(JBD_PROC_NAME, 0644, NULL);
1903 if (proc_jbd_debug) {
1904 /* Why is this so hard? */
1905 proc_jbd_debug->read_proc = read_jbd_debug;
1906 proc_jbd_debug->write_proc = write_jbd_debug;
1910 static void __exit remove_jbd_proc_entry(void)
1913 remove_proc_entry(JBD_PROC_NAME, NULL);
1918 #define create_jbd_proc_entry() do {} while (0)
1919 #define remove_jbd_proc_entry() do {} while (0)
1923 struct kmem_cache *jbd_handle_cache;
1925 static int __init journal_init_handle_cache(void)
1927 jbd_handle_cache = kmem_cache_create("journal_handle",
1930 SLAB_TEMPORARY, /* flags */
1932 if (jbd_handle_cache == NULL) {
1933 printk(KERN_EMERG "JBD: failed to create handle cache\n");
1939 static void journal_destroy_handle_cache(void)
1941 if (jbd_handle_cache)
1942 kmem_cache_destroy(jbd_handle_cache);
1946 * Module startup and shutdown
1949 static int __init journal_init_caches(void)
1953 ret = journal_init_revoke_caches();
1955 ret = journal_init_journal_head_cache();
1957 ret = journal_init_handle_cache();
1961 static void journal_destroy_caches(void)
1963 journal_destroy_revoke_caches();
1964 journal_destroy_journal_head_cache();
1965 journal_destroy_handle_cache();
1968 static int __init journal_init(void)
1972 BUILD_BUG_ON(sizeof(struct journal_superblock_s) != 1024);
1974 ret = journal_init_caches();
1976 journal_destroy_caches();
1977 create_jbd_proc_entry();
1981 static void __exit journal_exit(void)
1983 #ifdef CONFIG_JBD_DEBUG
1984 int n = atomic_read(&nr_journal_heads);
1986 printk(KERN_EMERG "JBD: leaked %d journal_heads!\n", n);
1988 remove_jbd_proc_entry();
1989 journal_destroy_caches();
1992 MODULE_LICENSE("GPL");
1993 module_init(journal_init);
1994 module_exit(journal_exit);