2 * linux/fs/transaction.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 transaction handling code; part of the ext2fs
15 * This file manages transactions (compound commits managed by the
16 * journaling code) and handles (individual atomic operations by the
20 #include <linux/time.h>
22 #include <linux/jbd.h>
23 #include <linux/errno.h>
24 #include <linux/slab.h>
25 #include <linux/timer.h>
26 #include <linux/smp_lock.h>
28 #include <linux/highmem.h>
31 * get_transaction: obtain a new transaction_t object.
33 * Simply allocate and initialise a new transaction. Create it in
34 * RUNNING state and add it to the current journal (which should not
35 * have an existing running transaction: we only make a new transaction
36 * once we have started to commit the old one).
39 * The journal MUST be locked. We don't perform atomic mallocs on the
40 * new transaction and we can't block without protecting against other
41 * processes trying to touch the journal while it is in transition.
43 * Called under j_state_lock
46 static transaction_t *
47 get_transaction(journal_t *journal, transaction_t *transaction)
49 transaction->t_journal = journal;
50 transaction->t_state = T_RUNNING;
51 transaction->t_tid = journal->j_transaction_sequence++;
52 transaction->t_expires = jiffies + journal->j_commit_interval;
53 spin_lock_init(&transaction->t_handle_lock);
55 /* Set up the commit timer for the new transaction. */
56 journal->j_commit_timer->expires = transaction->t_expires;
57 add_timer(journal->j_commit_timer);
59 J_ASSERT(journal->j_running_transaction == NULL);
60 journal->j_running_transaction = transaction;
68 * A handle_t is an object which represents a single atomic update to a
69 * filesystem, and which tracks all of the modifications which form part
74 * start_this_handle: Given a handle, deal with any locking or stalling
75 * needed to make sure that there is enough journal space for the handle
76 * to begin. Attach the handle to a transaction and set up the
77 * transaction's buffer credits.
80 static int start_this_handle(journal_t *journal, handle_t *handle)
82 transaction_t *transaction;
84 int nblocks = handle->h_buffer_credits;
85 transaction_t *new_transaction = NULL;
88 if (nblocks > journal->j_max_transaction_buffers) {
89 printk(KERN_ERR "JBD: %s wants too many credits (%d > %d)\n",
90 current->comm, nblocks,
91 journal->j_max_transaction_buffers);
97 if (!journal->j_running_transaction) {
98 new_transaction = jbd_kmalloc(sizeof(*new_transaction),
100 if (!new_transaction) {
104 memset(new_transaction, 0, sizeof(*new_transaction));
107 jbd_debug(3, "New handle %p going live.\n", handle);
112 * We need to hold j_state_lock until t_updates has been incremented,
113 * for proper journal barrier handling
115 spin_lock(&journal->j_state_lock);
117 if (is_journal_aborted(journal) ||
118 (journal->j_errno != 0 && !(journal->j_flags & JFS_ACK_ERR))) {
119 spin_unlock(&journal->j_state_lock);
124 /* Wait on the journal's transaction barrier if necessary */
125 if (journal->j_barrier_count) {
126 spin_unlock(&journal->j_state_lock);
127 wait_event(journal->j_wait_transaction_locked,
128 journal->j_barrier_count == 0);
132 if (!journal->j_running_transaction) {
133 if (!new_transaction) {
134 spin_unlock(&journal->j_state_lock);
135 goto alloc_transaction;
137 get_transaction(journal, new_transaction);
138 new_transaction = NULL;
141 transaction = journal->j_running_transaction;
144 * If the current transaction is locked down for commit, wait for the
145 * lock to be released.
147 if (transaction->t_state == T_LOCKED) {
150 prepare_to_wait(&journal->j_wait_transaction_locked,
151 &wait, TASK_UNINTERRUPTIBLE);
152 spin_unlock(&journal->j_state_lock);
154 finish_wait(&journal->j_wait_transaction_locked, &wait);
159 * If there is not enough space left in the log to write all potential
160 * buffers requested by this operation, we need to stall pending a log
161 * checkpoint to free some more log space.
163 spin_lock(&transaction->t_handle_lock);
164 needed = transaction->t_outstanding_credits + nblocks;
166 if (needed > journal->j_max_transaction_buffers) {
168 * If the current transaction is already too large, then start
169 * to commit it: we can then go back and attach this handle to
174 jbd_debug(2, "Handle %p starting new commit...\n", handle);
175 spin_unlock(&transaction->t_handle_lock);
176 prepare_to_wait(&journal->j_wait_transaction_locked, &wait,
177 TASK_UNINTERRUPTIBLE);
178 __log_start_commit(journal, transaction->t_tid);
179 spin_unlock(&journal->j_state_lock);
181 finish_wait(&journal->j_wait_transaction_locked, &wait);
186 * The commit code assumes that it can get enough log space
187 * without forcing a checkpoint. This is *critical* for
188 * correctness: a checkpoint of a buffer which is also
189 * associated with a committing transaction creates a deadlock,
190 * so commit simply cannot force through checkpoints.
192 * We must therefore ensure the necessary space in the journal
193 * *before* starting to dirty potentially checkpointed buffers
194 * in the new transaction.
196 * The worst part is, any transaction currently committing can
197 * reduce the free space arbitrarily. Be careful to account for
198 * those buffers when checkpointing.
202 * @@@ AKPM: This seems rather over-defensive. We're giving commit
203 * a _lot_ of headroom: 1/4 of the journal plus the size of
204 * the committing transaction. Really, we only need to give it
205 * committing_transaction->t_outstanding_credits plus "enough" for
206 * the log control blocks.
207 * Also, this test is inconsitent with the matching one in
210 if (__log_space_left(journal) < jbd_space_needed(journal)) {
211 jbd_debug(2, "Handle %p waiting for checkpoint...\n", handle);
212 spin_unlock(&transaction->t_handle_lock);
213 __log_wait_for_space(journal);
217 /* OK, account for the buffers that this operation expects to
218 * use and add the handle to the running transaction. */
220 handle->h_transaction = transaction;
221 transaction->t_outstanding_credits += nblocks;
222 transaction->t_updates++;
223 transaction->t_handle_count++;
224 jbd_debug(4, "Handle %p given %d credits (total %d, free %d)\n",
225 handle, nblocks, transaction->t_outstanding_credits,
226 __log_space_left(journal));
227 spin_unlock(&transaction->t_handle_lock);
228 spin_unlock(&journal->j_state_lock);
231 kfree(new_transaction);
235 /* Allocate a new handle. This should probably be in a slab... */
236 static handle_t *new_handle(int nblocks)
238 handle_t *handle = jbd_alloc_handle(GFP_NOFS);
241 memset(handle, 0, sizeof(*handle));
242 handle->h_buffer_credits = nblocks;
249 * handle_t *journal_start() - Obtain a new handle.
250 * @journal: Journal to start transaction on.
251 * @nblocks: number of block buffer we might modify
253 * We make sure that the transaction can guarantee at least nblocks of
254 * modified buffers in the log. We block until the log can guarantee
257 * This function is visible to journal users (like ext3fs), so is not
258 * called with the journal already locked.
260 * Return a pointer to a newly allocated handle, or NULL on failure
262 handle_t *journal_start(journal_t *journal, int nblocks)
264 handle_t *handle = journal_current_handle();
268 return ERR_PTR(-EROFS);
271 J_ASSERT(handle->h_transaction->t_journal == journal);
276 handle = new_handle(nblocks);
278 return ERR_PTR(-ENOMEM);
280 current->journal_info = handle;
282 err = start_this_handle(journal, handle);
284 jbd_free_handle(handle);
285 current->journal_info = NULL;
286 handle = ERR_PTR(err);
292 * int journal_extend() - extend buffer credits.
293 * @handle: handle to 'extend'
294 * @nblocks: nr blocks to try to extend by.
296 * Some transactions, such as large extends and truncates, can be done
297 * atomically all at once or in several stages. The operation requests
298 * a credit for a number of buffer modications in advance, but can
299 * extend its credit if it needs more.
301 * journal_extend tries to give the running handle more buffer credits.
302 * It does not guarantee that allocation - this is a best-effort only.
303 * The calling process MUST be able to deal cleanly with a failure to
306 * Return 0 on success, non-zero on failure.
308 * return code < 0 implies an error
309 * return code > 0 implies normal transaction-full status.
311 int journal_extend(handle_t *handle, int nblocks)
313 transaction_t *transaction = handle->h_transaction;
314 journal_t *journal = transaction->t_journal;
319 if (is_handle_aborted(handle))
324 spin_lock(&journal->j_state_lock);
326 /* Don't extend a locked-down transaction! */
327 if (handle->h_transaction->t_state != T_RUNNING) {
328 jbd_debug(3, "denied handle %p %d blocks: "
329 "transaction not running\n", handle, nblocks);
333 spin_lock(&transaction->t_handle_lock);
334 wanted = transaction->t_outstanding_credits + nblocks;
336 if (wanted > journal->j_max_transaction_buffers) {
337 jbd_debug(3, "denied handle %p %d blocks: "
338 "transaction too large\n", handle, nblocks);
342 if (wanted > __log_space_left(journal)) {
343 jbd_debug(3, "denied handle %p %d blocks: "
344 "insufficient log space\n", handle, nblocks);
348 handle->h_buffer_credits += nblocks;
349 transaction->t_outstanding_credits += nblocks;
352 jbd_debug(3, "extended handle %p by %d\n", handle, nblocks);
354 spin_unlock(&transaction->t_handle_lock);
356 spin_unlock(&journal->j_state_lock);
363 * int journal_restart() - restart a handle .
364 * @handle: handle to restart
365 * @nblocks: nr credits requested
367 * Restart a handle for a multi-transaction filesystem
370 * If the journal_extend() call above fails to grant new buffer credits
371 * to a running handle, a call to journal_restart will commit the
372 * handle's transaction so far and reattach the handle to a new
373 * transaction capabable of guaranteeing the requested number of
377 int journal_restart(handle_t *handle, int nblocks)
379 transaction_t *transaction = handle->h_transaction;
380 journal_t *journal = transaction->t_journal;
383 /* If we've had an abort of any type, don't even think about
384 * actually doing the restart! */
385 if (is_handle_aborted(handle))
389 * First unlink the handle from its current transaction, and start the
392 J_ASSERT(transaction->t_updates > 0);
393 J_ASSERT(journal_current_handle() == handle);
395 spin_lock(&journal->j_state_lock);
396 spin_lock(&transaction->t_handle_lock);
397 transaction->t_outstanding_credits -= handle->h_buffer_credits;
398 transaction->t_updates--;
400 if (!transaction->t_updates)
401 wake_up(&journal->j_wait_updates);
402 spin_unlock(&transaction->t_handle_lock);
404 jbd_debug(2, "restarting handle %p\n", handle);
405 __log_start_commit(journal, transaction->t_tid);
406 spin_unlock(&journal->j_state_lock);
408 handle->h_buffer_credits = nblocks;
409 ret = start_this_handle(journal, handle);
415 * void journal_lock_updates () - establish a transaction barrier.
416 * @journal: Journal to establish a barrier on.
418 * This locks out any further updates from being started, and blocks
419 * until all existing updates have completed, returning only once the
420 * journal is in a quiescent state with no updates running.
422 * The journal lock should not be held on entry.
424 void journal_lock_updates(journal_t *journal)
428 spin_lock(&journal->j_state_lock);
429 ++journal->j_barrier_count;
431 /* Wait until there are no running updates */
433 transaction_t *transaction = journal->j_running_transaction;
438 spin_lock(&transaction->t_handle_lock);
439 if (!transaction->t_updates) {
440 spin_unlock(&transaction->t_handle_lock);
443 prepare_to_wait(&journal->j_wait_updates, &wait,
444 TASK_UNINTERRUPTIBLE);
445 spin_unlock(&transaction->t_handle_lock);
446 spin_unlock(&journal->j_state_lock);
448 finish_wait(&journal->j_wait_updates, &wait);
449 spin_lock(&journal->j_state_lock);
451 spin_unlock(&journal->j_state_lock);
454 * We have now established a barrier against other normal updates, but
455 * we also need to barrier against other journal_lock_updates() calls
456 * to make sure that we serialise special journal-locked operations
459 down(&journal->j_barrier);
463 * void journal_unlock_updates (journal_t* journal) - release barrier
464 * @journal: Journal to release the barrier on.
466 * Release a transaction barrier obtained with journal_lock_updates().
468 * Should be called without the journal lock held.
470 void journal_unlock_updates (journal_t *journal)
472 J_ASSERT(journal->j_barrier_count != 0);
474 up(&journal->j_barrier);
475 spin_lock(&journal->j_state_lock);
476 --journal->j_barrier_count;
477 spin_unlock(&journal->j_state_lock);
478 wake_up(&journal->j_wait_transaction_locked);
482 * Report any unexpected dirty buffers which turn up. Normally those
483 * indicate an error, but they can occur if the user is running (say)
484 * tune2fs to modify the live filesystem, so we need the option of
485 * continuing as gracefully as possible. #
487 * The caller should already hold the journal lock and
488 * j_list_lock spinlock: most callers will need those anyway
489 * in order to probe the buffer's journaling state safely.
491 static void jbd_unexpected_dirty_buffer(struct journal_head *jh)
493 struct buffer_head *bh = jh2bh(jh);
496 if (buffer_dirty(bh)) {
497 /* If this buffer is one which might reasonably be dirty
498 * --- ie. data, or not part of this journal --- then
499 * we're OK to leave it alone, but otherwise we need to
500 * move the dirty bit to the journal's own internal
504 if (jlist == BJ_Metadata || jlist == BJ_Reserved ||
505 jlist == BJ_Shadow || jlist == BJ_Forget) {
506 if (test_clear_buffer_dirty(jh2bh(jh))) {
507 set_bit(BH_JBDDirty, &jh2bh(jh)->b_state);
514 * If the buffer is already part of the current transaction, then there
515 * is nothing we need to do. If it is already part of a prior
516 * transaction which we are still committing to disk, then we need to
517 * make sure that we do not overwrite the old copy: we do copy-out to
518 * preserve the copy going to disk. We also account the buffer against
519 * the handle's metadata buffer credits (unless the buffer is already
520 * part of the transaction, that is).
524 do_get_write_access(handle_t *handle, struct journal_head *jh,
525 int force_copy, int *credits)
527 struct buffer_head *bh;
528 transaction_t *transaction;
531 char *frozen_buffer = NULL;
534 if (is_handle_aborted(handle))
537 transaction = handle->h_transaction;
538 journal = transaction->t_journal;
540 jbd_debug(5, "buffer_head %p, force_copy %d\n", jh, force_copy);
542 JBUFFER_TRACE(jh, "entry");
546 /* @@@ Need to check for errors here at some point. */
549 jbd_lock_bh_state(bh);
551 /* We now hold the buffer lock so it is safe to query the buffer
552 * state. Is the buffer dirty?
554 * If so, there are two possibilities. The buffer may be
555 * non-journaled, and undergoing a quite legitimate writeback.
556 * Otherwise, it is journaled, and we don't expect dirty buffers
557 * in that state (the buffers should be marked JBD_Dirty
558 * instead.) So either the IO is being done under our own
559 * control and this is a bug, or it's a third party IO such as
560 * dump(8) (which may leave the buffer scheduled for read ---
561 * ie. locked but not dirty) or tune2fs (which may actually have
562 * the buffer dirtied, ugh.) */
564 if (buffer_dirty(bh)) {
566 * First question: is this buffer already part of the current
567 * transaction or the existing committing transaction?
569 if (jh->b_transaction) {
571 jh->b_transaction == transaction ||
573 journal->j_committing_transaction);
574 if (jh->b_next_transaction)
575 J_ASSERT_JH(jh, jh->b_next_transaction ==
577 JBUFFER_TRACE(jh, "Unexpected dirty buffer");
578 jbd_unexpected_dirty_buffer(jh);
585 if (is_handle_aborted(handle)) {
586 jbd_unlock_bh_state(bh);
592 * The buffer is already part of this transaction if b_transaction or
593 * b_next_transaction points to it
595 if (jh->b_transaction == transaction ||
596 jh->b_next_transaction == transaction)
600 * If there is already a copy-out version of this buffer, then we don't
601 * need to make another one
603 if (jh->b_frozen_data) {
604 JBUFFER_TRACE(jh, "has frozen data");
605 J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
606 jh->b_next_transaction = transaction;
608 J_ASSERT_JH(jh, handle->h_buffer_credits > 0);
609 handle->h_buffer_credits--;
615 /* Is there data here we need to preserve? */
617 if (jh->b_transaction && jh->b_transaction != transaction) {
618 JBUFFER_TRACE(jh, "owned by older transaction");
619 J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
620 J_ASSERT_JH(jh, jh->b_transaction ==
621 journal->j_committing_transaction);
623 /* There is one case we have to be very careful about.
624 * If the committing transaction is currently writing
625 * this buffer out to disk and has NOT made a copy-out,
626 * then we cannot modify the buffer contents at all
627 * right now. The essence of copy-out is that it is the
628 * extra copy, not the primary copy, which gets
629 * journaled. If the primary copy is already going to
630 * disk then we cannot do copy-out here. */
632 if (jh->b_jlist == BJ_Shadow) {
633 DEFINE_WAIT_BIT(wait, &bh->b_state, BH_Unshadow);
634 wait_queue_head_t *wqh;
636 wqh = bit_waitqueue(&bh->b_state, BH_Unshadow);
638 JBUFFER_TRACE(jh, "on shadow: sleep");
639 jbd_unlock_bh_state(bh);
640 /* commit wakes up all shadow buffers after IO */
642 prepare_to_wait(wqh, &wait.wait,
643 TASK_UNINTERRUPTIBLE);
644 if (jh->b_jlist != BJ_Shadow)
648 finish_wait(wqh, &wait.wait);
652 /* Only do the copy if the currently-owning transaction
653 * still needs it. If it is on the Forget list, the
654 * committing transaction is past that stage. The
655 * buffer had better remain locked during the kmalloc,
656 * but that should be true --- we hold the journal lock
657 * still and the buffer is already on the BUF_JOURNAL
658 * list so won't be flushed.
660 * Subtle point, though: if this is a get_undo_access,
661 * then we will be relying on the frozen_data to contain
662 * the new value of the committed_data record after the
663 * transaction, so we HAVE to force the frozen_data copy
666 if (jh->b_jlist != BJ_Forget || force_copy) {
667 JBUFFER_TRACE(jh, "generate frozen data");
668 if (!frozen_buffer) {
669 JBUFFER_TRACE(jh, "allocate memory for buffer");
670 jbd_unlock_bh_state(bh);
671 frozen_buffer = jbd_kmalloc(jh2bh(jh)->b_size,
673 if (!frozen_buffer) {
675 "%s: OOM for frozen_buffer\n",
677 JBUFFER_TRACE(jh, "oom!");
679 jbd_lock_bh_state(bh);
684 jh->b_frozen_data = frozen_buffer;
685 frozen_buffer = NULL;
688 jh->b_next_transaction = transaction;
691 J_ASSERT(handle->h_buffer_credits > 0);
692 handle->h_buffer_credits--;
697 * Finally, if the buffer is not journaled right now, we need to make
698 * sure it doesn't get written to disk before the caller actually
699 * commits the new data
701 if (!jh->b_transaction) {
702 JBUFFER_TRACE(jh, "no transaction");
703 J_ASSERT_JH(jh, !jh->b_next_transaction);
704 jh->b_transaction = transaction;
705 JBUFFER_TRACE(jh, "file as BJ_Reserved");
706 spin_lock(&journal->j_list_lock);
707 __journal_file_buffer(jh, transaction, BJ_Reserved);
708 spin_unlock(&journal->j_list_lock);
717 J_EXPECT_JH(jh, buffer_uptodate(jh2bh(jh)),
718 "Possible IO failure.\n");
719 page = jh2bh(jh)->b_page;
720 offset = ((unsigned long) jh2bh(jh)->b_data) & ~PAGE_MASK;
721 source = kmap_atomic(page, KM_USER0);
722 memcpy(jh->b_frozen_data, source+offset, jh2bh(jh)->b_size);
723 kunmap_atomic(source, KM_USER0);
725 jbd_unlock_bh_state(bh);
728 * If we are about to journal a buffer, then any revoke pending on it is
731 journal_cancel_revoke(handle, jh);
735 kfree(frozen_buffer);
737 JBUFFER_TRACE(jh, "exit");
742 * int journal_get_write_access() - notify intent to modify a buffer for metadata (not data) update.
743 * @handle: transaction to add buffer modifications to
744 * @bh: bh to be used for metadata writes
746 * Returns an error code or 0 on success.
748 * In full data journalling mode the buffer may be of type BJ_AsyncData,
749 * because we're write()ing a buffer which is also part of a shared mapping.
752 int journal_get_write_access(handle_t *handle,
753 struct buffer_head *bh, int *credits)
755 struct journal_head *jh = journal_add_journal_head(bh);
758 /* We do not want to get caught playing with fields which the
759 * log thread also manipulates. Make sure that the buffer
760 * completes any outstanding IO before proceeding. */
761 rc = do_get_write_access(handle, jh, 0, credits);
762 journal_put_journal_head(jh);
768 * When the user wants to journal a newly created buffer_head
769 * (ie. getblk() returned a new buffer and we are going to populate it
770 * manually rather than reading off disk), then we need to keep the
771 * buffer_head locked until it has been completely filled with new
772 * data. In this case, we should be able to make the assertion that
773 * the bh is not already part of an existing transaction.
775 * The buffer should already be locked by the caller by this point.
776 * There is no lock ranking violation: it was a newly created,
777 * unlocked buffer beforehand. */
780 * int journal_get_create_access () - notify intent to use newly created bh
781 * @handle: transaction to new buffer to
784 * Call this if you create a new bh.
786 int journal_get_create_access(handle_t *handle, struct buffer_head *bh)
788 transaction_t *transaction = handle->h_transaction;
789 journal_t *journal = transaction->t_journal;
790 struct journal_head *jh = journal_add_journal_head(bh);
793 jbd_debug(5, "journal_head %p\n", jh);
795 if (is_handle_aborted(handle))
799 JBUFFER_TRACE(jh, "entry");
801 * The buffer may already belong to this transaction due to pre-zeroing
802 * in the filesystem's new_block code. It may also be on the previous,
803 * committing transaction's lists, but it HAS to be in Forget state in
804 * that case: the transaction must have deleted the buffer for it to be
807 jbd_lock_bh_state(bh);
808 spin_lock(&journal->j_list_lock);
809 J_ASSERT_JH(jh, (jh->b_transaction == transaction ||
810 jh->b_transaction == NULL ||
811 (jh->b_transaction == journal->j_committing_transaction &&
812 jh->b_jlist == BJ_Forget)));
814 J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
815 J_ASSERT_JH(jh, buffer_locked(jh2bh(jh)));
817 J_ASSERT_JH(jh, handle->h_buffer_credits > 0);
818 handle->h_buffer_credits--;
820 if (jh->b_transaction == NULL) {
821 jh->b_transaction = transaction;
822 JBUFFER_TRACE(jh, "file as BJ_Reserved");
823 __journal_file_buffer(jh, transaction, BJ_Reserved);
824 } else if (jh->b_transaction == journal->j_committing_transaction) {
825 JBUFFER_TRACE(jh, "set next transaction");
826 jh->b_next_transaction = transaction;
828 spin_unlock(&journal->j_list_lock);
829 jbd_unlock_bh_state(bh);
832 * akpm: I added this. ext3_alloc_branch can pick up new indirect
833 * blocks which contain freed but then revoked metadata. We need
834 * to cancel the revoke in case we end up freeing it yet again
835 * and the reallocating as data - this would cause a second revoke,
836 * which hits an assertion error.
838 JBUFFER_TRACE(jh, "cancelling revoke");
839 journal_cancel_revoke(handle, jh);
840 journal_put_journal_head(jh);
846 * int journal_get_undo_access() - Notify intent to modify metadata with
847 * non-rewindable consequences
848 * @handle: transaction
849 * @bh: buffer to undo
850 * @credits: store the number of taken credits here (if not NULL)
852 * Sometimes there is a need to distinguish between metadata which has
853 * been committed to disk and that which has not. The ext3fs code uses
854 * this for freeing and allocating space, we have to make sure that we
855 * do not reuse freed space until the deallocation has been committed,
856 * since if we overwrote that space we would make the delete
857 * un-rewindable in case of a crash.
859 * To deal with that, journal_get_undo_access requests write access to a
860 * buffer for parts of non-rewindable operations such as delete
861 * operations on the bitmaps. The journaling code must keep a copy of
862 * the buffer's contents prior to the undo_access call until such time
863 * as we know that the buffer has definitely been committed to disk.
865 * We never need to know which transaction the committed data is part
866 * of, buffers touched here are guaranteed to be dirtied later and so
867 * will be committed to a new transaction in due course, at which point
868 * we can discard the old committed data pointer.
870 * Returns error number or 0 on success.
872 int journal_get_undo_access(handle_t *handle, struct buffer_head *bh,
876 struct journal_head *jh = journal_add_journal_head(bh);
877 char *committed_data = NULL;
879 JBUFFER_TRACE(jh, "entry");
882 * Do this first --- it can drop the journal lock, so we want to
883 * make sure that obtaining the committed_data is done
884 * atomically wrt. completion of any outstanding commits.
886 err = do_get_write_access(handle, jh, 1, credits);
891 if (!jh->b_committed_data) {
892 committed_data = jbd_kmalloc(jh2bh(jh)->b_size, GFP_NOFS);
893 if (!committed_data) {
894 printk(KERN_EMERG "%s: No memory for committed data\n",
901 jbd_lock_bh_state(bh);
902 if (!jh->b_committed_data) {
903 /* Copy out the current buffer contents into the
904 * preserved, committed copy. */
905 JBUFFER_TRACE(jh, "generate b_committed data");
906 if (!committed_data) {
907 jbd_unlock_bh_state(bh);
911 jh->b_committed_data = committed_data;
912 committed_data = NULL;
913 memcpy(jh->b_committed_data, bh->b_data, bh->b_size);
915 jbd_unlock_bh_state(bh);
917 journal_put_journal_head(jh);
919 kfree(committed_data);
924 * int journal_dirty_data() - mark a buffer as containing dirty data which
925 * needs to be flushed before we can commit the
926 * current transaction.
927 * @handle: transaction
928 * @bh: bufferhead to mark
930 * The buffer is placed on the transaction's data list and is marked as
931 * belonging to the transaction.
933 * Returns error number or 0 on success.
935 * journal_dirty_data() can be called via page_launder->ext3_writepage
938 int journal_dirty_data(handle_t *handle, struct buffer_head *bh)
940 journal_t *journal = handle->h_transaction->t_journal;
942 struct journal_head *jh;
944 if (is_handle_aborted(handle))
947 jh = journal_add_journal_head(bh);
948 JBUFFER_TRACE(jh, "entry");
951 * The buffer could *already* be dirty. Writeout can start
954 jbd_debug(4, "jh: %p, tid:%d\n", jh, handle->h_transaction->t_tid);
957 * What if the buffer is already part of a running transaction?
959 * There are two cases:
960 * 1) It is part of the current running transaction. Refile it,
961 * just in case we have allocated it as metadata, deallocated
962 * it, then reallocated it as data.
963 * 2) It is part of the previous, still-committing transaction.
964 * If all we want to do is to guarantee that the buffer will be
965 * written to disk before this new transaction commits, then
966 * being sure that the *previous* transaction has this same
967 * property is sufficient for us! Just leave it on its old
970 * In case (2), the buffer must not already exist as metadata
971 * --- that would violate write ordering (a transaction is free
972 * to write its data at any point, even before the previous
973 * committing transaction has committed). The caller must
974 * never, ever allow this to happen: there's nothing we can do
975 * about it in this layer.
977 jbd_lock_bh_state(bh);
978 spin_lock(&journal->j_list_lock);
979 if (jh->b_transaction) {
980 JBUFFER_TRACE(jh, "has transaction");
981 if (jh->b_transaction != handle->h_transaction) {
982 JBUFFER_TRACE(jh, "belongs to older transaction");
983 J_ASSERT_JH(jh, jh->b_transaction ==
984 journal->j_committing_transaction);
986 /* @@@ IS THIS TRUE ? */
988 * Not any more. Scenario: someone does a write()
989 * in data=journal mode. The buffer's transaction has
990 * moved into commit. Then someone does another
991 * write() to the file. We do the frozen data copyout
992 * and set b_next_transaction to point to j_running_t.
993 * And while we're in that state, someone does a
994 * writepage() in an attempt to pageout the same area
995 * of the file via a shared mapping. At present that
996 * calls journal_dirty_data(), and we get right here.
997 * It may be too late to journal the data. Simply
998 * falling through to the next test will suffice: the
999 * data will be dirty and wil be checkpointed. The
1000 * ordering comments in the next comment block still
1003 //J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
1006 * If we're journalling data, and this buffer was
1007 * subject to a write(), it could be metadata, forget
1008 * or shadow against the committing transaction. Now,
1009 * someone has dirtied the same darn page via a mapping
1010 * and it is being writepage()'d.
1011 * We *could* just steal the page from commit, with some
1012 * fancy locking there. Instead, we just skip it -
1013 * don't tie the page's buffers to the new transaction
1015 * Implication: if we crash before the writepage() data
1016 * is written into the filesystem, recovery will replay
1019 if (jh->b_jlist != BJ_None &&
1020 jh->b_jlist != BJ_SyncData &&
1021 jh->b_jlist != BJ_Locked) {
1022 JBUFFER_TRACE(jh, "Not stealing");
1027 * This buffer may be undergoing writeout in commit. We
1028 * can't return from here and let the caller dirty it
1029 * again because that can cause the write-out loop in
1030 * commit to never terminate.
1032 if (buffer_dirty(bh)) {
1034 spin_unlock(&journal->j_list_lock);
1035 jbd_unlock_bh_state(bh);
1037 sync_dirty_buffer(bh);
1038 jbd_lock_bh_state(bh);
1039 spin_lock(&journal->j_list_lock);
1040 /* The buffer may become locked again at any
1041 time if it is redirtied */
1044 /* journal_clean_data_list() may have got there first */
1045 if (jh->b_transaction != NULL) {
1046 JBUFFER_TRACE(jh, "unfile from commit");
1047 __journal_unfile_buffer(jh);
1049 /* The buffer will be refiled below */
1053 * Special case --- the buffer might actually have been
1054 * allocated and then immediately deallocated in the previous,
1055 * committing transaction, so might still be left on that
1056 * transaction's metadata lists.
1058 if (jh->b_jlist != BJ_SyncData && jh->b_jlist != BJ_Locked) {
1059 JBUFFER_TRACE(jh, "not on correct data list: unfile");
1060 J_ASSERT_JH(jh, jh->b_jlist != BJ_Shadow);
1061 __journal_unfile_buffer(jh);
1062 JBUFFER_TRACE(jh, "file as data");
1063 __journal_file_buffer(jh, handle->h_transaction,
1067 JBUFFER_TRACE(jh, "not on a transaction");
1068 __journal_file_buffer(jh, handle->h_transaction, BJ_SyncData);
1071 spin_unlock(&journal->j_list_lock);
1072 jbd_unlock_bh_state(bh);
1074 BUFFER_TRACE(bh, "brelse");
1077 JBUFFER_TRACE(jh, "exit");
1078 journal_put_journal_head(jh);
1083 * int journal_dirty_metadata() - mark a buffer as containing dirty metadata
1084 * @handle: transaction to add buffer to.
1085 * @bh: buffer to mark
1087 * mark dirty metadata which needs to be journaled as part of the current
1090 * The buffer is placed on the transaction's metadata list and is marked
1091 * as belonging to the transaction.
1093 * Returns error number or 0 on success.
1095 * Special care needs to be taken if the buffer already belongs to the
1096 * current committing transaction (in which case we should have frozen
1097 * data present for that commit). In that case, we don't relink the
1098 * buffer: that only gets done when the old transaction finally
1099 * completes its commit.
1101 int journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
1103 transaction_t *transaction = handle->h_transaction;
1104 journal_t *journal = transaction->t_journal;
1105 struct journal_head *jh = bh2jh(bh);
1107 jbd_debug(5, "journal_head %p\n", jh);
1108 JBUFFER_TRACE(jh, "entry");
1109 if (is_handle_aborted(handle))
1112 jbd_lock_bh_state(bh);
1115 * fastpath, to avoid expensive locking. If this buffer is already
1116 * on the running transaction's metadata list there is nothing to do.
1117 * Nobody can take it off again because there is a handle open.
1118 * I _think_ we're OK here with SMP barriers - a mistaken decision will
1119 * result in this test being false, so we go in and take the locks.
1121 if (jh->b_transaction == transaction && jh->b_jlist == BJ_Metadata) {
1122 JBUFFER_TRACE(jh, "fastpath");
1123 J_ASSERT_JH(jh, jh->b_transaction ==
1124 journal->j_running_transaction);
1128 set_buffer_jbddirty(bh);
1131 * Metadata already on the current transaction list doesn't
1132 * need to be filed. Metadata on another transaction's list must
1133 * be committing, and will be refiled once the commit completes:
1134 * leave it alone for now.
1136 if (jh->b_transaction != transaction) {
1137 JBUFFER_TRACE(jh, "already on other transaction");
1138 J_ASSERT_JH(jh, jh->b_transaction ==
1139 journal->j_committing_transaction);
1140 J_ASSERT_JH(jh, jh->b_next_transaction == transaction);
1141 /* And this case is illegal: we can't reuse another
1142 * transaction's data buffer, ever. */
1146 /* That test should have eliminated the following case: */
1147 J_ASSERT_JH(jh, jh->b_frozen_data == 0);
1149 JBUFFER_TRACE(jh, "file as BJ_Metadata");
1150 spin_lock(&journal->j_list_lock);
1151 __journal_file_buffer(jh, handle->h_transaction, BJ_Metadata);
1152 spin_unlock(&journal->j_list_lock);
1154 jbd_unlock_bh_state(bh);
1156 JBUFFER_TRACE(jh, "exit");
1161 * journal_release_buffer: undo a get_write_access without any buffer
1162 * updates, if the update decided in the end that it didn't need access.
1164 * The caller passes in the number of credits which should be put back for
1165 * this buffer (zero or one).
1167 * We leave the buffer attached to t_reserved_list because even though this
1168 * handle doesn't want it, some other concurrent handle may want to journal
1169 * this buffer. If that handle is curently in between get_write_access() and
1170 * journal_dirty_metadata() then it expects the buffer to be reserved. If
1171 * we were to rip it off t_reserved_list here, the other handle will explode
1172 * when journal_dirty_metadata is presented with a non-reserved buffer.
1174 * If nobody really wants to journal this buffer then it will be thrown
1175 * away at the start of commit.
1178 journal_release_buffer(handle_t *handle, struct buffer_head *bh, int credits)
1180 BUFFER_TRACE(bh, "entry");
1181 handle->h_buffer_credits += credits;
1185 * void journal_forget() - bforget() for potentially-journaled buffers.
1186 * @handle: transaction handle
1187 * @bh: bh to 'forget'
1189 * We can only do the bforget if there are no commits pending against the
1190 * buffer. If the buffer is dirty in the current running transaction we
1191 * can safely unlink it.
1193 * bh may not be a journalled buffer at all - it may be a non-JBD
1194 * buffer which came off the hashtable. Check for this.
1196 * Decrements bh->b_count by one.
1198 * Allow this call even if the handle has aborted --- it may be part of
1199 * the caller's cleanup after an abort.
1201 int journal_forget (handle_t *handle, struct buffer_head *bh)
1203 transaction_t *transaction = handle->h_transaction;
1204 journal_t *journal = transaction->t_journal;
1205 struct journal_head *jh;
1208 BUFFER_TRACE(bh, "entry");
1210 jbd_lock_bh_state(bh);
1211 spin_lock(&journal->j_list_lock);
1213 if (!buffer_jbd(bh))
1217 /* Critical error: attempting to delete a bitmap buffer, maybe?
1218 * Don't do any jbd operations, and return an error. */
1219 if (!J_EXPECT_JH(jh, !jh->b_committed_data,
1220 "inconsistent data on disk")) {
1225 if (jh->b_transaction == handle->h_transaction) {
1226 J_ASSERT_JH(jh, !jh->b_frozen_data);
1228 /* If we are forgetting a buffer which is already part
1229 * of this transaction, then we can just drop it from
1230 * the transaction immediately. */
1231 clear_buffer_dirty(bh);
1232 clear_buffer_jbddirty(bh);
1234 JBUFFER_TRACE(jh, "belongs to current transaction: unfile");
1236 __journal_unfile_buffer(jh);
1239 * We are no longer going to journal this buffer.
1240 * However, the commit of this transaction is still
1241 * important to the buffer: the delete that we are now
1242 * processing might obsolete an old log entry, so by
1243 * committing, we can satisfy the buffer's checkpoint.
1245 * So, if we have a checkpoint on the buffer, we should
1246 * now refile the buffer on our BJ_Forget list so that
1247 * we know to remove the checkpoint after we commit.
1250 if (jh->b_cp_transaction) {
1251 __journal_file_buffer(jh, transaction, BJ_Forget);
1253 journal_remove_journal_head(bh);
1255 if (!buffer_jbd(bh)) {
1256 spin_unlock(&journal->j_list_lock);
1257 jbd_unlock_bh_state(bh);
1262 } else if (jh->b_transaction) {
1263 J_ASSERT_JH(jh, (jh->b_transaction ==
1264 journal->j_committing_transaction));
1265 /* However, if the buffer is still owned by a prior
1266 * (committing) transaction, we can't drop it yet... */
1267 JBUFFER_TRACE(jh, "belongs to older transaction");
1268 /* ... but we CAN drop it from the new transaction if we
1269 * have also modified it since the original commit. */
1271 if (jh->b_next_transaction) {
1272 J_ASSERT(jh->b_next_transaction == transaction);
1273 jh->b_next_transaction = NULL;
1278 spin_unlock(&journal->j_list_lock);
1279 jbd_unlock_bh_state(bh);
1285 * int journal_stop() - complete a transaction
1286 * @handle: tranaction to complete.
1288 * All done for a particular handle.
1290 * There is not much action needed here. We just return any remaining
1291 * buffer credits to the transaction and remove the handle. The only
1292 * complication is that we need to start a commit operation if the
1293 * filesystem is marked for synchronous update.
1295 * journal_stop itself will not usually return an error, but it may
1296 * do so in unusual circumstances. In particular, expect it to
1297 * return -EIO if a journal_abort has been executed since the
1298 * transaction began.
1300 int journal_stop(handle_t *handle)
1302 transaction_t *transaction = handle->h_transaction;
1303 journal_t *journal = transaction->t_journal;
1304 int old_handle_count, err;
1306 J_ASSERT(transaction->t_updates > 0);
1307 J_ASSERT(journal_current_handle() == handle);
1309 if (is_handle_aborted(handle))
1314 if (--handle->h_ref > 0) {
1315 jbd_debug(4, "h_ref %d -> %d\n", handle->h_ref + 1,
1320 jbd_debug(4, "Handle %p going down\n", handle);
1323 * Implement synchronous transaction batching. If the handle
1324 * was synchronous, don't force a commit immediately. Let's
1325 * yield and let another thread piggyback onto this transaction.
1326 * Keep doing that while new threads continue to arrive.
1327 * It doesn't cost much - we're about to run a commit and sleep
1328 * on IO anyway. Speeds up many-threaded, many-dir operations
1331 if (handle->h_sync) {
1333 old_handle_count = transaction->t_handle_count;
1334 set_current_state(TASK_UNINTERRUPTIBLE);
1335 schedule_timeout(1);
1336 } while (old_handle_count != transaction->t_handle_count);
1339 current->journal_info = NULL;
1340 spin_lock(&journal->j_state_lock);
1341 spin_lock(&transaction->t_handle_lock);
1342 transaction->t_outstanding_credits -= handle->h_buffer_credits;
1343 transaction->t_updates--;
1344 if (!transaction->t_updates) {
1345 wake_up(&journal->j_wait_updates);
1346 if (journal->j_barrier_count)
1347 wake_up(&journal->j_wait_transaction_locked);
1351 * If the handle is marked SYNC, we need to set another commit
1352 * going! We also want to force a commit if the current
1353 * transaction is occupying too much of the log, or if the
1354 * transaction is too old now.
1356 if (handle->h_sync ||
1357 transaction->t_outstanding_credits >
1358 journal->j_max_transaction_buffers ||
1359 time_after_eq(jiffies, transaction->t_expires)) {
1360 /* Do this even for aborted journals: an abort still
1361 * completes the commit thread, it just doesn't write
1362 * anything to disk. */
1363 tid_t tid = transaction->t_tid;
1365 spin_unlock(&transaction->t_handle_lock);
1366 jbd_debug(2, "transaction too old, requesting commit for "
1367 "handle %p\n", handle);
1368 /* This is non-blocking */
1369 __log_start_commit(journal, transaction->t_tid);
1370 spin_unlock(&journal->j_state_lock);
1373 * Special case: JFS_SYNC synchronous updates require us
1374 * to wait for the commit to complete.
1376 if (handle->h_sync && !(current->flags & PF_MEMALLOC))
1377 err = log_wait_commit(journal, tid);
1379 spin_unlock(&transaction->t_handle_lock);
1380 spin_unlock(&journal->j_state_lock);
1383 jbd_free_handle(handle);
1387 /**int journal_force_commit() - force any uncommitted transactions
1388 * @journal: journal to force
1390 * For synchronous operations: force any uncommitted transactions
1391 * to disk. May seem kludgy, but it reuses all the handle batching
1392 * code in a very simple manner.
1394 int journal_force_commit(journal_t *journal)
1399 handle = journal_start(journal, 1);
1400 if (IS_ERR(handle)) {
1401 ret = PTR_ERR(handle);
1404 ret = journal_stop(handle);
1411 * List management code snippets: various functions for manipulating the
1412 * transaction buffer lists.
1417 * Append a buffer to a transaction list, given the transaction's list head
1420 * j_list_lock is held.
1422 * jbd_lock_bh_state(jh2bh(jh)) is held.
1426 __blist_add_buffer(struct journal_head **list, struct journal_head *jh)
1429 jh->b_tnext = jh->b_tprev = jh;
1432 /* Insert at the tail of the list to preserve order */
1433 struct journal_head *first = *list, *last = first->b_tprev;
1435 jh->b_tnext = first;
1436 last->b_tnext = first->b_tprev = jh;
1441 * Remove a buffer from a transaction list, given the transaction's list
1444 * Called with j_list_lock held, and the journal may not be locked.
1446 * jbd_lock_bh_state(jh2bh(jh)) is held.
1450 __blist_del_buffer(struct journal_head **list, struct journal_head *jh)
1453 *list = jh->b_tnext;
1457 jh->b_tprev->b_tnext = jh->b_tnext;
1458 jh->b_tnext->b_tprev = jh->b_tprev;
1462 * Remove a buffer from the appropriate transaction list.
1464 * Note that this function can *change* the value of
1465 * bh->b_transaction->t_sync_datalist, t_buffers, t_forget,
1466 * t_iobuf_list, t_shadow_list, t_log_list or t_reserved_list. If the caller
1467 * is holding onto a copy of one of thee pointers, it could go bad.
1468 * Generally the caller needs to re-read the pointer from the transaction_t.
1470 * Called under j_list_lock. The journal may not be locked.
1472 void __journal_unfile_buffer(struct journal_head *jh)
1474 struct journal_head **list = NULL;
1475 transaction_t *transaction;
1476 struct buffer_head *bh = jh2bh(jh);
1478 J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
1479 transaction = jh->b_transaction;
1481 assert_spin_locked(&transaction->t_journal->j_list_lock);
1483 J_ASSERT_JH(jh, jh->b_jlist < BJ_Types);
1484 if (jh->b_jlist != BJ_None)
1485 J_ASSERT_JH(jh, transaction != 0);
1487 switch (jh->b_jlist) {
1491 list = &transaction->t_sync_datalist;
1494 transaction->t_nr_buffers--;
1495 J_ASSERT_JH(jh, transaction->t_nr_buffers >= 0);
1496 list = &transaction->t_buffers;
1499 list = &transaction->t_forget;
1502 list = &transaction->t_iobuf_list;
1505 list = &transaction->t_shadow_list;
1508 list = &transaction->t_log_list;
1511 list = &transaction->t_reserved_list;
1514 list = &transaction->t_locked_list;
1518 __blist_del_buffer(list, jh);
1519 jh->b_jlist = BJ_None;
1520 if (test_clear_buffer_jbddirty(bh))
1521 mark_buffer_dirty(bh); /* Expose it to the VM */
1523 jh->b_transaction = NULL;
1526 void journal_unfile_buffer(journal_t *journal, struct journal_head *jh)
1528 jbd_lock_bh_state(jh2bh(jh));
1529 spin_lock(&journal->j_list_lock);
1530 __journal_unfile_buffer(jh);
1531 spin_unlock(&journal->j_list_lock);
1532 jbd_unlock_bh_state(jh2bh(jh));
1536 * Called from journal_try_to_free_buffers().
1538 * Called under jbd_lock_bh_state(bh)
1541 __journal_try_to_free_buffer(journal_t *journal, struct buffer_head *bh)
1543 struct journal_head *jh;
1547 if (buffer_locked(bh) || buffer_dirty(bh))
1550 if (jh->b_next_transaction != 0)
1553 spin_lock(&journal->j_list_lock);
1554 if (jh->b_transaction != 0 && jh->b_cp_transaction == 0) {
1555 if (jh->b_jlist == BJ_SyncData || jh->b_jlist == BJ_Locked) {
1556 /* A written-back ordered data buffer */
1557 JBUFFER_TRACE(jh, "release data");
1558 __journal_unfile_buffer(jh);
1559 journal_remove_journal_head(bh);
1562 } else if (jh->b_cp_transaction != 0 && jh->b_transaction == 0) {
1563 /* written-back checkpointed metadata buffer */
1564 if (jh->b_jlist == BJ_None) {
1565 JBUFFER_TRACE(jh, "remove from checkpoint list");
1566 __journal_remove_checkpoint(jh);
1567 journal_remove_journal_head(bh);
1571 spin_unlock(&journal->j_list_lock);
1578 * int journal_try_to_free_buffers() - try to free page buffers.
1579 * @journal: journal for operation
1580 * @page: to try and free
1581 * @gfp_mask: 'IO' mode for try_to_free_buffers()
1584 * For all the buffers on this page,
1585 * if they are fully written out ordered data, move them onto BUF_CLEAN
1586 * so try_to_free_buffers() can reap them.
1588 * This function returns non-zero if we wish try_to_free_buffers()
1589 * to be called. We do this if the page is releasable by try_to_free_buffers().
1590 * We also do it if the page has locked or dirty buffers and the caller wants
1591 * us to perform sync or async writeout.
1593 * This complicates JBD locking somewhat. We aren't protected by the
1594 * BKL here. We wish to remove the buffer from its committing or
1595 * running transaction's ->t_datalist via __journal_unfile_buffer.
1597 * This may *change* the value of transaction_t->t_datalist, so anyone
1598 * who looks at t_datalist needs to lock against this function.
1600 * Even worse, someone may be doing a journal_dirty_data on this
1601 * buffer. So we need to lock against that. journal_dirty_data()
1602 * will come out of the lock with the buffer dirty, which makes it
1603 * ineligible for release here.
1605 * Who else is affected by this? hmm... Really the only contender
1606 * is do_get_write_access() - it could be looking at the buffer while
1607 * journal_try_to_free_buffer() is changing its state. But that
1608 * cannot happen because we never reallocate freed data as metadata
1609 * while the data is part of a transaction. Yes?
1611 int journal_try_to_free_buffers(journal_t *journal,
1612 struct page *page, int unused_gfp_mask)
1614 struct buffer_head *head;
1615 struct buffer_head *bh;
1618 J_ASSERT(PageLocked(page));
1620 head = page_buffers(page);
1623 struct journal_head *jh;
1626 * We take our own ref against the journal_head here to avoid
1627 * having to add tons of locking around each instance of
1628 * journal_remove_journal_head() and journal_put_journal_head().
1630 jh = journal_grab_journal_head(bh);
1634 jbd_lock_bh_state(bh);
1635 __journal_try_to_free_buffer(journal, bh);
1636 journal_put_journal_head(jh);
1637 jbd_unlock_bh_state(bh);
1640 } while ((bh = bh->b_this_page) != head);
1641 ret = try_to_free_buffers(page);
1647 * This buffer is no longer needed. If it is on an older transaction's
1648 * checkpoint list we need to record it on this transaction's forget list
1649 * to pin this buffer (and hence its checkpointing transaction) down until
1650 * this transaction commits. If the buffer isn't on a checkpoint list, we
1652 * Returns non-zero if JBD no longer has an interest in the buffer.
1654 * Called under j_list_lock.
1656 * Called under jbd_lock_bh_state(bh).
1658 static int __dispose_buffer(struct journal_head *jh, transaction_t *transaction)
1661 struct buffer_head *bh = jh2bh(jh);
1663 __journal_unfile_buffer(jh);
1665 if (jh->b_cp_transaction) {
1666 JBUFFER_TRACE(jh, "on running+cp transaction");
1667 __journal_file_buffer(jh, transaction, BJ_Forget);
1668 clear_buffer_jbddirty(bh);
1671 JBUFFER_TRACE(jh, "on running transaction");
1672 journal_remove_journal_head(bh);
1679 * journal_invalidatepage
1681 * This code is tricky. It has a number of cases to deal with.
1683 * There are two invariants which this code relies on:
1685 * i_size must be updated on disk before we start calling invalidatepage on the
1688 * This is done in ext3 by defining an ext3_setattr method which
1689 * updates i_size before truncate gets going. By maintaining this
1690 * invariant, we can be sure that it is safe to throw away any buffers
1691 * attached to the current transaction: once the transaction commits,
1692 * we know that the data will not be needed.
1694 * Note however that we can *not* throw away data belonging to the
1695 * previous, committing transaction!
1697 * Any disk blocks which *are* part of the previous, committing
1698 * transaction (and which therefore cannot be discarded immediately) are
1699 * not going to be reused in the new running transaction
1701 * The bitmap committed_data images guarantee this: any block which is
1702 * allocated in one transaction and removed in the next will be marked
1703 * as in-use in the committed_data bitmap, so cannot be reused until
1704 * the next transaction to delete the block commits. This means that
1705 * leaving committing buffers dirty is quite safe: the disk blocks
1706 * cannot be reallocated to a different file and so buffer aliasing is
1710 * The above applies mainly to ordered data mode. In writeback mode we
1711 * don't make guarantees about the order in which data hits disk --- in
1712 * particular we don't guarantee that new dirty data is flushed before
1713 * transaction commit --- so it is always safe just to discard data
1714 * immediately in that mode. --sct
1718 * The journal_unmap_buffer helper function returns zero if the buffer
1719 * concerned remains pinned as an anonymous buffer belonging to an older
1722 * We're outside-transaction here. Either or both of j_running_transaction
1723 * and j_committing_transaction may be NULL.
1725 static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh)
1727 transaction_t *transaction;
1728 struct journal_head *jh;
1732 BUFFER_TRACE(bh, "entry");
1735 * It is safe to proceed here without the j_list_lock because the
1736 * buffers cannot be stolen by try_to_free_buffers as long as we are
1737 * holding the page lock. --sct
1740 if (!buffer_jbd(bh))
1741 goto zap_buffer_unlocked;
1743 spin_lock(&journal->j_state_lock);
1744 jbd_lock_bh_state(bh);
1745 spin_lock(&journal->j_list_lock);
1747 jh = journal_grab_journal_head(bh);
1749 goto zap_buffer_no_jh;
1751 transaction = jh->b_transaction;
1752 if (transaction == NULL) {
1753 /* First case: not on any transaction. If it
1754 * has no checkpoint link, then we can zap it:
1755 * it's a writeback-mode buffer so we don't care
1756 * if it hits disk safely. */
1757 if (!jh->b_cp_transaction) {
1758 JBUFFER_TRACE(jh, "not on any transaction: zap");
1762 if (!buffer_dirty(bh)) {
1763 /* bdflush has written it. We can drop it now */
1767 /* OK, it must be in the journal but still not
1768 * written fully to disk: it's metadata or
1769 * journaled data... */
1771 if (journal->j_running_transaction) {
1772 /* ... and once the current transaction has
1773 * committed, the buffer won't be needed any
1775 JBUFFER_TRACE(jh, "checkpointed: add to BJ_Forget");
1776 ret = __dispose_buffer(jh,
1777 journal->j_running_transaction);
1778 spin_unlock(&journal->j_list_lock);
1779 jbd_unlock_bh_state(bh);
1780 spin_unlock(&journal->j_state_lock);
1781 journal_put_journal_head(jh);
1784 /* There is no currently-running transaction. So the
1785 * orphan record which we wrote for this file must have
1786 * passed into commit. We must attach this buffer to
1787 * the committing transaction, if it exists. */
1788 if (journal->j_committing_transaction) {
1789 JBUFFER_TRACE(jh, "give to committing trans");
1790 ret = __dispose_buffer(jh,
1791 journal->j_committing_transaction);
1792 spin_unlock(&journal->j_list_lock);
1793 jbd_unlock_bh_state(bh);
1794 spin_unlock(&journal->j_state_lock);
1795 journal_put_journal_head(jh);
1798 /* The orphan record's transaction has
1799 * committed. We can cleanse this buffer */
1800 clear_buffer_jbddirty(bh);
1804 } else if (transaction == journal->j_committing_transaction) {
1805 /* If it is committing, we simply cannot touch it. We
1806 * can remove it's next_transaction pointer from the
1807 * running transaction if that is set, but nothing
1809 JBUFFER_TRACE(jh, "on committing transaction");
1810 set_buffer_freed(bh);
1811 if (jh->b_next_transaction) {
1812 J_ASSERT(jh->b_next_transaction ==
1813 journal->j_running_transaction);
1814 jh->b_next_transaction = NULL;
1816 spin_unlock(&journal->j_list_lock);
1817 jbd_unlock_bh_state(bh);
1818 spin_unlock(&journal->j_state_lock);
1819 journal_put_journal_head(jh);
1822 /* Good, the buffer belongs to the running transaction.
1823 * We are writing our own transaction's data, not any
1824 * previous one's, so it is safe to throw it away
1825 * (remember that we expect the filesystem to have set
1826 * i_size already for this truncate so recovery will not
1827 * expose the disk blocks we are discarding here.) */
1828 J_ASSERT_JH(jh, transaction == journal->j_running_transaction);
1829 may_free = __dispose_buffer(jh, transaction);
1833 journal_put_journal_head(jh);
1835 spin_unlock(&journal->j_list_lock);
1836 jbd_unlock_bh_state(bh);
1837 spin_unlock(&journal->j_state_lock);
1838 zap_buffer_unlocked:
1839 clear_buffer_dirty(bh);
1840 J_ASSERT_BH(bh, !buffer_jbddirty(bh));
1841 clear_buffer_mapped(bh);
1842 clear_buffer_req(bh);
1843 clear_buffer_new(bh);
1849 * int journal_invalidatepage()
1850 * @journal: journal to use for flush...
1851 * @page: page to flush
1852 * @offset: length of page to invalidate.
1854 * Reap page buffers containing data after offset in page.
1856 * Return non-zero if the page's buffers were successfully reaped.
1858 int journal_invalidatepage(journal_t *journal,
1860 unsigned long offset)
1862 struct buffer_head *head, *bh, *next;
1863 unsigned int curr_off = 0;
1866 if (!PageLocked(page))
1868 if (!page_has_buffers(page))
1871 /* We will potentially be playing with lists other than just the
1872 * data lists (especially for journaled data mode), so be
1873 * cautious in our locking. */
1875 head = bh = page_buffers(page);
1877 unsigned int next_off = curr_off + bh->b_size;
1878 next = bh->b_this_page;
1880 /* AKPM: doing lock_buffer here may be overly paranoid */
1881 if (offset <= curr_off) {
1882 /* This block is wholly outside the truncation point */
1884 may_free &= journal_unmap_buffer(journal, bh);
1887 curr_off = next_off;
1890 } while (bh != head);
1893 if (!may_free || !try_to_free_buffers(page))
1895 J_ASSERT(!page_has_buffers(page));
1901 * File a buffer on the given transaction list.
1903 void __journal_file_buffer(struct journal_head *jh,
1904 transaction_t *transaction, int jlist)
1906 struct journal_head **list = NULL;
1908 struct buffer_head *bh = jh2bh(jh);
1910 J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
1911 assert_spin_locked(&transaction->t_journal->j_list_lock);
1913 J_ASSERT_JH(jh, jh->b_jlist < BJ_Types);
1914 J_ASSERT_JH(jh, jh->b_transaction == transaction ||
1915 jh->b_transaction == 0);
1917 if (jh->b_transaction && jh->b_jlist == jlist)
1920 /* The following list of buffer states needs to be consistent
1921 * with __jbd_unexpected_dirty_buffer()'s handling of dirty
1924 if (jlist == BJ_Metadata || jlist == BJ_Reserved ||
1925 jlist == BJ_Shadow || jlist == BJ_Forget) {
1926 if (test_clear_buffer_dirty(bh) ||
1927 test_clear_buffer_jbddirty(bh))
1931 if (jh->b_transaction)
1932 __journal_unfile_buffer(jh);
1933 jh->b_transaction = transaction;
1937 J_ASSERT_JH(jh, !jh->b_committed_data);
1938 J_ASSERT_JH(jh, !jh->b_frozen_data);
1941 list = &transaction->t_sync_datalist;
1944 transaction->t_nr_buffers++;
1945 list = &transaction->t_buffers;
1948 list = &transaction->t_forget;
1951 list = &transaction->t_iobuf_list;
1954 list = &transaction->t_shadow_list;
1957 list = &transaction->t_log_list;
1960 list = &transaction->t_reserved_list;
1963 list = &transaction->t_locked_list;
1967 __blist_add_buffer(list, jh);
1968 jh->b_jlist = jlist;
1971 set_buffer_jbddirty(bh);
1974 void journal_file_buffer(struct journal_head *jh,
1975 transaction_t *transaction, int jlist)
1977 jbd_lock_bh_state(jh2bh(jh));
1978 spin_lock(&transaction->t_journal->j_list_lock);
1979 __journal_file_buffer(jh, transaction, jlist);
1980 spin_unlock(&transaction->t_journal->j_list_lock);
1981 jbd_unlock_bh_state(jh2bh(jh));
1985 * Remove a buffer from its current buffer list in preparation for
1986 * dropping it from its current transaction entirely. If the buffer has
1987 * already started to be used by a subsequent transaction, refile the
1988 * buffer on that transaction's metadata list.
1990 * Called under journal->j_list_lock
1992 * Called under jbd_lock_bh_state(jh2bh(jh))
1994 void __journal_refile_buffer(struct journal_head *jh)
1997 struct buffer_head *bh = jh2bh(jh);
1999 J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
2000 if (jh->b_transaction)
2001 assert_spin_locked(&jh->b_transaction->t_journal->j_list_lock);
2003 /* If the buffer is now unused, just drop it. */
2004 if (jh->b_next_transaction == NULL) {
2005 __journal_unfile_buffer(jh);
2010 * It has been modified by a later transaction: add it to the new
2011 * transaction's metadata list.
2014 was_dirty = test_clear_buffer_jbddirty(bh);
2015 __journal_unfile_buffer(jh);
2016 jh->b_transaction = jh->b_next_transaction;
2017 jh->b_next_transaction = NULL;
2018 __journal_file_buffer(jh, jh->b_transaction, BJ_Metadata);
2019 J_ASSERT_JH(jh, jh->b_transaction->t_state == T_RUNNING);
2022 set_buffer_jbddirty(bh);
2026 * For the unlocked version of this call, also make sure that any
2027 * hanging journal_head is cleaned up if necessary.
2029 * __journal_refile_buffer is usually called as part of a single locked
2030 * operation on a buffer_head, in which the caller is probably going to
2031 * be hooking the journal_head onto other lists. In that case it is up
2032 * to the caller to remove the journal_head if necessary. For the
2033 * unlocked journal_refile_buffer call, the caller isn't going to be
2034 * doing anything else to the buffer so we need to do the cleanup
2035 * ourselves to avoid a jh leak.
2037 * *** The journal_head may be freed by this call! ***
2039 void journal_refile_buffer(journal_t *journal, struct journal_head *jh)
2041 struct buffer_head *bh = jh2bh(jh);
2043 jbd_lock_bh_state(bh);
2044 spin_lock(&journal->j_list_lock);
2046 __journal_refile_buffer(jh);
2047 jbd_unlock_bh_state(bh);
2048 journal_remove_journal_head(bh);
2050 spin_unlock(&journal->j_list_lock);