[PATCH] jbd2: initial copy of files from jbd

This is a simple copy of the files in fs/jbd to fs/jbd2 and
/usr/incude/linux/[ext4_]jbd.h to /usr/include/[ext4_]jbd2.h

Signed-off-by: Dave Kleikamp <shaggy@austin.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2080 insertions, 0 deletions

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
new file mode 100644
index 000000000000..e1b3c8af4d17
--- /dev/null
+++ b/fs/jbd2/transaction.c
@@ -0,0 +1,2080 @@
+/*
+ * linux/fs/transaction.c
+ *
+ * Written by Stephen C. Tweedie <sct@redhat.com>, 1998
+ *
+ * Copyright 1998 Red Hat corp --- All Rights Reserved
+ *
+ * This file is part of the Linux kernel and is made available under
+ * the terms of the GNU General Public License, version 2, or at your
+ * option, any later version, incorporated herein by reference.
+ *
+ * Generic filesystem transaction handling code; part of the ext2fs
+ * journaling system.
+ *
+ * This file manages transactions (compound commits managed by the
+ * journaling code) and handles (individual atomic operations by the
+ * filesystem).
+ */
+
+#include <linux/time.h>
+#include <linux/fs.h>
+#include <linux/jbd.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/timer.h>
+#include <linux/smp_lock.h>
+#include <linux/mm.h>
+#include <linux/highmem.h>
+
+/*
+ * get_transaction: obtain a new transaction_t object.
+ *
+ * Simply allocate and initialise a new transaction.  Create it in
+ * RUNNING state and add it to the current journal (which should not
+ * have an existing running transaction: we only make a new transaction
+ * once we have started to commit the old one).
+ *
+ * Preconditions:
+ *      The journal MUST be locked.  We don't perform atomic mallocs on the
+ *      new transaction and we can't block without protecting against other
+ *      processes trying to touch the journal while it is in transition.
+ *
+ * Called under j_state_lock
+ */
+
+static transaction_t *
+get_transaction(journal_t *journal, transaction_t *transaction)
+{
+        transaction->t_journal = journal;
+        transaction->t_state = T_RUNNING;
+        transaction->t_tid = journal->j_transaction_sequence++;
+        transaction->t_expires = jiffies + journal->j_commit_interval;
+        spin_lock_init(&transaction->t_handle_lock);
+
+        /* Set up the commit timer for the new transaction. */
+        journal->j_commit_timer.expires = transaction->t_expires;
+        add_timer(&journal->j_commit_timer);
+
+        J_ASSERT(journal->j_running_transaction == NULL);
+        journal->j_running_transaction = transaction;
+
+        return transaction;
+}
+
+/*
+ * Handle management.
+ *
+ * A handle_t is an object which represents a single atomic update to a
+ * filesystem, and which tracks all of the modifications which form part
+ * of that one update.
+ */
+
+/*
+ * start_this_handle: Given a handle, deal with any locking or stalling
+ * needed to make sure that there is enough journal space for the handle
+ * to begin.  Attach the handle to a transaction and set up the
+ * transaction's buffer credits.
+ */
+
+static int start_this_handle(journal_t *journal, handle_t *handle)
+{
+        transaction_t *transaction;
+        int needed;
+        int nblocks = handle->h_buffer_credits;
+        transaction_t *new_transaction = NULL;
+        int ret = 0;
+
+        if (nblocks > journal->j_max_transaction_buffers) {
+                printk(KERN_ERR "JBD: %s wants too many credits (%d > %d)\n",
+                       current->comm, nblocks,
+                       journal->j_max_transaction_buffers);
+                ret = -ENOSPC;
+                goto out;
+        }
+
+alloc_transaction:
+        if (!journal->j_running_transaction) {
+                new_transaction = jbd_kmalloc(sizeof(*new_transaction),
+                                                GFP_NOFS);
+                if (!new_transaction) {
+                        ret = -ENOMEM;
+                        goto out;
+                }
+                memset(new_transaction, 0, sizeof(*new_transaction));
+        }
+
+        jbd_debug(3, "New handle %p going live.\n", handle);
+
+repeat:
+
+        /*
+         * We need to hold j_state_lock until t_updates has been incremented,
+         * for proper journal barrier handling
+         */
+        spin_lock(&journal->j_state_lock);
+repeat_locked:
+        if (is_journal_aborted(journal) ||
+            (journal->j_errno != 0 && !(journal->j_flags & JFS_ACK_ERR))) {
+                spin_unlock(&journal->j_state_lock);
+                ret = -EROFS;
+                goto out;
+        }
+
+        /* Wait on the journal's transaction barrier if necessary */
+        if (journal->j_barrier_count) {
+                spin_unlock(&journal->j_state_lock);
+                wait_event(journal->j_wait_transaction_locked,
+                                journal->j_barrier_count == 0);
+                goto repeat;
+        }
+
+        if (!journal->j_running_transaction) {
+                if (!new_transaction) {
+                        spin_unlock(&journal->j_state_lock);
+                        goto alloc_transaction;
+                }
+                get_transaction(journal, new_transaction);
+                new_transaction = NULL;
+        }
+
+        transaction = journal->j_running_transaction;
+
+        /*
+         * If the current transaction is locked down for commit, wait for the
+         * lock to be released.
+         */
+        if (transaction->t_state == T_LOCKED) {
+                DEFINE_WAIT(wait);
+
+                prepare_to_wait(&journal->j_wait_transaction_locked,
+                                        &wait, TASK_UNINTERRUPTIBLE);
+                spin_unlock(&journal->j_state_lock);
+                schedule();
+                finish_wait(&journal->j_wait_transaction_locked, &wait);
+                goto repeat;
+        }
+
+        /*
+         * If there is not enough space left in the log to write all potential
+         * buffers requested by this operation, we need to stall pending a log
+         * checkpoint to free some more log space.
+         */
+        spin_lock(&transaction->t_handle_lock);
+        needed = transaction->t_outstanding_credits + nblocks;
+
+        if (needed > journal->j_max_transaction_buffers) {
+                /*
+                 * If the current transaction is already too large, then start
+                 * to commit it: we can then go back and attach this handle to
+                 * a new transaction.
+                 */
+                DEFINE_WAIT(wait);
+
+                jbd_debug(2, "Handle %p starting new commit...\n", handle);
+                spin_unlock(&transaction->t_handle_lock);
+                prepare_to_wait(&journal->j_wait_transaction_locked, &wait,
+                                TASK_UNINTERRUPTIBLE);
+                __log_start_commit(journal, transaction->t_tid);
+                spin_unlock(&journal->j_state_lock);
+                schedule();
+                finish_wait(&journal->j_wait_transaction_locked, &wait);
+                goto repeat;
+        }
+
+        /*
+         * The commit code assumes that it can get enough log space
+         * without forcing a checkpoint.  This is *critical* for
+         * correctness: a checkpoint of a buffer which is also
+         * associated with a committing transaction creates a deadlock,
+         * so commit simply cannot force through checkpoints.
+         *
+         * We must therefore ensure the necessary space in the journal
+         * *before* starting to dirty potentially checkpointed buffers
+         * in the new transaction.
+         *
+         * The worst part is, any transaction currently committing can
+         * reduce the free space arbitrarily.  Be careful to account for
+         * those buffers when checkpointing.
+         */
+
+        /*
+         * @@@ AKPM: This seems rather over-defensive.  We're giving commit
+         * a _lot_ of headroom: 1/4 of the journal plus the size of
+         * the committing transaction.  Really, we only need to give it
+         * committing_transaction->t_outstanding_credits plus "enough" for
+         * the log control blocks.
+         * Also, this test is inconsitent with the matching one in
+         * journal_extend().
+         */
+        if (__log_space_left(journal) < jbd_space_needed(journal)) {
+                jbd_debug(2, "Handle %p waiting for checkpoint...\n", handle);
+                spin_unlock(&transaction->t_handle_lock);
+                __log_wait_for_space(journal);
+                goto repeat_locked;
+        }
+
+        /* OK, account for the buffers that this operation expects to
+         * use and add the handle to the running transaction. */
+
+        handle->h_transaction = transaction;
+        transaction->t_outstanding_credits += nblocks;
+        transaction->t_updates++;
+        transaction->t_handle_count++;
+        jbd_debug(4, "Handle %p given %d credits (total %d, free %d)\n",
+                  handle, nblocks, transaction->t_outstanding_credits,
+                  __log_space_left(journal));
+        spin_unlock(&transaction->t_handle_lock);
+        spin_unlock(&journal->j_state_lock);
+out:
+        if (unlikely(new_transaction))          /* It's usually NULL */
+                kfree(new_transaction);
+        return ret;
+}
+
+/* Allocate a new handle.  This should probably be in a slab... */
+static handle_t *new_handle(int nblocks)
+{
+        handle_t *handle = jbd_alloc_handle(GFP_NOFS);
+        if (!handle)
+                return NULL;
+        memset(handle, 0, sizeof(*handle));
+        handle->h_buffer_credits = nblocks;
+        handle->h_ref = 1;
+
+        return handle;
+}
+
+/**
+ * handle_t *journal_start() - Obtain a new handle.
+ * @journal: Journal to start transaction on.
+ * @nblocks: number of block buffer we might modify
+ *
+ * We make sure that the transaction can guarantee at least nblocks of
+ * modified buffers in the log.  We block until the log can guarantee
+ * that much space.
+ *
+ * This function is visible to journal users (like ext3fs), so is not
+ * called with the journal already locked.
+ *
+ * Return a pointer to a newly allocated handle, or NULL on failure
+ */
+handle_t *journal_start(journal_t *journal, int nblocks)
+{
+        handle_t *handle = journal_current_handle();
+        int err;
+
+        if (!journal)
+                return ERR_PTR(-EROFS);
+
+        if (handle) {
+                J_ASSERT(handle->h_transaction->t_journal == journal);
+                handle->h_ref++;
+                return handle;
+        }
+
+        handle = new_handle(nblocks);
+        if (!handle)
+                return ERR_PTR(-ENOMEM);
+
+        current->journal_info = handle;
+
+        err = start_this_handle(journal, handle);
+        if (err < 0) {
+                jbd_free_handle(handle);
+                current->journal_info = NULL;
+                handle = ERR_PTR(err);
+        }
+        return handle;
+}
+
+/**
+ * int journal_extend() - extend buffer credits.
+ * @handle:  handle to 'extend'
+ * @nblocks: nr blocks to try to extend by.
+ *
+ * Some transactions, such as large extends and truncates, can be done
+ * atomically all at once or in several stages.  The operation requests
+ * a credit for a number of buffer modications in advance, but can
+ * extend its credit if it needs more.
+ *
+ * journal_extend tries to give the running handle more buffer credits.
+ * It does not guarantee that allocation - this is a best-effort only.
+ * The calling process MUST be able to deal cleanly with a failure to
+ * extend here.
+ *
+ * Return 0 on success, non-zero on failure.
+ *
+ * return code < 0 implies an error
+ * return code > 0 implies normal transaction-full status.
+ */
+int journal_extend(handle_t *handle, int nblocks)
+{
+        transaction_t *transaction = handle->h_transaction;
+        journal_t *journal = transaction->t_journal;
+        int result;
+        int wanted;
+
+        result = -EIO;
+        if (is_handle_aborted(handle))
+                goto out;
+
+        result = 1;
+
+        spin_lock(&journal->j_state_lock);
+
+        /* Don't extend a locked-down transaction! */
+        if (handle->h_transaction->t_state != T_RUNNING) {
+                jbd_debug(3, "denied handle %p %d blocks: "
+                          "transaction not running\n", handle, nblocks);
+                goto error_out;
+        }
+
+        spin_lock(&transaction->t_handle_lock);
+        wanted = transaction->t_outstanding_credits + nblocks;
+
+        if (wanted > journal->j_max_transaction_buffers) {
+                jbd_debug(3, "denied handle %p %d blocks: "
+                          "transaction too large\n", handle, nblocks);
+                goto unlock;
+        }
+
+        if (wanted > __log_space_left(journal)) {
+                jbd_debug(3, "denied handle %p %d blocks: "
+                          "insufficient log space\n", handle, nblocks);
+                goto unlock;
+        }
+
+        handle->h_buffer_credits += nblocks;
+        transaction->t_outstanding_credits += nblocks;
+        result = 0;
+
+        jbd_debug(3, "extended handle %p by %d\n", handle, nblocks);
+unlock:
+        spin_unlock(&transaction->t_handle_lock);
+error_out:
+        spin_unlock(&journal->j_state_lock);
+out:
+        return result;
+}
+
+
+/**
+ * int journal_restart() - restart a handle .
+ * @handle:  handle to restart
+ * @nblocks: nr credits requested
+ *
+ * Restart a handle for a multi-transaction filesystem
+ * operation.
+ *
+ * If the journal_extend() call above fails to grant new buffer credits
+ * to a running handle, a call to journal_restart will commit the
+ * handle's transaction so far and reattach the handle to a new
+ * transaction capabable of guaranteeing the requested number of
+ * credits.
+ */
+
+int journal_restart(handle_t *handle, int nblocks)
+{
+        transaction_t *transaction = handle->h_transaction;
+        journal_t *journal = transaction->t_journal;
+        int ret;
+
+        /* If we've had an abort of any type, don't even think about
+         * actually doing the restart! */
+        if (is_handle_aborted(handle))
+                return 0;
+
+        /*
+         * First unlink the handle from its current transaction, and start the
+         * commit on that.
+         */
+        J_ASSERT(transaction->t_updates > 0);
+        J_ASSERT(journal_current_handle() == handle);
+
+        spin_lock(&journal->j_state_lock);
+        spin_lock(&transaction->t_handle_lock);
+        transaction->t_outstanding_credits -= handle->h_buffer_credits;
+        transaction->t_updates--;
+
+        if (!transaction->t_updates)
+                wake_up(&journal->j_wait_updates);
+        spin_unlock(&transaction->t_handle_lock);
+
+        jbd_debug(2, "restarting handle %p\n", handle);
+        __log_start_commit(journal, transaction->t_tid);
+        spin_unlock(&journal->j_state_lock);
+
+        handle->h_buffer_credits = nblocks;
+        ret = start_this_handle(journal, handle);
+        return ret;
+}
+
+
+/**
+ * void journal_lock_updates () - establish a transaction barrier.
+ * @journal:  Journal to establish a barrier on.
+ *
+ * This locks out any further updates from being started, and blocks
+ * until all existing updates have completed, returning only once the
+ * journal is in a quiescent state with no updates running.
+ *
+ * The journal lock should not be held on entry.
+ */
+void journal_lock_updates(journal_t *journal)
+{
+        DEFINE_WAIT(wait);
+
+        spin_lock(&journal->j_state_lock);
+        ++journal->j_barrier_count;
+
+        /* Wait until there are no running updates */
+        while (1) {
+                transaction_t *transaction = journal->j_running_transaction;
+
+                if (!transaction)
+                        break;
+
+                spin_lock(&transaction->t_handle_lock);
+                if (!transaction->t_updates) {
+                        spin_unlock(&transaction->t_handle_lock);
+                        break;
+                }
+                prepare_to_wait(&journal->j_wait_updates, &wait,
+                                TASK_UNINTERRUPTIBLE);
+                spin_unlock(&transaction->t_handle_lock);
+                spin_unlock(&journal->j_state_lock);
+                schedule();
+                finish_wait(&journal->j_wait_updates, &wait);
+                spin_lock(&journal->j_state_lock);
+        }
+        spin_unlock(&journal->j_state_lock);
+
+        /*
+         * We have now established a barrier against other normal updates, but
+         * we also need to barrier against other journal_lock_updates() calls
+         * to make sure that we serialise special journal-locked operations
+         * too.
+         */
+        mutex_lock(&journal->j_barrier);
+}
+
+/**
+ * void journal_unlock_updates (journal_t* journal) - release barrier
+ * @journal:  Journal to release the barrier on.
+ *
+ * Release a transaction barrier obtained with journal_lock_updates().
+ *
+ * Should be called without the journal lock held.
+ */
+void journal_unlock_updates (journal_t *journal)
+{
+        J_ASSERT(journal->j_barrier_count != 0);
+
+        mutex_unlock(&journal->j_barrier);
+        spin_lock(&journal->j_state_lock);
+        --journal->j_barrier_count;
+        spin_unlock(&journal->j_state_lock);
+        wake_up(&journal->j_wait_transaction_locked);
+}
+
+/*
+ * Report any unexpected dirty buffers which turn up.  Normally those
+ * indicate an error, but they can occur if the user is running (say)
+ * tune2fs to modify the live filesystem, so we need the option of
+ * continuing as gracefully as possible.  #
+ *
+ * The caller should already hold the journal lock and
+ * j_list_lock spinlock: most callers will need those anyway
+ * in order to probe the buffer's journaling state safely.
+ */
+static void jbd_unexpected_dirty_buffer(struct journal_head *jh)
+{
+        int jlist;
+
+        /* If this buffer is one which might reasonably be dirty
+         * --- ie. data, or not part of this journal --- then
+         * we're OK to leave it alone, but otherwise we need to
+         * move the dirty bit to the journal's own internal
+         * JBDDirty bit. */
+        jlist = jh->b_jlist;
+
+        if (jlist == BJ_Metadata || jlist == BJ_Reserved ||
+            jlist == BJ_Shadow || jlist == BJ_Forget) {
+                struct buffer_head *bh = jh2bh(jh);
+
+                if (test_clear_buffer_dirty(bh))
+                        set_buffer_jbddirty(bh);
+        }
+}
+
+/*
+ * If the buffer is already part of the current transaction, then there
+ * is nothing we need to do.  If it is already part of a prior
+ * transaction which we are still committing to disk, then we need to
+ * make sure that we do not overwrite the old copy: we do copy-out to
+ * preserve the copy going to disk.  We also account the buffer against
+ * the handle's metadata buffer credits (unless the buffer is already
+ * part of the transaction, that is).
+ *
+ */
+static int
+do_get_write_access(handle_t *handle, struct journal_head *jh,
+                        int force_copy)
+{
+        struct buffer_head *bh;
+        transaction_t *transaction;
+        journal_t *journal;
+        int error;
+        char *frozen_buffer = NULL;
+        int need_copy = 0;
+
+        if (is_handle_aborted(handle))
+                return -EROFS;
+
+        transaction = handle->h_transaction;
+        journal = transaction->t_journal;
+
+        jbd_debug(5, "buffer_head %p, force_copy %d\n", jh, force_copy);
+
+        JBUFFER_TRACE(jh, "entry");
+repeat:
+        bh = jh2bh(jh);
+
+        /* @@@ Need to check for errors here at some point. */
+
+        lock_buffer(bh);
+        jbd_lock_bh_state(bh);
+
+        /* We now hold the buffer lock so it is safe to query the buffer
+         * state.  Is the buffer dirty?
+         *
+         * If so, there are two possibilities.  The buffer may be
+         * non-journaled, and undergoing a quite legitimate writeback.
+         * Otherwise, it is journaled, and we don't expect dirty buffers
+         * in that state (the buffers should be marked JBD_Dirty
+         * instead.)  So either the IO is being done under our own
+         * control and this is a bug, or it's a third party IO such as
+         * dump(8) (which may leave the buffer scheduled for read ---
+         * ie. locked but not dirty) or tune2fs (which may actually have
+         * the buffer dirtied, ugh.)  */
+
+        if (buffer_dirty(bh)) {
+                /*
+                 * First question: is this buffer already part of the current
+                 * transaction or the existing committing transaction?
+                 */
+                if (jh->b_transaction) {
+                        J_ASSERT_JH(jh,
+                                jh->b_transaction == transaction ||
+                                jh->b_transaction ==
+                                        journal->j_committing_transaction);
+                        if (jh->b_next_transaction)
+                                J_ASSERT_JH(jh, jh->b_next_transaction ==
+                                                        transaction);
+                }
+                /*
+                 * In any case we need to clean the dirty flag and we must
+                 * do it under the buffer lock to be sure we don't race
+                 * with running write-out.
+                 */
+                JBUFFER_TRACE(jh, "Unexpected dirty buffer");
+                jbd_unexpected_dirty_buffer(jh);
+        }
+
+        unlock_buffer(bh);
+
+        error = -EROFS;
+        if (is_handle_aborted(handle)) {
+                jbd_unlock_bh_state(bh);
+                goto out;
+        }
+        error = 0;
+
+        /*
+         * The buffer is already part of this transaction if b_transaction or
+         * b_next_transaction points to it
+         */
+        if (jh->b_transaction == transaction ||
+            jh->b_next_transaction == transaction)
+                goto done;
+
+        /*
+         * If there is already a copy-out version of this buffer, then we don't
+         * need to make another one
+         */
+        if (jh->b_frozen_data) {
+                JBUFFER_TRACE(jh, "has frozen data");
+                J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
+                jh->b_next_transaction = transaction;
+                goto done;
+        }
+
+        /* Is there data here we need to preserve? */
+
+        if (jh->b_transaction && jh->b_transaction != transaction) {
+                JBUFFER_TRACE(jh, "owned by older transaction");
+                J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
+                J_ASSERT_JH(jh, jh->b_transaction ==
+                                        journal->j_committing_transaction);
+
+                /* There is one case we have to be very careful about.
+                 * If the committing transaction is currently writing
+                 * this buffer out to disk and has NOT made a copy-out,
+                 * then we cannot modify the buffer contents at all
+                 * right now.  The essence of copy-out is that it is the
+                 * extra copy, not the primary copy, which gets
+                 * journaled.  If the primary copy is already going to
+                 * disk then we cannot do copy-out here. */
+
+                if (jh->b_jlist == BJ_Shadow) {
+                        DEFINE_WAIT_BIT(wait, &bh->b_state, BH_Unshadow);
+                        wait_queue_head_t *wqh;
+
+                        wqh = bit_waitqueue(&bh->b_state, BH_Unshadow);
+
+                        JBUFFER_TRACE(jh, "on shadow: sleep");
+                        jbd_unlock_bh_state(bh);
+                        /* commit wakes up all shadow buffers after IO */
+                        for ( ; ; ) {
+                                prepare_to_wait(wqh, &wait.wait,
+                                                TASK_UNINTERRUPTIBLE);
+                                if (jh->b_jlist != BJ_Shadow)
+                                        break;
+                                schedule();
+                        }
+                        finish_wait(wqh, &wait.wait);
+                        goto repeat;
+                }
+
+                /* Only do the copy if the currently-owning transaction
+                 * still needs it.  If it is on the Forget list, the
+                 * committing transaction is past that stage.  The
+                 * buffer had better remain locked during the kmalloc,
+                 * but that should be true --- we hold the journal lock
+                 * still and the buffer is already on the BUF_JOURNAL
+                 * list so won't be flushed.
+                 *
+                 * Subtle point, though: if this is a get_undo_access,
+                 * then we will be relying on the frozen_data to contain
+                 * the new value of the committed_data record after the
+                 * transaction, so we HAVE to force the frozen_data copy
+                 * in that case. */
+
+                if (jh->b_jlist != BJ_Forget || force_copy) {
+                        JBUFFER_TRACE(jh, "generate frozen data");
+                        if (!frozen_buffer) {
+                                JBUFFER_TRACE(jh, "allocate memory for buffer");
+                                jbd_unlock_bh_state(bh);
+                                frozen_buffer =
+                                        jbd_slab_alloc(jh2bh(jh)->b_size,
+                                                         GFP_NOFS);
+                                if (!frozen_buffer) {
+                                        printk(KERN_EMERG
+                                               "%s: OOM for frozen_buffer\n",
+                                               __FUNCTION__);
+                                        JBUFFER_TRACE(jh, "oom!");
+                                        error = -ENOMEM;
+                                        jbd_lock_bh_state(bh);
+                                        goto done;
+                                }
+                                goto repeat;
+                        }
+                        jh->b_frozen_data = frozen_buffer;
+                        frozen_buffer = NULL;
+                        need_copy = 1;
+                }
+                jh->b_next_transaction = transaction;
+        }
+
+
+        /*
+         * Finally, if the buffer is not journaled right now, we need to make
+         * sure it doesn't get written to disk before the caller actually
+         * commits the new data
+         */
+        if (!jh->b_transaction) {
+                JBUFFER_TRACE(jh, "no transaction");
+                J_ASSERT_JH(jh, !jh->b_next_transaction);
+                jh->b_transaction = transaction;
+                JBUFFER_TRACE(jh, "file as BJ_Reserved");
+                spin_lock(&journal->j_list_lock);
+                __journal_file_buffer(jh, transaction, BJ_Reserved);
+                spin_unlock(&journal->j_list_lock);
+        }
+
+done:
+        if (need_copy) {
+                struct page *page;
+                int offset;
+                char *source;
+
+                J_EXPECT_JH(jh, buffer_uptodate(jh2bh(jh)),
+                            "Possible IO failure.\n");
+                page = jh2bh(jh)->b_page;
+                offset = ((unsigned long) jh2bh(jh)->b_data) & ~PAGE_MASK;
+                source = kmap_atomic(page, KM_USER0);
+                memcpy(jh->b_frozen_data, source+offset, jh2bh(jh)->b_size);
+                kunmap_atomic(source, KM_USER0);
+        }
+        jbd_unlock_bh_state(bh);
+
+        /*
+         * If we are about to journal a buffer, then any revoke pending on it is
+         * no longer valid
+         */
+        journal_cancel_revoke(handle, jh);
+
+out:
+        if (unlikely(frozen_buffer))    /* It's usually NULL */
+                jbd_slab_free(frozen_buffer, bh->b_size);
+
+        JBUFFER_TRACE(jh, "exit");
+        return error;
+}
+
+/**
+ * int journal_get_write_access() - notify intent to modify a buffer for metadata (not data) update.
+ * @handle: transaction to add buffer modifications to
+ * @bh:     bh to be used for metadata writes
+ * @credits: variable that will receive credits for the buffer
+ *
+ * Returns an error code or 0 on success.
+ *
+ * In full data journalling mode the buffer may be of type BJ_AsyncData,
+ * because we're write()ing a buffer which is also part of a shared mapping.
+ */
+
+int journal_get_write_access(handle_t *handle, struct buffer_head *bh)
+{
+        struct journal_head *jh = journal_add_journal_head(bh);
+        int rc;
+
+        /* We do not want to get caught playing with fields which the
+         * log thread also manipulates.  Make sure that the buffer
+         * completes any outstanding IO before proceeding. */
+        rc = do_get_write_access(handle, jh, 0);
+        journal_put_journal_head(jh);
+        return rc;
+}
+
+
+/*
+ * When the user wants to journal a newly created buffer_head
+ * (ie. getblk() returned a new buffer and we are going to populate it
+ * manually rather than reading off disk), then we need to keep the
+ * buffer_head locked until it has been completely filled with new
+ * data.  In this case, we should be able to make the assertion that
+ * the bh is not already part of an existing transaction.
+ *
+ * The buffer should already be locked by the caller by this point.
+ * There is no lock ranking violation: it was a newly created,
+ * unlocked buffer beforehand. */
+
+/**
+ * int journal_get_create_access () - notify intent to use newly created bh
+ * @handle: transaction to new buffer to
+ * @bh: new buffer.
+ *
+ * Call this if you create a new bh.
+ */
+int journal_get_create_access(handle_t *handle, struct buffer_head *bh)
+{
+        transaction_t *transaction = handle->h_transaction;
+        journal_t *journal = transaction->t_journal;
+        struct journal_head *jh = journal_add_journal_head(bh);
+        int err;
+
+        jbd_debug(5, "journal_head %p\n", jh);
+        err = -EROFS;
+        if (is_handle_aborted(handle))
+                goto out;
+        err = 0;
+
+        JBUFFER_TRACE(jh, "entry");
+        /*
+         * The buffer may already belong to this transaction due to pre-zeroing
+         * in the filesystem's new_block code.  It may also be on the previous,
+         * committing transaction's lists, but it HAS to be in Forget state in
+         * that case: the transaction must have deleted the buffer for it to be
+         * reused here.
+         */
+        jbd_lock_bh_state(bh);
+        spin_lock(&journal->j_list_lock);
+        J_ASSERT_JH(jh, (jh->b_transaction == transaction ||
+                jh->b_transaction == NULL ||
+                (jh->b_transaction == journal->j_committing_transaction &&
+                          jh->b_jlist == BJ_Forget)));
+
+        J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
+        J_ASSERT_JH(jh, buffer_locked(jh2bh(jh)));
+
+        if (jh->b_transaction == NULL) {
+                jh->b_transaction = transaction;
+                JBUFFER_TRACE(jh, "file as BJ_Reserved");
+                __journal_file_buffer(jh, transaction, BJ_Reserved);
+        } else if (jh->b_transaction == journal->j_committing_transaction) {
+                JBUFFER_TRACE(jh, "set next transaction");
+                jh->b_next_transaction = transaction;
+        }
+        spin_unlock(&journal->j_list_lock);
+        jbd_unlock_bh_state(bh);
+
+        /*
+         * akpm: I added this.  ext3_alloc_branch can pick up new indirect
+         * blocks which contain freed but then revoked metadata.  We need
+         * to cancel the revoke in case we end up freeing it yet again
+         * and the reallocating as data - this would cause a second revoke,
+         * which hits an assertion error.
+         */
+        JBUFFER_TRACE(jh, "cancelling revoke");
+        journal_cancel_revoke(handle, jh);
+        journal_put_journal_head(jh);
+out:
+        return err;
+}
+
+/**
+ * int journal_get_undo_access() -  Notify intent to modify metadata with
+ *     non-rewindable consequences
+ * @handle: transaction
+ * @bh: buffer to undo
+ * @credits: store the number of taken credits here (if not NULL)
+ *
+ * Sometimes there is a need to distinguish between metadata which has
+ * been committed to disk and that which has not.  The ext3fs code uses
+ * this for freeing and allocating space, we have to make sure that we
+ * do not reuse freed space until the deallocation has been committed,
+ * since if we overwrote that space we would make the delete
+ * un-rewindable in case of a crash.
+ *
+ * To deal with that, journal_get_undo_access requests write access to a
+ * buffer for parts of non-rewindable operations such as delete
+ * operations on the bitmaps.  The journaling code must keep a copy of
+ * the buffer's contents prior to the undo_access call until such time
+ * as we know that the buffer has definitely been committed to disk.
+ *
+ * We never need to know which transaction the committed data is part
+ * of, buffers touched here are guaranteed to be dirtied later and so
+ * will be committed to a new transaction in due course, at which point
+ * we can discard the old committed data pointer.
+ *
+ * Returns error number or 0 on success.
+ */
+int journal_get_undo_access(handle_t *handle, struct buffer_head *bh)
+{
+        int err;
+        struct journal_head *jh = journal_add_journal_head(bh);
+        char *committed_data = NULL;
+
+        JBUFFER_TRACE(jh, "entry");
+
+        /*
+         * Do this first --- it can drop the journal lock, so we want to
+         * make sure that obtaining the committed_data is done
+         * atomically wrt. completion of any outstanding commits.
+         */
+        err = do_get_write_access(handle, jh, 1);
+        if (err)
+                goto out;
+
+repeat:
+        if (!jh->b_committed_data) {
+                committed_data = jbd_slab_alloc(jh2bh(jh)->b_size, GFP_NOFS);
+                if (!committed_data) {
+                        printk(KERN_EMERG "%s: No memory for committed data\n",
+                                __FUNCTION__);
+                        err = -ENOMEM;
+                        goto out;
+                }
+        }
+
+        jbd_lock_bh_state(bh);
+        if (!jh->b_committed_data) {
+                /* Copy out the current buffer contents into the
+                 * preserved, committed copy. */
+                JBUFFER_TRACE(jh, "generate b_committed data");
+                if (!committed_data) {
+                        jbd_unlock_bh_state(bh);
+                        goto repeat;
+                }
+
+                jh->b_committed_data = committed_data;
+                committed_data = NULL;
+                memcpy(jh->b_committed_data, bh->b_data, bh->b_size);
+        }
+        jbd_unlock_bh_state(bh);
+out:
+        journal_put_journal_head(jh);
+        if (unlikely(committed_data))
+                jbd_slab_free(committed_data, bh->b_size);
+        return err;
+}
+
+/**
+ * int journal_dirty_data() -  mark a buffer as containing dirty data which
+ *                             needs to be flushed before we can commit the
+ *                             current transaction.
+ * @handle: transaction
+ * @bh: bufferhead to mark
+ *
+ * The buffer is placed on the transaction's data list and is marked as
+ * belonging to the transaction.
+ *
+ * Returns error number or 0 on success.
+ *
+ * journal_dirty_data() can be called via page_launder->ext3_writepage
+ * by kswapd.
+ */
+int journal_dirty_data(handle_t *handle, struct buffer_head *bh)
+{
+        journal_t *journal = handle->h_transaction->t_journal;
+        int need_brelse = 0;
+        struct journal_head *jh;
+
+        if (is_handle_aborted(handle))
+                return 0;
+
+        jh = journal_add_journal_head(bh);
+        JBUFFER_TRACE(jh, "entry");
+
+        /*
+         * The buffer could *already* be dirty.  Writeout can start
+         * at any time.
+         */
+        jbd_debug(4, "jh: %p, tid:%d\n", jh, handle->h_transaction->t_tid);
+
+        /*
+         * What if the buffer is already part of a running transaction?
+         *
+         * There are two cases:
+         * 1) It is part of the current running transaction.  Refile it,
+         *    just in case we have allocated it as metadata, deallocated
+         *    it, then reallocated it as data.
+         * 2) It is part of the previous, still-committing transaction.
+         *    If all we want to do is to guarantee that the buffer will be
+         *    written to disk before this new transaction commits, then
+         *    being sure that the *previous* transaction has this same
+         *    property is sufficient for us!  Just leave it on its old
+         *    transaction.
+         *
+         * In case (2), the buffer must not already exist as metadata
+         * --- that would violate write ordering (a transaction is free
+         * to write its data at any point, even before the previous
+         * committing transaction has committed).  The caller must
+         * never, ever allow this to happen: there's nothing we can do
+         * about it in this layer.
+         */
+        jbd_lock_bh_state(bh);
+        spin_lock(&journal->j_list_lock);
+        if (jh->b_transaction) {
+                JBUFFER_TRACE(jh, "has transaction");
+                if (jh->b_transaction != handle->h_transaction) {
+                        JBUFFER_TRACE(jh, "belongs to older transaction");
+                        J_ASSERT_JH(jh, jh->b_transaction ==
+                                        journal->j_committing_transaction);
+
+                        /* @@@ IS THIS TRUE  ? */
+                        /*
+                         * Not any more.  Scenario: someone does a write()
+                         * in data=journal mode.  The buffer's transaction has
+                         * moved into commit.  Then someone does another
+                         * write() to the file.  We do the frozen data copyout
+                         * and set b_next_transaction to point to j_running_t.
+                         * And while we're in that state, someone does a
+                         * writepage() in an attempt to pageout the same area
+                         * of the file via a shared mapping.  At present that
+                         * calls journal_dirty_data(), and we get right here.
+                         * It may be too late to journal the data.  Simply
+                         * falling through to the next test will suffice: the
+                         * data will be dirty and wil be checkpointed.  The
+                         * ordering comments in the next comment block still
+                         * apply.
+                         */
+                        //J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
+
+                        /*
+                         * If we're journalling data, and this buffer was
+                         * subject to a write(), it could be metadata, forget
+                         * or shadow against the committing transaction.  Now,
+                         * someone has dirtied the same darn page via a mapping
+                         * and it is being writepage()'d.
+                         * We *could* just steal the page from commit, with some
+                         * fancy locking there.  Instead, we just skip it -
+                         * don't tie the page's buffers to the new transaction
+                         * at all.
+                         * Implication: if we crash before the writepage() data
+                         * is written into the filesystem, recovery will replay
+                         * the write() data.
+                         */
+                        if (jh->b_jlist != BJ_None &&
+                                        jh->b_jlist != BJ_SyncData &&
+                                        jh->b_jlist != BJ_Locked) {
+                                JBUFFER_TRACE(jh, "Not stealing");
+                                goto no_journal;
+                        }
+
+                        /*
+                         * This buffer may be undergoing writeout in commit.  We
+                         * can't return from here and let the caller dirty it
+                         * again because that can cause the write-out loop in
+                         * commit to never terminate.
+                         */
+                        if (buffer_dirty(bh)) {
+                                get_bh(bh);
+                                spin_unlock(&journal->j_list_lock);
+                                jbd_unlock_bh_state(bh);
+                                need_brelse = 1;
+                                sync_dirty_buffer(bh);
+                                jbd_lock_bh_state(bh);
+                                spin_lock(&journal->j_list_lock);
+                                /* The buffer may become locked again at any
+                                   time if it is redirtied */
+                        }
+
+                        /* journal_clean_data_list() may have got there first */
+                        if (jh->b_transaction != NULL) {
+                                JBUFFER_TRACE(jh, "unfile from commit");
+                                __journal_temp_unlink_buffer(jh);
+                                /* It still points to the committing
+                                 * transaction; move it to this one so
+                                 * that the refile assert checks are
+                                 * happy. */
+                                jh->b_transaction = handle->h_transaction;
+                        }
+                        /* The buffer will be refiled below */
+
+                }
+                /*
+                 * Special case --- the buffer might actually have been
+                 * allocated and then immediately deallocated in the previous,
+                 * committing transaction, so might still be left on that
+                 * transaction's metadata lists.
+                 */
+                if (jh->b_jlist != BJ_SyncData && jh->b_jlist != BJ_Locked) {
+                        JBUFFER_TRACE(jh, "not on correct data list: unfile");
+                        J_ASSERT_JH(jh, jh->b_jlist != BJ_Shadow);
+                        __journal_temp_unlink_buffer(jh);
+                        jh->b_transaction = handle->h_transaction;
+                        JBUFFER_TRACE(jh, "file as data");
+                        __journal_file_buffer(jh, handle->h_transaction,
+                                                BJ_SyncData);
+                }
+        } else {
+                JBUFFER_TRACE(jh, "not on a transaction");
+                __journal_file_buffer(jh, handle->h_transaction, BJ_SyncData);
+        }
+no_journal:
+        spin_unlock(&journal->j_list_lock);
+        jbd_unlock_bh_state(bh);
+        if (need_brelse) {
+                BUFFER_TRACE(bh, "brelse");
+                __brelse(bh);
+        }
+        JBUFFER_TRACE(jh, "exit");
+        journal_put_journal_head(jh);
+        return 0;
+}
+
+/**
+ * int journal_dirty_metadata() -  mark a buffer as containing dirty metadata
+ * @handle: transaction to add buffer to.
+ * @bh: buffer to mark
+ *
+ * mark dirty metadata which needs to be journaled as part of the current
+ * transaction.
+ *
+ * The buffer is placed on the transaction's metadata list and is marked
+ * as belonging to the transaction.
+ *
+ * Returns error number or 0 on success.
+ *
+ * Special care needs to be taken if the buffer already belongs to the
+ * current committing transaction (in which case we should have frozen
+ * data present for that commit).  In that case, we don't relink the
+ * buffer: that only gets done when the old transaction finally
+ * completes its commit.
+ */
+int journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
+{
+        transaction_t *transaction = handle->h_transaction;
+        journal_t *journal = transaction->t_journal;
+        struct journal_head *jh = bh2jh(bh);
+
+        jbd_debug(5, "journal_head %p\n", jh);
+        JBUFFER_TRACE(jh, "entry");
+        if (is_handle_aborted(handle))
+                goto out;
+
+        jbd_lock_bh_state(bh);
+
+        if (jh->b_modified == 0) {
+                /*
+                 * This buffer's got modified and becoming part
+                 * of the transaction. This needs to be done
+                 * once a transaction -bzzz
+                 */
+                jh->b_modified = 1;
+                J_ASSERT_JH(jh, handle->h_buffer_credits > 0);
+                handle->h_buffer_credits--;
+        }
+
+        /*
+         * fastpath, to avoid expensive locking.  If this buffer is already
+         * on the running transaction's metadata list there is nothing to do.
+         * Nobody can take it off again because there is a handle open.
+         * I _think_ we're OK here with SMP barriers - a mistaken decision will
+         * result in this test being false, so we go in and take the locks.
+         */
+        if (jh->b_transaction == transaction && jh->b_jlist == BJ_Metadata) {
+                JBUFFER_TRACE(jh, "fastpath");
+                J_ASSERT_JH(jh, jh->b_transaction ==
+                                        journal->j_running_transaction);
+                goto out_unlock_bh;
+        }
+
+        set_buffer_jbddirty(bh);
+
+        /*
+         * Metadata already on the current transaction list doesn't
+         * need to be filed.  Metadata on another transaction's list must
+         * be committing, and will be refiled once the commit completes:
+         * leave it alone for now.
+         */
+        if (jh->b_transaction != transaction) {
+                JBUFFER_TRACE(jh, "already on other transaction");
+                J_ASSERT_JH(jh, jh->b_transaction ==
+                                        journal->j_committing_transaction);
+                J_ASSERT_JH(jh, jh->b_next_transaction == transaction);
+                /* And this case is illegal: we can't reuse another
+                 * transaction's data buffer, ever. */
+                goto out_unlock_bh;
+        }
+
+        /* That test should have eliminated the following case: */
+        J_ASSERT_JH(jh, jh->b_frozen_data == 0);
+
+        JBUFFER_TRACE(jh, "file as BJ_Metadata");
+        spin_lock(&journal->j_list_lock);
+        __journal_file_buffer(jh, handle->h_transaction, BJ_Metadata);
+        spin_unlock(&journal->j_list_lock);
+out_unlock_bh:
+        jbd_unlock_bh_state(bh);
+out:
+        JBUFFER_TRACE(jh, "exit");
+        return 0;
+}
+
+/*
+ * journal_release_buffer: undo a get_write_access without any buffer
+ * updates, if the update decided in the end that it didn't need access.
+ *
+ */
+void
+journal_release_buffer(handle_t *handle, struct buffer_head *bh)
+{
+        BUFFER_TRACE(bh, "entry");
+}
+
+/**
+ * void journal_forget() - bforget() for potentially-journaled buffers.
+ * @handle: transaction handle
+ * @bh:     bh to 'forget'
+ *
+ * We can only do the bforget if there are no commits pending against the
+ * buffer.  If the buffer is dirty in the current running transaction we
+ * can safely unlink it.
+ *
+ * bh may not be a journalled buffer at all - it may be a non-JBD
+ * buffer which came off the hashtable.  Check for this.
+ *
+ * Decrements bh->b_count by one.
+ *
+ * Allow this call even if the handle has aborted --- it may be part of
+ * the caller's cleanup after an abort.
+ */
+int journal_forget (handle_t *handle, struct buffer_head *bh)
+{
+        transaction_t *transaction = handle->h_transaction;
+        journal_t *journal = transaction->t_journal;
+        struct journal_head *jh;
+        int drop_reserve = 0;
+        int err = 0;
+
+        BUFFER_TRACE(bh, "entry");
+
+        jbd_lock_bh_state(bh);
+        spin_lock(&journal->j_list_lock);
+
+        if (!buffer_jbd(bh))
+                goto not_jbd;
+        jh = bh2jh(bh);
+
+        /* Critical error: attempting to delete a bitmap buffer, maybe?
+         * Don't do any jbd operations, and return an error. */
+        if (!J_EXPECT_JH(jh, !jh->b_committed_data,
+                         "inconsistent data on disk")) {
+                err = -EIO;
+                goto not_jbd;
+        }
+
+        /*
+         * The buffer's going from the transaction, we must drop
+         * all references -bzzz
+         */
+        jh->b_modified = 0;
+
+        if (jh->b_transaction == handle->h_transaction) {
+                J_ASSERT_JH(jh, !jh->b_frozen_data);
+
+                /* If we are forgetting a buffer which is already part
+                 * of this transaction, then we can just drop it from
+                 * the transaction immediately. */
+                clear_buffer_dirty(bh);
+                clear_buffer_jbddirty(bh);
+
+                JBUFFER_TRACE(jh, "belongs to current transaction: unfile");
+
+                drop_reserve = 1;
+
+                /*
+                 * We are no longer going to journal this buffer.
+                 * However, the commit of this transaction is still
+                 * important to the buffer: the delete that we are now
+                 * processing might obsolete an old log entry, so by
+                 * committing, we can satisfy the buffer's checkpoint.
+                 *
+                 * So, if we have a checkpoint on the buffer, we should
+                 * now refile the buffer on our BJ_Forget list so that
+                 * we know to remove the checkpoint after we commit.
+                 */
+
+                if (jh->b_cp_transaction) {
+                        __journal_temp_unlink_buffer(jh);
+                        __journal_file_buffer(jh, transaction, BJ_Forget);
+                } else {
+                        __journal_unfile_buffer(jh);
+                        journal_remove_journal_head(bh);
+                        __brelse(bh);
+                        if (!buffer_jbd(bh)) {
+                                spin_unlock(&journal->j_list_lock);
+                                jbd_unlock_bh_state(bh);
+                                __bforget(bh);
+                                goto drop;
+                        }
+                }
+        } else if (jh->b_transaction) {
+                J_ASSERT_JH(jh, (jh->b_transaction ==
+                                 journal->j_committing_transaction));
+                /* However, if the buffer is still owned by a prior
+                 * (committing) transaction, we can't drop it yet... */
+                JBUFFER_TRACE(jh, "belongs to older transaction");
+                /* ... but we CAN drop it from the new transaction if we
+                 * have also modified it since the original commit. */
+
+                if (jh->b_next_transaction) {
+                        J_ASSERT(jh->b_next_transaction == transaction);
+                        jh->b_next_transaction = NULL;
+                        drop_reserve = 1;
+                }
+        }
+
+not_jbd:
+        spin_unlock(&journal->j_list_lock);
+        jbd_unlock_bh_state(bh);
+        __brelse(bh);
+drop:
+        if (drop_reserve) {
+                /* no need to reserve log space for this block -bzzz */
+                handle->h_buffer_credits++;
+        }
+        return err;
+}
+
+/**
+ * int journal_stop() - complete a transaction
+ * @handle: tranaction to complete.
+ *
+ * All done for a particular handle.
+ *
+ * There is not much action needed here.  We just return any remaining
+ * buffer credits to the transaction and remove the handle.  The only
+ * complication is that we need to start a commit operation if the
+ * filesystem is marked for synchronous update.
+ *
+ * journal_stop itself will not usually return an error, but it may
+ * do so in unusual circumstances.  In particular, expect it to
+ * return -EIO if a journal_abort has been executed since the
+ * transaction began.
+ */
+int journal_stop(handle_t *handle)
+{
+        transaction_t *transaction = handle->h_transaction;
+        journal_t *journal = transaction->t_journal;
+        int old_handle_count, err;
+        pid_t pid;
+
+        J_ASSERT(transaction->t_updates > 0);
+        J_ASSERT(journal_current_handle() == handle);
+
+        if (is_handle_aborted(handle))
+                err = -EIO;
+        else
+                err = 0;
+
+        if (--handle->h_ref > 0) {
+                jbd_debug(4, "h_ref %d -> %d\n", handle->h_ref + 1,
+                          handle->h_ref);
+                return err;
+        }
+
+        jbd_debug(4, "Handle %p going down\n", handle);
+
+        /*
+         * Implement synchronous transaction batching.  If the handle
+         * was synchronous, don't force a commit immediately.  Let's
+         * yield and let another thread piggyback onto this transaction.
+         * Keep doing that while new threads continue to arrive.
+         * It doesn't cost much - we're about to run a commit and sleep
+         * on IO anyway.  Speeds up many-threaded, many-dir operations
+         * by 30x or more...
+         *
+         * But don't do this if this process was the most recent one to
+         * perform a synchronous write.  We do this to detect the case where a
+         * single process is doing a stream of sync writes.  No point in waiting
+         * for joiners in that case.
+         */
+        pid = current->pid;
+        if (handle->h_sync && journal->j_last_sync_writer != pid) {
+                journal->j_last_sync_writer = pid;
+                do {
+                        old_handle_count = transaction->t_handle_count;
+                        schedule_timeout_uninterruptible(1);
+                } while (old_handle_count != transaction->t_handle_count);
+        }
+
+        current->journal_info = NULL;
+        spin_lock(&journal->j_state_lock);
+        spin_lock(&transaction->t_handle_lock);
+        transaction->t_outstanding_credits -= handle->h_buffer_credits;
+        transaction->t_updates--;
+        if (!transaction->t_updates) {
+                wake_up(&journal->j_wait_updates);
+                if (journal->j_barrier_count)
+                        wake_up(&journal->j_wait_transaction_locked);
+        }
+
+        /*
+         * If the handle is marked SYNC, we need to set another commit
+         * going!  We also want to force a commit if the current
+         * transaction is occupying too much of the log, or if the
+         * transaction is too old now.
+         */
+        if (handle->h_sync ||
+                        transaction->t_outstanding_credits >
+                                journal->j_max_transaction_buffers ||
+                        time_after_eq(jiffies, transaction->t_expires)) {
+                /* Do this even for aborted journals: an abort still
+                 * completes the commit thread, it just doesn't write
+                 * anything to disk. */
+                tid_t tid = transaction->t_tid;
+
+                spin_unlock(&transaction->t_handle_lock);
+                jbd_debug(2, "transaction too old, requesting commit for "
+                                        "handle %p\n", handle);
+                /* This is non-blocking */
+                __log_start_commit(journal, transaction->t_tid);
+                spin_unlock(&journal->j_state_lock);
+
+                /*
+                 * Special case: JFS_SYNC synchronous updates require us
+                 * to wait for the commit to complete.
+                 */
+                if (handle->h_sync && !(current->flags & PF_MEMALLOC))
+                        err = log_wait_commit(journal, tid);
+        } else {
+                spin_unlock(&transaction->t_handle_lock);
+                spin_unlock(&journal->j_state_lock);
+        }
+
+        jbd_free_handle(handle);
+        return err;
+}
+
+/**int journal_force_commit() - force any uncommitted transactions
+ * @journal: journal to force
+ *
+ * For synchronous operations: force any uncommitted transactions
+ * to disk.  May seem kludgy, but it reuses all the handle batching
+ * code in a very simple manner.
+ */
+int journal_force_commit(journal_t *journal)
+{
+        handle_t *handle;
+        int ret;
+
+        handle = journal_start(journal, 1);
+        if (IS_ERR(handle)) {
+                ret = PTR_ERR(handle);
+        } else {
+                handle->h_sync = 1;
+                ret = journal_stop(handle);
+        }
+        return ret;
+}
+
+/*
+ *
+ * List management code snippets: various functions for manipulating the
+ * transaction buffer lists.
+ *
+ */
+
+/*
+ * Append a buffer to a transaction list, given the transaction's list head
+ * pointer.
+ *
+ * j_list_lock is held.
+ *
+ * jbd_lock_bh_state(jh2bh(jh)) is held.
+ */
+
+static inline void
+__blist_add_buffer(struct journal_head **list, struct journal_head *jh)
+{
+        if (!*list) {
+                jh->b_tnext = jh->b_tprev = jh;
+                *list = jh;
+        } else {
+                /* Insert at the tail of the list to preserve order */
+                struct journal_head *first = *list, *last = first->b_tprev;
+                jh->b_tprev = last;
+                jh->b_tnext = first;
+                last->b_tnext = first->b_tprev = jh;
+        }
+}
+
+/*
+ * Remove a buffer from a transaction list, given the transaction's list
+ * head pointer.
+ *
+ * Called with j_list_lock held, and the journal may not be locked.
+ *
+ * jbd_lock_bh_state(jh2bh(jh)) is held.
+ */
+
+static inline void
+__blist_del_buffer(struct journal_head **list, struct journal_head *jh)
+{
+        if (*list == jh) {
+                *list = jh->b_tnext;
+                if (*list == jh)
+                        *list = NULL;
+        }
+        jh->b_tprev->b_tnext = jh->b_tnext;
+        jh->b_tnext->b_tprev = jh->b_tprev;
+}
+
+/*
+ * Remove a buffer from the appropriate transaction list.
+ *
+ * Note that this function can *change* the value of
+ * bh->b_transaction->t_sync_datalist, t_buffers, t_forget,
+ * t_iobuf_list, t_shadow_list, t_log_list or t_reserved_list.  If the caller
+ * is holding onto a copy of one of thee pointers, it could go bad.
+ * Generally the caller needs to re-read the pointer from the transaction_t.
+ *
+ * Called under j_list_lock.  The journal may not be locked.
+ */
+void __journal_temp_unlink_buffer(struct journal_head *jh)
+{
+        struct journal_head **list = NULL;
+        transaction_t *transaction;
+        struct buffer_head *bh = jh2bh(jh);
+
+        J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
+        transaction = jh->b_transaction;
+        if (transaction)
+                assert_spin_locked(&transaction->t_journal->j_list_lock);
+
+        J_ASSERT_JH(jh, jh->b_jlist < BJ_Types);
+        if (jh->b_jlist != BJ_None)
+                J_ASSERT_JH(jh, transaction != 0);
+
+        switch (jh->b_jlist) {
+        case BJ_None:
+                return;
+        case BJ_SyncData:
+                list = &transaction->t_sync_datalist;
+                break;
+        case BJ_Metadata:
+                transaction->t_nr_buffers--;
+                J_ASSERT_JH(jh, transaction->t_nr_buffers >= 0);
+                list = &transaction->t_buffers;
+                break;
+        case BJ_Forget:
+                list = &transaction->t_forget;
+                break;
+        case BJ_IO:
+                list = &transaction->t_iobuf_list;
+                break;
+        case BJ_Shadow:
+                list = &transaction->t_shadow_list;
+                break;
+        case BJ_LogCtl:
+                list = &transaction->t_log_list;
+                break;
+        case BJ_Reserved:
+                list = &transaction->t_reserved_list;
+                break;
+        case BJ_Locked:
+                list = &transaction->t_locked_list;
+                break;
+        }
+
+        __blist_del_buffer(list, jh);
+        jh->b_jlist = BJ_None;
+        if (test_clear_buffer_jbddirty(bh))
+                mark_buffer_dirty(bh);  /* Expose it to the VM */
+}
+
+void __journal_unfile_buffer(struct journal_head *jh)
+{
+        __journal_temp_unlink_buffer(jh);
+        jh->b_transaction = NULL;
+}
+
+void journal_unfile_buffer(journal_t *journal, struct journal_head *jh)
+{
+        jbd_lock_bh_state(jh2bh(jh));
+        spin_lock(&journal->j_list_lock);
+        __journal_unfile_buffer(jh);
+        spin_unlock(&journal->j_list_lock);
+        jbd_unlock_bh_state(jh2bh(jh));
+}
+
+/*
+ * Called from journal_try_to_free_buffers().
+ *
+ * Called under jbd_lock_bh_state(bh)
+ */
+static void
+__journal_try_to_free_buffer(journal_t *journal, struct buffer_head *bh)
+{
+        struct journal_head *jh;
+
+        jh = bh2jh(bh);
+
+        if (buffer_locked(bh) || buffer_dirty(bh))
+                goto out;
+
+        if (jh->b_next_transaction != 0)
+                goto out;
+
+        spin_lock(&journal->j_list_lock);
+        if (jh->b_transaction != 0 && jh->b_cp_transaction == 0) {
+                if (jh->b_jlist == BJ_SyncData || jh->b_jlist == BJ_Locked) {
+                        /* A written-back ordered data buffer */
+                        JBUFFER_TRACE(jh, "release data");
+                        __journal_unfile_buffer(jh);
+                        journal_remove_journal_head(bh);
+                        __brelse(bh);
+                }
+        } else if (jh->b_cp_transaction != 0 && jh->b_transaction == 0) {
+                /* written-back checkpointed metadata buffer */
+                if (jh->b_jlist == BJ_None) {
+                        JBUFFER_TRACE(jh, "remove from checkpoint list");
+                        __journal_remove_checkpoint(jh);
+                        journal_remove_journal_head(bh);
+                        __brelse(bh);
+                }
+        }
+        spin_unlock(&journal->j_list_lock);
+out:
+        return;
+}
+
+
+/**
+ * int journal_try_to_free_buffers() - try to free page buffers.
+ * @journal: journal for operation
+ * @page: to try and free
+ * @unused_gfp_mask: unused
+ *
+ *
+ * For all the buffers on this page,
+ * if they are fully written out ordered data, move them onto BUF_CLEAN
+ * so try_to_free_buffers() can reap them.
+ *
+ * This function returns non-zero if we wish try_to_free_buffers()
+ * to be called. We do this if the page is releasable by try_to_free_buffers().
+ * We also do it if the page has locked or dirty buffers and the caller wants
+ * us to perform sync or async writeout.
+ *
+ * This complicates JBD locking somewhat.  We aren't protected by the
+ * BKL here.  We wish to remove the buffer from its committing or
+ * running transaction's ->t_datalist via __journal_unfile_buffer.
+ *
+ * This may *change* the value of transaction_t->t_datalist, so anyone
+ * who looks at t_datalist needs to lock against this function.
+ *
+ * Even worse, someone may be doing a journal_dirty_data on this
+ * buffer.  So we need to lock against that.  journal_dirty_data()
+ * will come out of the lock with the buffer dirty, which makes it
+ * ineligible for release here.
+ *
+ * Who else is affected by this?  hmm...  Really the only contender
+ * is do_get_write_access() - it could be looking at the buffer while
+ * journal_try_to_free_buffer() is changing its state.  But that
+ * cannot happen because we never reallocate freed data as metadata
+ * while the data is part of a transaction.  Yes?
+ */
+int journal_try_to_free_buffers(journal_t *journal,
+                                struct page *page, gfp_t unused_gfp_mask)
+{
+        struct buffer_head *head;
+        struct buffer_head *bh;
+        int ret = 0;
+
+        J_ASSERT(PageLocked(page));
+
+        head = page_buffers(page);
+        bh = head;
+        do {
+                struct journal_head *jh;
+
+                /*
+                 * We take our own ref against the journal_head here to avoid
+                 * having to add tons of locking around each instance of
+                 * journal_remove_journal_head() and journal_put_journal_head().
+                 */
+                jh = journal_grab_journal_head(bh);
+                if (!jh)
+                        continue;
+
+                jbd_lock_bh_state(bh);
+                __journal_try_to_free_buffer(journal, bh);
+                journal_put_journal_head(jh);
+                jbd_unlock_bh_state(bh);
+                if (buffer_jbd(bh))
+                        goto busy;
+        } while ((bh = bh->b_this_page) != head);
+        ret = try_to_free_buffers(page);
+busy:
+        return ret;
+}
+
+/*
+ * This buffer is no longer needed.  If it is on an older transaction's
+ * checkpoint list we need to record it on this transaction's forget list
+ * to pin this buffer (and hence its checkpointing transaction) down until
+ * this transaction commits.  If the buffer isn't on a checkpoint list, we
+ * release it.
+ * Returns non-zero if JBD no longer has an interest in the buffer.
+ *
+ * Called under j_list_lock.
+ *
+ * Called under jbd_lock_bh_state(bh).
+ */
+static int __dispose_buffer(struct journal_head *jh, transaction_t *transaction)
+{
+        int may_free = 1;
+        struct buffer_head *bh = jh2bh(jh);
+
+        __journal_unfile_buffer(jh);
+
+        if (jh->b_cp_transaction) {
+                JBUFFER_TRACE(jh, "on running+cp transaction");
+                __journal_file_buffer(jh, transaction, BJ_Forget);
+                clear_buffer_jbddirty(bh);
+                may_free = 0;
+        } else {
+                JBUFFER_TRACE(jh, "on running transaction");
+                journal_remove_journal_head(bh);
+                __brelse(bh);
+        }
+        return may_free;
+}
+
+/*
+ * journal_invalidatepage
+ *
+ * This code is tricky.  It has a number of cases to deal with.
+ *
+ * There are two invariants which this code relies on:
+ *
+ * i_size must be updated on disk before we start calling invalidatepage on the
+ * data.
+ *
+ *  This is done in ext3 by defining an ext3_setattr method which
+ *  updates i_size before truncate gets going.  By maintaining this
+ *  invariant, we can be sure that it is safe to throw away any buffers
+ *  attached to the current transaction: once the transaction commits,
+ *  we know that the data will not be needed.
+ *
+ *  Note however that we can *not* throw away data belonging to the
+ *  previous, committing transaction!
+ *
+ * Any disk blocks which *are* part of the previous, committing
+ * transaction (and which therefore cannot be discarded immediately) are
+ * not going to be reused in the new running transaction
+ *
+ *  The bitmap committed_data images guarantee this: any block which is
+ *  allocated in one transaction and removed in the next will be marked
+ *  as in-use in the committed_data bitmap, so cannot be reused until
+ *  the next transaction to delete the block commits.  This means that
+ *  leaving committing buffers dirty is quite safe: the disk blocks
+ *  cannot be reallocated to a different file and so buffer aliasing is
+ *  not possible.
+ *
+ *
+ * The above applies mainly to ordered data mode.  In writeback mode we
+ * don't make guarantees about the order in which data hits disk --- in
+ * particular we don't guarantee that new dirty data is flushed before
+ * transaction commit --- so it is always safe just to discard data
+ * immediately in that mode.  --sct
+ */
+
+/*
+ * The journal_unmap_buffer helper function returns zero if the buffer
+ * concerned remains pinned as an anonymous buffer belonging to an older
+ * transaction.
+ *
+ * We're outside-transaction here.  Either or both of j_running_transaction
+ * and j_committing_transaction may be NULL.
+ */
+static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh)
+{
+        transaction_t *transaction;
+        struct journal_head *jh;
+        int may_free = 1;
+        int ret;
+
+        BUFFER_TRACE(bh, "entry");
+
+        /*
+         * It is safe to proceed here without the j_list_lock because the
+         * buffers cannot be stolen by try_to_free_buffers as long as we are
+         * holding the page lock. --sct
+         */
+
+        if (!buffer_jbd(bh))
+                goto zap_buffer_unlocked;
+
+        spin_lock(&journal->j_state_lock);
+        jbd_lock_bh_state(bh);
+        spin_lock(&journal->j_list_lock);
+
+        jh = journal_grab_journal_head(bh);
+        if (!jh)
+                goto zap_buffer_no_jh;
+
+        transaction = jh->b_transaction;
+        if (transaction == NULL) {
+                /* First case: not on any transaction.  If it
+                 * has no checkpoint link, then we can zap it:
+                 * it's a writeback-mode buffer so we don't care
+                 * if it hits disk safely. */
+                if (!jh->b_cp_transaction) {
+                        JBUFFER_TRACE(jh, "not on any transaction: zap");
+                        goto zap_buffer;
+                }
+
+                if (!buffer_dirty(bh)) {
+                        /* bdflush has written it.  We can drop it now */
+                        goto zap_buffer;
+                }
+
+                /* OK, it must be in the journal but still not
+                 * written fully to disk: it's metadata or
+                 * journaled data... */
+
+                if (journal->j_running_transaction) {
+                        /* ... and once the current transaction has
+                         * committed, the buffer won't be needed any
+                         * longer. */
+                        JBUFFER_TRACE(jh, "checkpointed: add to BJ_Forget");
+                        ret = __dispose_buffer(jh,
+                                        journal->j_running_transaction);
+                        journal_put_journal_head(jh);
+                        spin_unlock(&journal->j_list_lock);
+                        jbd_unlock_bh_state(bh);
+                        spin_unlock(&journal->j_state_lock);
+                        return ret;
+                } else {
+                        /* There is no currently-running transaction. So the
+                         * orphan record which we wrote for this file must have
+                         * passed into commit.  We must attach this buffer to
+                         * the committing transaction, if it exists. */
+                        if (journal->j_committing_transaction) {
+                                JBUFFER_TRACE(jh, "give to committing trans");
+                                ret = __dispose_buffer(jh,
+                                        journal->j_committing_transaction);
+                                journal_put_journal_head(jh);
+                                spin_unlock(&journal->j_list_lock);
+                                jbd_unlock_bh_state(bh);
+                                spin_unlock(&journal->j_state_lock);
+                                return ret;
+                        } else {
+                                /* The orphan record's transaction has
+                                 * committed.  We can cleanse this buffer */
+                                clear_buffer_jbddirty(bh);
+                                goto zap_buffer;
+                        }
+                }
+        } else if (transaction == journal->j_committing_transaction) {
+                if (jh->b_jlist == BJ_Locked) {
+                        /*
+                         * The buffer is on the committing transaction's locked
+                         * list.  We have the buffer locked, so I/O has
+                         * completed.  So we can nail the buffer now.
+                         */
+                        may_free = __dispose_buffer(jh, transaction);
+                        goto zap_buffer;
+                }
+                /*
+                 * If it is committing, we simply cannot touch it.  We
+                 * can remove it's next_transaction pointer from the
+                 * running transaction if that is set, but nothing
+                 * else. */
+                JBUFFER_TRACE(jh, "on committing transaction");
+                set_buffer_freed(bh);
+                if (jh->b_next_transaction) {
+                        J_ASSERT(jh->b_next_transaction ==
+                                        journal->j_running_transaction);
+                        jh->b_next_transaction = NULL;
+                }
+                journal_put_journal_head(jh);
+                spin_unlock(&journal->j_list_lock);
+                jbd_unlock_bh_state(bh);
+                spin_unlock(&journal->j_state_lock);
+                return 0;
+        } else {
+                /* Good, the buffer belongs to the running transaction.
+                 * We are writing our own transaction's data, not any
+                 * previous one's, so it is safe to throw it away
+                 * (remember that we expect the filesystem to have set
+                 * i_size already for this truncate so recovery will not
+                 * expose the disk blocks we are discarding here.) */
+                J_ASSERT_JH(jh, transaction == journal->j_running_transaction);
+                may_free = __dispose_buffer(jh, transaction);
+        }
+
+zap_buffer:
+        journal_put_journal_head(jh);
+zap_buffer_no_jh:
+        spin_unlock(&journal->j_list_lock);
+        jbd_unlock_bh_state(bh);
+        spin_unlock(&journal->j_state_lock);
+zap_buffer_unlocked:
+        clear_buffer_dirty(bh);
+        J_ASSERT_BH(bh, !buffer_jbddirty(bh));
+        clear_buffer_mapped(bh);
+        clear_buffer_req(bh);
+        clear_buffer_new(bh);
+        bh->b_bdev = NULL;
+        return may_free;
+}
+
+/**
+ * void journal_invalidatepage()
+ * @journal: journal to use for flush...
+ * @page:    page to flush
+ * @offset:  length of page to invalidate.
+ *
+ * Reap page buffers containing data after offset in page.
+ *
+ */
+void journal_invalidatepage(journal_t *journal,
+                      struct page *page,
+                      unsigned long offset)
+{
+        struct buffer_head *head, *bh, *next;
+        unsigned int curr_off = 0;
+        int may_free = 1;
+
+        if (!PageLocked(page))
+                BUG();
+        if (!page_has_buffers(page))
+                return;
+
+        /* We will potentially be playing with lists other than just the
+         * data lists (especially for journaled data mode), so be
+         * cautious in our locking. */
+
+        head = bh = page_buffers(page);
+        do {
+                unsigned int next_off = curr_off + bh->b_size;
+                next = bh->b_this_page;
+
+                if (offset <= curr_off) {
+                        /* This block is wholly outside the truncation point */
+                        lock_buffer(bh);
+                        may_free &= journal_unmap_buffer(journal, bh);
+                        unlock_buffer(bh);
+                }
+                curr_off = next_off;
+                bh = next;
+
+        } while (bh != head);
+
+        if (!offset) {
+                if (may_free && try_to_free_buffers(page))
+                        J_ASSERT(!page_has_buffers(page));
+        }
+}
+
+/*
+ * File a buffer on the given transaction list.
+ */
+void __journal_file_buffer(struct journal_head *jh,
+                        transaction_t *transaction, int jlist)
+{
+        struct journal_head **list = NULL;
+        int was_dirty = 0;
+        struct buffer_head *bh = jh2bh(jh);
+
+        J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
+        assert_spin_locked(&transaction->t_journal->j_list_lock);
+
+        J_ASSERT_JH(jh, jh->b_jlist < BJ_Types);
+        J_ASSERT_JH(jh, jh->b_transaction == transaction ||
+                                jh->b_transaction == 0);
+
+        if (jh->b_transaction && jh->b_jlist == jlist)
+                return;
+
+        /* The following list of buffer states needs to be consistent
+         * with __jbd_unexpected_dirty_buffer()'s handling of dirty
+         * state. */
+
+        if (jlist == BJ_Metadata || jlist == BJ_Reserved ||
+            jlist == BJ_Shadow || jlist == BJ_Forget) {
+                if (test_clear_buffer_dirty(bh) ||
+                    test_clear_buffer_jbddirty(bh))
+                        was_dirty = 1;
+        }
+
+        if (jh->b_transaction)
+                __journal_temp_unlink_buffer(jh);
+        jh->b_transaction = transaction;
+
+        switch (jlist) {
+        case BJ_None:
+                J_ASSERT_JH(jh, !jh->b_committed_data);
+                J_ASSERT_JH(jh, !jh->b_frozen_data);
+                return;
+        case BJ_SyncData:
+                list = &transaction->t_sync_datalist;
+                break;
+        case BJ_Metadata:
+                transaction->t_nr_buffers++;
+                list = &transaction->t_buffers;
+                break;
+        case BJ_Forget:
+                list = &transaction->t_forget;
+                break;
+        case BJ_IO:
+                list = &transaction->t_iobuf_list;
+                break;
+        case BJ_Shadow:
+                list = &transaction->t_shadow_list;
+                break;
+        case BJ_LogCtl:
+                list = &transaction->t_log_list;
+                break;
+        case BJ_Reserved:
+                list = &transaction->t_reserved_list;
+                break;
+        case BJ_Locked:
+                list =  &transaction->t_locked_list;
+                break;
+        }
+
+        __blist_add_buffer(list, jh);
+        jh->b_jlist = jlist;
+
+        if (was_dirty)
+                set_buffer_jbddirty(bh);
+}
+
+void journal_file_buffer(struct journal_head *jh,
+                                transaction_t *transaction, int jlist)
+{
+        jbd_lock_bh_state(jh2bh(jh));
+        spin_lock(&transaction->t_journal->j_list_lock);
+        __journal_file_buffer(jh, transaction, jlist);
+        spin_unlock(&transaction->t_journal->j_list_lock);
+        jbd_unlock_bh_state(jh2bh(jh));
+}
+
+/*
+ * Remove a buffer from its current buffer list in preparation for
+ * dropping it from its current transaction entirely.  If the buffer has
+ * already started to be used by a subsequent transaction, refile the
+ * buffer on that transaction's metadata list.
+ *
+ * Called under journal->j_list_lock
+ *
+ * Called under jbd_lock_bh_state(jh2bh(jh))
+ */
+void __journal_refile_buffer(struct journal_head *jh)
+{
+        int was_dirty;
+        struct buffer_head *bh = jh2bh(jh);
+
+        J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
+        if (jh->b_transaction)
+                assert_spin_locked(&jh->b_transaction->t_journal->j_list_lock);
+
+        /* If the buffer is now unused, just drop it. */
+        if (jh->b_next_transaction == NULL) {
+                __journal_unfile_buffer(jh);
+                return;
+        }
+
+        /*
+         * It has been modified by a later transaction: add it to the new
+         * transaction's metadata list.
+         */
+
+        was_dirty = test_clear_buffer_jbddirty(bh);
+        __journal_temp_unlink_buffer(jh);
+        jh->b_transaction = jh->b_next_transaction;
+        jh->b_next_transaction = NULL;
+        __journal_file_buffer(jh, jh->b_transaction,
+                                was_dirty ? BJ_Metadata : BJ_Reserved);
+        J_ASSERT_JH(jh, jh->b_transaction->t_state == T_RUNNING);
+
+        if (was_dirty)
+                set_buffer_jbddirty(bh);
+}
+
+/*
+ * For the unlocked version of this call, also make sure that any
+ * hanging journal_head is cleaned up if necessary.
+ *
+ * __journal_refile_buffer is usually called as part of a single locked
+ * operation on a buffer_head, in which the caller is probably going to
+ * be hooking the journal_head onto other lists.  In that case it is up
+ * to the caller to remove the journal_head if necessary.  For the
+ * unlocked journal_refile_buffer call, the caller isn't going to be
+ * doing anything else to the buffer so we need to do the cleanup
+ * ourselves to avoid a jh leak.
+ *
+ * *** The journal_head may be freed by this call! ***
+ */
+void journal_refile_buffer(journal_t *journal, struct journal_head *jh)
+{
+        struct buffer_head *bh = jh2bh(jh);
+
+        jbd_lock_bh_state(bh);
+        spin_lock(&journal->j_list_lock);
+
+        __journal_refile_buffer(jh);
+        jbd_unlock_bh_state(bh);
+        journal_remove_journal_head(bh);
+
+        spin_unlock(&journal->j_list_lock);
+        __brelse(bh);
+}