1 files changed, 844 insertions, 0 deletions

diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
new file mode 100644
index 000000000000..dac720c837ab
--- /dev/null
+++ b/fs/jbd/commit.c
@@ -0,0 +1,844 @@
+/*
+ * linux/fs/commit.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.
+ *
+ * Journal commit routines for the generic filesystem journaling code;
+ * part of the ext2fs journaling system.
+ */
+
+#include <linux/time.h>
+#include <linux/fs.h>
+#include <linux/jbd.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/smp_lock.h>
+
+/*
+ * Default IO end handler for temporary BJ_IO buffer_heads.
+ */
+static void journal_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
+{
+        BUFFER_TRACE(bh, "");
+        if (uptodate)
+                set_buffer_uptodate(bh);
+        else
+                clear_buffer_uptodate(bh);
+        unlock_buffer(bh);
+}
+
+/*
+ * When an ext3-ordered file is truncated, it is possible that many pages are
+ * not sucessfully freed, because they are attached to a committing transaction.
+ * After the transaction commits, these pages are left on the LRU, with no
+ * ->mapping, and with attached buffers.  These pages are trivially reclaimable
+ * by the VM, but their apparent absence upsets the VM accounting, and it makes
+ * the numbers in /proc/meminfo look odd.
+ *
+ * So here, we have a buffer which has just come off the forget list.  Look to
+ * see if we can strip all buffers from the backing page.
+ *
+ * Called under lock_journal(), and possibly under journal_datalist_lock.  The
+ * caller provided us with a ref against the buffer, and we drop that here.
+ */
+static void release_buffer_page(struct buffer_head *bh)
+{
+        struct page *page;
+
+        if (buffer_dirty(bh))
+                goto nope;
+        if (atomic_read(&bh->b_count) != 1)
+                goto nope;
+        page = bh->b_page;
+        if (!page)
+                goto nope;
+        if (page->mapping)
+                goto nope;
+
+        /* OK, it's a truncated page */
+        if (TestSetPageLocked(page))
+                goto nope;
+
+        page_cache_get(page);
+        __brelse(bh);
+        try_to_free_buffers(page);
+        unlock_page(page);
+        page_cache_release(page);
+        return;
+
+nope:
+        __brelse(bh);
+}
+
+/*
+ * Try to acquire jbd_lock_bh_state() against the buffer, when j_list_lock is
+ * held.  For ranking reasons we must trylock.  If we lose, schedule away and
+ * return 0.  j_list_lock is dropped in this case.
+ */
+static int inverted_lock(journal_t *journal, struct buffer_head *bh)
+{
+        if (!jbd_trylock_bh_state(bh)) {
+                spin_unlock(&journal->j_list_lock);
+                schedule();
+                return 0;
+        }
+        return 1;
+}
+
+/* Done it all: now write the commit record.  We should have
+ * cleaned up our previous buffers by now, so if we are in abort
+ * mode we can now just skip the rest of the journal write
+ * entirely.
+ *
+ * Returns 1 if the journal needs to be aborted or 0 on success
+ */
+static int journal_write_commit_record(journal_t *journal,
+                                        transaction_t *commit_transaction)
+{
+        struct journal_head *descriptor;
+        struct buffer_head *bh;
+        int i, ret;
+        int barrier_done = 0;
+
+        if (is_journal_aborted(journal))
+                return 0;
+
+        descriptor = journal_get_descriptor_buffer(journal);
+        if (!descriptor)
+                return 1;
+
+        bh = jh2bh(descriptor);
+
+        /* AKPM: buglet - add `i' to tmp! */
+        for (i = 0; i < bh->b_size; i += 512) {
+                journal_header_t *tmp = (journal_header_t*)bh->b_data;
+                tmp->h_magic = cpu_to_be32(JFS_MAGIC_NUMBER);
+                tmp->h_blocktype = cpu_to_be32(JFS_COMMIT_BLOCK);
+                tmp->h_sequence = cpu_to_be32(commit_transaction->t_tid);
+        }
+
+        JBUFFER_TRACE(descriptor, "write commit block");
+        set_buffer_dirty(bh);
+        if (journal->j_flags & JFS_BARRIER) {
+                set_buffer_ordered(bh);
+                barrier_done = 1;
+        }
+        ret = sync_dirty_buffer(bh);
+        /* is it possible for another commit to fail at roughly
+         * the same time as this one?  If so, we don't want to
+         * trust the barrier flag in the super, but instead want
+         * to remember if we sent a barrier request
+         */
+        if (ret == -EOPNOTSUPP && barrier_done) {
+                char b[BDEVNAME_SIZE];
+
+                printk(KERN_WARNING
+                        "JBD: barrier-based sync failed on %s - "
+                        "disabling barriers\n",
+                        bdevname(journal->j_dev, b));
+                spin_lock(&journal->j_state_lock);
+                journal->j_flags &= ~JFS_BARRIER;
+                spin_unlock(&journal->j_state_lock);
+
+                /* And try again, without the barrier */
+                clear_buffer_ordered(bh);
+                set_buffer_uptodate(bh);
+                set_buffer_dirty(bh);
+                ret = sync_dirty_buffer(bh);
+        }
+        put_bh(bh);             /* One for getblk() */
+        journal_put_journal_head(descriptor);
+
+        return (ret == -EIO);
+}
+
+/*
+ * journal_commit_transaction
+ *
+ * The primary function for committing a transaction to the log.  This
+ * function is called by the journal thread to begin a complete commit.
+ */
+void journal_commit_transaction(journal_t *journal)
+{
+        transaction_t *commit_transaction;
+        struct journal_head *jh, *new_jh, *descriptor;
+        struct buffer_head **wbuf = journal->j_wbuf;
+        int bufs;
+        int flags;
+        int err;
+        unsigned long blocknr;
+        char *tagp = NULL;
+        journal_header_t *header;
+        journal_block_tag_t *tag = NULL;
+        int space_left = 0;
+        int first_tag = 0;
+        int tag_flag;
+        int i;
+
+        /*
+         * First job: lock down the current transaction and wait for
+         * all outstanding updates to complete.
+         */
+
+#ifdef COMMIT_STATS
+        spin_lock(&journal->j_list_lock);
+        summarise_journal_usage(journal);
+        spin_unlock(&journal->j_list_lock);
+#endif
+
+        /* Do we need to erase the effects of a prior journal_flush? */
+        if (journal->j_flags & JFS_FLUSHED) {
+                jbd_debug(3, "super block updated\n");
+                journal_update_superblock(journal, 1);
+        } else {
+                jbd_debug(3, "superblock not updated\n");
+        }
+
+        J_ASSERT(journal->j_running_transaction != NULL);
+        J_ASSERT(journal->j_committing_transaction == NULL);
+
+        commit_transaction = journal->j_running_transaction;
+        J_ASSERT(commit_transaction->t_state == T_RUNNING);
+
+        jbd_debug(1, "JBD: starting commit of transaction %d\n",
+                        commit_transaction->t_tid);
+
+        spin_lock(&journal->j_state_lock);
+        commit_transaction->t_state = T_LOCKED;
+
+        spin_lock(&commit_transaction->t_handle_lock);
+        while (commit_transaction->t_updates) {
+                DEFINE_WAIT(wait);
+
+                prepare_to_wait(&journal->j_wait_updates, &wait,
+                                        TASK_UNINTERRUPTIBLE);
+                if (commit_transaction->t_updates) {
+                        spin_unlock(&commit_transaction->t_handle_lock);
+                        spin_unlock(&journal->j_state_lock);
+                        schedule();
+                        spin_lock(&journal->j_state_lock);
+                        spin_lock(&commit_transaction->t_handle_lock);
+                }
+                finish_wait(&journal->j_wait_updates, &wait);
+        }
+        spin_unlock(&commit_transaction->t_handle_lock);
+
+        J_ASSERT (commit_transaction->t_outstanding_credits <=
+                        journal->j_max_transaction_buffers);
+
+        /*
+         * First thing we are allowed to do is to discard any remaining
+         * BJ_Reserved buffers.  Note, it is _not_ permissible to assume
+         * that there are no such buffers: if a large filesystem
+         * operation like a truncate needs to split itself over multiple
+         * transactions, then it may try to do a journal_restart() while
+         * there are still BJ_Reserved buffers outstanding.  These must
+         * be released cleanly from the current transaction.
+         *
+         * In this case, the filesystem must still reserve write access
+         * again before modifying the buffer in the new transaction, but
+         * we do not require it to remember exactly which old buffers it
+         * has reserved.  This is consistent with the existing behaviour
+         * that multiple journal_get_write_access() calls to the same
+         * buffer are perfectly permissable.
+         */
+        while (commit_transaction->t_reserved_list) {
+                jh = commit_transaction->t_reserved_list;
+                JBUFFER_TRACE(jh, "reserved, unused: refile");
+                /*
+                 * A journal_get_undo_access()+journal_release_buffer() may
+                 * leave undo-committed data.
+                 */
+                if (jh->b_committed_data) {
+                        struct buffer_head *bh = jh2bh(jh);
+
+                        jbd_lock_bh_state(bh);
+                        if (jh->b_committed_data) {
+                                kfree(jh->b_committed_data);
+                                jh->b_committed_data = NULL;
+                        }
+                        jbd_unlock_bh_state(bh);
+                }
+                journal_refile_buffer(journal, jh);
+        }
+
+        /*
+         * Now try to drop any written-back buffers from the journal's
+         * checkpoint lists.  We do this *before* commit because it potentially
+         * frees some memory
+         */
+        spin_lock(&journal->j_list_lock);
+        __journal_clean_checkpoint_list(journal);
+        spin_unlock(&journal->j_list_lock);
+
+        jbd_debug (3, "JBD: commit phase 1\n");
+
+        /*
+         * Switch to a new revoke table.
+         */
+        journal_switch_revoke_table(journal);
+
+        commit_transaction->t_state = T_FLUSH;
+        journal->j_committing_transaction = commit_transaction;
+        journal->j_running_transaction = NULL;
+        commit_transaction->t_log_start = journal->j_head;
+        wake_up(&journal->j_wait_transaction_locked);
+        spin_unlock(&journal->j_state_lock);
+
+        jbd_debug (3, "JBD: commit phase 2\n");
+
+        /*
+         * First, drop modified flag: all accesses to the buffers
+         * will be tracked for a new trasaction only -bzzz
+         */
+        spin_lock(&journal->j_list_lock);
+        if (commit_transaction->t_buffers) {
+                new_jh = jh = commit_transaction->t_buffers->b_tnext;
+                do {
+                        J_ASSERT_JH(new_jh, new_jh->b_modified == 1 ||
+                                        new_jh->b_modified == 0);
+                        new_jh->b_modified = 0;
+                        new_jh = new_jh->b_tnext;
+                } while (new_jh != jh);
+        }
+        spin_unlock(&journal->j_list_lock);
+
+        /*
+         * Now start flushing things to disk, in the order they appear
+         * on the transaction lists.  Data blocks go first.
+         */
+
+        err = 0;
+        /*
+         * Whenever we unlock the journal and sleep, things can get added
+         * onto ->t_sync_datalist, so we have to keep looping back to
+         * write_out_data until we *know* that the list is empty.
+         */
+        bufs = 0;
+        /*
+         * Cleanup any flushed data buffers from the data list.  Even in
+         * abort mode, we want to flush this out as soon as possible.
+         */
+write_out_data:
+        cond_resched();
+        spin_lock(&journal->j_list_lock);
+
+        while (commit_transaction->t_sync_datalist) {
+                struct buffer_head *bh;
+
+                jh = commit_transaction->t_sync_datalist;
+                commit_transaction->t_sync_datalist = jh->b_tnext;
+                bh = jh2bh(jh);
+                if (buffer_locked(bh)) {
+                        BUFFER_TRACE(bh, "locked");
+                        if (!inverted_lock(journal, bh))
+                                goto write_out_data;
+                        __journal_temp_unlink_buffer(jh);
+                        __journal_file_buffer(jh, commit_transaction,
+                                                BJ_Locked);
+                        jbd_unlock_bh_state(bh);
+                        if (lock_need_resched(&journal->j_list_lock)) {
+                                spin_unlock(&journal->j_list_lock);
+                                goto write_out_data;
+                        }
+                } else {
+                        if (buffer_dirty(bh)) {
+                                BUFFER_TRACE(bh, "start journal writeout");
+                                get_bh(bh);
+                                wbuf[bufs++] = bh;
+                                if (bufs == journal->j_wbufsize) {
+                                        jbd_debug(2, "submit %d writes\n",
+                                                        bufs);
+                                        spin_unlock(&journal->j_list_lock);
+                                        ll_rw_block(WRITE, bufs, wbuf);
+                                        journal_brelse_array(wbuf, bufs);
+                                        bufs = 0;
+                                        goto write_out_data;
+                                }
+                        } else {
+                                BUFFER_TRACE(bh, "writeout complete: unfile");
+                                if (!inverted_lock(journal, bh))
+                                        goto write_out_data;
+                                __journal_unfile_buffer(jh);
+                                jbd_unlock_bh_state(bh);
+                                journal_remove_journal_head(bh);
+                                put_bh(bh);
+                                if (lock_need_resched(&journal->j_list_lock)) {
+                                        spin_unlock(&journal->j_list_lock);
+                                        goto write_out_data;
+                                }
+                        }
+                }
+        }
+
+        if (bufs) {
+                spin_unlock(&journal->j_list_lock);
+                ll_rw_block(WRITE, bufs, wbuf);
+                journal_brelse_array(wbuf, bufs);
+                spin_lock(&journal->j_list_lock);
+        }
+
+        /*
+         * Wait for all previously submitted IO to complete.
+         */
+        while (commit_transaction->t_locked_list) {
+                struct buffer_head *bh;
+
+                jh = commit_transaction->t_locked_list->b_tprev;
+                bh = jh2bh(jh);
+                get_bh(bh);
+                if (buffer_locked(bh)) {
+                        spin_unlock(&journal->j_list_lock);
+                        wait_on_buffer(bh);
+                        if (unlikely(!buffer_uptodate(bh)))
+                                err = -EIO;
+                        spin_lock(&journal->j_list_lock);
+                }
+                if (!inverted_lock(journal, bh)) {
+                        put_bh(bh);
+                        spin_lock(&journal->j_list_lock);
+                        continue;
+                }
+                if (buffer_jbd(bh) && jh->b_jlist == BJ_Locked) {
+                        __journal_unfile_buffer(jh);
+                        jbd_unlock_bh_state(bh);
+                        journal_remove_journal_head(bh);
+                        put_bh(bh);
+                } else {
+                        jbd_unlock_bh_state(bh);
+                }
+                put_bh(bh);
+                cond_resched_lock(&journal->j_list_lock);
+        }
+        spin_unlock(&journal->j_list_lock);
+
+        if (err)
+                __journal_abort_hard(journal);
+
+        journal_write_revoke_records(journal, commit_transaction);
+
+        jbd_debug(3, "JBD: commit phase 2\n");
+
+        /*
+         * If we found any dirty or locked buffers, then we should have
+         * looped back up to the write_out_data label.  If there weren't
+         * any then journal_clean_data_list should have wiped the list
+         * clean by now, so check that it is in fact empty.
+         */
+        J_ASSERT (commit_transaction->t_sync_datalist == NULL);
+
+        jbd_debug (3, "JBD: commit phase 3\n");
+
+        /*
+         * Way to go: we have now written out all of the data for a
+         * transaction!  Now comes the tricky part: we need to write out
+         * metadata.  Loop over the transaction's entire buffer list:
+         */
+        commit_transaction->t_state = T_COMMIT;
+
+        descriptor = NULL;
+        bufs = 0;
+        while (commit_transaction->t_buffers) {
+
+                /* Find the next buffer to be journaled... */
+
+                jh = commit_transaction->t_buffers;
+
+                /* If we're in abort mode, we just un-journal the buffer and
+                   release it for background writing. */
+
+                if (is_journal_aborted(journal)) {
+                        JBUFFER_TRACE(jh, "journal is aborting: refile");
+                        journal_refile_buffer(journal, jh);
+                        /* If that was the last one, we need to clean up
+                         * any descriptor buffers which may have been
+                         * already allocated, even if we are now
+                         * aborting. */
+                        if (!commit_transaction->t_buffers)
+                                goto start_journal_io;
+                        continue;
+                }
+
+                /* Make sure we have a descriptor block in which to
+                   record the metadata buffer. */
+
+                if (!descriptor) {
+                        struct buffer_head *bh;
+
+                        J_ASSERT (bufs == 0);
+
+                        jbd_debug(4, "JBD: get descriptor\n");
+
+                        descriptor = journal_get_descriptor_buffer(journal);
+                        if (!descriptor) {
+                                __journal_abort_hard(journal);
+                                continue;
+                        }
+
+                        bh = jh2bh(descriptor);
+                        jbd_debug(4, "JBD: got buffer %llu (%p)\n",
+                                (unsigned long long)bh->b_blocknr, bh->b_data);
+                        header = (journal_header_t *)&bh->b_data[0];
+                        header->h_magic     = cpu_to_be32(JFS_MAGIC_NUMBER);
+                        header->h_blocktype = cpu_to_be32(JFS_DESCRIPTOR_BLOCK);
+                        header->h_sequence  = cpu_to_be32(commit_transaction->t_tid);
+
+                        tagp = &bh->b_data[sizeof(journal_header_t)];
+                        space_left = bh->b_size - sizeof(journal_header_t);
+                        first_tag = 1;
+                        set_buffer_jwrite(bh);
+                        set_buffer_dirty(bh);
+                        wbuf[bufs++] = bh;
+
+                        /* Record it so that we can wait for IO
+                           completion later */
+                        BUFFER_TRACE(bh, "ph3: file as descriptor");
+                        journal_file_buffer(descriptor, commit_transaction,
+                                        BJ_LogCtl);
+                }
+
+                /* Where is the buffer to be written? */
+
+                err = journal_next_log_block(journal, &blocknr);
+                /* If the block mapping failed, just abandon the buffer
+                   and repeat this loop: we'll fall into the
+                   refile-on-abort condition above. */
+                if (err) {
+                        __journal_abort_hard(journal);
+                        continue;
+                }
+
+                /*
+                 * start_this_handle() uses t_outstanding_credits to determine
+                 * the free space in the log, but this counter is changed
+                 * by journal_next_log_block() also.
+                 */
+                commit_transaction->t_outstanding_credits--;
+
+                /* Bump b_count to prevent truncate from stumbling over
+                   the shadowed buffer!  @@@ This can go if we ever get
+                   rid of the BJ_IO/BJ_Shadow pairing of buffers. */
+                atomic_inc(&jh2bh(jh)->b_count);
+
+                /* Make a temporary IO buffer with which to write it out
+                   (this will requeue both the metadata buffer and the
+                   temporary IO buffer). new_bh goes on BJ_IO*/
+
+                set_bit(BH_JWrite, &jh2bh(jh)->b_state);
+                /*
+                 * akpm: journal_write_metadata_buffer() sets
+                 * new_bh->b_transaction to commit_transaction.
+                 * We need to clean this up before we release new_bh
+                 * (which is of type BJ_IO)
+                 */
+                JBUFFER_TRACE(jh, "ph3: write metadata");
+                flags = journal_write_metadata_buffer(commit_transaction,
+                                                      jh, &new_jh, blocknr);
+                set_bit(BH_JWrite, &jh2bh(new_jh)->b_state);
+                wbuf[bufs++] = jh2bh(new_jh);
+
+                /* Record the new block's tag in the current descriptor
+                   buffer */
+
+                tag_flag = 0;
+                if (flags & 1)
+                        tag_flag |= JFS_FLAG_ESCAPE;
+                if (!first_tag)
+                        tag_flag |= JFS_FLAG_SAME_UUID;
+
+                tag = (journal_block_tag_t *) tagp;
+                tag->t_blocknr = cpu_to_be32(jh2bh(jh)->b_blocknr);
+                tag->t_flags = cpu_to_be32(tag_flag);
+                tagp += sizeof(journal_block_tag_t);
+                space_left -= sizeof(journal_block_tag_t);
+
+                if (first_tag) {
+                        memcpy (tagp, journal->j_uuid, 16);
+                        tagp += 16;
+                        space_left -= 16;
+                        first_tag = 0;
+                }
+
+                /* If there's no more to do, or if the descriptor is full,
+                   let the IO rip! */
+
+                if (bufs == journal->j_wbufsize ||
+                    commit_transaction->t_buffers == NULL ||
+                    space_left < sizeof(journal_block_tag_t) + 16) {
+
+                        jbd_debug(4, "JBD: Submit %d IOs\n", bufs);
+
+                        /* Write an end-of-descriptor marker before
+                           submitting the IOs.  "tag" still points to
+                           the last tag we set up. */
+
+                        tag->t_flags |= cpu_to_be32(JFS_FLAG_LAST_TAG);
+
+start_journal_io:
+                        for (i = 0; i < bufs; i++) {
+                                struct buffer_head *bh = wbuf[i];
+                                lock_buffer(bh);
+                                clear_buffer_dirty(bh);
+                                set_buffer_uptodate(bh);
+                                bh->b_end_io = journal_end_buffer_io_sync;
+                                submit_bh(WRITE, bh);
+                        }
+                        cond_resched();
+
+                        /* Force a new descriptor to be generated next
+                           time round the loop. */
+                        descriptor = NULL;
+                        bufs = 0;
+                }
+        }
+
+        /* Lo and behold: we have just managed to send a transaction to
+           the log.  Before we can commit it, wait for the IO so far to
+           complete.  Control buffers being written are on the
+           transaction's t_log_list queue, and metadata buffers are on
+           the t_iobuf_list queue.
+
+           Wait for the buffers in reverse order.  That way we are
+           less likely to be woken up until all IOs have completed, and
+           so we incur less scheduling load.
+        */
+
+        jbd_debug(3, "JBD: commit phase 4\n");
+
+        /*
+         * akpm: these are BJ_IO, and j_list_lock is not needed.
+         * See __journal_try_to_free_buffer.
+         */
+wait_for_iobuf:
+        while (commit_transaction->t_iobuf_list != NULL) {
+                struct buffer_head *bh;
+
+                jh = commit_transaction->t_iobuf_list->b_tprev;
+                bh = jh2bh(jh);
+                if (buffer_locked(bh)) {
+                        wait_on_buffer(bh);
+                        goto wait_for_iobuf;
+                }
+                if (cond_resched())
+                        goto wait_for_iobuf;
+
+                if (unlikely(!buffer_uptodate(bh)))
+                        err = -EIO;
+
+                clear_buffer_jwrite(bh);
+
+                JBUFFER_TRACE(jh, "ph4: unfile after journal write");
+                journal_unfile_buffer(journal, jh);
+
+                /*
+                 * ->t_iobuf_list should contain only dummy buffer_heads
+                 * which were created by journal_write_metadata_buffer().
+                 */
+                BUFFER_TRACE(bh, "dumping temporary bh");
+                journal_put_journal_head(jh);
+                __brelse(bh);
+                J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
+                free_buffer_head(bh);
+
+                /* We also have to unlock and free the corresponding
+                   shadowed buffer */
+                jh = commit_transaction->t_shadow_list->b_tprev;
+                bh = jh2bh(jh);
+                clear_bit(BH_JWrite, &bh->b_state);
+                J_ASSERT_BH(bh, buffer_jbddirty(bh));
+
+                /* The metadata is now released for reuse, but we need
+                   to remember it against this transaction so that when
+                   we finally commit, we can do any checkpointing
+                   required. */
+                JBUFFER_TRACE(jh, "file as BJ_Forget");
+                journal_file_buffer(jh, commit_transaction, BJ_Forget);
+                /* Wake up any transactions which were waiting for this
+                   IO to complete */
+                wake_up_bit(&bh->b_state, BH_Unshadow);
+                JBUFFER_TRACE(jh, "brelse shadowed buffer");
+                __brelse(bh);
+        }
+
+        J_ASSERT (commit_transaction->t_shadow_list == NULL);
+
+        jbd_debug(3, "JBD: commit phase 5\n");
+
+        /* Here we wait for the revoke record and descriptor record buffers */
+ wait_for_ctlbuf:
+        while (commit_transaction->t_log_list != NULL) {
+                struct buffer_head *bh;
+
+                jh = commit_transaction->t_log_list->b_tprev;
+                bh = jh2bh(jh);
+                if (buffer_locked(bh)) {
+                        wait_on_buffer(bh);
+                        goto wait_for_ctlbuf;
+                }
+                if (cond_resched())
+                        goto wait_for_ctlbuf;
+
+                if (unlikely(!buffer_uptodate(bh)))
+                        err = -EIO;
+
+                BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
+                clear_buffer_jwrite(bh);
+                journal_unfile_buffer(journal, jh);
+                journal_put_journal_head(jh);
+                __brelse(bh);           /* One for getblk */
+                /* AKPM: bforget here */
+        }
+
+        jbd_debug(3, "JBD: commit phase 6\n");
+
+        if (journal_write_commit_record(journal, commit_transaction))
+                err = -EIO;
+
+        if (err)
+                __journal_abort_hard(journal);
+
+        /* End of a transaction!  Finally, we can do checkpoint
+           processing: any buffers committed as a result of this
+           transaction can be removed from any checkpoint list it was on
+           before. */
+
+        jbd_debug(3, "JBD: commit phase 7\n");
+
+        J_ASSERT(commit_transaction->t_sync_datalist == NULL);
+        J_ASSERT(commit_transaction->t_buffers == NULL);
+        J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
+        J_ASSERT(commit_transaction->t_iobuf_list == NULL);
+        J_ASSERT(commit_transaction->t_shadow_list == NULL);
+        J_ASSERT(commit_transaction->t_log_list == NULL);
+
+restart_loop:
+        while (commit_transaction->t_forget) {
+                transaction_t *cp_transaction;
+                struct buffer_head *bh;
+
+                jh = commit_transaction->t_forget;
+                bh = jh2bh(jh);
+                jbd_lock_bh_state(bh);
+                J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
+                        jh->b_transaction == journal->j_running_transaction);
+
+                /*
+                 * If there is undo-protected committed data against
+                 * this buffer, then we can remove it now.  If it is a
+                 * buffer needing such protection, the old frozen_data
+                 * field now points to a committed version of the
+                 * buffer, so rotate that field to the new committed
+                 * data.
+                 *
+                 * Otherwise, we can just throw away the frozen data now.
+                 */
+                if (jh->b_committed_data) {
+                        kfree(jh->b_committed_data);
+                        jh->b_committed_data = NULL;
+                        if (jh->b_frozen_data) {
+                                jh->b_committed_data = jh->b_frozen_data;
+                                jh->b_frozen_data = NULL;
+                        }
+                } else if (jh->b_frozen_data) {
+                        kfree(jh->b_frozen_data);
+                        jh->b_frozen_data = NULL;
+                }
+
+                spin_lock(&journal->j_list_lock);
+                cp_transaction = jh->b_cp_transaction;
+                if (cp_transaction) {
+                        JBUFFER_TRACE(jh, "remove from old cp transaction");
+                        __journal_remove_checkpoint(jh);
+                }
+
+                /* Only re-checkpoint the buffer_head if it is marked
+                 * dirty.  If the buffer was added to the BJ_Forget list
+                 * by journal_forget, it may no longer be dirty and
+                 * there's no point in keeping a checkpoint record for
+                 * it. */
+
+                /* A buffer which has been freed while still being
+                 * journaled by a previous transaction may end up still
+                 * being dirty here, but we want to avoid writing back
+                 * that buffer in the future now that the last use has
+                 * been committed.  That's not only a performance gain,
+                 * it also stops aliasing problems if the buffer is left
+                 * behind for writeback and gets reallocated for another
+                 * use in a different page. */
+                if (buffer_freed(bh)) {
+                        clear_buffer_freed(bh);
+                        clear_buffer_jbddirty(bh);
+                }
+
+                if (buffer_jbddirty(bh)) {
+                        JBUFFER_TRACE(jh, "add to new checkpointing trans");
+                        __journal_insert_checkpoint(jh, commit_transaction);
+                        JBUFFER_TRACE(jh, "refile for checkpoint writeback");
+                        __journal_refile_buffer(jh);
+                        jbd_unlock_bh_state(bh);
+                } else {
+                        J_ASSERT_BH(bh, !buffer_dirty(bh));
+                        J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
+                        __journal_unfile_buffer(jh);
+                        jbd_unlock_bh_state(bh);
+                        journal_remove_journal_head(bh);  /* needs a brelse */
+                        release_buffer_page(bh);
+                }
+                spin_unlock(&journal->j_list_lock);
+                if (cond_resched())
+                        goto restart_loop;
+        }
+
+        /* Done with this transaction! */
+
+        jbd_debug(3, "JBD: commit phase 8\n");
+
+        J_ASSERT(commit_transaction->t_state == T_COMMIT);
+
+        /*
+         * This is a bit sleazy.  We borrow j_list_lock to protect
+         * journal->j_committing_transaction in __journal_remove_checkpoint.
+         * Really, __jornal_remove_checkpoint should be using j_state_lock but
+         * it's a bit hassle to hold that across __journal_remove_checkpoint
+         */
+        spin_lock(&journal->j_state_lock);
+        spin_lock(&journal->j_list_lock);
+        commit_transaction->t_state = T_FINISHED;
+        J_ASSERT(commit_transaction == journal->j_committing_transaction);
+        journal->j_commit_sequence = commit_transaction->t_tid;
+        journal->j_committing_transaction = NULL;
+        spin_unlock(&journal->j_state_lock);
+
+        if (commit_transaction->t_checkpoint_list == NULL) {
+                __journal_drop_transaction(journal, commit_transaction);
+        } else {
+                if (journal->j_checkpoint_transactions == NULL) {
+                        journal->j_checkpoint_transactions = commit_transaction;
+                        commit_transaction->t_cpnext = commit_transaction;
+                        commit_transaction->t_cpprev = commit_transaction;
+                } else {
+                        commit_transaction->t_cpnext =
+                                journal->j_checkpoint_transactions;
+                        commit_transaction->t_cpprev =
+                                commit_transaction->t_cpnext->t_cpprev;
+                        commit_transaction->t_cpnext->t_cpprev =
+                                commit_transaction;
+                        commit_transaction->t_cpprev->t_cpnext =
+                                commit_transaction;
+                }
+        }
+        spin_unlock(&journal->j_list_lock);
+
+        jbd_debug(1, "JBD: commit %d complete, head %d\n",
+                  journal->j_commit_sequence, journal->j_tail_sequence);
+
+        wake_up(&journal->j_wait_done_commit);
+}