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journal.c

/*
 * linux/fs/jbd2/journal.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 journal-writing code; part of the ext2fs
 * journaling system.
 *
 * This file manages journals: areas of disk reserved for logging
 * transactional updates.  This includes the kernel journaling thread
 * which is responsible for scheduling updates to the log.
 *
 * We do not actually manage the physical storage of the journal in this
 * file: that is left to a per-journal policy function, which allows us
 * to store the journal within a filesystem-specified area for ext2
 * journaling (ext2 can use a reserved inode for storing the log).
 */

#include <linux/module.h>
#include <linux/time.h>
#include <linux/fs.h>
#include <linux/jbd2.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/freezer.h>
#include <linux/pagemap.h>
#include <linux/kthread.h>
#include <linux/poison.h>
#include <linux/proc_fs.h>
#include <linux/debugfs.h>

#include <asm/uaccess.h>
#include <asm/page.h>

EXPORT_SYMBOL(jbd2_journal_start);
EXPORT_SYMBOL(jbd2_journal_restart);
EXPORT_SYMBOL(jbd2_journal_extend);
EXPORT_SYMBOL(jbd2_journal_stop);
EXPORT_SYMBOL(jbd2_journal_lock_updates);
EXPORT_SYMBOL(jbd2_journal_unlock_updates);
EXPORT_SYMBOL(jbd2_journal_get_write_access);
EXPORT_SYMBOL(jbd2_journal_get_create_access);
EXPORT_SYMBOL(jbd2_journal_get_undo_access);
EXPORT_SYMBOL(jbd2_journal_dirty_data);
EXPORT_SYMBOL(jbd2_journal_dirty_metadata);
EXPORT_SYMBOL(jbd2_journal_release_buffer);
EXPORT_SYMBOL(jbd2_journal_forget);
#if 0
EXPORT_SYMBOL(journal_sync_buffer);
#endif
EXPORT_SYMBOL(jbd2_journal_flush);
EXPORT_SYMBOL(jbd2_journal_revoke);

EXPORT_SYMBOL(jbd2_journal_init_dev);
EXPORT_SYMBOL(jbd2_journal_init_inode);
EXPORT_SYMBOL(jbd2_journal_update_format);
EXPORT_SYMBOL(jbd2_journal_check_used_features);
EXPORT_SYMBOL(jbd2_journal_check_available_features);
EXPORT_SYMBOL(jbd2_journal_set_features);
EXPORT_SYMBOL(jbd2_journal_create);
EXPORT_SYMBOL(jbd2_journal_load);
EXPORT_SYMBOL(jbd2_journal_destroy);
EXPORT_SYMBOL(jbd2_journal_update_superblock);
EXPORT_SYMBOL(jbd2_journal_abort);
EXPORT_SYMBOL(jbd2_journal_errno);
EXPORT_SYMBOL(jbd2_journal_ack_err);
EXPORT_SYMBOL(jbd2_journal_clear_err);
EXPORT_SYMBOL(jbd2_log_wait_commit);
EXPORT_SYMBOL(jbd2_journal_start_commit);
EXPORT_SYMBOL(jbd2_journal_force_commit_nested);
EXPORT_SYMBOL(jbd2_journal_wipe);
EXPORT_SYMBOL(jbd2_journal_blocks_per_page);
EXPORT_SYMBOL(jbd2_journal_invalidatepage);
EXPORT_SYMBOL(jbd2_journal_try_to_free_buffers);
EXPORT_SYMBOL(jbd2_journal_force_commit);

static int journal_convert_superblock_v1(journal_t *, journal_superblock_t *);
static void __journal_abort_soft (journal_t *journal, int errno);

/*
 * Helper function used to manage commit timeouts
 */

static void commit_timeout(unsigned long __data)
{
      struct task_struct * p = (struct task_struct *) __data;

      wake_up_process(p);
}

/*
 * kjournald2: The main thread function used to manage a logging device
 * journal.
 *
 * This kernel thread is responsible for two things:
 *
 * 1) COMMIT:  Every so often we need to commit the current state of the
 *    filesystem to disk.  The journal thread is responsible for writing
 *    all of the metadata buffers to disk.
 *
 * 2) CHECKPOINT: We cannot reuse a used section of the log file until all
 *    of the data in that part of the log has been rewritten elsewhere on
 *    the disk.  Flushing these old buffers to reclaim space in the log is
 *    known as checkpointing, and this thread is responsible for that job.
 */

static int kjournald2(void *arg)
{
      journal_t *journal = arg;
      transaction_t *transaction;

      /*
       * Set up an interval timer which can be used to trigger a commit wakeup
       * after the commit interval expires
       */
      setup_timer(&journal->j_commit_timer, commit_timeout,
                  (unsigned long)current);

      /* Record that the journal thread is running */
      journal->j_task = current;
      wake_up(&journal->j_wait_done_commit);

      printk(KERN_INFO "kjournald2 starting.  Commit interval %ld seconds\n",
                  journal->j_commit_interval / HZ);

      /*
       * And now, wait forever for commit wakeup events.
       */
      spin_lock(&journal->j_state_lock);

loop:
      if (journal->j_flags & JBD2_UNMOUNT)
            goto end_loop;

      jbd_debug(1, "commit_sequence=%d, commit_request=%d\n",
            journal->j_commit_sequence, journal->j_commit_request);

      if (journal->j_commit_sequence != journal->j_commit_request) {
            jbd_debug(1, "OK, requests differ\n");
            spin_unlock(&journal->j_state_lock);
            del_timer_sync(&journal->j_commit_timer);
            jbd2_journal_commit_transaction(journal);
            spin_lock(&journal->j_state_lock);
            goto loop;
      }

      wake_up(&journal->j_wait_done_commit);
      if (freezing(current)) {
            /*
             * The simpler the better. Flushing journal isn't a
             * good idea, because that depends on threads that may
             * be already stopped.
             */
            jbd_debug(1, "Now suspending kjournald2\n");
            spin_unlock(&journal->j_state_lock);
            refrigerator();
            spin_lock(&journal->j_state_lock);
      } else {
            /*
             * We assume on resume that commits are already there,
             * so we don't sleep
             */
            DEFINE_WAIT(wait);
            int should_sleep = 1;

            prepare_to_wait(&journal->j_wait_commit, &wait,
                        TASK_INTERRUPTIBLE);
            if (journal->j_commit_sequence != journal->j_commit_request)
                  should_sleep = 0;
            transaction = journal->j_running_transaction;
            if (transaction && time_after_eq(jiffies,
                                    transaction->t_expires))
                  should_sleep = 0;
            if (journal->j_flags & JBD2_UNMOUNT)
                  should_sleep = 0;
            if (should_sleep) {
                  spin_unlock(&journal->j_state_lock);
                  schedule();
                  spin_lock(&journal->j_state_lock);
            }
            finish_wait(&journal->j_wait_commit, &wait);
      }

      jbd_debug(1, "kjournald2 wakes\n");

      /*
       * Were we woken up by a commit wakeup event?
       */
      transaction = journal->j_running_transaction;
      if (transaction && time_after_eq(jiffies, transaction->t_expires)) {
            journal->j_commit_request = transaction->t_tid;
            jbd_debug(1, "woke because of timeout\n");
      }
      goto loop;

end_loop:
      spin_unlock(&journal->j_state_lock);
      del_timer_sync(&journal->j_commit_timer);
      journal->j_task = NULL;
      wake_up(&journal->j_wait_done_commit);
      jbd_debug(1, "Journal thread exiting.\n");
      return 0;
}

static int jbd2_journal_start_thread(journal_t *journal)
{
      struct task_struct *t;

      t = kthread_run(kjournald2, journal, "kjournald2");
      if (IS_ERR(t))
            return PTR_ERR(t);

      wait_event(journal->j_wait_done_commit, journal->j_task != 0);
      return 0;
}

static void journal_kill_thread(journal_t *journal)
{
      spin_lock(&journal->j_state_lock);
      journal->j_flags |= JBD2_UNMOUNT;

      while (journal->j_task) {
            wake_up(&journal->j_wait_commit);
            spin_unlock(&journal->j_state_lock);
            wait_event(journal->j_wait_done_commit, journal->j_task == 0);
            spin_lock(&journal->j_state_lock);
      }
      spin_unlock(&journal->j_state_lock);
}

/*
 * jbd2_journal_write_metadata_buffer: write a metadata buffer to the journal.
 *
 * Writes a metadata buffer to a given disk block.  The actual IO is not
 * performed but a new buffer_head is constructed which labels the data
 * to be written with the correct destination disk block.
 *
 * Any magic-number escaping which needs to be done will cause a
 * copy-out here.  If the buffer happens to start with the
 * JBD2_MAGIC_NUMBER, then we can't write it to the log directly: the
 * magic number is only written to the log for descripter blocks.  In
 * this case, we copy the data and replace the first word with 0, and we
 * return a result code which indicates that this buffer needs to be
 * marked as an escaped buffer in the corresponding log descriptor
 * block.  The missing word can then be restored when the block is read
 * during recovery.
 *
 * If the source buffer has already been modified by a new transaction
 * since we took the last commit snapshot, we use the frozen copy of
 * that data for IO.  If we end up using the existing buffer_head's data
 * for the write, then we *have* to lock the buffer to prevent anyone
 * else from using and possibly modifying it while the IO is in
 * progress.
 *
 * The function returns a pointer to the buffer_heads to be used for IO.
 *
 * We assume that the journal has already been locked in this function.
 *
 * Return value:
 *  <0: Error
 * >=0: Finished OK
 *
 * On success:
 * Bit 0 set == escape performed on the data
 * Bit 1 set == buffer copy-out performed (kfree the data after IO)
 */

int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
                          struct journal_head  *jh_in,
                          struct journal_head **jh_out,
                          unsigned long long blocknr)
{
      int need_copy_out = 0;
      int done_copy_out = 0;
      int do_escape = 0;
      char *mapped_data;
      struct buffer_head *new_bh;
      struct journal_head *new_jh;
      struct page *new_page;
      unsigned int new_offset;
      struct buffer_head *bh_in = jh2bh(jh_in);

      /*
       * The buffer really shouldn't be locked: only the current committing
       * transaction is allowed to write it, so nobody else is allowed
       * to do any IO.
       *
       * akpm: except if we're journalling data, and write() output is
       * also part of a shared mapping, and another thread has
       * decided to launch a writepage() against this buffer.
       */
      J_ASSERT_BH(bh_in, buffer_jbddirty(bh_in));

      new_bh = alloc_buffer_head(GFP_NOFS|__GFP_NOFAIL);

      /*
       * If a new transaction has already done a buffer copy-out, then
       * we use that version of the data for the commit.
       */
      jbd_lock_bh_state(bh_in);
repeat:
      if (jh_in->b_frozen_data) {
            done_copy_out = 1;
            new_page = virt_to_page(jh_in->b_frozen_data);
            new_offset = offset_in_page(jh_in->b_frozen_data);
      } else {
            new_page = jh2bh(jh_in)->b_page;
            new_offset = offset_in_page(jh2bh(jh_in)->b_data);
      }

      mapped_data = kmap_atomic(new_page, KM_USER0);
      /*
       * Check for escaping
       */
      if (*((__be32 *)(mapped_data + new_offset)) ==
                        cpu_to_be32(JBD2_MAGIC_NUMBER)) {
            need_copy_out = 1;
            do_escape = 1;
      }
      kunmap_atomic(mapped_data, KM_USER0);

      /*
       * Do we need to do a data copy?
       */
      if (need_copy_out && !done_copy_out) {
            char *tmp;

            jbd_unlock_bh_state(bh_in);
            tmp = jbd2_alloc(bh_in->b_size, GFP_NOFS);
            jbd_lock_bh_state(bh_in);
            if (jh_in->b_frozen_data) {
                  jbd2_free(tmp, bh_in->b_size);
                  goto repeat;
            }

            jh_in->b_frozen_data = tmp;
            mapped_data = kmap_atomic(new_page, KM_USER0);
            memcpy(tmp, mapped_data + new_offset, jh2bh(jh_in)->b_size);
            kunmap_atomic(mapped_data, KM_USER0);

            new_page = virt_to_page(tmp);
            new_offset = offset_in_page(tmp);
            done_copy_out = 1;
      }

      /*
       * Did we need to do an escaping?  Now we've done all the
       * copying, we can finally do so.
       */
      if (do_escape) {
            mapped_data = kmap_atomic(new_page, KM_USER0);
            *((unsigned int *)(mapped_data + new_offset)) = 0;
            kunmap_atomic(mapped_data, KM_USER0);
      }

      /* keep subsequent assertions sane */
      new_bh->b_state = 0;
      init_buffer(new_bh, NULL, NULL);
      atomic_set(&new_bh->b_count, 1);
      jbd_unlock_bh_state(bh_in);

      new_jh = jbd2_journal_add_journal_head(new_bh); /* This sleeps */

      set_bh_page(new_bh, new_page, new_offset);
      new_jh->b_transaction = NULL;
      new_bh->b_size = jh2bh(jh_in)->b_size;
      new_bh->b_bdev = transaction->t_journal->j_dev;
      new_bh->b_blocknr = blocknr;
      set_buffer_mapped(new_bh);
      set_buffer_dirty(new_bh);

      *jh_out = new_jh;

      /*
       * The to-be-written buffer needs to get moved to the io queue,
       * and the original buffer whose contents we are shadowing or
       * copying is moved to the transaction's shadow queue.
       */
      JBUFFER_TRACE(jh_in, "file as BJ_Shadow");
      jbd2_journal_file_buffer(jh_in, transaction, BJ_Shadow);
      JBUFFER_TRACE(new_jh, "file as BJ_IO");
      jbd2_journal_file_buffer(new_jh, transaction, BJ_IO);

      return do_escape | (done_copy_out << 1);
}

/*
 * Allocation code for the journal file.  Manage the space left in the
 * journal, so that we can begin checkpointing when appropriate.
 */

/*
 * __jbd2_log_space_left: Return the number of free blocks left in the journal.
 *
 * Called with the journal already locked.
 *
 * Called under j_state_lock
 */

int __jbd2_log_space_left(journal_t *journal)
{
      int left = journal->j_free;

      assert_spin_locked(&journal->j_state_lock);

      /*
       * Be pessimistic here about the number of those free blocks which
       * might be required for log descriptor control blocks.
       */

#define MIN_LOG_RESERVED_BLOCKS 32 /* Allow for rounding errors */

      left -= MIN_LOG_RESERVED_BLOCKS;

      if (left <= 0)
            return 0;
      left -= (left >> 3);
      return left;
}

/*
 * Called under j_state_lock.  Returns true if a transaction was started.
 */
int __jbd2_log_start_commit(journal_t *journal, tid_t target)
{
      /*
       * Are we already doing a recent enough commit?
       */
      if (!tid_geq(journal->j_commit_request, target)) {
            /*
             * We want a new commit: OK, mark the request and wakup the
             * commit thread.  We do _not_ do the commit ourselves.
             */

            journal->j_commit_request = target;
            jbd_debug(1, "JBD: requesting commit %d/%d\n",
                    journal->j_commit_request,
                    journal->j_commit_sequence);
            wake_up(&journal->j_wait_commit);
            return 1;
      }
      return 0;
}

int jbd2_log_start_commit(journal_t *journal, tid_t tid)
{
      int ret;

      spin_lock(&journal->j_state_lock);
      ret = __jbd2_log_start_commit(journal, tid);
      spin_unlock(&journal->j_state_lock);
      return ret;
}

/*
 * Force and wait upon a commit if the calling process is not within
 * transaction.  This is used for forcing out undo-protected data which contains
 * bitmaps, when the fs is running out of space.
 *
 * We can only force the running transaction if we don't have an active handle;
 * otherwise, we will deadlock.
 *
 * Returns true if a transaction was started.
 */
int jbd2_journal_force_commit_nested(journal_t *journal)
{
      transaction_t *transaction = NULL;
      tid_t tid;

      spin_lock(&journal->j_state_lock);
      if (journal->j_running_transaction && !current->journal_info) {
            transaction = journal->j_running_transaction;
            __jbd2_log_start_commit(journal, transaction->t_tid);
      } else if (journal->j_committing_transaction)
            transaction = journal->j_committing_transaction;

      if (!transaction) {
            spin_unlock(&journal->j_state_lock);
            return 0;   /* Nothing to retry */
      }

      tid = transaction->t_tid;
      spin_unlock(&journal->j_state_lock);
      jbd2_log_wait_commit(journal, tid);
      return 1;
}

/*
 * Start a commit of the current running transaction (if any).  Returns true
 * if a transaction was started, and fills its tid in at *ptid
 */
int jbd2_journal_start_commit(journal_t *journal, tid_t *ptid)
{
      int ret = 0;

      spin_lock(&journal->j_state_lock);
      if (journal->j_running_transaction) {
            tid_t tid = journal->j_running_transaction->t_tid;

            ret = __jbd2_log_start_commit(journal, tid);
            if (ret && ptid)
                  *ptid = tid;
      } else if (journal->j_committing_transaction && ptid) {
            /*
             * If ext3_write_super() recently started a commit, then we
             * have to wait for completion of that transaction
             */
            *ptid = journal->j_committing_transaction->t_tid;
            ret = 1;
      }
      spin_unlock(&journal->j_state_lock);
      return ret;
}

/*
 * Wait for a specified commit to complete.
 * The caller may not hold the journal lock.
 */
int jbd2_log_wait_commit(journal_t *journal, tid_t tid)
{
      int err = 0;

#ifdef CONFIG_JBD2_DEBUG
      spin_lock(&journal->j_state_lock);
      if (!tid_geq(journal->j_commit_request, tid)) {
            printk(KERN_EMERG
                   "%s: error: j_commit_request=%d, tid=%d\n",
                   __FUNCTION__, journal->j_commit_request, tid);
      }
      spin_unlock(&journal->j_state_lock);
#endif
      spin_lock(&journal->j_state_lock);
      while (tid_gt(tid, journal->j_commit_sequence)) {
            jbd_debug(1, "JBD: want %d, j_commit_sequence=%d\n",
                          tid, journal->j_commit_sequence);
            wake_up(&journal->j_wait_commit);
            spin_unlock(&journal->j_state_lock);
            wait_event(journal->j_wait_done_commit,
                        !tid_gt(tid, journal->j_commit_sequence));
            spin_lock(&journal->j_state_lock);
      }
      spin_unlock(&journal->j_state_lock);

      if (unlikely(is_journal_aborted(journal))) {
            printk(KERN_EMERG "journal commit I/O error\n");
            err = -EIO;
      }
      return err;
}

/*
 * Log buffer allocation routines:
 */

int jbd2_journal_next_log_block(journal_t *journal, unsigned long long *retp)
{
      unsigned long blocknr;

      spin_lock(&journal->j_state_lock);
      J_ASSERT(journal->j_free > 1);

      blocknr = journal->j_head;
      journal->j_head++;
      journal->j_free--;
      if (journal->j_head == journal->j_last)
            journal->j_head = journal->j_first;
      spin_unlock(&journal->j_state_lock);
      return jbd2_journal_bmap(journal, blocknr, retp);
}

/*
 * Conversion of logical to physical block numbers for the journal
 *
 * On external journals the journal blocks are identity-mapped, so
 * this is a no-op.  If needed, we can use j_blk_offset - everything is
 * ready.
 */
int jbd2_journal_bmap(journal_t *journal, unsigned long blocknr,
             unsigned long long *retp)
{
      int err = 0;
      unsigned long long ret;

      if (journal->j_inode) {
            ret = bmap(journal->j_inode, blocknr);
            if (ret)
                  *retp = ret;
            else {
                  char b[BDEVNAME_SIZE];

                  printk(KERN_ALERT "%s: journal block not found "
                              "at offset %lu on %s\n",
                        __FUNCTION__,
                        blocknr,
                        bdevname(journal->j_dev, b));
                  err = -EIO;
                  __journal_abort_soft(journal, err);
            }
      } else {
            *retp = blocknr; /* +journal->j_blk_offset */
      }
      return err;
}

/*
 * We play buffer_head aliasing tricks to write data/metadata blocks to
 * the journal without copying their contents, but for journal
 * descriptor blocks we do need to generate bona fide buffers.
 *
 * After the caller of jbd2_journal_get_descriptor_buffer() has finished modifying
 * the buffer's contents they really should run flush_dcache_page(bh->b_page).
 * But we don't bother doing that, so there will be coherency problems with
 * mmaps of blockdevs which hold live JBD-controlled filesystems.
 */
struct journal_head *jbd2_journal_get_descriptor_buffer(journal_t *journal)
{
      struct buffer_head *bh;
      unsigned long long blocknr;
      int err;

      err = jbd2_journal_next_log_block(journal, &blocknr);

      if (err)
            return NULL;

      bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
      lock_buffer(bh);
      memset(bh->b_data, 0, journal->j_blocksize);
      set_buffer_uptodate(bh);
      unlock_buffer(bh);
      BUFFER_TRACE(bh, "return this buffer");
      return jbd2_journal_add_journal_head(bh);
}

/*
 * Management for journal control blocks: functions to create and
 * destroy journal_t structures, and to initialise and read existing
 * journal blocks from disk.  */

/* First: create and setup a journal_t object in memory.  We initialise
 * very few fields yet: that has to wait until we have created the
 * journal structures from from scratch, or loaded them from disk. */

static journal_t * journal_init_common (void)
{
      journal_t *journal;
      int err;

      journal = kzalloc(sizeof(*journal), GFP_KERNEL|__GFP_NOFAIL);
      if (!journal)
            goto fail;

      init_waitqueue_head(&journal->j_wait_transaction_locked);
      init_waitqueue_head(&journal->j_wait_logspace);
      init_waitqueue_head(&journal->j_wait_done_commit);
      init_waitqueue_head(&journal->j_wait_checkpoint);
      init_waitqueue_head(&journal->j_wait_commit);
      init_waitqueue_head(&journal->j_wait_updates);
      mutex_init(&journal->j_barrier);
      mutex_init(&journal->j_checkpoint_mutex);
      spin_lock_init(&journal->j_revoke_lock);
      spin_lock_init(&journal->j_list_lock);
      spin_lock_init(&journal->j_state_lock);

      journal->j_commit_interval = (HZ * JBD2_DEFAULT_MAX_COMMIT_AGE);

      /* The journal is marked for error until we succeed with recovery! */
      journal->j_flags = JBD2_ABORT;

      /* Set up a default-sized revoke table for the new mount. */
      err = jbd2_journal_init_revoke(journal, JOURNAL_REVOKE_DEFAULT_HASH);
      if (err) {
            kfree(journal);
            goto fail;
      }
      return journal;
fail:
      return NULL;
}

/* jbd2_journal_init_dev and jbd2_journal_init_inode:
 *
 * Create a journal structure assigned some fixed set of disk blocks to
 * the journal.  We don't actually touch those disk blocks yet, but we
 * need to set up all of the mapping information to tell the journaling
 * system where the journal blocks are.
 *
 */

/**
 *  journal_t * jbd2_journal_init_dev() - creates an initialises a journal structure
 *  @bdev: Block device on which to create the journal
 *  @fs_dev: Device which hold journalled filesystem for this journal.
 *  @start: Block nr Start of journal.
 *  @len:  Length of the journal in blocks.
 *  @blocksize: blocksize of journalling device
 *  @returns: a newly created journal_t *
 *
 *  jbd2_journal_init_dev creates a journal which maps a fixed contiguous
 *  range of blocks on an arbitrary block device.
 *
 */
journal_t * jbd2_journal_init_dev(struct block_device *bdev,
                  struct block_device *fs_dev,
                  unsigned long long start, int len, int blocksize)
{
      journal_t *journal = journal_init_common();
      struct buffer_head *bh;
      int n;

      if (!journal)
            return NULL;

      /* journal descriptor can store up to n blocks -bzzz */
      journal->j_blocksize = blocksize;
      n = journal->j_blocksize / sizeof(journal_block_tag_t);
      journal->j_wbufsize = n;
      journal->j_wbuf = kmalloc(n * sizeof(struct buffer_head*), GFP_KERNEL);
      if (!journal->j_wbuf) {
            printk(KERN_ERR "%s: Cant allocate bhs for commit thread\n",
                  __FUNCTION__);
            kfree(journal);
            journal = NULL;
            goto out;
      }
      journal->j_dev = bdev;
      journal->j_fs_dev = fs_dev;
      journal->j_blk_offset = start;
      journal->j_maxlen = len;

      bh = __getblk(journal->j_dev, start, journal->j_blocksize);
      J_ASSERT(bh != NULL);
      journal->j_sb_buffer = bh;
      journal->j_superblock = (journal_superblock_t *)bh->b_data;
out:
      return journal;
}

/**
 *  journal_t * jbd2_journal_init_inode () - creates a journal which maps to a inode.
 *  @inode: An inode to create the journal in
 *
 * jbd2_journal_init_inode creates a journal which maps an on-disk inode as
 * the journal.  The inode must exist already, must support bmap() and
 * must have all data blocks preallocated.
 */
journal_t * jbd2_journal_init_inode (struct inode *inode)
{
      struct buffer_head *bh;
      journal_t *journal = journal_init_common();
      int err;
      int n;
      unsigned long long blocknr;

      if (!journal)
            return NULL;

      journal->j_dev = journal->j_fs_dev = inode->i_sb->s_bdev;
      journal->j_inode = inode;
      jbd_debug(1,
              "journal %p: inode %s/%ld, size %Ld, bits %d, blksize %ld\n",
              journal, inode->i_sb->s_id, inode->i_ino,
              (long long) inode->i_size,
              inode->i_sb->s_blocksize_bits, inode->i_sb->s_blocksize);

      journal->j_maxlen = inode->i_size >> inode->i_sb->s_blocksize_bits;
      journal->j_blocksize = inode->i_sb->s_blocksize;

      /* journal descriptor can store up to n blocks -bzzz */
      n = journal->j_blocksize / sizeof(journal_block_tag_t);
      journal->j_wbufsize = n;
      journal->j_wbuf = kmalloc(n * sizeof(struct buffer_head*), GFP_KERNEL);
      if (!journal->j_wbuf) {
            printk(KERN_ERR "%s: Cant allocate bhs for commit thread\n",
                  __FUNCTION__);
            kfree(journal);
            return NULL;
      }

      err = jbd2_journal_bmap(journal, 0, &blocknr);
      /* If that failed, give up */
      if (err) {
            printk(KERN_ERR "%s: Cannnot locate journal superblock\n",
                   __FUNCTION__);
            kfree(journal);
            return NULL;
      }

      bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
      J_ASSERT(bh != NULL);
      journal->j_sb_buffer = bh;
      journal->j_superblock = (journal_superblock_t *)bh->b_data;

      return journal;
}

/*
 * If the journal init or create aborts, we need to mark the journal
 * superblock as being NULL to prevent the journal destroy from writing
 * back a bogus superblock.
 */
static void journal_fail_superblock (journal_t *journal)
{
      struct buffer_head *bh = journal->j_sb_buffer;
      brelse(bh);
      journal->j_sb_buffer = NULL;
}

/*
 * Given a journal_t structure, initialise the various fields for
 * startup of a new journaling session.  We use this both when creating
 * a journal, and after recovering an old journal to reset it for
 * subsequent use.
 */

static int journal_reset(journal_t *journal)
{
      journal_superblock_t *sb = journal->j_superblock;
      unsigned long long first, last;

      first = be32_to_cpu(sb->s_first);
      last = be32_to_cpu(sb->s_maxlen);

      journal->j_first = first;
      journal->j_last = last;

      journal->j_head = first;
      journal->j_tail = first;
      journal->j_free = last - first;

      journal->j_tail_sequence = journal->j_transaction_sequence;
      journal->j_commit_sequence = journal->j_transaction_sequence - 1;
      journal->j_commit_request = journal->j_commit_sequence;

      journal->j_max_transaction_buffers = journal->j_maxlen / 4;

      /* Add the dynamic fields and write it to disk. */
      jbd2_journal_update_superblock(journal, 1);
      return jbd2_journal_start_thread(journal);
}

/**
 * int jbd2_journal_create() - Initialise the new journal file
 * @journal: Journal to create. This structure must have been initialised
 *
 * Given a journal_t structure which tells us which disk blocks we can
 * use, create a new journal superblock and initialise all of the
 * journal fields from scratch.
 **/
int jbd2_journal_create(journal_t *journal)
{
      unsigned long long blocknr;
      struct buffer_head *bh;
      journal_superblock_t *sb;
      int i, err;

      if (journal->j_maxlen < JBD2_MIN_JOURNAL_BLOCKS) {
            printk (KERN_ERR "Journal length (%d blocks) too short.\n",
                  journal->j_maxlen);
            journal_fail_superblock(journal);
            return -EINVAL;
      }

      if (journal->j_inode == NULL) {
            /*
             * We don't know what block to start at!
             */
            printk(KERN_EMERG
                   "%s: creation of journal on external device!\n",
                   __FUNCTION__);
            BUG();
      }

      /* Zero out the entire journal on disk.  We cannot afford to
         have any blocks on disk beginning with JBD2_MAGIC_NUMBER. */
      jbd_debug(1, "JBD: Zeroing out journal blocks...\n");
      for (i = 0; i < journal->j_maxlen; i++) {
            err = jbd2_journal_bmap(journal, i, &blocknr);
            if (err)
                  return err;
            bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
            lock_buffer(bh);
            memset (bh->b_data, 0, journal->j_blocksize);
            BUFFER_TRACE(bh, "marking dirty");
            mark_buffer_dirty(bh);
            BUFFER_TRACE(bh, "marking uptodate");
            set_buffer_uptodate(bh);
            unlock_buffer(bh);
            __brelse(bh);
      }

      sync_blockdev(journal->j_dev);
      jbd_debug(1, "JBD: journal cleared.\n");

      /* OK, fill in the initial static fields in the new superblock */
      sb = journal->j_superblock;

      sb->s_header.h_magic     = cpu_to_be32(JBD2_MAGIC_NUMBER);
      sb->s_header.h_blocktype = cpu_to_be32(JBD2_SUPERBLOCK_V2);

      sb->s_blocksize   = cpu_to_be32(journal->j_blocksize);
      sb->s_maxlen      = cpu_to_be32(journal->j_maxlen);
      sb->s_first = cpu_to_be32(1);

      journal->j_transaction_sequence = 1;

      journal->j_flags &= ~JBD2_ABORT;
      journal->j_format_version = 2;

      return journal_reset(journal);
}

/**
 * void jbd2_journal_update_superblock() - Update journal sb on disk.
 * @journal: The journal to update.
 * @wait: Set to '0' if you don't want to wait for IO completion.
 *
 * Update a journal's dynamic superblock fields and write it to disk,
 * optionally waiting for the IO to complete.
 */
void jbd2_journal_update_superblock(journal_t *journal, int wait)
{
      journal_superblock_t *sb = journal->j_superblock;
      struct buffer_head *bh = journal->j_sb_buffer;

      /*
       * As a special case, if the on-disk copy is already marked as needing
       * no recovery (s_start == 0) and there are no outstanding transactions
       * in the filesystem, then we can safely defer the superblock update
       * until the next commit by setting JBD2_FLUSHED.  This avoids
       * attempting a write to a potential-readonly device.
       */
      if (sb->s_start == 0 && journal->j_tail_sequence ==
                        journal->j_transaction_sequence) {
            jbd_debug(1,"JBD: Skipping superblock update on recovered sb "
                  "(start %ld, seq %d, errno %d)\n",
                  journal->j_tail, journal->j_tail_sequence,
                  journal->j_errno);
            goto out;
      }

      spin_lock(&journal->j_state_lock);
      jbd_debug(1,"JBD: updating superblock (start %ld, seq %d, errno %d)\n",
              journal->j_tail, journal->j_tail_sequence, journal->j_errno);

      sb->s_sequence = cpu_to_be32(journal->j_tail_sequence);
      sb->s_start    = cpu_to_be32(journal->j_tail);
      sb->s_errno    = cpu_to_be32(journal->j_errno);
      spin_unlock(&journal->j_state_lock);

      BUFFER_TRACE(bh, "marking dirty");
      mark_buffer_dirty(bh);
      if (wait)
            sync_dirty_buffer(bh);
      else
            ll_rw_block(SWRITE, 1, &bh);

out:
      /* If we have just flushed the log (by marking s_start==0), then
       * any future commit will have to be careful to update the
       * superblock again to re-record the true start of the log. */

      spin_lock(&journal->j_state_lock);
      if (sb->s_start)
            journal->j_flags &= ~JBD2_FLUSHED;
      else
            journal->j_flags |= JBD2_FLUSHED;
      spin_unlock(&journal->j_state_lock);
}

/*
 * Read the superblock for a given journal, performing initial
 * validation of the format.
 */

static int journal_get_superblock(journal_t *journal)
{
      struct buffer_head *bh;
      journal_superblock_t *sb;
      int err = -EIO;

      bh = journal->j_sb_buffer;

      J_ASSERT(bh != NULL);
      if (!buffer_uptodate(bh)) {
            ll_rw_block(READ, 1, &bh);
            wait_on_buffer(bh);
            if (!buffer_uptodate(bh)) {
                  printk (KERN_ERR
                        "JBD: IO error reading journal superblock\n");
                  goto out;
            }
      }

      sb = journal->j_superblock;

      err = -EINVAL;

      if (sb->s_header.h_magic != cpu_to_be32(JBD2_MAGIC_NUMBER) ||
          sb->s_blocksize != cpu_to_be32(journal->j_blocksize)) {
            printk(KERN_WARNING "JBD: no valid journal superblock found\n");
            goto out;
      }

      switch(be32_to_cpu(sb->s_header.h_blocktype)) {
      case JBD2_SUPERBLOCK_V1:
            journal->j_format_version = 1;
            break;
      case JBD2_SUPERBLOCK_V2:
            journal->j_format_version = 2;
            break;
      default:
            printk(KERN_WARNING "JBD: unrecognised superblock format ID\n");
            goto out;
      }

      if (be32_to_cpu(sb->s_maxlen) < journal->j_maxlen)
            journal->j_maxlen = be32_to_cpu(sb->s_maxlen);
      else if (be32_to_cpu(sb->s_maxlen) > journal->j_maxlen) {
            printk (KERN_WARNING "JBD: journal file too short\n");
            goto out;
      }

      return 0;

out:
      journal_fail_superblock(journal);
      return err;
}

/*
 * Load the on-disk journal superblock and read the key fields into the
 * journal_t.
 */

static int load_superblock(journal_t *journal)
{
      int err;
      journal_superblock_t *sb;

      err = journal_get_superblock(journal);
      if (err)
            return err;

      sb = journal->j_superblock;

      journal->j_tail_sequence = be32_to_cpu(sb->s_sequence);
      journal->j_tail = be32_to_cpu(sb->s_start);
      journal->j_first = be32_to_cpu(sb->s_first);
      journal->j_last = be32_to_cpu(sb->s_maxlen);
      journal->j_errno = be32_to_cpu(sb->s_errno);

      return 0;
}


/**
 * int jbd2_journal_load() - Read journal from disk.
 * @journal: Journal to act on.
 *
 * Given a journal_t structure which tells us which disk blocks contain
 * a journal, read the journal from disk to initialise the in-memory
 * structures.
 */
int jbd2_journal_load(journal_t *journal)
{
      int err;
      journal_superblock_t *sb;

      err = load_superblock(journal);
      if (err)
            return err;

      sb = journal->j_superblock;
      /* If this is a V2 superblock, then we have to check the
       * features flags on it. */

      if (journal->j_format_version >= 2) {
            if ((sb->s_feature_ro_compat &
                 ~cpu_to_be32(JBD2_KNOWN_ROCOMPAT_FEATURES)) ||
                (sb->s_feature_incompat &
                 ~cpu_to_be32(JBD2_KNOWN_INCOMPAT_FEATURES))) {
                  printk (KERN_WARNING
                        "JBD: Unrecognised features on journal\n");
                  return -EINVAL;
            }
      }

      /* Let the recovery code check whether it needs to recover any
       * data from the journal. */
      if (jbd2_journal_recover(journal))
            goto recovery_error;

      /* OK, we've finished with the dynamic journal bits:
       * reinitialise the dynamic contents of the superblock in memory
       * and reset them on disk. */
      if (journal_reset(journal))
            goto recovery_error;

      journal->j_flags &= ~JBD2_ABORT;
      journal->j_flags |= JBD2_LOADED;
      return 0;

recovery_error:
      printk (KERN_WARNING "JBD: recovery failed\n");
      return -EIO;
}

/**
 * void jbd2_journal_destroy() - Release a journal_t structure.
 * @journal: Journal to act on.
 *
 * Release a journal_t structure once it is no longer in use by the
 * journaled object.
 */
void jbd2_journal_destroy(journal_t *journal)
{
      /* Wait for the commit thread to wake up and die. */
      journal_kill_thread(journal);

      /* Force a final log commit */
      if (journal->j_running_transaction)
            jbd2_journal_commit_transaction(journal);

      /* Force any old transactions to disk */

      /* Totally anal locking here... */
      spin_lock(&journal->j_list_lock);
      while (journal->j_checkpoint_transactions != NULL) {
            spin_unlock(&journal->j_list_lock);
            jbd2_log_do_checkpoint(journal);
            spin_lock(&journal->j_list_lock);
      }

      J_ASSERT(journal->j_running_transaction == NULL);
      J_ASSERT(journal->j_committing_transaction == NULL);
      J_ASSERT(journal->j_checkpoint_transactions == NULL);
      spin_unlock(&journal->j_list_lock);

      /* We can now mark the journal as empty. */
      journal->j_tail = 0;
      journal->j_tail_sequence = ++journal->j_transaction_sequence;
      if (journal->j_sb_buffer) {
            jbd2_journal_update_superblock(journal, 1);
            brelse(journal->j_sb_buffer);
      }

      if (journal->j_inode)
            iput(journal->j_inode);
      if (journal->j_revoke)
            jbd2_journal_destroy_revoke(journal);
      kfree(journal->j_wbuf);
      kfree(journal);
}


/**
 *int jbd2_journal_check_used_features () - Check if features specified are used.
 * @journal: Journal to check.
 * @compat: bitmask of compatible features
 * @ro: bitmask of features that force read-only mount
 * @incompat: bitmask of incompatible features
 *
 * Check whether the journal uses all of a given set of
 * features.  Return true (non-zero) if it does.
 **/

int jbd2_journal_check_used_features (journal_t *journal, unsigned long compat,
                         unsigned long ro, unsigned long incompat)
{
      journal_superblock_t *sb;

      if (!compat && !ro && !incompat)
            return 1;
      if (journal->j_format_version == 1)
            return 0;

      sb = journal->j_superblock;

      if (((be32_to_cpu(sb->s_feature_compat) & compat) == compat) &&
          ((be32_to_cpu(sb->s_feature_ro_compat) & ro) == ro) &&
          ((be32_to_cpu(sb->s_feature_incompat) & incompat) == incompat))
            return 1;

      return 0;
}

/**
 * int jbd2_journal_check_available_features() - Check feature set in journalling layer
 * @journal: Journal to check.
 * @compat: bitmask of compatible features
 * @ro: bitmask of features that force read-only mount
 * @incompat: bitmask of incompatible features
 *
 * Check whether the journaling code supports the use of
 * all of a given set of features on this journal.  Return true
 * (non-zero) if it can. */

int jbd2_journal_check_available_features (journal_t *journal, unsigned long compat,
                              unsigned long ro, unsigned long incompat)
{
      journal_superblock_t *sb;

      if (!compat && !ro && !incompat)
            return 1;

      sb = journal->j_superblock;

      /* We can support any known requested features iff the
       * superblock is in version 2.  Otherwise we fail to support any
       * extended sb features. */

      if (journal->j_format_version != 2)
            return 0;

      if ((compat   & JBD2_KNOWN_COMPAT_FEATURES) == compat &&
          (ro       & JBD2_KNOWN_ROCOMPAT_FEATURES) == ro &&
          (incompat & JBD2_KNOWN_INCOMPAT_FEATURES) == incompat)
            return 1;

      return 0;
}

/**
 * int jbd2_journal_set_features () - Mark a given journal feature in the superblock
 * @journal: Journal to act on.
 * @compat: bitmask of compatible features
 * @ro: bitmask of features that force read-only mount
 * @incompat: bitmask of incompatible features
 *
 * Mark a given journal feature as present on the
 * superblock.  Returns true if the requested features could be set.
 *
 */

int jbd2_journal_set_features (journal_t *journal, unsigned long compat,
                    unsigned long ro, unsigned long incompat)
{
      journal_superblock_t *sb;

      if (jbd2_journal_check_used_features(journal, compat, ro, incompat))
            return 1;

      if (!jbd2_journal_check_available_features(journal, compat, ro, incompat))
            return 0;

      jbd_debug(1, "Setting new features 0x%lx/0x%lx/0x%lx\n",
              compat, ro, incompat);

      sb = journal->j_superblock;

      sb->s_feature_compat    |= cpu_to_be32(compat);
      sb->s_feature_ro_compat |= cpu_to_be32(ro);
      sb->s_feature_incompat  |= cpu_to_be32(incompat);

      return 1;
}


/**
 * int jbd2_journal_update_format () - Update on-disk journal structure.
 * @journal: Journal to act on.
 *
 * Given an initialised but unloaded journal struct, poke about in the
 * on-disk structure to update it to the most recent supported version.
 */
int jbd2_journal_update_format (journal_t *journal)
{
      journal_superblock_t *sb;
      int err;

      err = journal_get_superblock(journal);
      if (err)
            return err;

      sb = journal->j_superblock;

      switch (be32_to_cpu(sb->s_header.h_blocktype)) {
      case JBD2_SUPERBLOCK_V2:
            return 0;
      case JBD2_SUPERBLOCK_V1:
            return journal_convert_superblock_v1(journal, sb);
      default:
            break;
      }
      return -EINVAL;
}

static int journal_convert_superblock_v1(journal_t *journal,
                               journal_superblock_t *sb)
{
      int offset, blocksize;
      struct buffer_head *bh;

      printk(KERN_WARNING
            "JBD: Converting superblock from version 1 to 2.\n");

      /* Pre-initialise new fields to zero */
      offset = ((char *) &(sb->s_feature_compat)) - ((char *) sb);
      blocksize = be32_to_cpu(sb->s_blocksize);
      memset(&sb->s_feature_compat, 0, blocksize-offset);

      sb->s_nr_users = cpu_to_be32(1);
      sb->s_header.h_blocktype = cpu_to_be32(JBD2_SUPERBLOCK_V2);
      journal->j_format_version = 2;

      bh = journal->j_sb_buffer;
      BUFFER_TRACE(bh, "marking dirty");
      mark_buffer_dirty(bh);
      sync_dirty_buffer(bh);
      return 0;
}


/**
 * int jbd2_journal_flush () - Flush journal
 * @journal: Journal to act on.
 *
 * Flush all data for a given journal to disk and empty the journal.
 * Filesystems can use this when remounting readonly to ensure that
 * recovery does not need to happen on remount.
 */

int jbd2_journal_flush(journal_t *journal)
{
      int err = 0;
      transaction_t *transaction = NULL;
      unsigned long old_tail;

      spin_lock(&journal->j_state_lock);

      /* Force everything buffered to the log... */
      if (journal->j_running_transaction) {
            transaction = journal->j_running_transaction;
            __jbd2_log_start_commit(journal, transaction->t_tid);
      } else if (journal->j_committing_transaction)
            transaction = journal->j_committing_transaction;

      /* Wait for the log commit to complete... */
      if (transaction) {
            tid_t tid = transaction->t_tid;

            spin_unlock(&journal->j_state_lock);
            jbd2_log_wait_commit(journal, tid);
      } else {
            spin_unlock(&journal->j_state_lock);
      }

      /* ...and flush everything in the log out to disk. */
      spin_lock(&journal->j_list_lock);
      while (!err && journal->j_checkpoint_transactions != NULL) {
            spin_unlock(&journal->j_list_lock);
            err = jbd2_log_do_checkpoint(journal);
            spin_lock(&journal->j_list_lock);
      }
      spin_unlock(&journal->j_list_lock);
      jbd2_cleanup_journal_tail(journal);

      /* Finally, mark the journal as really needing no recovery.
       * This sets s_start==0 in the underlying superblock, which is
       * the magic code for a fully-recovered superblock.  Any future
       * commits of data to the journal will restore the current
       * s_start value. */
      spin_lock(&journal->j_state_lock);
      old_tail = journal->j_tail;
      journal->j_tail = 0;
      spin_unlock(&journal->j_state_lock);
      jbd2_journal_update_superblock(journal, 1);
      spin_lock(&journal->j_state_lock);
      journal->j_tail = old_tail;

      J_ASSERT(!journal->j_running_transaction);
      J_ASSERT(!journal->j_committing_transaction);
      J_ASSERT(!journal->j_checkpoint_transactions);
      J_ASSERT(journal->j_head == journal->j_tail);
      J_ASSERT(journal->j_tail_sequence == journal->j_transaction_sequence);
      spin_unlock(&journal->j_state_lock);
      return err;
}

/**
 * int jbd2_journal_wipe() - Wipe journal contents
 * @journal: Journal to act on.
 * @write: flag (see below)
 *
 * Wipe out all of the contents of a journal, safely.  This will produce
 * a warning if the journal contains any valid recovery information.
 * Must be called between journal_init_*() and jbd2_journal_load().
 *
 * If 'write' is non-zero, then we wipe out the journal on disk; otherwise
 * we merely suppress recovery.
 */

int jbd2_journal_wipe(journal_t *journal, int write)
{
      journal_superblock_t *sb;
      int err = 0;

      J_ASSERT (!(journal->j_flags & JBD2_LOADED));

      err = load_superblock(journal);
      if (err)
            return err;

      sb = journal->j_superblock;

      if (!journal->j_tail)
            goto no_recovery;

      printk (KERN_WARNING "JBD: %s recovery information on journal\n",
            write ? "Clearing" : "Ignoring");

      err = jbd2_journal_skip_recovery(journal);
      if (write)
            jbd2_journal_update_superblock(journal, 1);

 no_recovery:
      return err;
}

/*
 * journal_dev_name: format a character string to describe on what
 * device this journal is present.
 */

static const char *journal_dev_name(journal_t *journal, char *buffer)
{
      struct block_device *bdev;

      if (journal->j_inode)
            bdev = journal->j_inode->i_sb->s_bdev;
      else
            bdev = journal->j_dev;

      return bdevname(bdev, buffer);
}

/*
 * Journal abort has very specific semantics, which we describe
 * for journal abort.
 *
 * Two internal function, which provide abort to te jbd layer
 * itself are here.
 */

/*
 * Quick version for internal journal use (doesn't lock the journal).
 * Aborts hard --- we mark the abort as occurred, but do _nothing_ else,
 * and don't attempt to make any other journal updates.
 */
void __jbd2_journal_abort_hard(journal_t *journal)
{
      transaction_t *transaction;
      char b[BDEVNAME_SIZE];

      if (journal->j_flags & JBD2_ABORT)
            return;

      printk(KERN_ERR "Aborting journal on device %s.\n",
            journal_dev_name(journal, b));

      spin_lock(&journal->j_state_lock);
      journal->j_flags |= JBD2_ABORT;
      transaction = journal->j_running_transaction;
      if (transaction)
            __jbd2_log_start_commit(journal, transaction->t_tid);
      spin_unlock(&journal->j_state_lock);
}

/* Soft abort: record the abort error status in the journal superblock,
 * but don't do any other IO. */
static void __journal_abort_soft (journal_t *journal, int errno)
{
      if (journal->j_flags & JBD2_ABORT)
            return;

      if (!journal->j_errno)
            journal->j_errno = errno;

      __jbd2_journal_abort_hard(journal);

      if (errno)
            jbd2_journal_update_superblock(journal, 1);
}

/**
 * void jbd2_journal_abort () - Shutdown the journal immediately.
 * @journal: the journal to shutdown.
 * @errno:   an error number to record in the journal indicating
 *           the reason for the shutdown.
 *
 * Perform a complete, immediate shutdown of the ENTIRE
 * journal (not of a single transaction).  This operation cannot be
 * undone without closing and reopening the journal.
 *
 * The jbd2_journal_abort function is intended to support higher level error
 * recovery mechanisms such as the ext2/ext3 remount-readonly error
 * mode.
 *
 * Journal abort has very specific semantics.  Any existing dirty,
 * unjournaled buffers in the main filesystem will still be written to
 * disk by bdflush, but the journaling mechanism will be suspended
 * immediately and no further transaction commits will be honoured.
 *
 * Any dirty, journaled buffers will be written back to disk without
 * hitting the journal.  Atomicity cannot be guaranteed on an aborted
 * filesystem, but we _do_ attempt to leave as much data as possible
 * behind for fsck to use for cleanup.
 *
 * Any attempt to get a new transaction handle on a journal which is in
 * ABORT state will just result in an -EROFS error return.  A
 * jbd2_journal_stop on an existing handle will return -EIO if we have
 * entered abort state during the update.
 *
 * Recursive transactions are not disturbed by journal abort until the
 * final jbd2_journal_stop, which will receive the -EIO error.
 *
 * Finally, the jbd2_journal_abort call allows the caller to supply an errno
 * which will be recorded (if possible) in the journal superblock.  This
 * allows a client to record failure conditions in the middle of a
 * transaction without having to complete the transaction to record the
 * failure to disk.  ext3_error, for example, now uses this
 * functionality.
 *
 * Errors which originate from within the journaling layer will NOT
 * supply an errno; a null errno implies that absolutely no further
 * writes are done to the journal (unless there are any already in
 * progress).
 *
 */

void jbd2_journal_abort(journal_t *journal, int errno)
{
      __journal_abort_soft(journal, errno);
}

/**
 * int jbd2_journal_errno () - returns the journal's error state.
 * @journal: journal to examine.
 *
 * This is the errno numbet set with jbd2_journal_abort(), the last
 * time the journal was mounted - if the journal was stopped
 * without calling abort this will be 0.
 *
 * If the journal has been aborted on this mount time -EROFS will
 * be returned.
 */
int jbd2_journal_errno(journal_t *journal)
{
      int err;

      spin_lock(&journal->j_state_lock);
      if (journal->j_flags & JBD2_ABORT)
            err = -EROFS;
      else
            err = journal->j_errno;
      spin_unlock(&journal->j_state_lock);
      return err;
}

/**
 * int jbd2_journal_clear_err () - clears the journal's error state
 * @journal: journal to act on.
 *
 * An error must be cleared or Acked to take a FS out of readonly
 * mode.
 */
int jbd2_journal_clear_err(journal_t *journal)
{
      int err = 0;

      spin_lock(&journal->j_state_lock);
      if (journal->j_flags & JBD2_ABORT)
            err = -EROFS;
      else
            journal->j_errno = 0;
      spin_unlock(&journal->j_state_lock);
      return err;
}

/**
 * void jbd2_journal_ack_err() - Ack journal err.
 * @journal: journal to act on.
 *
 * An error must be cleared or Acked to take a FS out of readonly
 * mode.
 */
void jbd2_journal_ack_err(journal_t *journal)
{
      spin_lock(&journal->j_state_lock);
      if (journal->j_errno)
            journal->j_flags |= JBD2_ACK_ERR;
      spin_unlock(&journal->j_state_lock);
}

int jbd2_journal_blocks_per_page(struct inode *inode)
{
      return 1 << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);
}

/*
 * helper functions to deal with 32 or 64bit block numbers.
 */
size_t journal_tag_bytes(journal_t *journal)
{
      if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_64BIT))
            return JBD2_TAG_SIZE64;
      else
            return JBD2_TAG_SIZE32;
}

/*
 * Journal_head storage management
 */
static struct kmem_cache *jbd2_journal_head_cache;
#ifdef CONFIG_JBD2_DEBUG
static atomic_t nr_journal_heads = ATOMIC_INIT(0);
#endif

static int journal_init_jbd2_journal_head_cache(void)
{
      int retval;

      J_ASSERT(jbd2_journal_head_cache == 0);
      jbd2_journal_head_cache = kmem_cache_create("jbd2_journal_head",
                        sizeof(struct journal_head),
                        0,          /* offset */
                        0,          /* flags */
                        NULL);            /* ctor */
      retval = 0;
      if (jbd2_journal_head_cache == 0) {
            retval = -ENOMEM;
            printk(KERN_EMERG "JBD: no memory for journal_head cache\n");
      }
      return retval;
}

static void jbd2_journal_destroy_jbd2_journal_head_cache(void)
{
      J_ASSERT(jbd2_journal_head_cache != NULL);
      kmem_cache_destroy(jbd2_journal_head_cache);
      jbd2_journal_head_cache = NULL;
}

/*
 * journal_head splicing and dicing
 */
static struct journal_head *journal_alloc_journal_head(void)
{
      struct journal_head *ret;
      static unsigned long last_warning;

#ifdef CONFIG_JBD2_DEBUG
      atomic_inc(&nr_journal_heads);
#endif
      ret = kmem_cache_alloc(jbd2_journal_head_cache, GFP_NOFS);
      if (ret == 0) {
            jbd_debug(1, "out of memory for journal_head\n");
            if (time_after(jiffies, last_warning + 5*HZ)) {
                  printk(KERN_NOTICE "ENOMEM in %s, retrying.\n",
                         __FUNCTION__);
                  last_warning = jiffies;
            }
            while (ret == 0) {
                  yield();
                  ret = kmem_cache_alloc(jbd2_journal_head_cache, GFP_NOFS);
            }
      }
      return ret;
}

static void journal_free_journal_head(struct journal_head *jh)
{
#ifdef CONFIG_JBD2_DEBUG
      atomic_dec(&nr_journal_heads);
      memset(jh, JBD2_POISON_FREE, sizeof(*jh));
#endif
      kmem_cache_free(jbd2_journal_head_cache, jh);
}

/*
 * A journal_head is attached to a buffer_head whenever JBD has an
 * interest in the buffer.
 *
 * Whenever a buffer has an attached journal_head, its ->b_state:BH_JBD bit
 * is set.  This bit is tested in core kernel code where we need to take
 * JBD-specific actions.  Testing the zeroness of ->b_private is not reliable
 * there.
 *
 * When a buffer has its BH_JBD bit set, its ->b_count is elevated by one.
 *
 * When a buffer has its BH_JBD bit set it is immune from being released by
 * core kernel code, mainly via ->b_count.
 *
 * A journal_head may be detached from its buffer_head when the journal_head's
 * b_transaction, b_cp_transaction and b_next_transaction pointers are NULL.
 * Various places in JBD call jbd2_journal_remove_journal_head() to indicate that the
 * journal_head can be dropped if needed.
 *
 * Various places in the kernel want to attach a journal_head to a buffer_head
 * _before_ attaching the journal_head to a transaction.  To protect the
 * journal_head in this situation, jbd2_journal_add_journal_head elevates the
 * journal_head's b_jcount refcount by one.  The caller must call
 * jbd2_journal_put_journal_head() to undo this.
 *
 * So the typical usage would be:
 *
 *    (Attach a journal_head if needed.  Increments b_jcount)
 *    struct journal_head *jh = jbd2_journal_add_journal_head(bh);
 *    ...
 *    jh->b_transaction = xxx;
 *    jbd2_journal_put_journal_head(jh);
 *
 * Now, the journal_head's b_jcount is zero, but it is safe from being released
 * because it has a non-zero b_transaction.
 */

/*
 * Give a buffer_head a journal_head.
 *
 * Doesn't need the journal lock.
 * May sleep.
 */
struct journal_head *jbd2_journal_add_journal_head(struct buffer_head *bh)
{
      struct journal_head *jh;
      struct journal_head *new_jh = NULL;

repeat:
      if (!buffer_jbd(bh)) {
            new_jh = journal_alloc_journal_head();
            memset(new_jh, 0, sizeof(*new_jh));
      }

      jbd_lock_bh_journal_head(bh);
      if (buffer_jbd(bh)) {
            jh = bh2jh(bh);
      } else {
            J_ASSERT_BH(bh,
                  (atomic_read(&bh->b_count) > 0) ||
                  (bh->b_page && bh->b_page->mapping));

            if (!new_jh) {
                  jbd_unlock_bh_journal_head(bh);
                  goto repeat;
            }

            jh = new_jh;
            new_jh = NULL;          /* We consumed it */
            set_buffer_jbd(bh);
            bh->b_private = jh;
            jh->b_bh = bh;
            get_bh(bh);
            BUFFER_TRACE(bh, "added journal_head");
      }
      jh->b_jcount++;
      jbd_unlock_bh_journal_head(bh);
      if (new_jh)
            journal_free_journal_head(new_jh);
      return bh->b_private;
}

/*
 * Grab a ref against this buffer_head's journal_head.  If it ended up not
 * having a journal_head, return NULL
 */
struct journal_head *jbd2_journal_grab_journal_head(struct buffer_head *bh)
{
      struct journal_head *jh = NULL;

      jbd_lock_bh_journal_head(bh);
      if (buffer_jbd(bh)) {
            jh = bh2jh(bh);
            jh->b_jcount++;
      }
      jbd_unlock_bh_journal_head(bh);
      return jh;
}

static void __journal_remove_journal_head(struct buffer_head *bh)
{
      struct journal_head *jh = bh2jh(bh);

      J_ASSERT_JH(jh, jh->b_jcount >= 0);

      get_bh(bh);
      if (jh->b_jcount == 0) {
            if (jh->b_transaction == NULL &&
                        jh->b_next_transaction == NULL &&
                        jh->b_cp_transaction == NULL) {
                  J_ASSERT_JH(jh, jh->b_jlist == BJ_None);
                  J_ASSERT_BH(bh, buffer_jbd(bh));
                  J_ASSERT_BH(bh, jh2bh(jh) == bh);
                  BUFFER_TRACE(bh, "remove journal_head");
                  if (jh->b_frozen_data) {
                        printk(KERN_WARNING "%s: freeing "
                                    "b_frozen_data\n",
                                    __FUNCTION__);
                        jbd2_free(jh->b_frozen_data, bh->b_size);
                  }
                  if (jh->b_committed_data) {
                        printk(KERN_WARNING "%s: freeing "
                                    "b_committed_data\n",
                                    __FUNCTION__);
                        jbd2_free(jh->b_committed_data, bh->b_size);
                  }
                  bh->b_private = NULL;
                  jh->b_bh = NULL;  /* debug, really */
                  clear_buffer_jbd(bh);
                  __brelse(bh);
                  journal_free_journal_head(jh);
            } else {
                  BUFFER_TRACE(bh, "journal_head was locked");
            }
      }
}

/*
 * jbd2_journal_remove_journal_head(): if the buffer isn't attached to a transaction
 * and has a zero b_jcount then remove and release its journal_head.   If we did
 * see that the buffer is not used by any transaction we also "logically"
 * decrement ->b_count.
 *
 * We in fact take an additional increment on ->b_count as a convenience,
 * because the caller usually wants to do additional things with the bh
 * after calling here.
 * The caller of jbd2_journal_remove_journal_head() *must* run __brelse(bh) at some
 * time.  Once the caller has run __brelse(), the buffer is eligible for
 * reaping by try_to_free_buffers().
 */
void jbd2_journal_remove_journal_head(struct buffer_head *bh)
{
      jbd_lock_bh_journal_head(bh);
      __journal_remove_journal_head(bh);
      jbd_unlock_bh_journal_head(bh);
}

/*
 * Drop a reference on the passed journal_head.  If it fell to zero then try to
 * release the journal_head from the buffer_head.
 */
void jbd2_journal_put_journal_head(struct journal_head *jh)
{
      struct buffer_head *bh = jh2bh(jh);

      jbd_lock_bh_journal_head(bh);
      J_ASSERT_JH(jh, jh->b_jcount > 0);
      --jh->b_jcount;
      if (!jh->b_jcount && !jh->b_transaction) {
            __journal_remove_journal_head(bh);
            __brelse(bh);
      }
      jbd_unlock_bh_journal_head(bh);
}

/*
 * debugfs tunables
 */
#ifdef CONFIG_JBD2_DEBUG
u8 jbd2_journal_enable_debug __read_mostly;
EXPORT_SYMBOL(jbd2_journal_enable_debug);

#define JBD2_DEBUG_NAME "jbd2-debug"

static struct dentry *jbd2_debugfs_dir;
static struct dentry *jbd2_debug;

static void __init jbd2_create_debugfs_entry(void)
{
      jbd2_debugfs_dir = debugfs_create_dir("jbd2", NULL);
      if (jbd2_debugfs_dir)
            jbd2_debug = debugfs_create_u8(JBD2_DEBUG_NAME, S_IRUGO,
                                     jbd2_debugfs_dir,
                                     &jbd2_journal_enable_debug);
}

static void __exit jbd2_remove_debugfs_entry(void)
{
      debugfs_remove(jbd2_debug);
      debugfs_remove(jbd2_debugfs_dir);
}

#else

static void __init jbd2_create_debugfs_entry(void)
{
}

static void __exit jbd2_remove_debugfs_entry(void)
{
}

#endif

struct kmem_cache *jbd2_handle_cache;

static int __init journal_init_handle_cache(void)
{
      jbd2_handle_cache = kmem_cache_create("jbd2_journal_handle",
                        sizeof(handle_t),
                        0,          /* offset */
                        0,          /* flags */
                        NULL);            /* ctor */
      if (jbd2_handle_cache == NULL) {
            printk(KERN_EMERG "JBD: failed to create handle cache\n");
            return -ENOMEM;
      }
      return 0;
}

static void jbd2_journal_destroy_handle_cache(void)
{
      if (jbd2_handle_cache)
            kmem_cache_destroy(jbd2_handle_cache);
}

/*
 * Module startup and shutdown
 */

static int __init journal_init_caches(void)
{
      int ret;

      ret = jbd2_journal_init_revoke_caches();
      if (ret == 0)
            ret = journal_init_jbd2_journal_head_cache();
      if (ret == 0)
            ret = journal_init_handle_cache();
      return ret;
}

static void jbd2_journal_destroy_caches(void)
{
      jbd2_journal_destroy_revoke_caches();
      jbd2_journal_destroy_jbd2_journal_head_cache();
      jbd2_journal_destroy_handle_cache();
}

static int __init journal_init(void)
{
      int ret;

      BUILD_BUG_ON(sizeof(struct journal_superblock_s) != 1024);

      ret = journal_init_caches();
      if (ret != 0)
            jbd2_journal_destroy_caches();
      jbd2_create_debugfs_entry();
      return ret;
}

static void __exit journal_exit(void)
{
#ifdef CONFIG_JBD2_DEBUG
      int n = atomic_read(&nr_journal_heads);
      if (n)
            printk(KERN_EMERG "JBD: leaked %d journal_heads!\n", n);
#endif
      jbd2_remove_debugfs_entry();
      jbd2_journal_destroy_caches();
}

MODULE_LICENSE("GPL");
module_init(journal_init);
module_exit(journal_exit);


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