/*
   * Copyright (c) 2010 Red Hat, Inc. All Rights Reserved.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License as
   * published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it would be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write the Free Software Foundation,
   * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
   */
  
  #include "xfs.h"
  #include "xfs_fs.h"

  #include "xfs_log_format.h"

  #include "xfs_shared.h"

  #include "xfs_trans_resv.h"

  #include "xfs_sb.h"
  #include "xfs_ag.h"

  #include "xfs_mount.h"
  #include "xfs_error.h"
  #include "xfs_alloc.h"

  #include "xfs_extent_busy.h"

  #include "xfs_discard.h"

  #include "xfs_trans.h"
  #include "xfs_trans_priv.h"
  #include "xfs_log.h"
  #include "xfs_log_priv.h"

  
  /*

   * Allocate a new ticket. Failing to get a new ticket makes it really hard to
   * recover, so we don't allow failure here. Also, we allocate in a context that
   * we don't want to be issuing transactions from, so we need to tell the
   * allocation code this as well.
   *
   * We don't reserve any space for the ticket - we are going to steal whatever
   * space we require from transactions as they commit. To ensure we reserve all
   * the space required, we need to set the current reservation of the ticket to
   * zero so that we know to steal the initial transaction overhead from the
   * first transaction commit.
   */
  static struct xlog_ticket *
  xlog_cil_ticket_alloc(

  	struct xlog	*log)

  {
  	struct xlog_ticket *tic;
  
  	tic = xlog_ticket_alloc(log, 0, 1, XFS_TRANSACTION, 0,
  				KM_SLEEP|KM_NOFS);
  	tic->t_trans_type = XFS_TRANS_CHECKPOINT;
  
  	/*
  	 * set the current reservation to zero so we know to steal the basic
  	 * transaction overhead reservation from the first transaction commit.
  	 */
  	tic->t_curr_res = 0;
  	return tic;
  }
  
  /*
   * After the first stage of log recovery is done, we know where the head and
   * tail of the log are. We need this log initialisation done before we can
   * initialise the first CIL checkpoint context.
   *
   * Here we allocate a log ticket to track space usage during a CIL push.  This
   * ticket is passed to xlog_write() directly so that we don't slowly leak log
   * space by failing to account for space used by log headers and additional
   * region headers for split regions.
   */
  void
  xlog_cil_init_post_recovery(

  	struct xlog	*log)

  {

  	log->l_cilp->xc_ctx->ticket = xlog_cil_ticket_alloc(log);
  	log->l_cilp->xc_ctx->sequence = 1;
  	log->l_cilp->xc_ctx->commit_lsn = xlog_assign_lsn(log->l_curr_cycle,
  								log->l_curr_block);
  }
  
  /*

   * Prepare the log item for insertion into the CIL. Calculate the difference in
   * log space and vectors it will consume, and if it is a new item pin it as
   * well.
   */
  STATIC void
  xfs_cil_prepare_item(
  	struct xlog		*log,
  	struct xfs_log_vec	*lv,
  	struct xfs_log_vec	*old_lv,
  	int			*diff_len,
  	int			*diff_iovecs)
  {
  	/* Account for the new LV being passed in */
  	if (lv->lv_buf_len != XFS_LOG_VEC_ORDERED) {
  		*diff_len += lv->lv_buf_len;
  		*diff_iovecs += lv->lv_niovecs;
  	}
  
  	/*
  	 * If there is no old LV, this is the first time we've seen the item in
  	 * this CIL context and so we need to pin it. If we are replacing the
  	 * old_lv, then remove the space it accounts for and free it.
  	 */
  	if (!old_lv)
  		lv->lv_item->li_ops->iop_pin(lv->lv_item);
  	else if (old_lv != lv) {
  		ASSERT(lv->lv_buf_len != XFS_LOG_VEC_ORDERED);
  
  		*diff_len -= old_lv->lv_buf_len;
  		*diff_iovecs -= old_lv->lv_niovecs;
  		kmem_free(old_lv);
  	}
  
  	/* attach new log vector to log item */
  	lv->lv_item->li_lv = lv;
  
  	/*
  	 * If this is the first time the item is being committed to the
  	 * CIL, store the sequence number on the log item so we can
  	 * tell in future commits whether this is the first checkpoint
  	 * the item is being committed into.
  	 */
  	if (!lv->lv_item->li_seq)
  		lv->lv_item->li_seq = log->l_cilp->xc_ctx->sequence;
  }
  
  /*

   * Format log item into a flat buffers
   *
   * For delayed logging, we need to hold a formatted buffer containing all the
   * changes on the log item. This enables us to relog the item in memory and
   * write it out asynchronously without needing to relock the object that was
   * modified at the time it gets written into the iclog.
   *
   * This function builds a vector for the changes in each log item in the
   * transaction. It then works out the length of the buffer needed for each log
   * item, allocates them and formats the vector for the item into the buffer.
   * The buffer is then attached to the log item are then inserted into the
   * Committed Item List for tracking until the next checkpoint is written out.
   *
   * We don't set up region headers during this process; we simply copy the
   * regions into the flat buffer. We can do this because we still have to do a
   * formatting step to write the regions into the iclog buffer.  Writing the
   * ophdrs during the iclog write means that we can support splitting large
   * regions across iclog boundares without needing a change in the format of the
   * item/region encapsulation.
   *
   * Hence what we need to do now is change the rewrite the vector array to point
   * to the copied region inside the buffer we just allocated. This allows us to
   * format the regions into the iclog as though they are being formatted
   * directly out of the objects themselves.
   */

  static void
  xlog_cil_insert_format_items(
  	struct xlog		*log,
  	struct xfs_trans	*tp,
  	int			*diff_len,
  	int			*diff_iovecs)

  {

  	struct xfs_log_item_desc *lidp;

  
  	/* Bail out if we didn't find a log item.  */
  	if (list_empty(&tp->t_items)) {
  		ASSERT(0);

  		return;

  	}
  
  	list_for_each_entry(lidp, &tp->t_items, lid_trans) {

  		struct xfs_log_item *lip = lidp->lid_item;

  		struct xfs_log_vec *lv;

  		struct xfs_log_vec *old_lv;

  		int	niovecs = 0;
  		int	nbytes = 0;
  		int	buf_size;

  		bool	ordered = false;

  		/* Skip items which aren't dirty in this transaction. */
  		if (!(lidp->lid_flags & XFS_LID_DIRTY))
  			continue;

  		/* get number of vecs and size of data to be stored */
  		lip->li_ops->iop_size(lip, &niovecs, &nbytes);

  		/* Skip items that do not have any vectors for writing */

  		if (!niovecs)

  			continue;

  		/*
  		 * Ordered items need to be tracked but we do not wish to write
  		 * them. We need a logvec to track the object, but we do not
  		 * need an iovec or buffer to be allocated for copying data.
  		 */
  		if (niovecs == XFS_LOG_VEC_ORDERED) {
  			ordered = true;
  			niovecs = 0;

  			nbytes = 0;

  		}

  		/*
  		 * We 64-bit align the length of each iovec so that the start
  		 * of the next one is naturally aligned.  We'll need to

  		 * account for that slack space here. Then round nbytes up
  		 * to 64-bit alignment so that the initial buffer alignment is
  		 * easy to calculate and verify.

  		 */
  		nbytes += niovecs * sizeof(uint64_t);

  		nbytes = round_up(nbytes, sizeof(uint64_t));

  		/* grab the old item if it exists for reservation accounting */
  		old_lv = lip->li_lv;

  		/*
  		 * The data buffer needs to start 64-bit aligned, so round up
  		 * that space to ensure we can align it appropriately and not
  		 * overrun the buffer.
  		 */
  		buf_size = nbytes +
  			   round_up((sizeof(struct xfs_log_vec) +
  				     niovecs * sizeof(struct xfs_log_iovec)),
  				    sizeof(uint64_t));

  		/* compare to existing item size */
  		if (lip->li_lv && buf_size <= lip->li_lv->lv_size) {
  			/* same or smaller, optimise common overwrite case */
  			lv = lip->li_lv;
  			lv->lv_next = NULL;
  
  			if (ordered)
  				goto insert;

  			/*
  			 * set the item up as though it is a new insertion so
  			 * that the space reservation accounting is correct.
  			 */
  			*diff_iovecs -= lv->lv_niovecs;
  			*diff_len -= lv->lv_buf_len;

  		} else {
  			/* allocate new data chunk */
  			lv = kmem_zalloc(buf_size, KM_SLEEP|KM_NOFS);
  			lv->lv_item = lip;
  			lv->lv_size = buf_size;
  			if (ordered) {
  				/* track as an ordered logvec */
  				ASSERT(lip->li_lv == NULL);
  				lv->lv_buf_len = XFS_LOG_VEC_ORDERED;
  				goto insert;
  			}
  			lv->lv_iovecp = (struct xfs_log_iovec *)&lv[1];

  		}

  		/* Ensure the lv is set up according to ->iop_size */

  		lv->lv_niovecs = niovecs;

  		/* The allocated data region lies beyond the iovec region */

  		lv->lv_buf_len = 0;

  		lv->lv_buf = (char *)lv + buf_size - nbytes;

  		ASSERT(IS_ALIGNED((unsigned long)lv->lv_buf, sizeof(uint64_t)));

  		lip->li_ops->iop_format(lip, lv);

  insert:

  		ASSERT(lv->lv_buf_len <= nbytes);

  		xfs_cil_prepare_item(log, lv, old_lv, diff_len, diff_iovecs);

  	}

  }
  
  /*
   * Insert the log items into the CIL and calculate the difference in space
   * consumed by the item. Add the space to the checkpoint ticket and calculate
   * if the change requires additional log metadata. If it does, take that space

   * as well. Remove the amount of space we added to the checkpoint ticket from

   * the current transaction ticket so that the accounting works out correctly.
   */

  static void
  xlog_cil_insert_items(

  	struct xlog		*log,

  	struct xfs_trans	*tp)

  {

  	struct xfs_cil		*cil = log->l_cilp;
  	struct xfs_cil_ctx	*ctx = cil->xc_ctx;

  	struct xfs_log_item_desc *lidp;

  	int			len = 0;
  	int			diff_iovecs = 0;
  	int			iclog_space;

  	ASSERT(tp);

  
  	/*

  	 * We can do this safely because the context can't checkpoint until we
  	 * are done so it doesn't matter exactly how we update the CIL.
  	 */

  	xlog_cil_insert_format_items(log, tp, &len, &diff_iovecs);
  
  	/*
  	 * Now (re-)position everything modified at the tail of the CIL.
  	 * We do this here so we only need to take the CIL lock once during
  	 * the transaction commit.
  	 */

  	spin_lock(&cil->xc_cil_lock);

  	list_for_each_entry(lidp, &tp->t_items, lid_trans) {
  		struct xfs_log_item	*lip = lidp->lid_item;

  		/* Skip items which aren't dirty in this transaction. */
  		if (!(lidp->lid_flags & XFS_LID_DIRTY))
  			continue;

  		list_move_tail(&lip->li_cil, &cil->xc_cil);

  	}

  	/* account for space used by new iovec headers  */
  	len += diff_iovecs * sizeof(xlog_op_header_t);

  	ctx->nvecs += diff_iovecs;

  	/* attach the transaction to the CIL if it has any busy extents */
  	if (!list_empty(&tp->t_busy))
  		list_splice_init(&tp->t_busy, &ctx->busy_extents);

  	/*
  	 * Now transfer enough transaction reservation to the context ticket
  	 * for the checkpoint. The context ticket is special - the unit
  	 * reservation has to grow as well as the current reservation as we
  	 * steal from tickets so we can correctly determine the space used
  	 * during the transaction commit.
  	 */
  	if (ctx->ticket->t_curr_res == 0) {

  		ctx->ticket->t_curr_res = ctx->ticket->t_unit_res;

  		tp->t_ticket->t_curr_res -= ctx->ticket->t_unit_res;

  	}
  
  	/* do we need space for more log record headers? */
  	iclog_space = log->l_iclog_size - log->l_iclog_hsize;
  	if (len > 0 && (ctx->space_used / iclog_space !=
  				(ctx->space_used + len) / iclog_space)) {
  		int hdrs;
  
  		hdrs = (len + iclog_space - 1) / iclog_space;
  		/* need to take into account split region headers, too */
  		hdrs *= log->l_iclog_hsize + sizeof(struct xlog_op_header);
  		ctx->ticket->t_unit_res += hdrs;
  		ctx->ticket->t_curr_res += hdrs;

  		tp->t_ticket->t_curr_res -= hdrs;
  		ASSERT(tp->t_ticket->t_curr_res >= len);

  	}

  	tp->t_ticket->t_curr_res -= len;

  	ctx->space_used += len;
  
  	spin_unlock(&cil->xc_cil_lock);

  }
  
  static void
  xlog_cil_free_logvec(
  	struct xfs_log_vec	*log_vector)
  {
  	struct xfs_log_vec	*lv;
  
  	for (lv = log_vector; lv; ) {
  		struct xfs_log_vec *next = lv->lv_next;

  		kmem_free(lv);
  		lv = next;
  	}
  }
  
  /*

   * Mark all items committed and clear busy extents. We free the log vector
   * chains in a separate pass so that we unpin the log items as quickly as
   * possible.
   */
  static void
  xlog_cil_committed(
  	void	*args,
  	int	abort)
  {
  	struct xfs_cil_ctx	*ctx = args;

  	struct xfs_mount	*mp = ctx->cil->xc_log->l_mp;

  	xfs_trans_committed_bulk(ctx->cil->xc_log->l_ailp, ctx->lv_chain,
  					ctx->start_lsn, abort);

  	xfs_extent_busy_sort(&ctx->busy_extents);
  	xfs_extent_busy_clear(mp, &ctx->busy_extents,

  			     (mp->m_flags & XFS_MOUNT_DISCARD) && !abort);

  	spin_lock(&ctx->cil->xc_push_lock);

  	list_del(&ctx->committing);

  	spin_unlock(&ctx->cil->xc_push_lock);

  
  	xlog_cil_free_logvec(ctx->lv_chain);

  
  	if (!list_empty(&ctx->busy_extents)) {
  		ASSERT(mp->m_flags & XFS_MOUNT_DISCARD);
  
  		xfs_discard_extents(mp, &ctx->busy_extents);

  		xfs_extent_busy_clear(mp, &ctx->busy_extents, false);

  	}

  	kmem_free(ctx);
  }
  
  /*

   * Push the Committed Item List to the log. If @push_seq flag is zero, then it
   * is a background flush and so we can chose to ignore it. Otherwise, if the
   * current sequence is the same as @push_seq we need to do a flush. If
   * @push_seq is less than the current sequence, then it has already been
   * flushed and we don't need to do anything - the caller will wait for it to
   * complete if necessary.
   *
   * @push_seq is a value rather than a flag because that allows us to do an
   * unlocked check of the sequence number for a match. Hence we can allows log
   * forces to run racily and not issue pushes for the same sequence twice. If we
   * get a race between multiple pushes for the same sequence they will block on
   * the first one and then abort, hence avoiding needless pushes.

   */

  STATIC int

  xlog_cil_push(

  	struct xlog		*log)

  {
  	struct xfs_cil		*cil = log->l_cilp;
  	struct xfs_log_vec	*lv;
  	struct xfs_cil_ctx	*ctx;
  	struct xfs_cil_ctx	*new_ctx;
  	struct xlog_in_core	*commit_iclog;
  	struct xlog_ticket	*tic;

  	int			num_iovecs;

  	int			error = 0;
  	struct xfs_trans_header thdr;
  	struct xfs_log_iovec	lhdr;
  	struct xfs_log_vec	lvhdr = { NULL };
  	xfs_lsn_t		commit_lsn;

  	xfs_lsn_t		push_seq;

  
  	if (!cil)
  		return 0;

  	new_ctx = kmem_zalloc(sizeof(*new_ctx), KM_SLEEP|KM_NOFS);
  	new_ctx->ticket = xlog_cil_ticket_alloc(log);

  	down_write(&cil->xc_ctx_lock);

  	ctx = cil->xc_ctx;

  	spin_lock(&cil->xc_push_lock);

  	push_seq = cil->xc_push_seq;
  	ASSERT(push_seq <= ctx->sequence);

  	/*
  	 * Check if we've anything to push. If there is nothing, then we don't
  	 * move on to a new sequence number and so we have to be able to push
  	 * this sequence again later.
  	 */
  	if (list_empty(&cil->xc_cil)) {
  		cil->xc_push_seq = 0;

  		spin_unlock(&cil->xc_push_lock);

  		goto out_skip;

  	}

  	spin_unlock(&cil->xc_push_lock);

  
  	/* check for a previously pushed seqeunce */

  	if (push_seq < cil->xc_ctx->sequence)

  		goto out_skip;

  	/*
  	 * pull all the log vectors off the items in the CIL, and
  	 * remove the items from the CIL. We don't need the CIL lock
  	 * here because it's only needed on the transaction commit
  	 * side which is currently locked out by the flush lock.
  	 */
  	lv = NULL;

  	num_iovecs = 0;

  	while (!list_empty(&cil->xc_cil)) {
  		struct xfs_log_item	*item;

  
  		item = list_first_entry(&cil->xc_cil,
  					struct xfs_log_item, li_cil);
  		list_del_init(&item->li_cil);
  		if (!ctx->lv_chain)
  			ctx->lv_chain = item->li_lv;
  		else
  			lv->lv_next = item->li_lv;
  		lv = item->li_lv;
  		item->li_lv = NULL;

  		num_iovecs += lv->lv_niovecs;

  	}
  
  	/*
  	 * initialise the new context and attach it to the CIL. Then attach
  	 * the current context to the CIL committing lsit so it can be found
  	 * during log forces to extract the commit lsn of the sequence that
  	 * needs to be forced.
  	 */
  	INIT_LIST_HEAD(&new_ctx->committing);
  	INIT_LIST_HEAD(&new_ctx->busy_extents);
  	new_ctx->sequence = ctx->sequence + 1;
  	new_ctx->cil = cil;
  	cil->xc_ctx = new_ctx;
  
  	/*
  	 * The switch is now done, so we can drop the context lock and move out
  	 * of a shared context. We can't just go straight to the commit record,
  	 * though - we need to synchronise with previous and future commits so
  	 * that the commit records are correctly ordered in the log to ensure
  	 * that we process items during log IO completion in the correct order.
  	 *
  	 * For example, if we get an EFI in one checkpoint and the EFD in the
  	 * next (e.g. due to log forces), we do not want the checkpoint with
  	 * the EFD to be committed before the checkpoint with the EFI.  Hence
  	 * we must strictly order the commit records of the checkpoints so
  	 * that: a) the checkpoint callbacks are attached to the iclogs in the
  	 * correct order; and b) the checkpoints are replayed in correct order
  	 * in log recovery.
  	 *
  	 * Hence we need to add this context to the committing context list so
  	 * that higher sequences will wait for us to write out a commit record
  	 * before they do.

  	 *
  	 * xfs_log_force_lsn requires us to mirror the new sequence into the cil
  	 * structure atomically with the addition of this sequence to the
  	 * committing list. This also ensures that we can do unlocked checks
  	 * against the current sequence in log forces without risking
  	 * deferencing a freed context pointer.

  	 */

  	spin_lock(&cil->xc_push_lock);

  	cil->xc_current_sequence = new_ctx->sequence;

  	list_add(&ctx->committing, &cil->xc_committing);

  	spin_unlock(&cil->xc_push_lock);

  	up_write(&cil->xc_ctx_lock);
  
  	/*
  	 * Build a checkpoint transaction header and write it to the log to
  	 * begin the transaction. We need to account for the space used by the
  	 * transaction header here as it is not accounted for in xlog_write().
  	 *
  	 * The LSN we need to pass to the log items on transaction commit is
  	 * the LSN reported by the first log vector write. If we use the commit
  	 * record lsn then we can move the tail beyond the grant write head.
  	 */
  	tic = ctx->ticket;
  	thdr.th_magic = XFS_TRANS_HEADER_MAGIC;
  	thdr.th_type = XFS_TRANS_CHECKPOINT;
  	thdr.th_tid = tic->t_tid;
  	thdr.th_num_items = num_iovecs;

  	lhdr.i_addr = &thdr;

  	lhdr.i_len = sizeof(xfs_trans_header_t);
  	lhdr.i_type = XLOG_REG_TYPE_TRANSHDR;
  	tic->t_curr_res -= lhdr.i_len + sizeof(xlog_op_header_t);
  
  	lvhdr.lv_niovecs = 1;
  	lvhdr.lv_iovecp = &lhdr;
  	lvhdr.lv_next = ctx->lv_chain;
  
  	error = xlog_write(log, &lvhdr, tic, &ctx->start_lsn, NULL, 0);
  	if (error)

  		goto out_abort_free_ticket;

  
  	/*
  	 * now that we've written the checkpoint into the log, strictly
  	 * order the commit records so replay will get them in the right order.
  	 */
  restart:

  	spin_lock(&cil->xc_push_lock);

  	list_for_each_entry(new_ctx, &cil->xc_committing, committing) {
  		/*
  		 * Higher sequences will wait for this one so skip them.
  		 * Don't wait for own own sequence, either.
  		 */
  		if (new_ctx->sequence >= ctx->sequence)
  			continue;
  		if (!new_ctx->commit_lsn) {
  			/*
  			 * It is still being pushed! Wait for the push to
  			 * complete, then start again from the beginning.
  			 */

  			xlog_wait(&cil->xc_commit_wait, &cil->xc_push_lock);

  			goto restart;
  		}
  	}

  	spin_unlock(&cil->xc_push_lock);

  	/* xfs_log_done always frees the ticket on error. */

  	commit_lsn = xfs_log_done(log->l_mp, tic, &commit_iclog, 0);

  	if (commit_lsn == -1)

  		goto out_abort;
  
  	/* attach all the transactions w/ busy extents to iclog */
  	ctx->log_cb.cb_func = xlog_cil_committed;
  	ctx->log_cb.cb_arg = ctx;
  	error = xfs_log_notify(log->l_mp, commit_iclog, &ctx->log_cb);
  	if (error)
  		goto out_abort;
  
  	/*
  	 * now the checkpoint commit is complete and we've attached the
  	 * callbacks to the iclog we can assign the commit LSN to the context
  	 * and wake up anyone who is waiting for the commit to complete.
  	 */

  	spin_lock(&cil->xc_push_lock);

  	ctx->commit_lsn = commit_lsn;

  	wake_up_all(&cil->xc_commit_wait);

  	spin_unlock(&cil->xc_push_lock);

  
  	/* release the hounds! */
  	return xfs_log_release_iclog(log->l_mp, commit_iclog);
  
  out_skip:
  	up_write(&cil->xc_ctx_lock);
  	xfs_log_ticket_put(new_ctx->ticket);
  	kmem_free(new_ctx);
  	return 0;

  out_abort_free_ticket:
  	xfs_log_ticket_put(tic);

  out_abort:
  	xlog_cil_committed(ctx, XFS_LI_ABORTED);
  	return XFS_ERROR(EIO);
  }

  static void
  xlog_cil_push_work(
  	struct work_struct	*work)
  {
  	struct xfs_cil		*cil = container_of(work, struct xfs_cil,
  							xc_push_work);
  	xlog_cil_push(cil->xc_log);
  }
  
  /*
   * We need to push CIL every so often so we don't cache more than we can fit in
   * the log. The limit really is that a checkpoint can't be more than half the
   * log (the current checkpoint is not allowed to overwrite the previous
   * checkpoint), but commit latency and memory usage limit this to a smaller
   * size.
   */
  static void
  xlog_cil_push_background(

  	struct xlog	*log)

  {
  	struct xfs_cil	*cil = log->l_cilp;
  
  	/*
  	 * The cil won't be empty because we are called while holding the
  	 * context lock so whatever we added to the CIL will still be there
  	 */
  	ASSERT(!list_empty(&cil->xc_cil));
  
  	/*
  	 * don't do a background push if we haven't used up all the
  	 * space available yet.
  	 */
  	if (cil->xc_ctx->space_used < XLOG_CIL_SPACE_LIMIT(log))
  		return;

  	spin_lock(&cil->xc_push_lock);

  	if (cil->xc_push_seq < cil->xc_current_sequence) {
  		cil->xc_push_seq = cil->xc_current_sequence;
  		queue_work(log->l_mp->m_cil_workqueue, &cil->xc_push_work);
  	}

  	spin_unlock(&cil->xc_push_lock);

  
  }

  /*
   * xlog_cil_push_now() is used to trigger an immediate CIL push to the sequence
   * number that is passed. When it returns, the work will be queued for
   * @push_seq, but it won't be completed. The caller is expected to do any
   * waiting for push_seq to complete if it is required.
   */

  static void

  xlog_cil_push_now(

  	struct xlog	*log,

  	xfs_lsn_t	push_seq)
  {
  	struct xfs_cil	*cil = log->l_cilp;
  
  	if (!cil)
  		return;
  
  	ASSERT(push_seq && push_seq <= cil->xc_current_sequence);
  
  	/* start on any pending background push to minimise wait time on it */
  	flush_work(&cil->xc_push_work);
  
  	/*
  	 * If the CIL is empty or we've already pushed the sequence then
  	 * there's no work we need to do.
  	 */

  	spin_lock(&cil->xc_push_lock);

  	if (list_empty(&cil->xc_cil) || push_seq <= cil->xc_push_seq) {

  		spin_unlock(&cil->xc_push_lock);

  		return;
  	}
  
  	cil->xc_push_seq = push_seq;

  	queue_work(log->l_mp->m_cil_workqueue, &cil->xc_push_work);

  	spin_unlock(&cil->xc_push_lock);

  }

  bool
  xlog_cil_empty(
  	struct xlog	*log)
  {
  	struct xfs_cil	*cil = log->l_cilp;
  	bool		empty = false;
  
  	spin_lock(&cil->xc_push_lock);
  	if (list_empty(&cil->xc_cil))
  		empty = true;
  	spin_unlock(&cil->xc_push_lock);
  	return empty;
  }

  /*

   * Commit a transaction with the given vector to the Committed Item List.
   *
   * To do this, we need to format the item, pin it in memory if required and
   * account for the space used by the transaction. Once we have done that we
   * need to release the unused reservation for the transaction, attach the
   * transaction to the checkpoint context so we carry the busy extents through
   * to checkpoint completion, and then unlock all the items in the transaction.
   *

   * Called with the context lock already held in read mode to lock out
   * background commit, returns without it held once background commits are
   * allowed again.
   */

  void

  xfs_log_commit_cil(
  	struct xfs_mount	*mp,
  	struct xfs_trans	*tp,

  	xfs_lsn_t		*commit_lsn,
  	int			flags)
  {

  	struct xlog		*log = mp->m_log;

  	struct xfs_cil		*cil = log->l_cilp;

  	int			log_flags = 0;

  
  	if (flags & XFS_TRANS_RELEASE_LOG_RES)
  		log_flags = XFS_LOG_REL_PERM_RESERV;

  	/* lock out background commit */

  	down_read(&cil->xc_ctx_lock);

  	xlog_cil_insert_items(log, tp);

  
  	/* check we didn't blow the reservation */
  	if (tp->t_ticket->t_curr_res < 0)

  		xlog_print_tic_res(mp, tp->t_ticket);

  	tp->t_commit_lsn = cil->xc_ctx->sequence;
  	if (commit_lsn)
  		*commit_lsn = tp->t_commit_lsn;

  	xfs_log_done(mp, tp->t_ticket, NULL, log_flags);
  	xfs_trans_unreserve_and_mod_sb(tp);
  
  	/*
  	 * Once all the items of the transaction have been copied to the CIL,
  	 * the items can be unlocked and freed.
  	 *
  	 * This needs to be done before we drop the CIL context lock because we
  	 * have to update state in the log items and unlock them before they go
  	 * to disk. If we don't, then the CIL checkpoint can race with us and
  	 * we can run checkpoint completion before we've updated and unlocked
  	 * the log items. This affects (at least) processing of stale buffers,
  	 * inodes and EFIs.
  	 */

  	xfs_trans_free_items(tp, tp->t_commit_lsn, 0);

  	xlog_cil_push_background(log);

  	up_read(&cil->xc_ctx_lock);

  }
  
  /*

   * Conditionally push the CIL based on the sequence passed in.
   *
   * We only need to push if we haven't already pushed the sequence
   * number given. Hence the only time we will trigger a push here is
   * if the push sequence is the same as the current context.
   *
   * We return the current commit lsn to allow the callers to determine if a
   * iclog flush is necessary following this call.

   */
  xfs_lsn_t

  xlog_cil_force_lsn(

  	struct xlog	*log,

  	xfs_lsn_t	sequence)

  {
  	struct xfs_cil		*cil = log->l_cilp;
  	struct xfs_cil_ctx	*ctx;
  	xfs_lsn_t		commit_lsn = NULLCOMMITLSN;

  	ASSERT(sequence <= cil->xc_current_sequence);
  
  	/*
  	 * check to see if we need to force out the current context.
  	 * xlog_cil_push() handles racing pushes for the same sequence,
  	 * so no need to deal with it here.
  	 */

  restart:
  	xlog_cil_push_now(log, sequence);

  
  	/*
  	 * See if we can find a previous sequence still committing.

  	 * We need to wait for all previous sequence commits to complete
  	 * before allowing the force of push_seq to go ahead. Hence block
  	 * on commits for those as well.
  	 */

  	spin_lock(&cil->xc_push_lock);

  	list_for_each_entry(ctx, &cil->xc_committing, committing) {

  		if (ctx->sequence > sequence)

  			continue;
  		if (!ctx->commit_lsn) {
  			/*
  			 * It is still being pushed! Wait for the push to
  			 * complete, then start again from the beginning.
  			 */

  			xlog_wait(&cil->xc_commit_wait, &cil->xc_push_lock);

  			goto restart;
  		}

  		if (ctx->sequence != sequence)

  			continue;
  		/* found it! */
  		commit_lsn = ctx->commit_lsn;
  	}

  
  	/*
  	 * The call to xlog_cil_push_now() executes the push in the background.
  	 * Hence by the time we have got here it our sequence may not have been
  	 * pushed yet. This is true if the current sequence still matches the
  	 * push sequence after the above wait loop and the CIL still contains
  	 * dirty objects.
  	 *
  	 * When the push occurs, it will empty the CIL and
  	 * atomically increment the currect sequence past the push sequence and
  	 * move it into the committing list. Of course, if the CIL is clean at
  	 * the time of the push, it won't have pushed the CIL at all, so in that
  	 * case we should try the push for this sequence again from the start
  	 * just in case.
  	 */
  
  	if (sequence == cil->xc_current_sequence &&
  	    !list_empty(&cil->xc_cil)) {
  		spin_unlock(&cil->xc_push_lock);
  		goto restart;
  	}

  	spin_unlock(&cil->xc_push_lock);

  	return commit_lsn;
  }

  
  /*
   * Check if the current log item was first committed in this sequence.
   * We can't rely on just the log item being in the CIL, we have to check
   * the recorded commit sequence number.
   *
   * Note: for this to be used in a non-racy manner, it has to be called with
   * CIL flushing locked out. As a result, it should only be used during the
   * transaction commit process when deciding what to format into the item.
   */
  bool
  xfs_log_item_in_current_chkpt(
  	struct xfs_log_item *lip)
  {
  	struct xfs_cil_ctx *ctx;

  	if (list_empty(&lip->li_cil))
  		return false;
  
  	ctx = lip->li_mountp->m_log->l_cilp->xc_ctx;
  
  	/*
  	 * li_seq is written on the first commit of a log item to record the
  	 * first checkpoint it is written to. Hence if it is different to the
  	 * current sequence, we're in a new checkpoint.
  	 */
  	if (XFS_LSN_CMP(lip->li_seq, ctx->sequence) != 0)
  		return false;
  	return true;
  }

  
  /*
   * Perform initial CIL structure initialisation.
   */
  int
  xlog_cil_init(

  	struct xlog	*log)

  {
  	struct xfs_cil	*cil;
  	struct xfs_cil_ctx *ctx;
  
  	cil = kmem_zalloc(sizeof(*cil), KM_SLEEP|KM_MAYFAIL);
  	if (!cil)
  		return ENOMEM;
  
  	ctx = kmem_zalloc(sizeof(*ctx), KM_SLEEP|KM_MAYFAIL);
  	if (!ctx) {
  		kmem_free(cil);
  		return ENOMEM;
  	}
  
  	INIT_WORK(&cil->xc_push_work, xlog_cil_push_work);
  	INIT_LIST_HEAD(&cil->xc_cil);
  	INIT_LIST_HEAD(&cil->xc_committing);
  	spin_lock_init(&cil->xc_cil_lock);

  	spin_lock_init(&cil->xc_push_lock);

  	init_rwsem(&cil->xc_ctx_lock);
  	init_waitqueue_head(&cil->xc_commit_wait);
  
  	INIT_LIST_HEAD(&ctx->committing);
  	INIT_LIST_HEAD(&ctx->busy_extents);
  	ctx->sequence = 1;
  	ctx->cil = cil;
  	cil->xc_ctx = ctx;
  	cil->xc_current_sequence = ctx->sequence;
  
  	cil->xc_log = log;
  	log->l_cilp = cil;
  	return 0;
  }
  
  void
  xlog_cil_destroy(

  	struct xlog	*log)

  {
  	if (log->l_cilp->xc_ctx) {
  		if (log->l_cilp->xc_ctx->ticket)
  			xfs_log_ticket_put(log->l_cilp->xc_ctx->ticket);
  		kmem_free(log->l_cilp->xc_ctx);
  	}
  
  	ASSERT(list_empty(&log->l_cilp->xc_cil));
  	kmem_free(log->l_cilp);
  }