1 files changed, 360 insertions, 112 deletions

diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index db6cb7800251..eccbfb99e894 100644
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -44,9 +44,20 @@ xlog_cil_ticket_alloc(
 	 * transaction overhead reservation from the first transaction commit.
 	 */
 	tic->t_curr_res = 0;
+	tic->t_iclog_hdrs = 0;
 	return tic;
 }
 
+static inline void
+xlog_cil_set_iclog_hdr_count(struct xfs_cil *cil)
+{
+	struct xlog	*log = cil->xc_log;
+
+	atomic_set(&cil->xc_iclog_hdrs,
+		   (XLOG_CIL_BLOCKING_SPACE_LIMIT(log) /
+			(log->l_iclog_size - log->l_iclog_hsize)));
+}
+
 /*
  * 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
@@ -61,7 +72,7 @@ xlog_item_in_current_chkpt(
 	struct xfs_cil		*cil,
 	struct xfs_log_item	*lip)
 {
-	if (list_empty(&lip->li_cil))
+	if (test_bit(XLOG_CIL_EMPTY, &cil->xc_flags))
 		return false;
 
 	/*
@@ -93,15 +104,88 @@ xlog_cil_ctx_alloc(void)
 	ctx = kmem_zalloc(sizeof(*ctx), KM_NOFS);
 	INIT_LIST_HEAD(&ctx->committing);
 	INIT_LIST_HEAD(&ctx->busy_extents);
+	INIT_LIST_HEAD(&ctx->log_items);
+	INIT_LIST_HEAD(&ctx->lv_chain);
 	INIT_WORK(&ctx->push_work, xlog_cil_push_work);
 	return ctx;
 }
 
+/*
+ * Aggregate the CIL per cpu structures into global counts, lists, etc and
+ * clear the percpu state ready for the next context to use. This is called
+ * from the push code with the context lock held exclusively, hence nothing else
+ * will be accessing or modifying the per-cpu counters.
+ */
+static void
+xlog_cil_push_pcp_aggregate(
+	struct xfs_cil		*cil,
+	struct xfs_cil_ctx	*ctx)
+{
+	struct xlog_cil_pcp	*cilpcp;
+	int			cpu;
+
+	for_each_online_cpu(cpu) {
+		cilpcp = per_cpu_ptr(cil->xc_pcp, cpu);
+
+		ctx->ticket->t_curr_res += cilpcp->space_reserved;
+		cilpcp->space_reserved = 0;
+
+		if (!list_empty(&cilpcp->busy_extents)) {
+			list_splice_init(&cilpcp->busy_extents,
+					&ctx->busy_extents);
+		}
+		if (!list_empty(&cilpcp->log_items))
+			list_splice_init(&cilpcp->log_items, &ctx->log_items);
+
+		/*
+		 * We're in the middle of switching cil contexts.  Reset the
+		 * counter we use to detect when the current context is nearing
+		 * full.
+		 */
+		cilpcp->space_used = 0;
+	}
+}
+
+/*
+ * Aggregate the CIL per-cpu space used counters into the global atomic value.
+ * This is called when the per-cpu counter aggregation will first pass the soft
+ * limit threshold so we can switch to atomic counter aggregation for accurate
+ * detection of hard limit traversal.
+ */
+static void
+xlog_cil_insert_pcp_aggregate(
+	struct xfs_cil		*cil,
+	struct xfs_cil_ctx	*ctx)
+{
+	struct xlog_cil_pcp	*cilpcp;
+	int			cpu;
+	int			count = 0;
+
+	/* Trigger atomic updates then aggregate only for the first caller */
+	if (!test_and_clear_bit(XLOG_CIL_PCP_SPACE, &cil->xc_flags))
+		return;
+
+	for_each_online_cpu(cpu) {
+		int	old, prev;
+
+		cilpcp = per_cpu_ptr(cil->xc_pcp, cpu);
+		do {
+			old = cilpcp->space_used;
+			prev = cmpxchg(&cilpcp->space_used, old, 0);
+		} while (old != prev);
+		count += old;
+	}
+	atomic_add(count, &ctx->space_used);
+}
+
 static void
 xlog_cil_ctx_switch(
 	struct xfs_cil		*cil,
 	struct xfs_cil_ctx	*ctx)
 {
+	xlog_cil_set_iclog_hdr_count(cil);
+	set_bit(XLOG_CIL_EMPTY, &cil->xc_flags);
+	set_bit(XLOG_CIL_PCP_SPACE, &cil->xc_flags);
 	ctx->sequence = ++cil->xc_current_sequence;
 	ctx->cil = cil;
 	cil->xc_ctx = ctx;
@@ -123,6 +207,7 @@ xlog_cil_init_post_recovery(
 {
 	log->l_cilp->xc_ctx->ticket = xlog_cil_ticket_alloc(log);
 	log->l_cilp->xc_ctx->sequence = 1;
+	xlog_cil_set_iclog_hdr_count(log->l_cilp);
 }
 
 static inline int
@@ -254,6 +339,7 @@ xlog_cil_alloc_shadow_bufs(
 
 			memset(lv, 0, xlog_cil_iovec_space(niovecs));
 
+			INIT_LIST_HEAD(&lv->lv_list);
 			lv->lv_item = lip;
 			lv->lv_size = buf_size;
 			if (ordered)
@@ -269,7 +355,6 @@ xlog_cil_alloc_shadow_bufs(
 			else
 				lv->lv_buf_len = 0;
 			lv->lv_bytes = 0;
-			lv->lv_next = NULL;
 		}
 
 		/* Ensure the lv is set up according to ->iop_size */
@@ -396,7 +481,6 @@ xlog_cil_insert_format_items(
 		if (lip->li_lv && shadow->lv_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;
@@ -434,6 +518,23 @@ insert:
 }
 
 /*
+ * The use of lockless waitqueue_active() requires that the caller has
+ * serialised itself against the wakeup call in xlog_cil_push_work(). That
+ * can be done by either holding the push lock or the context lock.
+ */
+static inline bool
+xlog_cil_over_hard_limit(
+	struct xlog	*log,
+	int32_t		space_used)
+{
+	if (waitqueue_active(&log->l_cilp->xc_push_wait))
+		return true;
+	if (space_used >= XLOG_CIL_BLOCKING_SPACE_LIMIT(log))
+		return true;
+	return false;
+}
+
+/*
  * 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
@@ -450,8 +551,10 @@ xlog_cil_insert_items(
 	struct xfs_cil_ctx	*ctx = cil->xc_ctx;
 	struct xfs_log_item	*lip;
 	int			len = 0;
-	int			iclog_space;
 	int			iovhdr_res = 0, split_res = 0, ctx_res = 0;
+	int			space_used;
+	int			order;
+	struct xlog_cil_pcp	*cilpcp;
 
 	ASSERT(tp);
 
@@ -461,93 +564,135 @@ xlog_cil_insert_items(
 	 */
 	xlog_cil_insert_format_items(log, tp, &len);
 
-	spin_lock(&cil->xc_cil_lock);
+	/*
+	 * Subtract the space released by intent cancelation from the space we
+	 * consumed so that we remove it from the CIL space and add it back to
+	 * the current transaction reservation context.
+	 */
+	len -= released_space;
 
-	/* 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);
+	/*
+	 * Grab the per-cpu pointer for the CIL before we start any accounting.
+	 * That ensures that we are running with pre-emption disabled and so we
+	 * can't be scheduled away between split sample/update operations that
+	 * are done without outside locking to serialise them.
+	 */
+	cilpcp = get_cpu_ptr(cil->xc_pcp);
 
 	/*
-	 * 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.
+	 * We need to take the CIL checkpoint unit reservation on the first
+	 * commit into the CIL. Test the XLOG_CIL_EMPTY bit first so we don't
+	 * unnecessarily do an atomic op in the fast path here. We can clear the
+	 * XLOG_CIL_EMPTY bit as we are under the xc_ctx_lock here and that
+	 * needs to be held exclusively to reset the XLOG_CIL_EMPTY bit.
 	 */
-	if (ctx->ticket->t_curr_res == 0) {
+	if (test_bit(XLOG_CIL_EMPTY, &cil->xc_flags) &&
+	    test_and_clear_bit(XLOG_CIL_EMPTY, &cil->xc_flags))
 		ctx_res = ctx->ticket->t_unit_res;
-		ctx->ticket->t_curr_res = ctx_res;
-		tp->t_ticket->t_curr_res -= ctx_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)) {
-		split_res = (len + iclog_space - 1) / iclog_space;
-		/* need to take into account split region headers, too */
-		split_res *= log->l_iclog_hsize + sizeof(struct xlog_op_header);
-		ctx->ticket->t_unit_res += split_res;
-		ctx->ticket->t_curr_res += split_res;
-		tp->t_ticket->t_curr_res -= split_res;
-		ASSERT(tp->t_ticket->t_curr_res >= len);
+	/*
+	 * Check if we need to steal iclog headers. atomic_read() is not a
+	 * locked atomic operation, so we can check the value before we do any
+	 * real atomic ops in the fast path. If we've already taken the CIL unit
+	 * reservation from this commit, we've already got one iclog header
+	 * space reserved so we have to account for that otherwise we risk
+	 * overrunning the reservation on this ticket.
+	 *
+	 * If the CIL is already at the hard limit, we might need more header
+	 * space that originally reserved. So steal more header space from every
+	 * commit that occurs once we are over the hard limit to ensure the CIL
+	 * push won't run out of reservation space.
+	 *
+	 * This can steal more than we need, but that's OK.
+	 *
+	 * The cil->xc_ctx_lock provides the serialisation necessary for safely
+	 * calling xlog_cil_over_hard_limit() in this context.
+	 */
+	space_used = atomic_read(&ctx->space_used) + cilpcp->space_used + len;
+	if (atomic_read(&cil->xc_iclog_hdrs) > 0 ||
+	    xlog_cil_over_hard_limit(log, space_used)) {
+		split_res = log->l_iclog_hsize +
+					sizeof(struct xlog_op_header);
+		if (ctx_res)
+			ctx_res += split_res * (tp->t_ticket->t_iclog_hdrs - 1);
+		else
+			ctx_res = split_res * tp->t_ticket->t_iclog_hdrs;
+		atomic_sub(tp->t_ticket->t_iclog_hdrs, &cil->xc_iclog_hdrs);
 	}
-	tp->t_ticket->t_curr_res -= len;
-	tp->t_ticket->t_curr_res += released_space;
-	ctx->space_used += len;
-	ctx->space_used -= released_space;
+	cilpcp->space_reserved += ctx_res;
 
 	/*
-	 * If we've overrun the reservation, dump the tx details before we move
-	 * the log items. Shutdown is imminent...
+	 * Accurately account when over the soft limit, otherwise fold the
+	 * percpu count into the global count if over the per-cpu threshold.
 	 */
-	if (WARN_ON(tp->t_ticket->t_curr_res < 0)) {
-		xfs_warn(log->l_mp, "Transaction log reservation overrun:");
-		xfs_warn(log->l_mp,
-			 "  log items: %d bytes (iov hdrs: %d bytes)",
-			 len, iovhdr_res);
-		xfs_warn(log->l_mp, "  split region headers: %d bytes",
-			 split_res);
-		xfs_warn(log->l_mp, "  ctx ticket: %d bytes", ctx_res);
-		xlog_print_trans(tp);
+	if (!test_bit(XLOG_CIL_PCP_SPACE, &cil->xc_flags)) {
+		atomic_add(len, &ctx->space_used);
+	} else if (cilpcp->space_used + len >
+			(XLOG_CIL_SPACE_LIMIT(log) / num_online_cpus())) {
+		space_used = atomic_add_return(cilpcp->space_used + len,
+						&ctx->space_used);
+		cilpcp->space_used = 0;
+
+		/*
+		 * If we just transitioned over the soft limit, we need to
+		 * transition to the global atomic counter.
+		 */
+		if (space_used >= XLOG_CIL_SPACE_LIMIT(log))
+			xlog_cil_insert_pcp_aggregate(cil, ctx);
+	} else {
+		cilpcp->space_used += len;
 	}
+	/* attach the transaction to the CIL if it has any busy extents */
+	if (!list_empty(&tp->t_busy))
+		list_splice_init(&tp->t_busy, &cilpcp->busy_extents);
 
 	/*
-	 * Now (re-)position everything modified at the tail of the CIL.
+	 * Now update the order of everything modified in the transaction
+	 * and insert items into the CIL if they aren't already there.
 	 * We do this here so we only need to take the CIL lock once during
 	 * the transaction commit.
 	 */
+	order = atomic_inc_return(&ctx->order_id);
 	list_for_each_entry(lip, &tp->t_items, li_trans) {
-
 		/* Skip items which aren't dirty in this transaction. */
 		if (!test_bit(XFS_LI_DIRTY, &lip->li_flags))
 			continue;
 
-		/*
-		 * Only move the item if it isn't already at the tail. This is
-		 * to prevent a transient list_empty() state when reinserting
-		 * an item that is already the only item in the CIL.
-		 */
-		if (!list_is_last(&lip->li_cil, &cil->xc_cil))
-			list_move_tail(&lip->li_cil, &cil->xc_cil);
+		lip->li_order_id = order;
+		if (!list_empty(&lip->li_cil))
+			continue;
+		list_add_tail(&lip->li_cil, &cilpcp->log_items);
 	}
+	put_cpu_ptr(cilpcp);
 
-	spin_unlock(&cil->xc_cil_lock);
-
-	if (tp->t_ticket->t_curr_res < 0)
+	/*
+	 * If we've overrun the reservation, dump the tx details before we move
+	 * the log items. Shutdown is imminent...
+	 */
+	tp->t_ticket->t_curr_res -= ctx_res + len;
+	if (WARN_ON(tp->t_ticket->t_curr_res < 0)) {
+		xfs_warn(log->l_mp, "Transaction log reservation overrun:");
+		xfs_warn(log->l_mp,
+			 "  log items: %d bytes (iov hdrs: %d bytes)",
+			 len, iovhdr_res);
+		xfs_warn(log->l_mp, "  split region headers: %d bytes",
+			 split_res);
+		xfs_warn(log->l_mp, "  ctx ticket: %d bytes", ctx_res);
+		xlog_print_trans(tp);
 		xlog_force_shutdown(log, SHUTDOWN_LOG_IO_ERROR);
+	}
 }
 
 static void
 xlog_cil_free_logvec(
-	struct xfs_log_vec	*log_vector)
+	struct list_head	*lv_chain)
 {
 	struct xfs_log_vec	*lv;
 
-	for (lv = log_vector; lv; ) {
-		struct xfs_log_vec *next = lv->lv_next;
+	while (!list_empty(lv_chain)) {
+		lv = list_first_entry(lv_chain, struct xfs_log_vec, lv_list);
+		list_del_init(&lv->lv_list);
 		kmem_free(lv);
-		lv = next;
 	}
 }
 
@@ -647,7 +792,7 @@ xlog_cil_committed(
 		spin_unlock(&ctx->cil->xc_push_lock);
 	}
 
-	xfs_trans_committed_bulk(ctx->cil->xc_log->l_ailp, ctx->lv_chain,
+	xfs_trans_committed_bulk(ctx->cil->xc_log->l_ailp, &ctx->lv_chain,
 					ctx->start_lsn, abort);
 
 	xfs_extent_busy_sort(&ctx->busy_extents);
@@ -658,7 +803,7 @@ xlog_cil_committed(
 	list_del(&ctx->committing);
 	spin_unlock(&ctx->cil->xc_push_lock);
 
-	xlog_cil_free_logvec(ctx->lv_chain);
+	xlog_cil_free_logvec(&ctx->lv_chain);
 
 	if (!list_empty(&ctx->busy_extents))
 		xlog_discard_busy_extents(mp, ctx);
@@ -817,7 +962,6 @@ restart:
 static int
 xlog_cil_write_chain(
 	struct xfs_cil_ctx	*ctx,
-	struct xfs_log_vec	*chain,
 	uint32_t		chain_len)
 {
 	struct xlog		*log = ctx->cil->xc_log;
@@ -826,7 +970,7 @@ xlog_cil_write_chain(
 	error = xlog_cil_order_write(ctx->cil, ctx->sequence, _START_RECORD);
 	if (error)
 		return error;
-	return xlog_write(log, ctx, chain, ctx->ticket, chain_len);
+	return xlog_write(log, ctx, &ctx->lv_chain, ctx->ticket, chain_len);
 }
 
 /*
@@ -855,6 +999,8 @@ xlog_cil_write_commit_record(
 		.lv_iovecp = &reg,
 	};
 	int			error;
+	LIST_HEAD(lv_chain);
+	list_add(&vec.lv_list, &lv_chain);
 
 	if (xlog_is_shutdown(log))
 		return -EIO;
@@ -865,7 +1011,7 @@ xlog_cil_write_commit_record(
 
 	/* account for space used by record data */
 	ctx->ticket->t_curr_res -= reg.i_len;
-	error = xlog_write(log, ctx, &vec, ctx->ticket, reg.i_len);
+	error = xlog_write(log, ctx, &lv_chain, ctx->ticket, reg.i_len);
 	if (error)
 		xlog_force_shutdown(log, SHUTDOWN_LOG_IO_ERROR);
 	return error;
@@ -931,12 +1077,31 @@ xlog_cil_build_trans_hdr(
 	lvhdr->lv_niovecs = 2;
 	lvhdr->lv_iovecp = &hdr->lhdr[0];
 	lvhdr->lv_bytes = hdr->lhdr[0].i_len + hdr->lhdr[1].i_len;
-	lvhdr->lv_next = ctx->lv_chain;
 
 	tic->t_curr_res -= lvhdr->lv_bytes;
 }
 
 /*
+ * CIL item reordering compare function. We want to order in ascending ID order,
+ * but we want to leave items with the same ID in the order they were added to
+ * the list. This is important for operations like reflink where we log 4 order
+ * dependent intents in a single transaction when we overwrite an existing
+ * shared extent with a new shared extent. i.e. BUI(unmap), CUI(drop),
+ * CUI (inc), BUI(remap)...
+ */
+static int
+xlog_cil_order_cmp(
+	void			*priv,
+	const struct list_head	*a,
+	const struct list_head	*b)
+{
+	struct xfs_log_vec	*l1 = container_of(a, struct xfs_log_vec, lv_list);
+	struct xfs_log_vec	*l2 = container_of(b, struct xfs_log_vec, lv_list);
+
+	return l1->lv_order_id > l2->lv_order_id;
+}
+
+/*
  * 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.
@@ -947,18 +1112,16 @@ xlog_cil_build_trans_hdr(
  */
 static void
 xlog_cil_build_lv_chain(
-	struct xfs_cil		*cil,
 	struct xfs_cil_ctx	*ctx,
 	struct list_head	*whiteouts,
 	uint32_t		*num_iovecs,
 	uint32_t		*num_bytes)
 {
-	struct xfs_log_vec	*lv = NULL;
-
-	while (!list_empty(&cil->xc_cil)) {
+	while (!list_empty(&ctx->log_items)) {
 		struct xfs_log_item	*item;
+		struct xfs_log_vec	*lv;
 
-		item = list_first_entry(&cil->xc_cil,
+		item = list_first_entry(&ctx->log_items,
 					struct xfs_log_item, li_cil);
 
 		if (test_bit(XFS_LI_WHITEOUT, &item->li_flags)) {
@@ -967,18 +1130,18 @@ xlog_cil_build_lv_chain(
 			continue;
 		}
 
-		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;
+		lv->lv_order_id = item->li_order_id;
 
 		/* we don't write ordered log vectors */
 		if (lv->lv_buf_len != XFS_LOG_VEC_ORDERED)
 			*num_bytes += lv->lv_bytes;
+		*num_iovecs += lv->lv_niovecs;
+		list_add_tail(&lv->lv_list, &ctx->lv_chain);
+
+		list_del_init(&item->li_cil);
+		item->li_order_id = 0;
+		item->li_lv = NULL;
 	}
 }
 
@@ -1022,10 +1185,11 @@ xlog_cil_push_work(
 	int			num_bytes = 0;
 	int			error = 0;
 	struct xlog_cil_trans_hdr thdr;
-	struct xfs_log_vec	lvhdr = { NULL };
+	struct xfs_log_vec	lvhdr = {};
 	xfs_csn_t		push_seq;
 	bool			push_commit_stable;
 	LIST_HEAD		(whiteouts);
+	struct xlog_ticket	*ticket;
 
 	new_ctx = xlog_cil_ctx_alloc();
 	new_ctx->ticket = xlog_cil_ticket_alloc(log);
@@ -1049,12 +1213,14 @@ xlog_cil_push_work(
 	if (waitqueue_active(&cil->xc_push_wait))
 		wake_up_all(&cil->xc_push_wait);
 
+	xlog_cil_push_pcp_aggregate(cil, ctx);
+
 	/*
 	 * 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)) {
+	if (test_bit(XLOG_CIL_EMPTY, &cil->xc_flags)) {
 		cil->xc_push_seq = 0;
 		spin_unlock(&cil->xc_push_lock);
 		goto out_skip;
@@ -1094,7 +1260,7 @@ xlog_cil_push_work(
 	list_add(&ctx->committing, &cil->xc_committing);
 	spin_unlock(&cil->xc_push_lock);
 
-	xlog_cil_build_lv_chain(cil, ctx, &whiteouts, &num_iovecs, &num_bytes);
+	xlog_cil_build_lv_chain(ctx, &whiteouts, &num_iovecs, &num_bytes);
 
 	/*
 	 * Switch the contexts so we can drop the context lock and move out
@@ -1127,14 +1293,30 @@ xlog_cil_push_work(
 	up_write(&cil->xc_ctx_lock);
 
 	/*
+	 * Sort the log vector chain before we add the transaction headers.
+	 * This ensures we always have the transaction headers at the start
+	 * of the chain.
+	 */
+	list_sort(NULL, &ctx->lv_chain, xlog_cil_order_cmp);
+
+	/*
 	 * 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().
+	 * Add the lvhdr to the head of the lv chain we pass to xlog_write() so
+	 * it gets written into the iclog first.
 	 */
 	xlog_cil_build_trans_hdr(ctx, &thdr, &lvhdr, num_iovecs);
 	num_bytes += lvhdr.lv_bytes;
+	list_add(&lvhdr.lv_list, &ctx->lv_chain);
 
-	error = xlog_cil_write_chain(ctx, &lvhdr, num_bytes);
+	/*
+	 * Take the lvhdr back off the lv_chain immediately after calling
+	 * xlog_cil_write_chain() as it should not be passed to log IO
+	 * completion.
+	 */
+	error = xlog_cil_write_chain(ctx, num_bytes);
+	list_del(&lvhdr.lv_list);
 	if (error)
 		goto out_abort_free_ticket;
 
@@ -1142,7 +1324,14 @@ xlog_cil_push_work(
 	if (error)
 		goto out_abort_free_ticket;
 
-	xfs_log_ticket_ungrant(log, ctx->ticket);
+	/*
+	 * Grab the ticket from the ctx so we can ungrant it after releasing the
+	 * commit_iclog. The ctx may be freed by the time we return from
+	 * releasing the commit_iclog (i.e. checkpoint has been completed and
+	 * callback run) so we can't reference the ctx after the call to
+	 * xlog_state_release_iclog().
+	 */
+	ticket = ctx->ticket;
 
 	/*
 	 * If the checkpoint spans multiple iclogs, wait for all previous iclogs
@@ -1192,12 +1381,14 @@ xlog_cil_push_work(
 	if (push_commit_stable &&
 	    ctx->commit_iclog->ic_state == XLOG_STATE_ACTIVE)
 		xlog_state_switch_iclogs(log, ctx->commit_iclog, 0);
-	xlog_state_release_iclog(log, ctx->commit_iclog);
+	ticket = ctx->ticket;
+	xlog_state_release_iclog(log, ctx->commit_iclog, ticket);
 
 	/* Not safe to reference ctx now! */
 
 	spin_unlock(&log->l_icloglock);
 	xlog_cil_cleanup_whiteouts(&whiteouts);
+	xfs_log_ticket_ungrant(log, ticket);
 	return;
 
 out_skip:
@@ -1207,17 +1398,19 @@ out_skip:
 	return;
 
 out_abort_free_ticket:
-	xfs_log_ticket_ungrant(log, ctx->ticket);
 	ASSERT(xlog_is_shutdown(log));
 	xlog_cil_cleanup_whiteouts(&whiteouts);
 	if (!ctx->commit_iclog) {
+		xfs_log_ticket_ungrant(log, ctx->ticket);
 		xlog_cil_committed(ctx);
 		return;
 	}
 	spin_lock(&log->l_icloglock);
-	xlog_state_release_iclog(log, ctx->commit_iclog);
+	ticket = ctx->ticket;
+	xlog_state_release_iclog(log, ctx->commit_iclog, ticket);
 	/* Not safe to reference ctx now! */
 	spin_unlock(&log->l_icloglock);
+	xfs_log_ticket_ungrant(log, ticket);
 }
 
 /*
@@ -1232,18 +1425,27 @@ xlog_cil_push_background(
 	struct xlog	*log) __releases(cil->xc_ctx_lock)
 {
 	struct xfs_cil	*cil = log->l_cilp;
+	int		space_used = atomic_read(&cil->xc_ctx->space_used);
 
 	/*
 	 * 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
+	 * context lock so whatever we added to the CIL will still be there.
 	 */
-	ASSERT(!list_empty(&cil->xc_cil));
+	ASSERT(!test_bit(XLOG_CIL_EMPTY, &cil->xc_flags));
 
 	/*
-	 * Don't do a background push if we haven't used up all the
-	 * space available yet.
+	 * We are done if:
+	 * - we haven't used up all the space available yet; or
+	 * - we've already queued up a push; and
+	 * - we're not over the hard limit; and
+	 * - nothing has been over the hard limit.
+	 *
+	 * If so, we don't need to take the push lock as there's nothing to do.
 	 */
-	if (cil->xc_ctx->space_used < XLOG_CIL_SPACE_LIMIT(log)) {
+	if (space_used < XLOG_CIL_SPACE_LIMIT(log) ||
+	    (cil->xc_push_seq == cil->xc_current_sequence &&
+	     space_used < XLOG_CIL_BLOCKING_SPACE_LIMIT(log) &&
+	     !waitqueue_active(&cil->xc_push_wait))) {
 		up_read(&cil->xc_ctx_lock);
 		return;
 	}
@@ -1270,12 +1472,11 @@ xlog_cil_push_background(
 	 * dipping back down under the hard limit.
 	 *
 	 * The ctx->xc_push_lock provides the serialisation necessary for safely
-	 * using the lockless waitqueue_active() check in this context.
+	 * calling xlog_cil_over_hard_limit() in this context.
 	 */
-	if (cil->xc_ctx->space_used >= XLOG_CIL_BLOCKING_SPACE_LIMIT(log) ||
-	    waitqueue_active(&cil->xc_push_wait)) {
+	if (xlog_cil_over_hard_limit(log, space_used)) {
 		trace_xfs_log_cil_wait(log, cil->xc_ctx->ticket);
-		ASSERT(cil->xc_ctx->space_used < log->l_logsize);
+		ASSERT(space_used < log->l_logsize);
 		xlog_wait(&cil->xc_push_wait, &cil->xc_push_lock);
 		return;
 	}
@@ -1334,7 +1535,8 @@ xlog_cil_push_now(
 	 * If the CIL is empty or we've already pushed the sequence then
 	 * there's no more work that we need to do.
 	 */
-	if (list_empty(&cil->xc_cil) || push_seq <= cil->xc_push_seq) {
+	if (test_bit(XLOG_CIL_EMPTY, &cil->xc_flags) ||
+	    push_seq <= cil->xc_push_seq) {
 		spin_unlock(&cil->xc_push_lock);
 		return;
 	}
@@ -1352,7 +1554,7 @@ xlog_cil_empty(
 	bool		empty = false;
 
 	spin_lock(&cil->xc_push_lock);
-	if (list_empty(&cil->xc_cil))
+	if (test_bit(XLOG_CIL_EMPTY, &cil->xc_flags))
 		empty = true;
 	spin_unlock(&cil->xc_push_lock);
 	return empty;
@@ -1483,7 +1685,7 @@ xlog_cil_flush(
 	 * If the CIL is empty, make sure that any previous checkpoint that may
 	 * still be in an active iclog is pushed to stable storage.
 	 */
-	if (list_empty(&log->l_cilp->xc_cil))
+	if (test_bit(XLOG_CIL_EMPTY, &log->l_cilp->xc_flags))
 		xfs_log_force(log->l_mp, 0);
 }
 
@@ -1568,7 +1770,7 @@ restart:
 	 * we would have found the context on the committing list.
 	 */
 	if (sequence == cil->xc_current_sequence &&
-	    !list_empty(&cil->xc_cil)) {
+	    !test_bit(XLOG_CIL_EMPTY, &cil->xc_flags)) {
 		spin_unlock(&cil->xc_push_lock);
 		goto restart;
 	}
@@ -1589,14 +1791,48 @@ out_shutdown:
 }
 
 /*
+ * Move dead percpu state to the relevant CIL context structures.
+ *
+ * We have to lock the CIL context here to ensure that nothing is modifying
+ * the percpu state, either addition or removal. Both of these are done under
+ * the CIL context lock, so grabbing that exclusively here will ensure we can
+ * safely drain the cilpcp for the CPU that is dying.
+ */
+void
+xlog_cil_pcp_dead(
+	struct xlog		*log,
+	unsigned int		cpu)
+{
+	struct xfs_cil		*cil = log->l_cilp;
+	struct xlog_cil_pcp	*cilpcp = per_cpu_ptr(cil->xc_pcp, cpu);
+	struct xfs_cil_ctx	*ctx;
+
+	down_write(&cil->xc_ctx_lock);
+	ctx = cil->xc_ctx;
+	if (ctx->ticket)
+		ctx->ticket->t_curr_res += cilpcp->space_reserved;
+	cilpcp->space_reserved = 0;
+
+	if (!list_empty(&cilpcp->log_items))
+		list_splice_init(&cilpcp->log_items, &ctx->log_items);
+	if (!list_empty(&cilpcp->busy_extents))
+		list_splice_init(&cilpcp->busy_extents, &ctx->busy_extents);
+	atomic_add(cilpcp->space_used, &ctx->space_used);
+	cilpcp->space_used = 0;
+	up_write(&cil->xc_ctx_lock);
+}
+
+/*
  * Perform initial CIL structure initialisation.
  */
 int
 xlog_cil_init(
-	struct xlog	*log)
+	struct xlog		*log)
 {
-	struct xfs_cil	*cil;
-	struct xfs_cil_ctx *ctx;
+	struct xfs_cil		*cil;
+	struct xfs_cil_ctx	*ctx;
+	struct xlog_cil_pcp	*cilpcp;
+	int			cpu;
 
 	cil = kmem_zalloc(sizeof(*cil), KM_MAYFAIL);
 	if (!cil)
@@ -1611,22 +1847,31 @@ xlog_cil_init(
 	if (!cil->xc_push_wq)
 		goto out_destroy_cil;
 
-	INIT_LIST_HEAD(&cil->xc_cil);
+	cil->xc_log = log;
+	cil->xc_pcp = alloc_percpu(struct xlog_cil_pcp);
+	if (!cil->xc_pcp)
+		goto out_destroy_wq;
+
+	for_each_possible_cpu(cpu) {
+		cilpcp = per_cpu_ptr(cil->xc_pcp, cpu);
+		INIT_LIST_HEAD(&cilpcp->busy_extents);
+		INIT_LIST_HEAD(&cilpcp->log_items);
+	}
+
 	INIT_LIST_HEAD(&cil->xc_committing);
-	spin_lock_init(&cil->xc_cil_lock);
 	spin_lock_init(&cil->xc_push_lock);
 	init_waitqueue_head(&cil->xc_push_wait);
 	init_rwsem(&cil->xc_ctx_lock);
 	init_waitqueue_head(&cil->xc_start_wait);
 	init_waitqueue_head(&cil->xc_commit_wait);
-	cil->xc_log = log;
 	log->l_cilp = cil;
 
 	ctx = xlog_cil_ctx_alloc();
 	xlog_cil_ctx_switch(cil, ctx);
-
 	return 0;
 
+out_destroy_wq:
+	destroy_workqueue(cil->xc_push_wq);
 out_destroy_cil:
 	kmem_free(cil);
 	return -ENOMEM;
@@ -1636,14 +1881,17 @@ 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);
+	struct xfs_cil	*cil = log->l_cilp;
+
+	if (cil->xc_ctx) {
+		if (cil->xc_ctx->ticket)
+			xfs_log_ticket_put(cil->xc_ctx->ticket);
+		kmem_free(cil->xc_ctx);
 	}
 
-	ASSERT(list_empty(&log->l_cilp->xc_cil));
-	destroy_workqueue(log->l_cilp->xc_push_wq);
-	kmem_free(log->l_cilp);
+	ASSERT(test_bit(XLOG_CIL_EMPTY, &cil->xc_flags));
+	free_percpu(cil->xc_pcp);
+	destroy_workqueue(cil->xc_push_wq);
+	kmem_free(cil);
 }