1 files changed, 725 insertions, 0 deletions

diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
new file mode 100644
index 000000000000..bb17cc044bf3
--- /dev/null
+++ b/fs/xfs/xfs_log_cil.c
@@ -0,0 +1,725 @@
+/*
+ * 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_types.h"
+#include "xfs_bit.h"
+#include "xfs_log.h"
+#include "xfs_inum.h"
+#include "xfs_trans.h"
+#include "xfs_trans_priv.h"
+#include "xfs_log_priv.h"
+#include "xfs_sb.h"
+#include "xfs_ag.h"
+#include "xfs_dir2.h"
+#include "xfs_dmapi.h"
+#include "xfs_mount.h"
+#include "xfs_error.h"
+#include "xfs_alloc.h"
+
+/*
+ * Perform initial CIL structure initialisation. If the CIL is not
+ * enabled in this filesystem, ensure the log->l_cilp is null so
+ * we can check this conditional to determine if we are doing delayed
+ * logging or not.
+ */
+int
+xlog_cil_init(
+        struct log      *log)
+{
+        struct xfs_cil  *cil;
+        struct xfs_cil_ctx *ctx;
+
+        log->l_cilp = NULL;
+        if (!(log->l_mp->m_flags & XFS_MOUNT_DELAYLOG))
+                return 0;
+
+        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_LIST_HEAD(&cil->xc_cil);
+        INIT_LIST_HEAD(&cil->xc_committing);
+        spin_lock_init(&cil->xc_cil_lock);
+        init_rwsem(&cil->xc_ctx_lock);
+        sv_init(&cil->xc_commit_wait, SV_DEFAULT, "cilwait");
+
+        INIT_LIST_HEAD(&ctx->committing);
+        INIT_LIST_HEAD(&ctx->busy_extents);
+        ctx->sequence = 1;
+        ctx->cil = cil;
+        cil->xc_ctx = ctx;
+
+        cil->xc_log = log;
+        log->l_cilp = cil;
+        return 0;
+}
+
+void
+xlog_cil_destroy(
+        struct log      *log)
+{
+        if (!log->l_cilp)
+                return;
+
+        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);
+}
+
+/*
+ * 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 log      *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 log      *log)
+{
+        if (!log->l_cilp)
+                return;
+
+        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);
+}
+
+/*
+ * Insert the log item 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 addded to the checkpoint ticket from
+ * the current transaction ticket so that the accounting works out correctly.
+ *
+ * If this is the first time the item is being placed into the CIL in this
+ * context, pin it so it can't be written to disk until the CIL is flushed to
+ * the iclog and the iclog written to disk.
+ */
+static void
+xlog_cil_insert(
+        struct log              *log,
+        struct xlog_ticket      *ticket,
+        struct xfs_log_item     *item,
+        struct xfs_log_vec      *lv)
+{
+        struct xfs_cil          *cil = log->l_cilp;
+        struct xfs_log_vec      *old = lv->lv_item->li_lv;
+        struct xfs_cil_ctx      *ctx = cil->xc_ctx;
+        int                     len;
+        int                     diff_iovecs;
+        int                     iclog_space;
+
+        if (old) {
+                /* existing lv on log item, space used is a delta */
+                ASSERT(!list_empty(&item->li_cil));
+                ASSERT(old->lv_buf && old->lv_buf_len && old->lv_niovecs);
+
+                len = lv->lv_buf_len - old->lv_buf_len;
+                diff_iovecs = lv->lv_niovecs - old->lv_niovecs;
+                kmem_free(old->lv_buf);
+                kmem_free(old);
+        } else {
+                /* new lv, must pin the log item */
+                ASSERT(!lv->lv_item->li_lv);
+                ASSERT(list_empty(&item->li_cil));
+
+                len = lv->lv_buf_len;
+                diff_iovecs = lv->lv_niovecs;
+                IOP_PIN(lv->lv_item);
+
+        }
+        len += diff_iovecs * sizeof(xlog_op_header_t);
+
+        /* attach new log vector to log item */
+        lv->lv_item->li_lv = lv;
+
+        spin_lock(&cil->xc_cil_lock);
+        list_move_tail(&item->li_cil, &cil->xc_cil);
+        ctx->nvecs += diff_iovecs;
+
+        /*
+         * 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 (!item->li_seq)
+                item->li_seq = ctx->sequence;
+
+        /*
+         * 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) {
+                /* first commit in checkpoint, steal the header reservation */
+                ASSERT(ticket->t_curr_res >= ctx->ticket->t_unit_res + len);
+                ctx->ticket->t_curr_res = ctx->ticket->t_unit_res;
+                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;
+                ticket->t_curr_res -= hdrs;
+                ASSERT(ticket->t_curr_res >= len);
+        }
+        ticket->t_curr_res -= len;
+        ctx->space_used += len;
+
+        spin_unlock(&cil->xc_cil_lock);
+}
+
+/*
+ * 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_format_items(
+        struct log              *log,
+        struct xfs_log_vec      *log_vector,
+        struct xlog_ticket      *ticket,
+        xfs_lsn_t               *start_lsn)
+{
+        struct xfs_log_vec *lv;
+
+        if (start_lsn)
+                *start_lsn = log->l_cilp->xc_ctx->sequence;
+
+        ASSERT(log_vector);
+        for (lv = log_vector; lv; lv = lv->lv_next) {
+                void    *ptr;
+                int     index;
+                int     len = 0;
+
+                /* build the vector array and calculate it's length */
+                IOP_FORMAT(lv->lv_item, lv->lv_iovecp);
+                for (index = 0; index < lv->lv_niovecs; index++)
+                        len += lv->lv_iovecp[index].i_len;
+
+                lv->lv_buf_len = len;
+                lv->lv_buf = kmem_zalloc(lv->lv_buf_len, KM_SLEEP|KM_NOFS);
+                ptr = lv->lv_buf;
+
+                for (index = 0; index < lv->lv_niovecs; index++) {
+                        struct xfs_log_iovec *vec = &lv->lv_iovecp[index];
+
+                        memcpy(ptr, vec->i_addr, vec->i_len);
+                        vec->i_addr = ptr;
+                        ptr += vec->i_len;
+                }
+                ASSERT(ptr == lv->lv_buf + lv->lv_buf_len);
+
+                xlog_cil_insert(log, ticket, lv->lv_item, lv);
+        }
+}
+
+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_buf);
+                kmem_free(lv);
+                lv = next;
+        }
+}
+
+/*
+ * 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.
+ *
+ * For more specific information about the order of operations in
+ * xfs_log_commit_cil() please refer to the comments in
+ * xfs_trans_commit_iclog().
+ *
+ * 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.
+ */
+int
+xfs_log_commit_cil(
+        struct xfs_mount        *mp,
+        struct xfs_trans        *tp,
+        struct xfs_log_vec      *log_vector,
+        xfs_lsn_t               *commit_lsn,
+        int                     flags)
+{
+        struct log              *log = mp->m_log;
+        int                     log_flags = 0;
+        int                     push = 0;
+
+        if (flags & XFS_TRANS_RELEASE_LOG_RES)
+                log_flags = XFS_LOG_REL_PERM_RESERV;
+
+        if (XLOG_FORCED_SHUTDOWN(log)) {
+                xlog_cil_free_logvec(log_vector);
+                return XFS_ERROR(EIO);
+        }
+
+        /* lock out background commit */
+        down_read(&log->l_cilp->xc_ctx_lock);
+        xlog_cil_format_items(log, log_vector, tp->t_ticket, commit_lsn);
+
+        /* check we didn't blow the reservation */
+        if (tp->t_ticket->t_curr_res < 0)
+                xlog_print_tic_res(log->l_mp, tp->t_ticket);
+
+        /* attach the transaction to the CIL if it has any busy extents */
+        if (!list_empty(&tp->t_busy)) {
+                spin_lock(&log->l_cilp->xc_cil_lock);
+                list_splice_init(&tp->t_busy,
+                                        &log->l_cilp->xc_ctx->busy_extents);
+                spin_unlock(&log->l_cilp->xc_cil_lock);
+        }
+
+        tp->t_commit_lsn = *commit_lsn;
+        xfs_log_done(mp, tp->t_ticket, NULL, log_flags);
+        xfs_trans_unreserve_and_mod_sb(tp);
+
+        /* check for background commit before unlock */
+        if (log->l_cilp->xc_ctx->space_used > XLOG_CIL_SPACE_LIMIT(log))
+                push = 1;
+        up_read(&log->l_cilp->xc_ctx_lock);
+
+        /*
+         * 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 in most cases.
+         */
+        if (push)
+                xlog_cil_push(log, 0);
+        return 0;
+}
+
+/*
+ * 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_log_vec      *lv;
+        int                     abortflag = abort ? XFS_LI_ABORTED : 0;
+        struct xfs_busy_extent  *busyp, *n;
+
+        /* unpin all the log items */
+        for (lv = ctx->lv_chain; lv; lv = lv->lv_next ) {
+                xfs_trans_item_committed(lv->lv_item, ctx->start_lsn,
+                                                        abortflag);
+        }
+
+        list_for_each_entry_safe(busyp, n, &ctx->busy_extents, list)
+                xfs_alloc_busy_clear(ctx->cil->xc_log->l_mp, busyp);
+
+        spin_lock(&ctx->cil->xc_cil_lock);
+        list_del(&ctx->committing);
+        spin_unlock(&ctx->cil->xc_cil_lock);
+
+        xlog_cil_free_logvec(ctx->lv_chain);
+        kmem_free(ctx);
+}
+
+/*
+ * Push the Committed Item List to the log. If the push_now flag is not set,
+ * then it is a background flush and so we can chose to ignore it.
+ */
+int
+xlog_cil_push(
+        struct log              *log,
+        int                     push_now)
+{
+        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_lv;
+        int                     num_iovecs;
+        int                     len;
+        int                     error = 0;
+        struct xfs_trans_header thdr;
+        struct xfs_log_iovec    lhdr;
+        struct xfs_log_vec      lvhdr = { NULL };
+        xfs_lsn_t               commit_lsn;
+
+        if (!cil)
+                return 0;
+
+        new_ctx = kmem_zalloc(sizeof(*new_ctx), KM_SLEEP|KM_NOFS);
+        new_ctx->ticket = xlog_cil_ticket_alloc(log);
+
+        /* lock out transaction commit, but don't block on background push */
+        if (!down_write_trylock(&cil->xc_ctx_lock)) {
+                if (!push_now)
+                        goto out_free_ticket;
+                down_write(&cil->xc_ctx_lock);
+        }
+        ctx = cil->xc_ctx;
+
+        /* check if we've anything to push */
+        if (list_empty(&cil->xc_cil))
+                goto out_skip;
+
+        /* check for spurious background flush */
+        if (!push_now && cil->xc_ctx->space_used < XLOG_CIL_SPACE_LIMIT(log))
+                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_lv = 0;
+        num_iovecs = 0;
+        len = 0;
+        while (!list_empty(&cil->xc_cil)) {
+                struct xfs_log_item     *item;
+                int                     i;
+
+                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_lv++;
+                num_iovecs += lv->lv_niovecs;
+                for (i = 0; i < lv->lv_niovecs; i++)
+                        len += lv->lv_iovecp[i].i_len;
+        }
+
+        /*
+         * 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.
+         */
+        spin_lock(&cil->xc_cil_lock);
+        list_add(&ctx->committing, &cil->xc_committing);
+        spin_unlock(&cil->xc_cil_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 = (xfs_caddr_t)&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;
+
+        /*
+         * 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_cil_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.
+                         */
+                        sv_wait(&cil->xc_commit_wait, 0, &cil->xc_cil_lock, 0);
+                        goto restart;
+                }
+        }
+        spin_unlock(&cil->xc_cil_lock);
+
+        commit_lsn = xfs_log_done(log->l_mp, tic, &commit_iclog, 0);
+        if (error || 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_cil_lock);
+        ctx->commit_lsn = commit_lsn;
+        sv_broadcast(&cil->xc_commit_wait);
+        spin_unlock(&cil->xc_cil_lock);
+
+        /* release the hounds! */
+        return xfs_log_release_iclog(log->l_mp, commit_iclog);
+
+out_skip:
+        up_write(&cil->xc_ctx_lock);
+out_free_ticket:
+        xfs_log_ticket_put(new_ctx->ticket);
+        kmem_free(new_ctx);
+        return 0;
+
+out_abort:
+        xlog_cil_committed(ctx, XFS_LI_ABORTED);
+        return XFS_ERROR(EIO);
+}
+
+/*
+ * 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.
+ *
+ * XXX: Initially, just push the CIL unconditionally and return whatever
+ * commit lsn is there. It'll be empty, so this is broken for now.
+ */
+xfs_lsn_t
+xlog_cil_push_lsn(
+        struct log      *log,
+        xfs_lsn_t       push_seq)
+{
+        struct xfs_cil          *cil = log->l_cilp;
+        struct xfs_cil_ctx      *ctx;
+        xfs_lsn_t               commit_lsn = NULLCOMMITLSN;
+
+restart:
+        down_write(&cil->xc_ctx_lock);
+        ASSERT(push_seq <= cil->xc_ctx->sequence);
+
+        /* check to see if we need to force out the current context */
+        if (push_seq == cil->xc_ctx->sequence) {
+                up_write(&cil->xc_ctx_lock);
+                xlog_cil_push(log, 1);
+                goto restart;
+        }
+
+        /*
+         * See if we can find a previous sequence still committing.
+         * We can drop the flush lock as soon as we have the cil lock
+         * because we are now only comparing contexts protected by
+         * the cil lock.
+         *
+         * 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_cil_lock);
+        up_write(&cil->xc_ctx_lock);
+        list_for_each_entry(ctx, &cil->xc_committing, committing) {
+                if (ctx->sequence > push_seq)
+                        continue;
+                if (!ctx->commit_lsn) {
+                        /*
+                         * It is still being pushed! Wait for the push to
+                         * complete, then start again from the beginning.
+                         */
+                        sv_wait(&cil->xc_commit_wait, 0, &cil->xc_cil_lock, 0);
+                        goto restart;
+                }
+                if (ctx->sequence != push_seq)
+                        continue;
+                /* found it! */
+                commit_lsn = ctx->commit_lsn;
+        }
+        spin_unlock(&cil->xc_cil_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 (!(lip->li_mountp->m_flags & XFS_MOUNT_DELAYLOG))
+                return false;
+        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;
+}