[PATCH 1/4] NFSv4.1/flexfiles: Add refcounting to struct nfs4_ff_layout_mirror

[PATCH 1/4] NFSv4.1/flexfiles: Add refcounting to struct nfs4_ff_layout_mirror

[Trond Myklebust]

We do want to share mirrors between layout segments, so add a refcount
to enable that.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
---
 fs/nfs/flexfilelayout/flexfilelayout.c | 36 +++++++++++++++++++++++++---------
 fs/nfs/flexfilelayout/flexfilelayout.h |  1 +
 2 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
index cc2c5f7f2bc1..62de0b8038c8 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -135,6 +135,31 @@ decode_name(struct xdr_stream *xdr, u32 *id)
 	return 0;
 }
 
+static struct nfs4_ff_layout_mirror *ff_layout_alloc_mirror(gfp_t gfp_flags)
+{
+	struct nfs4_ff_layout_mirror *mirror;
+
+	mirror = kzalloc(sizeof(*mirror), gfp_flags);
+	if (mirror != NULL) {
+		spin_lock_init(&mirror->lock);
+		atomic_set(&mirror->ref, 1);
+	}
+	return mirror;
+}
+
+static void ff_layout_free_mirror(struct nfs4_ff_layout_mirror *mirror)
+{
+	kfree(mirror->fh_versions);
+	nfs4_ff_layout_put_deviceid(mirror->mirror_ds);
+	kfree(mirror);
+}
+
+static void ff_layout_put_mirror(struct nfs4_ff_layout_mirror *mirror)
+{
+	if (mirror != NULL && atomic_dec_and_test(&mirror->ref))
+		ff_layout_free_mirror(mirror);
+}
+
 static void ff_layout_free_mirror_array(struct nfs4_ff_layout_segment *fls)
 {
 	int i;
@@ -144,11 +169,7 @@ static void ff_layout_free_mirror_array(struct nfs4_ff_layout_segment *fls)
 			/* normally mirror_ds is freed in
 			 * .free_deviceid_node but we still do it here
 			 * for .alloc_lseg error path */
-			if (fls->mirror_array[i]) {
-				kfree(fls->mirror_array[i]->fh_versions);
-				nfs4_ff_layout_put_deviceid(fls->mirror_array[i]->mirror_ds);
-				kfree(fls->mirror_array[i]);
-			}
+			ff_layout_put_mirror(fls->mirror_array[i]);
 		}
 		kfree(fls->mirror_array);
 		fls->mirror_array = NULL;
@@ -262,15 +283,12 @@ ff_layout_alloc_lseg(struct pnfs_layout_hdr *lh,
 		if (ds_count != 1)
 			goto out_err_free;
 
-		fls->mirror_array[i] =
-			kzalloc(sizeof(struct nfs4_ff_layout_mirror),
-				gfp_flags);
+		fls->mirror_array[i] = ff_layout_alloc_mirror(gfp_flags);
 		if (fls->mirror_array[i] == NULL) {
 			rc = -ENOMEM;
 			goto out_err_free;
 		}
 
-		spin_lock_init(&fls->mirror_array[i]->lock);
 		fls->mirror_array[i]->ds_count = ds_count;
 		fls->mirror_array[i]->lseg = &fls->generic_hdr;
 
diff --git a/fs/nfs/flexfilelayout/flexfilelayout.h b/fs/nfs/flexfilelayout/flexfilelayout.h
index f92f9a0a856b..26b8258e256f 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.h
+++ b/fs/nfs/flexfilelayout/flexfilelayout.h
@@ -77,6 +77,7 @@ struct nfs4_ff_layout_mirror {
 	u32				uid;
 	u32				gid;
 	struct rpc_cred			*cred;
+	atomic_t			ref;
 	spinlock_t			lock;
 	struct nfs4_ff_layoutstat	read_stat;
 	struct nfs4_ff_layoutstat	write_stat;
-- 
2.4.3

[PATCH 2/4] NFSv4.1/flexfiles: Remove mirror backpointer to lseg.

[Trond Myklebust]

When we start sharing mirrors between several lsegs, we won't be able to
keep it.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
---
 fs/nfs/flexfilelayout/flexfilelayout.c | 25 ++++++++++++-------------
 fs/nfs/flexfilelayout/flexfilelayout.h |  1 -
 2 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
index 62de0b8038c8..f3efff640989 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -290,7 +290,6 @@ ff_layout_alloc_lseg(struct pnfs_layout_hdr *lh,
 		}
 
 		fls->mirror_array[i]->ds_count = ds_count;
-		fls->mirror_array[i]->lseg = &fls->generic_hdr;
 
 		/* deviceid */
 		rc = decode_deviceid(&stream, &devid);
@@ -513,7 +512,8 @@ nfs4_ff_layout_stat_io_update_completed(struct nfs4_ff_layoutstat *layoutstat,
 }
 
 static void
-nfs4_ff_layout_stat_io_start_read(struct nfs4_ff_layout_mirror *mirror,
+nfs4_ff_layout_stat_io_start_read(struct inode *inode,
+		struct nfs4_ff_layout_mirror *mirror,
 		__u64 requested, ktime_t now)
 {
 	bool report;
@@ -524,8 +524,7 @@ nfs4_ff_layout_stat_io_start_read(struct nfs4_ff_layout_mirror *mirror,
 	spin_unlock(&mirror->lock);
 
 	if (report)
-		pnfs_report_layoutstat(mirror->lseg->pls_layout->plh_inode,
-				GFP_KERNEL);
+		pnfs_report_layoutstat(inode, GFP_KERNEL);
 }
 
 static void
@@ -542,7 +541,8 @@ nfs4_ff_layout_stat_io_end_read(struct rpc_task *task,
 }
 
 static void
-nfs4_ff_layout_stat_io_start_write(struct nfs4_ff_layout_mirror *mirror,
+nfs4_ff_layout_stat_io_start_write(struct inode *inode,
+		struct nfs4_ff_layout_mirror *mirror,
 		__u64 requested, ktime_t now)
 {
 	bool report;
@@ -553,8 +553,7 @@ nfs4_ff_layout_stat_io_start_write(struct nfs4_ff_layout_mirror *mirror,
 	spin_unlock(&mirror->lock);
 
 	if (report)
-		pnfs_report_layoutstat(mirror->lseg->pls_layout->plh_inode,
-				GFP_NOIO);
+		pnfs_report_layoutstat(inode, GFP_NOIO);
 }
 
 static void
@@ -1098,7 +1097,7 @@ ff_layout_reset_to_mds(struct pnfs_layout_segment *lseg, int idx)
 static int ff_layout_read_prepare_common(struct rpc_task *task,
 					 struct nfs_pgio_header *hdr)
 {
-	nfs4_ff_layout_stat_io_start_read(
+	nfs4_ff_layout_stat_io_start_read(hdr->inode,
 			FF_LAYOUT_COMP(hdr->lseg, hdr->pgio_mirror_idx),
 			hdr->args.count,
 			task->tk_start);
@@ -1285,7 +1284,7 @@ static int ff_layout_commit_done_cb(struct rpc_task *task,
 static int ff_layout_write_prepare_common(struct rpc_task *task,
 					  struct nfs_pgio_header *hdr)
 {
-	nfs4_ff_layout_stat_io_start_write(
+	nfs4_ff_layout_stat_io_start_write(hdr->inode,
 			FF_LAYOUT_COMP(hdr->lseg, hdr->pgio_mirror_idx),
 			hdr->args.count,
 			task->tk_start);
@@ -1367,7 +1366,7 @@ static void ff_layout_write_count_stats(struct rpc_task *task, void *data)
 static void ff_layout_commit_prepare_common(struct rpc_task *task,
 		struct nfs_commit_data *cdata)
 {
-	nfs4_ff_layout_stat_io_start_write(
+	nfs4_ff_layout_stat_io_start_write(cdata->inode,
 			FF_LAYOUT_COMP(cdata->lseg, cdata->ds_commit_index),
 			0, task->tk_start);
 }
@@ -1912,8 +1911,8 @@ ff_layout_mirror_prepare_stats(struct nfs42_layoutstat_args *args,
 		devinfo->layout_type = LAYOUT_FLEX_FILES;
 		devinfo->layoutstats_encode = ff_layout_encode_layoutstats;
 		devinfo->layout_private = mirror;
-		/* lseg refcount put in cleanup_layoutstats */
-		pnfs_get_lseg(pls);
+		/* mirror refcount put in cleanup_layoutstats */
+		atomic_inc(&mirror->ref);
 
 		++(*dev_count);
 	}
@@ -1965,7 +1964,7 @@ ff_layout_cleanup_layoutstats(struct nfs42_layoutstat_data *data)
 	for (i = 0; i < data->args.num_dev; i++) {
 		mirror = data->args.devinfo[i].layout_private;
 		data->args.devinfo[i].layout_private = NULL;
-		pnfs_put_lseg(mirror->lseg);
+		ff_layout_put_mirror(mirror);
 	}
 }
 
diff --git a/fs/nfs/flexfilelayout/flexfilelayout.h b/fs/nfs/flexfilelayout/flexfilelayout.h
index 26b8258e256f..fe9d3ff7cf85 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.h
+++ b/fs/nfs/flexfilelayout/flexfilelayout.h
@@ -67,7 +67,6 @@ struct nfs4_ff_layoutstat {
 };
 
 struct nfs4_ff_layout_mirror {
-	struct pnfs_layout_segment	*lseg; /* back pointer */
 	u32				ds_count;
 	u32				efficiency;
 	struct nfs4_ff_layout_ds	*mirror_ds;
-- 
2.4.3

[PATCH 3/4] NFSv4.1/flexfile: Ensure uniqueness of mirrors across layout segments

[Trond Myklebust]

Keep the full list of mirrors in the struct nfs4_ff_layout_mirror so that
they can be shared among the layout segments that use them.
Also ensure that we send out only one copy of the layoutstats per mirror.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
---
 fs/nfs/flexfilelayout/flexfilelayout.c | 116 ++++++++++++++++++++++++++-------
 fs/nfs/flexfilelayout/flexfilelayout.h |   3 +
 2 files changed, 95 insertions(+), 24 deletions(-)

diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
index f3efff640989..210352741177 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -34,6 +34,7 @@ ff_layout_alloc_layout_hdr(struct inode *inode, gfp_t gfp_flags)
 	ffl = kzalloc(sizeof(*ffl), gfp_flags);
 	if (ffl) {
 		INIT_LIST_HEAD(&ffl->error_list);
+		INIT_LIST_HEAD(&ffl->mirrors);
 		return &ffl->generic_hdr;
 	} else
 		return NULL;
@@ -135,6 +136,66 @@ decode_name(struct xdr_stream *xdr, u32 *id)
 	return 0;
 }
 
+static bool ff_mirror_match_fh(const struct nfs4_ff_layout_mirror *m1,
+		const struct nfs4_ff_layout_mirror *m2)
+{
+	int i, j;
+
+	if (m1->fh_versions_cnt != m2->fh_versions_cnt)
+		return false;
+	for (i = 0; i < m1->fh_versions_cnt; i++) {
+		bool found_fh = false;
+		for (j = 0; j < m2->fh_versions_cnt; i++) {
+			if (nfs_compare_fh(&m1->fh_versions[i],
+					&m2->fh_versions[j])) {
+				found_fh = true;
+				break;
+			}
+		}
+		if (!found_fh)
+			return false;
+	}
+	return true;
+}
+
+static struct nfs4_ff_layout_mirror *
+ff_layout_add_mirror(struct pnfs_layout_hdr *lo,
+		struct nfs4_ff_layout_mirror *mirror)
+{
+	struct nfs4_flexfile_layout *ff_layout = FF_LAYOUT_FROM_HDR(lo);
+	struct nfs4_ff_layout_mirror *pos;
+	struct inode *inode = lo->plh_inode;
+
+	spin_lock(&inode->i_lock);
+	list_for_each_entry(pos, &ff_layout->mirrors, mirrors) {
+		if (mirror->mirror_ds != pos->mirror_ds)
+			continue;
+		if (!ff_mirror_match_fh(mirror, pos))
+			continue;
+		if (atomic_inc_not_zero(&pos->ref)) {
+			spin_unlock(&inode->i_lock);
+			return pos;
+		}
+	}
+	list_add(&mirror->mirrors, &ff_layout->mirrors);
+	mirror->layout = lo;
+	spin_unlock(&inode->i_lock);
+	return mirror;
+}
+
+void
+ff_layout_remove_mirror(struct nfs4_ff_layout_mirror *mirror)
+{
+	struct inode *inode;
+	if (mirror->layout == NULL)
+		return;
+	inode = mirror->layout->plh_inode;
+	spin_lock(&inode->i_lock);
+	list_del(&mirror->mirrors);
+	spin_unlock(&inode->i_lock);
+	mirror->layout = NULL;
+}
+
 static struct nfs4_ff_layout_mirror *ff_layout_alloc_mirror(gfp_t gfp_flags)
 {
 	struct nfs4_ff_layout_mirror *mirror;
@@ -143,12 +204,14 @@ static struct nfs4_ff_layout_mirror *ff_layout_alloc_mirror(gfp_t gfp_flags)
 	if (mirror != NULL) {
 		spin_lock_init(&mirror->lock);
 		atomic_set(&mirror->ref, 1);
+		INIT_LIST_HEAD(&mirror->mirrors);
 	}
 	return mirror;
 }
 
 static void ff_layout_free_mirror(struct nfs4_ff_layout_mirror *mirror)
 {
+	ff_layout_remove_mirror(mirror);
 	kfree(mirror->fh_versions);
 	nfs4_ff_layout_put_deviceid(mirror->mirror_ds);
 	kfree(mirror);
@@ -267,6 +330,7 @@ ff_layout_alloc_lseg(struct pnfs_layout_hdr *lh,
 		goto out_err_free;
 
 	for (i = 0; i < fls->mirror_array_cnt; i++) {
+		struct nfs4_ff_layout_mirror *mirror;
 		struct nfs4_deviceid devid;
 		struct nfs4_deviceid_node *idnode;
 		u32 ds_count;
@@ -355,6 +419,12 @@ ff_layout_alloc_lseg(struct pnfs_layout_hdr *lh,
 		if (rc)
 			goto out_err_free;
 
+		mirror = ff_layout_add_mirror(lh, fls->mirror_array[i]);
+		if (mirror != fls->mirror_array[i]) {
+			ff_layout_free_mirror(fls->mirror_array[i]);
+			fls->mirror_array[i] = mirror;
+		}
+
 		dprintk("%s: uid %d gid %d\n", __func__,
 			fls->mirror_array[i]->uid,
 			fls->mirror_array[i]->gid);
@@ -1883,24 +1953,27 @@ ff_layout_encode_layoutstats(struct xdr_stream *xdr,
 	*start = cpu_to_be32((xdr->p - start - 1) * 4);
 }
 
-static bool
+static int
 ff_layout_mirror_prepare_stats(struct nfs42_layoutstat_args *args,
 			       struct pnfs_layout_segment *pls,
-			       int *dev_count, int dev_limit)
+			       int dev_limit)
 {
+	struct nfs4_flexfile_layout *ff_layout = FF_LAYOUT_FROM_HDR(pls->pls_layout);
 	struct nfs4_ff_layout_mirror *mirror;
 	struct nfs4_deviceid_node *dev;
 	struct nfs42_layoutstat_devinfo *devinfo;
-	int i;
+	int i = 0;
 
-	for (i = 0; i < FF_LAYOUT_MIRROR_COUNT(pls); i++) {
-		if (*dev_count >= dev_limit)
+	list_for_each_entry(mirror, &ff_layout->mirrors, mirrors) {
+		if (i >= dev_limit)
 			break;
-		mirror = FF_LAYOUT_COMP(pls, i);
-		if (!mirror || !mirror->mirror_ds)
+		if (!mirror->mirror_ds)
 			continue;
-		dev = FF_LAYOUT_DEVID_NODE(pls, i);
-		devinfo = &args->devinfo[*dev_count];
+		/* mirror refcount put in cleanup_layoutstats */
+		if (!atomic_inc_not_zero(&mirror->ref))
+			continue;
+		dev = &mirror->mirror_ds->id_node; 
+		devinfo = &args->devinfo[i];
 		memcpy(&devinfo->dev_id, &dev->deviceid, NFS4_DEVICEID4_SIZE);
 		devinfo->offset = pls->pls_range.offset;
 		devinfo->length = pls->pls_range.length;
@@ -1911,24 +1984,25 @@ ff_layout_mirror_prepare_stats(struct nfs42_layoutstat_args *args,
 		devinfo->layout_type = LAYOUT_FLEX_FILES;
 		devinfo->layoutstats_encode = ff_layout_encode_layoutstats;
 		devinfo->layout_private = mirror;
-		/* mirror refcount put in cleanup_layoutstats */
-		atomic_inc(&mirror->ref);
 
-		++(*dev_count);
+		i++;
 	}
-
-	return *dev_count < dev_limit;
+	return i;
 }
 
 static int
 ff_layout_prepare_layoutstats(struct nfs42_layoutstat_args *args)
 {
+	struct nfs4_flexfile_layout *ff_layout;
+	struct nfs4_ff_layout_mirror *mirror;
 	struct pnfs_layout_segment *pls;
 	int dev_count = 0;
 
 	spin_lock(&args->inode->i_lock);
-	list_for_each_entry(pls, &NFS_I(args->inode)->layout->plh_segs, pls_list) {
-		dev_count += FF_LAYOUT_MIRROR_COUNT(pls);
+	ff_layout = FF_LAYOUT_FROM_HDR(NFS_I(args->inode)->layout);
+	list_for_each_entry(mirror, &ff_layout->mirrors, mirrors) {
+		if (atomic_read(&mirror->ref) != 0)
+			dev_count ++;
 	}
 	spin_unlock(&args->inode->i_lock);
 	/* For now, send at most PNFS_LAYOUTSTATS_MAXDEV statistics */
@@ -1937,20 +2011,14 @@ ff_layout_prepare_layoutstats(struct nfs42_layoutstat_args *args)
 			__func__, dev_count, PNFS_LAYOUTSTATS_MAXDEV);
 		dev_count = PNFS_LAYOUTSTATS_MAXDEV;
 	}
-	args->devinfo = kmalloc(dev_count * sizeof(*args->devinfo), GFP_KERNEL);
+	args->devinfo = kmalloc_array(dev_count, sizeof(*args->devinfo), GFP_NOIO);
 	if (!args->devinfo)
 		return -ENOMEM;
 
 	dev_count = 0;
 	spin_lock(&args->inode->i_lock);
-	list_for_each_entry(pls, &NFS_I(args->inode)->layout->plh_segs, pls_list) {
-		if (!ff_layout_mirror_prepare_stats(args, pls, &dev_count,
-						    PNFS_LAYOUTSTATS_MAXDEV)) {
-			break;
-		}
-	}
+	args->num_dev = ff_layout_mirror_prepare_stats(args, pls, dev_count);
 	spin_unlock(&args->inode->i_lock);
-	args->num_dev = dev_count;
 
 	return 0;
 }
diff --git a/fs/nfs/flexfilelayout/flexfilelayout.h b/fs/nfs/flexfilelayout/flexfilelayout.h
index fe9d3ff7cf85..68cc0d9828f9 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.h
+++ b/fs/nfs/flexfilelayout/flexfilelayout.h
@@ -67,6 +67,8 @@ struct nfs4_ff_layoutstat {
 };
 
 struct nfs4_ff_layout_mirror {
+	struct pnfs_layout_hdr		*layout;
+	struct list_head		mirrors;
 	u32				ds_count;
 	u32				efficiency;
 	struct nfs4_ff_layout_ds	*mirror_ds;
@@ -95,6 +97,7 @@ struct nfs4_ff_layout_segment {
 struct nfs4_flexfile_layout {
 	struct pnfs_layout_hdr generic_hdr;
 	struct pnfs_ds_commit_info commit_info;
+	struct list_head	mirrors;
 	struct list_head	error_list; /* nfs4_ff_layout_ds_err */
 };
 
-- 
2.4.3

[PATCH 4/4] NFSv4.2/pnfs: Make the layoutstats timer configurable

[Trond Myklebust]

Allow advanced users to set the layoutstats timer in order to lengthen
or shorten the period between layoutstat transmissions to the server.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
---
 Documentation/kernel-parameters.txt    | 9 +++++++++
 fs/nfs/flexfilelayout/flexfilelayout.c | 5 ++++-
 fs/nfs/pnfs.c                          | 4 ++++
 fs/nfs/pnfs.h                          | 3 +++
 4 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 1d6f0459cd7b..30d78b561574 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2279,6 +2279,15 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			The default parameter value of '0' causes the kernel
 			not to attempt recovery of lost locks.
 
+	nfs4.layoutstats_timer =
+			[NFSv4.2] Change the rate at which the kernel sends
+			layoutstats to the pNFS metadata server.
+
+			Setting this to value to 0 causes the kernel to use
+			whatever value is the default set by the layout
+			driver. A non-zero value sets the minimum interval
+			in seconds between layoutstats transmissions.
+
 	nfsd.nfs4_disable_idmapping=
 			[NFSv4] When set to the default of '1', the NFSv4
 			server will return only numeric uids and gids to
diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
index 210352741177..738065674484 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -533,14 +533,17 @@ nfs4_ff_layoutstat_start_io(struct nfs4_ff_layout_mirror *mirror,
 			    ktime_t now)
 {
 	static const ktime_t notime = {0};
+	s64 report_interval = FF_LAYOUTSTATS_REPORT_INTERVAL;
 
 	nfs4_ff_start_busy_timer(&layoutstat->busy_timer, now);
 	if (ktime_equal(mirror->start_time, notime))
 		mirror->start_time = now;
 	if (ktime_equal(mirror->last_report_time, notime))
 		mirror->last_report_time = now;
+	if (layoutstats_timer != 0)
+		report_interval = (s64)layoutstats_timer * 1000LL;
 	if (ktime_to_ms(ktime_sub(now, mirror->last_report_time)) >=
-			FF_LAYOUTSTATS_REPORT_INTERVAL) {
+			report_interval) {
 		mirror->last_report_time = now;
 		return true;
 	}
diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 247c5a5d2d6b..3530bb703214 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -2285,3 +2285,7 @@ out_put:
 }
 EXPORT_SYMBOL_GPL(pnfs_report_layoutstat);
 #endif
+
+unsigned int layoutstats_timer;
+module_param(layoutstats_timer, uint, 0644);
+EXPORT_SYMBOL_GPL(layoutstats_timer);
diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
index 02c27f93caf1..d3979dd1037a 100644
--- a/fs/nfs/pnfs.h
+++ b/fs/nfs/pnfs.h
@@ -528,12 +528,15 @@ pnfs_use_threshold(struct nfs4_threshold **dst, struct nfs4_threshold *src,
 					nfss->pnfs_curr_ld->id == src->l_type);
 }
 
+extern unsigned int layoutstats_timer;
+
 #ifdef NFS_DEBUG
 void nfs4_print_deviceid(const struct nfs4_deviceid *dev_id);
 #else
 static inline void nfs4_print_deviceid(const struct nfs4_deviceid *dev_id)
 {
 }
+
 #endif /* NFS_DEBUG */
 #else  /* CONFIG_NFS_V4_1 */
 
-- 
2.4.3