pnfs/flexfiles: add ff_layout_prepare_layoutstats

It fills in the generic part of LAYOUTSTATS call. One thing to note
is that we don't really track if IO is continuous or not. So just fake
to use the completed bytes for it.

Still missing flexfiles specific part, which will be included in the next patch.
Reviewed-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Peng Tao <tao.peng@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/flexfilelayout/flexfilelayout.c

@@ -20,6 +20,7 @@
 #include "../nfs4trace.h"
 #include "../iostat.h"
 #include "../nfs.h"
+#include "../nfs42.h"
 
 #define NFSDBG_FACILITY         NFSDBG_PNFS_LD
 
@@ -1659,6 +1660,75 @@ ff_layout_encode_layoutreturn(struct pnfs_layout_hdr *lo,
 	dprintk("%s: Return\n", __func__);
 }
 
+static bool
+ff_layout_mirror_prepare_stats(struct nfs42_layoutstat_args *args,
+			       struct pnfs_layout_segment *pls,
+			       int *dev_count, int dev_limit)
+{
+	struct nfs4_ff_layout_mirror *mirror;
+	struct nfs4_deviceid_node *dev;
+	struct nfs42_layoutstat_devinfo *devinfo;
+	int i;
+
+	for (i = 0; i <= FF_LAYOUT_MIRROR_COUNT(pls); i++) {
+		if (*dev_count >= dev_limit)
+			break;
+		mirror = FF_LAYOUT_COMP(pls, i);
+		dev = FF_LAYOUT_DEVID_NODE(pls, i);
+		devinfo = &args->devinfo[*dev_count];
+		memcpy(&devinfo->dev_id, &dev->deviceid, NFS4_DEVICEID4_SIZE);
+		devinfo->offset = pls->pls_range.offset;
+		devinfo->length = pls->pls_range.length;
+		/* well, we don't really know if IO is continuous or not! */
+		devinfo->read_count = mirror->read_stat.io_stat.bytes_completed;
+		devinfo->read_bytes = mirror->read_stat.io_stat.bytes_completed;
+		devinfo->write_count = mirror->write_stat.io_stat.bytes_completed;
+		devinfo->write_bytes = mirror->write_stat.io_stat.bytes_completed;
+		devinfo->layout_type = LAYOUT_FLEX_FILES;
+		devinfo->layoutstats_encode = NULL;
+		devinfo->layout_private = NULL;
+
+		++(*dev_count);
+	}
+
+	return *dev_count < dev_limit;
+}
+
+static int
+ff_layout_prepare_layoutstats(struct nfs42_layoutstat_args *args)
+{
+	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);
+	}
+	spin_unlock(&args->inode->i_lock);
+	/* For now, send at most PNFS_LAYOUTSTATS_MAXDEV statistics */
+	if (dev_count > PNFS_LAYOUTSTATS_MAXDEV) {
+		dprintk("%s: truncating devinfo to limit (%d:%d)\n",
+			__func__, dev_count, PNFS_LAYOUTSTATS_MAXDEV);
+		dev_count = PNFS_LAYOUTSTATS_MAXDEV;
+	}
+	args->devinfo = kmalloc(dev_count * sizeof(*args->devinfo), GFP_KERNEL);
+	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;
+		}
+	}
+	spin_unlock(&args->inode->i_lock);
+	args->num_dev = dev_count;
+
+	return 0;
+}
+
 static struct pnfs_layoutdriver_type flexfilelayout_type = {
 	.id			= LAYOUT_FLEX_FILES,
 	.name			= "LAYOUT_FLEX_FILES",
@@ -1681,6 +1751,7 @@ static struct pnfs_layoutdriver_type flexfilelayout_type = {
 	.alloc_deviceid_node    = ff_layout_alloc_deviceid_node,
 	.encode_layoutreturn    = ff_layout_encode_layoutreturn,
 	.sync			= pnfs_nfs_generic_sync,
+	.prepare_layoutstats	= ff_layout_prepare_layoutstats,
 };
 
 static int __init nfs4flexfilelayout_init(void)