NFSD: Add trace point for SCSI fencing operation.

Add trace point to print client IP address, net namespace number,
device name and status of SCSI pr_preempt command.

Signed-off-by: Dai Ngo <[e-mail]>
Signed-off-by: Chuck Lever <[e-mail]>

fs/nfsd/blocklayout.c

···
 #include "pnfs.h"
 #include "filecache.h"
 #include "vfs.h"
+#include "trace.h"
 
 #define NFSDDBG_FACILITY	NFSDDBG_PNFS
 
···
 {
 	struct nfs4_client *clp = ls->ls_stid.sc_client;
 	struct block_device *bdev = file->nf_file->f_path.mnt->mnt_sb->s_bdev;
+	int status;
 
-	bdev->bd_disk->fops->pr_ops->pr_preempt(bdev, NFSD_MDS_PR_KEY,
+	status = bdev->bd_disk->fops->pr_ops->pr_preempt(bdev, NFSD_MDS_PR_KEY,
 			nfsd4_scsi_pr_key(clp),
 			PR_EXCLUSIVE_ACCESS_REG_ONLY, true);
+	trace_nfsd_pnfs_fence(clp, bdev->bd_disk->disk_name, status);
 }
 
 const struct nfsd4_layout_ops scsi_layout_ops = {

fs/nfsd/trace.h

···
 DEFINE_NFSD_VFS_GETATTR_EVENT(nfsd_vfs_getattr);
 DEFINE_NFSD_VFS_GETATTR_EVENT(nfsd_vfs_statfs);
 
+DECLARE_EVENT_CLASS(nfsd_pnfs_class,
+	TP_PROTO(
+		const struct nfs4_client *clp,
+		const char *dev,
+		int error
+	),
+	TP_ARGS(clp, dev, error),
+	TP_STRUCT__entry(
+		__sockaddr(addr, sizeof(struct sockaddr_in6))
+		__field(unsigned int, netns_ino)
+		__string(dev, dev)
+		__field(int, error)
+	),
+	TP_fast_assign(
+		__assign_sockaddr(addr, &clp->cl_addr,
+				sizeof(struct sockaddr_in6));
+		__entry->netns_ino = clp->net->ns.inum;
+		__assign_str(dev);
+		__entry->error = error;
+	),
+	TP_printk("client=%pISpc nn=%d dev=%s error=%d",
+		__get_sockaddr(addr),
+		__entry->netns_ino,
+		__get_str(dev),
+		__entry->error
+	)
+);
+
+#define DEFINE_NFSD_PNFS_ERR_EVENT(name)		\
+DEFINE_EVENT(nfsd_pnfs_class, nfsd_pnfs_##name,	\
+	TP_PROTO(					\
+		const struct nfs4_client *clp,		\
+		const char *dev,				\
+		int error				\
+	),						\
+	TP_ARGS(clp, dev, error))
+
+DEFINE_NFSD_PNFS_ERR_EVENT(fence);
 #endif /* _NFSD_TRACE_H */
 
 #undef TRACE_INCLUDE_PATH