nfs/localio: add tracepoints for misaligned DIO READ and WRITE support

Add nfs_local_dio_class and use it to create nfs_local_dio_read,
nfs_local_dio_write and nfs_local_dio_misaligned trace events.

These trace events show how NFS LOCALIO splits a given misaligned
IO into a mix of misaligned head and/or tail extents and a DIO-aligned
middle extent.  The misaligned head and/or tail extents are issued
using buffered IO and the DIO-aligned middle is issued using O_DIRECT.

This combination of trace events is useful for LOCALIO DIO READs:

  echo 1 > /sys/kernel/tracing/events/nfs/nfs_local_dio_read/enable
  echo 1 > /sys/kernel/tracing/events/nfs/nfs_local_dio_misaligned/enable
  echo 1 > /sys/kernel/tracing/events/nfs/nfs_initiate_read/enable
  echo 1 > /sys/kernel/tracing/events/nfs/nfs_readpage_done/enable
  echo 1 > /sys/kernel/tracing/events/xfs/xfs_file_direct_read/enable

This combination of trace events is useful for LOCALIO DIO WRITEs:

  echo 1 > /sys/kernel/tracing/events/nfs/nfs_local_dio_write/enable
  echo 1 > /sys/kernel/tracing/events/nfs/nfs_local_dio_misaligned/enable
  echo 1 > /sys/kernel/tracing/events/nfs/nfs_initiate_write/enable
  echo 1 > /sys/kernel/tracing/events/nfs/nfs_writeback_done/enable
  echo 1 > /sys/kernel/tracing/events/xfs/xfs_file_direct_write/enable

Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

fs/nfs/internal.h

@@ -456,6 +456,16 @@ extern int nfs_wait_bit_killable(struct wait_bit_key *key, int mode);
 
 #if IS_ENABLED(CONFIG_NFS_LOCALIO)
 /* localio.c */
+struct nfs_local_dio {
+	u32 mem_align;
+	u32 offset_align;
+	loff_t middle_offset;
+	loff_t end_offset;
+	ssize_t	start_len;	/* Length for misaligned first extent */
+	ssize_t	middle_len;	/* Length for DIO-aligned middle extent */
+	ssize_t	end_len;	/* Length for misaligned last extent */
+};
+
 extern void nfs_local_probe_async(struct nfs_client *);
 extern void nfs_local_probe_async_work(struct work_struct *);
 extern struct nfsd_file *nfs_local_open_fh(struct nfs_client *,

fs/nfs/localio.c

@@ -322,16 +322,6 @@ nfs_local_iocb_alloc(struct nfs_pgio_header *hdr,
 	return iocb;
 }
 
-struct nfs_local_dio {
-	u32 mem_align;
-	u32 offset_align;
-	loff_t middle_offset;
-	loff_t end_offset;
-	ssize_t	start_len;	/* Length for misaligned first extent */
-	ssize_t	middle_len;	/* Length for DIO-aligned middle extent */
-	ssize_t	end_len;	/* Length for misaligned last extent */
-};
-
 static bool
 nfs_is_local_dio_possible(struct nfs_local_kiocb *iocb, int rw,
 			  size_t len, struct nfs_local_dio *local_dio)
@@ -367,6 +357,10 @@ nfs_is_local_dio_possible(struct nfs_local_kiocb *iocb, int rw,
 	local_dio->middle_len = middle_end - start_end;
 	local_dio->end_len = orig_end - middle_end;
 
+	if (rw == ITER_DEST)
+		trace_nfs_local_dio_read(hdr->inode, offset, len, local_dio);
+	else
+		trace_nfs_local_dio_write(hdr->inode, offset, len, local_dio);
 	return true;
 }
 
@@ -446,8 +440,11 @@ nfs_local_iters_setup_dio(struct nfs_local_kiocb *iocb, int rw,
 		nfs_iov_iter_aligned_bvec(&iters[n_iters],
 			local_dio->mem_align-1, local_dio->offset_align-1);
 
-	if (unlikely(!iocb->iter_is_dio_aligned[n_iters]))
+	if (unlikely(!iocb->iter_is_dio_aligned[n_iters])) {
+		trace_nfs_local_dio_misaligned(iocb->hdr->inode,
+			iocb->hdr->args.offset, len, local_dio);
 		return 0; /* no DIO-aligned IO possible */
+	}
 	++n_iters;
 
 	iocb->n_iters = n_iters;

fs/nfs/nfs2xdr.c

@@ -23,8 +23,8 @@
 #include <linux/nfs2.h>
 #include <linux/nfs_fs.h>
 #include <linux/nfs_common.h>
-#include "nfstrace.h"
 #include "internal.h"
+#include "nfstrace.h"
 
 #define NFSDBG_FACILITY		NFSDBG_XDR
 

fs/nfs/nfs3xdr.c

@@ -23,8 +23,8 @@
 #include <linux/nfsacl.h>
 #include <linux/nfs_common.h>
 
-#include "nfstrace.h"
 #include "internal.h"
+#include "nfstrace.h"
 
 #define NFSDBG_FACILITY		NFSDBG_XDR
 

fs/nfs/nfstrace.h

@@ -1732,6 +1732,76 @@ DEFINE_NFS_DIRECT_REQ_EVENT(nfs_direct_write_completion);
 DEFINE_NFS_DIRECT_REQ_EVENT(nfs_direct_write_schedule_iovec);
 DEFINE_NFS_DIRECT_REQ_EVENT(nfs_direct_write_reschedule_io);
 
+#if IS_ENABLED(CONFIG_NFS_LOCALIO)
+
+DECLARE_EVENT_CLASS(nfs_local_dio_class,
+	TP_PROTO(
+		const struct inode *inode,
+		loff_t offset,
+		ssize_t count,
+		const struct nfs_local_dio *local_dio
+	),
+	TP_ARGS(inode, offset, count, local_dio),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(u64, fileid)
+		__field(u32, fhandle)
+		__field(loff_t, offset)
+		__field(ssize_t, count)
+		__field(u32, mem_align)
+		__field(u32, offset_align)
+		__field(loff_t, start)
+		__field(ssize_t, start_len)
+		__field(loff_t, middle)
+		__field(ssize_t, middle_len)
+		__field(loff_t, end)
+		__field(ssize_t, end_len)
+	),
+	TP_fast_assign(
+		const struct nfs_inode *nfsi = NFS_I(inode);
+		const struct nfs_fh *fh = &nfsi->fh;
+
+		__entry->dev = inode->i_sb->s_dev;
+		__entry->fileid = nfsi->fileid;
+		__entry->fhandle = nfs_fhandle_hash(fh);
+		__entry->offset = offset;
+		__entry->count = count;
+		__entry->mem_align = local_dio->mem_align;
+		__entry->offset_align = local_dio->offset_align;
+		__entry->start = offset;
+		__entry->start_len = local_dio->start_len;
+		__entry->middle = local_dio->middle_offset;
+		__entry->middle_len = local_dio->middle_len;
+		__entry->end = local_dio->end_offset;
+		__entry->end_len = local_dio->end_len;
+	),
+	TP_printk("fileid=%02x:%02x:%llu fhandle=0x%08x "
+		  "offset=%lld count=%zd "
+		  "mem_align=%u offset_align=%u "
+		  "start=%llu+%zd middle=%llu+%zd end=%llu+%zd",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  (unsigned long long)__entry->fileid,
+		  __entry->fhandle, __entry->offset, __entry->count,
+		  __entry->mem_align, __entry->offset_align,
+		  __entry->start, __entry->start_len,
+		  __entry->middle, __entry->middle_len,
+		  __entry->end, __entry->end_len)
+)
+
+#define DEFINE_NFS_LOCAL_DIO_EVENT(name)		\
+DEFINE_EVENT(nfs_local_dio_class, nfs_local_dio_##name,	\
+	TP_PROTO(const struct inode *inode,		\
+		 loff_t offset,				\
+		 ssize_t count,				\
+		 const struct nfs_local_dio *local_dio),\
+	TP_ARGS(inode, offset, count, local_dio))
+
+DEFINE_NFS_LOCAL_DIO_EVENT(read);
+DEFINE_NFS_LOCAL_DIO_EVENT(write);
+DEFINE_NFS_LOCAL_DIO_EVENT(misaligned);
+
+#endif /* CONFIG_NFS_LOCALIO */
+
 TRACE_EVENT(nfs_fh_to_dentry,
 		TP_PROTO(
 			const struct super_block *sb,