NFS: Add basic readdir tracing

Add tracing to track how often the client goes to the server for updated
readdir information.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/dir.c

@@ -984,10 +984,14 @@ static int find_and_lock_cache_page(struct nfs_readdir_descriptor *desc)
 		if (desc->page_index == desc->page_index_max)
 			nfs_grow_dtsize(desc);
 		desc->page_index_max = desc->page_index;
+		trace_nfs_readdir_cache_fill(desc->file, nfsi->cookieverf,
+					     desc->last_cookie,
+					     desc->page->index, desc->dtsize);
 		res = nfs_readdir_xdr_to_array(desc, nfsi->cookieverf, verf,
 					       &desc->page, 1);
 		if (res < 0) {
 			nfs_readdir_page_unlock_and_put_cached(desc);
+			trace_nfs_readdir_cache_fill_done(inode, res);
 			if (res == -EBADCOOKIE || res == -ENOTSYNC) {
 				invalidate_inode_pages2(desc->file->f_mapping);
 				desc->page_index = 0;
@@ -1108,7 +1112,14 @@ static int uncached_readdir(struct nfs_readdir_descriptor *desc)
 	desc->duped = 0;
 	desc->page_index_max = 0;
 
+	trace_nfs_readdir_uncached(desc->file, desc->verf, desc->last_cookie,
+				   -1, desc->dtsize);
+
 	status = nfs_readdir_xdr_to_array(desc, desc->verf, verf, arrays, sz);
+	if (status < 0) {
+		trace_nfs_readdir_uncached_done(file_inode(desc->file), status);
+		goto out_free;
+	}
 
 	for (i = 0; !desc->eob && i < sz && arrays[i]; i++) {
 		desc->page = arrays[i];
@@ -1127,7 +1138,7 @@ static int uncached_readdir(struct nfs_readdir_descriptor *desc)
 			 i < (desc->page_index_max >> 1))
 			nfs_shrink_dtsize(desc);
 	}
-
+out_free:
 	for (i = 0; i < sz && arrays[i]; i++)
 		nfs_readdir_page_array_free(arrays[i]);
 out:

fs/nfs/nfstrace.h

@@ -160,6 +160,8 @@ DEFINE_NFS_INODE_EVENT(nfs_fsync_enter);
 DEFINE_NFS_INODE_EVENT_DONE(nfs_fsync_exit);
 DEFINE_NFS_INODE_EVENT(nfs_access_enter);
 DEFINE_NFS_INODE_EVENT_DONE(nfs_set_cache_invalid);
+DEFINE_NFS_INODE_EVENT_DONE(nfs_readdir_cache_fill_done);
+DEFINE_NFS_INODE_EVENT_DONE(nfs_readdir_uncached_done);
 
 TRACE_EVENT(nfs_access_exit,
 		TP_PROTO(
@@ -271,6 +273,72 @@ DEFINE_NFS_UPDATE_SIZE_EVENT(wcc);
 DEFINE_NFS_UPDATE_SIZE_EVENT(update);
 DEFINE_NFS_UPDATE_SIZE_EVENT(grow);
 
+DECLARE_EVENT_CLASS(nfs_readdir_event,
+		TP_PROTO(
+			const struct file *file,
+			const __be32 *verifier,
+			u64 cookie,
+			pgoff_t page_index,
+			unsigned int dtsize
+		),
+
+		TP_ARGS(file, verifier, cookie, page_index, dtsize),
+
+		TP_STRUCT__entry(
+			__field(dev_t, dev)
+			__field(u32, fhandle)
+			__field(u64, fileid)
+			__field(u64, version)
+			__array(char, verifier, NFS4_VERIFIER_SIZE)
+			__field(u64, cookie)
+			__field(pgoff_t, index)
+			__field(unsigned int, dtsize)
+		),
+
+		TP_fast_assign(
+			const struct inode *dir = file_inode(file);
+			const struct nfs_inode *nfsi = NFS_I(dir);
+
+			__entry->dev = dir->i_sb->s_dev;
+			__entry->fileid = nfsi->fileid;
+			__entry->fhandle = nfs_fhandle_hash(&nfsi->fh);
+			__entry->version = inode_peek_iversion_raw(dir);
+			if (cookie != 0)
+				memcpy(__entry->verifier, verifier,
+				       NFS4_VERIFIER_SIZE);
+			else
+				memset(__entry->verifier, 0,
+				       NFS4_VERIFIER_SIZE);
+			__entry->cookie = cookie;
+			__entry->index = page_index;
+			__entry->dtsize = dtsize;
+		),
+
+		TP_printk(
+			"fileid=%02x:%02x:%llu fhandle=0x%08x version=%llu "
+			"cookie=%s:0x%llx cache_index=%lu dtsize=%u",
+			MAJOR(__entry->dev), MINOR(__entry->dev),
+			(unsigned long long)__entry->fileid, __entry->fhandle,
+			__entry->version, show_nfs4_verifier(__entry->verifier),
+			(unsigned long long)__entry->cookie, __entry->index,
+			__entry->dtsize
+		)
+);
+
+#define DEFINE_NFS_READDIR_EVENT(name) \
+	DEFINE_EVENT(nfs_readdir_event, name, \
+			TP_PROTO( \
+				const struct file *file, \
+				const __be32 *verifier, \
+				u64 cookie, \
+				pgoff_t page_index, \
+				unsigned int dtsize \
+				), \
+			TP_ARGS(file, verifier, cookie, page_index, dtsize))
+
+DEFINE_NFS_READDIR_EVENT(nfs_readdir_cache_fill);
+DEFINE_NFS_READDIR_EVENT(nfs_readdir_uncached);
+
 DECLARE_EVENT_CLASS(nfs_lookup_event,
 		TP_PROTO(
 			const struct inode *dir,