smb: client: add tracepoints for deferred handle caching

Add tracepoints to observe handle caching behavior.

smb3_open_cached: emitted when an open reuses a cached handle from
a previous deferred close, avoiding a network round-trip

smb3_close_cached: emitted when a close is deferred (handle cached
for potential reuse by subsequent opens)

Signed-off-by: Bharath SM <bharathsm@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: bharathsm-ms

fs/smb/client/file.c

@@ -1083,6 +1083,9 @@ int cifs_open(struct inode *inode, struct file *file)
 		rc = cfile ? 0 : -ENOENT;
 	}
 	if (rc == 0) {
+		trace_smb3_open_cached(xid, tcon->tid, tcon->ses->Suid,
+				       cfile->fid.persistent_fid,
+				       file->f_flags, cfile->f_flags);
 		file->private_data = cfile;
 		spin_lock(&CIFS_I(inode)->deferred_lock);
 		cifs_del_deferred_close(cfile);
@@ -1442,6 +1445,7 @@ int cifs_close(struct inode *inode, struct file *file)
 	struct cifsInodeInfo *cinode = CIFS_I(inode);
 	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
 	struct cifs_deferred_close *dclose;
+	struct cifs_tcon *tcon;
 
 	cifs_fscache_unuse_inode_cookie(inode, file->f_mode & FMODE_WRITE);
 
@@ -1468,6 +1472,10 @@ int cifs_close(struct inode *inode, struct file *file)
 					cifsFileInfo_get(cfile);
 			} else {
 				/* Deferred close for files */
+				tcon = tlink_tcon(cfile->tlink);
+				trace_smb3_close_cached(tcon->tid, tcon->ses->Suid,
+						cfile->fid.persistent_fid,
+						cifs_sb->ctx->closetimeo);
 				queue_delayed_work(deferredclose_wq,
 						&cfile->deferred, cifs_sb->ctx->closetimeo);
 				cfile->deferred_close_scheduled = true;

fs/smb/client/trace.h

@@ -1361,6 +1361,57 @@ DEFINE_EVENT(smb3_open_done_class, smb3_##name,  \
 DEFINE_SMB3_OPEN_DONE_EVENT(open_done);
 DEFINE_SMB3_OPEN_DONE_EVENT(posix_mkdir_done);
 
+TRACE_EVENT(smb3_open_cached,
+	TP_PROTO(unsigned int xid,
+		__u32 tid,
+		__u64 sesid,
+		__u64 fid,
+		unsigned int oflags,
+		unsigned int cflags),
+	TP_ARGS(xid, tid, sesid, fid, oflags, cflags),
+	TP_STRUCT__entry(
+		__field(unsigned int, xid)
+		__field(__u32, tid)
+		__field(__u64, sesid)
+		__field(__u64, fid)
+		__field(unsigned int, oflags)
+		__field(unsigned int, cflags)
+	),
+	TP_fast_assign(
+		__entry->xid = xid;
+		__entry->tid = tid;
+		__entry->sesid = sesid;
+		__entry->fid = fid;
+		__entry->oflags = oflags;
+		__entry->cflags = cflags;
+	),
+	TP_printk("xid=%u sid=0x%llx tid=0x%x fid=0x%llx oflags=0x%x cflags=0x%x",
+		__entry->xid, __entry->sesid, __entry->tid, __entry->fid,
+		__entry->oflags, __entry->cflags)
+);
+
+TRACE_EVENT(smb3_close_cached,
+	TP_PROTO(__u32 tid,
+		__u64 sesid,
+		__u64 fid,
+		unsigned long delay_jiffies),
+	TP_ARGS(tid, sesid, fid, delay_jiffies),
+	TP_STRUCT__entry(
+		__field(__u32, tid)
+		__field(__u64, sesid)
+		__field(__u64, fid)
+		__field(unsigned long, delay_jiffies)
+	),
+	TP_fast_assign(
+		__entry->tid = tid;
+		__entry->sesid = sesid;
+		__entry->fid = fid;
+		__entry->delay_jiffies = delay_jiffies;
+	),
+	TP_printk("sid=0x%llx tid=0x%x fid=0x%llx delay_jiffies=%lu",
+		__entry->sesid, __entry->tid, __entry->fid, __entry->delay_jiffies)
+);
+
 
 DECLARE_EVENT_CLASS(smb3_lease_done_class,
 	TP_PROTO(__u32	lease_state,