FAILED: patch "[PATCH] CIFS: Increment num_remote_opens stats counter even in case" failed to apply to 5.5-stable tree

The patch below does not apply to the 5.5-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 1be1fa42ebb73ad8fd67d2c846931361b4e3dd0a Mon Sep 17 00:00:00 2001
From: Shyam Prasad N <[email protected]>
Date: Mon, 9 Mar 2020 01:35:09 -0700
Subject: [PATCH] CIFS: Increment num_remote_opens stats counter even in case
of smb2_query_dir_first

The num_remote_opens counter keeps track of the number of open files which must be maintained by the server at any point. This is a per-tree-connect counter, and the value of this counter gets displayed in the /proc/fs/cifs/Stats output as a following...

Open files: 0 total (local), 1 open on server

                             ^^^^^^^^^^^^^^^^

As a thumb-rule, we want to increment this counter for each open/create that we successfully execute on the server. Similarly, we should decrement the counter when we successfully execute a close.

In this case, an increment was being missed in case of smb2_query_dir_first, in case of successful open. As a result, we would underflow the counter and we could even see the counter go to negative after sufficient smb2_query_dir_first calls.

I tested the stats counter for a bunch of filesystem operations with the fix. And it looks like the counter looks correct to me.

I also check if we missed the increments and decrements elsewhere. It does not seem so. Few other cases where an open is done and we don't increment the counter are the compound calls where the corresponding close is also sent in the request.

index c31e84ee3c39..3dddd20c5e2b 100644
@@ -2222,6 +2222,8 @@ smb2_query_dir_first(const unsigned int xid, struct cifs_tcon *tcon,
 		goto qdf_free;
 	}
 
+	atomic_inc(&tcon->num_remote_opens);
+
 	qd_rsp = (struct smb2_query_directory_rsp *)rsp_iov[1].iov_base;
 	if (qd_rsp->sync_hdr.Status == STATUS_NO_MORE_FILES) {
 		trace_smb3_query_dir_done(xid, fid->persistent_fid,