diff mbox series

fix for patch "cifs" make sure that channel scaling is done only once"

Message ID CAH2r5mvEHKkYqu6CEgk5fzY8tR+UFa-Ynh38gB9Sej4u41YjkA@mail.gmail.com
State New
Headers show
Series fix for patch "cifs" make sure that channel scaling is done only once" | expand

Commit Message

Steve French Jan. 31, 2024, 10:43 p.m. UTC 
Looks like the patch in for-next "cifs: make sure that channel scaling
is done only once" (see attached) was missing some unlocks that were
noticed by compile with C=1 and/or sparse.   See below.



--
Thanks,

Steve

Comments

Steve French Jan. 31, 2024, 10:57 p.m. UTC | #1 
Updated patch (with fix merged into it) attached - and pushed to
for-next pending review and testing


On Wed, Jan 31, 2024 at 4:43 PM Steve French <smfrench@gmail.com> wrote:
>
> Looks like the patch in for-next "cifs: make sure that channel scaling
> is done only once" (see attached) was missing some unlocks that were
> noticed by compile with C=1 and/or sparse.   See below.
>
>
> diff --git a/fs/smb/client/smb2pdu.c b/fs/smb/client/smb2pdu.c
> index 2837fc4465a7..3110aabc32c5 100644
> --- a/fs/smb/client/smb2pdu.c
> +++ b/fs/smb/client/smb2pdu.c
> @@ -400,8 +400,11 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon,
>         }
>
>         spin_lock(&ses->ses_lock);
> -       if (ses->flags & CIFS_SES_FLAG_SCALE_CHANNELS)
> +       if (ses->flags & CIFS_SES_FLAG_SCALE_CHANNELS) {
> +               spin_unlock(&ses->ses_lock);
> +               mutex_unlock(&ses->session_mutex);
>                 goto skip_add_channels;
> +       }
>         ses->flags |= CIFS_SES_FLAG_SCALE_CHANNELS;
>         spin_unlock(&ses->ses_lock);
>
>
> --
> Thanks,
>
> Steve
diff mbox series

Patch

From 17525952fa834a75751f51726eb3cd683948b148 Mon Sep 17 00:00:00 2001
From: Shyam Prasad N <sprasad@microsoft.com>
Date: Mon, 29 Jan 2024 13:58:13 +0000
Subject: [PATCH] cifs: make sure that channel scaling is done only once

Following a successful cifs_tree_connect, we have the code
to scale up/down the number of channels in the session.
However, it is not protected by a lock today.

As a result, this code can be executed by several processes
that select the same channel. The core functions handle this
well, as they pick chan_lock. However, we've seen cases where
smb2_reconnect throws some warnings.

To fix that, this change introduces a flags bitmap inside the
cifs_ses structure. A new flag type is used to ensure that
only one process enters this section at any time.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
---
 fs/smb/client/cifsglob.h |  3 +++
 fs/smb/client/smb2pdu.c  | 17 ++++++++++++++---
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index 16befff4cbb4..9093c507042f 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -1032,6 +1032,8 @@  struct cifs_chan {
 	__u8 signkey[SMB3_SIGN_KEY_SIZE];
 };
 
+#define CIFS_SES_FLAG_SCALE_CHANNELS (0x1)
+
 /*
  * Session structure.  One of these for each uid session with a particular host
  */
@@ -1064,6 +1066,7 @@  struct cifs_ses {
 	enum securityEnum sectype; /* what security flavor was specified? */
 	bool sign;		/* is signing required? */
 	bool domainAuto:1;
+	unsigned int flags;
 	__u16 session_flags;
 	__u8 smb3signingkey[SMB3_SIGN_KEY_SIZE];
 	__u8 smb3encryptionkey[SMB3_ENC_DEC_KEY_SIZE];
diff --git a/fs/smb/client/smb2pdu.c b/fs/smb/client/smb2pdu.c
index 86f6f35b7f32..273e24f9da13 100644
--- a/fs/smb/client/smb2pdu.c
+++ b/fs/smb/client/smb2pdu.c
@@ -399,6 +399,12 @@  smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon,
 		goto out;
 	}
 
+	spin_lock(&ses->ses_lock);
+	if (ses->flags & CIFS_SES_FLAG_SCALE_CHANNELS)
+		goto skip_add_channels;
+	ses->flags |= CIFS_SES_FLAG_SCALE_CHANNELS;
+	spin_unlock(&ses->ses_lock);
+
 	if (!rc &&
 	    (server->capabilities & SMB2_GLOBAL_CAP_MULTI_CHANNEL)) {
 		mutex_unlock(&ses->session_mutex);
@@ -428,17 +434,22 @@  smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon,
 		if (ses->chan_max > ses->chan_count &&
 		    ses->iface_count &&
 		    !SERVER_IS_CHAN(server)) {
-			if (ses->chan_count == 1)
+			if (ses->chan_count == 1) {
 				cifs_server_dbg(VFS, "supports multichannel now\n");
+				queue_delayed_work(cifsiod_wq, &tcon->query_interfaces,
+						 (SMB_INTERFACE_POLL_INTERVAL * HZ));
+			}
 
 			cifs_try_adding_channels(ses);
-			queue_delayed_work(cifsiod_wq, &tcon->query_interfaces,
-					   (SMB_INTERFACE_POLL_INTERVAL * HZ));
 		}
 	} else {
 		mutex_unlock(&ses->session_mutex);
 	}
+
 skip_add_channels:
+	spin_lock(&ses->ses_lock);
+	ses->flags &= ~CIFS_SES_FLAG_SCALE_CHANNELS;
+	spin_unlock(&ses->ses_lock);
 
 	if (smb2_command != SMB2_INTERNAL_CMD)
 		mod_delayed_work(cifsiod_wq, &server->reconnect, 0);
-- 
2.40.1