Re: [PATCH 1/2] cifs: client: force multichannel=off when max_channels=1

[Enzo Matsumiya]

On 09/22, Henrique Carvalho wrote:
> Hi Rajasi,
>
> On 9/22/25 5:24 AM, rajasimandalos@xxxxxxxxx wrote:
> > From: Rajasi Mandal <rajasimandal@xxxxxxxxxxxxx>
> >
> > Previously, specifying both multichannel and max_channels=1 as mount
> > options would leave multichannel enabled, even though it is not
> > meaningful when only one channel is allowed. This led to confusion and
> > inconsistent behavior, as the client would advertise multichannel
> > capability but never establish secondary channels.
> >
> > Fix this by forcing multichannel to false whenever max_channels=1,
> > ensuring the mount configuration is consistent and matches user intent.
> > This prevents the client from advertising or attempting multichannel
> > support when it is not possible.
> >
> > Signed-off-by: Rajasi Mandal <rajasimandal@xxxxxxxxxxxxx>
> > ---
> >  fs/smb/client/fs_context.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
> > index 072383899e81..43552b44f613 100644
> > --- a/fs/smb/client/fs_context.c
> > +++ b/fs/smb/client/fs_context.c
> > @@ -1820,6 +1820,13 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
> >  		goto cifs_parse_mount_err;
> >  	}
> >
> > +	/*
> > +	 * Multichannel is not meaningful if max_channels is 1.
> > +	 * Force multichannel to false to ensure consistent configuration.
> > +	 */
> > +	if (ctx->multichannel && ctx->max_channels == 1)
> > +		ctx->multichannel = false;
> > +
> >  	return 0;
> >
> >   cifs_parse_mount_err:
>
> Do we even need ->multichannel flag at all? Maybe we could replace
> ->multichannel for a function that checks for max_channels > 1?

I agree with Henrique.

I'd actually like to propose going even further and having the whole
module behaving as if multichannel was always on, even with
max_channels=1 -- the only difference being the need to run the
query_interfaces worker.

This is probably work for another patch/series though.


Cheers,

Enzo