Re: [PATCH 3/3] usb: gadget: f_fs: Fix mmgrab()/mmdrop() balance.

[Neill Kapron <nkapron@google.com>]

On Tue, Sep 01, 2026 at 02:09:08PM +0200, Ingo Rohloff wrote:
> This fixes commit 5eb5c72c72fe ("USB: gadget: ffs: fix mm lifetime
> handling").  The problem is that the previous patch calls mmgrab() for
> reads and writes, but it only calls mmdrop() for reads.  So with each
> completed async IO write (via an USB IN endpoint) the number of mm_count
> increases.
> 
> Signed-off-by: Ingo Rohloff <ingo.rohloff@lauterbach.com>
> ---
>  drivers/usb/gadget/function/f_fs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> index 9dec09d06ca9..0be989c7c23f 100644
> --- a/drivers/usb/gadget/function/f_fs.c
> +++ b/drivers/usb/gadget/function/f_fs.c
> @@ -884,8 +884,8 @@ static void ffs_user_copy_worker(struct work_struct *work)
>  		} else {
>  			ret = -EFAULT;
>  		}
> -		mmdrop(io_data->mm);
>  	}
> +	mmdrop(io_data->mm);
>  
>  	io_data->kiocb->ki_complete(io_data->kiocb, ret);
>  
> -- 
> 2.55.0
>

Hi Ingo,

This looks correct to me, and has been reported to me separately. Can
you resend this change on its own ahead of the rest of the series and
include the Fixes: and Cc: stable tags as Hongyu already pointed out?

With that:

Reviewed-by: Neill Kapron <nkapron@google.com>

Thanks,
Neill