netdev - Re: [PATCH] qrtr: Convert qrtr

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Message-ID: <9aa67df2-a539-29eb-c9e9-4dddcb73ec19@gmail.com>
Date:   Fri, 5 Jun 2020 09:43:25 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Matthew Wilcox <willy@...radead.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH] qrtr: Convert qrtr_ports from IDR to XArray



On 6/5/20 5:00 AM, Matthew Wilcox wrote:
> From: "Matthew Wilcox (Oracle)" <willy@...radead.org>
> 
> The XArray interface is easier for this driver to use.  Also fixes a
> bug reported by the improper use of GFP_ATOMIC.
> 

This does not look stable candidate.

If you try to add a Fixes: tag, you might discover that this bug is old,
and I do not believe XArray has been backported to stable branches ?


Please submit a fix suitable for old kernels (as old as v4.7)

Then when net-next is open in ~2 weeks, the Xarray stuff can be proposed.

Thanks.

> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> ---
>  net/qrtr/qrtr.c | 39 +++++++++++++--------------------------
>  1 file changed, 13 insertions(+), 26 deletions(-)
> 
> diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c
> index 2d8d6131bc5f..488f8f326ee5 100644
> --- a/net/qrtr/qrtr.c
> +++ b/net/qrtr/qrtr.c
> @@ -20,6 +20,7 @@
>  /* auto-bind range */
>  #define QRTR_MIN_EPH_SOCKET 0x4000
>  #define QRTR_MAX_EPH_SOCKET 0x7fff
> +#define QRTR_PORT_RANGE	XA_LIMIT(QRTR_MIN_EPH_SOCKET, QRTR_MAX_EPH_SOCKET)
>  
>  /**
>   * struct qrtr_hdr_v1 - (I|R)PCrouter packet header version 1
> @@ -106,8 +107,7 @@ static LIST_HEAD(qrtr_all_nodes);
>  static DEFINE_MUTEX(qrtr_node_lock);
>  
>  /* local port allocation management */
> -static DEFINE_IDR(qrtr_ports);
> -static DEFINE_MUTEX(qrtr_port_lock);
> +static DEFINE_XARRAY_ALLOC(qrtr_ports);
>  
>  /**
>   * struct qrtr_node - endpoint node
> @@ -623,7 +623,7 @@ static struct qrtr_sock *qrtr_port_lookup(int port)
>  		port = 0;
>  
>  	rcu_read_lock();
> -	ipc = idr_find(&qrtr_ports, port);
> +	ipc = xa_load(&qrtr_ports, port);
>  	if (ipc)
>  		sock_hold(&ipc->sk);
>  	rcu_read_unlock();
> @@ -665,9 +665,7 @@ static void qrtr_port_remove(struct qrtr_sock *ipc)
>  
>  	__sock_put(&ipc->sk);
>  
> -	mutex_lock(&qrtr_port_lock);
> -	idr_remove(&qrtr_ports, port);
> -	mutex_unlock(&qrtr_port_lock);
> +	xa_erase(&qrtr_ports, port);
>  
>  	/* Ensure that if qrtr_port_lookup() did enter the RCU read section we
>  	 * wait for it to up increment the refcount */
> @@ -688,25 +686,18 @@ static int qrtr_port_assign(struct qrtr_sock *ipc, int *port)
>  {
>  	int rc;
>  
> -	mutex_lock(&qrtr_port_lock);
>  	if (!*port) {
> -		rc = idr_alloc(&qrtr_ports, ipc,
> -			       QRTR_MIN_EPH_SOCKET, QRTR_MAX_EPH_SOCKET + 1,
> -			       GFP_ATOMIC);
> -		if (rc >= 0)
> -			*port = rc;
> +		rc = xa_alloc(&qrtr_ports, port, ipc, QRTR_PORT_RANGE,
> +				GFP_KERNEL);
>  	} else if (*port < QRTR_MIN_EPH_SOCKET && !capable(CAP_NET_ADMIN)) {
>  		rc = -EACCES;
>  	} else if (*port == QRTR_PORT_CTRL) {
> -		rc = idr_alloc(&qrtr_ports, ipc, 0, 1, GFP_ATOMIC);
> +		rc = xa_insert(&qrtr_ports, 0, ipc, GFP_KERNEL);
>  	} else {
> -		rc = idr_alloc(&qrtr_ports, ipc, *port, *port + 1, GFP_ATOMIC);
> -		if (rc >= 0)
> -			*port = rc;
> +		rc = xa_insert(&qrtr_ports, *port, ipc, GFP_KERNEL);
>  	}
> -	mutex_unlock(&qrtr_port_lock);
>  
> -	if (rc == -ENOSPC)
> +	if (rc == -EBUSY)
>  		return -EADDRINUSE;
>  	else if (rc < 0)
>  		return rc;
> @@ -720,20 +711,16 @@ static int qrtr_port_assign(struct qrtr_sock *ipc, int *port)
>  static void qrtr_reset_ports(void)
>  {
>  	struct qrtr_sock *ipc;
> -	int id;
> -
> -	mutex_lock(&qrtr_port_lock);
> -	idr_for_each_entry(&qrtr_ports, ipc, id) {
> -		/* Don't reset control port */
> -		if (id == 0)
> -			continue;
> +	unsigned long index;
>  
> +	rcu_read_lock();
> +	xa_for_each_start(&qrtr_ports, index, ipc, 1) {
>  		sock_hold(&ipc->sk);
>  		ipc->sk.sk_err = ENETRESET;
>  		ipc->sk.sk_error_report(&ipc->sk);
>  		sock_put(&ipc->sk);
>  	}
> -	mutex_unlock(&qrtr_port_lock);
> +	rcu_read_unlock();
>  }
>  
>  /* Bind socket to address.
>