Re: [PATCH v2 1/2] SUNRPC: Fix memory reclaim deadlocks in rpciod

[Junxiao Bi <junxiao.bi-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>]

Hi Trond,

Thanks for looking into this issue.

PF_FSTRANS is also used in file net/sunrpc/xprtrdma/transport.c -
xprt_rdma_connect_worker(), do we also add PF_MEMALLOC_NOIO there?

Also PF_FSTRANS seemed duplicated with PF_MEMALLOC_NOIO, can we directly
replace it with PF_MEMALLOC_NOIO?

Thanks,
Junxiao.

On 08/23/2014 06:49 AM, Trond Myklebust wrote:
> Junxiao Bi reports seeing the following deadlock:
> 
> @ crash> bt 1539
> @ PID: 1539   TASK: ffff88178f64a040  CPU: 1   COMMAND: "rpciod/1"
> @  #0 [ffff88178f64d2c0] schedule at ffffffff8145833a
> @  #1 [ffff88178f64d348] io_schedule at ffffffff8145842c
> @  #2 [ffff88178f64d368] sync_page at ffffffff810d8161
> @  #3 [ffff88178f64d378] __wait_on_bit at ffffffff8145895b
> @  #4 [ffff88178f64d3b8] wait_on_page_bit at ffffffff810d82fe
> @  #5 [ffff88178f64d418] wait_on_page_writeback at ffffffff810e2a1a
> @  #6 [ffff88178f64d438] shrink_page_list at ffffffff810e34e1
> @  #7 [ffff88178f64d588] shrink_list at ffffffff810e3dbe
> @  #8 [ffff88178f64d6f8] shrink_zone at ffffffff810e425e
> @  #9 [ffff88178f64d7b8] do_try_to_free_pages at ffffffff810e4978
> @ #10 [ffff88178f64d828] try_to_free_pages at ffffffff810e4c31
> @ #11 [ffff88178f64d8c8] __alloc_pages_nodemask at ffffffff810de370
> @ #12 [ffff88178f64d978] kmem_getpages at ffffffff8110e18b
> @ #13 [ffff88178f64d9a8] fallback_alloc at ffffffff8110e35e
> @ #14 [ffff88178f64da08] ____cache_alloc_node at ffffffff8110e51f
> @ #15 [ffff88178f64da48] __kmalloc at ffffffff8110efba
> @ #16 [ffff88178f64da98] xs_setup_xprt at ffffffffa00a563f [sunrpc]
> @ #17 [ffff88178f64dad8] xs_setup_tcp at ffffffffa00a7648 [sunrpc]
> @ #18 [ffff88178f64daf8] xprt_create_transport at ffffffffa00a478f [sunrpc]
> @ #19 [ffff88178f64db18] rpc_create at ffffffffa00a2d7a [sunrpc]
> @ #20 [ffff88178f64dbf8] rpcb_create at ffffffffa00b026b [sunrpc]
> @ #21 [ffff88178f64dc98] rpcb_getport_async at ffffffffa00b0c94 [sunrpc]
> @ #22 [ffff88178f64ddf8] call_bind at ffffffffa00a11f8 [sunrpc]
> @ #23 [ffff88178f64de18] __rpc_execute at ffffffffa00a88ef [sunrpc]
> @ #24 [ffff88178f64de58] rpc_async_schedule at ffffffffa00a9187 [sunrpc]
> @ #25 [ffff88178f64de78] worker_thread at ffffffff81072ed2
> @ #26 [ffff88178f64dee8] kthread at ffffffff81076df3
> @ #27 [ffff88178f64df48] kernel_thread at ffffffff81012e2a
> @ crash>
> 
> Junxiao notes that the problem is not limited to the rpcbind client. In
> fact we can trigger the exact same problem when trying to reconnect to
> the server, and we find ourselves calling sock_alloc().
> 
> The following solution should work for all kernels that support the
> PF_MEMALLOC_NOIO flag (i.e. Linux 3.9 and newer).
> 
> Link: http://lkml.kernel.org/r/53F6F772.6020708-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org
> Reported-by: Junxiao Bi <junxiao.bi-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> Cc: stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org # 3.9+
> Signed-off-by: Trond Myklebust <trond.myklebust-7I+n7zu2hftEKMMhf/gKZA@public.gmane.org>
> ---
>  net/sunrpc/sched.c    |  5 +++--
>  net/sunrpc/xprtsock.c | 15 ++++++++-------
>  2 files changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
> index 9358c79fd589..ab3aff71ff93 100644
> --- a/net/sunrpc/sched.c
> +++ b/net/sunrpc/sched.c
> @@ -19,6 +19,7 @@
>  #include <linux/spinlock.h>
>  #include <linux/mutex.h>
>  #include <linux/freezer.h>
> +#include <linux/sched.h>
>  
>  #include <linux/sunrpc/clnt.h>
>  
> @@ -821,9 +822,9 @@ void rpc_execute(struct rpc_task *task)
>  
>  static void rpc_async_schedule(struct work_struct *work)
>  {
> -	current->flags |= PF_FSTRANS;
> +	current->flags |= PF_FSTRANS | PF_MEMALLOC_NOIO;
>  	__rpc_execute(container_of(work, struct rpc_task, u.tk_work));
> -	current->flags &= ~PF_FSTRANS;
> +	current->flags &= ~(PF_FSTRANS | PF_MEMALLOC_NOIO);
>  }
>  
>  /**
> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
> index 43cd89eacfab..1d6d4d84b299 100644
> --- a/net/sunrpc/xprtsock.c
> +++ b/net/sunrpc/xprtsock.c
> @@ -38,6 +38,7 @@
>  #include <linux/sunrpc/svcsock.h>
>  #include <linux/sunrpc/xprtsock.h>
>  #include <linux/file.h>
> +#include <linux/sched.h>
>  #ifdef CONFIG_SUNRPC_BACKCHANNEL
>  #include <linux/sunrpc/bc_xprt.h>
>  #endif
> @@ -1927,7 +1928,7 @@ static int xs_local_setup_socket(struct sock_xprt *transport)
>  	struct socket *sock;
>  	int status = -EIO;
>  
> -	current->flags |= PF_FSTRANS;
> +	current->flags |= PF_FSTRANS | PF_MEMALLOC_NOIO;
>  
>  	clear_bit(XPRT_CONNECTION_ABORT, &xprt->state);
>  	status = __sock_create(xprt->xprt_net, AF_LOCAL,
> @@ -1968,7 +1969,7 @@ static int xs_local_setup_socket(struct sock_xprt *transport)
>  out:
>  	xprt_clear_connecting(xprt);
>  	xprt_wake_pending_tasks(xprt, status);
> -	current->flags &= ~PF_FSTRANS;
> +	current->flags &= ~(PF_FSTRANS | PF_MEMALLOC_NOIO);
>  	return status;
>  }
>  
> @@ -2071,7 +2072,7 @@ static void xs_udp_setup_socket(struct work_struct *work)
>  	struct socket *sock = transport->sock;
>  	int status = -EIO;
>  
> -	current->flags |= PF_FSTRANS;
> +	current->flags |= PF_FSTRANS | PF_MEMALLOC_NOIO;
>  
>  	/* Start by resetting any existing state */
>  	xs_reset_transport(transport);
> @@ -2092,7 +2093,7 @@ static void xs_udp_setup_socket(struct work_struct *work)
>  out:
>  	xprt_clear_connecting(xprt);
>  	xprt_wake_pending_tasks(xprt, status);
> -	current->flags &= ~PF_FSTRANS;
> +	current->flags &= ~(PF_FSTRANS | PF_MEMALLOC_NOIO);
>  }
>  
>  /*
> @@ -2229,7 +2230,7 @@ static void xs_tcp_setup_socket(struct work_struct *work)
>  	struct rpc_xprt *xprt = &transport->xprt;
>  	int status = -EIO;
>  
> -	current->flags |= PF_FSTRANS;
> +	current->flags |= PF_FSTRANS | PF_MEMALLOC_NOIO;
>  
>  	if (!sock) {
>  		clear_bit(XPRT_CONNECTION_ABORT, &xprt->state);
> @@ -2276,7 +2277,7 @@ static void xs_tcp_setup_socket(struct work_struct *work)
>  	case -EINPROGRESS:
>  	case -EALREADY:
>  		xprt_clear_connecting(xprt);
> -		current->flags &= ~PF_FSTRANS;
> +		current->flags &= ~(PF_FSTRANS | PF_MEMALLOC_NOIO);
>  		return;
>  	case -EINVAL:
>  		/* Happens, for instance, if the user specified a link
> @@ -2294,7 +2295,7 @@ out_eagain:
>  out:
>  	xprt_clear_connecting(xprt);
>  	xprt_wake_pending_tasks(xprt, status);
> -	current->flags &= ~PF_FSTRANS;
> +	current->flags &= ~(PF_FSTRANS | PF_MEMALLOC_NOIO);
>  }
>  
>  /**
> 

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