[1/3] SUNRPC: The TCP back channel mustn't disappear while requests are outstanding
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Message ID 20191016141546.32277-1-trond.myklebust@hammerspace.com
State New
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Series
  • [1/3] SUNRPC: The TCP back channel mustn't disappear while requests are outstanding
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Commit Message

Trond Myklebust Oct. 16, 2019, 2:15 p.m. UTC
If there are TCP back channel requests either being processed by the
server threads, then we should hold a reference to the transport
to ensure it doesn't get freed from underneath us.

Reported-by: Neil Brown <neilb@suse.de>
Fixes: 2ea24497a1b3 ("SUNRPC: RPC callbacks may be split across several..")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 net/sunrpc/backchannel_rqst.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Comments

J. Bruce Fields Oct. 16, 2019, 9:38 p.m. UTC | #1
These make sense to me.  (But I'll confess I haven't been following the
back and forth with Neil.)

On Wed, Oct 16, 2019 at 10:15:44AM -0400, Trond Myklebust wrote:
> If there are TCP back channel requests either being processed by the

In this patch and the next, is the "either" unnecessary, or was there
some other condition you meant to mention?

--b.

> server threads, then we should hold a reference to the transport
> to ensure it doesn't get freed from underneath us.
> 
> Reported-by: Neil Brown <neilb@suse.de>
> Fixes: 2ea24497a1b3 ("SUNRPC: RPC callbacks may be split across several..")
> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
> ---
>  net/sunrpc/backchannel_rqst.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sunrpc/backchannel_rqst.c b/net/sunrpc/backchannel_rqst.c
> index 339e8c077c2d..7eb251372f94 100644
> --- a/net/sunrpc/backchannel_rqst.c
> +++ b/net/sunrpc/backchannel_rqst.c
> @@ -307,8 +307,8 @@ void xprt_free_bc_rqst(struct rpc_rqst *req)
>  		 */
>  		dprintk("RPC:       Last session removed req=%p\n", req);
>  		xprt_free_allocation(req);
> -		return;
>  	}
> +	xprt_put(xprt);
>  }
>  
>  /*
> @@ -339,7 +339,7 @@ struct rpc_rqst *xprt_lookup_bc_request(struct rpc_xprt *xprt, __be32 xid)
>  		spin_unlock(&xprt->bc_pa_lock);
>  		if (new) {
>  			if (req != new)
> -				xprt_free_bc_rqst(new);
> +				xprt_free_allocation(new);
>  			break;
>  		} else if (req)
>  			break;
> @@ -368,6 +368,7 @@ void xprt_complete_bc_request(struct rpc_rqst *req, uint32_t copied)
>  	set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
>  
>  	dprintk("RPC:       add callback request to list\n");
> +	xprt_get(xprt);
>  	spin_lock(&bc_serv->sv_cb_lock);
>  	list_add(&req->rq_bc_list, &bc_serv->sv_cb_list);
>  	wake_up(&bc_serv->sv_cb_waitq);
> -- 
> 2.21.0
>
NeilBrown Oct. 16, 2019, 10:24 p.m. UTC | #2
On Wed, Oct 16 2019, Trond Myklebust wrote:

> If there are TCP back channel requests either being processed by the
> server threads, then we should hold a reference to the transport
> to ensure it doesn't get freed from underneath us.
>
> Reported-by: Neil Brown <neilb@suse.de>
> Fixes: 2ea24497a1b3 ("SUNRPC: RPC callbacks may be split across several..")
> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
> ---
>  net/sunrpc/backchannel_rqst.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/net/sunrpc/backchannel_rqst.c b/net/sunrpc/backchannel_rqst.c
> index 339e8c077c2d..7eb251372f94 100644
> --- a/net/sunrpc/backchannel_rqst.c
> +++ b/net/sunrpc/backchannel_rqst.c
> @@ -307,8 +307,8 @@ void xprt_free_bc_rqst(struct rpc_rqst *req)
>  		 */
>  		dprintk("RPC:       Last session removed req=%p\n", req);
>  		xprt_free_allocation(req);
> -		return;
>  	}
> +	xprt_put(xprt);
>  }
>  
>  /*
> @@ -339,7 +339,7 @@ struct rpc_rqst *xprt_lookup_bc_request(struct rpc_xprt *xprt, __be32 xid)
>  		spin_unlock(&xprt->bc_pa_lock);
>  		if (new) {
>  			if (req != new)
> -				xprt_free_bc_rqst(new);
> +				xprt_free_allocation(new);
>  			break;
>  		} else if (req)
>  			break;
> @@ -368,6 +368,7 @@ void xprt_complete_bc_request(struct rpc_rqst *req, uint32_t copied)
>  	set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
>  
>  	dprintk("RPC:       add callback request to list\n");
> +	xprt_get(xprt);
>  	spin_lock(&bc_serv->sv_cb_lock);
>  	list_add(&req->rq_bc_list, &bc_serv->sv_cb_list);
>  	wake_up(&bc_serv->sv_cb_waitq);
> -- 
> 2.21.0

Looks good.
This and the next two:
 Reviewed-by: NeilBrown <neilb@suse.de>

It would help me if you could add a Fixes: tag to at least the first
two.

BTW, while reviewing I notices that bc_alloc_count and bc_slot_count are
almost identical.  The three places were that are changed separately are
probably (minor) bugs.
Do you recall why there were two different counters?  Has the reason
disappeared?

Thanks,
NeilBrown
Trond Myklebust Oct. 17, 2019, 12:43 p.m. UTC | #3
On Thu, 2019-10-17 at 09:24 +1100, NeilBrown wrote:
> On Wed, Oct 16 2019, Trond Myklebust wrote:
> 
> > If there are TCP back channel requests either being processed by
> > the
> > server threads, then we should hold a reference to the transport
> > to ensure it doesn't get freed from underneath us.
> > 
> > Reported-by: Neil Brown <neilb@suse.de>
> > Fixes: 2ea24497a1b3 ("SUNRPC: RPC callbacks may be split across
> > several..")
> > Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
> > ---
> >  net/sunrpc/backchannel_rqst.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/net/sunrpc/backchannel_rqst.c
> > b/net/sunrpc/backchannel_rqst.c
> > index 339e8c077c2d..7eb251372f94 100644
> > --- a/net/sunrpc/backchannel_rqst.c
> > +++ b/net/sunrpc/backchannel_rqst.c
> > @@ -307,8 +307,8 @@ void xprt_free_bc_rqst(struct rpc_rqst *req)
> >  		 */
> >  		dprintk("RPC:       Last session removed req=%p\n",
> > req);
> >  		xprt_free_allocation(req);
> > -		return;
> >  	}
> > +	xprt_put(xprt);
> >  }
> >  
> >  /*
> > @@ -339,7 +339,7 @@ struct rpc_rqst *xprt_lookup_bc_request(struct
> > rpc_xprt *xprt, __be32 xid)
> >  		spin_unlock(&xprt->bc_pa_lock);
> >  		if (new) {
> >  			if (req != new)
> > -				xprt_free_bc_rqst(new);
> > +				xprt_free_allocation(new);
> >  			break;
> >  		} else if (req)
> >  			break;
> > @@ -368,6 +368,7 @@ void xprt_complete_bc_request(struct rpc_rqst
> > *req, uint32_t copied)
> >  	set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
> >  
> >  	dprintk("RPC:       add callback request to list\n");
> > +	xprt_get(xprt);
> >  	spin_lock(&bc_serv->sv_cb_lock);
> >  	list_add(&req->rq_bc_list, &bc_serv->sv_cb_list);
> >  	wake_up(&bc_serv->sv_cb_waitq);
> > -- 
> > 2.21.0
> 
> Looks good.
> This and the next two:
>  Reviewed-by: NeilBrown <neilb@suse.de>
> 
> It would help me if you could add a Fixes: tag to at least the first
> two.

Neither have Cc:stable, but they both already have Fixes: tags. See
above.

> 
> BTW, while reviewing I notices that bc_alloc_count and bc_slot_count
> are
> almost identical.  The three places were that are changed separately
> are
> probably (minor) bugs.
> Do you recall why there were two different counters?  Has the reason
> disappeared?

IIRC, the former contains the count of preallocated slots, and the
latter the count of preallocated+dynamic slots.

Thanks
  Trond

Patch
diff mbox series

diff --git a/net/sunrpc/backchannel_rqst.c b/net/sunrpc/backchannel_rqst.c
index 339e8c077c2d..7eb251372f94 100644
--- a/net/sunrpc/backchannel_rqst.c
+++ b/net/sunrpc/backchannel_rqst.c
@@ -307,8 +307,8 @@  void xprt_free_bc_rqst(struct rpc_rqst *req)
 		 */
 		dprintk("RPC:       Last session removed req=%p\n", req);
 		xprt_free_allocation(req);
-		return;
 	}
+	xprt_put(xprt);
 }
 
 /*
@@ -339,7 +339,7 @@  struct rpc_rqst *xprt_lookup_bc_request(struct rpc_xprt *xprt, __be32 xid)
 		spin_unlock(&xprt->bc_pa_lock);
 		if (new) {
 			if (req != new)
-				xprt_free_bc_rqst(new);
+				xprt_free_allocation(new);
 			break;
 		} else if (req)
 			break;
@@ -368,6 +368,7 @@  void xprt_complete_bc_request(struct rpc_rqst *req, uint32_t copied)
 	set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
 
 	dprintk("RPC:       add callback request to list\n");
+	xprt_get(xprt);
 	spin_lock(&bc_serv->sv_cb_lock);
 	list_add(&req->rq_bc_list, &bc_serv->sv_cb_list);
 	wake_up(&bc_serv->sv_cb_waitq);