diff mbox

[v1,10/13] xprtrdma: Release FRMR segment buffers during LOCAL_INV completion

Message ID 20140623224023.1634.67233.stgit@manet.1015granger.net (mailing list archive)
State Not Applicable
Headers show

Commit Message

Chuck Lever June 23, 2014, 10:40 p.m. UTC 
FRMR uses a LOCAL_INV Work Request, which is asynchronous, to
deregister segment buffers.  Other registration strategies use
synchronous deregistration mechanisms (like ib_unmap_fmr()).

For a synchronous deregistration mechanism, it makes sense for
xprt_rdma_free() to put segment buffers back into the buffer pool
immediately once rpcrdma_deregister_external() returns.

This is currently also what FRMR is doing. It is releasing segment
buffers just after the LOCAL_INV WR is posted.

But segment buffers need to be put back after the LOCAL_INV WR
_completes_ (or flushes). Otherwise, rpcrdma_buffer_get() can then
assign these segment buffers to another RPC task while they are
still "in use" by the hardware.

The result of re-using an FRMR too quickly is that it's rkey
no longer matches the rkey that was registered with the provider.
This results in FAST_REG_MR or LOCAL_INV Work Requests completing
with IB_WC_MW_BIND_ERR, and the FRMR, and thus the transport,
becomes unusable.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 net/sunrpc/xprtrdma/verbs.c     |   44 +++++++++++++++++++++++++++++++++++----
 net/sunrpc/xprtrdma/xprt_rdma.h |    2 ++
 2 files changed, 42 insertions(+), 4 deletions(-)


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Comments

Shirley Ma June 25, 2014, 5:17 a.m. UTC | #1 
Would it be possible to delay rpcrdma_buffer_put() until LOCAL_INV request send completion? remove rpcrdma_buffer_put() from xprt_rdma_free(), add a call back after LOCAL_INV completed?

Shirley

On 06/23/2014 03:40 PM, Chuck Lever wrote:
> FRMR uses a LOCAL_INV Work Request, which is asynchronous, to
> deregister segment buffers.  Other registration strategies use
> synchronous deregistration mechanisms (like ib_unmap_fmr()).
> 
> For a synchronous deregistration mechanism, it makes sense for
> xprt_rdma_free() to put segment buffers back into the buffer pool
> immediately once rpcrdma_deregister_external() returns.
> 
> This is currently also what FRMR is doing. It is releasing segment
> buffers just after the LOCAL_INV WR is posted.
> 
> But segment buffers need to be put back after the LOCAL_INV WR
> _completes_ (or flushes). Otherwise, rpcrdma_buffer_get() can then
> assign these segment buffers to another RPC task while they are
> still "in use" by the hardware.
> 
> The result of re-using an FRMR too quickly is that it's rkey
> no longer matches the rkey that was registered with the provider.
> This results in FAST_REG_MR or LOCAL_INV Work Requests completing
> with IB_WC_MW_BIND_ERR, and the FRMR, and thus the transport,
> becomes unusable.
> 
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
>  net/sunrpc/xprtrdma/verbs.c     |   44 +++++++++++++++++++++++++++++++++++----
>  net/sunrpc/xprtrdma/xprt_rdma.h |    2 ++
>  2 files changed, 42 insertions(+), 4 deletions(-)
> 
> diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
> index f24f0bf..52f57f7 100644
> --- a/net/sunrpc/xprtrdma/verbs.c
> +++ b/net/sunrpc/xprtrdma/verbs.c
> @@ -62,6 +62,8 @@
>  #endif
>  
>  static void rpcrdma_decrement_frmr_rkey(struct rpcrdma_mw *);
> +static void rpcrdma_get_mw(struct rpcrdma_mw *);
> +static void rpcrdma_put_mw(struct rpcrdma_mw *);
>  
>  /*
>   * internal functions
> @@ -167,6 +169,7 @@ rpcrdma_sendcq_process_wc(struct ib_wc *wc)
>  		if (fastreg)
>  			rpcrdma_decrement_frmr_rkey(mw);
>  	}
> +	rpcrdma_put_mw(mw);
>  }
>  
>  static int
> @@ -1034,7 +1037,7 @@ rpcrdma_buffer_create(struct rpcrdma_buffer *buf, struct rpcrdma_ep *ep,
>  	len += cdata->padding;
>  	switch (ia->ri_memreg_strategy) {
>  	case RPCRDMA_FRMR:
> -		len += buf->rb_max_requests * RPCRDMA_MAX_SEGS *
> +		len += (buf->rb_max_requests + 1) * RPCRDMA_MAX_SEGS *
>  				sizeof(struct rpcrdma_mw);
>  		break;
>  	case RPCRDMA_MTHCAFMR:
> @@ -1076,7 +1079,7 @@ rpcrdma_buffer_create(struct rpcrdma_buffer *buf, struct rpcrdma_ep *ep,
>  	r = (struct rpcrdma_mw *)p;
>  	switch (ia->ri_memreg_strategy) {
>  	case RPCRDMA_FRMR:
> -		for (i = buf->rb_max_requests * RPCRDMA_MAX_SEGS; i; i--) {
> +		for (i = (buf->rb_max_requests+1) * RPCRDMA_MAX_SEGS; i; i--) {
>  			r->r.frmr.fr_mr = ib_alloc_fast_reg_mr(ia->ri_pd,
>  						ia->ri_max_frmr_depth);
>  			if (IS_ERR(r->r.frmr.fr_mr)) {
> @@ -1252,12 +1255,36 @@ rpcrdma_buffer_destroy(struct rpcrdma_buffer *buf)
>  }
>  
>  static void
> -rpcrdma_put_mw_locked(struct rpcrdma_mw *mw)
> +rpcrdma_free_mw(struct kref *kref)
>  {
> +	struct rpcrdma_mw *mw = container_of(kref, struct rpcrdma_mw, mw_ref);
>  	list_add_tail(&mw->mw_list, &mw->mw_pool->rb_mws);
>  }
>  
>  static void
> +rpcrdma_put_mw_locked(struct rpcrdma_mw *mw)
> +{
> +	kref_put(&mw->mw_ref, rpcrdma_free_mw);
> +}
> +
> +static void
> +rpcrdma_get_mw(struct rpcrdma_mw *mw)
> +{
> +	kref_get(&mw->mw_ref);
> +}
> +
> +static void
> +rpcrdma_put_mw(struct rpcrdma_mw *mw)
> +{
> +	struct rpcrdma_buffer *buffers = mw->mw_pool;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&buffers->rb_lock, flags);
> +	rpcrdma_put_mw_locked(mw);
> +	spin_unlock_irqrestore(&buffers->rb_lock, flags);
> +}
> +
> +static void
>  rpcrdma_buffer_put_mw(struct rpcrdma_mw **mw)
>  {
>  	rpcrdma_put_mw_locked(*mw);
> @@ -1304,6 +1331,7 @@ rpcrdma_buffer_get_mws(struct rpcrdma_req *req, struct rpcrdma_buffer *buffers)
>  		r = list_entry(buffers->rb_mws.next,
>  				struct rpcrdma_mw, mw_list);
>  		list_del(&r->mw_list);
> +		kref_init(&r->mw_ref);
>  		r->mw_pool = buffers;
>  		req->rl_segments[i].mr_chunk.rl_mw = r;
>  	}
> @@ -1583,6 +1611,7 @@ rpcrdma_register_frmr_external(struct rpcrdma_mr_seg *seg,
>  	dprintk("RPC:       %s: Using frmr %p to map %d segments\n",
>  		__func__, seg1->mr_chunk.rl_mw, i);
>  
> +	rpcrdma_get_mw(seg1->mr_chunk.rl_mw);
>  	if (unlikely(seg1->mr_chunk.rl_mw->r.frmr.fr_state == FRMR_IS_VALID)) {
>  		dprintk("RPC:       %s: frmr %x left valid, posting invalidate.\n",
>  			__func__,
> @@ -1595,6 +1624,7 @@ rpcrdma_register_frmr_external(struct rpcrdma_mr_seg *seg,
>  		invalidate_wr.send_flags = IB_SEND_SIGNALED;
>  		invalidate_wr.ex.invalidate_rkey =
>  			seg1->mr_chunk.rl_mw->r.frmr.fr_mr->rkey;
> +		rpcrdma_get_mw(seg1->mr_chunk.rl_mw);
>  		DECR_CQCOUNT(&r_xprt->rx_ep);
>  		post_wr = &invalidate_wr;
>  	} else
> @@ -1638,6 +1668,9 @@ rpcrdma_register_frmr_external(struct rpcrdma_mr_seg *seg,
>  	*nsegs = i;
>  	return 0;
>  out_err:
> +	rpcrdma_put_mw(seg1->mr_chunk.rl_mw);
> +	if (post_wr == &invalidate_wr)
> +		rpcrdma_put_mw(seg1->mr_chunk.rl_mw);
>  	while (i--)
>  		rpcrdma_unmap_one(ia, --seg);
>  	return rc;
> @@ -1653,6 +1686,7 @@ rpcrdma_deregister_frmr_external(struct rpcrdma_mr_seg *seg,
>  
>  	while (seg1->mr_nsegs--)
>  		rpcrdma_unmap_one(ia, seg++);
> +	rpcrdma_get_mw(seg1->mr_chunk.rl_mw);
>  
>  	memset(&invalidate_wr, 0, sizeof invalidate_wr);
>  	invalidate_wr.wr_id = (unsigned long)(void *)seg1->mr_chunk.rl_mw;
> @@ -1664,9 +1698,11 @@ rpcrdma_deregister_frmr_external(struct rpcrdma_mr_seg *seg,
>  	read_lock(&ia->ri_qplock);
>  	rc = ib_post_send(ia->ri_id->qp, &invalidate_wr, &bad_wr);
>  	read_unlock(&ia->ri_qplock);
> -	if (rc)
> +	if (rc) {
> +		rpcrdma_put_mw(seg1->mr_chunk.rl_mw);
>  		dprintk("RPC:       %s: failed ib_post_send for invalidate,"
>  			" status %i\n", __func__, rc);
> +	}
>  	return rc;
>  }
>  
> diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
> index b81e5b5..7a140fe 100644
> --- a/net/sunrpc/xprtrdma/xprt_rdma.h
> +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
> @@ -44,6 +44,7 @@
>  #include <linux/spinlock.h> 		/* spinlock_t, etc */
>  #include <linux/atomic.h>			/* atomic_t, etc */
>  #include <linux/workqueue.h>		/* struct work_struct */
> +#include <linux/kref.h>
>  
>  #include <rdma/rdma_cm.h>		/* RDMA connection api */
>  #include <rdma/ib_verbs.h>		/* RDMA verbs api */
> @@ -176,6 +177,7 @@ struct rpcrdma_mw {
>  	} r;
>  	struct list_head	mw_list;
>  	struct rpcrdma_buffer	*mw_pool;
> +	struct kref		mw_ref;
>  };
>  
>  #define RPCRDMA_BIT_FASTREG		(0)
> 
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Chuck Lever June 25, 2014, 2:32 p.m. UTC | #2 
Hi Shirley-

On Jun 25, 2014, at 1:17 AM, Shirley Ma <shirley.ma@oracle.com> wrote:

> Would it be possible to delay rpcrdma_buffer_put() until LOCAL_INV request send completion? remove rpcrdma_buffer_put() from xprt_rdma_free(), add a call back after LOCAL_INV completed?

That’s exactly what this patch does. The relevant part of
rpcrdma_buffer_put() is:

  list_add(&mw->mw_list, &buf->rb_mws);

This is now wrapped with a reference count so that
rpcrdma_buffer_put() and the LOCAL_INV completion can run in any
order. The FRMR is added back to the list only after both of those
two have finished.

Nothing in xprt_rdma_free() is allowed to sleep, so we can’t wait for
LOCAL_INV completion in there.

The only alternative I can think of is having rpcrdma_buffer_get() check
fr_state as it removes FRMRs from the rb_mws list. Only if the FRMR is
marked FRMR_IS_INVALID, rpcrdma_buffer_get() will add it to the
rpcrdma_req.

--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com



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Shirley Ma June 25, 2014, 4:14 p.m. UTC | #3 
On 06/25/2014 07:32 AM, Chuck Lever wrote:
> Hi Shirley-
> 
> On Jun 25, 2014, at 1:17 AM, Shirley Ma <shirley.ma@oracle.com> wrote:
> 
>> Would it be possible to delay rpcrdma_buffer_put() until LOCAL_INV request send completion? remove rpcrdma_buffer_put() from xprt_rdma_free(), add a call back after LOCAL_INV completed?
> 
> That’s exactly what this patch does. The relevant part of
> rpcrdma_buffer_put() is:
> 
>   list_add(&mw->mw_list, &buf->rb_mws);
> 
> This is now wrapped with a reference count so that
> rpcrdma_buffer_put() and the LOCAL_INV completion can run in any
> order. The FRMR is added back to the list only after both of those
> two have finished.

What I was thinking is to run rpcrdma_buffer_put after LOCAL_INV completion without reference count.
 
> Nothing in xprt_rdma_free() is allowed to sleep, so we can’t wait for
> LOCAL_INV completion in there.
> 
> The only alternative I can think of is having rpcrdma_buffer_get() check
> fr_state as it removes FRMRs from the rb_mws list. Only if the FRMR is
> marked FRMR_IS_INVALID, rpcrdma_buffer_get() will add it to the
> rpcrdma_req.

I thought about it too, an atomic operation would be better than a lock.

> --
> Chuck Lever
> chuck[dot]lever[at]oracle[dot]com
> 
> 
> 
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diff mbox

Patch

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index f24f0bf..52f57f7 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -62,6 +62,8 @@ 
 #endif
 
 static void rpcrdma_decrement_frmr_rkey(struct rpcrdma_mw *);
+static void rpcrdma_get_mw(struct rpcrdma_mw *);
+static void rpcrdma_put_mw(struct rpcrdma_mw *);
 
 /*
  * internal functions
@@ -167,6 +169,7 @@  rpcrdma_sendcq_process_wc(struct ib_wc *wc)
 		if (fastreg)
 			rpcrdma_decrement_frmr_rkey(mw);
 	}
+	rpcrdma_put_mw(mw);
 }
 
 static int
@@ -1034,7 +1037,7 @@  rpcrdma_buffer_create(struct rpcrdma_buffer *buf, struct rpcrdma_ep *ep,
 	len += cdata->padding;
 	switch (ia->ri_memreg_strategy) {
 	case RPCRDMA_FRMR:
-		len += buf->rb_max_requests * RPCRDMA_MAX_SEGS *
+		len += (buf->rb_max_requests + 1) * RPCRDMA_MAX_SEGS *
 				sizeof(struct rpcrdma_mw);
 		break;
 	case RPCRDMA_MTHCAFMR:
@@ -1076,7 +1079,7 @@  rpcrdma_buffer_create(struct rpcrdma_buffer *buf, struct rpcrdma_ep *ep,
 	r = (struct rpcrdma_mw *)p;
 	switch (ia->ri_memreg_strategy) {
 	case RPCRDMA_FRMR:
-		for (i = buf->rb_max_requests * RPCRDMA_MAX_SEGS; i; i--) {
+		for (i = (buf->rb_max_requests+1) * RPCRDMA_MAX_SEGS; i; i--) {
 			r->r.frmr.fr_mr = ib_alloc_fast_reg_mr(ia->ri_pd,
 						ia->ri_max_frmr_depth);
 			if (IS_ERR(r->r.frmr.fr_mr)) {
@@ -1252,12 +1255,36 @@  rpcrdma_buffer_destroy(struct rpcrdma_buffer *buf)
 }
 
 static void
-rpcrdma_put_mw_locked(struct rpcrdma_mw *mw)
+rpcrdma_free_mw(struct kref *kref)
 {
+	struct rpcrdma_mw *mw = container_of(kref, struct rpcrdma_mw, mw_ref);
 	list_add_tail(&mw->mw_list, &mw->mw_pool->rb_mws);
 }
 
 static void
+rpcrdma_put_mw_locked(struct rpcrdma_mw *mw)
+{
+	kref_put(&mw->mw_ref, rpcrdma_free_mw);
+}
+
+static void
+rpcrdma_get_mw(struct rpcrdma_mw *mw)
+{
+	kref_get(&mw->mw_ref);
+}
+
+static void
+rpcrdma_put_mw(struct rpcrdma_mw *mw)
+{
+	struct rpcrdma_buffer *buffers = mw->mw_pool;
+	unsigned long flags;
+
+	spin_lock_irqsave(&buffers->rb_lock, flags);
+	rpcrdma_put_mw_locked(mw);
+	spin_unlock_irqrestore(&buffers->rb_lock, flags);
+}
+
+static void
 rpcrdma_buffer_put_mw(struct rpcrdma_mw **mw)
 {
 	rpcrdma_put_mw_locked(*mw);
@@ -1304,6 +1331,7 @@  rpcrdma_buffer_get_mws(struct rpcrdma_req *req, struct rpcrdma_buffer *buffers)
 		r = list_entry(buffers->rb_mws.next,
 				struct rpcrdma_mw, mw_list);
 		list_del(&r->mw_list);
+		kref_init(&r->mw_ref);
 		r->mw_pool = buffers;
 		req->rl_segments[i].mr_chunk.rl_mw = r;
 	}
@@ -1583,6 +1611,7 @@  rpcrdma_register_frmr_external(struct rpcrdma_mr_seg *seg,
 	dprintk("RPC:       %s: Using frmr %p to map %d segments\n",
 		__func__, seg1->mr_chunk.rl_mw, i);
 
+	rpcrdma_get_mw(seg1->mr_chunk.rl_mw);
 	if (unlikely(seg1->mr_chunk.rl_mw->r.frmr.fr_state == FRMR_IS_VALID)) {
 		dprintk("RPC:       %s: frmr %x left valid, posting invalidate.\n",
 			__func__,
@@ -1595,6 +1624,7 @@  rpcrdma_register_frmr_external(struct rpcrdma_mr_seg *seg,
 		invalidate_wr.send_flags = IB_SEND_SIGNALED;
 		invalidate_wr.ex.invalidate_rkey =
 			seg1->mr_chunk.rl_mw->r.frmr.fr_mr->rkey;
+		rpcrdma_get_mw(seg1->mr_chunk.rl_mw);
 		DECR_CQCOUNT(&r_xprt->rx_ep);
 		post_wr = &invalidate_wr;
 	} else
@@ -1638,6 +1668,9 @@  rpcrdma_register_frmr_external(struct rpcrdma_mr_seg *seg,
 	*nsegs = i;
 	return 0;
 out_err:
+	rpcrdma_put_mw(seg1->mr_chunk.rl_mw);
+	if (post_wr == &invalidate_wr)
+		rpcrdma_put_mw(seg1->mr_chunk.rl_mw);
 	while (i--)
 		rpcrdma_unmap_one(ia, --seg);
 	return rc;
@@ -1653,6 +1686,7 @@  rpcrdma_deregister_frmr_external(struct rpcrdma_mr_seg *seg,
 
 	while (seg1->mr_nsegs--)
 		rpcrdma_unmap_one(ia, seg++);
+	rpcrdma_get_mw(seg1->mr_chunk.rl_mw);
 
 	memset(&invalidate_wr, 0, sizeof invalidate_wr);
 	invalidate_wr.wr_id = (unsigned long)(void *)seg1->mr_chunk.rl_mw;
@@ -1664,9 +1698,11 @@  rpcrdma_deregister_frmr_external(struct rpcrdma_mr_seg *seg,
 	read_lock(&ia->ri_qplock);
 	rc = ib_post_send(ia->ri_id->qp, &invalidate_wr, &bad_wr);
 	read_unlock(&ia->ri_qplock);
-	if (rc)
+	if (rc) {
+		rpcrdma_put_mw(seg1->mr_chunk.rl_mw);
 		dprintk("RPC:       %s: failed ib_post_send for invalidate,"
 			" status %i\n", __func__, rc);
+	}
 	return rc;
 }
 
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index b81e5b5..7a140fe 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -44,6 +44,7 @@ 
 #include <linux/spinlock.h> 		/* spinlock_t, etc */
 #include <linux/atomic.h>			/* atomic_t, etc */
 #include <linux/workqueue.h>		/* struct work_struct */
+#include <linux/kref.h>
 
 #include <rdma/rdma_cm.h>		/* RDMA connection api */
 #include <rdma/ib_verbs.h>		/* RDMA verbs api */
@@ -176,6 +177,7 @@  struct rpcrdma_mw {
 	} r;
 	struct list_head	mw_list;
 	struct rpcrdma_buffer	*mw_pool;
+	struct kref		mw_ref;
 };
 
 #define RPCRDMA_BIT_FASTREG		(0)