diff mbox

[5/9] IB/core: add a simple MR pool

Message ID 1456784410-20166-6-git-send-email-hch@lst.de (mailing list archive)
State Superseded
Headers show

Commit Message

Christoph Hellwig Feb. 29, 2016, 10:20 p.m. UTC 
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/infiniband/core/Makefile  |  2 +-
 drivers/infiniband/core/mr_pool.c | 84 +++++++++++++++++++++++++++++++++++++++
 drivers/infiniband/core/verbs.c   |  5 +++
 include/rdma/ib_verbs.h           |  9 ++++-
 include/rdma/mr_pool.h            | 25 ++++++++++++
 5 files changed, 123 insertions(+), 2 deletions(-)
 create mode 100644 drivers/infiniband/core/mr_pool.c
 create mode 100644 include/rdma/mr_pool.h

Comments

Bart Van Assche Feb. 29, 2016, 10:36 p.m. UTC | #1 
On 02/29/2016 02:20 PM, Christoph Hellwig wrote:
> +struct ib_mr *ib_mr_pool_get(struct ib_qp *qp, struct list_head *list)
> +{
> +	struct ib_mr *mr = NULL;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&qp->mr_lock, flags);
> +	mr = list_first_entry_or_null(list, struct ib_mr, qp_entry);
> +	if (mr)
> +		qp->mrs_used++;
> +	spin_unlock_irqrestore(&qp->mr_lock, flags);
> +
> +	return mr;
> +}
> +EXPORT_SYMBOL(ib_mr_pool_get);
> +
> +void ib_mr_pool_put(struct ib_qp *qp, struct list_head *list, struct ib_mr *mr)
> +{
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&qp->mr_lock, flags);
> +	list_add(&mr->qp_entry, list);
> +	qp->mrs_used--;
> +	spin_unlock_irqrestore(&qp->mr_lock, flags);
> +}
> +EXPORT_SYMBOL(ib_mr_pool_put);

Hi Christoph,

So ib_mr_pool_get() does not remove the returned element from the list 
and ib_mr_pool_put() adds it to the list? Why this asymmetry?

Thanks,

Bart.
--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Christoph Hellwig March 1, 2016, 6:48 a.m. UTC | #2 
On Mon, Feb 29, 2016 at 02:36:53PM -0800, Bart Van Assche wrote:
> So ib_mr_pool_get() does not remove the returned element from the list and 
> ib_mr_pool_put() adds it to the list? Why this asymmetry?

It should removed it.  I already fixed this up twice after testing,
not sure why this sneaked back in..
--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Bart Van Assche March 1, 2016, 7:12 p.m. UTC | #3 
On 02/29/2016 02:20 PM, Christoph Hellwig wrote:
> +int ib_mr_pool_init(struct ib_qp *qp, struct list_head *list, int nr,
> +		enum ib_mr_type type, u32 max_num_sg)
> +{
> +	struct ib_mr *mr;
> +	unsigned long flags;
> +	int ret, i;
> +
> +	for (i = 0; i < nr; i++) {
> +		mr = ib_alloc_mr(qp->pd, type, max_num_sg);
> +		if (IS_ERR(mr)) {
> +			ret = PTR_ERR(mr);
> +			goto out;
> +		}
> +
> +		spin_lock_irqsave(&qp->mr_lock, flags);
> +		list_add_tail(&mr->qp_entry, list);
> +		spin_unlock_irqrestore(&qp->mr_lock, flags);
> +	}
> +
> +	return 0;
> +out:
> +	ib_mr_pool_destroy(qp, list);
> +	return ret;
> +}
> +EXPORT_SYMBOL(ib_mr_pool_init);
> +
> +void ib_mr_pool_destroy(struct ib_qp *qp, struct list_head *list)
> +{
> +	struct ib_mr *mr;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&qp->mr_lock, flags);
> +	while (!list_empty(list)) {
> +		mr = list_first_entry(list, struct ib_mr, qp_entry);
> +		list_del(&mr->qp_entry);
> +
> +		spin_unlock_irqrestore(&qp->mr_lock, flags);
> +		ib_dereg_mr(mr);
> +		spin_lock_irqsave(&qp->mr_lock, flags);
> +	}
> +	spin_unlock_irqrestore(&qp->mr_lock, flags);
> +}
> +EXPORT_SYMBOL(ib_mr_pool_destroy);

Hello Christoph,

A second question about this patch: why do we need locking in 
ib_mr_pool_init() and ib_mr_pool_destroy()? Calling ib_mr_pool_get() or 
ib_mr_pool_put() while one of these two functions is in progress is a 
bug (race condition). Can the locking be left out from these two functions?

Bart.
--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Christoph Hellwig March 2, 2016, 9:14 a.m. UTC | #4 
On Tue, Mar 01, 2016 at 11:12:09AM -0800, Bart Van Assche wrote:
> A second question about this patch: why do we need locking in 
> ib_mr_pool_init() and ib_mr_pool_destroy()? Calling ib_mr_pool_get() or 
> ib_mr_pool_put() while one of these two functions is in progress is a bug 
> (race condition). Can the locking be left out from these two functions?

Maybe.  But then we'd need to use barrier to ensure no reordering ever
happens.  Just using the lock in the this slow path as well makes that
a lot easier.
--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
diff mbox

Patch

diff --git a/drivers/infiniband/core/Makefile b/drivers/infiniband/core/Makefile
index f818538..48bd9d8 100644
--- a/drivers/infiniband/core/Makefile
+++ b/drivers/infiniband/core/Makefile
@@ -10,7 +10,7 @@  obj-$(CONFIG_INFINIBAND_USER_ACCESS) +=	ib_uverbs.o ib_ucm.o \
 
 ib_core-y :=			packer.o ud_header.o verbs.o cq.o sysfs.o \
 				device.o fmr_pool.o cache.o netlink.o \
-				roce_gid_mgmt.o
+				roce_gid_mgmt.o mr_pool.o
 ib_core-$(CONFIG_INFINIBAND_USER_MEM) += umem.o
 ib_core-$(CONFIG_INFINIBAND_ON_DEMAND_PAGING) += umem_odp.o umem_rbtree.o
 
diff --git a/drivers/infiniband/core/mr_pool.c b/drivers/infiniband/core/mr_pool.c
new file mode 100644
index 0000000..b1eb27a
--- /dev/null
+++ b/drivers/infiniband/core/mr_pool.c
@@ -0,0 +1,84 @@ 
+/*
+ * Copyright (c) 2016 HGST, a Western Digital Company.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+#include <rdma/ib_verbs.h>
+#include <rdma/mr_pool.h>
+
+struct ib_mr *ib_mr_pool_get(struct ib_qp *qp, struct list_head *list)
+{
+	struct ib_mr *mr = NULL;
+	unsigned long flags;
+
+	spin_lock_irqsave(&qp->mr_lock, flags);
+	mr = list_first_entry_or_null(list, struct ib_mr, qp_entry);
+	if (mr)
+		qp->mrs_used++;
+	spin_unlock_irqrestore(&qp->mr_lock, flags);
+
+	return mr;
+}
+EXPORT_SYMBOL(ib_mr_pool_get);
+
+void ib_mr_pool_put(struct ib_qp *qp, struct list_head *list, struct ib_mr *mr)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&qp->mr_lock, flags);
+	list_add(&mr->qp_entry, list);
+	qp->mrs_used--;
+	spin_unlock_irqrestore(&qp->mr_lock, flags);
+}
+EXPORT_SYMBOL(ib_mr_pool_put);
+
+int ib_mr_pool_init(struct ib_qp *qp, struct list_head *list, int nr,
+		enum ib_mr_type type, u32 max_num_sg)
+{
+	struct ib_mr *mr;
+	unsigned long flags;
+	int ret, i;
+
+	for (i = 0; i < nr; i++) {
+		mr = ib_alloc_mr(qp->pd, type, max_num_sg);
+		if (IS_ERR(mr)) {
+			ret = PTR_ERR(mr);
+			goto out;
+		}
+
+		spin_lock_irqsave(&qp->mr_lock, flags);
+		list_add_tail(&mr->qp_entry, list);
+		spin_unlock_irqrestore(&qp->mr_lock, flags);
+	}
+
+	return 0;
+out:
+	ib_mr_pool_destroy(qp, list);
+	return ret;
+}
+EXPORT_SYMBOL(ib_mr_pool_init);
+
+void ib_mr_pool_destroy(struct ib_qp *qp, struct list_head *list)
+{
+	struct ib_mr *mr;
+	unsigned long flags;
+
+	spin_lock_irqsave(&qp->mr_lock, flags);
+	while (!list_empty(list)) {
+		mr = list_first_entry(list, struct ib_mr, qp_entry);
+		list_del(&mr->qp_entry);
+
+		spin_unlock_irqrestore(&qp->mr_lock, flags);
+		ib_dereg_mr(mr);
+		spin_lock_irqsave(&qp->mr_lock, flags);
+	}
+	spin_unlock_irqrestore(&qp->mr_lock, flags);
+}
+EXPORT_SYMBOL(ib_mr_pool_destroy);
diff --git a/drivers/infiniband/core/verbs.c b/drivers/infiniband/core/verbs.c
index 662466f..20bb5d1 100644
--- a/drivers/infiniband/core/verbs.c
+++ b/drivers/infiniband/core/verbs.c
@@ -762,6 +762,9 @@  struct ib_qp *ib_create_qp(struct ib_pd *pd,
 	qp->qp_type    = qp_init_attr->qp_type;
 
 	atomic_set(&qp->usecnt, 0);
+	qp->mrs_used = 0;
+	spin_lock_init(&qp->mr_lock);
+
 	if (qp_init_attr->qp_type == IB_QPT_XRC_TGT)
 		return ib_create_xrc_qp(qp, qp_init_attr);
 
@@ -1255,6 +1258,8 @@  int ib_destroy_qp(struct ib_qp *qp)
 	struct ib_srq *srq;
 	int ret;
 
+	WARN_ON_ONCE(qp->mrs_used > 0);
+
 	if (atomic_read(&qp->usecnt))
 		return -EBUSY;
 
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 267f11e..1e68dae 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -1408,6 +1408,10 @@  struct ib_qp {
 	struct ib_srq	       *srq;
 	struct ib_xrcd	       *xrcd; /* XRC TGT QPs only */
 	struct list_head	xrcd_list;
+
+	spinlock_t		mr_lock;
+	int			mrs_used;
+
 	/* count times opened, mcast attaches, flow attaches */
 	atomic_t		usecnt;
 	struct list_head	open_list;
@@ -1422,12 +1426,15 @@  struct ib_qp {
 struct ib_mr {
 	struct ib_device  *device;
 	struct ib_pd	  *pd;
-	struct ib_uobject *uobject;
 	u32		   lkey;
 	u32		   rkey;
 	u64		   iova;
 	u32		   length;
 	unsigned int	   page_size;
+	union {
+		struct ib_uobject	*uobject;	/* user */
+		struct list_head	qp_entry;	/* FR */
+	};
 };
 
 struct ib_mw {
diff --git a/include/rdma/mr_pool.h b/include/rdma/mr_pool.h
new file mode 100644
index 0000000..986010b
--- /dev/null
+++ b/include/rdma/mr_pool.h
@@ -0,0 +1,25 @@ 
+/*
+ * Copyright (c) 2016 HGST, a Western Digital Company.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+#ifndef _RDMA_MR_POOL_H
+#define _RDMA_MR_POOL_H 1
+
+#include <rdma/ib_verbs.h>
+
+struct ib_mr *ib_mr_pool_get(struct ib_qp *qp, struct list_head *list);
+void ib_mr_pool_put(struct ib_qp *qp, struct list_head *list, struct ib_mr *mr);
+
+int ib_mr_pool_init(struct ib_qp *qp, struct list_head *list, int nr,
+		enum ib_mr_type type, u32 max_num_sg);
+void ib_mr_pool_destroy(struct ib_qp *qp, struct list_head *list);
+
+#endif /* _RDMA_MR_POOL_H */