IB/qib: RCU locking for MR validation
Profiling indicates that MR validation locking is expensive. The MR
table is largely read-only and is a suitable candidate for RCU locking.
The patch uses RCU locking during validation to eliminate one
lock/unlock during that validation.
Reviewed-by: Mike Heinz <michael.william.heinz@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
diff --git a/drivers/infiniband/hw/qib/qib_keys.c b/drivers/infiniband/hw/qib/qib_keys.c
index 8b5ee3a..970165b 100644
--- a/drivers/infiniband/hw/qib/qib_keys.c
+++ b/drivers/infiniband/hw/qib/qib_keys.c
@@ -40,8 +40,7 @@
*
* Returns 0 if successful, otherwise returns -errno.
*
- * Increments mr reference count and sets published
- * as required.
+ * Increments mr reference count as required.
*
* Sets the lkey field mr for non-dma regions.
*
@@ -60,10 +59,12 @@
/* special case for dma_mr lkey == 0 */
if (dma_region) {
- /* should the dma_mr be relative to the pd? */
- if (!dev->dma_mr) {
+ struct qib_mregion *tmr;
+
+ tmr = rcu_dereference(dev->dma_mr);
+ if (!tmr) {
qib_get_mr(mr);
- dev->dma_mr = mr;
+ rcu_assign_pointer(dev->dma_mr, mr);
mr->lkey_published = 1;
}
goto success;
@@ -93,7 +94,7 @@
rkt->gen++;
}
qib_get_mr(mr);
- rkt->table[r] = mr;
+ rcu_assign_pointer(rkt->table[r], mr);
mr->lkey_published = 1;
success:
spin_unlock_irqrestore(&rkt->lock, flags);
@@ -120,33 +121,30 @@
spin_lock_irqsave(&rkt->lock, flags);
if (!mr->lkey_published)
goto out;
- mr->lkey_published = 0;
-
-
- spin_lock_irqsave(&dev->lk_table.lock, flags);
- if (lkey == 0) {
- if (dev->dma_mr && dev->dma_mr == mr) {
- qib_put_mr(dev->dma_mr);
- dev->dma_mr = NULL;
- }
- } else {
+ if (lkey == 0)
+ rcu_assign_pointer(dev->dma_mr, NULL);
+ else {
r = lkey >> (32 - ib_qib_lkey_table_size);
- qib_put_mr(dev->dma_mr);
- rkt->table[r] = NULL;
+ rcu_assign_pointer(rkt->table[r], NULL);
}
+ qib_put_mr(mr);
+ mr->lkey_published = 0;
out:
- spin_unlock_irqrestore(&dev->lk_table.lock, flags);
+ spin_unlock_irqrestore(&rkt->lock, flags);
}
/**
* qib_lkey_ok - check IB SGE for validity and initialize
* @rkt: table containing lkey to check SGE against
+ * @pd: protection domain
* @isge: outgoing internal SGE
* @sge: SGE to check
* @acc: access flags
*
* Return 1 if valid and successful, otherwise returns 0.
*
+ * increments the reference count upon success
+ *
* Check the IB SGE for validity and initialize our internal version
* of it.
*/
@@ -156,24 +154,25 @@
struct qib_mregion *mr;
unsigned n, m;
size_t off;
- unsigned long flags;
/*
* We use LKEY == zero for kernel virtual addresses
* (see qib_get_dma_mr and qib_dma.c).
*/
- spin_lock_irqsave(&rkt->lock, flags);
+ rcu_read_lock();
if (sge->lkey == 0) {
struct qib_ibdev *dev = to_idev(pd->ibpd.device);
if (pd->user)
goto bail;
- if (!dev->dma_mr)
+ mr = rcu_dereference(dev->dma_mr);
+ if (!mr)
goto bail;
- qib_get_mr(dev->dma_mr);
- spin_unlock_irqrestore(&rkt->lock, flags);
+ if (unlikely(!atomic_inc_not_zero(&mr->refcount)))
+ goto bail;
+ rcu_read_unlock();
- isge->mr = dev->dma_mr;
+ isge->mr = mr;
isge->vaddr = (void *) sge->addr;
isge->length = sge->length;
isge->sge_length = sge->length;
@@ -181,18 +180,18 @@
isge->n = 0;
goto ok;
}
- mr = rkt->table[(sge->lkey >> (32 - ib_qib_lkey_table_size))];
- if (unlikely(mr == NULL || mr->lkey != sge->lkey ||
- mr->pd != &pd->ibpd))
+ mr = rcu_dereference(
+ rkt->table[(sge->lkey >> (32 - ib_qib_lkey_table_size))]);
+ if (unlikely(!mr || mr->lkey != sge->lkey || mr->pd != &pd->ibpd))
goto bail;
off = sge->addr - mr->user_base;
- if (unlikely(sge->addr < mr->user_base ||
- off + sge->length > mr->length ||
- (mr->access_flags & acc) != acc))
+ if (unlikely(sge->addr < mr->iova || off + sge->length > mr->length ||
+ (mr->access_flags & acc) == 0))
goto bail;
- qib_get_mr(mr);
- spin_unlock_irqrestore(&rkt->lock, flags);
+ if (unlikely(!atomic_inc_not_zero(&mr->refcount)))
+ goto bail;
+ rcu_read_unlock();
off += mr->offset;
if (mr->page_shift) {
@@ -228,20 +227,22 @@
ok:
return 1;
bail:
- spin_unlock_irqrestore(&rkt->lock, flags);
+ rcu_read_unlock();
return 0;
}
/**
* qib_rkey_ok - check the IB virtual address, length, and RKEY
- * @dev: infiniband device
- * @ss: SGE state
+ * @qp: qp for validation
+ * @sge: SGE state
* @len: length of data
* @vaddr: virtual address to place data
* @rkey: rkey to check
* @acc: access flags
*
* Return 1 if successful, otherwise 0.
+ *
+ * increments the reference count upon success
*/
int qib_rkey_ok(struct qib_qp *qp, struct qib_sge *sge,
u32 len, u64 vaddr, u32 rkey, int acc)
@@ -250,25 +251,26 @@
struct qib_mregion *mr;
unsigned n, m;
size_t off;
- unsigned long flags;
/*
* We use RKEY == zero for kernel virtual addresses
* (see qib_get_dma_mr and qib_dma.c).
*/
- spin_lock_irqsave(&rkt->lock, flags);
+ rcu_read_lock();
if (rkey == 0) {
struct qib_pd *pd = to_ipd(qp->ibqp.pd);
struct qib_ibdev *dev = to_idev(pd->ibpd.device);
if (pd->user)
goto bail;
- if (!dev->dma_mr)
+ mr = rcu_dereference(dev->dma_mr);
+ if (!mr)
goto bail;
- qib_get_mr(dev->dma_mr);
- spin_unlock_irqrestore(&rkt->lock, flags);
+ if (unlikely(!atomic_inc_not_zero(&mr->refcount)))
+ goto bail;
+ rcu_read_unlock();
- sge->mr = dev->dma_mr;
+ sge->mr = mr;
sge->vaddr = (void *) vaddr;
sge->length = len;
sge->sge_length = len;
@@ -277,16 +279,18 @@
goto ok;
}
- mr = rkt->table[(rkey >> (32 - ib_qib_lkey_table_size))];
- if (unlikely(mr == NULL || mr->lkey != rkey || qp->ibqp.pd != mr->pd))
+ mr = rcu_dereference(
+ rkt->table[(rkey >> (32 - ib_qib_lkey_table_size))]);
+ if (unlikely(!mr || mr->lkey != rkey || qp->ibqp.pd != mr->pd))
goto bail;
off = vaddr - mr->iova;
if (unlikely(vaddr < mr->iova || off + len > mr->length ||
(mr->access_flags & acc) == 0))
goto bail;
- qib_get_mr(mr);
- spin_unlock_irqrestore(&rkt->lock, flags);
+ if (unlikely(!atomic_inc_not_zero(&mr->refcount)))
+ goto bail;
+ rcu_read_unlock();
off += mr->offset;
if (mr->page_shift) {
@@ -322,7 +326,7 @@
ok:
return 1;
bail:
- spin_unlock_irqrestore(&rkt->lock, flags);
+ rcu_read_unlock();
return 0;
}