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authorAndy Grover <andy.grover@oracle.com>2009-02-24 18:30:31 +0300
committerDavid S. Miller <davem@davemloft.net>2009-02-27 10:39:30 +0300
commitf528efe276ec16603b78f95fb63ca26b5b4c87dc (patch)
tree5eaf262dbf69918c4155c905d950c899bc08c326 /net/rds/ib_ring.c
parentec16227e14141e4fd7ae76354c09dadfe2449d9e (diff)
downloadlinux-f528efe276ec16603b78f95fb63ca26b5b4c87dc.tar.xz
RDS/IB: Ring-handling code.
Signed-off-by: Andy Grover <andy.grover@oracle.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/rds/ib_ring.c')
-rw-r--r--net/rds/ib_ring.c168
1 files changed, 168 insertions, 0 deletions
diff --git a/net/rds/ib_ring.c b/net/rds/ib_ring.c
new file mode 100644
index 000000000000..99a6ccae964c
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+++ b/net/rds/ib_ring.c
@@ -0,0 +1,168 @@
+/*
+ * Copyright (c) 2006 Oracle. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses. You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above
+ * copyright notice, this list of conditions and the following
+ * disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following
+ * disclaimer in the documentation and/or other materials
+ * provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+
+#include "rds.h"
+#include "ib.h"
+
+/*
+ * Locking for IB rings.
+ * We assume that allocation is always protected by a mutex
+ * in the caller (this is a valid assumption for the current
+ * implementation).
+ *
+ * Freeing always happens in an interrupt, and hence only
+ * races with allocations, but not with other free()s.
+ *
+ * The interaction between allocation and freeing is that
+ * the alloc code has to determine the number of free entries.
+ * To this end, we maintain two counters; an allocation counter
+ * and a free counter. Both are allowed to run freely, and wrap
+ * around.
+ * The number of used entries is always (alloc_ctr - free_ctr) % NR.
+ *
+ * The current implementation makes free_ctr atomic. When the
+ * caller finds an allocation fails, it should set an "alloc fail"
+ * bit and retry the allocation. The "alloc fail" bit essentially tells
+ * the CQ completion handlers to wake it up after freeing some
+ * more entries.
+ */
+
+/*
+ * This only happens on shutdown.
+ */
+DECLARE_WAIT_QUEUE_HEAD(rds_ib_ring_empty_wait);
+
+void rds_ib_ring_init(struct rds_ib_work_ring *ring, u32 nr)
+{
+ memset(ring, 0, sizeof(*ring));
+ ring->w_nr = nr;
+ rdsdebug("ring %p nr %u\n", ring, ring->w_nr);
+}
+
+static inline u32 __rds_ib_ring_used(struct rds_ib_work_ring *ring)
+{
+ u32 diff;
+
+ /* This assumes that atomic_t has at least as many bits as u32 */
+ diff = ring->w_alloc_ctr - (u32) atomic_read(&ring->w_free_ctr);
+ BUG_ON(diff > ring->w_nr);
+
+ return diff;
+}
+
+void rds_ib_ring_resize(struct rds_ib_work_ring *ring, u32 nr)
+{
+ /* We only ever get called from the connection setup code,
+ * prior to creating the QP. */
+ BUG_ON(__rds_ib_ring_used(ring));
+ ring->w_nr = nr;
+}
+
+static int __rds_ib_ring_empty(struct rds_ib_work_ring *ring)
+{
+ return __rds_ib_ring_used(ring) == 0;
+}
+
+u32 rds_ib_ring_alloc(struct rds_ib_work_ring *ring, u32 val, u32 *pos)
+{
+ u32 ret = 0, avail;
+
+ avail = ring->w_nr - __rds_ib_ring_used(ring);
+
+ rdsdebug("ring %p val %u next %u free %u\n", ring, val,
+ ring->w_alloc_ptr, avail);
+
+ if (val && avail) {
+ ret = min(val, avail);
+ *pos = ring->w_alloc_ptr;
+
+ ring->w_alloc_ptr = (ring->w_alloc_ptr + ret) % ring->w_nr;
+ ring->w_alloc_ctr += ret;
+ }
+
+ return ret;
+}
+
+void rds_ib_ring_free(struct rds_ib_work_ring *ring, u32 val)
+{
+ ring->w_free_ptr = (ring->w_free_ptr + val) % ring->w_nr;
+ atomic_add(val, &ring->w_free_ctr);
+
+ if (__rds_ib_ring_empty(ring) &&
+ waitqueue_active(&rds_ib_ring_empty_wait))
+ wake_up(&rds_ib_ring_empty_wait);
+}
+
+void rds_ib_ring_unalloc(struct rds_ib_work_ring *ring, u32 val)
+{
+ ring->w_alloc_ptr = (ring->w_alloc_ptr - val) % ring->w_nr;
+ ring->w_alloc_ctr -= val;
+}
+
+int rds_ib_ring_empty(struct rds_ib_work_ring *ring)
+{
+ return __rds_ib_ring_empty(ring);
+}
+
+int rds_ib_ring_low(struct rds_ib_work_ring *ring)
+{
+ return __rds_ib_ring_used(ring) <= (ring->w_nr >> 2);
+}
+
+/*
+ * returns the oldest alloced ring entry. This will be the next one
+ * freed. This can't be called if there are none allocated.
+ */
+u32 rds_ib_ring_oldest(struct rds_ib_work_ring *ring)
+{
+ return ring->w_free_ptr;
+}
+
+/*
+ * returns the number of completed work requests.
+ */
+
+u32 rds_ib_ring_completed(struct rds_ib_work_ring *ring, u32 wr_id, u32 oldest)
+{
+ u32 ret;
+
+ if (oldest <= (unsigned long long)wr_id)
+ ret = (unsigned long long)wr_id - oldest + 1;
+ else
+ ret = ring->w_nr - oldest + (unsigned long long)wr_id + 1;
+
+ rdsdebug("ring %p ret %u wr_id %u oldest %u\n", ring, ret,
+ wr_id, oldest);
+ return ret;
+}