async_tx: add the async_tx api

The async_tx api provides methods for describing a chain of asynchronous
bulk memory transfers/transforms with support for inter-transactional
dependencies.  It is implemented as a dmaengine client that smooths over
the details of different hardware offload engine implementations.  Code
that is written to the api can optimize for asynchronous operation and the
api will fit the chain of operations to the available offload resources. 
 
	I imagine that any piece of ADMA hardware would register with the
	'async_*' subsystem, and a call to async_X would be routed as
	appropriate, or be run in-line. - Neil Brown

async_tx exploits the capabilities of struct dma_async_tx_descriptor to
provide an api of the following general format:

struct dma_async_tx_descriptor *
async_<operation>(..., struct dma_async_tx_descriptor *depend_tx,
			dma_async_tx_callback cb_fn, void *cb_param)
{
	struct dma_chan *chan = async_tx_find_channel(depend_tx, <operation>);
	struct dma_device *device = chan ? chan->device : NULL;
	int int_en = cb_fn ? 1 : 0;
	struct dma_async_tx_descriptor *tx = device ?
		device->device_prep_dma_<operation>(chan, len, int_en) : NULL;

	if (tx) { /* run <operation> asynchronously */
		...
		tx->tx_set_dest(addr, tx, index);
		...
		tx->tx_set_src(addr, tx, index);
		...
		async_tx_submit(chan, tx, flags, depend_tx, cb_fn, cb_param);
	} else { /* run <operation> synchronously */
		...
		<operation>
		...
		async_tx_sync_epilog(flags, depend_tx, cb_fn, cb_param);
	}

	return tx;
}

async_tx_find_channel() returns a capable channel from its pool.  The
channel pool is organized as a per-cpu array of channel pointers.  The
async_tx_rebalance() routine is tasked with managing these arrays.  In the
uniprocessor case async_tx_rebalance() tries to spread responsibility
evenly over channels of similar capabilities.  For example if there are two
copy+xor channels, one will handle copy operations and the other will
handle xor.  In the SMP case async_tx_rebalance() attempts to spread the
operations evenly over the cpus, e.g. cpu0 gets copy channel0 and xor
channel0 while cpu1 gets copy channel 1 and xor channel 1.  When a
dependency is specified async_tx_find_channel defaults to keeping the
operation on the same channel.  A xor->copy->xor chain will stay on one
channel if it supports both operation types, otherwise the transaction will
transition between a copy and a xor resource.

Currently the raid5 implementation in the MD raid456 driver has been
converted to the async_tx api.  A driver for the offload engines on the
Intel Xscale series of I/O processors, iop-adma, is provided in a later
commit.  With the iop-adma driver and async_tx, raid456 is able to offload
copy, xor, and xor-zero-sum operations to hardware engines.
 
On iop342 tiobench showed higher throughput for sequential writes (20 - 30%
improvement) and sequential reads to a degraded array (40 - 55%
improvement).  For the other cases performance was roughly equal, +/- a few
percentage points.  On a x86-smp platform the performance of the async_tx
implementation (in synchronous mode) was also +/- a few percentage points
of the original implementation.  According to 'top' on iop342 CPU
utilization drops from ~50% to ~15% during a 'resync' while the speed
according to /proc/mdstat doubles from ~25 MB/s to ~50 MB/s.
 
The tiobench command line used for testing was: tiobench --size 2048
--block 4096 --block 131072 --dir /mnt/raid --numruns 5
* iop342 had 1GB of memory available

Details:
* if CONFIG_DMA_ENGINE=n the asynchronous path is compiled away by making
  async_tx_find_channel a static inline routine that always returns NULL
* when a callback is specified for a given transaction an interrupt will
  fire at operation completion time and the callback will occur in a
  tasklet.  if the the channel does not support interrupts then a live
  polling wait will be performed
* the api is written as a dmaengine client that requests all available
  channels
* In support of dependencies the api implicitly schedules channel-switch
  interrupts.  The interrupt triggers the cleanup tasklet which causes
  pending operations to be scheduled on the next channel
* Xor engines treat an xor destination address differently than a software
  xor routine.  To the software routine the destination address is an implied
  source, whereas engines treat it as a write-only destination.  This patch
  modifies the xor_blocks routine to take a an explicit destination address
  to mirror the hardware.

Changelog:
* fixed a leftover debug print
* don't allow callbacks in async_interrupt_cond
* fixed xor_block changes
* fixed usage of ASYNC_TX_XOR_DROP_DEST
* drop dma mapping methods, suggested by Chris Leech
* printk warning fixups from Andrew Morton
* don't use inline in C files, Adrian Bunk
* select the API when MD is enabled
* BUG_ON xor source counts <= 1
* implicitly handle hardware concerns like channel switching and
  interrupts, Neil Brown
* remove the per operation type list, and distribute operation capabilities
  evenly amongst the available channels
* simplify async_tx_find_channel to optimize the fast path
* introduce the channel_table_initialized flag to prevent early calls to
  the api
* reorganize the code to mimic crypto
* include mm.h as not all archs include it in dma-mapping.h
* make the Kconfig options non-user visible, Adrian Bunk
* move async_tx under crypto since it is meant as 'core' functionality, and
  the two may share algorithms in the future
* move large inline functions into c files
* checkpatch.pl fixes
* gpl v2 only correction

Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Acked-By: NeilBrown <neilb@suse.de>

2 files changed, 159 insertions, 2 deletions

diff --git a/include/linux/async_tx.h b/include/linux/async_tx.h
new file mode 100644
index 000000000000..ff1255079fa1
--- /dev/null
+++ b/include/linux/async_tx.h
@@ -0,0 +1,156 @@
+/*
+ * Copyright © 2006, Intel Corporation.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+#ifndef _ASYNC_TX_H_
+#define _ASYNC_TX_H_
+#include <linux/dmaengine.h>
+#include <linux/spinlock.h>
+#include <linux/interrupt.h>
+
+/**
+ * dma_chan_ref - object used to manage dma channels received from the
+ *   dmaengine core.
+ * @chan - the channel being tracked
+ * @node - node for the channel to be placed on async_tx_master_list
+ * @rcu - for list_del_rcu
+ * @count - number of times this channel is listed in the pool
+ *      (for channels with multiple capabiities)
+ */
+struct dma_chan_ref {
+        struct dma_chan *chan;
+        struct list_head node;
+        struct rcu_head rcu;
+        atomic_t count;
+};
+
+/**
+ * async_tx_flags - modifiers for the async_* calls
+ * @ASYNC_TX_XOR_ZERO_DST: this flag must be used for xor operations where the
+ * the destination address is not a source.  The asynchronous case handles this
+ * implicitly, the synchronous case needs to zero the destination block.
+ * @ASYNC_TX_XOR_DROP_DST: this flag must be used if the destination address is
+ * also one of the source addresses.  In the synchronous case the destination
+ * address is an implied source, whereas the asynchronous case it must be listed
+ * as a source.  The destination address must be the first address in the source
+ * array.
+ * @ASYNC_TX_ASSUME_COHERENT: skip cache maintenance operations
+ * @ASYNC_TX_ACK: immediately ack the descriptor, precludes setting up a
+ * dependency chain
+ * @ASYNC_TX_DEP_ACK: ack the dependency descriptor.  Useful for chaining.
+ * @ASYNC_TX_KMAP_SRC: if the transaction is to be performed synchronously
+ * take an atomic mapping (KM_USER0) on the source page(s)
+ * @ASYNC_TX_KMAP_DST: if the transaction is to be performed synchronously
+ * take an atomic mapping (KM_USER0) on the dest page(s)
+ */
+enum async_tx_flags {
+        ASYNC_TX_XOR_ZERO_DST    = (1 << 0),
+        ASYNC_TX_XOR_DROP_DST    = (1 << 1),
+        ASYNC_TX_ASSUME_COHERENT = (1 << 2),
+        ASYNC_TX_ACK             = (1 << 3),
+        ASYNC_TX_DEP_ACK         = (1 << 4),
+        ASYNC_TX_KMAP_SRC        = (1 << 5),
+        ASYNC_TX_KMAP_DST        = (1 << 6),
+};
+
+#ifdef CONFIG_DMA_ENGINE
+void async_tx_issue_pending_all(void);
+enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx);
+void async_tx_run_dependencies(struct dma_async_tx_descriptor *tx);
+struct dma_chan *
+async_tx_find_channel(struct dma_async_tx_descriptor *depend_tx,
+        enum dma_transaction_type tx_type);
+#else
+static inline void async_tx_issue_pending_all(void)
+{
+        do { } while (0);
+}
+
+static inline enum dma_status
+dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx)
+{
+        return DMA_SUCCESS;
+}
+
+static inline void
+async_tx_run_dependencies(struct dma_async_tx_descriptor *tx,
+        struct dma_chan *host_chan)
+{
+        do { } while (0);
+}
+
+static inline struct dma_chan *
+async_tx_find_channel(struct dma_async_tx_descriptor *depend_tx,
+        enum dma_transaction_type tx_type)
+{
+        return NULL;
+}
+#endif
+
+/**
+ * async_tx_sync_epilog - actions to take if an operation is run synchronously
+ * @flags: async_tx flags
+ * @depend_tx: transaction depends on depend_tx
+ * @cb_fn: function to call when the transaction completes
+ * @cb_fn_param: parameter to pass to the callback routine
+ */
+static inline void
+async_tx_sync_epilog(unsigned long flags,
+        struct dma_async_tx_descriptor *depend_tx,
+        dma_async_tx_callback cb_fn, void *cb_fn_param)
+{
+        if (cb_fn)
+                cb_fn(cb_fn_param);
+
+        if (depend_tx && (flags & ASYNC_TX_DEP_ACK))
+                async_tx_ack(depend_tx);
+}
+
+void
+async_tx_submit(struct dma_chan *chan, struct dma_async_tx_descriptor *tx,
+        enum async_tx_flags flags, struct dma_async_tx_descriptor *depend_tx,
+        dma_async_tx_callback cb_fn, void *cb_fn_param);
+
+struct dma_async_tx_descriptor *
+async_xor(struct page *dest, struct page **src_list, unsigned int offset,
+        int src_cnt, size_t len, enum async_tx_flags flags,
+        struct dma_async_tx_descriptor *depend_tx,
+        dma_async_tx_callback cb_fn, void *cb_fn_param);
+
+struct dma_async_tx_descriptor *
+async_xor_zero_sum(struct page *dest, struct page **src_list,
+        unsigned int offset, int src_cnt, size_t len,
+        u32 *result, enum async_tx_flags flags,
+        struct dma_async_tx_descriptor *depend_tx,
+        dma_async_tx_callback cb_fn, void *cb_fn_param);
+
+struct dma_async_tx_descriptor *
+async_memcpy(struct page *dest, struct page *src, unsigned int dest_offset,
+        unsigned int src_offset, size_t len, enum async_tx_flags flags,
+        struct dma_async_tx_descriptor *depend_tx,
+        dma_async_tx_callback cb_fn, void *cb_fn_param);
+
+struct dma_async_tx_descriptor *
+async_memset(struct page *dest, int val, unsigned int offset,
+        size_t len, enum async_tx_flags flags,
+        struct dma_async_tx_descriptor *depend_tx,
+        dma_async_tx_callback cb_fn, void *cb_fn_param);
+
+struct dma_async_tx_descriptor *
+async_trigger_callback(enum async_tx_flags flags,
+        struct dma_async_tx_descriptor *depend_tx,
+        dma_async_tx_callback cb_fn, void *cb_fn_param);
+#endif /* _ASYNC_TX_H_ */
diff --git a/include/linux/raid/xor.h b/include/linux/raid/xor.h
index 7d6c20b654fa..3e120587eada 100644
--- a/include/linux/raid/xor.h
+++ b/include/linux/raid/xor.h
@@ -3,9 +3,10 @@
 
 #include <linux/raid/md.h>
 
-#define MAX_XOR_BLOCKS 5
+#define MAX_XOR_BLOCKS 4
 
-extern void xor_blocks(unsigned int count, unsigned int bytes, void **ptr);
+extern void xor_blocks(unsigned int count, unsigned int bytes,
+        void *dest, void **srcs);
 
 struct xor_block_template {
         struct xor_block_template *next;