dmaengine: centralize channel allocation, introduce dma_find_channel

Allowing multiple clients to each define their own channel allocation
scheme quickly leads to a pathological situation.  For memory-to-memory
offload all clients can share a central allocator.

This simply moves the existing async_tx allocator to dmaengine with
minimal fixups:
* async_tx.c:get_chan_ref_by_cap --> dmaengine.c:nth_chan
* async_tx.c:async_tx_rebalance --> dmaengine.c:dma_channel_rebalance
* split out common code from async_tx.c:__async_tx_find_channel -->
  dma_find_channel

Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 4 insertions, 142 deletions

diff --git a/crypto/async_tx/async_tx.c b/crypto/async_tx/async_tx.c
index 43fe4cbe71e..b88bb1f608f 100644
--- a/crypto/async_tx/async_tx.c
+++ b/crypto/async_tx/async_tx.c
@@ -38,25 +38,10 @@ static struct dma_client async_tx_dma = {
 };
 
 /**
- * dma_cap_mask_all - enable iteration over all operation types
- */
-static dma_cap_mask_t dma_cap_mask_all;
-
-/**
- * chan_ref_percpu - tracks channel allocations per core/opertion
- */
-struct chan_ref_percpu {
-        struct dma_chan_ref *ref;
-};
-
-static int channel_table_initialized;
-static struct chan_ref_percpu *channel_table[DMA_TX_TYPE_END];
-
-/**
  * async_tx_lock - protect modification of async_tx_master_list and serialize
  *      rebalance operations
  */
-static spinlock_t async_tx_lock;
+static DEFINE_SPINLOCK(async_tx_lock);
 
 static LIST_HEAD(async_tx_master_list);
 
@@ -89,85 +74,6 @@ init_dma_chan_ref(struct dma_chan_ref *ref, struct dma_chan *chan)
         atomic_set(&ref->count, 0);
 }
 
-/**
- * get_chan_ref_by_cap - returns the nth channel of the given capability
- *      defaults to returning the channel with the desired capability and the
- *      lowest reference count if the index can not be satisfied
- * @cap: capability to match
- * @index: nth channel desired, passing -1 has the effect of forcing the
- *  default return value
- */
-static struct dma_chan_ref *
-get_chan_ref_by_cap(enum dma_transaction_type cap, int index)
-{
-        struct dma_chan_ref *ret_ref = NULL, *min_ref = NULL, *ref;
-
-        rcu_read_lock();
-        list_for_each_entry_rcu(ref, &async_tx_master_list, node)
-                if (dma_has_cap(cap, ref->chan->device->cap_mask)) {
-                        if (!min_ref)
-                                min_ref = ref;
-                        else if (atomic_read(&ref->count) <
-                                atomic_read(&min_ref->count))
-                                min_ref = ref;
-
-                        if (index-- == 0) {
-                                ret_ref = ref;
-                                break;
-                        }
-                }
-        rcu_read_unlock();
-
-        if (!ret_ref)
-                ret_ref = min_ref;
-
-        if (ret_ref)
-                atomic_inc(&ret_ref->count);
-
-        return ret_ref;
-}
-
-/**
- * async_tx_rebalance - redistribute the available channels, optimize
- * for cpu isolation in the SMP case, and opertaion isolation in the
- * uniprocessor case
- */
-static void async_tx_rebalance(void)
-{
-        int cpu, cap, cpu_idx = 0;
-        unsigned long flags;
-
-        if (!channel_table_initialized)
-                return;
-
-        spin_lock_irqsave(&async_tx_lock, flags);
-
-        /* undo the last distribution */
-        for_each_dma_cap_mask(cap, dma_cap_mask_all)
-                for_each_possible_cpu(cpu) {
-                        struct dma_chan_ref *ref =
-                                per_cpu_ptr(channel_table[cap], cpu)->ref;
-                        if (ref) {
-                                atomic_set(&ref->count, 0);
-                                per_cpu_ptr(channel_table[cap], cpu)->ref =
-                                                                        NULL;
-                        }
-                }
-
-        for_each_dma_cap_mask(cap, dma_cap_mask_all)
-                for_each_online_cpu(cpu) {
-                        struct dma_chan_ref *new;
-                        if (NR_CPUS > 1)
-                                new = get_chan_ref_by_cap(cap, cpu_idx++);
-                        else
-                                new = get_chan_ref_by_cap(cap, -1);
-
-                        per_cpu_ptr(channel_table[cap], cpu)->ref = new;
-                }
-
-        spin_unlock_irqrestore(&async_tx_lock, flags);
-}
-
 static enum dma_state_client
 dma_channel_add_remove(struct dma_client *client,
         struct dma_chan *chan, enum dma_state state)
@@ -211,8 +117,6 @@ dma_channel_add_remove(struct dma_client *client,
                                 " (-ENOMEM)\n");
                         return 0;
                 }
-
-                async_tx_rebalance();
                 break;
         case DMA_RESOURCE_REMOVED:
                 found = 0;
@@ -233,8 +137,6 @@ dma_channel_add_remove(struct dma_client *client,
                         ack = DMA_ACK;
                 else
                         break;
-
-                async_tx_rebalance();
                 break;
         case DMA_RESOURCE_SUSPEND:
         case DMA_RESOURCE_RESUME:
@@ -248,51 +150,18 @@ dma_channel_add_remove(struct dma_client *client,
         return ack;
 }
 
-static int __init
-async_tx_init(void)
+static int __init async_tx_init(void)
 {
-        enum dma_transaction_type cap;
-
-        spin_lock_init(&async_tx_lock);
-        bitmap_fill(dma_cap_mask_all.bits, DMA_TX_TYPE_END);
-
-        /* an interrupt will never be an explicit operation type.
-         * clearing this bit prevents allocation to a slot in 'channel_table'
-         */
-        clear_bit(DMA_INTERRUPT, dma_cap_mask_all.bits);
-
-        for_each_dma_cap_mask(cap, dma_cap_mask_all) {
-                channel_table[cap] = alloc_percpu(struct chan_ref_percpu);
-                if (!channel_table[cap])
-                        goto err;
-        }
-
-        channel_table_initialized = 1;
         dma_async_client_register(&async_tx_dma);
         dma_async_client_chan_request(&async_tx_dma);
 
         printk(KERN_INFO "async_tx: api initialized (async)\n");
 
         return 0;
-err:
-        printk(KERN_ERR "async_tx: initialization failure\n");
-
-        while (--cap >= 0)
-                free_percpu(channel_table[cap]);
-
-        return 1;
 }
 
 static void __exit async_tx_exit(void)
 {
-        enum dma_transaction_type cap;
-
-        channel_table_initialized = 0;
-
-        for_each_dma_cap_mask(cap, dma_cap_mask_all)
-                if (channel_table[cap])
-                        free_percpu(channel_table[cap]);
-
         dma_async_client_unregister(&async_tx_dma);
 }
 
@@ -308,16 +177,9 @@ __async_tx_find_channel(struct dma_async_tx_descriptor *depend_tx,
 {
         /* see if we can keep the chain on one channel */
         if (depend_tx &&
-                dma_has_cap(tx_type, depend_tx->chan->device->cap_mask))
+            dma_has_cap(tx_type, depend_tx->chan->device->cap_mask))
                 return depend_tx->chan;
-        else if (likely(channel_table_initialized)) {
-                struct dma_chan_ref *ref;
-                int cpu = get_cpu();
-                ref = per_cpu_ptr(channel_table[tx_type], cpu)->ref;
-                put_cpu();
-                return ref ? ref->chan : NULL;
-        } else
-                return NULL;
+        return dma_find_channel(tx_type);
 }
 EXPORT_SYMBOL_GPL(__async_tx_find_channel);
 #else