block: continue ll_rw_blk.c splitup

[safe/jmp/linux-2.6] / block / blk-ioc.c

diff --git a/block/blk-ioc.c b/block/blk-ioc.c
new file mode 100644 (file)
index 0000000..6d16755
--- /dev/null
+++ b/block/blk-ioc.c
@@ -0,0 +1,194 @@
+/*
+ * Functions related to io context handling
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/bio.h>
+#include <linux/blkdev.h>
+#include <linux/bootmem.h>     /* for max_pfn/max_low_pfn */
+
+#include "blk.h"
+
+/*
+ * For io context allocations
+ */
+static struct kmem_cache *iocontext_cachep;
+
+static void cfq_dtor(struct io_context *ioc)
+{
+       struct cfq_io_context *cic[1];
+       int r;
+
+       /*
+        * We don't have a specific key to lookup with, so use the gang
+        * lookup to just retrieve the first item stored. The cfq exit
+        * function will iterate the full tree, so any member will do.
+        */
+       r = radix_tree_gang_lookup(&ioc->radix_root, (void **) cic, 0, 1);
+       if (r > 0)
+               cic[0]->dtor(ioc);
+}
+
+/*
+ * IO Context helper functions. put_io_context() returns 1 if there are no
+ * more users of this io context, 0 otherwise.
+ */
+int put_io_context(struct io_context *ioc)
+{
+       if (ioc == NULL)
+               return 1;
+
+       BUG_ON(atomic_read(&ioc->refcount) == 0);
+
+       if (atomic_dec_and_test(&ioc->refcount)) {
+               rcu_read_lock();
+               if (ioc->aic && ioc->aic->dtor)
+                       ioc->aic->dtor(ioc->aic);
+               rcu_read_unlock();
+               cfq_dtor(ioc);
+
+               kmem_cache_free(iocontext_cachep, ioc);
+               return 1;
+       }
+       return 0;
+}
+EXPORT_SYMBOL(put_io_context);
+
+static void cfq_exit(struct io_context *ioc)
+{
+       struct cfq_io_context *cic[1];
+       int r;
+
+       rcu_read_lock();
+       /*
+        * See comment for cfq_dtor()
+        */
+       r = radix_tree_gang_lookup(&ioc->radix_root, (void **) cic, 0, 1);
+       rcu_read_unlock();
+
+       if (r > 0)
+               cic[0]->exit(ioc);
+}
+
+/* Called by the exitting task */
+void exit_io_context(void)
+{
+       struct io_context *ioc;
+
+       task_lock(current);
+       ioc = current->io_context;
+       current->io_context = NULL;
+       task_unlock(current);
+
+       if (atomic_dec_and_test(&ioc->nr_tasks)) {
+               if (ioc->aic && ioc->aic->exit)
+                       ioc->aic->exit(ioc->aic);
+               cfq_exit(ioc);
+
+               put_io_context(ioc);
+       }
+}
+
+struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
+{
+       struct io_context *ret;
+
+       ret = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node);
+       if (ret) {
+               atomic_set(&ret->refcount, 1);
+               atomic_set(&ret->nr_tasks, 1);
+               spin_lock_init(&ret->lock);
+               ret->ioprio_changed = 0;
+               ret->ioprio = 0;
+               ret->last_waited = jiffies; /* doesn't matter... */
+               ret->nr_batch_requests = 0; /* because this is 0 */
+               ret->aic = NULL;
+               INIT_RADIX_TREE(&ret->radix_root, GFP_ATOMIC | __GFP_HIGH);
+               ret->ioc_data = NULL;
+       }
+
+       return ret;
+}
+
+/*
+ * If the current task has no IO context then create one and initialise it.
+ * Otherwise, return its existing IO context.
+ *
+ * This returned IO context doesn't have a specifically elevated refcount,
+ * but since the current task itself holds a reference, the context can be
+ * used in general code, so long as it stays within `current` context.
+ */
+struct io_context *current_io_context(gfp_t gfp_flags, int node)
+{
+       struct task_struct *tsk = current;
+       struct io_context *ret;
+
+       ret = tsk->io_context;
+       if (likely(ret))
+               return ret;
+
+       ret = alloc_io_context(gfp_flags, node);
+       if (ret) {
+               /* make sure set_task_ioprio() sees the settings above */
+               smp_wmb();
+               tsk->io_context = ret;
+       }
+
+       return ret;
+}
+
+/*
+ * If the current task has no IO context then create one and initialise it.
+ * If it does have a context, take a ref on it.
+ *
+ * This is always called in the context of the task which submitted the I/O.
+ */
+struct io_context *get_io_context(gfp_t gfp_flags, int node)
+{
+       struct io_context *ret = NULL;
+
+       /*
+        * Check for unlikely race with exiting task. ioc ref count is
+        * zero when ioc is being detached.
+        */
+       do {
+               ret = current_io_context(gfp_flags, node);
+               if (unlikely(!ret))
+                       break;
+       } while (!atomic_inc_not_zero(&ret->refcount));
+
+       return ret;
+}
+EXPORT_SYMBOL(get_io_context);
+
+void copy_io_context(struct io_context **pdst, struct io_context **psrc)
+{
+       struct io_context *src = *psrc;
+       struct io_context *dst = *pdst;
+
+       if (src) {
+               BUG_ON(atomic_read(&src->refcount) == 0);
+               atomic_inc(&src->refcount);
+               put_io_context(dst);
+               *pdst = src;
+       }
+}
+EXPORT_SYMBOL(copy_io_context);
+
+void swap_io_context(struct io_context **ioc1, struct io_context **ioc2)
+{
+       struct io_context *temp;
+       temp = *ioc1;
+       *ioc1 = *ioc2;
+       *ioc2 = temp;
+}
+EXPORT_SYMBOL(swap_io_context);
+
+int __init blk_ioc_init(void)
+{
+       iocontext_cachep = kmem_cache_create("blkdev_ioc",
+                       sizeof(struct io_context), 0, SLAB_PANIC, NULL);
+       return 0;
+}
+subsys_initcall(blk_ioc_init);