2.6.25

 block

diff --git a/block/blk-ioc.c b/block/blk-ioc.c
new file mode 100644
index 0000000..e34df7c
--- /dev/null
+++ b/block/blk-ioc.c
@@ -0,0 +1,180 @@
+/*
+ * 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)
+{
+   if (!hlist_empty(&ioc->cic_list)) {
+      struct cfq_io_context *cic;
+
+      cic = list_entry(ioc->cic_list.first, struct cfq_io_context,
+                        cic_list);
+      cic->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)
+{
+   rcu_read_lock();
+
+   if (!hlist_empty(&ioc->cic_list)) {
+      struct cfq_io_context *cic;
+
+      cic = list_entry(ioc->cic_list.first, struct cfq_io_context,
+                        cic_list);
+      cic->exit(ioc);
+   }
+   rcu_read_unlock();
+}
+
+/* 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);
+      INIT_HLIST_HEAD(&ret->cic_list);
+      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);
+
+static 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);