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Subject[PATCH 03/13] block: misc ioc cleanups
Date
* int return from put_io_context() wasn't used by anybody.  Make it
return void like other put functions and docbook-fy the function
comment.

* Reorder dummy declarations for !CONFIG_BLOCK case a bit.

* Make alloc_ioc_context() use __GFP_ZERO allocation, take init out of
if block and drop 0'ing.

* Docbook-fy current_io_context() comment.

This patch doesn't introduce any functional change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
---
block/blk-ioc.c | 72 ++++++++++++++++++++++----------------------
include/linux/iocontext.h | 12 ++-----
2 files changed, 39 insertions(+), 45 deletions(-)
diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index 6f9bbd9..8bebf06 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -27,26 +27,28 @@ static void cfq_dtor(struct io_context *ioc)
}
}

-/*
- * IO Context helper functions. put_io_context() returns 1 if there are no
- * more users of this io context, 0 otherwise.
+/**
+ * put_io_context - put a reference of io_context
+ * @ioc: io_context to put
+ *
+ * Decrement reference count of @ioc and release it if the count reaches
+ * zero.
*/
-int put_io_context(struct io_context *ioc)
+void put_io_context(struct io_context *ioc)
{
if (ioc == NULL)
- return 1;
+ return;

- BUG_ON(atomic_long_read(&ioc->refcount) == 0);
+ BUG_ON(atomic_long_read(&ioc->refcount) <= 0);

- if (atomic_long_dec_and_test(&ioc->refcount)) {
- rcu_read_lock();
- cfq_dtor(ioc);
- rcu_read_unlock();
+ if (!atomic_long_dec_and_test(&ioc->refcount))
+ return;

- kmem_cache_free(iocontext_cachep, ioc);
- return 1;
- }
- return 0;
+ rcu_read_lock();
+ cfq_dtor(ioc);
+ rcu_read_unlock();
+
+ kmem_cache_free(iocontext_cachep, ioc);
}
EXPORT_SYMBOL(put_io_context);

@@ -84,33 +86,31 @@ struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
{
struct io_context *ioc;

- ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node);
- if (ioc) {
- atomic_long_set(&ioc->refcount, 1);
- atomic_set(&ioc->nr_tasks, 1);
- spin_lock_init(&ioc->lock);
- ioc->ioprio_changed = 0;
- ioc->ioprio = 0;
- ioc->last_waited = 0; /* doesn't matter... */
- ioc->nr_batch_requests = 0; /* because this is 0 */
- INIT_RADIX_TREE(&ioc->radix_root, GFP_ATOMIC | __GFP_HIGH);
- INIT_HLIST_HEAD(&ioc->cic_list);
- ioc->ioc_data = NULL;
-#if defined(CONFIG_BLK_CGROUP) || defined(CONFIG_BLK_CGROUP_MODULE)
- ioc->cgroup_changed = 0;
-#endif
- }
+ ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
+ node);
+ if (unlikely(!ioc))
+ return NULL;
+
+ /* initialize */
+ atomic_long_set(&ioc->refcount, 1);
+ atomic_set(&ioc->nr_tasks, 1);
+ spin_lock_init(&ioc->lock);
+ INIT_RADIX_TREE(&ioc->radix_root, GFP_ATOMIC | __GFP_HIGH);
+ INIT_HLIST_HEAD(&ioc->cic_list);

return ioc;
}

-/*
- * If the current task has no IO context then create one and initialise it.
- * Otherwise, return its existing IO context.
+/**
+ * current_io_context - get io_context of %current
+ * @gfp_flags: allocation flags, used if allocation is necessary
+ * @node: allocation node, used if allocation is necessary
*
- * 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.
+ * Return io_context of %current. If it doesn't exist, it is created with
+ * @gfp_flags and @node. The returned io_context does NOT have its
+ * reference count incremented. Because io_context is exited only on task
+ * exit, %current can be sure that the returned io_context is valid and
+ * alive as long as it is executing.
*/
struct io_context *current_io_context(gfp_t gfp_flags, int node)
{
diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
index 5037a0a..8a6ecb66 100644
--- a/include/linux/iocontext.h
+++ b/include/linux/iocontext.h
@@ -76,20 +76,14 @@ static inline struct io_context *ioc_task_link(struct io_context *ioc)

struct task_struct;
#ifdef CONFIG_BLOCK
-int put_io_context(struct io_context *ioc);
+void put_io_context(struct io_context *ioc);
void exit_io_context(struct task_struct *task);
struct io_context *get_io_context(gfp_t gfp_flags, int node);
struct io_context *alloc_io_context(gfp_t gfp_flags, int node);
#else
-static inline void exit_io_context(struct task_struct *task)
-{
-}
-
struct io_context;
-static inline int put_io_context(struct io_context *ioc)
-{
- return 1;
-}
+static inline void put_io_context(struct io_context *ioc) { }
+static inline void exit_io_context(struct task_struct *task) { }
#endif

#endif
--
1.7.3.1


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