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-rw-r--r--block/blk-core.c25
-rw-r--r--block/blk-ioc.c62
-rw-r--r--block/blk.h36
-rw-r--r--block/cfq-iosched.c2
4 files changed, 71 insertions, 54 deletions
diff --git a/block/blk-core.c b/block/blk-core.c
index fd4749391e1..6804fdf27ef 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -771,9 +771,12 @@ static struct request *get_request(struct request_queue *q, int rw_flags,
{
struct request *rq = NULL;
struct request_list *rl = &q->rq;
- struct io_context *ioc = NULL;
+ struct io_context *ioc;
const bool is_sync = rw_is_sync(rw_flags) != 0;
+ bool retried = false;
int may_queue;
+retry:
+ ioc = current->io_context;
if (unlikely(blk_queue_dead(q)))
return NULL;
@@ -784,7 +787,20 @@ static struct request *get_request(struct request_queue *q, int rw_flags,
if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
if (rl->count[is_sync]+1 >= q->nr_requests) {
- ioc = current_io_context(GFP_ATOMIC, q->node);
+ /*
+ * We want ioc to record batching state. If it's
+ * not already there, creating a new one requires
+ * dropping queue_lock, which in turn requires
+ * retesting conditions to avoid queue hang.
+ */
+ if (!ioc && !retried) {
+ spin_unlock_irq(q->queue_lock);
+ create_io_context(current, gfp_mask, q->node);
+ spin_lock_irq(q->queue_lock);
+ retried = true;
+ goto retry;
+ }
+
/*
* The queue will fill after this allocation, so set
* it as full, and mark this process as "batching".
@@ -892,7 +908,6 @@ static struct request *get_request_wait(struct request_queue *q, int rw_flags,
rq = get_request(q, rw_flags, bio, GFP_NOIO);
while (!rq) {
DEFINE_WAIT(wait);
- struct io_context *ioc;
struct request_list *rl = &q->rq;
if (unlikely(blk_queue_dead(q)))
@@ -912,8 +927,8 @@ static struct request *get_request_wait(struct request_queue *q, int rw_flags,
* up to a big batch of them for a small period time.
* See ioc_batching, ioc_set_batching
*/
- ioc = current_io_context(GFP_NOIO, q->node);
- ioc_set_batching(q, ioc);
+ create_io_context(current, GFP_NOIO, q->node);
+ ioc_set_batching(q, current->io_context);
spin_lock_irq(q->queue_lock);
finish_wait(&rl->wait[is_sync], &wait);
diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index fb23965595d..e23c797b468 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -205,16 +205,15 @@ void exit_io_context(struct task_struct *task)
put_io_context(ioc, NULL);
}
-static struct io_context *create_task_io_context(struct task_struct *task,
- gfp_t gfp_flags, int node,
- bool take_ref)
+void create_io_context_slowpath(struct task_struct *task, gfp_t gfp_flags,
+ int node)
{
struct io_context *ioc;
ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
node);
if (unlikely(!ioc))
- return NULL;
+ return;
/* initialize */
atomic_long_set(&ioc->refcount, 1);
@@ -226,42 +225,13 @@ static struct io_context *create_task_io_context(struct task_struct *task,
/* try to install, somebody might already have beaten us to it */
task_lock(task);
-
- if (!task->io_context && !(task->flags & PF_EXITING)) {
+ if (!task->io_context && !(task->flags & PF_EXITING))
task->io_context = ioc;
- } else {
+ else
kmem_cache_free(iocontext_cachep, ioc);
- ioc = task->io_context;
- }
-
- if (ioc && take_ref)
- get_io_context(ioc);
-
task_unlock(task);
- return ioc;
}
-
-/**
- * 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
- *
- * 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)
-{
- might_sleep_if(gfp_flags & __GFP_WAIT);
-
- if (current->io_context)
- return current->io_context;
-
- return create_task_io_context(current, gfp_flags, node, false);
-}
-EXPORT_SYMBOL(current_io_context);
+EXPORT_SYMBOL(create_io_context_slowpath);
/**
* get_task_io_context - get io_context of a task
@@ -274,7 +244,7 @@ EXPORT_SYMBOL(current_io_context);
* incremented.
*
* This function always goes through task_lock() and it's better to use
- * current_io_context() + get_io_context() for %current.
+ * %current->io_context + get_io_context() for %current.
*/
struct io_context *get_task_io_context(struct task_struct *task,
gfp_t gfp_flags, int node)
@@ -283,16 +253,18 @@ struct io_context *get_task_io_context(struct task_struct *task,
might_sleep_if(gfp_flags & __GFP_WAIT);
- task_lock(task);
- ioc = task->io_context;
- if (likely(ioc)) {
- get_io_context(ioc);
+ do {
+ task_lock(task);
+ ioc = task->io_context;
+ if (likely(ioc)) {
+ get_io_context(ioc);
+ task_unlock(task);
+ return ioc;
+ }
task_unlock(task);
- return ioc;
- }
- task_unlock(task);
+ } while (create_io_context(task, gfp_flags, node));
- return create_task_io_context(task, gfp_flags, node, true);
+ return NULL;
}
EXPORT_SYMBOL(get_task_io_context);
diff --git a/block/blk.h b/block/blk.h
index 8d421156fef..5bca2668e1b 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -127,9 +127,6 @@ static inline int blk_should_fake_timeout(struct request_queue *q)
}
#endif
-void get_io_context(struct io_context *ioc);
-struct io_context *current_io_context(gfp_t gfp_flags, int node);
-
int ll_back_merge_fn(struct request_queue *q, struct request *req,
struct bio *bio);
int ll_front_merge_fn(struct request_queue *q, struct request *req,
@@ -198,6 +195,39 @@ static inline int blk_do_io_stat(struct request *rq)
(rq->cmd_flags & REQ_DISCARD));
}
+/*
+ * Internal io_context interface
+ */
+void get_io_context(struct io_context *ioc);
+
+void create_io_context_slowpath(struct task_struct *task, gfp_t gfp_mask,
+ int node);
+
+/**
+ * create_io_context - try to create task->io_context
+ * @task: target task
+ * @gfp_mask: allocation mask
+ * @node: allocation node
+ *
+ * If @task->io_context is %NULL, allocate a new io_context and install it.
+ * Returns the current @task->io_context which may be %NULL if allocation
+ * failed.
+ *
+ * Note that this function can't be called with IRQ disabled because
+ * task_lock which protects @task->io_context is IRQ-unsafe.
+ */
+static inline struct io_context *create_io_context(struct task_struct *task,
+ gfp_t gfp_mask, int node)
+{
+ WARN_ON_ONCE(irqs_disabled());
+ if (unlikely(!task->io_context))
+ create_io_context_slowpath(task, gfp_mask, node);
+ return task->io_context;
+}
+
+/*
+ * Internal throttling interface
+ */
#ifdef CONFIG_BLK_DEV_THROTTLING
extern bool blk_throtl_bio(struct request_queue *q, struct bio *bio);
extern void blk_throtl_drain(struct request_queue *q);
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 3b07ce16878..5f7e4d16140 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -3012,7 +3012,7 @@ static int cfq_create_cic(struct cfq_data *cfqd, gfp_t gfp_mask)
might_sleep_if(gfp_mask & __GFP_WAIT);
/* allocate stuff */
- ioc = current_io_context(gfp_mask, q->node);
+ ioc = create_io_context(current, gfp_mask, q->node);
if (!ioc)
goto out;