#ifndef IOCONTEXT_H
#define IOCONTEXT_H
#include <linux/radix-tree.h>
#include <linux/rcupdate.h>
#include <linux/workqueue.h>
enum {
ICQ_IOPRIO_CHANGED,
ICQ_CGROUP_CHANGED,
};
/*
* An io_cq (icq) is association between an io_context (ioc) and a
* request_queue (q). This is used by elevators which need to track
* information per ioc - q pair.
*
* Elevator can request use of icq by setting elevator_type->icq_size and
* ->icq_align. Both size and align must be larger than that of struct
* io_cq and elevator can use the tail area for private information. The
* recommended way to do this is defining a struct which contains io_cq as
* the first member followed by private members and using its size and
* align. For example,
*
* struct snail_io_cq {
* struct io_cq icq;
* int poke_snail;
* int feed_snail;
* };
*
* struct elevator_type snail_elv_type {
* .ops = { ... },
* .icq_size = sizeof(struct snail_io_cq),
* .icq_align = __alignof__(struct snail_io_cq),
* ...
* };
*
* If icq_size is set, block core will manage icq's. All requests will
* have its ->elv.icq field set before elevator_ops->elevator_set_req_fn()
* is called and be holding a reference to the associated io_context.
*
* Whenever a new icq is created, elevator_ops->elevator_init_icq_fn() is
* called and, on destruction, ->elevator_exit_icq_fn(). Both functions
* are called with both the associated io_context and queue locks held.
*
* Elevator is allowed to lookup icq using ioc_lookup_icq() while holding
* queue lock but the returned icq is valid only until the queue lock is
* released. Elevators can not and should not try to create or destroy
* icq's.
*
* As icq's are linked from both ioc and q, the locking rules are a bit
* complex.
*
* - ioc lock nests inside q lock.
*
* - ioc->icq_list and icq->ioc_node are protected by ioc lock.
* q->icq_list and icq->q_node by q lock.
*
* - ioc->icq_tree and ioc->icq_hint are protected by ioc lock, while icq
* itself is protected by q lock. However, both the indexes and icq
* itself are also RCU managed and lookup can be performed holding only
* the q lock.
*
* - icq's are not reference counted. They are destroyed when either the
* ioc or q goes away. Each request with icq set holds an extra
* reference to ioc to ensure it stays until the request is completed.
*
* - Linking and unlinking icq's are performed while holding both ioc and q
* locks. Due to the lock ordering, q exit is simple but ioc exit
* requires reverse-order double lock dance.
*/
struct io_cq {
struct request_queue *q;
struct io_context *ioc;
/*
* q_node and ioc_node link io_cq through icq_list of q and ioc
* respectively. Both fields are unused once ioc_exit_icq() is
* called and shared with __rcu_icq_cache and __rcu_head which are
* used for RCU free of io_cq.
*/
union {
struct list_head q_node;
struct kmem_cache *__rcu_icq_cache;
};
union {
struct hlist_node ioc_node;
struct rcu_head __rcu_head;
};
unsigned long changed;
};
/*
* I/O subsystem state of the associated processes. It is refcounted
* and kmalloc'ed. These could be shared between processes.
*/
struct io_context {
atomic_long_t refcount;
atomic_t nr_tasks;
/* all the fields below are protected by this lock */
spinlock_t lock;
unsigned short ioprio;
/*
* For request batching
*/
int nr_batch_requests; /* Number of requests left in the batch */
unsigned long last_waited; /* Time last woken after wait for request */
struct radix_tree_root icq_tree;
struct io_cq __rcu *icq_hint;
struct hlist_head icq_list;
struct work_struct release_work;
};
static inline struct io_context *ioc_task_link(struct io_context *ioc)
{
/*
* if ref count is zero, don't allow sharing (ioc is going away, it's
* a race).
*/
if (ioc && atomic_long_inc_not_zero(&ioc->refcount)) {
atomic_inc(&ioc->nr_tasks);
return ioc;
}
return NULL;
}
struct task_struct;
#ifdef CONFIG_BLOCK
void put_io_context(struct io_context *ioc, struct request_queue *locked_q);
void exit_io_context(struct task_struct *task);
struct io_context *get_task_io_context(struct task_struct *task,
gfp_t gfp_flags, int node);
void ioc_ioprio_changed(struct io_context *ioc, int ioprio);
void ioc_cgroup_changed(struct io_context *ioc);
#else
struct io_context;
static inline void put_io_context(struct io_context *ioc,
struct request_queue *locked_q) { }
static inline void exit_io_context(struct task_struct *task) { }
#endif
#endif
