root/include/linux/iocontext.h

INCLUDED FROM

DEFINITIONS

1. ioc_task_link
2. exit_io_context
3. put_io_context

#ifndef IOCONTEXT_H
#define IOCONTEXT_H

#include <linux/radix-tree.h>
#include <linux/rcupdate.h>

/*
 * This is the per-process anticipatory I/O scheduler state.
 */
struct as_io_context {
        spinlock_t lock;

        void (*dtor)(struct as_io_context *aic); /* destructor */
        void (*exit)(struct as_io_context *aic); /* called on task exit */

        unsigned long state;
        atomic_t nr_queued; /* queued reads & sync writes */
        atomic_t nr_dispatched; /* number of requests gone to the drivers */

        /* IO History tracking */
        /* Thinktime */
        unsigned long last_end_request;
        unsigned long ttime_total;
        unsigned long ttime_samples;
        unsigned long ttime_mean;
        /* Layout pattern */
        unsigned int seek_samples;
        sector_t last_request_pos;
        u64 seek_total;
        sector_t seek_mean;
};

struct cfq_queue;
struct cfq_io_context {
        void *key;
        unsigned long dead_key;

        struct cfq_queue *cfqq[2];

        struct io_context *ioc;

        unsigned long last_end_request;
        sector_t last_request_pos;

        unsigned long ttime_total;
        unsigned long ttime_samples;
        unsigned long ttime_mean;

        unsigned int seek_samples;
        u64 seek_total;
        sector_t seek_mean;

        struct list_head queue_list;
        struct hlist_node cic_list;

        void (*dtor)(struct io_context *); /* destructor */
        void (*exit)(struct io_context *); /* called on task exit */

        struct rcu_head rcu_head;
};

/*
 * I/O subsystem state of the associated processes.  It is refcounted
 * and kmalloc'ed. These could be shared between processes.
 */
struct io_context {
        atomic_t refcount;
        atomic_t nr_tasks;

        /* all the fields below are protected by this lock */
        spinlock_t lock;

        unsigned short ioprio;
        unsigned short ioprio_changed;

        /*
         * For request batching
         */
        unsigned long last_waited; /* Time last woken after wait for request */
        int nr_batch_requests;     /* Number of requests left in the batch */

        struct as_io_context *aic;
        struct radix_tree_root radix_root;
        struct hlist_head cic_list;
        void *ioc_data;
};

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_inc_not_zero(&ioc->refcount)) {
                atomic_inc(&ioc->nr_tasks);
                return ioc;
        }

        return NULL;
}

#ifdef CONFIG_BLOCK
int put_io_context(struct io_context *ioc);
void exit_io_context(void);
struct io_context *get_io_context(gfp_t gfp_flags, int node);
struct io_context *alloc_io_context(gfp_t gfp_flags, int node);
void copy_io_context(struct io_context **pdst, struct io_context **psrc);
#else
static inline void exit_io_context(void)
{
}

struct io_context;
static inline int put_io_context(struct io_context *ioc)
{
        return 1;
}
#endif

#endif