/* General filesystem caching backing cache interface
 *
 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 *
 * NOTE!!! See:
 *
 *      Documentation/filesystems/caching/backend-api.txt
 *
 * for a description of the cache backend interface declared here.
 */

#ifndef _LINUX_FSCACHE_CACHE_H
#define _LINUX_FSCACHE_CACHE_H

#include <linux/fscache.h>
#include <linux/sched.h>
#include <linux/workqueue.h>

#define NR_MAXCACHES BITS_PER_LONG

struct fscache_cache;
struct fscache_cache_ops;
struct fscache_object;
struct fscache_operation;

/*
 * cache tag definition
 */
struct fscache_cache_tag {
        struct list_head        link;
        struct fscache_cache    *cache;         /* cache referred to by this tag */
        unsigned long           flags;
#define FSCACHE_TAG_RESERVED    0               /* T if tag is reserved for a cache */
        atomic_t                usage;
        char                    name[0];        /* tag name */
};

/*
 * cache definition
 */
struct fscache_cache {
        const struct fscache_cache_ops *ops;
        struct fscache_cache_tag *tag;          /* tag representing this cache */
        struct kobject          *kobj;          /* system representation of this cache */
        struct list_head        link;           /* link in list of caches */
        size_t                  max_index_size; /* maximum size of index data */
        char                    identifier[36]; /* cache label */

        /* node management */
        struct work_struct      op_gc;          /* operation garbage collector */
        struct list_head        object_list;    /* list of data/index objects */
        struct list_head        op_gc_list;     /* list of ops to be deleted */
        spinlock_t              object_list_lock;
        spinlock_t              op_gc_list_lock;
        atomic_t                object_count;   /* no. of live objects in this cache */
        struct fscache_object   *fsdef;         /* object for the fsdef index */
        unsigned long           flags;
#define FSCACHE_IOERROR         0       /* cache stopped on I/O error */
#define FSCACHE_CACHE_WITHDRAWN 1       /* cache has been withdrawn */
};

extern wait_queue_head_t fscache_cache_cleared_wq;

/*
 * operation to be applied to a cache object
 * - retrieval initiation operations are done in the context of the process
 *   that issued them, and not in an async thread pool
 */
typedef void (*fscache_operation_release_t)(struct fscache_operation *op);
typedef void (*fscache_operation_processor_t)(struct fscache_operation *op);

struct fscache_operation {
        struct work_struct      work;           /* record for async ops */
        struct list_head        pend_link;      /* link in object->pending_ops */
        struct fscache_object   *object;        /* object to be operated upon */

        unsigned long           flags;
#define FSCACHE_OP_TYPE         0x000f  /* operation type */
#define FSCACHE_OP_ASYNC        0x0001  /* - async op, processor may sleep for disk */
#define FSCACHE_OP_MYTHREAD     0x0002  /* - processing is done be issuing thread, not pool */
#define FSCACHE_OP_WAITING      4       /* cleared when op is woken */
#define FSCACHE_OP_EXCLUSIVE    5       /* exclusive op, other ops must wait */
#define FSCACHE_OP_DEAD         6       /* op is now dead */
#define FSCACHE_OP_DEC_READ_CNT 7       /* decrement object->n_reads on destruction */
#define FSCACHE_OP_KEEP_FLAGS   0xc0    /* flags to keep when repurposing an op */

        atomic_t                usage;
        unsigned                debug_id;       /* debugging ID */

        /* operation processor callback
         * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
         *   the op in a non-pool thread */
        fscache_operation_processor_t processor;

        /* operation releaser */
        fscache_operation_release_t release;
};

extern atomic_t fscache_op_debug_id;
extern void fscache_op_work_func(struct work_struct *work);

extern void fscache_enqueue_operation(struct fscache_operation *);
extern void fscache_put_operation(struct fscache_operation *);

/**
 * fscache_operation_init - Do basic initialisation of an operation
 * @op: The operation to initialise
 * @release: The release function to assign
 *
 * Do basic initialisation of an operation.  The caller must still set flags,
 * object and processor if needed.
 */
static inline void fscache_operation_init(struct fscache_operation *op,
                                        fscache_operation_processor_t processor,
                                        fscache_operation_release_t release)
{
        INIT_WORK(&op->work, fscache_op_work_func);
        atomic_set(&op->usage, 1);
        op->debug_id = atomic_inc_return(&fscache_op_debug_id);
        op->processor = processor;
        op->release = release;
        INIT_LIST_HEAD(&op->pend_link);
}

/*
 * data read operation
 */
struct fscache_retrieval {
        struct fscache_operation op;
        struct address_space    *mapping;       /* netfs pages */
        fscache_rw_complete_t   end_io_func;    /* function to call on I/O completion */
        void                    *context;       /* netfs read context (pinned) */
        struct list_head        to_do;          /* list of things to be done by the backend */
        unsigned long           start_time;     /* time at which retrieval started */
};

typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
                                             struct page *page,
                                             gfp_t gfp);

typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
                                              struct list_head *pages,
                                              unsigned *nr_pages,
                                              gfp_t gfp);

/**
 * fscache_get_retrieval - Get an extra reference on a retrieval operation
 * @op: The retrieval operation to get a reference on
 *
 * Get an extra reference on a retrieval operation.
 */
static inline
struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
{
        atomic_inc(&op->op.usage);
        return op;
}

/**
 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
 * @op: The retrieval operation affected
 *
 * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
 */
static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
{
        fscache_enqueue_operation(&op->op);
}

/**
 * fscache_put_retrieval - Drop a reference to a retrieval operation
 * @op: The retrieval operation affected
 *
 * Drop a reference to a retrieval operation.
 */
static inline void fscache_put_retrieval(struct fscache_retrieval *op)
{
        fscache_put_operation(&op->op);
}

/*
 * cached page storage work item
 * - used to do three things:
 *   - batch writes to the cache
 *   - do cache writes asynchronously
 *   - defer writes until cache object lookup completion
 */
struct fscache_storage {
        struct fscache_operation op;
        pgoff_t                 store_limit;    /* don't write more than this */
};

/*
 * cache operations
 */
struct fscache_cache_ops {
        /* name of cache provider */
        const char *name;

        /* allocate an object record for a cookie */
        struct fscache_object *(*alloc_object)(struct fscache_cache *cache,
                                               struct fscache_cookie *cookie);

        /* look up the object for a cookie
         * - return -ETIMEDOUT to be requeued
         */
        int (*lookup_object)(struct fscache_object *object);

        /* finished looking up */
        void (*lookup_complete)(struct fscache_object *object);

        /* increment the usage count on this object (may fail if unmounting) */
        struct fscache_object *(*grab_object)(struct fscache_object *object);

        /* pin an object in the cache */
        int (*pin_object)(struct fscache_object *object);

        /* unpin an object in the cache */
        void (*unpin_object)(struct fscache_object *object);

        /* store the updated auxiliary data on an object */
        void (*update_object)(struct fscache_object *object);

        /* discard the resources pinned by an object and effect retirement if
         * necessary */
        void (*drop_object)(struct fscache_object *object);

        /* dispose of a reference to an object */
        void (*put_object)(struct fscache_object *object);

        /* sync a cache */
        void (*sync_cache)(struct fscache_cache *cache);

        /* notification that the attributes of a non-index object (such as
         * i_size) have changed */
        int (*attr_changed)(struct fscache_object *object);

        /* reserve space for an object's data and associated metadata */
        int (*reserve_space)(struct fscache_object *object, loff_t i_size);

        /* request a backing block for a page be read or allocated in the
         * cache */
        fscache_page_retrieval_func_t read_or_alloc_page;

        /* request backing blocks for a list of pages be read or allocated in
         * the cache */
        fscache_pages_retrieval_func_t read_or_alloc_pages;

        /* request a backing block for a page be allocated in the cache so that
         * it can be written directly */
        fscache_page_retrieval_func_t allocate_page;

        /* request backing blocks for pages be allocated in the cache so that
         * they can be written directly */
        fscache_pages_retrieval_func_t allocate_pages;

        /* write a page to its backing block in the cache */
        int (*write_page)(struct fscache_storage *op, struct page *page);

        /* detach backing block from a page (optional)
         * - must release the cookie lock before returning
         * - may sleep
         */
        void (*uncache_page)(struct fscache_object *object,
                             struct page *page);

        /* dissociate a cache from all the pages it was backing */
        void (*dissociate_pages)(struct fscache_cache *cache);
};

/*
 * data file or index object cookie
 * - a file will only appear in one cache
 * - a request to cache a file may or may not be honoured, subject to
 *   constraints such as disk space
 * - indices are created on disk just-in-time
 */
struct fscache_cookie {
        atomic_t                        usage;          /* number of users of this cookie */
        atomic_t                        n_children;     /* number of children of this cookie */
        spinlock_t                      lock;
        spinlock_t                      stores_lock;    /* lock on page store tree */
        struct hlist_head               backing_objects; /* object(s) backing this file/index */
        const struct fscache_cookie_def *def;           /* definition */
        struct fscache_cookie           *parent;        /* parent of this entry */
        void                            *netfs_data;    /* back pointer to netfs */
        struct radix_tree_root          stores;         /* pages to be stored on this cookie */
#define FSCACHE_COOKIE_PENDING_TAG      0               /* pages tag: pending write to cache */
#define FSCACHE_COOKIE_STORING_TAG      1               /* pages tag: writing to cache */

        unsigned long                   flags;
#define FSCACHE_COOKIE_LOOKING_UP       0       /* T if non-index cookie being looked up still */
#define FSCACHE_COOKIE_CREATING         1       /* T if non-index object being created still */
#define FSCACHE_COOKIE_NO_DATA_YET      2       /* T if new object with no cached data yet */
#define FSCACHE_COOKIE_PENDING_FILL     3       /* T if pending initial fill on object */
#define FSCACHE_COOKIE_FILLING          4       /* T if filling object incrementally */
#define FSCACHE_COOKIE_UNAVAILABLE      5       /* T if cookie is unavailable (error, etc) */
};

extern struct fscache_cookie fscache_fsdef_index;

/*
 * on-disk cache file or index handle
 */
struct fscache_object {
        enum fscache_object_state {
                FSCACHE_OBJECT_INIT,            /* object in initial unbound state */
                FSCACHE_OBJECT_LOOKING_UP,      /* looking up object */
                FSCACHE_OBJECT_CREATING,        /* creating object */

                /* active states */
                FSCACHE_OBJECT_AVAILABLE,       /* cleaning up object after creation */
                FSCACHE_OBJECT_ACTIVE,          /* object is usable */
                FSCACHE_OBJECT_UPDATING,        /* object is updating */

                /* terminal states */
                FSCACHE_OBJECT_DYING,           /* object waiting for accessors to finish */
                FSCACHE_OBJECT_LC_DYING,        /* object cleaning up after lookup/create */
                FSCACHE_OBJECT_ABORT_INIT,      /* abort the init state */
                FSCACHE_OBJECT_RELEASING,       /* releasing object */
                FSCACHE_OBJECT_RECYCLING,       /* retiring object */
                FSCACHE_OBJECT_WITHDRAWING,     /* withdrawing object */
                FSCACHE_OBJECT_DEAD,            /* object is now dead */
                FSCACHE_OBJECT__NSTATES
        } state;

        int                     debug_id;       /* debugging ID */
        int                     n_children;     /* number of child objects */
        int                     n_ops;          /* number of ops outstanding on object */
        int                     n_obj_ops;      /* number of object ops outstanding on object */
        int                     n_in_progress;  /* number of ops in progress */
        int                     n_exclusive;    /* number of exclusive ops queued */
        atomic_t                n_reads;        /* number of read ops in progress */
        spinlock_t              lock;           /* state and operations lock */

        unsigned long           lookup_jif;     /* time at which lookup started */
        unsigned long           event_mask;     /* events this object is interested in */
        unsigned long           events;         /* events to be processed by this object
                                                 * (order is important - using fls) */
#define FSCACHE_OBJECT_EV_REQUEUE       0       /* T if object should be requeued */
#define FSCACHE_OBJECT_EV_UPDATE        1       /* T if object should be updated */
#define FSCACHE_OBJECT_EV_CLEARED       2       /* T if accessors all gone */
#define FSCACHE_OBJECT_EV_ERROR         3       /* T if fatal error occurred during processing */
#define FSCACHE_OBJECT_EV_RELEASE       4       /* T if netfs requested object release */
#define FSCACHE_OBJECT_EV_RETIRE        5       /* T if netfs requested object retirement */
#define FSCACHE_OBJECT_EV_WITHDRAW      6       /* T if cache requested object withdrawal */
#define FSCACHE_OBJECT_EVENTS_MASK      0x7f    /* mask of all events*/

        unsigned long           flags;
#define FSCACHE_OBJECT_LOCK             0       /* T if object is busy being processed */
#define FSCACHE_OBJECT_PENDING_WRITE    1       /* T if object has pending write */
#define FSCACHE_OBJECT_WAITING          2       /* T if object is waiting on its parent */

        struct list_head        cache_link;     /* link in cache->object_list */
        struct hlist_node       cookie_link;    /* link in cookie->backing_objects */
        struct fscache_cache    *cache;         /* cache that supplied this object */
        struct fscache_cookie   *cookie;        /* netfs's file/index object */
        struct fscache_object   *parent;        /* parent object */
        struct work_struct      work;           /* attention scheduling record */
        struct list_head        dependents;     /* FIFO of dependent objects */
        struct list_head        dep_link;       /* link in parent's dependents list */
        struct list_head        pending_ops;    /* unstarted operations on this object */
#ifdef CONFIG_FSCACHE_OBJECT_LIST
        struct rb_node          objlist_link;   /* link in global object list */
#endif
        pgoff_t                 store_limit;    /* current storage limit */
        loff_t                  store_limit_l;  /* current storage limit */
};

extern const char *fscache_object_states[];

#define fscache_object_is_active(obj)                         \
        (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) &&  \
         (obj)->state >= FSCACHE_OBJECT_AVAILABLE &&          \
         (obj)->state < FSCACHE_OBJECT_DYING)

#define fscache_object_is_dead(obj)                             \
        (test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) &&     \
         (obj)->state >= FSCACHE_OBJECT_DYING)

extern void fscache_object_work_func(struct work_struct *work);

/**
 * fscache_object_init - Initialise a cache object description
 * @object: Object description
 *
 * Initialise a cache object description to its basic values.
 *
 * See Documentation/filesystems/caching/backend-api.txt for a complete
 * description.
 */
static inline
void fscache_object_init(struct fscache_object *object,
                         struct fscache_cookie *cookie,
                         struct fscache_cache *cache)
{
        atomic_inc(&cache->object_count);

        object->state = FSCACHE_OBJECT_INIT;
        spin_lock_init(&object->lock);
        INIT_LIST_HEAD(&object->cache_link);
        INIT_HLIST_NODE(&object->cookie_link);
        INIT_WORK(&object->work, fscache_object_work_func);
        INIT_LIST_HEAD(&object->dependents);
        INIT_LIST_HEAD(&object->dep_link);
        INIT_LIST_HEAD(&object->pending_ops);
        object->n_children = 0;
        object->n_ops = object->n_in_progress = object->n_exclusive = 0;
        object->events = object->event_mask = 0;
        object->flags = 0;
        object->store_limit = 0;
        object->store_limit_l = 0;
        object->cache = cache;
        object->cookie = cookie;
        object->parent = NULL;
}

extern void fscache_object_lookup_negative(struct fscache_object *object);
extern void fscache_obtained_object(struct fscache_object *object);

#ifdef CONFIG_FSCACHE_OBJECT_LIST
extern void fscache_object_destroy(struct fscache_object *object);
#else
#define fscache_object_destroy(object) do {} while(0)
#endif

/**
 * fscache_object_destroyed - Note destruction of an object in a cache
 * @cache: The cache from which the object came
 *
 * Note the destruction and deallocation of an object record in a cache.
 */
static inline void fscache_object_destroyed(struct fscache_cache *cache)
{
        if (atomic_dec_and_test(&cache->object_count))
                wake_up_all(&fscache_cache_cleared_wq);
}

/**
 * fscache_object_lookup_error - Note an object encountered an error
 * @object: The object on which the error was encountered
 *
 * Note that an object encountered a fatal error (usually an I/O error) and
 * that it should be withdrawn as soon as possible.
 */
static inline void fscache_object_lookup_error(struct fscache_object *object)
{
        set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
}

/**
 * fscache_set_store_limit - Set the maximum size to be stored in an object
 * @object: The object to set the maximum on
 * @i_size: The limit to set in bytes
 *
 * Set the maximum size an object is permitted to reach, implying the highest
 * byte that may be written.  Intended to be called by the attr_changed() op.
 *
 * See Documentation/filesystems/caching/backend-api.txt for a complete
 * description.
 */
static inline
void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
{
        object->store_limit_l = i_size;
        object->store_limit = i_size >> PAGE_SHIFT;
        if (i_size & ~PAGE_MASK)
                object->store_limit++;
}

/**
 * fscache_end_io - End a retrieval operation on a page
 * @op: The FS-Cache operation covering the retrieval
 * @page: The page that was to be fetched
 * @error: The error code (0 if successful)
 *
 * Note the end of an operation to retrieve a page, as covered by a particular
 * operation record.
 */
static inline void fscache_end_io(struct fscache_retrieval *op,
                                  struct page *page, int error)
{
        op->end_io_func(page, op->context, error);
}

/*
 * out-of-line cache backend functions
 */
extern __printf(3, 4)
void fscache_init_cache(struct fscache_cache *cache,
                        const struct fscache_cache_ops *ops,
                        const char *idfmt, ...);

extern int fscache_add_cache(struct fscache_cache *cache,
                             struct fscache_object *fsdef,
                             const char *tagname);
extern void fscache_withdraw_cache(struct fscache_cache *cache);

extern void fscache_io_error(struct fscache_cache *cache);

extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
                                      struct pagevec *pagevec);

extern bool fscache_object_sleep_till_congested(signed long *timeoutp);

extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
                                               const void *data,
                                               uint16_t datalen);

#endif /* _LINUX_FSCACHE_CACHE_H */