/*
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#ifndef __XEN_BLKIF__BACKEND__COMMON_H__
#define __XEN_BLKIF__BACKEND__COMMON_H__

#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/vmalloc.h>
#include <linux/wait.h>
#include <linux/io.h>
#include <linux/rbtree.h>
#include <asm/setup.h>
#include <asm/hypervisor.h>
#include <xen/grant_table.h>
#include <xen/page.h>
#include <xen/xenbus.h>
#include <xen/interface/io/ring.h>
#include <xen/interface/io/blkif.h>
#include <xen/interface/io/protocols.h>

extern unsigned int xen_blkif_max_ring_order;
extern unsigned int xenblk_max_queues;
/*
 * This is the maximum number of segments that would be allowed in indirect
 * requests. This value will also be passed to the frontend.
 */
#define MAX_INDIRECT_SEGMENTS 256

/*
 * Xen use 4K pages. The guest may use different page size (4K or 64K)
 * Number of Xen pages per segment
 */
#define XEN_PAGES_PER_SEGMENT   (PAGE_SIZE / XEN_PAGE_SIZE)

#define XEN_PAGES_PER_INDIRECT_FRAME \
        (XEN_PAGE_SIZE/sizeof(struct blkif_request_segment))
#define SEGS_PER_INDIRECT_FRAME \
        (XEN_PAGES_PER_INDIRECT_FRAME / XEN_PAGES_PER_SEGMENT)

#define MAX_INDIRECT_PAGES \
        ((MAX_INDIRECT_SEGMENTS + SEGS_PER_INDIRECT_FRAME - 1)/SEGS_PER_INDIRECT_FRAME)
#define INDIRECT_PAGES(_segs) DIV_ROUND_UP(_segs, XEN_PAGES_PER_INDIRECT_FRAME)

/* Not a real protocol.  Used to generate ring structs which contain
 * the elements common to all protocols only.  This way we get a
 * compiler-checkable way to use common struct elements, so we can
 * avoid using switch(protocol) in a number of places.  */
struct blkif_common_request {
        char dummy;
};

/* i386 protocol version */

struct blkif_x86_32_request_rw {
        uint8_t        nr_segments;  /* number of segments                   */
        blkif_vdev_t   handle;       /* only for read/write requests         */
        uint64_t       id;           /* private guest value, echoed in resp  */
        blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
        struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
} __attribute__((__packed__));

struct blkif_x86_32_request_discard {
        uint8_t        flag;         /* BLKIF_DISCARD_SECURE or zero         */
        blkif_vdev_t   _pad1;        /* was "handle" for read/write requests */
        uint64_t       id;           /* private guest value, echoed in resp  */
        blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
        uint64_t       nr_sectors;
} __attribute__((__packed__));

struct blkif_x86_32_request_other {
        uint8_t        _pad1;
        blkif_vdev_t   _pad2;
        uint64_t       id;           /* private guest value, echoed in resp  */
} __attribute__((__packed__));

struct blkif_x86_32_request_indirect {
        uint8_t        indirect_op;
        uint16_t       nr_segments;
        uint64_t       id;
        blkif_sector_t sector_number;
        blkif_vdev_t   handle;
        uint16_t       _pad1;
        grant_ref_t    indirect_grefs[BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST];
        /*
         * The maximum number of indirect segments (and pages) that will
         * be used is determined by MAX_INDIRECT_SEGMENTS, this value
         * is also exported to the guest (via xenstore
         * feature-max-indirect-segments entry), so the frontend knows how
         * many indirect segments the backend supports.
         */
        uint64_t       _pad2;        /* make it 64 byte aligned */
} __attribute__((__packed__));

struct blkif_x86_32_request {
        uint8_t        operation;    /* BLKIF_OP_???                         */
        union {
                struct blkif_x86_32_request_rw rw;
                struct blkif_x86_32_request_discard discard;
                struct blkif_x86_32_request_other other;
                struct blkif_x86_32_request_indirect indirect;
        } u;
} __attribute__((__packed__));

/* x86_64 protocol version */

struct blkif_x86_64_request_rw {
        uint8_t        nr_segments;  /* number of segments                   */
        blkif_vdev_t   handle;       /* only for read/write requests         */
        uint32_t       _pad1;        /* offsetof(blkif_request..,u.rw.id)==8 */
        uint64_t       id;
        blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
        struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
} __attribute__((__packed__));

struct blkif_x86_64_request_discard {
        uint8_t        flag;         /* BLKIF_DISCARD_SECURE or zero         */
        blkif_vdev_t   _pad1;        /* was "handle" for read/write requests */
        uint32_t       _pad2;        /* offsetof(blkif_..,u.discard.id)==8   */
        uint64_t       id;
        blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
        uint64_t       nr_sectors;
} __attribute__((__packed__));

struct blkif_x86_64_request_other {
        uint8_t        _pad1;
        blkif_vdev_t   _pad2;
        uint32_t       _pad3;        /* offsetof(blkif_..,u.discard.id)==8   */
        uint64_t       id;           /* private guest value, echoed in resp  */
} __attribute__((__packed__));

struct blkif_x86_64_request_indirect {
        uint8_t        indirect_op;
        uint16_t       nr_segments;
        uint32_t       _pad1;        /* offsetof(blkif_..,u.indirect.id)==8   */
        uint64_t       id;
        blkif_sector_t sector_number;
        blkif_vdev_t   handle;
        uint16_t       _pad2;
        grant_ref_t    indirect_grefs[BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST];
        /*
         * The maximum number of indirect segments (and pages) that will
         * be used is determined by MAX_INDIRECT_SEGMENTS, this value
         * is also exported to the guest (via xenstore
         * feature-max-indirect-segments entry), so the frontend knows how
         * many indirect segments the backend supports.
         */
        uint32_t       _pad3;        /* make it 64 byte aligned */
} __attribute__((__packed__));

struct blkif_x86_64_request {
        uint8_t        operation;    /* BLKIF_OP_???                         */
        union {
                struct blkif_x86_64_request_rw rw;
                struct blkif_x86_64_request_discard discard;
                struct blkif_x86_64_request_other other;
                struct blkif_x86_64_request_indirect indirect;
        } u;
} __attribute__((__packed__));

DEFINE_RING_TYPES(blkif_common, struct blkif_common_request,
                  struct blkif_response);
DEFINE_RING_TYPES(blkif_x86_32, struct blkif_x86_32_request,
                  struct blkif_response __packed);
DEFINE_RING_TYPES(blkif_x86_64, struct blkif_x86_64_request,
                  struct blkif_response);

union blkif_back_rings {
        struct blkif_back_ring        native;
        struct blkif_common_back_ring common;
        struct blkif_x86_32_back_ring x86_32;
        struct blkif_x86_64_back_ring x86_64;
};

enum blkif_protocol {
        BLKIF_PROTOCOL_NATIVE = 1,
        BLKIF_PROTOCOL_X86_32 = 2,
        BLKIF_PROTOCOL_X86_64 = 3,
};

/*
 * Default protocol if the frontend doesn't specify one.
 */
#ifdef CONFIG_X86
#  define BLKIF_PROTOCOL_DEFAULT BLKIF_PROTOCOL_X86_32
#else
#  define BLKIF_PROTOCOL_DEFAULT BLKIF_PROTOCOL_NATIVE
#endif

struct xen_vbd {
        /* What the domain refers to this vbd as. */
        blkif_vdev_t            handle;
        /* Non-zero -> read-only */
        unsigned char           readonly;
        /* VDISK_xxx */
        unsigned char           type;
        /* phys device that this vbd maps to. */
        u32                     pdevice;
        struct file             *bdev_file;
        /* Cached size parameter. */
        sector_t                size;
        unsigned int            flush_support:1;
        unsigned int            discard_secure:1;
        /* Connect-time cached feature_persistent parameter value */
        unsigned int            feature_gnt_persistent_parm:1;
        /* Persistent grants feature negotiation result */
        unsigned int            feature_gnt_persistent:1;
        unsigned int            overflow_max_grants:1;
};

struct backend_info;

/* Number of requests that we can fit in a ring */
#define XEN_BLKIF_REQS_PER_PAGE         32

struct persistent_gnt {
        struct page *page;
        grant_ref_t gnt;
        grant_handle_t handle;
        unsigned long last_used;
        bool active;
        struct rb_node node;
        struct list_head remove_node;
};

/* Per-ring information. */
struct xen_blkif_ring {
        /* Physical parameters of the comms window. */
        unsigned int            irq;
        union blkif_back_rings  blk_rings;
        void                    *blk_ring;
        /* Private fields. */
        spinlock_t              blk_ring_lock;

        wait_queue_head_t       wq;
        atomic_t                inflight;
        bool                    active;
        /* One thread per blkif ring. */
        struct task_struct      *xenblkd;
        unsigned int            waiting_reqs;

        /* List of all 'pending_req' available */
        struct list_head        pending_free;
        /* And its spinlock. */
        spinlock_t              pending_free_lock;
        wait_queue_head_t       pending_free_wq;

        /* Tree to store persistent grants. */
        struct rb_root          persistent_gnts;
        unsigned int            persistent_gnt_c;
        atomic_t                persistent_gnt_in_use;
        unsigned long           next_lru;

        /* Statistics. */
        unsigned long           st_print;
        unsigned long long      st_rd_req;
        unsigned long long      st_wr_req;
        unsigned long long      st_oo_req;
        unsigned long long      st_f_req;
        unsigned long long      st_ds_req;
        unsigned long long      st_rd_sect;
        unsigned long long      st_wr_sect;

        /* Used by the kworker that offload work from the persistent purge. */
        struct list_head        persistent_purge_list;
        struct work_struct      persistent_purge_work;

        /* Buffer of free pages to map grant refs. */
        struct gnttab_page_cache free_pages;

        struct work_struct      free_work;
        /* Thread shutdown wait queue. */
        wait_queue_head_t       shutdown_wq;
        struct xen_blkif        *blkif;
};

struct xen_blkif {
        /* Unique identifier for this interface. */
        domid_t                 domid;
        unsigned int            handle;
        /* Comms information. */
        enum blkif_protocol     blk_protocol;
        /* The VBD attached to this interface. */
        struct xen_vbd          vbd;
        /* Back pointer to the backend_info. */
        struct backend_info     *be;
        atomic_t                refcnt;
        /* for barrier (drain) requests */
        struct completion       drain_complete;
        atomic_t                drain;

        struct work_struct      free_work;
        unsigned int            nr_ring_pages;
        bool                    multi_ref;
        /* All rings for this device. */
        struct xen_blkif_ring   *rings;
        unsigned int            nr_rings;
        unsigned long           buffer_squeeze_end;
};

struct seg_buf {
        unsigned long offset;
        unsigned int nsec;
};

struct grant_page {
        struct page             *page;
        struct persistent_gnt   *persistent_gnt;
        grant_handle_t          handle;
        grant_ref_t             gref;
};

/*
 * Each outstanding request that we've passed to the lower device layers has a
 * 'pending_req' allocated to it. Each buffer_head that completes decrements
 * the pendcnt towards zero. When it hits zero, the specified domain has a
 * response queued for it, with the saved 'id' passed back.
 */
struct pending_req {
        struct xen_blkif_ring   *ring;
        u64                     id;
        int                     nr_segs;
        atomic_t                pendcnt;
        unsigned short          operation;
        int                     status;
        struct list_head        free_list;
        struct grant_page       *segments[MAX_INDIRECT_SEGMENTS];
        /* Indirect descriptors */
        struct grant_page       *indirect_pages[MAX_INDIRECT_PAGES];
        struct seg_buf          seg[MAX_INDIRECT_SEGMENTS];
        struct bio              *biolist[MAX_INDIRECT_SEGMENTS];
        struct gnttab_unmap_grant_ref unmap[MAX_INDIRECT_SEGMENTS];
        struct page                   *unmap_pages[MAX_INDIRECT_SEGMENTS];
        struct gntab_unmap_queue_data gnttab_unmap_data;
};


#define vbd_sz(_v)      bdev_nr_sectors(file_bdev((_v)->bdev_file))

#define xen_blkif_get(_b) (atomic_inc(&(_b)->refcnt))
#define xen_blkif_put(_b)                               \
        do {                                            \
                if (atomic_dec_and_test(&(_b)->refcnt)) \
                        schedule_work(&(_b)->free_work);\
        } while (0)

struct phys_req {
        unsigned short          dev;
        blkif_sector_t          nr_sects;
        struct block_device     *bdev;
        blkif_sector_t          sector_number;
};

int xen_blkif_interface_init(void);
void xen_blkif_interface_fini(void);

int xen_blkif_xenbus_init(void);
void xen_blkif_xenbus_fini(void);

irqreturn_t xen_blkif_be_int(int irq, void *dev_id);
int xen_blkif_schedule(void *arg);
void xen_blkbk_free_caches(struct xen_blkif_ring *ring);

int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
                              struct backend_info *be, int state);

int xen_blkbk_barrier(struct xenbus_transaction xbt,
                      struct backend_info *be, int state);
struct xenbus_device *xen_blkbk_xenbus(struct backend_info *be);
void xen_blkbk_unmap_purged_grants(struct work_struct *work);

#endif /* __XEN_BLKIF__BACKEND__COMMON_H__ */