Merge branch 'topic/hda' into for-linus

[mirror_ubuntu-artful-kernel.git] / include / linux / blkdev.h

#ifndef _LINUX_BLKDEV_H
#define _LINUX_BLKDEV_H

#ifdef CONFIG_BLOCK

#include <linux/sched.h>
#include <linux/major.h>
#include <linux/genhd.h>
#include <linux/list.h>
#include <linux/timer.h>
#include <linux/workqueue.h>
#include <linux/pagemap.h>
#include <linux/backing-dev.h>
#include <linux/wait.h>
#include <linux/mempool.h>
#include <linux/bio.h>
#include <linux/module.h>
#include <linux/stringify.h>
#include <linux/gfp.h>
#include <linux/bsg.h>
#include <linux/smp.h>

#include <asm/scatterlist.h>

struct scsi_ioctl_command;

struct request_queue;
struct elevator_queue;
struct request_pm_state;
struct blk_trace;
struct request;
struct sg_io_hdr;

#define BLKDEV_MIN_RQ   4
#define BLKDEV_MAX_RQ   128     /* Default maximum */

struct request;
typedef void (rq_end_io_fn)(struct request *, int);

struct request_list {
        /*
         * count[], starved[], and wait[] are indexed by
         * BLK_RW_SYNC/BLK_RW_ASYNC
         */
        int count[2];
        int starved[2];
        int elvpriv;
        mempool_t *rq_pool;
        wait_queue_head_t wait[2];
};

/*
 * request command types
 */
enum rq_cmd_type_bits {
        REQ_TYPE_FS             = 1,    /* fs request */
        REQ_TYPE_BLOCK_PC,              /* scsi command */
        REQ_TYPE_SENSE,                 /* sense request */
        REQ_TYPE_PM_SUSPEND,            /* suspend request */
        REQ_TYPE_PM_RESUME,             /* resume request */
        REQ_TYPE_PM_SHUTDOWN,           /* shutdown request */
        REQ_TYPE_SPECIAL,               /* driver defined type */
        REQ_TYPE_LINUX_BLOCK,           /* generic block layer message */
        /*
         * for ATA/ATAPI devices. this really doesn't belong here, ide should
         * use REQ_TYPE_SPECIAL and use rq->cmd[0] with the range of driver
         * private REQ_LB opcodes to differentiate what type of request this is
         */
        REQ_TYPE_ATA_TASKFILE,
        REQ_TYPE_ATA_PC,
};

/*
 * For request of type REQ_TYPE_LINUX_BLOCK, rq->cmd[0] is the opcode being
 * sent down (similar to how REQ_TYPE_BLOCK_PC means that ->cmd[] holds a
 * SCSI cdb.
 *
 * 0x00 -> 0x3f are driver private, to be used for whatever purpose they need,
 * typically to differentiate REQ_TYPE_SPECIAL requests.
 *
 */
enum {
        REQ_LB_OP_EJECT = 0x40,         /* eject request */
        REQ_LB_OP_FLUSH = 0x41,         /* flush request */
};

/*
 * request type modified bits. first four bits match BIO_RW* bits, important
 */
enum rq_flag_bits {
        __REQ_RW,               /* not set, read. set, write */
        __REQ_FAILFAST_DEV,     /* no driver retries of device errors */
        __REQ_FAILFAST_TRANSPORT, /* no driver retries of transport errors */
        __REQ_FAILFAST_DRIVER,  /* no driver retries of driver errors */
        /* above flags must match BIO_RW_* */
        __REQ_DISCARD,          /* request to discard sectors */
        __REQ_SORTED,           /* elevator knows about this request */
        __REQ_SOFTBARRIER,      /* may not be passed by ioscheduler */
        __REQ_HARDBARRIER,      /* may not be passed by drive either */
        __REQ_FUA,              /* forced unit access */
        __REQ_NOMERGE,          /* don't touch this for merging */
        __REQ_STARTED,          /* drive already may have started this one */
        __REQ_DONTPREP,         /* don't call prep for this one */
        __REQ_QUEUED,           /* uses queueing */
        __REQ_ELVPRIV,          /* elevator private data attached */
        __REQ_FAILED,           /* set if the request failed */
        __REQ_QUIET,            /* don't worry about errors */
        __REQ_PREEMPT,          /* set for "ide_preempt" requests */
        __REQ_ORDERED_COLOR,    /* is before or after barrier */
        __REQ_RW_SYNC,          /* request is sync (sync write or read) */
        __REQ_ALLOCED,          /* request came from our alloc pool */
        __REQ_RW_META,          /* metadata io request */
        __REQ_COPY_USER,        /* contains copies of user pages */
        __REQ_INTEGRITY,        /* integrity metadata has been remapped */
        __REQ_NOIDLE,           /* Don't anticipate more IO after this one */
        __REQ_IO_STAT,          /* account I/O stat */
        __REQ_MIXED_MERGE,      /* merge of different types, fail separately */
        __REQ_NR_BITS,          /* stops here */
};

#define REQ_RW          (1 << __REQ_RW)
#define REQ_FAILFAST_DEV        (1 << __REQ_FAILFAST_DEV)
#define REQ_FAILFAST_TRANSPORT  (1 << __REQ_FAILFAST_TRANSPORT)
#define REQ_FAILFAST_DRIVER     (1 << __REQ_FAILFAST_DRIVER)
#define REQ_DISCARD     (1 << __REQ_DISCARD)
#define REQ_SORTED      (1 << __REQ_SORTED)
#define REQ_SOFTBARRIER (1 << __REQ_SOFTBARRIER)
#define REQ_HARDBARRIER (1 << __REQ_HARDBARRIER)
#define REQ_FUA         (1 << __REQ_FUA)
#define REQ_NOMERGE     (1 << __REQ_NOMERGE)
#define REQ_STARTED     (1 << __REQ_STARTED)
#define REQ_DONTPREP    (1 << __REQ_DONTPREP)
#define REQ_QUEUED      (1 << __REQ_QUEUED)
#define REQ_ELVPRIV     (1 << __REQ_ELVPRIV)
#define REQ_FAILED      (1 << __REQ_FAILED)
#define REQ_QUIET       (1 << __REQ_QUIET)
#define REQ_PREEMPT     (1 << __REQ_PREEMPT)
#define REQ_ORDERED_COLOR       (1 << __REQ_ORDERED_COLOR)
#define REQ_RW_SYNC     (1 << __REQ_RW_SYNC)
#define REQ_ALLOCED     (1 << __REQ_ALLOCED)
#define REQ_RW_META     (1 << __REQ_RW_META)
#define REQ_COPY_USER   (1 << __REQ_COPY_USER)
#define REQ_INTEGRITY   (1 << __REQ_INTEGRITY)
#define REQ_NOIDLE      (1 << __REQ_NOIDLE)
#define REQ_IO_STAT     (1 << __REQ_IO_STAT)
#define REQ_MIXED_MERGE (1 << __REQ_MIXED_MERGE)

#define REQ_FAILFAST_MASK       (REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | \
                                 REQ_FAILFAST_DRIVER)

#define BLK_MAX_CDB     16

/*
 * try to put the fields that are referenced together in the same cacheline.
 * if you modify this structure, be sure to check block/blk-core.c:rq_init()
 * as well!
 */
struct request {
        struct list_head queuelist;
        struct call_single_data csd;
        int cpu;

        struct request_queue *q;

        unsigned int cmd_flags;
        enum rq_cmd_type_bits cmd_type;
        unsigned long atomic_flags;

        /* the following two fields are internal, NEVER access directly */
        sector_t __sector;              /* sector cursor */
        unsigned int __data_len;        /* total data len */

        struct bio *bio;
        struct bio *biotail;

        struct hlist_node hash; /* merge hash */
        /*
         * The rb_node is only used inside the io scheduler, requests
         * are pruned when moved to the dispatch queue. So let the
         * completion_data share space with the rb_node.
         */
        union {
                struct rb_node rb_node; /* sort/lookup */
                void *completion_data;
        };

        /*
         * two pointers are available for the IO schedulers, if they need
         * more they have to dynamically allocate it.
         */
        void *elevator_private;
        void *elevator_private2;

        struct gendisk *rq_disk;
        unsigned long start_time;

        /* Number of scatter-gather DMA addr+len pairs after
         * physical address coalescing is performed.
         */
        unsigned short nr_phys_segments;

        unsigned short ioprio;

        void *special;          /* opaque pointer available for LLD use */
        char *buffer;           /* kaddr of the current segment if available */

        int tag;
        int errors;

        int ref_count;

        /*
         * when request is used as a packet command carrier
         */
        unsigned short cmd_len;
        unsigned char __cmd[BLK_MAX_CDB];
        unsigned char *cmd;

        unsigned int extra_len; /* length of alignment and padding */
        unsigned int sense_len;
        unsigned int resid_len; /* residual count */
        void *sense;

        unsigned long deadline;
        struct list_head timeout_list;
        unsigned int timeout;
        int retries;

        /*
         * completion callback.
         */
        rq_end_io_fn *end_io;
        void *end_io_data;

        /* for bidi */
        struct request *next_rq;
};

static inline unsigned short req_get_ioprio(struct request *req)
{
        return req->ioprio;
}

/*
 * State information carried for REQ_TYPE_PM_SUSPEND and REQ_TYPE_PM_RESUME
 * requests. Some step values could eventually be made generic.
 */
struct request_pm_state
{
        /* PM state machine step value, currently driver specific */
        int     pm_step;
        /* requested PM state value (S1, S2, S3, S4, ...) */
        u32     pm_state;
        void*   data;           /* for driver use */
};

#include <linux/elevator.h>

typedef void (request_fn_proc) (struct request_queue *q);
typedef int (make_request_fn) (struct request_queue *q, struct bio *bio);
typedef int (prep_rq_fn) (struct request_queue *, struct request *);
typedef void (unplug_fn) (struct request_queue *);

struct bio_vec;
struct bvec_merge_data {
        struct block_device *bi_bdev;
        sector_t bi_sector;
        unsigned bi_size;
        unsigned long bi_rw;
};
typedef int (merge_bvec_fn) (struct request_queue *, struct bvec_merge_data *,
                             struct bio_vec *);
typedef void (prepare_flush_fn) (struct request_queue *, struct request *);
typedef void (softirq_done_fn)(struct request *);
typedef int (dma_drain_needed_fn)(struct request *);
typedef int (lld_busy_fn) (struct request_queue *q);

enum blk_eh_timer_return {
        BLK_EH_NOT_HANDLED,
        BLK_EH_HANDLED,
        BLK_EH_RESET_TIMER,
};

typedef enum blk_eh_timer_return (rq_timed_out_fn)(struct request *);

enum blk_queue_state {
        Queue_down,
        Queue_up,
};

struct blk_queue_tag {
        struct request **tag_index;     /* map of busy tags */
        unsigned long *tag_map;         /* bit map of free/busy tags */
        int busy;                       /* current depth */
        int max_depth;                  /* what we will send to device */
        int real_max_depth;             /* what the array can hold */
        atomic_t refcnt;                /* map can be shared */
};

#define BLK_SCSI_MAX_CMDS       (256)
#define BLK_SCSI_CMD_PER_LONG   (BLK_SCSI_MAX_CMDS / (sizeof(long) * 8))

struct queue_limits {
        unsigned long           bounce_pfn;
        unsigned long           seg_boundary_mask;

        unsigned int            max_hw_sectors;
        unsigned int            max_sectors;
        unsigned int            max_segment_size;
        unsigned int            physical_block_size;
        unsigned int            alignment_offset;
        unsigned int            io_min;
        unsigned int            io_opt;
        unsigned int            max_discard_sectors;
        unsigned int            discard_granularity;
        unsigned int            discard_alignment;

        unsigned short          logical_block_size;
        unsigned short          max_hw_segments;
        unsigned short          max_phys_segments;

        unsigned char           misaligned;
        unsigned char           discard_misaligned;
        unsigned char           no_cluster;
        signed char             discard_zeroes_data;
};

struct request_queue
{
        /*
         * Together with queue_head for cacheline sharing
         */
        struct list_head        queue_head;
        struct request          *last_merge;
        struct elevator_queue   *elevator;

        /*
         * the queue request freelist, one for reads and one for writes
         */
        struct request_list     rq;

        request_fn_proc         *request_fn;
        make_request_fn         *make_request_fn;
        prep_rq_fn              *prep_rq_fn;
        unplug_fn               *unplug_fn;
        merge_bvec_fn           *merge_bvec_fn;
        prepare_flush_fn        *prepare_flush_fn;
        softirq_done_fn         *softirq_done_fn;
        rq_timed_out_fn         *rq_timed_out_fn;
        dma_drain_needed_fn     *dma_drain_needed;
        lld_busy_fn             *lld_busy_fn;

        /*
         * Dispatch queue sorting
         */
        sector_t                end_sector;
        struct request          *boundary_rq;

        /*
         * Auto-unplugging state
         */
        struct timer_list       unplug_timer;
        int                     unplug_thresh;  /* After this many requests */
        unsigned long           unplug_delay;   /* After this many jiffies */
        struct work_struct      unplug_work;

        struct backing_dev_info backing_dev_info;

        /*
         * The queue owner gets to use this for whatever they like.
         * ll_rw_blk doesn't touch it.
         */
        void                    *queuedata;

        /*
         * queue needs bounce pages for pages above this limit
         */
        gfp_t                   bounce_gfp;

        /*
         * various queue flags, see QUEUE_* below
         */
        unsigned long           queue_flags;

        /*
         * protects queue structures from reentrancy. ->__queue_lock should
         * _never_ be used directly, it is queue private. always use
         * ->queue_lock.
         */
        spinlock_t              __queue_lock;
        spinlock_t              *queue_lock;

        /*
         * queue kobject
         */
        struct kobject kobj;

        /*
         * queue settings
         */
        unsigned long           nr_requests;    /* Max # of requests */
        unsigned int            nr_congestion_on;
        unsigned int            nr_congestion_off;
        unsigned int            nr_batching;

        void                    *dma_drain_buffer;
        unsigned int            dma_drain_size;
        unsigned int            dma_pad_mask;
        unsigned int            dma_alignment;

        struct blk_queue_tag    *queue_tags;
        struct list_head        tag_busy_list;

        unsigned int            nr_sorted;
        unsigned int            in_flight[2];

        unsigned int            rq_timeout;
        struct timer_list       timeout;
        struct list_head        timeout_list;

        struct queue_limits     limits;

        /*
         * sg stuff
         */
        unsigned int            sg_timeout;
        unsigned int            sg_reserved_size;
        int                     node;
#ifdef CONFIG_BLK_DEV_IO_TRACE
        struct blk_trace        *blk_trace;
#endif
        /*
         * reserved for flush operations
         */
        unsigned int            ordered, next_ordered, ordseq;
        int                     orderr, ordcolor;
        struct request          pre_flush_rq, bar_rq, post_flush_rq;
        struct request          *orig_bar_rq;

        struct mutex            sysfs_lock;

#if defined(CONFIG_BLK_DEV_BSG)
        struct bsg_class_device bsg_dev;
#endif
};

#define QUEUE_FLAG_CLUSTER      0       /* cluster several segments into 1 */
#define QUEUE_FLAG_QUEUED       1       /* uses generic tag queueing */
#define QUEUE_FLAG_STOPPED      2       /* queue is stopped */
#define QUEUE_FLAG_SYNCFULL     3       /* read queue has been filled */
#define QUEUE_FLAG_ASYNCFULL    4       /* write queue has been filled */
#define QUEUE_FLAG_DEAD         5       /* queue being torn down */
#define QUEUE_FLAG_REENTER      6       /* Re-entrancy avoidance */
#define QUEUE_FLAG_PLUGGED      7       /* queue is plugged */
#define QUEUE_FLAG_ELVSWITCH    8       /* don't use elevator, just do FIFO */
#define QUEUE_FLAG_BIDI         9       /* queue supports bidi requests */
#define QUEUE_FLAG_NOMERGES    10       /* disable merge attempts */
#define QUEUE_FLAG_SAME_COMP   11       /* force complete on same CPU */
#define QUEUE_FLAG_FAIL_IO     12       /* fake timeout */
#define QUEUE_FLAG_STACKABLE   13       /* supports request stacking */
#define QUEUE_FLAG_NONROT      14       /* non-rotational device (SSD) */
#define QUEUE_FLAG_VIRT        QUEUE_FLAG_NONROT /* paravirt device */
#define QUEUE_FLAG_IO_STAT     15       /* do IO stats */
#define QUEUE_FLAG_DISCARD     16       /* supports DISCARD */

#define QUEUE_FLAG_DEFAULT      ((1 << QUEUE_FLAG_IO_STAT) |            \
                                 (1 << QUEUE_FLAG_CLUSTER) |            \
                                 (1 << QUEUE_FLAG_STACKABLE)    |       \
                                 (1 << QUEUE_FLAG_SAME_COMP))

static inline int queue_is_locked(struct request_queue *q)
{
#ifdef CONFIG_SMP
        spinlock_t *lock = q->queue_lock;
        return lock && spin_is_locked(lock);
#else
        return 1;
#endif
}

static inline void queue_flag_set_unlocked(unsigned int flag,
                                           struct request_queue *q)
{
        __set_bit(flag, &q->queue_flags);
}

static inline int queue_flag_test_and_clear(unsigned int flag,
                                            struct request_queue *q)
{
        WARN_ON_ONCE(!queue_is_locked(q));

        if (test_bit(flag, &q->queue_flags)) {
                __clear_bit(flag, &q->queue_flags);
                return 1;
        }

        return 0;
}

static inline int queue_flag_test_and_set(unsigned int flag,
                                          struct request_queue *q)
{
        WARN_ON_ONCE(!queue_is_locked(q));

        if (!test_bit(flag, &q->queue_flags)) {
                __set_bit(flag, &q->queue_flags);
                return 0;
        }

        return 1;
}

static inline void queue_flag_set(unsigned int flag, struct request_queue *q)
{
        WARN_ON_ONCE(!queue_is_locked(q));
        __set_bit(flag, &q->queue_flags);
}

static inline void queue_flag_clear_unlocked(unsigned int flag,
                                             struct request_queue *q)
{
        __clear_bit(flag, &q->queue_flags);
}

static inline int queue_in_flight(struct request_queue *q)
{
        return q->in_flight[0] + q->in_flight[1];
}

static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)
{
        WARN_ON_ONCE(!queue_is_locked(q));
        __clear_bit(flag, &q->queue_flags);
}

enum {
        /*
         * Hardbarrier is supported with one of the following methods.
         *
         * NONE         : hardbarrier unsupported
         * DRAIN        : ordering by draining is enough
         * DRAIN_FLUSH  : ordering by draining w/ pre and post flushes
         * DRAIN_FUA    : ordering by draining w/ pre flush and FUA write
         * TAG          : ordering by tag is enough
         * TAG_FLUSH    : ordering by tag w/ pre and post flushes
         * TAG_FUA      : ordering by tag w/ pre flush and FUA write
         */
        QUEUE_ORDERED_BY_DRAIN          = 0x01,
        QUEUE_ORDERED_BY_TAG            = 0x02,
        QUEUE_ORDERED_DO_PREFLUSH       = 0x10,
        QUEUE_ORDERED_DO_BAR            = 0x20,
        QUEUE_ORDERED_DO_POSTFLUSH      = 0x40,
        QUEUE_ORDERED_DO_FUA            = 0x80,

        QUEUE_ORDERED_NONE              = 0x00,

        QUEUE_ORDERED_DRAIN             = QUEUE_ORDERED_BY_DRAIN |
                                          QUEUE_ORDERED_DO_BAR,
        QUEUE_ORDERED_DRAIN_FLUSH       = QUEUE_ORDERED_DRAIN |
                                          QUEUE_ORDERED_DO_PREFLUSH |
                                          QUEUE_ORDERED_DO_POSTFLUSH,
        QUEUE_ORDERED_DRAIN_FUA         = QUEUE_ORDERED_DRAIN |
                                          QUEUE_ORDERED_DO_PREFLUSH |
                                          QUEUE_ORDERED_DO_FUA,

        QUEUE_ORDERED_TAG               = QUEUE_ORDERED_BY_TAG |
                                          QUEUE_ORDERED_DO_BAR,
        QUEUE_ORDERED_TAG_FLUSH         = QUEUE_ORDERED_TAG |
                                          QUEUE_ORDERED_DO_PREFLUSH |
                                          QUEUE_ORDERED_DO_POSTFLUSH,
        QUEUE_ORDERED_TAG_FUA           = QUEUE_ORDERED_TAG |
                                          QUEUE_ORDERED_DO_PREFLUSH |
                                          QUEUE_ORDERED_DO_FUA,

        /*
         * Ordered operation sequence
         */
        QUEUE_ORDSEQ_STARTED    = 0x01, /* flushing in progress */
        QUEUE_ORDSEQ_DRAIN      = 0x02, /* waiting for the queue to be drained */
        QUEUE_ORDSEQ_PREFLUSH   = 0x04, /* pre-flushing in progress */
        QUEUE_ORDSEQ_BAR        = 0x08, /* original barrier req in progress */
        QUEUE_ORDSEQ_POSTFLUSH  = 0x10, /* post-flushing in progress */
        QUEUE_ORDSEQ_DONE       = 0x20,
};

#define blk_queue_plugged(q)    test_bit(QUEUE_FLAG_PLUGGED, &(q)->queue_flags)
#define blk_queue_tagged(q)     test_bit(QUEUE_FLAG_QUEUED, &(q)->queue_flags)
#define blk_queue_stopped(q)    test_bit(QUEUE_FLAG_STOPPED, &(q)->queue_flags)
#define blk_queue_nomerges(q)   test_bit(QUEUE_FLAG_NOMERGES, &(q)->queue_flags)
#define blk_queue_nonrot(q)     test_bit(QUEUE_FLAG_NONROT, &(q)->queue_flags)
#define blk_queue_io_stat(q)    test_bit(QUEUE_FLAG_IO_STAT, &(q)->queue_flags)
#define blk_queue_flushing(q)   ((q)->ordseq)
#define blk_queue_stackable(q)  \
        test_bit(QUEUE_FLAG_STACKABLE, &(q)->queue_flags)
#define blk_queue_discard(q)    test_bit(QUEUE_FLAG_DISCARD, &(q)->queue_flags)

#define blk_fs_request(rq)      ((rq)->cmd_type == REQ_TYPE_FS)
#define blk_pc_request(rq)      ((rq)->cmd_type == REQ_TYPE_BLOCK_PC)
#define blk_special_request(rq) ((rq)->cmd_type == REQ_TYPE_SPECIAL)
#define blk_sense_request(rq)   ((rq)->cmd_type == REQ_TYPE_SENSE)

#define blk_failfast_dev(rq)    ((rq)->cmd_flags & REQ_FAILFAST_DEV)
#define blk_failfast_transport(rq) ((rq)->cmd_flags & REQ_FAILFAST_TRANSPORT)
#define blk_failfast_driver(rq) ((rq)->cmd_flags & REQ_FAILFAST_DRIVER)
#define blk_noretry_request(rq) (blk_failfast_dev(rq) ||        \
                                 blk_failfast_transport(rq) ||  \
                                 blk_failfast_driver(rq))
#define blk_rq_started(rq)      ((rq)->cmd_flags & REQ_STARTED)
#define blk_rq_io_stat(rq)      ((rq)->cmd_flags & REQ_IO_STAT)
#define blk_rq_quiet(rq)        ((rq)->cmd_flags & REQ_QUIET)

#define blk_account_rq(rq)      (blk_rq_started(rq) && (blk_fs_request(rq) || blk_discard_rq(rq))) 

#define blk_pm_suspend_request(rq)      ((rq)->cmd_type == REQ_TYPE_PM_SUSPEND)
#define blk_pm_resume_request(rq)       ((rq)->cmd_type == REQ_TYPE_PM_RESUME)
#define blk_pm_request(rq)      \
        (blk_pm_suspend_request(rq) || blk_pm_resume_request(rq))

#define blk_rq_cpu_valid(rq)    ((rq)->cpu != -1)
#define blk_sorted_rq(rq)       ((rq)->cmd_flags & REQ_SORTED)
#define blk_barrier_rq(rq)      ((rq)->cmd_flags & REQ_HARDBARRIER)
#define blk_fua_rq(rq)          ((rq)->cmd_flags & REQ_FUA)
#define blk_discard_rq(rq)      ((rq)->cmd_flags & REQ_DISCARD)
#define blk_bidi_rq(rq)         ((rq)->next_rq != NULL)
/* rq->queuelist of dequeued request must be list_empty() */
#define blk_queued_rq(rq)       (!list_empty(&(rq)->queuelist))

#define list_entry_rq(ptr)      list_entry((ptr), struct request, queuelist)

#define rq_data_dir(rq)         ((rq)->cmd_flags & 1)

/*
 * We regard a request as sync, if either a read or a sync write
 */
static inline bool rw_is_sync(unsigned int rw_flags)
{
        return !(rw_flags & REQ_RW) || (rw_flags & REQ_RW_SYNC);
}

static inline bool rq_is_sync(struct request *rq)
{
        return rw_is_sync(rq->cmd_flags);
}

#define rq_is_meta(rq)          ((rq)->cmd_flags & REQ_RW_META)
#define rq_noidle(rq)           ((rq)->cmd_flags & REQ_NOIDLE)

static inline int blk_queue_full(struct request_queue *q, int sync)
{
        if (sync)
                return test_bit(QUEUE_FLAG_SYNCFULL, &q->queue_flags);
        return test_bit(QUEUE_FLAG_ASYNCFULL, &q->queue_flags);
}

static inline void blk_set_queue_full(struct request_queue *q, int sync)
{
        if (sync)
                queue_flag_set(QUEUE_FLAG_SYNCFULL, q);
        else
                queue_flag_set(QUEUE_FLAG_ASYNCFULL, q);
}

static inline void blk_clear_queue_full(struct request_queue *q, int sync)
{
        if (sync)
                queue_flag_clear(QUEUE_FLAG_SYNCFULL, q);
        else
                queue_flag_clear(QUEUE_FLAG_ASYNCFULL, q);
}


/*
 * mergeable request must not have _NOMERGE or _BARRIER bit set, nor may
 * it already be started by driver.
 */
#define RQ_NOMERGE_FLAGS        \
        (REQ_NOMERGE | REQ_STARTED | REQ_HARDBARRIER | REQ_SOFTBARRIER)
#define rq_mergeable(rq)        \
        (!((rq)->cmd_flags & RQ_NOMERGE_FLAGS) && \
         (blk_discard_rq(rq) || blk_fs_request((rq))))

/*
 * q->prep_rq_fn return values
 */
#define BLKPREP_OK              0       /* serve it */
#define BLKPREP_KILL            1       /* fatal error, kill */
#define BLKPREP_DEFER           2       /* leave on queue */

extern unsigned long blk_max_low_pfn, blk_max_pfn;

/*
 * standard bounce addresses:
 *
 * BLK_BOUNCE_HIGH      : bounce all highmem pages
 * BLK_BOUNCE_ANY       : don't bounce anything
 * BLK_BOUNCE_ISA       : bounce pages above ISA DMA boundary
 */

#if BITS_PER_LONG == 32
#define BLK_BOUNCE_HIGH         ((u64)blk_max_low_pfn << PAGE_SHIFT)
#else
#define BLK_BOUNCE_HIGH         -1ULL
#endif
#define BLK_BOUNCE_ANY          (-1ULL)
#define BLK_BOUNCE_ISA          (ISA_DMA_THRESHOLD)

/*
 * default timeout for SG_IO if none specified
 */
#define BLK_DEFAULT_SG_TIMEOUT  (60 * HZ)
#define BLK_MIN_SG_TIMEOUT      (7 * HZ)

#ifdef CONFIG_BOUNCE
extern int init_emergency_isa_pool(void);
extern void blk_queue_bounce(struct request_queue *q, struct bio **bio);
#else
static inline int init_emergency_isa_pool(void)
{
        return 0;
}
static inline void blk_queue_bounce(struct request_queue *q, struct bio **bio)
{
}
#endif /* CONFIG_MMU */

struct rq_map_data {
        struct page **pages;
        int page_order;
        int nr_entries;
        unsigned long offset;
        int null_mapped;
        int from_user;
};

struct req_iterator {
        int i;
        struct bio *bio;
};

/* This should not be used directly - use rq_for_each_segment */
#define for_each_bio(_bio)              \
        for (; _bio; _bio = _bio->bi_next)
#define __rq_for_each_bio(_bio, rq)     \
        if ((rq->bio))                  \
                for (_bio = (rq)->bio; _bio; _bio = _bio->bi_next)

#define rq_for_each_segment(bvl, _rq, _iter)                    \
        __rq_for_each_bio(_iter.bio, _rq)                       \
                bio_for_each_segment(bvl, _iter.bio, _iter.i)

#define rq_iter_last(rq, _iter)                                 \
                (_iter.bio->bi_next == NULL && _iter.i == _iter.bio->bi_vcnt-1)

#ifndef ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
# error "You should define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE for your platform"
#endif
#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
extern void rq_flush_dcache_pages(struct request *rq);
#else
static inline void rq_flush_dcache_pages(struct request *rq)
{
}
#endif

extern int blk_register_queue(struct gendisk *disk);
extern void blk_unregister_queue(struct gendisk *disk);
extern void register_disk(struct gendisk *dev);
extern void generic_make_request(struct bio *bio);
extern void blk_rq_init(struct request_queue *q, struct request *rq);
extern void blk_put_request(struct request *);
extern void __blk_put_request(struct request_queue *, struct request *);
extern struct request *blk_get_request(struct request_queue *, int, gfp_t);
extern struct request *blk_make_request(struct request_queue *, struct bio *,
                                        gfp_t);
extern void blk_insert_request(struct request_queue *, struct request *, int, void *);
extern void blk_requeue_request(struct request_queue *, struct request *);
extern int blk_rq_check_limits(struct request_queue *q, struct request *rq);
extern int blk_lld_busy(struct request_queue *q);
extern int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
                             struct bio_set *bs, gfp_t gfp_mask,
                             int (*bio_ctr)(struct bio *, struct bio *, void *),
                             void *data);
extern void blk_rq_unprep_clone(struct request *rq);
extern int blk_insert_cloned_request(struct request_queue *q,
                                     struct request *rq);
extern void blk_plug_device(struct request_queue *);
extern void blk_plug_device_unlocked(struct request_queue *);
extern int blk_remove_plug(struct request_queue *);
extern void blk_recount_segments(struct request_queue *, struct bio *);
extern int scsi_cmd_ioctl(struct request_queue *, struct gendisk *, fmode_t,
                          unsigned int, void __user *);
extern int sg_scsi_ioctl(struct request_queue *, struct gendisk *, fmode_t,
                         struct scsi_ioctl_command __user *);

/*
 * A queue has just exitted congestion.  Note this in the global counter of
 * congested queues, and wake up anyone who was waiting for requests to be
 * put back.
 */
static inline void blk_clear_queue_congested(struct request_queue *q, int sync)
{
        clear_bdi_congested(&q->backing_dev_info, sync);
}

/*
 * A queue has just entered congestion.  Flag that in the queue's VM-visible
 * state flags and increment the global gounter of congested queues.
 */
static inline void blk_set_queue_congested(struct request_queue *q, int sync)
{
        set_bdi_congested(&q->backing_dev_info, sync);
}

extern void blk_start_queue(struct request_queue *q);
extern void blk_stop_queue(struct request_queue *q);
extern void blk_sync_queue(struct request_queue *q);
extern void __blk_stop_queue(struct request_queue *q);
extern void __blk_run_queue(struct request_queue *);
extern void blk_run_queue(struct request_queue *);
extern int blk_rq_map_user(struct request_queue *, struct request *,
                           struct rq_map_data *, void __user *, unsigned long,
                           gfp_t);
extern int blk_rq_unmap_user(struct bio *);
extern int blk_rq_map_kern(struct request_queue *, struct request *, void *, unsigned int, gfp_t);
extern int blk_rq_map_user_iov(struct request_queue *, struct request *,
                               struct rq_map_data *, struct sg_iovec *, int,
                               unsigned int, gfp_t);
extern int blk_execute_rq(struct request_queue *, struct gendisk *,
                          struct request *, int);
extern void blk_execute_rq_nowait(struct request_queue *, struct gendisk *,
                                  struct request *, int, rq_end_io_fn *);
extern void blk_unplug(struct request_queue *q);

static inline struct request_queue *bdev_get_queue(struct block_device *bdev)
{
        return bdev->bd_disk->queue;
}

/*
 * blk_rq_pos()                 : the current sector
 * blk_rq_bytes()               : bytes left in the entire request
 * blk_rq_cur_bytes()           : bytes left in the current segment
 * blk_rq_err_bytes()           : bytes left till the next error boundary
 * blk_rq_sectors()             : sectors left in the entire request
 * blk_rq_cur_sectors()         : sectors left in the current segment
 */
static inline sector_t blk_rq_pos(const struct request *rq)
{
        return rq->__sector;
}

static inline unsigned int blk_rq_bytes(const struct request *rq)
{
        return rq->__data_len;
}

static inline int blk_rq_cur_bytes(const struct request *rq)
{
        return rq->bio ? bio_cur_bytes(rq->bio) : 0;
}

extern unsigned int blk_rq_err_bytes(const struct request *rq);

static inline unsigned int blk_rq_sectors(const struct request *rq)
{
        return blk_rq_bytes(rq) >> 9;
}

static inline unsigned int blk_rq_cur_sectors(const struct request *rq)
{
        return blk_rq_cur_bytes(rq) >> 9;
}

/*
 * Request issue related functions.
 */
extern struct request *blk_peek_request(struct request_queue *q);
extern void blk_start_request(struct request *rq);
extern struct request *blk_fetch_request(struct request_queue *q);

/*
 * Request completion related functions.
 *
 * blk_update_request() completes given number of bytes and updates
 * the request without completing it.
 *
 * blk_end_request() and friends.  __blk_end_request() must be called
 * with the request queue spinlock acquired.
 *
 * Several drivers define their own end_request and call
 * blk_end_request() for parts of the original function.
 * This prevents code duplication in drivers.
 */
extern bool blk_update_request(struct request *rq, int error,
                               unsigned int nr_bytes);
extern bool blk_end_request(struct request *rq, int error,
                            unsigned int nr_bytes);
extern void blk_end_request_all(struct request *rq, int error);
extern bool blk_end_request_cur(struct request *rq, int error);
extern bool blk_end_request_err(struct request *rq, int error);
extern bool __blk_end_request(struct request *rq, int error,
                              unsigned int nr_bytes);
extern void __blk_end_request_all(struct request *rq, int error);
extern bool __blk_end_request_cur(struct request *rq, int error);
extern bool __blk_end_request_err(struct request *rq, int error);

extern void blk_complete_request(struct request *);
extern void __blk_complete_request(struct request *);
extern void blk_abort_request(struct request *);
extern void blk_abort_queue(struct request_queue *);

/*
 * Access functions for manipulating queue properties
 */
extern struct request_queue *blk_init_queue_node(request_fn_proc *rfn,
                                        spinlock_t *lock, int node_id);
extern struct request_queue *blk_init_queue(request_fn_proc *, spinlock_t *);
extern void blk_cleanup_queue(struct request_queue *);
extern void blk_queue_make_request(struct request_queue *, make_request_fn *);
extern void blk_queue_bounce_limit(struct request_queue *, u64);
extern void blk_queue_max_sectors(struct request_queue *, unsigned int);
extern void blk_queue_max_hw_sectors(struct request_queue *, unsigned int);
extern void blk_queue_max_phys_segments(struct request_queue *, unsigned short);
extern void blk_queue_max_hw_segments(struct request_queue *, unsigned short);
extern void blk_queue_max_segment_size(struct request_queue *, unsigned int);
extern void blk_queue_max_discard_sectors(struct request_queue *q,
                unsigned int max_discard_sectors);
extern void blk_queue_logical_block_size(struct request_queue *, unsigned short);
extern void blk_queue_physical_block_size(struct request_queue *, unsigned short);
extern void blk_queue_alignment_offset(struct request_queue *q,
                                       unsigned int alignment);
extern void blk_limits_io_min(struct queue_limits *limits, unsigned int min);
extern void blk_queue_io_min(struct request_queue *q, unsigned int min);
extern void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt);
extern void blk_queue_io_opt(struct request_queue *q, unsigned int opt);
extern void blk_set_default_limits(struct queue_limits *lim);
extern int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
                            sector_t offset);
extern int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
                            sector_t offset);
extern void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
                              sector_t offset);
extern void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b);
extern void blk_queue_dma_pad(struct request_queue *, unsigned int);
extern void blk_queue_update_dma_pad(struct request_queue *, unsigned int);
extern int blk_queue_dma_drain(struct request_queue *q,
                               dma_drain_needed_fn *dma_drain_needed,
                               void *buf, unsigned int size);
extern void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn);
extern void blk_queue_segment_boundary(struct request_queue *, unsigned long);
extern void blk_queue_prep_rq(struct request_queue *, prep_rq_fn *pfn);
extern void blk_queue_merge_bvec(struct request_queue *, merge_bvec_fn *);
extern void blk_queue_dma_alignment(struct request_queue *, int);
extern void blk_queue_update_dma_alignment(struct request_queue *, int);
extern void blk_queue_softirq_done(struct request_queue *, softirq_done_fn *);
extern void blk_queue_rq_timed_out(struct request_queue *, rq_timed_out_fn *);
extern void blk_queue_rq_timeout(struct request_queue *, unsigned int);
extern struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev);
extern int blk_queue_ordered(struct request_queue *, unsigned, prepare_flush_fn *);
extern bool blk_do_ordered(struct request_queue *, struct request **);
extern unsigned blk_ordered_cur_seq(struct request_queue *);
extern unsigned blk_ordered_req_seq(struct request *);
extern bool blk_ordered_complete_seq(struct request_queue *, unsigned, int);

extern int blk_rq_map_sg(struct request_queue *, struct request *, struct scatterlist *);
extern void blk_dump_rq_flags(struct request *, char *);
extern void generic_unplug_device(struct request_queue *);
extern long nr_blockdev_pages(void);

int blk_get_queue(struct request_queue *);
struct request_queue *blk_alloc_queue(gfp_t);
struct request_queue *blk_alloc_queue_node(gfp_t, int);
extern void blk_put_queue(struct request_queue *);

/*
 * tag stuff
 */
#define blk_rq_tagged(rq)               ((rq)->cmd_flags & REQ_QUEUED)
extern int blk_queue_start_tag(struct request_queue *, struct request *);
extern struct request *blk_queue_find_tag(struct request_queue *, int);
extern void blk_queue_end_tag(struct request_queue *, struct request *);
extern int blk_queue_init_tags(struct request_queue *, int, struct blk_queue_tag *);
extern void blk_queue_free_tags(struct request_queue *);
extern int blk_queue_resize_tags(struct request_queue *, int);
extern void blk_queue_invalidate_tags(struct request_queue *);
extern struct blk_queue_tag *blk_init_tags(int);
extern void blk_free_tags(struct blk_queue_tag *);

static inline struct request *blk_map_queue_find_tag(struct blk_queue_tag *bqt,
                                                int tag)
{
        if (unlikely(bqt == NULL || tag >= bqt->real_max_depth))
                return NULL;
        return bqt->tag_index[tag];
}

extern int blkdev_issue_flush(struct block_device *, sector_t *);
#define DISCARD_FL_WAIT         0x01    /* wait for completion */
#define DISCARD_FL_BARRIER      0x02    /* issue DISCARD_BARRIER request */
extern int blkdev_issue_discard(struct block_device *, sector_t sector,
                sector_t nr_sects, gfp_t, int flags);

static inline int sb_issue_discard(struct super_block *sb,
                                   sector_t block, sector_t nr_blocks)
{
        block <<= (sb->s_blocksize_bits - 9);
        nr_blocks <<= (sb->s_blocksize_bits - 9);
        return blkdev_issue_discard(sb->s_bdev, block, nr_blocks, GFP_KERNEL,
                                    DISCARD_FL_BARRIER);
}

extern int blk_verify_command(unsigned char *cmd, fmode_t has_write_perm);

#define MAX_PHYS_SEGMENTS 128
#define MAX_HW_SEGMENTS 128
#define SAFE_MAX_SECTORS 255
#define BLK_DEF_MAX_SECTORS 1024

#define MAX_SEGMENT_SIZE        65536

#define BLK_SEG_BOUNDARY_MASK   0xFFFFFFFFUL

#define blkdev_entry_to_request(entry) list_entry((entry), struct request, queuelist)

static inline unsigned long queue_bounce_pfn(struct request_queue *q)
{
        return q->limits.bounce_pfn;
}

static inline unsigned long queue_segment_boundary(struct request_queue *q)
{
        return q->limits.seg_boundary_mask;
}

static inline unsigned int queue_max_sectors(struct request_queue *q)
{
        return q->limits.max_sectors;
}

static inline unsigned int queue_max_hw_sectors(struct request_queue *q)
{
        return q->limits.max_hw_sectors;
}

static inline unsigned short queue_max_hw_segments(struct request_queue *q)
{
        return q->limits.max_hw_segments;
}

static inline unsigned short queue_max_phys_segments(struct request_queue *q)
{
        return q->limits.max_phys_segments;
}

static inline unsigned int queue_max_segment_size(struct request_queue *q)
{
        return q->limits.max_segment_size;
}

static inline unsigned short queue_logical_block_size(struct request_queue *q)
{
        int retval = 512;

        if (q && q->limits.logical_block_size)
                retval = q->limits.logical_block_size;

        return retval;
}

static inline unsigned short bdev_logical_block_size(struct block_device *bdev)
{
        return queue_logical_block_size(bdev_get_queue(bdev));
}

static inline unsigned int queue_physical_block_size(struct request_queue *q)
{
        return q->limits.physical_block_size;
}

static inline int bdev_physical_block_size(struct block_device *bdev)
{
        return queue_physical_block_size(bdev_get_queue(bdev));
}

static inline unsigned int queue_io_min(struct request_queue *q)
{
        return q->limits.io_min;
}

static inline int bdev_io_min(struct block_device *bdev)
{
        return queue_io_min(bdev_get_queue(bdev));
}

static inline unsigned int queue_io_opt(struct request_queue *q)
{
        return q->limits.io_opt;
}

static inline int bdev_io_opt(struct block_device *bdev)
{
        return queue_io_opt(bdev_get_queue(bdev));
}

static inline int queue_alignment_offset(struct request_queue *q)
{
        if (q->limits.misaligned)
                return -1;

        return q->limits.alignment_offset;
}

static inline int queue_limit_alignment_offset(struct queue_limits *lim, sector_t offset)
{
        unsigned int granularity = max(lim->physical_block_size, lim->io_min);

        offset &= granularity - 1;
        return (granularity + lim->alignment_offset - offset) & (granularity - 1);
}

static inline int queue_sector_alignment_offset(struct request_queue *q,
                                                sector_t sector)
{
        return queue_limit_alignment_offset(&q->limits, sector << 9);
}

static inline int bdev_alignment_offset(struct block_device *bdev)
{
        struct request_queue *q = bdev_get_queue(bdev);

        if (q->limits.misaligned)
                return -1;

        if (bdev != bdev->bd_contains)
                return bdev->bd_part->alignment_offset;

        return q->limits.alignment_offset;
}

static inline int queue_discard_alignment(struct request_queue *q)
{
        if (q->limits.discard_misaligned)
                return -1;

        return q->limits.discard_alignment;
}

static inline int queue_sector_discard_alignment(struct request_queue *q,
                                                 sector_t sector)
{
        struct queue_limits *lim = &q->limits;
        unsigned int alignment = (sector << 9) & (lim->discard_granularity - 1);

        return (lim->discard_granularity + lim->discard_alignment - alignment)
                & (lim->discard_granularity - 1);
}

static inline unsigned int queue_discard_zeroes_data(struct request_queue *q)
{
        if (q->limits.discard_zeroes_data == 1)
                return 1;

        return 0;
}

static inline unsigned int bdev_discard_zeroes_data(struct block_device *bdev)
{
        return queue_discard_zeroes_data(bdev_get_queue(bdev));
}

static inline int queue_dma_alignment(struct request_queue *q)
{
        return q ? q->dma_alignment : 511;
}

static inline int blk_rq_aligned(struct request_queue *q, void *addr,
                                 unsigned int len)
{
        unsigned int alignment = queue_dma_alignment(q) | q->dma_pad_mask;
        return !((unsigned long)addr & alignment) && !(len & alignment);
}

/* assumes size > 256 */
static inline unsigned int blksize_bits(unsigned int size)
{
        unsigned int bits = 8;
        do {
                bits++;
                size >>= 1;
        } while (size > 256);
        return bits;
}

static inline unsigned int block_size(struct block_device *bdev)
{
        return bdev->bd_block_size;
}

typedef struct {struct page *v;} Sector;

unsigned char *read_dev_sector(struct block_device *, sector_t, Sector *);

static inline void put_dev_sector(Sector p)
{
        page_cache_release(p.v);
}

struct work_struct;
int kblockd_schedule_work(struct request_queue *q, struct work_struct *work);

#define MODULE_ALIAS_BLOCKDEV(major,minor) \
        MODULE_ALIAS("block-major-" __stringify(major) "-" __stringify(minor))
#define MODULE_ALIAS_BLOCKDEV_MAJOR(major) \
        MODULE_ALIAS("block-major-" __stringify(major) "-*")

#if defined(CONFIG_BLK_DEV_INTEGRITY)

#define INTEGRITY_FLAG_READ     2       /* verify data integrity on read */
#define INTEGRITY_FLAG_WRITE    4       /* generate data integrity on write */

struct blk_integrity_exchg {
        void                    *prot_buf;
        void                    *data_buf;
        sector_t                sector;
        unsigned int            data_size;
        unsigned short          sector_size;
        const char              *disk_name;
};

typedef void (integrity_gen_fn) (struct blk_integrity_exchg *);
typedef int (integrity_vrfy_fn) (struct blk_integrity_exchg *);
typedef void (integrity_set_tag_fn) (void *, void *, unsigned int);
typedef void (integrity_get_tag_fn) (void *, void *, unsigned int);

struct blk_integrity {
        integrity_gen_fn        *generate_fn;
        integrity_vrfy_fn       *verify_fn;
        integrity_set_tag_fn    *set_tag_fn;
        integrity_get_tag_fn    *get_tag_fn;

        unsigned short          flags;
        unsigned short          tuple_size;
        unsigned short          sector_size;
        unsigned short          tag_size;

        const char              *name;

        struct kobject          kobj;
};

extern int blk_integrity_register(struct gendisk *, struct blk_integrity *);
extern void blk_integrity_unregister(struct gendisk *);
extern int blk_integrity_compare(struct gendisk *, struct gendisk *);
extern int blk_rq_map_integrity_sg(struct request *, struct scatterlist *);
extern int blk_rq_count_integrity_sg(struct request *);

static inline
struct blk_integrity *bdev_get_integrity(struct block_device *bdev)
{
        return bdev->bd_disk->integrity;
}

static inline struct blk_integrity *blk_get_integrity(struct gendisk *disk)
{
        return disk->integrity;
}

static inline int blk_integrity_rq(struct request *rq)
{
        if (rq->bio == NULL)
                return 0;

        return bio_integrity(rq->bio);
}

#else /* CONFIG_BLK_DEV_INTEGRITY */

#define blk_integrity_rq(rq)                    (0)
#define blk_rq_count_integrity_sg(a)            (0)
#define blk_rq_map_integrity_sg(a, b)           (0)
#define bdev_get_integrity(a)                   (0)
#define blk_get_integrity(a)                    (0)
#define blk_integrity_compare(a, b)             (0)
#define blk_integrity_register(a, b)            (0)
#define blk_integrity_unregister(a)             do { } while (0);

#endif /* CONFIG_BLK_DEV_INTEGRITY */

struct block_device_operations {
        int (*open) (struct block_device *, fmode_t);
        int (*release) (struct gendisk *, fmode_t);
        int (*locked_ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
        int (*ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
        int (*compat_ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
        int (*direct_access) (struct block_device *, sector_t,
                                                void **, unsigned long *);
        int (*media_changed) (struct gendisk *);
        unsigned long long (*set_capacity) (struct gendisk *,
                                                unsigned long long);
        int (*revalidate_disk) (struct gendisk *);
        int (*getgeo)(struct block_device *, struct hd_geometry *);
        struct module *owner;
};

extern int __blkdev_driver_ioctl(struct block_device *, fmode_t, unsigned int,
                                 unsigned long);
#else /* CONFIG_BLOCK */
/*
 * stubs for when the block layer is configured out
 */
#define buffer_heads_over_limit 0

static inline long nr_blockdev_pages(void)
{
        return 0;
}

#endif /* CONFIG_BLOCK */

#endif