linux/include/linux/aio.h
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   1#ifndef __LINUX__AIO_H
   2#define __LINUX__AIO_H
   3
   4#include <linux/list.h>
   5#include <linux/workqueue.h>
   6#include <linux/aio_abi.h>
   7#include <linux/uio.h>
   8#include <linux/rcupdate.h>
   9
  10#include <linux/atomic.h>
  11
  12#define AIO_MAXSEGS             4
  13#define AIO_KIOGRP_NR_ATOMIC    8
  14
  15struct kioctx;
  16
  17/* Notes on cancelling a kiocb:
  18 *      If a kiocb is cancelled, aio_complete may return 0 to indicate 
  19 *      that cancel has not yet disposed of the kiocb.  All cancel 
  20 *      operations *must* call aio_put_req to dispose of the kiocb 
  21 *      to guard against races with the completion code.
  22 */
  23#define KIOCB_C_CANCELLED       0x01
  24#define KIOCB_C_COMPLETE        0x02
  25
  26#define KIOCB_SYNC_KEY          (~0U)
  27
  28/* ki_flags bits */
  29/*
  30 * This may be used for cancel/retry serialization in the future, but
  31 * for now it's unused and we probably don't want modules to even
  32 * think they can use it.
  33 */
  34/* #define KIF_LOCKED           0 */
  35#define KIF_KICKED              1
  36#define KIF_CANCELLED           2
  37
  38#define kiocbTryLock(iocb)      test_and_set_bit(KIF_LOCKED, &(iocb)->ki_flags)
  39#define kiocbTryKick(iocb)      test_and_set_bit(KIF_KICKED, &(iocb)->ki_flags)
  40
  41#define kiocbSetLocked(iocb)    set_bit(KIF_LOCKED, &(iocb)->ki_flags)
  42#define kiocbSetKicked(iocb)    set_bit(KIF_KICKED, &(iocb)->ki_flags)
  43#define kiocbSetCancelled(iocb) set_bit(KIF_CANCELLED, &(iocb)->ki_flags)
  44
  45#define kiocbClearLocked(iocb)  clear_bit(KIF_LOCKED, &(iocb)->ki_flags)
  46#define kiocbClearKicked(iocb)  clear_bit(KIF_KICKED, &(iocb)->ki_flags)
  47#define kiocbClearCancelled(iocb)       clear_bit(KIF_CANCELLED, &(iocb)->ki_flags)
  48
  49#define kiocbIsLocked(iocb)     test_bit(KIF_LOCKED, &(iocb)->ki_flags)
  50#define kiocbIsKicked(iocb)     test_bit(KIF_KICKED, &(iocb)->ki_flags)
  51#define kiocbIsCancelled(iocb)  test_bit(KIF_CANCELLED, &(iocb)->ki_flags)
  52
  53/* is there a better place to document function pointer methods? */
  54/**
  55 * ki_retry     -       iocb forward progress callback
  56 * @kiocb:      The kiocb struct to advance by performing an operation.
  57 *
  58 * This callback is called when the AIO core wants a given AIO operation
  59 * to make forward progress.  The kiocb argument describes the operation
  60 * that is to be performed.  As the operation proceeds, perhaps partially,
  61 * ki_retry is expected to update the kiocb with progress made.  Typically
  62 * ki_retry is set in the AIO core and it itself calls file_operations
  63 * helpers.
  64 *
  65 * ki_retry's return value determines when the AIO operation is completed
  66 * and an event is generated in the AIO event ring.  Except the special
  67 * return values described below, the value that is returned from ki_retry
  68 * is transferred directly into the completion ring as the operation's
  69 * resulting status.  Once this has happened ki_retry *MUST NOT* reference
  70 * the kiocb pointer again.
  71 *
  72 * If ki_retry returns -EIOCBQUEUED it has made a promise that aio_complete()
  73 * will be called on the kiocb pointer in the future.  The AIO core will
  74 * not ask the method again -- ki_retry must ensure forward progress.
  75 * aio_complete() must be called once and only once in the future, multiple
  76 * calls may result in undefined behaviour.
  77 *
  78 * If ki_retry returns -EIOCBRETRY it has made a promise that kick_iocb()
  79 * will be called on the kiocb pointer in the future.  This may happen
  80 * through generic helpers that associate kiocb->ki_wait with a wait
  81 * queue head that ki_retry uses via current->io_wait.  It can also happen
  82 * with custom tracking and manual calls to kick_iocb(), though that is
  83 * discouraged.  In either case, kick_iocb() must be called once and only
  84 * once.  ki_retry must ensure forward progress, the AIO core will wait
  85 * indefinitely for kick_iocb() to be called.
  86 */
  87struct kiocb {
  88        struct list_head        ki_run_list;
  89        unsigned long           ki_flags;
  90        int                     ki_users;
  91        unsigned                ki_key;         /* id of this request */
  92
  93        struct file             *ki_filp;
  94        struct kioctx           *ki_ctx;        /* may be NULL for sync ops */
  95        int                     (*ki_cancel)(struct kiocb *, struct io_event *);
  96        ssize_t                 (*ki_retry)(struct kiocb *);
  97        void                    (*ki_dtor)(struct kiocb *);
  98
  99        union {
 100                void __user             *user;
 101                struct task_struct      *tsk;
 102        } ki_obj;
 103
 104        __u64                   ki_user_data;   /* user's data for completion */
 105        loff_t                  ki_pos;
 106
 107        void                    *private;
 108        /* State that we remember to be able to restart/retry  */
 109        unsigned short          ki_opcode;
 110        size_t                  ki_nbytes;      /* copy of iocb->aio_nbytes */
 111        char                    __user *ki_buf; /* remaining iocb->aio_buf */
 112        size_t                  ki_left;        /* remaining bytes */
 113        struct iovec            ki_inline_vec;  /* inline vector */
 114        struct iovec            *ki_iovec;
 115        unsigned long           ki_nr_segs;
 116        unsigned long           ki_cur_seg;
 117
 118        struct list_head        ki_list;        /* the aio core uses this
 119                                                 * for cancellation */
 120        struct list_head        ki_batch;       /* batch allocation */
 121
 122        /*
 123         * If the aio_resfd field of the userspace iocb is not zero,
 124         * this is the underlying eventfd context to deliver events to.
 125         */
 126        struct eventfd_ctx      *ki_eventfd;
 127};
 128
 129static inline bool is_sync_kiocb(struct kiocb *kiocb)
 130{
 131        return kiocb->ki_key == KIOCB_SYNC_KEY;
 132}
 133
 134static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
 135{
 136        *kiocb = (struct kiocb) {
 137                        .ki_users = 1,
 138                        .ki_key = KIOCB_SYNC_KEY,
 139                        .ki_filp = filp,
 140                        .ki_obj.tsk = current,
 141                };
 142}
 143
 144#define AIO_RING_MAGIC                  0xa10a10a1
 145#define AIO_RING_COMPAT_FEATURES        1
 146#define AIO_RING_INCOMPAT_FEATURES      0
 147struct aio_ring {
 148        unsigned        id;     /* kernel internal index number */
 149        unsigned        nr;     /* number of io_events */
 150        unsigned        head;
 151        unsigned        tail;
 152
 153        unsigned        magic;
 154        unsigned        compat_features;
 155        unsigned        incompat_features;
 156        unsigned        header_length;  /* size of aio_ring */
 157
 158
 159        struct io_event         io_events[0];
 160}; /* 128 bytes + ring size */
 161
 162#define AIO_RING_PAGES  8
 163struct aio_ring_info {
 164        unsigned long           mmap_base;
 165        unsigned long           mmap_size;
 166
 167        struct page             **ring_pages;
 168        spinlock_t              ring_lock;
 169        long                    nr_pages;
 170
 171        unsigned                nr, tail;
 172
 173        struct page             *internal_pages[AIO_RING_PAGES];
 174};
 175
 176static inline unsigned aio_ring_avail(struct aio_ring_info *info,
 177                                        struct aio_ring *ring)
 178{
 179        return (ring->head + info->nr - 1 - ring->tail) % info->nr;
 180}
 181
 182struct kioctx {
 183        atomic_t                users;
 184        int                     dead;
 185        struct mm_struct        *mm;
 186
 187        /* This needs improving */
 188        unsigned long           user_id;
 189        struct hlist_node       list;
 190
 191        wait_queue_head_t       wait;
 192
 193        spinlock_t              ctx_lock;
 194
 195        int                     reqs_active;
 196        struct list_head        active_reqs;    /* used for cancellation */
 197        struct list_head        run_list;       /* used for kicked reqs */
 198
 199        /* sys_io_setup currently limits this to an unsigned int */
 200        unsigned                max_reqs;
 201
 202        struct aio_ring_info    ring_info;
 203
 204        struct delayed_work     wq;
 205
 206        struct rcu_head         rcu_head;
 207};
 208
 209/* prototypes */
 210extern unsigned aio_max_size;
 211
 212#ifdef CONFIG_AIO
 213extern ssize_t wait_on_sync_kiocb(struct kiocb *iocb);
 214extern int aio_put_req(struct kiocb *iocb);
 215extern void kick_iocb(struct kiocb *iocb);
 216extern int aio_complete(struct kiocb *iocb, long res, long res2);
 217struct mm_struct;
 218extern void exit_aio(struct mm_struct *mm);
 219extern long do_io_submit(aio_context_t ctx_id, long nr,
 220                         struct iocb __user *__user *iocbpp, bool compat);
 221#else
 222static inline ssize_t wait_on_sync_kiocb(struct kiocb *iocb) { return 0; }
 223static inline int aio_put_req(struct kiocb *iocb) { return 0; }
 224static inline void kick_iocb(struct kiocb *iocb) { }
 225static inline int aio_complete(struct kiocb *iocb, long res, long res2) { return 0; }
 226struct mm_struct;
 227static inline void exit_aio(struct mm_struct *mm) { }
 228static inline long do_io_submit(aio_context_t ctx_id, long nr,
 229                                struct iocb __user * __user *iocbpp,
 230                                bool compat) { return 0; }
 231#endif /* CONFIG_AIO */
 232
 233static inline struct kiocb *list_kiocb(struct list_head *h)
 234{
 235        return list_entry(h, struct kiocb, ki_list);
 236}
 237
 238/* for sysctl: */
 239extern unsigned long aio_nr;
 240extern unsigned long aio_max_nr;
 241
 242#endif /* __LINUX__AIO_H */
 243
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