include/linux/aio.h

   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 struct kioctx;
  13 struct kiocb;
  14
  15 #define KIOCB_KEY               0
  16
  17 /*
  18  * We use ki_cancel == KIOCB_CANCELLED to indicate that a kiocb has been either
  19  * cancelled or completed (this makes a certain amount of sense because
  20  * successful cancellation - io_cancel() - does deliver the completion to
  21  * userspace).
  22  *
  23  * And since most things don't implement kiocb cancellation and we'd really like
  24  * kiocb completion to be lockless when possible, we use ki_cancel to
  25  * synchronize cancellation and completion - we only set it to KIOCB_CANCELLED
  26  * with xchg() or cmpxchg(), see batch_complete_aio() and kiocb_cancel().
  27  */
  28 #define KIOCB_CANCELLED         ((void *) (~0ULL))
  29
  30 typedef int (kiocb_cancel_fn)(struct kiocb *, struct io_event *);
  31
  32 /* is there a better place to document function pointer methods? */
  33 /**
  34  * ki_retry     -       iocb forward progress callback
  35  * @kiocb:      The kiocb struct to advance by performing an operation.
  36  *
  37  * This callback is called when the AIO core wants a given AIO operation
  38  * to make forward progress.  The kiocb argument describes the operation
  39  * that is to be performed.  As the operation proceeds, perhaps partially,
  40  * ki_retry is expected to update the kiocb with progress made.  Typically
  41  * ki_retry is set in the AIO core and it itself calls file_operations
  42  * helpers.
  43  *
  44  * ki_retry's return value determines when the AIO operation is completed
  45  * and an event is generated in the AIO event ring.  Except the special
  46  * return values described below, the value that is returned from ki_retry
  47  * is transferred directly into the completion ring as the operation's
  48  * resulting status.  Once this has happened ki_retry *MUST NOT* reference
  49  * the kiocb pointer again.
  50  *
  51  * If ki_retry returns -EIOCBQUEUED it has made a promise that aio_complete()
  52  * will be called on the kiocb pointer in the future.  The AIO core will
  53  * not ask the method again -- ki_retry must ensure forward progress.
  54  * aio_complete() must be called once and only once in the future, multiple
  55  * calls may result in undefined behaviour.
  56  */
  57 struct kiocb {
  58         atomic_t                ki_users;
  59
  60         struct file             *ki_filp;
  61         struct kioctx           *ki_ctx;        /* NULL for sync ops */
  62         kiocb_cancel_fn         *ki_cancel;
  63         ssize_t                 (*ki_retry)(struct kiocb *);
  64         void                    (*ki_dtor)(struct kiocb *);
  65
  66         union {
  67                 void __user             *user;
  68                 struct task_struct      *tsk;
  69         } ki_obj;
  70
  71         __u64                   ki_user_data;   /* user's data for completion */
  72         loff_t                  ki_pos;
  73
  74         void                    *private;
  75         /* State that we remember to be able to restart/retry  */
  76         unsigned short          ki_opcode;
  77         size_t                  ki_nbytes;      /* copy of iocb->aio_nbytes */
  78         char                    __user *ki_buf; /* remaining iocb->aio_buf */
  79         size_t                  ki_left;        /* remaining bytes */
  80         struct iovec            ki_inline_vec;  /* inline vector */
  81         struct iovec            *ki_iovec;
  82         unsigned long           ki_nr_segs;
  83         unsigned long           ki_cur_seg;
  84
  85         struct list_head        ki_list;        /* the aio core uses this
  86                                                  * for cancellation */
  87
  88         /*
  89          * If the aio_resfd field of the userspace iocb is not zero,
  90          * this is the underlying eventfd context to deliver events to.
  91          */
  92         struct eventfd_ctx      *ki_eventfd;
  93 };
  94
  95 static inline bool is_sync_kiocb(struct kiocb *kiocb)
  96 {
  97         return kiocb->ki_ctx == NULL;
  98 }
  99
 100 static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
 101 {
 102         *kiocb = (struct kiocb) {
 103                         .ki_users = ATOMIC_INIT(1),
 104                         .ki_ctx = NULL,
 105                         .ki_filp = filp,
 106                         .ki_obj.tsk = current,
 107                 };
 108 }
 109
 110 /* prototypes */
 111 #ifdef CONFIG_AIO
 112 extern ssize_t wait_on_sync_kiocb(struct kiocb *iocb);
 113 extern void aio_put_req(struct kiocb *iocb);
 114 extern void aio_complete(struct kiocb *iocb, long res, long res2);
 115 struct mm_struct;
 116 extern void exit_aio(struct mm_struct *mm);
 117 extern long do_io_submit(aio_context_t ctx_id, long nr,
 118                          struct iocb __user *__user *iocbpp, bool compat);
 119 void kiocb_set_cancel_fn(struct kiocb *req, kiocb_cancel_fn *cancel);
 120 #else
 121 static inline ssize_t wait_on_sync_kiocb(struct kiocb *iocb) { return 0; }
 122 static inline void aio_put_req(struct kiocb *iocb) { }
 123 static inline void aio_complete(struct kiocb *iocb, long res, long res2) { }
 124 struct mm_struct;
 125 static inline void exit_aio(struct mm_struct *mm) { }
 126 static inline long do_io_submit(aio_context_t ctx_id, long nr,
 127                                 struct iocb __user * __user *iocbpp,
 128                                 bool compat) { return 0; }
 129 static inline void kiocb_set_cancel_fn(struct kiocb *req,
 130                                        kiocb_cancel_fn *cancel) { }
 131 #endif /* CONFIG_AIO */
 132
 133 static inline struct kiocb *list_kiocb(struct list_head *h)
 134 {
 135         return list_entry(h, struct kiocb, ki_list);
 136 }
 137
 138 /* for sysctl: */
 139 extern unsigned long aio_nr;
 140 extern unsigned long aio_max_nr;
 141
 142 #endif /* __LINUX__AIO_H */