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![Benjamin LaHaise](/assets/img/avatar_default.png)
Reorder members of the kiocb structure to make sync kiocb setup faster. By setting the elements sequentially, the write combining buffers on the CPU are able to combine the writes into a single burst, which results in fewer cache cycles being consumed, freeing them up for other code. This results in a 10-20KB/s[*] increase on the bw_unix part of LMbench on my test system. * The improvement varies based on what other patches are in the system, as there are a number of bottlenecks, so this number is not absolutely accurate. Signed-off-by: Benjamin LaHaise <benjamin.c.lahaise@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
250 lines
7.9 KiB
C
250 lines
7.9 KiB
C
#ifndef __LINUX__AIO_H
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#define __LINUX__AIO_H
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#include <linux/list.h>
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#include <linux/workqueue.h>
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#include <linux/aio_abi.h>
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#include <asm/atomic.h>
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#define AIO_MAXSEGS 4
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#define AIO_KIOGRP_NR_ATOMIC 8
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struct kioctx;
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/* Notes on cancelling a kiocb:
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* If a kiocb is cancelled, aio_complete may return 0 to indicate
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* that cancel has not yet disposed of the kiocb. All cancel
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* operations *must* call aio_put_req to dispose of the kiocb
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* to guard against races with the completion code.
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*/
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#define KIOCB_C_CANCELLED 0x01
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#define KIOCB_C_COMPLETE 0x02
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#define KIOCB_SYNC_KEY (~0U)
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/* ki_flags bits */
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/*
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* This may be used for cancel/retry serialization in the future, but
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* for now it's unused and we probably don't want modules to even
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* think they can use it.
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*/
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/* #define KIF_LOCKED 0 */
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#define KIF_KICKED 1
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#define KIF_CANCELLED 2
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#define kiocbTryLock(iocb) test_and_set_bit(KIF_LOCKED, &(iocb)->ki_flags)
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#define kiocbTryKick(iocb) test_and_set_bit(KIF_KICKED, &(iocb)->ki_flags)
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#define kiocbSetLocked(iocb) set_bit(KIF_LOCKED, &(iocb)->ki_flags)
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#define kiocbSetKicked(iocb) set_bit(KIF_KICKED, &(iocb)->ki_flags)
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#define kiocbSetCancelled(iocb) set_bit(KIF_CANCELLED, &(iocb)->ki_flags)
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#define kiocbClearLocked(iocb) clear_bit(KIF_LOCKED, &(iocb)->ki_flags)
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#define kiocbClearKicked(iocb) clear_bit(KIF_KICKED, &(iocb)->ki_flags)
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#define kiocbClearCancelled(iocb) clear_bit(KIF_CANCELLED, &(iocb)->ki_flags)
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#define kiocbIsLocked(iocb) test_bit(KIF_LOCKED, &(iocb)->ki_flags)
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#define kiocbIsKicked(iocb) test_bit(KIF_KICKED, &(iocb)->ki_flags)
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#define kiocbIsCancelled(iocb) test_bit(KIF_CANCELLED, &(iocb)->ki_flags)
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/* is there a better place to document function pointer methods? */
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/**
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* ki_retry - iocb forward progress callback
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* @kiocb: The kiocb struct to advance by performing an operation.
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*
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* This callback is called when the AIO core wants a given AIO operation
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* to make forward progress. The kiocb argument describes the operation
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* that is to be performed. As the operation proceeds, perhaps partially,
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* ki_retry is expected to update the kiocb with progress made. Typically
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* ki_retry is set in the AIO core and it itself calls file_operations
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* helpers.
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*
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* ki_retry's return value determines when the AIO operation is completed
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* and an event is generated in the AIO event ring. Except the special
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* return values described below, the value that is returned from ki_retry
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* is transferred directly into the completion ring as the operation's
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* resulting status. Once this has happened ki_retry *MUST NOT* reference
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* the kiocb pointer again.
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*
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* If ki_retry returns -EIOCBQUEUED it has made a promise that aio_complete()
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* will be called on the kiocb pointer in the future. The AIO core will
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* not ask the method again -- ki_retry must ensure forward progress.
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* aio_complete() must be called once and only once in the future, multiple
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* calls may result in undefined behaviour.
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*
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* If ki_retry returns -EIOCBRETRY it has made a promise that kick_iocb()
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* will be called on the kiocb pointer in the future. This may happen
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* through generic helpers that associate kiocb->ki_wait with a wait
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* queue head that ki_retry uses via current->io_wait. It can also happen
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* with custom tracking and manual calls to kick_iocb(), though that is
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* discouraged. In either case, kick_iocb() must be called once and only
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* once. ki_retry must ensure forward progress, the AIO core will wait
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* indefinitely for kick_iocb() to be called.
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*/
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struct kiocb {
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struct list_head ki_run_list;
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long ki_flags;
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int ki_users;
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unsigned ki_key; /* id of this request */
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struct file *ki_filp;
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struct kioctx *ki_ctx; /* may be NULL for sync ops */
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int (*ki_cancel)(struct kiocb *, struct io_event *);
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ssize_t (*ki_retry)(struct kiocb *);
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void (*ki_dtor)(struct kiocb *);
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union {
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void __user *user;
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struct task_struct *tsk;
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} ki_obj;
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__u64 ki_user_data; /* user's data for completion */
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wait_queue_t ki_wait;
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loff_t ki_pos;
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void *private;
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/* State that we remember to be able to restart/retry */
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unsigned short ki_opcode;
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size_t ki_nbytes; /* copy of iocb->aio_nbytes */
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char __user *ki_buf; /* remaining iocb->aio_buf */
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size_t ki_left; /* remaining bytes */
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long ki_retried; /* just for testing */
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long ki_kicked; /* just for testing */
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long ki_queued; /* just for testing */
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struct list_head ki_list; /* the aio core uses this
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* for cancellation */
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};
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#define is_sync_kiocb(iocb) ((iocb)->ki_key == KIOCB_SYNC_KEY)
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#define init_sync_kiocb(x, filp) \
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do { \
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struct task_struct *tsk = current; \
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(x)->ki_flags = 0; \
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(x)->ki_users = 1; \
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(x)->ki_key = KIOCB_SYNC_KEY; \
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(x)->ki_filp = (filp); \
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(x)->ki_ctx = NULL; \
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(x)->ki_cancel = NULL; \
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(x)->ki_retry = NULL; \
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(x)->ki_dtor = NULL; \
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(x)->ki_obj.tsk = tsk; \
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(x)->ki_user_data = 0; \
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init_wait((&(x)->ki_wait)); \
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} while (0)
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#define AIO_RING_MAGIC 0xa10a10a1
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#define AIO_RING_COMPAT_FEATURES 1
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#define AIO_RING_INCOMPAT_FEATURES 0
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struct aio_ring {
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unsigned id; /* kernel internal index number */
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unsigned nr; /* number of io_events */
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unsigned head;
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unsigned tail;
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unsigned magic;
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unsigned compat_features;
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unsigned incompat_features;
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unsigned header_length; /* size of aio_ring */
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struct io_event io_events[0];
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}; /* 128 bytes + ring size */
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#define aio_ring_avail(info, ring) (((ring)->head + (info)->nr - 1 - (ring)->tail) % (info)->nr)
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#define AIO_RING_PAGES 8
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struct aio_ring_info {
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unsigned long mmap_base;
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unsigned long mmap_size;
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struct page **ring_pages;
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spinlock_t ring_lock;
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long nr_pages;
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unsigned nr, tail;
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struct page *internal_pages[AIO_RING_PAGES];
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};
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struct kioctx {
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atomic_t users;
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int dead;
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struct mm_struct *mm;
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/* This needs improving */
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unsigned long user_id;
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struct kioctx *next;
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wait_queue_head_t wait;
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spinlock_t ctx_lock;
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int reqs_active;
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struct list_head active_reqs; /* used for cancellation */
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struct list_head run_list; /* used for kicked reqs */
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/* sys_io_setup currently limits this to an unsigned int */
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unsigned max_reqs;
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struct aio_ring_info ring_info;
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struct work_struct wq;
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};
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/* prototypes */
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extern unsigned aio_max_size;
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extern ssize_t FASTCALL(wait_on_sync_kiocb(struct kiocb *iocb));
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extern int FASTCALL(aio_put_req(struct kiocb *iocb));
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extern void FASTCALL(kick_iocb(struct kiocb *iocb));
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extern int FASTCALL(aio_complete(struct kiocb *iocb, long res, long res2));
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extern void FASTCALL(__put_ioctx(struct kioctx *ctx));
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struct mm_struct;
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extern void FASTCALL(exit_aio(struct mm_struct *mm));
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extern struct kioctx *lookup_ioctx(unsigned long ctx_id);
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extern int FASTCALL(io_submit_one(struct kioctx *ctx,
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struct iocb __user *user_iocb, struct iocb *iocb));
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/* semi private, but used by the 32bit emulations: */
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struct kioctx *lookup_ioctx(unsigned long ctx_id);
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int FASTCALL(io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
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struct iocb *iocb));
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#define get_ioctx(kioctx) do { \
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BUG_ON(unlikely(atomic_read(&(kioctx)->users) <= 0)); \
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atomic_inc(&(kioctx)->users); \
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} while (0)
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#define put_ioctx(kioctx) do { \
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BUG_ON(unlikely(atomic_read(&(kioctx)->users) <= 0)); \
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if (unlikely(atomic_dec_and_test(&(kioctx)->users))) \
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__put_ioctx(kioctx); \
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} while (0)
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#define in_aio() !is_sync_wait(current->io_wait)
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/* may be used for debugging */
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#define warn_if_async() \
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do { \
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if (in_aio()) { \
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printk(KERN_ERR "%s(%s:%d) called in async context!\n", \
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__FUNCTION__, __FILE__, __LINE__); \
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dump_stack(); \
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} \
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} while (0)
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#define io_wait_to_kiocb(wait) container_of(wait, struct kiocb, ki_wait)
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#define is_retried_kiocb(iocb) ((iocb)->ki_retried > 1)
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#include <linux/aio_abi.h>
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static inline struct kiocb *list_kiocb(struct list_head *h)
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{
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return list_entry(h, struct kiocb, ki_list);
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}
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/* for sysctl: */
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extern unsigned long aio_nr;
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extern unsigned long aio_max_nr;
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#endif /* __LINUX__AIO_H */
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