![Kent Overstreet](/assets/img/avatar_default.png)
Cancelling kiocbs requires adding them to a per kioctx linked list, which is one of the few things we need to take the kioctx lock for in the fast path. But most kiocbs can't be cancelled - so if we just do this lazily, we can avoid quite a bit of locking overhead. While we're at it, instead of using a flag bit switch to using ki_cancel itself to indicate that a kiocb has been cancelled/completed. This lets us get rid of ki_flags entirely. [akpm@linux-foundation.org: remove buggy BUG()] Signed-off-by: Kent Overstreet <koverstreet@google.com> Cc: Zach Brown <zab@redhat.com> Cc: Felipe Balbi <balbi@ti.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Joel Becker <jlbec@evilplan.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Jens Axboe <axboe@kernel.dk> Cc: Asai Thambi S P <asamymuthupa@micron.com> Cc: Selvan Mani <smani@micron.com> Cc: Sam Bradshaw <sbradshaw@micron.com> Cc: Jeff Moyer <jmoyer@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Benjamin LaHaise <bcrl@kvack.org> Reviewed-by: "Theodore Ts'o" <tytso@mit.edu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
145 lines
4.8 KiB
C
145 lines
4.8 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 <linux/uio.h>
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#include <linux/rcupdate.h>
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#include <linux/atomic.h>
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struct kioctx;
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struct kiocb;
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#define KIOCB_SYNC_KEY (~0U)
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/*
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* We use ki_cancel == KIOCB_CANCELLED to indicate that a kiocb has been either
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* cancelled or completed (this makes a certain amount of sense because
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* successful cancellation - io_cancel() - does deliver the completion to
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* userspace).
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*
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* And since most things don't implement kiocb cancellation and we'd really like
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* kiocb completion to be lockless when possible, we use ki_cancel to
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* synchronize cancellation and completion - we only set it to KIOCB_CANCELLED
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* with xchg() or cmpxchg(), see batch_complete_aio() and kiocb_cancel().
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*/
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#define KIOCB_CANCELLED ((void *) (~0ULL))
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typedef int (kiocb_cancel_fn)(struct kiocb *, struct io_event *);
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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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struct kiocb {
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atomic_t 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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kiocb_cancel_fn *ki_cancel;
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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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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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struct iovec ki_inline_vec; /* inline vector */
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struct iovec *ki_iovec;
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unsigned long ki_nr_segs;
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unsigned long ki_cur_seg;
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struct list_head ki_list; /* the aio core uses this
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* for cancellation */
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struct list_head ki_batch; /* batch allocation */
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/*
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* If the aio_resfd field of the userspace iocb is not zero,
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* this is the underlying eventfd context to deliver events to.
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*/
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struct eventfd_ctx *ki_eventfd;
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};
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static inline bool is_sync_kiocb(struct kiocb *kiocb)
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{
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return kiocb->ki_key == KIOCB_SYNC_KEY;
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}
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static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
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{
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*kiocb = (struct kiocb) {
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.ki_users = ATOMIC_INIT(1),
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.ki_key = KIOCB_SYNC_KEY,
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.ki_filp = filp,
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.ki_obj.tsk = current,
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};
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}
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/* prototypes */
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#ifdef CONFIG_AIO
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extern ssize_t wait_on_sync_kiocb(struct kiocb *iocb);
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extern void aio_put_req(struct kiocb *iocb);
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extern void aio_complete(struct kiocb *iocb, long res, long res2);
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struct mm_struct;
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extern void exit_aio(struct mm_struct *mm);
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extern long do_io_submit(aio_context_t ctx_id, long nr,
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struct iocb __user *__user *iocbpp, bool compat);
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void kiocb_set_cancel_fn(struct kiocb *req, kiocb_cancel_fn *cancel);
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#else
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static inline ssize_t wait_on_sync_kiocb(struct kiocb *iocb) { return 0; }
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static inline void aio_put_req(struct kiocb *iocb) { }
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static inline void aio_complete(struct kiocb *iocb, long res, long res2) { }
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struct mm_struct;
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static inline void exit_aio(struct mm_struct *mm) { }
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static inline long do_io_submit(aio_context_t ctx_id, long nr,
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struct iocb __user * __user *iocbpp,
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bool compat) { return 0; }
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static inline void kiocb_set_cancel_fn(struct kiocb *req,
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kiocb_cancel_fn *cancel) { }
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#endif /* CONFIG_AIO */
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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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