2 * An async IO implementation for Linux
3 * Written by Benjamin LaHaise <bcrl@kvack.org>
5 * Implements an efficient asynchronous io interface.
7 * Copyright 2000, 2001, 2002 Red Hat, Inc. All Rights Reserved.
8 * Copyright 2018 Christoph Hellwig.
10 * See ../COPYING for licensing terms.
12 #define pr_fmt(fmt) "%s: " fmt, __func__
14 #include <linux/kernel.h>
15 #include <linux/init.h>
16 #include <linux/errno.h>
17 #include <linux/time.h>
18 #include <linux/aio_abi.h>
19 #include <linux/export.h>
20 #include <linux/syscalls.h>
21 #include <linux/backing-dev.h>
22 #include <linux/refcount.h>
23 #include <linux/uio.h>
25 #include <linux/sched/signal.h>
27 #include <linux/file.h>
29 #include <linux/mman.h>
30 #include <linux/percpu.h>
31 #include <linux/slab.h>
32 #include <linux/timer.h>
33 #include <linux/aio.h>
34 #include <linux/highmem.h>
35 #include <linux/workqueue.h>
36 #include <linux/security.h>
37 #include <linux/eventfd.h>
38 #include <linux/blkdev.h>
39 #include <linux/compat.h>
40 #include <linux/migrate.h>
41 #include <linux/ramfs.h>
42 #include <linux/percpu-refcount.h>
43 #include <linux/mount.h>
44 #include <linux/pseudo_fs.h>
46 #include <linux/uaccess.h>
47 #include <linux/nospec.h>
53 #define AIO_RING_MAGIC 0xa10a10a1
54 #define AIO_RING_COMPAT_FEATURES 1
55 #define AIO_RING_INCOMPAT_FEATURES 0
57 unsigned id
; /* kernel internal index number */
58 unsigned nr
; /* number of io_events */
59 unsigned head
; /* Written to by userland or under ring_lock
60 * mutex by aio_read_events_ring(). */
64 unsigned compat_features
;
65 unsigned incompat_features
;
66 unsigned header_length
; /* size of aio_ring */
69 struct io_event io_events
[];
70 }; /* 128 bytes + ring size */
73 * Plugging is meant to work with larger batches of IOs. If we don't
74 * have more than the below, then don't bother setting up a plug.
76 #define AIO_PLUG_THRESHOLD 2
78 #define AIO_RING_PAGES 8
83 struct kioctx __rcu
*table
[];
87 unsigned reqs_available
;
91 struct completion comp
;
96 struct percpu_ref users
;
99 struct percpu_ref reqs
;
101 unsigned long user_id
;
103 struct __percpu kioctx_cpu
*cpu
;
106 * For percpu reqs_available, number of slots we move to/from global
111 * This is what userspace passed to io_setup(), it's not used for
112 * anything but counting against the global max_reqs quota.
114 * The real limit is nr_events - 1, which will be larger (see
119 /* Size of ringbuffer, in units of struct io_event */
122 unsigned long mmap_base
;
123 unsigned long mmap_size
;
125 struct page
**ring_pages
;
128 struct rcu_work free_rwork
; /* see free_ioctx() */
131 * signals when all in-flight requests are done
133 struct ctx_rq_wait
*rq_wait
;
137 * This counts the number of available slots in the ringbuffer,
138 * so we avoid overflowing it: it's decremented (if positive)
139 * when allocating a kiocb and incremented when the resulting
140 * io_event is pulled off the ringbuffer.
142 * We batch accesses to it with a percpu version.
144 atomic_t reqs_available
;
145 } ____cacheline_aligned_in_smp
;
149 struct list_head active_reqs
; /* used for cancellation */
150 } ____cacheline_aligned_in_smp
;
153 struct mutex ring_lock
;
154 wait_queue_head_t wait
;
155 } ____cacheline_aligned_in_smp
;
159 unsigned completed_events
;
160 spinlock_t completion_lock
;
161 } ____cacheline_aligned_in_smp
;
163 struct page
*internal_pages
[AIO_RING_PAGES
];
164 struct file
*aio_ring_file
;
170 * First field must be the file pointer in all the
171 * iocb unions! See also 'struct kiocb' in <linux/fs.h>
175 struct work_struct work
;
182 struct wait_queue_head
*head
;
186 bool work_need_resched
;
187 struct wait_queue_entry wait
;
188 struct work_struct work
;
192 * NOTE! Each of the iocb union members has the file pointer
193 * as the first entry in their struct definition. So you can
194 * access the file pointer through any of the sub-structs,
195 * or directly as just 'ki_filp' in this struct.
199 struct file
*ki_filp
;
201 struct fsync_iocb fsync
;
202 struct poll_iocb poll
;
205 struct kioctx
*ki_ctx
;
206 kiocb_cancel_fn
*ki_cancel
;
208 struct io_event ki_res
;
210 struct list_head ki_list
; /* the aio core uses this
211 * for cancellation */
212 refcount_t ki_refcnt
;
215 * If the aio_resfd field of the userspace iocb is not zero,
216 * this is the underlying eventfd context to deliver events to.
218 struct eventfd_ctx
*ki_eventfd
;
221 /*------ sysctl variables----*/
222 static DEFINE_SPINLOCK(aio_nr_lock
);
223 static unsigned long aio_nr
; /* current system wide number of aio requests */
224 static unsigned long aio_max_nr
= 0x10000; /* system wide maximum number of aio requests */
225 /*----end sysctl variables---*/
227 static struct ctl_table aio_sysctls
[] = {
229 .procname
= "aio-nr",
231 .maxlen
= sizeof(aio_nr
),
233 .proc_handler
= proc_doulongvec_minmax
,
236 .procname
= "aio-max-nr",
238 .maxlen
= sizeof(aio_max_nr
),
240 .proc_handler
= proc_doulongvec_minmax
,
245 static void __init
aio_sysctl_init(void)
247 register_sysctl_init("fs", aio_sysctls
);
250 #define aio_sysctl_init() do { } while (0)
253 static struct kmem_cache
*kiocb_cachep
;
254 static struct kmem_cache
*kioctx_cachep
;
256 static struct vfsmount
*aio_mnt
;
258 static const struct file_operations aio_ring_fops
;
259 static const struct address_space_operations aio_ctx_aops
;
261 static struct file
*aio_private_file(struct kioctx
*ctx
, loff_t nr_pages
)
264 struct inode
*inode
= alloc_anon_inode(aio_mnt
->mnt_sb
);
266 return ERR_CAST(inode
);
268 inode
->i_mapping
->a_ops
= &aio_ctx_aops
;
269 inode
->i_mapping
->private_data
= ctx
;
270 inode
->i_size
= PAGE_SIZE
* nr_pages
;
272 file
= alloc_file_pseudo(inode
, aio_mnt
, "[aio]",
273 O_RDWR
, &aio_ring_fops
);
279 static int aio_init_fs_context(struct fs_context
*fc
)
281 if (!init_pseudo(fc
, AIO_RING_MAGIC
))
283 fc
->s_iflags
|= SB_I_NOEXEC
;
288 * Creates the slab caches used by the aio routines, panic on
289 * failure as this is done early during the boot sequence.
291 static int __init
aio_setup(void)
293 static struct file_system_type aio_fs
= {
295 .init_fs_context
= aio_init_fs_context
,
296 .kill_sb
= kill_anon_super
,
298 aio_mnt
= kern_mount(&aio_fs
);
300 panic("Failed to create aio fs mount.");
302 kiocb_cachep
= KMEM_CACHE(aio_kiocb
, SLAB_HWCACHE_ALIGN
|SLAB_PANIC
);
303 kioctx_cachep
= KMEM_CACHE(kioctx
,SLAB_HWCACHE_ALIGN
|SLAB_PANIC
);
307 __initcall(aio_setup
);
309 static void put_aio_ring_file(struct kioctx
*ctx
)
311 struct file
*aio_ring_file
= ctx
->aio_ring_file
;
312 struct address_space
*i_mapping
;
315 truncate_setsize(file_inode(aio_ring_file
), 0);
317 /* Prevent further access to the kioctx from migratepages */
318 i_mapping
= aio_ring_file
->f_mapping
;
319 spin_lock(&i_mapping
->private_lock
);
320 i_mapping
->private_data
= NULL
;
321 ctx
->aio_ring_file
= NULL
;
322 spin_unlock(&i_mapping
->private_lock
);
328 static void aio_free_ring(struct kioctx
*ctx
)
332 /* Disconnect the kiotx from the ring file. This prevents future
333 * accesses to the kioctx from page migration.
335 put_aio_ring_file(ctx
);
337 for (i
= 0; i
< ctx
->nr_pages
; i
++) {
339 pr_debug("pid(%d) [%d] page->count=%d\n", current
->pid
, i
,
340 page_count(ctx
->ring_pages
[i
]));
341 page
= ctx
->ring_pages
[i
];
344 ctx
->ring_pages
[i
] = NULL
;
348 if (ctx
->ring_pages
&& ctx
->ring_pages
!= ctx
->internal_pages
) {
349 kfree(ctx
->ring_pages
);
350 ctx
->ring_pages
= NULL
;
354 static int aio_ring_mremap(struct vm_area_struct
*vma
)
356 struct file
*file
= vma
->vm_file
;
357 struct mm_struct
*mm
= vma
->vm_mm
;
358 struct kioctx_table
*table
;
359 int i
, res
= -EINVAL
;
361 spin_lock(&mm
->ioctx_lock
);
363 table
= rcu_dereference(mm
->ioctx_table
);
364 for (i
= 0; i
< table
->nr
; i
++) {
367 ctx
= rcu_dereference(table
->table
[i
]);
368 if (ctx
&& ctx
->aio_ring_file
== file
) {
369 if (!atomic_read(&ctx
->dead
)) {
370 ctx
->user_id
= ctx
->mmap_base
= vma
->vm_start
;
378 spin_unlock(&mm
->ioctx_lock
);
382 static const struct vm_operations_struct aio_ring_vm_ops
= {
383 .mremap
= aio_ring_mremap
,
384 #if IS_ENABLED(CONFIG_MMU)
385 .fault
= filemap_fault
,
386 .map_pages
= filemap_map_pages
,
387 .page_mkwrite
= filemap_page_mkwrite
,
391 static int aio_ring_mmap(struct file
*file
, struct vm_area_struct
*vma
)
393 vma
->vm_flags
|= VM_DONTEXPAND
;
394 vma
->vm_ops
= &aio_ring_vm_ops
;
398 static const struct file_operations aio_ring_fops
= {
399 .mmap
= aio_ring_mmap
,
402 #if IS_ENABLED(CONFIG_MIGRATION)
403 static int aio_migratepage(struct address_space
*mapping
, struct page
*new,
404 struct page
*old
, enum migrate_mode mode
)
412 * We cannot support the _NO_COPY case here, because copy needs to
413 * happen under the ctx->completion_lock. That does not work with the
414 * migration workflow of MIGRATE_SYNC_NO_COPY.
416 if (mode
== MIGRATE_SYNC_NO_COPY
)
421 /* mapping->private_lock here protects against the kioctx teardown. */
422 spin_lock(&mapping
->private_lock
);
423 ctx
= mapping
->private_data
;
429 /* The ring_lock mutex. The prevents aio_read_events() from writing
430 * to the ring's head, and prevents page migration from mucking in
431 * a partially initialized kiotx.
433 if (!mutex_trylock(&ctx
->ring_lock
)) {
439 if (idx
< (pgoff_t
)ctx
->nr_pages
) {
440 /* Make sure the old page hasn't already been changed */
441 if (ctx
->ring_pages
[idx
] != old
)
449 /* Writeback must be complete */
450 BUG_ON(PageWriteback(old
));
453 rc
= migrate_page_move_mapping(mapping
, new, old
, 1);
454 if (rc
!= MIGRATEPAGE_SUCCESS
) {
459 /* Take completion_lock to prevent other writes to the ring buffer
460 * while the old page is copied to the new. This prevents new
461 * events from being lost.
463 spin_lock_irqsave(&ctx
->completion_lock
, flags
);
464 migrate_page_copy(new, old
);
465 BUG_ON(ctx
->ring_pages
[idx
] != old
);
466 ctx
->ring_pages
[idx
] = new;
467 spin_unlock_irqrestore(&ctx
->completion_lock
, flags
);
469 /* The old page is no longer accessible. */
473 mutex_unlock(&ctx
->ring_lock
);
475 spin_unlock(&mapping
->private_lock
);
480 static const struct address_space_operations aio_ctx_aops
= {
481 .dirty_folio
= noop_dirty_folio
,
482 #if IS_ENABLED(CONFIG_MIGRATION)
483 .migratepage
= aio_migratepage
,
487 static int aio_setup_ring(struct kioctx
*ctx
, unsigned int nr_events
)
489 struct aio_ring
*ring
;
490 struct mm_struct
*mm
= current
->mm
;
491 unsigned long size
, unused
;
496 /* Compensate for the ring buffer's head/tail overlap entry */
497 nr_events
+= 2; /* 1 is required, 2 for good luck */
499 size
= sizeof(struct aio_ring
);
500 size
+= sizeof(struct io_event
) * nr_events
;
502 nr_pages
= PFN_UP(size
);
506 file
= aio_private_file(ctx
, nr_pages
);
508 ctx
->aio_ring_file
= NULL
;
512 ctx
->aio_ring_file
= file
;
513 nr_events
= (PAGE_SIZE
* nr_pages
- sizeof(struct aio_ring
))
514 / sizeof(struct io_event
);
516 ctx
->ring_pages
= ctx
->internal_pages
;
517 if (nr_pages
> AIO_RING_PAGES
) {
518 ctx
->ring_pages
= kcalloc(nr_pages
, sizeof(struct page
*),
520 if (!ctx
->ring_pages
) {
521 put_aio_ring_file(ctx
);
526 for (i
= 0; i
< nr_pages
; i
++) {
528 page
= find_or_create_page(file
->f_mapping
,
529 i
, GFP_HIGHUSER
| __GFP_ZERO
);
532 pr_debug("pid(%d) page[%d]->count=%d\n",
533 current
->pid
, i
, page_count(page
));
534 SetPageUptodate(page
);
537 ctx
->ring_pages
[i
] = page
;
541 if (unlikely(i
!= nr_pages
)) {
546 ctx
->mmap_size
= nr_pages
* PAGE_SIZE
;
547 pr_debug("attempting mmap of %lu bytes\n", ctx
->mmap_size
);
549 if (mmap_write_lock_killable(mm
)) {
555 ctx
->mmap_base
= do_mmap(ctx
->aio_ring_file
, 0, ctx
->mmap_size
,
556 PROT_READ
| PROT_WRITE
,
557 MAP_SHARED
, 0, &unused
, NULL
);
558 mmap_write_unlock(mm
);
559 if (IS_ERR((void *)ctx
->mmap_base
)) {
565 pr_debug("mmap address: 0x%08lx\n", ctx
->mmap_base
);
567 ctx
->user_id
= ctx
->mmap_base
;
568 ctx
->nr_events
= nr_events
; /* trusted copy */
570 ring
= kmap_atomic(ctx
->ring_pages
[0]);
571 ring
->nr
= nr_events
; /* user copy */
573 ring
->head
= ring
->tail
= 0;
574 ring
->magic
= AIO_RING_MAGIC
;
575 ring
->compat_features
= AIO_RING_COMPAT_FEATURES
;
576 ring
->incompat_features
= AIO_RING_INCOMPAT_FEATURES
;
577 ring
->header_length
= sizeof(struct aio_ring
);
579 flush_dcache_page(ctx
->ring_pages
[0]);
584 #define AIO_EVENTS_PER_PAGE (PAGE_SIZE / sizeof(struct io_event))
585 #define AIO_EVENTS_FIRST_PAGE ((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event))
586 #define AIO_EVENTS_OFFSET (AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE)
588 void kiocb_set_cancel_fn(struct kiocb
*iocb
, kiocb_cancel_fn
*cancel
)
590 struct aio_kiocb
*req
= container_of(iocb
, struct aio_kiocb
, rw
);
591 struct kioctx
*ctx
= req
->ki_ctx
;
594 if (WARN_ON_ONCE(!list_empty(&req
->ki_list
)))
597 spin_lock_irqsave(&ctx
->ctx_lock
, flags
);
598 list_add_tail(&req
->ki_list
, &ctx
->active_reqs
);
599 req
->ki_cancel
= cancel
;
600 spin_unlock_irqrestore(&ctx
->ctx_lock
, flags
);
602 EXPORT_SYMBOL(kiocb_set_cancel_fn
);
605 * free_ioctx() should be RCU delayed to synchronize against the RCU
606 * protected lookup_ioctx() and also needs process context to call
607 * aio_free_ring(). Use rcu_work.
609 static void free_ioctx(struct work_struct
*work
)
611 struct kioctx
*ctx
= container_of(to_rcu_work(work
), struct kioctx
,
613 pr_debug("freeing %p\n", ctx
);
616 free_percpu(ctx
->cpu
);
617 percpu_ref_exit(&ctx
->reqs
);
618 percpu_ref_exit(&ctx
->users
);
619 kmem_cache_free(kioctx_cachep
, ctx
);
622 static void free_ioctx_reqs(struct percpu_ref
*ref
)
624 struct kioctx
*ctx
= container_of(ref
, struct kioctx
, reqs
);
626 /* At this point we know that there are no any in-flight requests */
627 if (ctx
->rq_wait
&& atomic_dec_and_test(&ctx
->rq_wait
->count
))
628 complete(&ctx
->rq_wait
->comp
);
630 /* Synchronize against RCU protected table->table[] dereferences */
631 INIT_RCU_WORK(&ctx
->free_rwork
, free_ioctx
);
632 queue_rcu_work(system_wq
, &ctx
->free_rwork
);
636 * When this function runs, the kioctx has been removed from the "hash table"
637 * and ctx->users has dropped to 0, so we know no more kiocbs can be submitted -
638 * now it's safe to cancel any that need to be.
640 static void free_ioctx_users(struct percpu_ref
*ref
)
642 struct kioctx
*ctx
= container_of(ref
, struct kioctx
, users
);
643 struct aio_kiocb
*req
;
645 spin_lock_irq(&ctx
->ctx_lock
);
647 while (!list_empty(&ctx
->active_reqs
)) {
648 req
= list_first_entry(&ctx
->active_reqs
,
649 struct aio_kiocb
, ki_list
);
650 req
->ki_cancel(&req
->rw
);
651 list_del_init(&req
->ki_list
);
654 spin_unlock_irq(&ctx
->ctx_lock
);
656 percpu_ref_kill(&ctx
->reqs
);
657 percpu_ref_put(&ctx
->reqs
);
660 static int ioctx_add_table(struct kioctx
*ctx
, struct mm_struct
*mm
)
663 struct kioctx_table
*table
, *old
;
664 struct aio_ring
*ring
;
666 spin_lock(&mm
->ioctx_lock
);
667 table
= rcu_dereference_raw(mm
->ioctx_table
);
671 for (i
= 0; i
< table
->nr
; i
++)
672 if (!rcu_access_pointer(table
->table
[i
])) {
674 rcu_assign_pointer(table
->table
[i
], ctx
);
675 spin_unlock(&mm
->ioctx_lock
);
677 /* While kioctx setup is in progress,
678 * we are protected from page migration
679 * changes ring_pages by ->ring_lock.
681 ring
= kmap_atomic(ctx
->ring_pages
[0]);
687 new_nr
= (table
? table
->nr
: 1) * 4;
688 spin_unlock(&mm
->ioctx_lock
);
690 table
= kzalloc(struct_size(table
, table
, new_nr
), GFP_KERNEL
);
696 spin_lock(&mm
->ioctx_lock
);
697 old
= rcu_dereference_raw(mm
->ioctx_table
);
700 rcu_assign_pointer(mm
->ioctx_table
, table
);
701 } else if (table
->nr
> old
->nr
) {
702 memcpy(table
->table
, old
->table
,
703 old
->nr
* sizeof(struct kioctx
*));
705 rcu_assign_pointer(mm
->ioctx_table
, table
);
714 static void aio_nr_sub(unsigned nr
)
716 spin_lock(&aio_nr_lock
);
717 if (WARN_ON(aio_nr
- nr
> aio_nr
))
721 spin_unlock(&aio_nr_lock
);
725 * Allocates and initializes an ioctx. Returns an ERR_PTR if it failed.
727 static struct kioctx
*ioctx_alloc(unsigned nr_events
)
729 struct mm_struct
*mm
= current
->mm
;
734 * Store the original nr_events -- what userspace passed to io_setup(),
735 * for counting against the global limit -- before it changes.
737 unsigned int max_reqs
= nr_events
;
740 * We keep track of the number of available ringbuffer slots, to prevent
741 * overflow (reqs_available), and we also use percpu counters for this.
743 * So since up to half the slots might be on other cpu's percpu counters
744 * and unavailable, double nr_events so userspace sees what they
745 * expected: additionally, we move req_batch slots to/from percpu
746 * counters at a time, so make sure that isn't 0:
748 nr_events
= max(nr_events
, num_possible_cpus() * 4);
751 /* Prevent overflows */
752 if (nr_events
> (0x10000000U
/ sizeof(struct io_event
))) {
753 pr_debug("ENOMEM: nr_events too high\n");
754 return ERR_PTR(-EINVAL
);
757 if (!nr_events
|| (unsigned long)max_reqs
> aio_max_nr
)
758 return ERR_PTR(-EAGAIN
);
760 ctx
= kmem_cache_zalloc(kioctx_cachep
, GFP_KERNEL
);
762 return ERR_PTR(-ENOMEM
);
764 ctx
->max_reqs
= max_reqs
;
766 spin_lock_init(&ctx
->ctx_lock
);
767 spin_lock_init(&ctx
->completion_lock
);
768 mutex_init(&ctx
->ring_lock
);
769 /* Protect against page migration throughout kiotx setup by keeping
770 * the ring_lock mutex held until setup is complete. */
771 mutex_lock(&ctx
->ring_lock
);
772 init_waitqueue_head(&ctx
->wait
);
774 INIT_LIST_HEAD(&ctx
->active_reqs
);
776 if (percpu_ref_init(&ctx
->users
, free_ioctx_users
, 0, GFP_KERNEL
))
779 if (percpu_ref_init(&ctx
->reqs
, free_ioctx_reqs
, 0, GFP_KERNEL
))
782 ctx
->cpu
= alloc_percpu(struct kioctx_cpu
);
786 err
= aio_setup_ring(ctx
, nr_events
);
790 atomic_set(&ctx
->reqs_available
, ctx
->nr_events
- 1);
791 ctx
->req_batch
= (ctx
->nr_events
- 1) / (num_possible_cpus() * 4);
792 if (ctx
->req_batch
< 1)
795 /* limit the number of system wide aios */
796 spin_lock(&aio_nr_lock
);
797 if (aio_nr
+ ctx
->max_reqs
> aio_max_nr
||
798 aio_nr
+ ctx
->max_reqs
< aio_nr
) {
799 spin_unlock(&aio_nr_lock
);
803 aio_nr
+= ctx
->max_reqs
;
804 spin_unlock(&aio_nr_lock
);
806 percpu_ref_get(&ctx
->users
); /* io_setup() will drop this ref */
807 percpu_ref_get(&ctx
->reqs
); /* free_ioctx_users() will drop this */
809 err
= ioctx_add_table(ctx
, mm
);
813 /* Release the ring_lock mutex now that all setup is complete. */
814 mutex_unlock(&ctx
->ring_lock
);
816 pr_debug("allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",
817 ctx
, ctx
->user_id
, mm
, ctx
->nr_events
);
821 aio_nr_sub(ctx
->max_reqs
);
823 atomic_set(&ctx
->dead
, 1);
825 vm_munmap(ctx
->mmap_base
, ctx
->mmap_size
);
828 mutex_unlock(&ctx
->ring_lock
);
829 free_percpu(ctx
->cpu
);
830 percpu_ref_exit(&ctx
->reqs
);
831 percpu_ref_exit(&ctx
->users
);
832 kmem_cache_free(kioctx_cachep
, ctx
);
833 pr_debug("error allocating ioctx %d\n", err
);
838 * Cancels all outstanding aio requests on an aio context. Used
839 * when the processes owning a context have all exited to encourage
840 * the rapid destruction of the kioctx.
842 static int kill_ioctx(struct mm_struct
*mm
, struct kioctx
*ctx
,
843 struct ctx_rq_wait
*wait
)
845 struct kioctx_table
*table
;
847 spin_lock(&mm
->ioctx_lock
);
848 if (atomic_xchg(&ctx
->dead
, 1)) {
849 spin_unlock(&mm
->ioctx_lock
);
853 table
= rcu_dereference_raw(mm
->ioctx_table
);
854 WARN_ON(ctx
!= rcu_access_pointer(table
->table
[ctx
->id
]));
855 RCU_INIT_POINTER(table
->table
[ctx
->id
], NULL
);
856 spin_unlock(&mm
->ioctx_lock
);
858 /* free_ioctx_reqs() will do the necessary RCU synchronization */
859 wake_up_all(&ctx
->wait
);
862 * It'd be more correct to do this in free_ioctx(), after all
863 * the outstanding kiocbs have finished - but by then io_destroy
864 * has already returned, so io_setup() could potentially return
865 * -EAGAIN with no ioctxs actually in use (as far as userspace
868 aio_nr_sub(ctx
->max_reqs
);
871 vm_munmap(ctx
->mmap_base
, ctx
->mmap_size
);
874 percpu_ref_kill(&ctx
->users
);
879 * exit_aio: called when the last user of mm goes away. At this point, there is
880 * no way for any new requests to be submited or any of the io_* syscalls to be
881 * called on the context.
883 * There may be outstanding kiocbs, but free_ioctx() will explicitly wait on
886 void exit_aio(struct mm_struct
*mm
)
888 struct kioctx_table
*table
= rcu_dereference_raw(mm
->ioctx_table
);
889 struct ctx_rq_wait wait
;
895 atomic_set(&wait
.count
, table
->nr
);
896 init_completion(&wait
.comp
);
899 for (i
= 0; i
< table
->nr
; ++i
) {
901 rcu_dereference_protected(table
->table
[i
], true);
909 * We don't need to bother with munmap() here - exit_mmap(mm)
910 * is coming and it'll unmap everything. And we simply can't,
911 * this is not necessarily our ->mm.
912 * Since kill_ioctx() uses non-zero ->mmap_size as indicator
913 * that it needs to unmap the area, just set it to 0.
916 kill_ioctx(mm
, ctx
, &wait
);
919 if (!atomic_sub_and_test(skipped
, &wait
.count
)) {
920 /* Wait until all IO for the context are done. */
921 wait_for_completion(&wait
.comp
);
924 RCU_INIT_POINTER(mm
->ioctx_table
, NULL
);
928 static void put_reqs_available(struct kioctx
*ctx
, unsigned nr
)
930 struct kioctx_cpu
*kcpu
;
933 local_irq_save(flags
);
934 kcpu
= this_cpu_ptr(ctx
->cpu
);
935 kcpu
->reqs_available
+= nr
;
937 while (kcpu
->reqs_available
>= ctx
->req_batch
* 2) {
938 kcpu
->reqs_available
-= ctx
->req_batch
;
939 atomic_add(ctx
->req_batch
, &ctx
->reqs_available
);
942 local_irq_restore(flags
);
945 static bool __get_reqs_available(struct kioctx
*ctx
)
947 struct kioctx_cpu
*kcpu
;
951 local_irq_save(flags
);
952 kcpu
= this_cpu_ptr(ctx
->cpu
);
953 if (!kcpu
->reqs_available
) {
954 int old
, avail
= atomic_read(&ctx
->reqs_available
);
957 if (avail
< ctx
->req_batch
)
961 avail
= atomic_cmpxchg(&ctx
->reqs_available
,
962 avail
, avail
- ctx
->req_batch
);
963 } while (avail
!= old
);
965 kcpu
->reqs_available
+= ctx
->req_batch
;
969 kcpu
->reqs_available
--;
971 local_irq_restore(flags
);
975 /* refill_reqs_available
976 * Updates the reqs_available reference counts used for tracking the
977 * number of free slots in the completion ring. This can be called
978 * from aio_complete() (to optimistically update reqs_available) or
979 * from aio_get_req() (the we're out of events case). It must be
980 * called holding ctx->completion_lock.
982 static void refill_reqs_available(struct kioctx
*ctx
, unsigned head
,
985 unsigned events_in_ring
, completed
;
987 /* Clamp head since userland can write to it. */
988 head
%= ctx
->nr_events
;
990 events_in_ring
= tail
- head
;
992 events_in_ring
= ctx
->nr_events
- (head
- tail
);
994 completed
= ctx
->completed_events
;
995 if (events_in_ring
< completed
)
996 completed
-= events_in_ring
;
1003 ctx
->completed_events
-= completed
;
1004 put_reqs_available(ctx
, completed
);
1007 /* user_refill_reqs_available
1008 * Called to refill reqs_available when aio_get_req() encounters an
1009 * out of space in the completion ring.
1011 static void user_refill_reqs_available(struct kioctx
*ctx
)
1013 spin_lock_irq(&ctx
->completion_lock
);
1014 if (ctx
->completed_events
) {
1015 struct aio_ring
*ring
;
1018 /* Access of ring->head may race with aio_read_events_ring()
1019 * here, but that's okay since whether we read the old version
1020 * or the new version, and either will be valid. The important
1021 * part is that head cannot pass tail since we prevent
1022 * aio_complete() from updating tail by holding
1023 * ctx->completion_lock. Even if head is invalid, the check
1024 * against ctx->completed_events below will make sure we do the
1027 ring
= kmap_atomic(ctx
->ring_pages
[0]);
1029 kunmap_atomic(ring
);
1031 refill_reqs_available(ctx
, head
, ctx
->tail
);
1034 spin_unlock_irq(&ctx
->completion_lock
);
1037 static bool get_reqs_available(struct kioctx
*ctx
)
1039 if (__get_reqs_available(ctx
))
1041 user_refill_reqs_available(ctx
);
1042 return __get_reqs_available(ctx
);
1046 * Allocate a slot for an aio request.
1047 * Returns NULL if no requests are free.
1049 * The refcount is initialized to 2 - one for the async op completion,
1050 * one for the synchronous code that does this.
1052 static inline struct aio_kiocb
*aio_get_req(struct kioctx
*ctx
)
1054 struct aio_kiocb
*req
;
1056 req
= kmem_cache_alloc(kiocb_cachep
, GFP_KERNEL
);
1060 if (unlikely(!get_reqs_available(ctx
))) {
1061 kmem_cache_free(kiocb_cachep
, req
);
1065 percpu_ref_get(&ctx
->reqs
);
1067 INIT_LIST_HEAD(&req
->ki_list
);
1068 refcount_set(&req
->ki_refcnt
, 2);
1069 req
->ki_eventfd
= NULL
;
1073 static struct kioctx
*lookup_ioctx(unsigned long ctx_id
)
1075 struct aio_ring __user
*ring
= (void __user
*)ctx_id
;
1076 struct mm_struct
*mm
= current
->mm
;
1077 struct kioctx
*ctx
, *ret
= NULL
;
1078 struct kioctx_table
*table
;
1081 if (get_user(id
, &ring
->id
))
1085 table
= rcu_dereference(mm
->ioctx_table
);
1087 if (!table
|| id
>= table
->nr
)
1090 id
= array_index_nospec(id
, table
->nr
);
1091 ctx
= rcu_dereference(table
->table
[id
]);
1092 if (ctx
&& ctx
->user_id
== ctx_id
) {
1093 if (percpu_ref_tryget_live(&ctx
->users
))
1101 static inline void iocb_destroy(struct aio_kiocb
*iocb
)
1103 if (iocb
->ki_eventfd
)
1104 eventfd_ctx_put(iocb
->ki_eventfd
);
1106 fput(iocb
->ki_filp
);
1107 percpu_ref_put(&iocb
->ki_ctx
->reqs
);
1108 kmem_cache_free(kiocb_cachep
, iocb
);
1112 * Called when the io request on the given iocb is complete.
1114 static void aio_complete(struct aio_kiocb
*iocb
)
1116 struct kioctx
*ctx
= iocb
->ki_ctx
;
1117 struct aio_ring
*ring
;
1118 struct io_event
*ev_page
, *event
;
1119 unsigned tail
, pos
, head
;
1120 unsigned long flags
;
1123 * Add a completion event to the ring buffer. Must be done holding
1124 * ctx->completion_lock to prevent other code from messing with the tail
1125 * pointer since we might be called from irq context.
1127 spin_lock_irqsave(&ctx
->completion_lock
, flags
);
1130 pos
= tail
+ AIO_EVENTS_OFFSET
;
1132 if (++tail
>= ctx
->nr_events
)
1135 ev_page
= kmap_atomic(ctx
->ring_pages
[pos
/ AIO_EVENTS_PER_PAGE
]);
1136 event
= ev_page
+ pos
% AIO_EVENTS_PER_PAGE
;
1138 *event
= iocb
->ki_res
;
1140 kunmap_atomic(ev_page
);
1141 flush_dcache_page(ctx
->ring_pages
[pos
/ AIO_EVENTS_PER_PAGE
]);
1143 pr_debug("%p[%u]: %p: %p %Lx %Lx %Lx\n", ctx
, tail
, iocb
,
1144 (void __user
*)(unsigned long)iocb
->ki_res
.obj
,
1145 iocb
->ki_res
.data
, iocb
->ki_res
.res
, iocb
->ki_res
.res2
);
1147 /* after flagging the request as done, we
1148 * must never even look at it again
1150 smp_wmb(); /* make event visible before updating tail */
1154 ring
= kmap_atomic(ctx
->ring_pages
[0]);
1157 kunmap_atomic(ring
);
1158 flush_dcache_page(ctx
->ring_pages
[0]);
1160 ctx
->completed_events
++;
1161 if (ctx
->completed_events
> 1)
1162 refill_reqs_available(ctx
, head
, tail
);
1163 spin_unlock_irqrestore(&ctx
->completion_lock
, flags
);
1165 pr_debug("added to ring %p at [%u]\n", iocb
, tail
);
1168 * Check if the user asked us to deliver the result through an
1169 * eventfd. The eventfd_signal() function is safe to be called
1172 if (iocb
->ki_eventfd
)
1173 eventfd_signal(iocb
->ki_eventfd
, 1);
1176 * We have to order our ring_info tail store above and test
1177 * of the wait list below outside the wait lock. This is
1178 * like in wake_up_bit() where clearing a bit has to be
1179 * ordered with the unlocked test.
1183 if (waitqueue_active(&ctx
->wait
))
1184 wake_up(&ctx
->wait
);
1187 static inline void iocb_put(struct aio_kiocb
*iocb
)
1189 if (refcount_dec_and_test(&iocb
->ki_refcnt
)) {
1195 /* aio_read_events_ring
1196 * Pull an event off of the ioctx's event ring. Returns the number of
1199 static long aio_read_events_ring(struct kioctx
*ctx
,
1200 struct io_event __user
*event
, long nr
)
1202 struct aio_ring
*ring
;
1203 unsigned head
, tail
, pos
;
1208 * The mutex can block and wake us up and that will cause
1209 * wait_event_interruptible_hrtimeout() to schedule without sleeping
1210 * and repeat. This should be rare enough that it doesn't cause
1211 * peformance issues. See the comment in read_events() for more detail.
1213 sched_annotate_sleep();
1214 mutex_lock(&ctx
->ring_lock
);
1216 /* Access to ->ring_pages here is protected by ctx->ring_lock. */
1217 ring
= kmap_atomic(ctx
->ring_pages
[0]);
1220 kunmap_atomic(ring
);
1223 * Ensure that once we've read the current tail pointer, that
1224 * we also see the events that were stored up to the tail.
1228 pr_debug("h%u t%u m%u\n", head
, tail
, ctx
->nr_events
);
1233 head
%= ctx
->nr_events
;
1234 tail
%= ctx
->nr_events
;
1238 struct io_event
*ev
;
1241 avail
= (head
<= tail
? tail
: ctx
->nr_events
) - head
;
1245 pos
= head
+ AIO_EVENTS_OFFSET
;
1246 page
= ctx
->ring_pages
[pos
/ AIO_EVENTS_PER_PAGE
];
1247 pos
%= AIO_EVENTS_PER_PAGE
;
1249 avail
= min(avail
, nr
- ret
);
1250 avail
= min_t(long, avail
, AIO_EVENTS_PER_PAGE
- pos
);
1253 copy_ret
= copy_to_user(event
+ ret
, ev
+ pos
,
1254 sizeof(*ev
) * avail
);
1257 if (unlikely(copy_ret
)) {
1264 head
%= ctx
->nr_events
;
1267 ring
= kmap_atomic(ctx
->ring_pages
[0]);
1269 kunmap_atomic(ring
);
1270 flush_dcache_page(ctx
->ring_pages
[0]);
1272 pr_debug("%li h%u t%u\n", ret
, head
, tail
);
1274 mutex_unlock(&ctx
->ring_lock
);
1279 static bool aio_read_events(struct kioctx
*ctx
, long min_nr
, long nr
,
1280 struct io_event __user
*event
, long *i
)
1282 long ret
= aio_read_events_ring(ctx
, event
+ *i
, nr
- *i
);
1287 if (unlikely(atomic_read(&ctx
->dead
)))
1293 return ret
< 0 || *i
>= min_nr
;
1296 static long read_events(struct kioctx
*ctx
, long min_nr
, long nr
,
1297 struct io_event __user
*event
,
1303 * Note that aio_read_events() is being called as the conditional - i.e.
1304 * we're calling it after prepare_to_wait() has set task state to
1305 * TASK_INTERRUPTIBLE.
1307 * But aio_read_events() can block, and if it blocks it's going to flip
1308 * the task state back to TASK_RUNNING.
1310 * This should be ok, provided it doesn't flip the state back to
1311 * TASK_RUNNING and return 0 too much - that causes us to spin. That
1312 * will only happen if the mutex_lock() call blocks, and we then find
1313 * the ringbuffer empty. So in practice we should be ok, but it's
1314 * something to be aware of when touching this code.
1317 aio_read_events(ctx
, min_nr
, nr
, event
, &ret
);
1319 wait_event_interruptible_hrtimeout(ctx
->wait
,
1320 aio_read_events(ctx
, min_nr
, nr
, event
, &ret
),
1326 * Create an aio_context capable of receiving at least nr_events.
1327 * ctxp must not point to an aio_context that already exists, and
1328 * must be initialized to 0 prior to the call. On successful
1329 * creation of the aio_context, *ctxp is filled in with the resulting
1330 * handle. May fail with -EINVAL if *ctxp is not initialized,
1331 * if the specified nr_events exceeds internal limits. May fail
1332 * with -EAGAIN if the specified nr_events exceeds the user's limit
1333 * of available events. May fail with -ENOMEM if insufficient kernel
1334 * resources are available. May fail with -EFAULT if an invalid
1335 * pointer is passed for ctxp. Will fail with -ENOSYS if not
1338 SYSCALL_DEFINE2(io_setup
, unsigned, nr_events
, aio_context_t __user
*, ctxp
)
1340 struct kioctx
*ioctx
= NULL
;
1344 ret
= get_user(ctx
, ctxp
);
1349 if (unlikely(ctx
|| nr_events
== 0)) {
1350 pr_debug("EINVAL: ctx %lu nr_events %u\n",
1355 ioctx
= ioctx_alloc(nr_events
);
1356 ret
= PTR_ERR(ioctx
);
1357 if (!IS_ERR(ioctx
)) {
1358 ret
= put_user(ioctx
->user_id
, ctxp
);
1360 kill_ioctx(current
->mm
, ioctx
, NULL
);
1361 percpu_ref_put(&ioctx
->users
);
1368 #ifdef CONFIG_COMPAT
1369 COMPAT_SYSCALL_DEFINE2(io_setup
, unsigned, nr_events
, u32 __user
*, ctx32p
)
1371 struct kioctx
*ioctx
= NULL
;
1375 ret
= get_user(ctx
, ctx32p
);
1380 if (unlikely(ctx
|| nr_events
== 0)) {
1381 pr_debug("EINVAL: ctx %lu nr_events %u\n",
1386 ioctx
= ioctx_alloc(nr_events
);
1387 ret
= PTR_ERR(ioctx
);
1388 if (!IS_ERR(ioctx
)) {
1389 /* truncating is ok because it's a user address */
1390 ret
= put_user((u32
)ioctx
->user_id
, ctx32p
);
1392 kill_ioctx(current
->mm
, ioctx
, NULL
);
1393 percpu_ref_put(&ioctx
->users
);
1402 * Destroy the aio_context specified. May cancel any outstanding
1403 * AIOs and block on completion. Will fail with -ENOSYS if not
1404 * implemented. May fail with -EINVAL if the context pointed to
1407 SYSCALL_DEFINE1(io_destroy
, aio_context_t
, ctx
)
1409 struct kioctx
*ioctx
= lookup_ioctx(ctx
);
1410 if (likely(NULL
!= ioctx
)) {
1411 struct ctx_rq_wait wait
;
1414 init_completion(&wait
.comp
);
1415 atomic_set(&wait
.count
, 1);
1417 /* Pass requests_done to kill_ioctx() where it can be set
1418 * in a thread-safe way. If we try to set it here then we have
1419 * a race condition if two io_destroy() called simultaneously.
1421 ret
= kill_ioctx(current
->mm
, ioctx
, &wait
);
1422 percpu_ref_put(&ioctx
->users
);
1424 /* Wait until all IO for the context are done. Otherwise kernel
1425 * keep using user-space buffers even if user thinks the context
1429 wait_for_completion(&wait
.comp
);
1433 pr_debug("EINVAL: invalid context id\n");
1437 static void aio_remove_iocb(struct aio_kiocb
*iocb
)
1439 struct kioctx
*ctx
= iocb
->ki_ctx
;
1440 unsigned long flags
;
1442 spin_lock_irqsave(&ctx
->ctx_lock
, flags
);
1443 list_del(&iocb
->ki_list
);
1444 spin_unlock_irqrestore(&ctx
->ctx_lock
, flags
);
1447 static void aio_complete_rw(struct kiocb
*kiocb
, long res
)
1449 struct aio_kiocb
*iocb
= container_of(kiocb
, struct aio_kiocb
, rw
);
1451 if (!list_empty_careful(&iocb
->ki_list
))
1452 aio_remove_iocb(iocb
);
1454 if (kiocb
->ki_flags
& IOCB_WRITE
) {
1455 struct inode
*inode
= file_inode(kiocb
->ki_filp
);
1458 * Tell lockdep we inherited freeze protection from submission
1461 if (S_ISREG(inode
->i_mode
))
1462 __sb_writers_acquired(inode
->i_sb
, SB_FREEZE_WRITE
);
1463 file_end_write(kiocb
->ki_filp
);
1466 iocb
->ki_res
.res
= res
;
1467 iocb
->ki_res
.res2
= 0;
1471 static int aio_prep_rw(struct kiocb
*req
, const struct iocb
*iocb
)
1475 req
->ki_complete
= aio_complete_rw
;
1476 req
->private = NULL
;
1477 req
->ki_pos
= iocb
->aio_offset
;
1478 req
->ki_flags
= iocb_flags(req
->ki_filp
);
1479 if (iocb
->aio_flags
& IOCB_FLAG_RESFD
)
1480 req
->ki_flags
|= IOCB_EVENTFD
;
1481 if (iocb
->aio_flags
& IOCB_FLAG_IOPRIO
) {
1483 * If the IOCB_FLAG_IOPRIO flag of aio_flags is set, then
1484 * aio_reqprio is interpreted as an I/O scheduling
1485 * class and priority.
1487 ret
= ioprio_check_cap(iocb
->aio_reqprio
);
1489 pr_debug("aio ioprio check cap error: %d\n", ret
);
1493 req
->ki_ioprio
= iocb
->aio_reqprio
;
1495 req
->ki_ioprio
= get_current_ioprio();
1497 ret
= kiocb_set_rw_flags(req
, iocb
->aio_rw_flags
);
1501 req
->ki_flags
&= ~IOCB_HIPRI
; /* no one is going to poll for this I/O */
1505 static ssize_t
aio_setup_rw(int rw
, const struct iocb
*iocb
,
1506 struct iovec
**iovec
, bool vectored
, bool compat
,
1507 struct iov_iter
*iter
)
1509 void __user
*buf
= (void __user
*)(uintptr_t)iocb
->aio_buf
;
1510 size_t len
= iocb
->aio_nbytes
;
1513 ssize_t ret
= import_single_range(rw
, buf
, len
, *iovec
, iter
);
1518 return __import_iovec(rw
, buf
, len
, UIO_FASTIOV
, iovec
, iter
, compat
);
1521 static inline void aio_rw_done(struct kiocb
*req
, ssize_t ret
)
1527 case -ERESTARTNOINTR
:
1528 case -ERESTARTNOHAND
:
1529 case -ERESTART_RESTARTBLOCK
:
1531 * There's no easy way to restart the syscall since other AIO's
1532 * may be already running. Just fail this IO with EINTR.
1537 req
->ki_complete(req
, ret
);
1541 static int aio_read(struct kiocb
*req
, const struct iocb
*iocb
,
1542 bool vectored
, bool compat
)
1544 struct iovec inline_vecs
[UIO_FASTIOV
], *iovec
= inline_vecs
;
1545 struct iov_iter iter
;
1549 ret
= aio_prep_rw(req
, iocb
);
1552 file
= req
->ki_filp
;
1553 if (unlikely(!(file
->f_mode
& FMODE_READ
)))
1555 if (unlikely(!file
->f_op
->read_iter
))
1558 ret
= aio_setup_rw(READ
, iocb
, &iovec
, vectored
, compat
, &iter
);
1561 ret
= rw_verify_area(READ
, file
, &req
->ki_pos
, iov_iter_count(&iter
));
1563 aio_rw_done(req
, call_read_iter(file
, req
, &iter
));
1568 static int aio_write(struct kiocb
*req
, const struct iocb
*iocb
,
1569 bool vectored
, bool compat
)
1571 struct iovec inline_vecs
[UIO_FASTIOV
], *iovec
= inline_vecs
;
1572 struct iov_iter iter
;
1576 ret
= aio_prep_rw(req
, iocb
);
1579 file
= req
->ki_filp
;
1581 if (unlikely(!(file
->f_mode
& FMODE_WRITE
)))
1583 if (unlikely(!file
->f_op
->write_iter
))
1586 ret
= aio_setup_rw(WRITE
, iocb
, &iovec
, vectored
, compat
, &iter
);
1589 ret
= rw_verify_area(WRITE
, file
, &req
->ki_pos
, iov_iter_count(&iter
));
1592 * Open-code file_start_write here to grab freeze protection,
1593 * which will be released by another thread in
1594 * aio_complete_rw(). Fool lockdep by telling it the lock got
1595 * released so that it doesn't complain about the held lock when
1596 * we return to userspace.
1598 if (S_ISREG(file_inode(file
)->i_mode
)) {
1599 sb_start_write(file_inode(file
)->i_sb
);
1600 __sb_writers_release(file_inode(file
)->i_sb
, SB_FREEZE_WRITE
);
1602 req
->ki_flags
|= IOCB_WRITE
;
1603 aio_rw_done(req
, call_write_iter(file
, req
, &iter
));
1609 static void aio_fsync_work(struct work_struct
*work
)
1611 struct aio_kiocb
*iocb
= container_of(work
, struct aio_kiocb
, fsync
.work
);
1612 const struct cred
*old_cred
= override_creds(iocb
->fsync
.creds
);
1614 iocb
->ki_res
.res
= vfs_fsync(iocb
->fsync
.file
, iocb
->fsync
.datasync
);
1615 revert_creds(old_cred
);
1616 put_cred(iocb
->fsync
.creds
);
1620 static int aio_fsync(struct fsync_iocb
*req
, const struct iocb
*iocb
,
1623 if (unlikely(iocb
->aio_buf
|| iocb
->aio_offset
|| iocb
->aio_nbytes
||
1624 iocb
->aio_rw_flags
))
1627 if (unlikely(!req
->file
->f_op
->fsync
))
1630 req
->creds
= prepare_creds();
1634 req
->datasync
= datasync
;
1635 INIT_WORK(&req
->work
, aio_fsync_work
);
1636 schedule_work(&req
->work
);
1640 static void aio_poll_put_work(struct work_struct
*work
)
1642 struct poll_iocb
*req
= container_of(work
, struct poll_iocb
, work
);
1643 struct aio_kiocb
*iocb
= container_of(req
, struct aio_kiocb
, poll
);
1649 * Safely lock the waitqueue which the request is on, synchronizing with the
1650 * case where the ->poll() provider decides to free its waitqueue early.
1652 * Returns true on success, meaning that req->head->lock was locked, req->wait
1653 * is on req->head, and an RCU read lock was taken. Returns false if the
1654 * request was already removed from its waitqueue (which might no longer exist).
1656 static bool poll_iocb_lock_wq(struct poll_iocb
*req
)
1658 wait_queue_head_t
*head
;
1661 * While we hold the waitqueue lock and the waitqueue is nonempty,
1662 * wake_up_pollfree() will wait for us. However, taking the waitqueue
1663 * lock in the first place can race with the waitqueue being freed.
1665 * We solve this as eventpoll does: by taking advantage of the fact that
1666 * all users of wake_up_pollfree() will RCU-delay the actual free. If
1667 * we enter rcu_read_lock() and see that the pointer to the queue is
1668 * non-NULL, we can then lock it without the memory being freed out from
1669 * under us, then check whether the request is still on the queue.
1671 * Keep holding rcu_read_lock() as long as we hold the queue lock, in
1672 * case the caller deletes the entry from the queue, leaving it empty.
1673 * In that case, only RCU prevents the queue memory from being freed.
1676 head
= smp_load_acquire(&req
->head
);
1678 spin_lock(&head
->lock
);
1679 if (!list_empty(&req
->wait
.entry
))
1681 spin_unlock(&head
->lock
);
1687 static void poll_iocb_unlock_wq(struct poll_iocb
*req
)
1689 spin_unlock(&req
->head
->lock
);
1693 static void aio_poll_complete_work(struct work_struct
*work
)
1695 struct poll_iocb
*req
= container_of(work
, struct poll_iocb
, work
);
1696 struct aio_kiocb
*iocb
= container_of(req
, struct aio_kiocb
, poll
);
1697 struct poll_table_struct pt
= { ._key
= req
->events
};
1698 struct kioctx
*ctx
= iocb
->ki_ctx
;
1701 if (!READ_ONCE(req
->cancelled
))
1702 mask
= vfs_poll(req
->file
, &pt
) & req
->events
;
1705 * Note that ->ki_cancel callers also delete iocb from active_reqs after
1706 * calling ->ki_cancel. We need the ctx_lock roundtrip here to
1707 * synchronize with them. In the cancellation case the list_del_init
1708 * itself is not actually needed, but harmless so we keep it in to
1709 * avoid further branches in the fast path.
1711 spin_lock_irq(&ctx
->ctx_lock
);
1712 if (poll_iocb_lock_wq(req
)) {
1713 if (!mask
&& !READ_ONCE(req
->cancelled
)) {
1715 * The request isn't actually ready to be completed yet.
1716 * Reschedule completion if another wakeup came in.
1718 if (req
->work_need_resched
) {
1719 schedule_work(&req
->work
);
1720 req
->work_need_resched
= false;
1722 req
->work_scheduled
= false;
1724 poll_iocb_unlock_wq(req
);
1725 spin_unlock_irq(&ctx
->ctx_lock
);
1728 list_del_init(&req
->wait
.entry
);
1729 poll_iocb_unlock_wq(req
);
1730 } /* else, POLLFREE has freed the waitqueue, so we must complete */
1731 list_del_init(&iocb
->ki_list
);
1732 iocb
->ki_res
.res
= mangle_poll(mask
);
1733 spin_unlock_irq(&ctx
->ctx_lock
);
1738 /* assumes we are called with irqs disabled */
1739 static int aio_poll_cancel(struct kiocb
*iocb
)
1741 struct aio_kiocb
*aiocb
= container_of(iocb
, struct aio_kiocb
, rw
);
1742 struct poll_iocb
*req
= &aiocb
->poll
;
1744 if (poll_iocb_lock_wq(req
)) {
1745 WRITE_ONCE(req
->cancelled
, true);
1746 if (!req
->work_scheduled
) {
1747 schedule_work(&aiocb
->poll
.work
);
1748 req
->work_scheduled
= true;
1750 poll_iocb_unlock_wq(req
);
1751 } /* else, the request was force-cancelled by POLLFREE already */
1756 static int aio_poll_wake(struct wait_queue_entry
*wait
, unsigned mode
, int sync
,
1759 struct poll_iocb
*req
= container_of(wait
, struct poll_iocb
, wait
);
1760 struct aio_kiocb
*iocb
= container_of(req
, struct aio_kiocb
, poll
);
1761 __poll_t mask
= key_to_poll(key
);
1762 unsigned long flags
;
1764 /* for instances that support it check for an event match first: */
1765 if (mask
&& !(mask
& req
->events
))
1769 * Complete the request inline if possible. This requires that three
1770 * conditions be met:
1771 * 1. An event mask must have been passed. If a plain wakeup was done
1772 * instead, then mask == 0 and we have to call vfs_poll() to get
1773 * the events, so inline completion isn't possible.
1774 * 2. The completion work must not have already been scheduled.
1775 * 3. ctx_lock must not be busy. We have to use trylock because we
1776 * already hold the waitqueue lock, so this inverts the normal
1777 * locking order. Use irqsave/irqrestore because not all
1778 * filesystems (e.g. fuse) call this function with IRQs disabled,
1779 * yet IRQs have to be disabled before ctx_lock is obtained.
1781 if (mask
&& !req
->work_scheduled
&&
1782 spin_trylock_irqsave(&iocb
->ki_ctx
->ctx_lock
, flags
)) {
1783 struct kioctx
*ctx
= iocb
->ki_ctx
;
1785 list_del_init(&req
->wait
.entry
);
1786 list_del(&iocb
->ki_list
);
1787 iocb
->ki_res
.res
= mangle_poll(mask
);
1788 if (iocb
->ki_eventfd
&& !eventfd_signal_allowed()) {
1790 INIT_WORK(&req
->work
, aio_poll_put_work
);
1791 schedule_work(&req
->work
);
1793 spin_unlock_irqrestore(&ctx
->ctx_lock
, flags
);
1798 * Schedule the completion work if needed. If it was already
1799 * scheduled, record that another wakeup came in.
1801 * Don't remove the request from the waitqueue here, as it might
1802 * not actually be complete yet (we won't know until vfs_poll()
1803 * is called), and we must not miss any wakeups. POLLFREE is an
1804 * exception to this; see below.
1806 if (req
->work_scheduled
) {
1807 req
->work_need_resched
= true;
1809 schedule_work(&req
->work
);
1810 req
->work_scheduled
= true;
1814 * If the waitqueue is being freed early but we can't complete
1815 * the request inline, we have to tear down the request as best
1816 * we can. That means immediately removing the request from its
1817 * waitqueue and preventing all further accesses to the
1818 * waitqueue via the request. We also need to schedule the
1819 * completion work (done above). Also mark the request as
1820 * cancelled, to potentially skip an unneeded call to ->poll().
1822 if (mask
& POLLFREE
) {
1823 WRITE_ONCE(req
->cancelled
, true);
1824 list_del_init(&req
->wait
.entry
);
1827 * Careful: this *must* be the last step, since as soon
1828 * as req->head is NULL'ed out, the request can be
1829 * completed and freed, since aio_poll_complete_work()
1830 * will no longer need to take the waitqueue lock.
1832 smp_store_release(&req
->head
, NULL
);
1838 struct aio_poll_table
{
1839 struct poll_table_struct pt
;
1840 struct aio_kiocb
*iocb
;
1846 aio_poll_queue_proc(struct file
*file
, struct wait_queue_head
*head
,
1847 struct poll_table_struct
*p
)
1849 struct aio_poll_table
*pt
= container_of(p
, struct aio_poll_table
, pt
);
1851 /* multiple wait queues per file are not supported */
1852 if (unlikely(pt
->queued
)) {
1853 pt
->error
= -EINVAL
;
1859 pt
->iocb
->poll
.head
= head
;
1860 add_wait_queue(head
, &pt
->iocb
->poll
.wait
);
1863 static int aio_poll(struct aio_kiocb
*aiocb
, const struct iocb
*iocb
)
1865 struct kioctx
*ctx
= aiocb
->ki_ctx
;
1866 struct poll_iocb
*req
= &aiocb
->poll
;
1867 struct aio_poll_table apt
;
1868 bool cancel
= false;
1871 /* reject any unknown events outside the normal event mask. */
1872 if ((u16
)iocb
->aio_buf
!= iocb
->aio_buf
)
1874 /* reject fields that are not defined for poll */
1875 if (iocb
->aio_offset
|| iocb
->aio_nbytes
|| iocb
->aio_rw_flags
)
1878 INIT_WORK(&req
->work
, aio_poll_complete_work
);
1879 req
->events
= demangle_poll(iocb
->aio_buf
) | EPOLLERR
| EPOLLHUP
;
1882 req
->cancelled
= false;
1883 req
->work_scheduled
= false;
1884 req
->work_need_resched
= false;
1886 apt
.pt
._qproc
= aio_poll_queue_proc
;
1887 apt
.pt
._key
= req
->events
;
1890 apt
.error
= -EINVAL
; /* same as no support for IOCB_CMD_POLL */
1892 /* initialized the list so that we can do list_empty checks */
1893 INIT_LIST_HEAD(&req
->wait
.entry
);
1894 init_waitqueue_func_entry(&req
->wait
, aio_poll_wake
);
1896 mask
= vfs_poll(req
->file
, &apt
.pt
) & req
->events
;
1897 spin_lock_irq(&ctx
->ctx_lock
);
1898 if (likely(apt
.queued
)) {
1899 bool on_queue
= poll_iocb_lock_wq(req
);
1901 if (!on_queue
|| req
->work_scheduled
) {
1903 * aio_poll_wake() already either scheduled the async
1904 * completion work, or completed the request inline.
1906 if (apt
.error
) /* unsupported case: multiple queues */
1911 if (mask
|| apt
.error
) {
1912 /* Steal to complete synchronously. */
1913 list_del_init(&req
->wait
.entry
);
1914 } else if (cancel
) {
1915 /* Cancel if possible (may be too late though). */
1916 WRITE_ONCE(req
->cancelled
, true);
1917 } else if (on_queue
) {
1919 * Actually waiting for an event, so add the request to
1920 * active_reqs so that it can be cancelled if needed.
1922 list_add_tail(&aiocb
->ki_list
, &ctx
->active_reqs
);
1923 aiocb
->ki_cancel
= aio_poll_cancel
;
1926 poll_iocb_unlock_wq(req
);
1928 if (mask
) { /* no async, we'd stolen it */
1929 aiocb
->ki_res
.res
= mangle_poll(mask
);
1932 spin_unlock_irq(&ctx
->ctx_lock
);
1938 static int __io_submit_one(struct kioctx
*ctx
, const struct iocb
*iocb
,
1939 struct iocb __user
*user_iocb
, struct aio_kiocb
*req
,
1942 req
->ki_filp
= fget(iocb
->aio_fildes
);
1943 if (unlikely(!req
->ki_filp
))
1946 if (iocb
->aio_flags
& IOCB_FLAG_RESFD
) {
1947 struct eventfd_ctx
*eventfd
;
1949 * If the IOCB_FLAG_RESFD flag of aio_flags is set, get an
1950 * instance of the file* now. The file descriptor must be
1951 * an eventfd() fd, and will be signaled for each completed
1952 * event using the eventfd_signal() function.
1954 eventfd
= eventfd_ctx_fdget(iocb
->aio_resfd
);
1955 if (IS_ERR(eventfd
))
1956 return PTR_ERR(eventfd
);
1958 req
->ki_eventfd
= eventfd
;
1961 if (unlikely(put_user(KIOCB_KEY
, &user_iocb
->aio_key
))) {
1962 pr_debug("EFAULT: aio_key\n");
1966 req
->ki_res
.obj
= (u64
)(unsigned long)user_iocb
;
1967 req
->ki_res
.data
= iocb
->aio_data
;
1968 req
->ki_res
.res
= 0;
1969 req
->ki_res
.res2
= 0;
1971 switch (iocb
->aio_lio_opcode
) {
1972 case IOCB_CMD_PREAD
:
1973 return aio_read(&req
->rw
, iocb
, false, compat
);
1974 case IOCB_CMD_PWRITE
:
1975 return aio_write(&req
->rw
, iocb
, false, compat
);
1976 case IOCB_CMD_PREADV
:
1977 return aio_read(&req
->rw
, iocb
, true, compat
);
1978 case IOCB_CMD_PWRITEV
:
1979 return aio_write(&req
->rw
, iocb
, true, compat
);
1980 case IOCB_CMD_FSYNC
:
1981 return aio_fsync(&req
->fsync
, iocb
, false);
1982 case IOCB_CMD_FDSYNC
:
1983 return aio_fsync(&req
->fsync
, iocb
, true);
1985 return aio_poll(req
, iocb
);
1987 pr_debug("invalid aio operation %d\n", iocb
->aio_lio_opcode
);
1992 static int io_submit_one(struct kioctx
*ctx
, struct iocb __user
*user_iocb
,
1995 struct aio_kiocb
*req
;
1999 if (unlikely(copy_from_user(&iocb
, user_iocb
, sizeof(iocb
))))
2002 /* enforce forwards compatibility on users */
2003 if (unlikely(iocb
.aio_reserved2
)) {
2004 pr_debug("EINVAL: reserve field set\n");
2008 /* prevent overflows */
2010 (iocb
.aio_buf
!= (unsigned long)iocb
.aio_buf
) ||
2011 (iocb
.aio_nbytes
!= (size_t)iocb
.aio_nbytes
) ||
2012 ((ssize_t
)iocb
.aio_nbytes
< 0)
2014 pr_debug("EINVAL: overflow check\n");
2018 req
= aio_get_req(ctx
);
2022 err
= __io_submit_one(ctx
, &iocb
, user_iocb
, req
, compat
);
2024 /* Done with the synchronous reference */
2028 * If err is 0, we'd either done aio_complete() ourselves or have
2029 * arranged for that to be done asynchronously. Anything non-zero
2030 * means that we need to destroy req ourselves.
2032 if (unlikely(err
)) {
2034 put_reqs_available(ctx
, 1);
2040 * Queue the nr iocbs pointed to by iocbpp for processing. Returns
2041 * the number of iocbs queued. May return -EINVAL if the aio_context
2042 * specified by ctx_id is invalid, if nr is < 0, if the iocb at
2043 * *iocbpp[0] is not properly initialized, if the operation specified
2044 * is invalid for the file descriptor in the iocb. May fail with
2045 * -EFAULT if any of the data structures point to invalid data. May
2046 * fail with -EBADF if the file descriptor specified in the first
2047 * iocb is invalid. May fail with -EAGAIN if insufficient resources
2048 * are available to queue any iocbs. Will return 0 if nr is 0. Will
2049 * fail with -ENOSYS if not implemented.
2051 SYSCALL_DEFINE3(io_submit
, aio_context_t
, ctx_id
, long, nr
,
2052 struct iocb __user
* __user
*, iocbpp
)
2057 struct blk_plug plug
;
2059 if (unlikely(nr
< 0))
2062 ctx
= lookup_ioctx(ctx_id
);
2063 if (unlikely(!ctx
)) {
2064 pr_debug("EINVAL: invalid context id\n");
2068 if (nr
> ctx
->nr_events
)
2069 nr
= ctx
->nr_events
;
2071 if (nr
> AIO_PLUG_THRESHOLD
)
2072 blk_start_plug(&plug
);
2073 for (i
= 0; i
< nr
; i
++) {
2074 struct iocb __user
*user_iocb
;
2076 if (unlikely(get_user(user_iocb
, iocbpp
+ i
))) {
2081 ret
= io_submit_one(ctx
, user_iocb
, false);
2085 if (nr
> AIO_PLUG_THRESHOLD
)
2086 blk_finish_plug(&plug
);
2088 percpu_ref_put(&ctx
->users
);
2092 #ifdef CONFIG_COMPAT
2093 COMPAT_SYSCALL_DEFINE3(io_submit
, compat_aio_context_t
, ctx_id
,
2094 int, nr
, compat_uptr_t __user
*, iocbpp
)
2099 struct blk_plug plug
;
2101 if (unlikely(nr
< 0))
2104 ctx
= lookup_ioctx(ctx_id
);
2105 if (unlikely(!ctx
)) {
2106 pr_debug("EINVAL: invalid context id\n");
2110 if (nr
> ctx
->nr_events
)
2111 nr
= ctx
->nr_events
;
2113 if (nr
> AIO_PLUG_THRESHOLD
)
2114 blk_start_plug(&plug
);
2115 for (i
= 0; i
< nr
; i
++) {
2116 compat_uptr_t user_iocb
;
2118 if (unlikely(get_user(user_iocb
, iocbpp
+ i
))) {
2123 ret
= io_submit_one(ctx
, compat_ptr(user_iocb
), true);
2127 if (nr
> AIO_PLUG_THRESHOLD
)
2128 blk_finish_plug(&plug
);
2130 percpu_ref_put(&ctx
->users
);
2136 * Attempts to cancel an iocb previously passed to io_submit. If
2137 * the operation is successfully cancelled, the resulting event is
2138 * copied into the memory pointed to by result without being placed
2139 * into the completion queue and 0 is returned. May fail with
2140 * -EFAULT if any of the data structures pointed to are invalid.
2141 * May fail with -EINVAL if aio_context specified by ctx_id is
2142 * invalid. May fail with -EAGAIN if the iocb specified was not
2143 * cancelled. Will fail with -ENOSYS if not implemented.
2145 SYSCALL_DEFINE3(io_cancel
, aio_context_t
, ctx_id
, struct iocb __user
*, iocb
,
2146 struct io_event __user
*, result
)
2149 struct aio_kiocb
*kiocb
;
2152 u64 obj
= (u64
)(unsigned long)iocb
;
2154 if (unlikely(get_user(key
, &iocb
->aio_key
)))
2156 if (unlikely(key
!= KIOCB_KEY
))
2159 ctx
= lookup_ioctx(ctx_id
);
2163 spin_lock_irq(&ctx
->ctx_lock
);
2164 /* TODO: use a hash or array, this sucks. */
2165 list_for_each_entry(kiocb
, &ctx
->active_reqs
, ki_list
) {
2166 if (kiocb
->ki_res
.obj
== obj
) {
2167 ret
= kiocb
->ki_cancel(&kiocb
->rw
);
2168 list_del_init(&kiocb
->ki_list
);
2172 spin_unlock_irq(&ctx
->ctx_lock
);
2176 * The result argument is no longer used - the io_event is
2177 * always delivered via the ring buffer. -EINPROGRESS indicates
2178 * cancellation is progress:
2183 percpu_ref_put(&ctx
->users
);
2188 static long do_io_getevents(aio_context_t ctx_id
,
2191 struct io_event __user
*events
,
2192 struct timespec64
*ts
)
2194 ktime_t until
= ts
? timespec64_to_ktime(*ts
) : KTIME_MAX
;
2195 struct kioctx
*ioctx
= lookup_ioctx(ctx_id
);
2198 if (likely(ioctx
)) {
2199 if (likely(min_nr
<= nr
&& min_nr
>= 0))
2200 ret
= read_events(ioctx
, min_nr
, nr
, events
, until
);
2201 percpu_ref_put(&ioctx
->users
);
2208 * Attempts to read at least min_nr events and up to nr events from
2209 * the completion queue for the aio_context specified by ctx_id. If
2210 * it succeeds, the number of read events is returned. May fail with
2211 * -EINVAL if ctx_id is invalid, if min_nr is out of range, if nr is
2212 * out of range, if timeout is out of range. May fail with -EFAULT
2213 * if any of the memory specified is invalid. May return 0 or
2214 * < min_nr if the timeout specified by timeout has elapsed
2215 * before sufficient events are available, where timeout == NULL
2216 * specifies an infinite timeout. Note that the timeout pointed to by
2217 * timeout is relative. Will fail with -ENOSYS if not implemented.
2221 SYSCALL_DEFINE5(io_getevents
, aio_context_t
, ctx_id
,
2224 struct io_event __user
*, events
,
2225 struct __kernel_timespec __user
*, timeout
)
2227 struct timespec64 ts
;
2230 if (timeout
&& unlikely(get_timespec64(&ts
, timeout
)))
2233 ret
= do_io_getevents(ctx_id
, min_nr
, nr
, events
, timeout
? &ts
: NULL
);
2234 if (!ret
&& signal_pending(current
))
2241 struct __aio_sigset
{
2242 const sigset_t __user
*sigmask
;
2246 SYSCALL_DEFINE6(io_pgetevents
,
2247 aio_context_t
, ctx_id
,
2250 struct io_event __user
*, events
,
2251 struct __kernel_timespec __user
*, timeout
,
2252 const struct __aio_sigset __user
*, usig
)
2254 struct __aio_sigset ksig
= { NULL
, };
2255 struct timespec64 ts
;
2259 if (timeout
&& unlikely(get_timespec64(&ts
, timeout
)))
2262 if (usig
&& copy_from_user(&ksig
, usig
, sizeof(ksig
)))
2265 ret
= set_user_sigmask(ksig
.sigmask
, ksig
.sigsetsize
);
2269 ret
= do_io_getevents(ctx_id
, min_nr
, nr
, events
, timeout
? &ts
: NULL
);
2271 interrupted
= signal_pending(current
);
2272 restore_saved_sigmask_unless(interrupted
);
2273 if (interrupted
&& !ret
)
2274 ret
= -ERESTARTNOHAND
;
2279 #if defined(CONFIG_COMPAT_32BIT_TIME) && !defined(CONFIG_64BIT)
2281 SYSCALL_DEFINE6(io_pgetevents_time32
,
2282 aio_context_t
, ctx_id
,
2285 struct io_event __user
*, events
,
2286 struct old_timespec32 __user
*, timeout
,
2287 const struct __aio_sigset __user
*, usig
)
2289 struct __aio_sigset ksig
= { NULL
, };
2290 struct timespec64 ts
;
2294 if (timeout
&& unlikely(get_old_timespec32(&ts
, timeout
)))
2297 if (usig
&& copy_from_user(&ksig
, usig
, sizeof(ksig
)))
2301 ret
= set_user_sigmask(ksig
.sigmask
, ksig
.sigsetsize
);
2305 ret
= do_io_getevents(ctx_id
, min_nr
, nr
, events
, timeout
? &ts
: NULL
);
2307 interrupted
= signal_pending(current
);
2308 restore_saved_sigmask_unless(interrupted
);
2309 if (interrupted
&& !ret
)
2310 ret
= -ERESTARTNOHAND
;
2317 #if defined(CONFIG_COMPAT_32BIT_TIME)
2319 SYSCALL_DEFINE5(io_getevents_time32
, __u32
, ctx_id
,
2322 struct io_event __user
*, events
,
2323 struct old_timespec32 __user
*, timeout
)
2325 struct timespec64 t
;
2328 if (timeout
&& get_old_timespec32(&t
, timeout
))
2331 ret
= do_io_getevents(ctx_id
, min_nr
, nr
, events
, timeout
? &t
: NULL
);
2332 if (!ret
&& signal_pending(current
))
2339 #ifdef CONFIG_COMPAT
2341 struct __compat_aio_sigset
{
2342 compat_uptr_t sigmask
;
2343 compat_size_t sigsetsize
;
2346 #if defined(CONFIG_COMPAT_32BIT_TIME)
2348 COMPAT_SYSCALL_DEFINE6(io_pgetevents
,
2349 compat_aio_context_t
, ctx_id
,
2350 compat_long_t
, min_nr
,
2352 struct io_event __user
*, events
,
2353 struct old_timespec32 __user
*, timeout
,
2354 const struct __compat_aio_sigset __user
*, usig
)
2356 struct __compat_aio_sigset ksig
= { 0, };
2357 struct timespec64 t
;
2361 if (timeout
&& get_old_timespec32(&t
, timeout
))
2364 if (usig
&& copy_from_user(&ksig
, usig
, sizeof(ksig
)))
2367 ret
= set_compat_user_sigmask(compat_ptr(ksig
.sigmask
), ksig
.sigsetsize
);
2371 ret
= do_io_getevents(ctx_id
, min_nr
, nr
, events
, timeout
? &t
: NULL
);
2373 interrupted
= signal_pending(current
);
2374 restore_saved_sigmask_unless(interrupted
);
2375 if (interrupted
&& !ret
)
2376 ret
= -ERESTARTNOHAND
;
2383 COMPAT_SYSCALL_DEFINE6(io_pgetevents_time64
,
2384 compat_aio_context_t
, ctx_id
,
2385 compat_long_t
, min_nr
,
2387 struct io_event __user
*, events
,
2388 struct __kernel_timespec __user
*, timeout
,
2389 const struct __compat_aio_sigset __user
*, usig
)
2391 struct __compat_aio_sigset ksig
= { 0, };
2392 struct timespec64 t
;
2396 if (timeout
&& get_timespec64(&t
, timeout
))
2399 if (usig
&& copy_from_user(&ksig
, usig
, sizeof(ksig
)))
2402 ret
= set_compat_user_sigmask(compat_ptr(ksig
.sigmask
), ksig
.sigsetsize
);
2406 ret
= do_io_getevents(ctx_id
, min_nr
, nr
, events
, timeout
? &t
: NULL
);
2408 interrupted
= signal_pending(current
);
2409 restore_saved_sigmask_unless(interrupted
);
2410 if (interrupted
&& !ret
)
2411 ret
= -ERESTARTNOHAND
;