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.
9 * See ../COPYING for licensing terms.
11 #define pr_fmt(fmt) "%s: " fmt, __func__
13 #include <linux/kernel.h>
14 #include <linux/init.h>
15 #include <linux/errno.h>
16 #include <linux/time.h>
17 #include <linux/aio_abi.h>
18 #include <linux/export.h>
19 #include <linux/syscalls.h>
20 #include <linux/backing-dev.h>
21 #include <linux/uio.h>
23 #include <linux/sched.h>
25 #include <linux/file.h>
27 #include <linux/mman.h>
28 #include <linux/mmu_context.h>
29 #include <linux/percpu.h>
30 #include <linux/slab.h>
31 #include <linux/timer.h>
32 #include <linux/aio.h>
33 #include <linux/highmem.h>
34 #include <linux/workqueue.h>
35 #include <linux/security.h>
36 #include <linux/eventfd.h>
37 #include <linux/blkdev.h>
38 #include <linux/compat.h>
39 #include <linux/anon_inodes.h>
40 #include <linux/migrate.h>
41 #include <linux/ramfs.h>
42 #include <linux/percpu-refcount.h>
44 #include <asm/kmap_types.h>
45 #include <asm/uaccess.h>
49 #define AIO_RING_MAGIC 0xa10a10a1
50 #define AIO_RING_COMPAT_FEATURES 1
51 #define AIO_RING_INCOMPAT_FEATURES 0
53 unsigned id; /* kernel internal index number */
54 unsigned nr; /* number of io_events */
59 unsigned compat_features;
60 unsigned incompat_features;
61 unsigned header_length; /* size of aio_ring */
64 struct io_event io_events[0];
65 }; /* 128 bytes + ring size */
67 #define AIO_RING_PAGES 8
72 struct kioctx *table[];
76 unsigned reqs_available;
80 struct percpu_ref users;
83 struct percpu_ref reqs;
85 unsigned long user_id;
87 struct __percpu kioctx_cpu *cpu;
90 * For percpu reqs_available, number of slots we move to/from global
95 * This is what userspace passed to io_setup(), it's not used for
96 * anything but counting against the global max_reqs quota.
98 * The real limit is nr_events - 1, which will be larger (see
103 /* Size of ringbuffer, in units of struct io_event */
106 unsigned long mmap_base;
107 unsigned long mmap_size;
109 struct page **ring_pages;
112 struct work_struct free_work;
116 * This counts the number of available slots in the ringbuffer,
117 * so we avoid overflowing it: it's decremented (if positive)
118 * when allocating a kiocb and incremented when the resulting
119 * io_event is pulled off the ringbuffer.
121 * We batch accesses to it with a percpu version.
123 atomic_t reqs_available;
124 } ____cacheline_aligned_in_smp;
128 struct list_head active_reqs; /* used for cancellation */
129 } ____cacheline_aligned_in_smp;
132 struct mutex ring_lock;
133 wait_queue_head_t wait;
134 } ____cacheline_aligned_in_smp;
138 spinlock_t completion_lock;
139 } ____cacheline_aligned_in_smp;
141 struct page *internal_pages[AIO_RING_PAGES];
142 struct file *aio_ring_file;
147 /*------ sysctl variables----*/
148 static DEFINE_SPINLOCK(aio_nr_lock);
149 unsigned long aio_nr; /* current system wide number of aio requests */
150 unsigned long aio_max_nr = 0x10000; /* system wide maximum number of aio requests */
151 /*----end sysctl variables---*/
153 static struct kmem_cache *kiocb_cachep;
154 static struct kmem_cache *kioctx_cachep;
157 * Creates the slab caches used by the aio routines, panic on
158 * failure as this is done early during the boot sequence.
160 static int __init aio_setup(void)
162 kiocb_cachep = KMEM_CACHE(kiocb, SLAB_HWCACHE_ALIGN|SLAB_PANIC);
163 kioctx_cachep = KMEM_CACHE(kioctx,SLAB_HWCACHE_ALIGN|SLAB_PANIC);
165 pr_debug("sizeof(struct page) = %zu\n", sizeof(struct page));
169 __initcall(aio_setup);
171 static void put_aio_ring_file(struct kioctx *ctx)
173 struct file *aio_ring_file = ctx->aio_ring_file;
175 truncate_setsize(aio_ring_file->f_inode, 0);
177 /* Prevent further access to the kioctx from migratepages */
178 spin_lock(&aio_ring_file->f_inode->i_mapping->private_lock);
179 aio_ring_file->f_inode->i_mapping->private_data = NULL;
180 ctx->aio_ring_file = NULL;
181 spin_unlock(&aio_ring_file->f_inode->i_mapping->private_lock);
187 static void aio_free_ring(struct kioctx *ctx)
191 for (i = 0; i < ctx->nr_pages; i++) {
192 pr_debug("pid(%d) [%d] page->count=%d\n", current->pid, i,
193 page_count(ctx->ring_pages[i]));
194 put_page(ctx->ring_pages[i]);
197 put_aio_ring_file(ctx);
199 if (ctx->ring_pages && ctx->ring_pages != ctx->internal_pages) {
200 kfree(ctx->ring_pages);
201 ctx->ring_pages = NULL;
205 static int aio_ring_mmap(struct file *file, struct vm_area_struct *vma)
207 vma->vm_ops = &generic_file_vm_ops;
211 static const struct file_operations aio_ring_fops = {
212 .mmap = aio_ring_mmap,
215 static int aio_set_page_dirty(struct page *page)
220 #if IS_ENABLED(CONFIG_MIGRATION)
221 static int aio_migratepage(struct address_space *mapping, struct page *new,
222 struct page *old, enum migrate_mode mode)
228 /* Writeback must be complete */
229 BUG_ON(PageWriteback(old));
232 rc = migrate_page_move_mapping(mapping, new, old, NULL, mode);
233 if (rc != MIGRATEPAGE_SUCCESS) {
240 /* We can potentially race against kioctx teardown here. Use the
241 * address_space's private data lock to protect the mapping's
244 spin_lock(&mapping->private_lock);
245 ctx = mapping->private_data;
248 spin_lock_irqsave(&ctx->completion_lock, flags);
249 migrate_page_copy(new, old);
251 if (idx < (pgoff_t)ctx->nr_pages)
252 ctx->ring_pages[idx] = new;
253 spin_unlock_irqrestore(&ctx->completion_lock, flags);
256 spin_unlock(&mapping->private_lock);
262 static const struct address_space_operations aio_ctx_aops = {
263 .set_page_dirty = aio_set_page_dirty,
264 #if IS_ENABLED(CONFIG_MIGRATION)
265 .migratepage = aio_migratepage,
269 static int aio_setup_ring(struct kioctx *ctx)
271 struct aio_ring *ring;
272 unsigned nr_events = ctx->max_reqs;
273 struct mm_struct *mm = current->mm;
274 unsigned long size, populate;
279 /* Compensate for the ring buffer's head/tail overlap entry */
280 nr_events += 2; /* 1 is required, 2 for good luck */
282 size = sizeof(struct aio_ring);
283 size += sizeof(struct io_event) * nr_events;
285 nr_pages = PFN_UP(size);
289 file = anon_inode_getfile_private("[aio]", &aio_ring_fops, ctx, O_RDWR);
291 ctx->aio_ring_file = NULL;
295 file->f_inode->i_mapping->a_ops = &aio_ctx_aops;
296 file->f_inode->i_mapping->private_data = ctx;
297 file->f_inode->i_size = PAGE_SIZE * (loff_t)nr_pages;
299 for (i = 0; i < nr_pages; i++) {
301 page = find_or_create_page(file->f_inode->i_mapping,
302 i, GFP_HIGHUSER | __GFP_ZERO);
305 pr_debug("pid(%d) page[%d]->count=%d\n",
306 current->pid, i, page_count(page));
307 SetPageUptodate(page);
311 ctx->aio_ring_file = file;
312 nr_events = (PAGE_SIZE * nr_pages - sizeof(struct aio_ring))
313 / sizeof(struct io_event);
315 ctx->ring_pages = ctx->internal_pages;
316 if (nr_pages > AIO_RING_PAGES) {
317 ctx->ring_pages = kcalloc(nr_pages, sizeof(struct page *),
319 if (!ctx->ring_pages) {
320 put_aio_ring_file(ctx);
325 ctx->mmap_size = nr_pages * PAGE_SIZE;
326 pr_debug("attempting mmap of %lu bytes\n", ctx->mmap_size);
328 down_write(&mm->mmap_sem);
329 ctx->mmap_base = do_mmap_pgoff(ctx->aio_ring_file, 0, ctx->mmap_size,
330 PROT_READ | PROT_WRITE,
331 MAP_SHARED | MAP_POPULATE, 0, &populate);
332 if (IS_ERR((void *)ctx->mmap_base)) {
333 up_write(&mm->mmap_sem);
339 pr_debug("mmap address: 0x%08lx\n", ctx->mmap_base);
341 /* We must do this while still holding mmap_sem for write, as we
342 * need to be protected against userspace attempting to mremap()
343 * or munmap() the ring buffer.
345 ctx->nr_pages = get_user_pages(current, mm, ctx->mmap_base, nr_pages,
346 1, 0, ctx->ring_pages, NULL);
348 /* Dropping the reference here is safe as the page cache will hold
349 * onto the pages for us. It is also required so that page migration
350 * can unmap the pages and get the right reference count.
352 for (i = 0; i < ctx->nr_pages; i++)
353 put_page(ctx->ring_pages[i]);
355 up_write(&mm->mmap_sem);
357 if (unlikely(ctx->nr_pages != nr_pages)) {
362 ctx->user_id = ctx->mmap_base;
363 ctx->nr_events = nr_events; /* trusted copy */
365 ring = kmap_atomic(ctx->ring_pages[0]);
366 ring->nr = nr_events; /* user copy */
368 ring->head = ring->tail = 0;
369 ring->magic = AIO_RING_MAGIC;
370 ring->compat_features = AIO_RING_COMPAT_FEATURES;
371 ring->incompat_features = AIO_RING_INCOMPAT_FEATURES;
372 ring->header_length = sizeof(struct aio_ring);
374 flush_dcache_page(ctx->ring_pages[0]);
379 #define AIO_EVENTS_PER_PAGE (PAGE_SIZE / sizeof(struct io_event))
380 #define AIO_EVENTS_FIRST_PAGE ((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event))
381 #define AIO_EVENTS_OFFSET (AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE)
383 void kiocb_set_cancel_fn(struct kiocb *req, kiocb_cancel_fn *cancel)
385 struct kioctx *ctx = req->ki_ctx;
388 spin_lock_irqsave(&ctx->ctx_lock, flags);
390 if (!req->ki_list.next)
391 list_add(&req->ki_list, &ctx->active_reqs);
393 req->ki_cancel = cancel;
395 spin_unlock_irqrestore(&ctx->ctx_lock, flags);
397 EXPORT_SYMBOL(kiocb_set_cancel_fn);
399 static int kiocb_cancel(struct kioctx *ctx, struct kiocb *kiocb)
401 kiocb_cancel_fn *old, *cancel;
404 * Don't want to set kiocb->ki_cancel = KIOCB_CANCELLED unless it
405 * actually has a cancel function, hence the cmpxchg()
408 cancel = ACCESS_ONCE(kiocb->ki_cancel);
410 if (!cancel || cancel == KIOCB_CANCELLED)
414 cancel = cmpxchg(&kiocb->ki_cancel, old, KIOCB_CANCELLED);
415 } while (cancel != old);
417 return cancel(kiocb);
420 static void free_ioctx(struct work_struct *work)
422 struct kioctx *ctx = container_of(work, struct kioctx, free_work);
424 pr_debug("freeing %p\n", ctx);
427 free_percpu(ctx->cpu);
428 kmem_cache_free(kioctx_cachep, ctx);
431 static void free_ioctx_reqs(struct percpu_ref *ref)
433 struct kioctx *ctx = container_of(ref, struct kioctx, reqs);
435 INIT_WORK(&ctx->free_work, free_ioctx);
436 schedule_work(&ctx->free_work);
440 * When this function runs, the kioctx has been removed from the "hash table"
441 * and ctx->users has dropped to 0, so we know no more kiocbs can be submitted -
442 * now it's safe to cancel any that need to be.
444 static void free_ioctx_users(struct percpu_ref *ref)
446 struct kioctx *ctx = container_of(ref, struct kioctx, users);
449 spin_lock_irq(&ctx->ctx_lock);
451 while (!list_empty(&ctx->active_reqs)) {
452 req = list_first_entry(&ctx->active_reqs,
453 struct kiocb, ki_list);
455 list_del_init(&req->ki_list);
456 kiocb_cancel(ctx, req);
459 spin_unlock_irq(&ctx->ctx_lock);
461 percpu_ref_kill(&ctx->reqs);
462 percpu_ref_put(&ctx->reqs);
465 static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
468 struct kioctx_table *table, *old;
469 struct aio_ring *ring;
471 spin_lock(&mm->ioctx_lock);
473 table = rcu_dereference(mm->ioctx_table);
477 for (i = 0; i < table->nr; i++)
478 if (!table->table[i]) {
480 table->table[i] = ctx;
482 spin_unlock(&mm->ioctx_lock);
484 ring = kmap_atomic(ctx->ring_pages[0]);
490 new_nr = (table ? table->nr : 1) * 4;
493 spin_unlock(&mm->ioctx_lock);
495 table = kzalloc(sizeof(*table) + sizeof(struct kioctx *) *
502 spin_lock(&mm->ioctx_lock);
504 old = rcu_dereference(mm->ioctx_table);
507 rcu_assign_pointer(mm->ioctx_table, table);
508 } else if (table->nr > old->nr) {
509 memcpy(table->table, old->table,
510 old->nr * sizeof(struct kioctx *));
512 rcu_assign_pointer(mm->ioctx_table, table);
521 static void aio_nr_sub(unsigned nr)
523 spin_lock(&aio_nr_lock);
524 if (WARN_ON(aio_nr - nr > aio_nr))
528 spin_unlock(&aio_nr_lock);
532 * Allocates and initializes an ioctx. Returns an ERR_PTR if it failed.
534 static struct kioctx *ioctx_alloc(unsigned nr_events)
536 struct mm_struct *mm = current->mm;
541 * We keep track of the number of available ringbuffer slots, to prevent
542 * overflow (reqs_available), and we also use percpu counters for this.
544 * So since up to half the slots might be on other cpu's percpu counters
545 * and unavailable, double nr_events so userspace sees what they
546 * expected: additionally, we move req_batch slots to/from percpu
547 * counters at a time, so make sure that isn't 0:
549 nr_events = max(nr_events, num_possible_cpus() * 4);
552 /* Prevent overflows */
553 if ((nr_events > (0x10000000U / sizeof(struct io_event))) ||
554 (nr_events > (0x10000000U / sizeof(struct kiocb)))) {
555 pr_debug("ENOMEM: nr_events too high\n");
556 return ERR_PTR(-EINVAL);
559 if (!nr_events || (unsigned long)nr_events > (aio_max_nr * 2UL))
560 return ERR_PTR(-EAGAIN);
562 ctx = kmem_cache_zalloc(kioctx_cachep, GFP_KERNEL);
564 return ERR_PTR(-ENOMEM);
566 ctx->max_reqs = nr_events;
568 if (percpu_ref_init(&ctx->users, free_ioctx_users))
571 if (percpu_ref_init(&ctx->reqs, free_ioctx_reqs))
574 spin_lock_init(&ctx->ctx_lock);
575 spin_lock_init(&ctx->completion_lock);
576 mutex_init(&ctx->ring_lock);
577 init_waitqueue_head(&ctx->wait);
579 INIT_LIST_HEAD(&ctx->active_reqs);
581 ctx->cpu = alloc_percpu(struct kioctx_cpu);
585 if (aio_setup_ring(ctx) < 0)
588 atomic_set(&ctx->reqs_available, ctx->nr_events - 1);
589 ctx->req_batch = (ctx->nr_events - 1) / (num_possible_cpus() * 4);
590 if (ctx->req_batch < 1)
593 /* limit the number of system wide aios */
594 spin_lock(&aio_nr_lock);
595 if (aio_nr + nr_events > (aio_max_nr * 2UL) ||
596 aio_nr + nr_events < aio_nr) {
597 spin_unlock(&aio_nr_lock);
601 aio_nr += ctx->max_reqs;
602 spin_unlock(&aio_nr_lock);
604 percpu_ref_get(&ctx->users); /* io_setup() will drop this ref */
606 err = ioctx_add_table(ctx, mm);
610 pr_debug("allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",
611 ctx, ctx->user_id, mm, ctx->nr_events);
615 aio_nr_sub(ctx->max_reqs);
619 free_percpu(ctx->cpu);
620 free_percpu(ctx->reqs.pcpu_count);
621 free_percpu(ctx->users.pcpu_count);
622 kmem_cache_free(kioctx_cachep, ctx);
623 pr_debug("error allocating ioctx %d\n", err);
628 * Cancels all outstanding aio requests on an aio context. Used
629 * when the processes owning a context have all exited to encourage
630 * the rapid destruction of the kioctx.
632 static void kill_ioctx(struct mm_struct *mm, struct kioctx *ctx)
634 if (!atomic_xchg(&ctx->dead, 1)) {
635 struct kioctx_table *table;
637 spin_lock(&mm->ioctx_lock);
639 table = rcu_dereference(mm->ioctx_table);
641 WARN_ON(ctx != table->table[ctx->id]);
642 table->table[ctx->id] = NULL;
644 spin_unlock(&mm->ioctx_lock);
646 /* percpu_ref_kill() will do the necessary call_rcu() */
647 wake_up_all(&ctx->wait);
650 * It'd be more correct to do this in free_ioctx(), after all
651 * the outstanding kiocbs have finished - but by then io_destroy
652 * has already returned, so io_setup() could potentially return
653 * -EAGAIN with no ioctxs actually in use (as far as userspace
656 aio_nr_sub(ctx->max_reqs);
659 vm_munmap(ctx->mmap_base, ctx->mmap_size);
661 percpu_ref_kill(&ctx->users);
665 /* wait_on_sync_kiocb:
666 * Waits on the given sync kiocb to complete.
668 ssize_t wait_on_sync_kiocb(struct kiocb *req)
670 while (!req->ki_ctx) {
671 set_current_state(TASK_UNINTERRUPTIBLE);
676 __set_current_state(TASK_RUNNING);
677 return req->ki_user_data;
679 EXPORT_SYMBOL(wait_on_sync_kiocb);
682 * exit_aio: called when the last user of mm goes away. At this point, there is
683 * no way for any new requests to be submited or any of the io_* syscalls to be
684 * called on the context.
686 * There may be outstanding kiocbs, but free_ioctx() will explicitly wait on
689 void exit_aio(struct mm_struct *mm)
691 struct kioctx_table *table;
697 table = rcu_dereference(mm->ioctx_table);
700 if (!table || i >= table->nr) {
702 rcu_assign_pointer(mm->ioctx_table, NULL);
708 ctx = table->table[i++];
714 * We don't need to bother with munmap() here -
715 * exit_mmap(mm) is coming and it'll unmap everything.
716 * Since aio_free_ring() uses non-zero ->mmap_size
717 * as indicator that it needs to unmap the area,
718 * just set it to 0; aio_free_ring() is the only
719 * place that uses ->mmap_size, so it's safe.
727 static void put_reqs_available(struct kioctx *ctx, unsigned nr)
729 struct kioctx_cpu *kcpu;
732 kcpu = this_cpu_ptr(ctx->cpu);
734 kcpu->reqs_available += nr;
735 while (kcpu->reqs_available >= ctx->req_batch * 2) {
736 kcpu->reqs_available -= ctx->req_batch;
737 atomic_add(ctx->req_batch, &ctx->reqs_available);
743 static bool get_reqs_available(struct kioctx *ctx)
745 struct kioctx_cpu *kcpu;
749 kcpu = this_cpu_ptr(ctx->cpu);
751 if (!kcpu->reqs_available) {
752 int old, avail = atomic_read(&ctx->reqs_available);
755 if (avail < ctx->req_batch)
759 avail = atomic_cmpxchg(&ctx->reqs_available,
760 avail, avail - ctx->req_batch);
761 } while (avail != old);
763 kcpu->reqs_available += ctx->req_batch;
767 kcpu->reqs_available--;
774 * Allocate a slot for an aio request.
775 * Returns NULL if no requests are free.
777 static inline struct kiocb *aio_get_req(struct kioctx *ctx)
781 if (!get_reqs_available(ctx))
784 req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL|__GFP_ZERO);
788 percpu_ref_get(&ctx->reqs);
793 put_reqs_available(ctx, 1);
797 static void kiocb_free(struct kiocb *req)
801 if (req->ki_eventfd != NULL)
802 eventfd_ctx_put(req->ki_eventfd);
803 kmem_cache_free(kiocb_cachep, req);
806 static struct kioctx *lookup_ioctx(unsigned long ctx_id)
808 struct aio_ring __user *ring = (void __user *)ctx_id;
809 struct mm_struct *mm = current->mm;
810 struct kioctx *ctx, *ret = NULL;
811 struct kioctx_table *table;
814 if (get_user(id, &ring->id))
818 table = rcu_dereference(mm->ioctx_table);
820 if (!table || id >= table->nr)
823 ctx = table->table[id];
824 if (ctx && ctx->user_id == ctx_id) {
825 percpu_ref_get(&ctx->users);
834 * Called when the io request on the given iocb is complete.
836 void aio_complete(struct kiocb *iocb, long res, long res2)
838 struct kioctx *ctx = iocb->ki_ctx;
839 struct aio_ring *ring;
840 struct io_event *ev_page, *event;
845 * Special case handling for sync iocbs:
846 * - events go directly into the iocb for fast handling
847 * - the sync task with the iocb in its stack holds the single iocb
848 * ref, no other paths have a way to get another ref
849 * - the sync task helpfully left a reference to itself in the iocb
851 if (is_sync_kiocb(iocb)) {
852 iocb->ki_user_data = res;
854 iocb->ki_ctx = ERR_PTR(-EXDEV);
855 wake_up_process(iocb->ki_obj.tsk);
859 if (iocb->ki_list.next) {
862 spin_lock_irqsave(&ctx->ctx_lock, flags);
863 list_del(&iocb->ki_list);
864 spin_unlock_irqrestore(&ctx->ctx_lock, flags);
868 * Add a completion event to the ring buffer. Must be done holding
869 * ctx->completion_lock to prevent other code from messing with the tail
870 * pointer since we might be called from irq context.
872 spin_lock_irqsave(&ctx->completion_lock, flags);
875 pos = tail + AIO_EVENTS_OFFSET;
877 if (++tail >= ctx->nr_events)
880 ev_page = kmap_atomic(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
881 event = ev_page + pos % AIO_EVENTS_PER_PAGE;
883 event->obj = (u64)(unsigned long)iocb->ki_obj.user;
884 event->data = iocb->ki_user_data;
888 kunmap_atomic(ev_page);
889 flush_dcache_page(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
891 pr_debug("%p[%u]: %p: %p %Lx %lx %lx\n",
892 ctx, tail, iocb, iocb->ki_obj.user, iocb->ki_user_data,
895 /* after flagging the request as done, we
896 * must never even look at it again
898 smp_wmb(); /* make event visible before updating tail */
902 ring = kmap_atomic(ctx->ring_pages[0]);
905 flush_dcache_page(ctx->ring_pages[0]);
907 spin_unlock_irqrestore(&ctx->completion_lock, flags);
909 pr_debug("added to ring %p at [%u]\n", iocb, tail);
912 * Check if the user asked us to deliver the result through an
913 * eventfd. The eventfd_signal() function is safe to be called
916 if (iocb->ki_eventfd != NULL)
917 eventfd_signal(iocb->ki_eventfd, 1);
919 /* everything turned out well, dispose of the aiocb. */
923 * We have to order our ring_info tail store above and test
924 * of the wait list below outside the wait lock. This is
925 * like in wake_up_bit() where clearing a bit has to be
926 * ordered with the unlocked test.
930 if (waitqueue_active(&ctx->wait))
933 percpu_ref_put(&ctx->reqs);
935 EXPORT_SYMBOL(aio_complete);
938 * Pull an event off of the ioctx's event ring. Returns the number of
941 static long aio_read_events_ring(struct kioctx *ctx,
942 struct io_event __user *event, long nr)
944 struct aio_ring *ring;
945 unsigned head, tail, pos;
949 mutex_lock(&ctx->ring_lock);
951 ring = kmap_atomic(ctx->ring_pages[0]);
956 pr_debug("h%u t%u m%u\n", head, tail, ctx->nr_events);
966 avail = (head <= tail ? tail : ctx->nr_events) - head;
970 avail = min(avail, nr - ret);
971 avail = min_t(long, avail, AIO_EVENTS_PER_PAGE -
972 ((head + AIO_EVENTS_OFFSET) % AIO_EVENTS_PER_PAGE));
974 pos = head + AIO_EVENTS_OFFSET;
975 page = ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE];
976 pos %= AIO_EVENTS_PER_PAGE;
979 copy_ret = copy_to_user(event + ret, ev + pos,
980 sizeof(*ev) * avail);
983 if (unlikely(copy_ret)) {
990 head %= ctx->nr_events;
993 ring = kmap_atomic(ctx->ring_pages[0]);
996 flush_dcache_page(ctx->ring_pages[0]);
998 pr_debug("%li h%u t%u\n", ret, head, tail);
1000 put_reqs_available(ctx, ret);
1002 mutex_unlock(&ctx->ring_lock);
1007 static bool aio_read_events(struct kioctx *ctx, long min_nr, long nr,
1008 struct io_event __user *event, long *i)
1010 long ret = aio_read_events_ring(ctx, event + *i, nr - *i);
1015 if (unlikely(atomic_read(&ctx->dead)))
1021 return ret < 0 || *i >= min_nr;
1024 static long read_events(struct kioctx *ctx, long min_nr, long nr,
1025 struct io_event __user *event,
1026 struct timespec __user *timeout)
1028 ktime_t until = { .tv64 = KTIME_MAX };
1034 if (unlikely(copy_from_user(&ts, timeout, sizeof(ts))))
1037 until = timespec_to_ktime(ts);
1041 * Note that aio_read_events() is being called as the conditional - i.e.
1042 * we're calling it after prepare_to_wait() has set task state to
1043 * TASK_INTERRUPTIBLE.
1045 * But aio_read_events() can block, and if it blocks it's going to flip
1046 * the task state back to TASK_RUNNING.
1048 * This should be ok, provided it doesn't flip the state back to
1049 * TASK_RUNNING and return 0 too much - that causes us to spin. That
1050 * will only happen if the mutex_lock() call blocks, and we then find
1051 * the ringbuffer empty. So in practice we should be ok, but it's
1052 * something to be aware of when touching this code.
1054 wait_event_interruptible_hrtimeout(ctx->wait,
1055 aio_read_events(ctx, min_nr, nr, event, &ret), until);
1057 if (!ret && signal_pending(current))
1064 * Create an aio_context capable of receiving at least nr_events.
1065 * ctxp must not point to an aio_context that already exists, and
1066 * must be initialized to 0 prior to the call. On successful
1067 * creation of the aio_context, *ctxp is filled in with the resulting
1068 * handle. May fail with -EINVAL if *ctxp is not initialized,
1069 * if the specified nr_events exceeds internal limits. May fail
1070 * with -EAGAIN if the specified nr_events exceeds the user's limit
1071 * of available events. May fail with -ENOMEM if insufficient kernel
1072 * resources are available. May fail with -EFAULT if an invalid
1073 * pointer is passed for ctxp. Will fail with -ENOSYS if not
1076 SYSCALL_DEFINE2(io_setup, unsigned, nr_events, aio_context_t __user *, ctxp)
1078 struct kioctx *ioctx = NULL;
1082 ret = get_user(ctx, ctxp);
1087 if (unlikely(ctx || nr_events == 0)) {
1088 pr_debug("EINVAL: io_setup: ctx %lu nr_events %u\n",
1093 ioctx = ioctx_alloc(nr_events);
1094 ret = PTR_ERR(ioctx);
1095 if (!IS_ERR(ioctx)) {
1096 ret = put_user(ioctx->user_id, ctxp);
1098 kill_ioctx(current->mm, ioctx);
1099 percpu_ref_put(&ioctx->users);
1107 * Destroy the aio_context specified. May cancel any outstanding
1108 * AIOs and block on completion. Will fail with -ENOSYS if not
1109 * implemented. May fail with -EINVAL if the context pointed to
1112 SYSCALL_DEFINE1(io_destroy, aio_context_t, ctx)
1114 struct kioctx *ioctx = lookup_ioctx(ctx);
1115 if (likely(NULL != ioctx)) {
1116 kill_ioctx(current->mm, ioctx);
1117 percpu_ref_put(&ioctx->users);
1120 pr_debug("EINVAL: io_destroy: invalid context id\n");
1124 typedef ssize_t (aio_rw_op)(struct kiocb *, const struct iovec *,
1125 unsigned long, loff_t);
1127 static ssize_t aio_setup_vectored_rw(struct kiocb *kiocb,
1128 int rw, char __user *buf,
1129 unsigned long *nr_segs,
1130 struct iovec **iovec,
1135 *nr_segs = kiocb->ki_nbytes;
1137 #ifdef CONFIG_COMPAT
1139 ret = compat_rw_copy_check_uvector(rw,
1140 (struct compat_iovec __user *)buf,
1141 *nr_segs, 1, *iovec, iovec);
1144 ret = rw_copy_check_uvector(rw,
1145 (struct iovec __user *)buf,
1146 *nr_segs, 1, *iovec, iovec);
1150 /* ki_nbytes now reflect bytes instead of segs */
1151 kiocb->ki_nbytes = ret;
1155 static ssize_t aio_setup_single_vector(struct kiocb *kiocb,
1156 int rw, char __user *buf,
1157 unsigned long *nr_segs,
1158 struct iovec *iovec)
1160 if (unlikely(!access_ok(!rw, buf, kiocb->ki_nbytes)))
1163 iovec->iov_base = buf;
1164 iovec->iov_len = kiocb->ki_nbytes;
1171 * Performs the initial checks and aio retry method
1172 * setup for the kiocb at the time of io submission.
1174 static ssize_t aio_run_iocb(struct kiocb *req, unsigned opcode,
1175 char __user *buf, bool compat)
1177 struct file *file = req->ki_filp;
1179 unsigned long nr_segs;
1183 struct iovec inline_vec, *iovec = &inline_vec;
1186 case IOCB_CMD_PREAD:
1187 case IOCB_CMD_PREADV:
1190 rw_op = file->f_op->aio_read;
1193 case IOCB_CMD_PWRITE:
1194 case IOCB_CMD_PWRITEV:
1197 rw_op = file->f_op->aio_write;
1200 if (unlikely(!(file->f_mode & mode)))
1206 ret = (opcode == IOCB_CMD_PREADV ||
1207 opcode == IOCB_CMD_PWRITEV)
1208 ? aio_setup_vectored_rw(req, rw, buf, &nr_segs,
1210 : aio_setup_single_vector(req, rw, buf, &nr_segs,
1215 ret = rw_verify_area(rw, file, &req->ki_pos, req->ki_nbytes);
1217 if (iovec != &inline_vec)
1222 req->ki_nbytes = ret;
1224 /* XXX: move/kill - rw_verify_area()? */
1225 /* This matches the pread()/pwrite() logic */
1226 if (req->ki_pos < 0) {
1232 file_start_write(file);
1234 ret = rw_op(req, iovec, nr_segs, req->ki_pos);
1237 file_end_write(file);
1240 case IOCB_CMD_FDSYNC:
1241 if (!file->f_op->aio_fsync)
1244 ret = file->f_op->aio_fsync(req, 1);
1247 case IOCB_CMD_FSYNC:
1248 if (!file->f_op->aio_fsync)
1251 ret = file->f_op->aio_fsync(req, 0);
1255 pr_debug("EINVAL: no operation provided\n");
1259 if (iovec != &inline_vec)
1262 if (ret != -EIOCBQUEUED) {
1264 * There's no easy way to restart the syscall since other AIO's
1265 * may be already running. Just fail this IO with EINTR.
1267 if (unlikely(ret == -ERESTARTSYS || ret == -ERESTARTNOINTR ||
1268 ret == -ERESTARTNOHAND ||
1269 ret == -ERESTART_RESTARTBLOCK))
1271 aio_complete(req, ret, 0);
1277 static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
1278 struct iocb *iocb, bool compat)
1283 /* enforce forwards compatibility on users */
1284 if (unlikely(iocb->aio_reserved1 || iocb->aio_reserved2)) {
1285 pr_debug("EINVAL: reserve field set\n");
1289 /* prevent overflows */
1291 (iocb->aio_buf != (unsigned long)iocb->aio_buf) ||
1292 (iocb->aio_nbytes != (size_t)iocb->aio_nbytes) ||
1293 ((ssize_t)iocb->aio_nbytes < 0)
1295 pr_debug("EINVAL: io_submit: overflow check\n");
1299 req = aio_get_req(ctx);
1303 req->ki_filp = fget(iocb->aio_fildes);
1304 if (unlikely(!req->ki_filp)) {
1309 if (iocb->aio_flags & IOCB_FLAG_RESFD) {
1311 * If the IOCB_FLAG_RESFD flag of aio_flags is set, get an
1312 * instance of the file* now. The file descriptor must be
1313 * an eventfd() fd, and will be signaled for each completed
1314 * event using the eventfd_signal() function.
1316 req->ki_eventfd = eventfd_ctx_fdget((int) iocb->aio_resfd);
1317 if (IS_ERR(req->ki_eventfd)) {
1318 ret = PTR_ERR(req->ki_eventfd);
1319 req->ki_eventfd = NULL;
1324 ret = put_user(KIOCB_KEY, &user_iocb->aio_key);
1325 if (unlikely(ret)) {
1326 pr_debug("EFAULT: aio_key\n");
1330 req->ki_obj.user = user_iocb;
1331 req->ki_user_data = iocb->aio_data;
1332 req->ki_pos = iocb->aio_offset;
1333 req->ki_nbytes = iocb->aio_nbytes;
1335 ret = aio_run_iocb(req, iocb->aio_lio_opcode,
1336 (char __user *)(unsigned long)iocb->aio_buf,
1343 put_reqs_available(ctx, 1);
1344 percpu_ref_put(&ctx->reqs);
1349 long do_io_submit(aio_context_t ctx_id, long nr,
1350 struct iocb __user *__user *iocbpp, bool compat)
1355 struct blk_plug plug;
1357 if (unlikely(nr < 0))
1360 if (unlikely(nr > LONG_MAX/sizeof(*iocbpp)))
1361 nr = LONG_MAX/sizeof(*iocbpp);
1363 if (unlikely(!access_ok(VERIFY_READ, iocbpp, (nr*sizeof(*iocbpp)))))
1366 ctx = lookup_ioctx(ctx_id);
1367 if (unlikely(!ctx)) {
1368 pr_debug("EINVAL: invalid context id\n");
1372 blk_start_plug(&plug);
1375 * AKPM: should this return a partial result if some of the IOs were
1376 * successfully submitted?
1378 for (i=0; i<nr; i++) {
1379 struct iocb __user *user_iocb;
1382 if (unlikely(__get_user(user_iocb, iocbpp + i))) {
1387 if (unlikely(copy_from_user(&tmp, user_iocb, sizeof(tmp)))) {
1392 ret = io_submit_one(ctx, user_iocb, &tmp, compat);
1396 blk_finish_plug(&plug);
1398 percpu_ref_put(&ctx->users);
1403 * Queue the nr iocbs pointed to by iocbpp for processing. Returns
1404 * the number of iocbs queued. May return -EINVAL if the aio_context
1405 * specified by ctx_id is invalid, if nr is < 0, if the iocb at
1406 * *iocbpp[0] is not properly initialized, if the operation specified
1407 * is invalid for the file descriptor in the iocb. May fail with
1408 * -EFAULT if any of the data structures point to invalid data. May
1409 * fail with -EBADF if the file descriptor specified in the first
1410 * iocb is invalid. May fail with -EAGAIN if insufficient resources
1411 * are available to queue any iocbs. Will return 0 if nr is 0. Will
1412 * fail with -ENOSYS if not implemented.
1414 SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
1415 struct iocb __user * __user *, iocbpp)
1417 return do_io_submit(ctx_id, nr, iocbpp, 0);
1421 * Finds a given iocb for cancellation.
1423 static struct kiocb *lookup_kiocb(struct kioctx *ctx, struct iocb __user *iocb,
1426 struct list_head *pos;
1428 assert_spin_locked(&ctx->ctx_lock);
1430 if (key != KIOCB_KEY)
1433 /* TODO: use a hash or array, this sucks. */
1434 list_for_each(pos, &ctx->active_reqs) {
1435 struct kiocb *kiocb = list_kiocb(pos);
1436 if (kiocb->ki_obj.user == iocb)
1443 * Attempts to cancel an iocb previously passed to io_submit. If
1444 * the operation is successfully cancelled, the resulting event is
1445 * copied into the memory pointed to by result without being placed
1446 * into the completion queue and 0 is returned. May fail with
1447 * -EFAULT if any of the data structures pointed to are invalid.
1448 * May fail with -EINVAL if aio_context specified by ctx_id is
1449 * invalid. May fail with -EAGAIN if the iocb specified was not
1450 * cancelled. Will fail with -ENOSYS if not implemented.
1452 SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
1453 struct io_event __user *, result)
1456 struct kiocb *kiocb;
1460 ret = get_user(key, &iocb->aio_key);
1464 ctx = lookup_ioctx(ctx_id);
1468 spin_lock_irq(&ctx->ctx_lock);
1470 kiocb = lookup_kiocb(ctx, iocb, key);
1472 ret = kiocb_cancel(ctx, kiocb);
1476 spin_unlock_irq(&ctx->ctx_lock);
1480 * The result argument is no longer used - the io_event is
1481 * always delivered via the ring buffer. -EINPROGRESS indicates
1482 * cancellation is progress:
1487 percpu_ref_put(&ctx->users);
1493 * Attempts to read at least min_nr events and up to nr events from
1494 * the completion queue for the aio_context specified by ctx_id. If
1495 * it succeeds, the number of read events is returned. May fail with
1496 * -EINVAL if ctx_id is invalid, if min_nr is out of range, if nr is
1497 * out of range, if timeout is out of range. May fail with -EFAULT
1498 * if any of the memory specified is invalid. May return 0 or
1499 * < min_nr if the timeout specified by timeout has elapsed
1500 * before sufficient events are available, where timeout == NULL
1501 * specifies an infinite timeout. Note that the timeout pointed to by
1502 * timeout is relative. Will fail with -ENOSYS if not implemented.
1504 SYSCALL_DEFINE5(io_getevents, aio_context_t, ctx_id,
1507 struct io_event __user *, events,
1508 struct timespec __user *, timeout)
1510 struct kioctx *ioctx = lookup_ioctx(ctx_id);
1513 if (likely(ioctx)) {
1514 if (likely(min_nr <= nr && min_nr >= 0))
1515 ret = read_events(ioctx, min_nr, nr, events, timeout);
1516 percpu_ref_put(&ioctx->users);