linux/fs/aio.c
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   1/*
   2 *      An async IO implementation for Linux
   3 *      Written by Benjamin LaHaise <bcrl@kvack.org>
   4 *
   5 *      Implements an efficient asynchronous io interface.
   6 *
   7 *      Copyright 2000, 2001, 2002 Red Hat, Inc.  All Rights Reserved.
   8 *
   9 *      See ../COPYING for licensing terms.
  10 */
  11#define pr_fmt(fmt) "%s: " fmt, __func__
  12
  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>
  22
  23#include <linux/sched.h>
  24#include <linux/fs.h>
  25#include <linux/file.h>
  26#include <linux/mm.h>
  27#include <linux/mman.h>
  28#include <linux/mmu_context.h>
  29#include <linux/slab.h>
  30#include <linux/timer.h>
  31#include <linux/aio.h>
  32#include <linux/highmem.h>
  33#include <linux/workqueue.h>
  34#include <linux/security.h>
  35#include <linux/eventfd.h>
  36#include <linux/blkdev.h>
  37#include <linux/compat.h>
  38
  39#include <asm/kmap_types.h>
  40#include <asm/uaccess.h>
  41
  42#define AIO_RING_MAGIC                  0xa10a10a1
  43#define AIO_RING_COMPAT_FEATURES        1
  44#define AIO_RING_INCOMPAT_FEATURES      0
  45struct aio_ring {
  46        unsigned        id;     /* kernel internal index number */
  47        unsigned        nr;     /* number of io_events */
  48        unsigned        head;
  49        unsigned        tail;
  50
  51        unsigned        magic;
  52        unsigned        compat_features;
  53        unsigned        incompat_features;
  54        unsigned        header_length;  /* size of aio_ring */
  55
  56
  57        struct io_event         io_events[0];
  58}; /* 128 bytes + ring size */
  59
  60#define AIO_RING_PAGES  8
  61
  62struct kioctx {
  63        atomic_t                users;
  64        atomic_t                dead;
  65
  66        /* This needs improving */
  67        unsigned long           user_id;
  68        struct hlist_node       list;
  69
  70        /*
  71         * This is what userspace passed to io_setup(), it's not used for
  72         * anything but counting against the global max_reqs quota.
  73         *
  74         * The real limit is nr_events - 1, which will be larger (see
  75         * aio_setup_ring())
  76         */
  77        unsigned                max_reqs;
  78
  79        /* Size of ringbuffer, in units of struct io_event */
  80        unsigned                nr_events;
  81
  82        unsigned long           mmap_base;
  83        unsigned long           mmap_size;
  84
  85        struct page             **ring_pages;
  86        long                    nr_pages;
  87
  88        struct rcu_head         rcu_head;
  89        struct work_struct      rcu_work;
  90
  91        struct {
  92                atomic_t        reqs_active;
  93        } ____cacheline_aligned_in_smp;
  94
  95        struct {
  96                spinlock_t      ctx_lock;
  97                struct list_head active_reqs;   /* used for cancellation */
  98        } ____cacheline_aligned_in_smp;
  99
 100        struct {
 101                struct mutex    ring_lock;
 102                wait_queue_head_t wait;
 103        } ____cacheline_aligned_in_smp;
 104
 105        struct {
 106                unsigned        tail;
 107                spinlock_t      completion_lock;
 108        } ____cacheline_aligned_in_smp;
 109
 110        struct page             *internal_pages[AIO_RING_PAGES];
 111};
 112
 113/*------ sysctl variables----*/
 114static DEFINE_SPINLOCK(aio_nr_lock);
 115unsigned long aio_nr;           /* current system wide number of aio requests */
 116unsigned long aio_max_nr = 0x10000; /* system wide maximum number of aio requests */
 117/*----end sysctl variables---*/
 118
 119static struct kmem_cache        *kiocb_cachep;
 120static struct kmem_cache        *kioctx_cachep;
 121
 122/* aio_setup
 123 *      Creates the slab caches used by the aio routines, panic on
 124 *      failure as this is done early during the boot sequence.
 125 */
 126static int __init aio_setup(void)
 127{
 128        kiocb_cachep = KMEM_CACHE(kiocb, SLAB_HWCACHE_ALIGN|SLAB_PANIC);
 129        kioctx_cachep = KMEM_CACHE(kioctx,SLAB_HWCACHE_ALIGN|SLAB_PANIC);
 130
 131        pr_debug("sizeof(struct page) = %zu\n", sizeof(struct page));
 132
 133        return 0;
 134}
 135__initcall(aio_setup);
 136
 137static void aio_free_ring(struct kioctx *ctx)
 138{
 139        long i;
 140
 141        for (i = 0; i < ctx->nr_pages; i++)
 142                put_page(ctx->ring_pages[i]);
 143
 144        if (ctx->ring_pages && ctx->ring_pages != ctx->internal_pages)
 145                kfree(ctx->ring_pages);
 146}
 147
 148static int aio_setup_ring(struct kioctx *ctx)
 149{
 150        struct aio_ring *ring;
 151        unsigned nr_events = ctx->max_reqs;
 152        struct mm_struct *mm = current->mm;
 153        unsigned long size, populate;
 154        int nr_pages;
 155
 156        /* Compensate for the ring buffer's head/tail overlap entry */
 157        nr_events += 2; /* 1 is required, 2 for good luck */
 158
 159        size = sizeof(struct aio_ring);
 160        size += sizeof(struct io_event) * nr_events;
 161        nr_pages = (size + PAGE_SIZE-1) >> PAGE_SHIFT;
 162
 163        if (nr_pages < 0)
 164                return -EINVAL;
 165
 166        nr_events = (PAGE_SIZE * nr_pages - sizeof(struct aio_ring)) / sizeof(struct io_event);
 167
 168        ctx->nr_events = 0;
 169        ctx->ring_pages = ctx->internal_pages;
 170        if (nr_pages > AIO_RING_PAGES) {
 171                ctx->ring_pages = kcalloc(nr_pages, sizeof(struct page *),
 172                                          GFP_KERNEL);
 173                if (!ctx->ring_pages)
 174                        return -ENOMEM;
 175        }
 176
 177        ctx->mmap_size = nr_pages * PAGE_SIZE;
 178        pr_debug("attempting mmap of %lu bytes\n", ctx->mmap_size);
 179        down_write(&mm->mmap_sem);
 180        ctx->mmap_base = do_mmap_pgoff(NULL, 0, ctx->mmap_size,
 181                                       PROT_READ|PROT_WRITE,
 182                                       MAP_ANONYMOUS|MAP_PRIVATE, 0, &populate);
 183        if (IS_ERR((void *)ctx->mmap_base)) {
 184                up_write(&mm->mmap_sem);
 185                ctx->mmap_size = 0;
 186                aio_free_ring(ctx);
 187                return -EAGAIN;
 188        }
 189
 190        pr_debug("mmap address: 0x%08lx\n", ctx->mmap_base);
 191        ctx->nr_pages = get_user_pages(current, mm, ctx->mmap_base, nr_pages,
 192                                       1, 0, ctx->ring_pages, NULL);
 193        up_write(&mm->mmap_sem);
 194
 195        if (unlikely(ctx->nr_pages != nr_pages)) {
 196                aio_free_ring(ctx);
 197                return -EAGAIN;
 198        }
 199        if (populate)
 200                mm_populate(ctx->mmap_base, populate);
 201
 202        ctx->user_id = ctx->mmap_base;
 203        ctx->nr_events = nr_events; /* trusted copy */
 204
 205        ring = kmap_atomic(ctx->ring_pages[0]);
 206        ring->nr = nr_events;   /* user copy */
 207        ring->id = ctx->user_id;
 208        ring->head = ring->tail = 0;
 209        ring->magic = AIO_RING_MAGIC;
 210        ring->compat_features = AIO_RING_COMPAT_FEATURES;
 211        ring->incompat_features = AIO_RING_INCOMPAT_FEATURES;
 212        ring->header_length = sizeof(struct aio_ring);
 213        kunmap_atomic(ring);
 214        flush_dcache_page(ctx->ring_pages[0]);
 215
 216        return 0;
 217}
 218
 219#define AIO_EVENTS_PER_PAGE     (PAGE_SIZE / sizeof(struct io_event))
 220#define AIO_EVENTS_FIRST_PAGE   ((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event))
 221#define AIO_EVENTS_OFFSET       (AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE)
 222
 223void kiocb_set_cancel_fn(struct kiocb *req, kiocb_cancel_fn *cancel)
 224{
 225        struct kioctx *ctx = req->ki_ctx;
 226        unsigned long flags;
 227
 228        spin_lock_irqsave(&ctx->ctx_lock, flags);
 229
 230        if (!req->ki_list.next)
 231                list_add(&req->ki_list, &ctx->active_reqs);
 232
 233        req->ki_cancel = cancel;
 234
 235        spin_unlock_irqrestore(&ctx->ctx_lock, flags);
 236}
 237EXPORT_SYMBOL(kiocb_set_cancel_fn);
 238
 239static int kiocb_cancel(struct kioctx *ctx, struct kiocb *kiocb,
 240                        struct io_event *res)
 241{
 242        kiocb_cancel_fn *old, *cancel;
 243        int ret = -EINVAL;
 244
 245        /*
 246         * Don't want to set kiocb->ki_cancel = KIOCB_CANCELLED unless it
 247         * actually has a cancel function, hence the cmpxchg()
 248         */
 249
 250        cancel = ACCESS_ONCE(kiocb->ki_cancel);
 251        do {
 252                if (!cancel || cancel == KIOCB_CANCELLED)
 253                        return ret;
 254
 255                old = cancel;
 256                cancel = cmpxchg(&kiocb->ki_cancel, old, KIOCB_CANCELLED);
 257        } while (cancel != old);
 258
 259        atomic_inc(&kiocb->ki_users);
 260        spin_unlock_irq(&ctx->ctx_lock);
 261
 262        memset(res, 0, sizeof(*res));
 263        res->obj = (u64)(unsigned long)kiocb->ki_obj.user;
 264        res->data = kiocb->ki_user_data;
 265        ret = cancel(kiocb, res);
 266
 267        spin_lock_irq(&ctx->ctx_lock);
 268
 269        return ret;
 270}
 271
 272static void free_ioctx_rcu(struct rcu_head *head)
 273{
 274        struct kioctx *ctx = container_of(head, struct kioctx, rcu_head);
 275        kmem_cache_free(kioctx_cachep, ctx);
 276}
 277
 278/*
 279 * When this function runs, the kioctx has been removed from the "hash table"
 280 * and ctx->users has dropped to 0, so we know no more kiocbs can be submitted -
 281 * now it's safe to cancel any that need to be.
 282 */
 283static void free_ioctx(struct kioctx *ctx)
 284{
 285        struct aio_ring *ring;
 286        struct io_event res;
 287        struct kiocb *req;
 288        unsigned head, avail;
 289
 290        spin_lock_irq(&ctx->ctx_lock);
 291
 292        while (!list_empty(&ctx->active_reqs)) {
 293                req = list_first_entry(&ctx->active_reqs,
 294                                       struct kiocb, ki_list);
 295
 296                list_del_init(&req->ki_list);
 297                kiocb_cancel(ctx, req, &res);
 298        }
 299
 300        spin_unlock_irq(&ctx->ctx_lock);
 301
 302        ring = kmap_atomic(ctx->ring_pages[0]);
 303        head = ring->head;
 304        kunmap_atomic(ring);
 305
 306        while (atomic_read(&ctx->reqs_active) > 0) {
 307                wait_event(ctx->wait,
 308                                head != ctx->tail ||
 309                                atomic_read(&ctx->reqs_active) <= 0);
 310
 311                avail = (head <= ctx->tail ? ctx->tail : ctx->nr_events) - head;
 312
 313                atomic_sub(avail, &ctx->reqs_active);
 314                head += avail;
 315                head %= ctx->nr_events;
 316        }
 317
 318        WARN_ON(atomic_read(&ctx->reqs_active) < 0);
 319
 320        aio_free_ring(ctx);
 321
 322        pr_debug("freeing %p\n", ctx);
 323
 324        /*
 325         * Here the call_rcu() is between the wait_event() for reqs_active to
 326         * hit 0, and freeing the ioctx.
 327         *
 328         * aio_complete() decrements reqs_active, but it has to touch the ioctx
 329         * after to issue a wakeup so we use rcu.
 330         */
 331        call_rcu(&ctx->rcu_head, free_ioctx_rcu);
 332}
 333
 334static void put_ioctx(struct kioctx *ctx)
 335{
 336        if (unlikely(atomic_dec_and_test(&ctx->users)))
 337                free_ioctx(ctx);
 338}
 339
 340/* ioctx_alloc
 341 *      Allocates and initializes an ioctx.  Returns an ERR_PTR if it failed.
 342 */
 343static struct kioctx *ioctx_alloc(unsigned nr_events)
 344{
 345        struct mm_struct *mm = current->mm;
 346        struct kioctx *ctx;
 347        int err = -ENOMEM;
 348
 349        /* Prevent overflows */
 350        if ((nr_events > (0x10000000U / sizeof(struct io_event))) ||
 351            (nr_events > (0x10000000U / sizeof(struct kiocb)))) {
 352                pr_debug("ENOMEM: nr_events too high\n");
 353                return ERR_PTR(-EINVAL);
 354        }
 355
 356        if (!nr_events || (unsigned long)nr_events > aio_max_nr)
 357                return ERR_PTR(-EAGAIN);
 358
 359        ctx = kmem_cache_zalloc(kioctx_cachep, GFP_KERNEL);
 360        if (!ctx)
 361                return ERR_PTR(-ENOMEM);
 362
 363        ctx->max_reqs = nr_events;
 364
 365        atomic_set(&ctx->users, 2);
 366        atomic_set(&ctx->dead, 0);
 367        spin_lock_init(&ctx->ctx_lock);
 368        spin_lock_init(&ctx->completion_lock);
 369        mutex_init(&ctx->ring_lock);
 370        init_waitqueue_head(&ctx->wait);
 371
 372        INIT_LIST_HEAD(&ctx->active_reqs);
 373
 374        if (aio_setup_ring(ctx) < 0)
 375                goto out_freectx;
 376
 377        /* limit the number of system wide aios */
 378        spin_lock(&aio_nr_lock);
 379        if (aio_nr + nr_events > aio_max_nr ||
 380            aio_nr + nr_events < aio_nr) {
 381                spin_unlock(&aio_nr_lock);
 382                goto out_cleanup;
 383        }
 384        aio_nr += ctx->max_reqs;
 385        spin_unlock(&aio_nr_lock);
 386
 387        /* now link into global list. */
 388        spin_lock(&mm->ioctx_lock);
 389        hlist_add_head_rcu(&ctx->list, &mm->ioctx_list);
 390        spin_unlock(&mm->ioctx_lock);
 391
 392        pr_debug("allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",
 393                 ctx, ctx->user_id, mm, ctx->nr_events);
 394        return ctx;
 395
 396out_cleanup:
 397        err = -EAGAIN;
 398        aio_free_ring(ctx);
 399out_freectx:
 400        kmem_cache_free(kioctx_cachep, ctx);
 401        pr_debug("error allocating ioctx %d\n", err);
 402        return ERR_PTR(err);
 403}
 404
 405static void kill_ioctx_work(struct work_struct *work)
 406{
 407        struct kioctx *ctx = container_of(work, struct kioctx, rcu_work);
 408
 409        wake_up_all(&ctx->wait);
 410        put_ioctx(ctx);
 411}
 412
 413static void kill_ioctx_rcu(struct rcu_head *head)
 414{
 415        struct kioctx *ctx = container_of(head, struct kioctx, rcu_head);
 416
 417        INIT_WORK(&ctx->rcu_work, kill_ioctx_work);
 418        schedule_work(&ctx->rcu_work);
 419}
 420
 421/* kill_ioctx
 422 *      Cancels all outstanding aio requests on an aio context.  Used
 423 *      when the processes owning a context have all exited to encourage
 424 *      the rapid destruction of the kioctx.
 425 */
 426static void kill_ioctx(struct kioctx *ctx)
 427{
 428        if (!atomic_xchg(&ctx->dead, 1)) {
 429                hlist_del_rcu(&ctx->list);
 430
 431                /*
 432                 * It'd be more correct to do this in free_ioctx(), after all
 433                 * the outstanding kiocbs have finished - but by then io_destroy
 434                 * has already returned, so io_setup() could potentially return
 435                 * -EAGAIN with no ioctxs actually in use (as far as userspace
 436                 *  could tell).
 437                 */
 438                spin_lock(&aio_nr_lock);
 439                BUG_ON(aio_nr - ctx->max_reqs > aio_nr);
 440                aio_nr -= ctx->max_reqs;
 441                spin_unlock(&aio_nr_lock);
 442
 443                if (ctx->mmap_size)
 444                        vm_munmap(ctx->mmap_base, ctx->mmap_size);
 445
 446                /* Between hlist_del_rcu() and dropping the initial ref */
 447                call_rcu(&ctx->rcu_head, kill_ioctx_rcu);
 448        }
 449}
 450
 451/* wait_on_sync_kiocb:
 452 *      Waits on the given sync kiocb to complete.
 453 */
 454ssize_t wait_on_sync_kiocb(struct kiocb *iocb)
 455{
 456        while (atomic_read(&iocb->ki_users)) {
 457                set_current_state(TASK_UNINTERRUPTIBLE);
 458                if (!atomic_read(&iocb->ki_users))
 459                        break;
 460                io_schedule();
 461        }
 462        __set_current_state(TASK_RUNNING);
 463        return iocb->ki_user_data;
 464}
 465EXPORT_SYMBOL(wait_on_sync_kiocb);
 466
 467/*
 468 * exit_aio: called when the last user of mm goes away.  At this point, there is
 469 * no way for any new requests to be submited or any of the io_* syscalls to be
 470 * called on the context.
 471 *
 472 * There may be outstanding kiocbs, but free_ioctx() will explicitly wait on
 473 * them.
 474 */
 475void exit_aio(struct mm_struct *mm)
 476{
 477        struct kioctx *ctx;
 478        struct hlist_node *n;
 479
 480        hlist_for_each_entry_safe(ctx, n, &mm->ioctx_list, list) {
 481                if (1 != atomic_read(&ctx->users))
 482                        printk(KERN_DEBUG
 483                                "exit_aio:ioctx still alive: %d %d %d\n",
 484                                atomic_read(&ctx->users),
 485                                atomic_read(&ctx->dead),
 486                                atomic_read(&ctx->reqs_active));
 487                /*
 488                 * We don't need to bother with munmap() here -
 489                 * exit_mmap(mm) is coming and it'll unmap everything.
 490                 * Since aio_free_ring() uses non-zero ->mmap_size
 491                 * as indicator that it needs to unmap the area,
 492                 * just set it to 0; aio_free_ring() is the only
 493                 * place that uses ->mmap_size, so it's safe.
 494                 */
 495                ctx->mmap_size = 0;
 496
 497                kill_ioctx(ctx);
 498        }
 499}
 500
 501/* aio_get_req
 502 *      Allocate a slot for an aio request.  Increments the ki_users count
 503 * of the kioctx so that the kioctx stays around until all requests are
 504 * complete.  Returns NULL if no requests are free.
 505 *
 506 * Returns with kiocb->ki_users set to 2.  The io submit code path holds
 507 * an extra reference while submitting the i/o.
 508 * This prevents races between the aio code path referencing the
 509 * req (after submitting it) and aio_complete() freeing the req.
 510 */
 511static inline struct kiocb *aio_get_req(struct kioctx *ctx)
 512{
 513        struct kiocb *req;
 514
 515        if (atomic_read(&ctx->reqs_active) >= ctx->nr_events)
 516                return NULL;
 517
 518        if (atomic_inc_return(&ctx->reqs_active) > ctx->nr_events - 1)
 519                goto out_put;
 520
 521        req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL|__GFP_ZERO);
 522        if (unlikely(!req))
 523                goto out_put;
 524
 525        atomic_set(&req->ki_users, 2);
 526        req->ki_ctx = ctx;
 527
 528        return req;
 529out_put:
 530        atomic_dec(&ctx->reqs_active);
 531        return NULL;
 532}
 533
 534static void kiocb_free(struct kiocb *req)
 535{
 536        if (req->ki_filp)
 537                fput(req->ki_filp);
 538        if (req->ki_eventfd != NULL)
 539                eventfd_ctx_put(req->ki_eventfd);
 540        if (req->ki_dtor)
 541                req->ki_dtor(req);
 542        if (req->ki_iovec != &req->ki_inline_vec)
 543                kfree(req->ki_iovec);
 544        kmem_cache_free(kiocb_cachep, req);
 545}
 546
 547void aio_put_req(struct kiocb *req)
 548{
 549        if (atomic_dec_and_test(&req->ki_users))
 550                kiocb_free(req);
 551}
 552EXPORT_SYMBOL(aio_put_req);
 553
 554static struct kioctx *lookup_ioctx(unsigned long ctx_id)
 555{
 556        struct mm_struct *mm = current->mm;
 557        struct kioctx *ctx, *ret = NULL;
 558
 559        rcu_read_lock();
 560
 561        hlist_for_each_entry_rcu(ctx, &mm->ioctx_list, list) {
 562                if (ctx->user_id == ctx_id) {
 563                        atomic_inc(&ctx->users);
 564                        ret = ctx;
 565                        break;
 566                }
 567        }
 568
 569        rcu_read_unlock();
 570        return ret;
 571}
 572
 573/* aio_complete
 574 *      Called when the io request on the given iocb is complete.
 575 */
 576void aio_complete(struct kiocb *iocb, long res, long res2)
 577{
 578        struct kioctx   *ctx = iocb->ki_ctx;
 579        struct aio_ring *ring;
 580        struct io_event *ev_page, *event;
 581        unsigned long   flags;
 582        unsigned tail, pos;
 583
 584        /*
 585         * Special case handling for sync iocbs:
 586         *  - events go directly into the iocb for fast handling
 587         *  - the sync task with the iocb in its stack holds the single iocb
 588         *    ref, no other paths have a way to get another ref
 589         *  - the sync task helpfully left a reference to itself in the iocb
 590         */
 591        if (is_sync_kiocb(iocb)) {
 592                BUG_ON(atomic_read(&iocb->ki_users) != 1);
 593                iocb->ki_user_data = res;
 594                atomic_set(&iocb->ki_users, 0);
 595                wake_up_process(iocb->ki_obj.tsk);
 596                return;
 597        }
 598
 599        /*
 600         * Take rcu_read_lock() in case the kioctx is being destroyed, as we
 601         * need to issue a wakeup after decrementing reqs_active.
 602         */
 603        rcu_read_lock();
 604
 605        if (iocb->ki_list.next) {
 606                unsigned long flags;
 607
 608                spin_lock_irqsave(&ctx->ctx_lock, flags);
 609                list_del(&iocb->ki_list);
 610                spin_unlock_irqrestore(&ctx->ctx_lock, flags);
 611        }
 612
 613        /*
 614         * cancelled requests don't get events, userland was given one
 615         * when the event got cancelled.
 616         */
 617        if (unlikely(xchg(&iocb->ki_cancel,
 618                          KIOCB_CANCELLED) == KIOCB_CANCELLED)) {
 619                atomic_dec(&ctx->reqs_active);
 620                /* Still need the wake_up in case free_ioctx is waiting */
 621                goto put_rq;
 622        }
 623
 624        /*
 625         * Add a completion event to the ring buffer. Must be done holding
 626         * ctx->ctx_lock to prevent other code from messing with the tail
 627         * pointer since we might be called from irq context.
 628         */
 629        spin_lock_irqsave(&ctx->completion_lock, flags);
 630
 631        tail = ctx->tail;
 632        pos = tail + AIO_EVENTS_OFFSET;
 633
 634        if (++tail >= ctx->nr_events)
 635                tail = 0;
 636
 637        ev_page = kmap_atomic(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
 638        event = ev_page + pos % AIO_EVENTS_PER_PAGE;
 639
 640        event->obj = (u64)(unsigned long)iocb->ki_obj.user;
 641        event->data = iocb->ki_user_data;
 642        event->res = res;
 643        event->res2 = res2;
 644
 645        kunmap_atomic(ev_page);
 646        flush_dcache_page(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
 647
 648        pr_debug("%p[%u]: %p: %p %Lx %lx %lx\n",
 649                 ctx, tail, iocb, iocb->ki_obj.user, iocb->ki_user_data,
 650                 res, res2);
 651
 652        /* after flagging the request as done, we
 653         * must never even look at it again
 654         */
 655        smp_wmb();      /* make event visible before updating tail */
 656
 657        ctx->tail = tail;
 658
 659        ring = kmap_atomic(ctx->ring_pages[0]);
 660        ring->tail = tail;
 661        kunmap_atomic(ring);
 662        flush_dcache_page(ctx->ring_pages[0]);
 663
 664        spin_unlock_irqrestore(&ctx->completion_lock, flags);
 665
 666        pr_debug("added to ring %p at [%u]\n", iocb, tail);
 667
 668        /*
 669         * Check if the user asked us to deliver the result through an
 670         * eventfd. The eventfd_signal() function is safe to be called
 671         * from IRQ context.
 672         */
 673        if (iocb->ki_eventfd != NULL)
 674                eventfd_signal(iocb->ki_eventfd, 1);
 675
 676put_rq:
 677        /* everything turned out well, dispose of the aiocb. */
 678        aio_put_req(iocb);
 679
 680        /*
 681         * We have to order our ring_info tail store above and test
 682         * of the wait list below outside the wait lock.  This is
 683         * like in wake_up_bit() where clearing a bit has to be
 684         * ordered with the unlocked test.
 685         */
 686        smp_mb();
 687
 688        if (waitqueue_active(&ctx->wait))
 689                wake_up(&ctx->wait);
 690
 691        rcu_read_unlock();
 692}
 693EXPORT_SYMBOL(aio_complete);
 694
 695/* aio_read_events
 696 *      Pull an event off of the ioctx's event ring.  Returns the number of
 697 *      events fetched
 698 */
 699static long aio_read_events_ring(struct kioctx *ctx,
 700                                 struct io_event __user *event, long nr)
 701{
 702        struct aio_ring *ring;
 703        unsigned head, pos;
 704        long ret = 0;
 705        int copy_ret;
 706
 707        mutex_lock(&ctx->ring_lock);
 708
 709        ring = kmap_atomic(ctx->ring_pages[0]);
 710        head = ring->head;
 711        kunmap_atomic(ring);
 712
 713        pr_debug("h%u t%u m%u\n", head, ctx->tail, ctx->nr_events);
 714
 715        if (head == ctx->tail)
 716                goto out;
 717
 718        while (ret < nr) {
 719                long avail;
 720                struct io_event *ev;
 721                struct page *page;
 722
 723                avail = (head <= ctx->tail ? ctx->tail : ctx->nr_events) - head;
 724                if (head == ctx->tail)
 725                        break;
 726
 727                avail = min(avail, nr - ret);
 728                avail = min_t(long, avail, AIO_EVENTS_PER_PAGE -
 729                            ((head + AIO_EVENTS_OFFSET) % AIO_EVENTS_PER_PAGE));
 730
 731                pos = head + AIO_EVENTS_OFFSET;
 732                page = ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE];
 733                pos %= AIO_EVENTS_PER_PAGE;
 734
 735                ev = kmap(page);
 736                copy_ret = copy_to_user(event + ret, ev + pos,
 737                                        sizeof(*ev) * avail);
 738                kunmap(page);
 739
 740                if (unlikely(copy_ret)) {
 741                        ret = -EFAULT;
 742                        goto out;
 743                }
 744
 745                ret += avail;
 746                head += avail;
 747                head %= ctx->nr_events;
 748        }
 749
 750        ring = kmap_atomic(ctx->ring_pages[0]);
 751        ring->head = head;
 752        kunmap_atomic(ring);
 753        flush_dcache_page(ctx->ring_pages[0]);
 754
 755        pr_debug("%li  h%u t%u\n", ret, head, ctx->tail);
 756
 757        atomic_sub(ret, &ctx->reqs_active);
 758out:
 759        mutex_unlock(&ctx->ring_lock);
 760
 761        return ret;
 762}
 763
 764static bool aio_read_events(struct kioctx *ctx, long min_nr, long nr,
 765                            struct io_event __user *event, long *i)
 766{
 767        long ret = aio_read_events_ring(ctx, event + *i, nr - *i);
 768
 769        if (ret > 0)
 770                *i += ret;
 771
 772        if (unlikely(atomic_read(&ctx->dead)))
 773                ret = -EINVAL;
 774
 775        if (!*i)
 776                *i = ret;
 777
 778        return ret < 0 || *i >= min_nr;
 779}
 780
 781static long read_events(struct kioctx *ctx, long min_nr, long nr,
 782                        struct io_event __user *event,
 783                        struct timespec __user *timeout)
 784{
 785        ktime_t until = { .tv64 = KTIME_MAX };
 786        long ret = 0;
 787
 788        if (timeout) {
 789                struct timespec ts;
 790
 791                if (unlikely(copy_from_user(&ts, timeout, sizeof(ts))))
 792                        return -EFAULT;
 793
 794                until = timespec_to_ktime(ts);
 795        }
 796
 797        /*
 798         * Note that aio_read_events() is being called as the conditional - i.e.
 799         * we're calling it after prepare_to_wait() has set task state to
 800         * TASK_INTERRUPTIBLE.
 801         *
 802         * But aio_read_events() can block, and if it blocks it's going to flip
 803         * the task state back to TASK_RUNNING.
 804         *
 805         * This should be ok, provided it doesn't flip the state back to
 806         * TASK_RUNNING and return 0 too much - that causes us to spin. That
 807         * will only happen if the mutex_lock() call blocks, and we then find
 808         * the ringbuffer empty. So in practice we should be ok, but it's
 809         * something to be aware of when touching this code.
 810         */
 811        wait_event_interruptible_hrtimeout(ctx->wait,
 812                        aio_read_events(ctx, min_nr, nr, event, &ret), until);
 813
 814        if (!ret && signal_pending(current))
 815                ret = -EINTR;
 816
 817        return ret;
 818}
 819
 820/* sys_io_setup:
 821 *      Create an aio_context capable of receiving at least nr_events.
 822 *      ctxp must not point to an aio_context that already exists, and
 823 *      must be initialized to 0 prior to the call.  On successful
 824 *      creation of the aio_context, *ctxp is filled in with the resulting 
 825 *      handle.  May fail with -EINVAL if *ctxp is not initialized,
 826 *      if the specified nr_events exceeds internal limits.  May fail 
 827 *      with -EAGAIN if the specified nr_events exceeds the user's limit 
 828 *      of available events.  May fail with -ENOMEM if insufficient kernel
 829 *      resources are available.  May fail with -EFAULT if an invalid
 830 *      pointer is passed for ctxp.  Will fail with -ENOSYS if not
 831 *      implemented.
 832 */
 833SYSCALL_DEFINE2(io_setup, unsigned, nr_events, aio_context_t __user *, ctxp)
 834{
 835        struct kioctx *ioctx = NULL;
 836        unsigned long ctx;
 837        long ret;
 838
 839        ret = get_user(ctx, ctxp);
 840        if (unlikely(ret))
 841                goto out;
 842
 843        ret = -EINVAL;
 844        if (unlikely(ctx || nr_events == 0)) {
 845                pr_debug("EINVAL: io_setup: ctx %lu nr_events %u\n",
 846                         ctx, nr_events);
 847                goto out;
 848        }
 849
 850        ioctx = ioctx_alloc(nr_events);
 851        ret = PTR_ERR(ioctx);
 852        if (!IS_ERR(ioctx)) {
 853                ret = put_user(ioctx->user_id, ctxp);
 854                if (ret)
 855                        kill_ioctx(ioctx);
 856                put_ioctx(ioctx);
 857        }
 858
 859out:
 860        return ret;
 861}
 862
 863/* sys_io_destroy:
 864 *      Destroy the aio_context specified.  May cancel any outstanding 
 865 *      AIOs and block on completion.  Will fail with -ENOSYS if not
 866 *      implemented.  May fail with -EINVAL if the context pointed to
 867 *      is invalid.
 868 */
 869SYSCALL_DEFINE1(io_destroy, aio_context_t, ctx)
 870{
 871        struct kioctx *ioctx = lookup_ioctx(ctx);
 872        if (likely(NULL != ioctx)) {
 873                kill_ioctx(ioctx);
 874                put_ioctx(ioctx);
 875                return 0;
 876        }
 877        pr_debug("EINVAL: io_destroy: invalid context id\n");
 878        return -EINVAL;
 879}
 880
 881static void aio_advance_iovec(struct kiocb *iocb, ssize_t ret)
 882{
 883        struct iovec *iov = &iocb->ki_iovec[iocb->ki_cur_seg];
 884
 885        BUG_ON(ret <= 0);
 886
 887        while (iocb->ki_cur_seg < iocb->ki_nr_segs && ret > 0) {
 888                ssize_t this = min((ssize_t)iov->iov_len, ret);
 889                iov->iov_base += this;
 890                iov->iov_len -= this;
 891                iocb->ki_left -= this;
 892                ret -= this;
 893                if (iov->iov_len == 0) {
 894                        iocb->ki_cur_seg++;
 895                        iov++;
 896                }
 897        }
 898
 899        /* the caller should not have done more io than what fit in
 900         * the remaining iovecs */
 901        BUG_ON(ret > 0 && iocb->ki_left == 0);
 902}
 903
 904typedef ssize_t (aio_rw_op)(struct kiocb *, const struct iovec *,
 905                            unsigned long, loff_t);
 906
 907static ssize_t aio_rw_vect_retry(struct kiocb *iocb, int rw, aio_rw_op *rw_op)
 908{
 909        struct file *file = iocb->ki_filp;
 910        struct address_space *mapping = file->f_mapping;
 911        struct inode *inode = mapping->host;
 912        ssize_t ret = 0;
 913
 914        /* This matches the pread()/pwrite() logic */
 915        if (iocb->ki_pos < 0)
 916                return -EINVAL;
 917
 918        if (rw == WRITE)
 919                file_start_write(file);
 920        do {
 921                ret = rw_op(iocb, &iocb->ki_iovec[iocb->ki_cur_seg],
 922                            iocb->ki_nr_segs - iocb->ki_cur_seg,
 923                            iocb->ki_pos);
 924                if (ret > 0)
 925                        aio_advance_iovec(iocb, ret);
 926
 927        /* retry all partial writes.  retry partial reads as long as its a
 928         * regular file. */
 929        } while (ret > 0 && iocb->ki_left > 0 &&
 930                 (rw == WRITE ||
 931                  (!S_ISFIFO(inode->i_mode) && !S_ISSOCK(inode->i_mode))));
 932        if (rw == WRITE)
 933                file_end_write(file);
 934
 935        /* This means we must have transferred all that we could */
 936        /* No need to retry anymore */
 937        if ((ret == 0) || (iocb->ki_left == 0))
 938                ret = iocb->ki_nbytes - iocb->ki_left;
 939
 940        /* If we managed to write some out we return that, rather than
 941         * the eventual error. */
 942        if (rw == WRITE
 943            && ret < 0 && ret != -EIOCBQUEUED
 944            && iocb->ki_nbytes - iocb->ki_left)
 945                ret = iocb->ki_nbytes - iocb->ki_left;
 946
 947        return ret;
 948}
 949
 950static ssize_t aio_setup_vectored_rw(int rw, struct kiocb *kiocb, bool compat)
 951{
 952        ssize_t ret;
 953
 954        kiocb->ki_nr_segs = kiocb->ki_nbytes;
 955
 956#ifdef CONFIG_COMPAT
 957        if (compat)
 958                ret = compat_rw_copy_check_uvector(rw,
 959                                (struct compat_iovec __user *)kiocb->ki_buf,
 960                                kiocb->ki_nr_segs, 1, &kiocb->ki_inline_vec,
 961                                &kiocb->ki_iovec);
 962        else
 963#endif
 964                ret = rw_copy_check_uvector(rw,
 965                                (struct iovec __user *)kiocb->ki_buf,
 966                                kiocb->ki_nr_segs, 1, &kiocb->ki_inline_vec,
 967                                &kiocb->ki_iovec);
 968        if (ret < 0)
 969                return ret;
 970
 971        /* ki_nbytes now reflect bytes instead of segs */
 972        kiocb->ki_nbytes = ret;
 973        return 0;
 974}
 975
 976static ssize_t aio_setup_single_vector(int rw, struct kiocb *kiocb)
 977{
 978        if (unlikely(!access_ok(!rw, kiocb->ki_buf, kiocb->ki_nbytes)))
 979                return -EFAULT;
 980
 981        kiocb->ki_iovec = &kiocb->ki_inline_vec;
 982        kiocb->ki_iovec->iov_base = kiocb->ki_buf;
 983        kiocb->ki_iovec->iov_len = kiocb->ki_nbytes;
 984        kiocb->ki_nr_segs = 1;
 985        return 0;
 986}
 987
 988/*
 989 * aio_setup_iocb:
 990 *      Performs the initial checks and aio retry method
 991 *      setup for the kiocb at the time of io submission.
 992 */
 993static ssize_t aio_run_iocb(struct kiocb *req, bool compat)
 994{
 995        struct file *file = req->ki_filp;
 996        ssize_t ret;
 997        int rw;
 998        fmode_t mode;
 999        aio_rw_op *rw_op;
1000
1001        switch (req->ki_opcode) {
1002        case IOCB_CMD_PREAD:
1003        case IOCB_CMD_PREADV:
1004                mode    = FMODE_READ;
1005                rw      = READ;
1006                rw_op   = file->f_op->aio_read;
1007                goto rw_common;
1008
1009        case IOCB_CMD_PWRITE:
1010        case IOCB_CMD_PWRITEV:
1011                mode    = FMODE_WRITE;
1012                rw      = WRITE;
1013                rw_op   = file->f_op->aio_write;
1014                goto rw_common;
1015rw_common:
1016                if (unlikely(!(file->f_mode & mode)))
1017                        return -EBADF;
1018
1019                if (!rw_op)
1020                        return -EINVAL;
1021
1022                ret = (req->ki_opcode == IOCB_CMD_PREADV ||
1023                       req->ki_opcode == IOCB_CMD_PWRITEV)
1024                        ? aio_setup_vectored_rw(rw, req, compat)
1025                        : aio_setup_single_vector(rw, req);
1026                if (ret)
1027                        return ret;
1028
1029                ret = rw_verify_area(rw, file, &req->ki_pos, req->ki_nbytes);
1030                if (ret < 0)
1031                        return ret;
1032
1033                req->ki_nbytes = ret;
1034                req->ki_left = ret;
1035
1036                ret = aio_rw_vect_retry(req, rw, rw_op);
1037                break;
1038
1039        case IOCB_CMD_FDSYNC:
1040                if (!file->f_op->aio_fsync)
1041                        return -EINVAL;
1042
1043                ret = file->f_op->aio_fsync(req, 1);
1044                break;
1045
1046        case IOCB_CMD_FSYNC:
1047                if (!file->f_op->aio_fsync)
1048                        return -EINVAL;
1049
1050                ret = file->f_op->aio_fsync(req, 0);
1051                break;
1052
1053        default:
1054                pr_debug("EINVAL: no operation provided\n");
1055                return -EINVAL;
1056        }
1057
1058        if (ret != -EIOCBQUEUED) {
1059                /*
1060                 * There's no easy way to restart the syscall since other AIO's
1061                 * may be already running. Just fail this IO with EINTR.
1062                 */
1063                if (unlikely(ret == -ERESTARTSYS || ret == -ERESTARTNOINTR ||
1064                             ret == -ERESTARTNOHAND ||
1065                             ret == -ERESTART_RESTARTBLOCK))
1066                        ret = -EINTR;
1067                aio_complete(req, ret, 0);
1068        }
1069
1070        return 0;
1071}
1072
1073static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
1074                         struct iocb *iocb, bool compat)
1075{
1076        struct kiocb *req;
1077        ssize_t ret;
1078
1079        /* enforce forwards compatibility on users */
1080        if (unlikely(iocb->aio_reserved1 || iocb->aio_reserved2)) {
1081                pr_debug("EINVAL: reserve field set\n");
1082                return -EINVAL;
1083        }
1084
1085        /* prevent overflows */
1086        if (unlikely(
1087            (iocb->aio_buf != (unsigned long)iocb->aio_buf) ||
1088            (iocb->aio_nbytes != (size_t)iocb->aio_nbytes) ||
1089            ((ssize_t)iocb->aio_nbytes < 0)
1090           )) {
1091                pr_debug("EINVAL: io_submit: overflow check\n");
1092                return -EINVAL;
1093        }
1094
1095        req = aio_get_req(ctx);
1096        if (unlikely(!req))
1097                return -EAGAIN;
1098
1099        req->ki_filp = fget(iocb->aio_fildes);
1100        if (unlikely(!req->ki_filp)) {
1101                ret = -EBADF;
1102                goto out_put_req;
1103        }
1104
1105        if (iocb->aio_flags & IOCB_FLAG_RESFD) {
1106                /*
1107                 * If the IOCB_FLAG_RESFD flag of aio_flags is set, get an
1108                 * instance of the file* now. The file descriptor must be
1109                 * an eventfd() fd, and will be signaled for each completed
1110                 * event using the eventfd_signal() function.
1111                 */
1112                req->ki_eventfd = eventfd_ctx_fdget((int) iocb->aio_resfd);
1113                if (IS_ERR(req->ki_eventfd)) {
1114                        ret = PTR_ERR(req->ki_eventfd);
1115                        req->ki_eventfd = NULL;
1116                        goto out_put_req;
1117                }
1118        }
1119
1120        ret = put_user(KIOCB_KEY, &user_iocb->aio_key);
1121        if (unlikely(ret)) {
1122                pr_debug("EFAULT: aio_key\n");
1123                goto out_put_req;
1124        }
1125
1126        req->ki_obj.user = user_iocb;
1127        req->ki_user_data = iocb->aio_data;
1128        req->ki_pos = iocb->aio_offset;
1129
1130        req->ki_buf = (char __user *)(unsigned long)iocb->aio_buf;
1131        req->ki_left = req->ki_nbytes = iocb->aio_nbytes;
1132        req->ki_opcode = iocb->aio_lio_opcode;
1133
1134        ret = aio_run_iocb(req, compat);
1135        if (ret)
1136                goto out_put_req;
1137
1138        aio_put_req(req);       /* drop extra ref to req */
1139        return 0;
1140out_put_req:
1141        atomic_dec(&ctx->reqs_active);
1142        aio_put_req(req);       /* drop extra ref to req */
1143        aio_put_req(req);       /* drop i/o ref to req */
1144        return ret;
1145}
1146
1147long do_io_submit(aio_context_t ctx_id, long nr,
1148                  struct iocb __user *__user *iocbpp, bool compat)
1149{
1150        struct kioctx *ctx;
1151        long ret = 0;
1152        int i = 0;
1153        struct blk_plug plug;
1154
1155        if (unlikely(nr < 0))
1156                return -EINVAL;
1157
1158        if (unlikely(nr > LONG_MAX/sizeof(*iocbpp)))
1159                nr = LONG_MAX/sizeof(*iocbpp);
1160
1161        if (unlikely(!access_ok(VERIFY_READ, iocbpp, (nr*sizeof(*iocbpp)))))
1162                return -EFAULT;
1163
1164        ctx = lookup_ioctx(ctx_id);
1165        if (unlikely(!ctx)) {
1166                pr_debug("EINVAL: invalid context id\n");
1167                return -EINVAL;
1168        }
1169
1170        blk_start_plug(&plug);
1171
1172        /*
1173         * AKPM: should this return a partial result if some of the IOs were
1174         * successfully submitted?
1175         */
1176        for (i=0; i<nr; i++) {
1177                struct iocb __user *user_iocb;
1178                struct iocb tmp;
1179
1180                if (unlikely(__get_user(user_iocb, iocbpp + i))) {
1181                        ret = -EFAULT;
1182                        break;
1183                }
1184
1185                if (unlikely(copy_from_user(&tmp, user_iocb, sizeof(tmp)))) {
1186                        ret = -EFAULT;
1187                        break;
1188                }
1189
1190                ret = io_submit_one(ctx, user_iocb, &tmp, compat);
1191                if (ret)
1192                        break;
1193        }
1194        blk_finish_plug(&plug);
1195
1196        put_ioctx(ctx);
1197        return i ? i : ret;
1198}
1199
1200/* sys_io_submit:
1201 *      Queue the nr iocbs pointed to by iocbpp for processing.  Returns
1202 *      the number of iocbs queued.  May return -EINVAL if the aio_context
1203 *      specified by ctx_id is invalid, if nr is < 0, if the iocb at
1204 *      *iocbpp[0] is not properly initialized, if the operation specified
1205 *      is invalid for the file descriptor in the iocb.  May fail with
1206 *      -EFAULT if any of the data structures point to invalid data.  May
1207 *      fail with -EBADF if the file descriptor specified in the first
1208 *      iocb is invalid.  May fail with -EAGAIN if insufficient resources
1209 *      are available to queue any iocbs.  Will return 0 if nr is 0.  Will
1210 *      fail with -ENOSYS if not implemented.
1211 */
1212SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
1213                struct iocb __user * __user *, iocbpp)
1214{
1215        return do_io_submit(ctx_id, nr, iocbpp, 0);
1216}
1217
1218/* lookup_kiocb
1219 *      Finds a given iocb for cancellation.
1220 */
1221static struct kiocb *lookup_kiocb(struct kioctx *ctx, struct iocb __user *iocb,
1222                                  u32 key)
1223{
1224        struct list_head *pos;
1225
1226        assert_spin_locked(&ctx->ctx_lock);
1227
1228        if (key != KIOCB_KEY)
1229                return NULL;
1230
1231        /* TODO: use a hash or array, this sucks. */
1232        list_for_each(pos, &ctx->active_reqs) {
1233                struct kiocb *kiocb = list_kiocb(pos);
1234                if (kiocb->ki_obj.user == iocb)
1235                        return kiocb;
1236        }
1237        return NULL;
1238}
1239
1240/* sys_io_cancel:
1241 *      Attempts to cancel an iocb previously passed to io_submit.  If
1242 *      the operation is successfully cancelled, the resulting event is
1243 *      copied into the memory pointed to by result without being placed
1244 *      into the completion queue and 0 is returned.  May fail with
1245 *      -EFAULT if any of the data structures pointed to are invalid.
1246 *      May fail with -EINVAL if aio_context specified by ctx_id is
1247 *      invalid.  May fail with -EAGAIN if the iocb specified was not
1248 *      cancelled.  Will fail with -ENOSYS if not implemented.
1249 */
1250SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
1251                struct io_event __user *, result)
1252{
1253        struct io_event res;
1254        struct kioctx *ctx;
1255        struct kiocb *kiocb;
1256        u32 key;
1257        int ret;
1258
1259        ret = get_user(key, &iocb->aio_key);
1260        if (unlikely(ret))
1261                return -EFAULT;
1262
1263        ctx = lookup_ioctx(ctx_id);
1264        if (unlikely(!ctx))
1265                return -EINVAL;
1266
1267        spin_lock_irq(&ctx->ctx_lock);
1268
1269        kiocb = lookup_kiocb(ctx, iocb, key);
1270        if (kiocb)
1271                ret = kiocb_cancel(ctx, kiocb, &res);
1272        else
1273                ret = -EINVAL;
1274
1275        spin_unlock_irq(&ctx->ctx_lock);
1276
1277        if (!ret) {
1278                /* Cancellation succeeded -- copy the result
1279                 * into the user's buffer.
1280                 */
1281                if (copy_to_user(result, &res, sizeof(res)))
1282                        ret = -EFAULT;
1283        }
1284
1285        put_ioctx(ctx);
1286
1287        return ret;
1288}
1289
1290/* io_getevents:
1291 *      Attempts to read at least min_nr events and up to nr events from
1292 *      the completion queue for the aio_context specified by ctx_id. If
1293 *      it succeeds, the number of read events is returned. May fail with
1294 *      -EINVAL if ctx_id is invalid, if min_nr is out of range, if nr is
1295 *      out of range, if timeout is out of range.  May fail with -EFAULT
1296 *      if any of the memory specified is invalid.  May return 0 or
1297 *      < min_nr if the timeout specified by timeout has elapsed
1298 *      before sufficient events are available, where timeout == NULL
1299 *      specifies an infinite timeout. Note that the timeout pointed to by
1300 *      timeout is relative.  Will fail with -ENOSYS if not implemented.
1301 */
1302SYSCALL_DEFINE5(io_getevents, aio_context_t, ctx_id,
1303                long, min_nr,
1304                long, nr,
1305                struct io_event __user *, events,
1306                struct timespec __user *, timeout)
1307{
1308        struct kioctx *ioctx = lookup_ioctx(ctx_id);
1309        long ret = -EINVAL;
1310
1311        if (likely(ioctx)) {
1312                if (likely(min_nr <= nr && min_nr >= 0))
1313                        ret = read_events(ioctx, min_nr, nr, events, timeout);
1314                put_ioctx(ioctx);
1315        }
1316        return ret;
1317}
1318
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