FreeBSD/Linux Kernel Cross Reference
sys/fs/aio.c

     /*
      *      An async IO implementation for Linux
      *      Written by Benjamin LaHaise <bcrl@kvack.org>
      *
      *      Implements an efficient asynchronous io interface.
      *
      *      Copyright 2000, 2001, 2002 Red Hat, Inc.  All Rights Reserved.
      *
      *      See ../COPYING for licensing terms.
     */
    #include <linux/kernel.h>
    #include <linux/init.h>
    #include <linux/errno.h>
    #include <linux/time.h>
    #include <linux/aio_abi.h>
    #include <linux/export.h>
    #include <linux/syscalls.h>
    #include <linux/backing-dev.h>
    #include <linux/uio.h>
    
    #define DEBUG 0
    
    #include <linux/sched.h>
    #include <linux/fs.h>
    #include <linux/file.h>
    #include <linux/mm.h>
    #include <linux/mman.h>
    #include <linux/mmu_context.h>
    #include <linux/slab.h>
    #include <linux/timer.h>
    #include <linux/aio.h>
    #include <linux/highmem.h>
    #include <linux/workqueue.h>
    #include <linux/security.h>
    #include <linux/eventfd.h>
    #include <linux/blkdev.h>
    #include <linux/compat.h>
    
    #include <asm/kmap_types.h>
    #include <asm/uaccess.h>
    
    #if DEBUG > 1
    #define dprintk         printk
    #else
    #define dprintk(x...)   do { ; } while (0)
    #endif
    
    /*------ sysctl variables----*/
    static DEFINE_SPINLOCK(aio_nr_lock);
    unsigned long aio_nr;           /* current system wide number of aio requests */
    unsigned long aio_max_nr = 0x10000; /* system wide maximum number of aio requests */
    /*----end sysctl variables---*/
    
    static struct kmem_cache        *kiocb_cachep;
    static struct kmem_cache        *kioctx_cachep;
    
    static struct workqueue_struct *aio_wq;
    
    static void aio_kick_handler(struct work_struct *);
    static void aio_queue_work(struct kioctx *);
    
    /* aio_setup
     *      Creates the slab caches used by the aio routines, panic on
     *      failure as this is done early during the boot sequence.
     */
    static int __init aio_setup(void)
    {
            kiocb_cachep = KMEM_CACHE(kiocb, SLAB_HWCACHE_ALIGN|SLAB_PANIC);
            kioctx_cachep = KMEM_CACHE(kioctx,SLAB_HWCACHE_ALIGN|SLAB_PANIC);
    
            aio_wq = alloc_workqueue("aio", 0, 1);  /* used to limit concurrency */
            BUG_ON(!aio_wq);
    
            pr_debug("aio_setup: sizeof(struct page) = %d\n", (int)sizeof(struct page));
    
            return 0;
    }
    __initcall(aio_setup);
    
    static void aio_free_ring(struct kioctx *ctx)
    {
            struct aio_ring_info *info = &ctx->ring_info;
            long i;
    
            for (i=0; i<info->nr_pages; i++)
                    put_page(info->ring_pages[i]);
    
            if (info->mmap_size) {
                    BUG_ON(ctx->mm != current->mm);
                    vm_munmap(info->mmap_base, info->mmap_size);
            }
    
            if (info->ring_pages && info->ring_pages != info->internal_pages)
                    kfree(info->ring_pages);
            info->ring_pages = NULL;
            info->nr = 0;
    }
    
    static int aio_setup_ring(struct kioctx *ctx)
   {
           struct aio_ring *ring;
           struct aio_ring_info *info = &ctx->ring_info;
           unsigned nr_events = ctx->max_reqs;
           unsigned long size;
           int nr_pages;
   
           /* Compensate for the ring buffer's head/tail overlap entry */
           nr_events += 2; /* 1 is required, 2 for good luck */
   
           size = sizeof(struct aio_ring);
           size += sizeof(struct io_event) * nr_events;
           nr_pages = (size + PAGE_SIZE-1) >> PAGE_SHIFT;
   
           if (nr_pages < 0)
                   return -EINVAL;
   
           nr_events = (PAGE_SIZE * nr_pages - sizeof(struct aio_ring)) / sizeof(struct io_event);
   
           info->nr = 0;
           info->ring_pages = info->internal_pages;
           if (nr_pages > AIO_RING_PAGES) {
                   info->ring_pages = kcalloc(nr_pages, sizeof(struct page *), GFP_KERNEL);
                   if (!info->ring_pages)
                           return -ENOMEM;
           }
   
           info->mmap_size = nr_pages * PAGE_SIZE;
           dprintk("attempting mmap of %lu bytes\n", info->mmap_size);
           down_write(&ctx->mm->mmap_sem);
           info->mmap_base = do_mmap_pgoff(NULL, 0, info->mmap_size, 
                                           PROT_READ|PROT_WRITE,
                                           MAP_ANONYMOUS|MAP_PRIVATE, 0);
           if (IS_ERR((void *)info->mmap_base)) {
                   up_write(&ctx->mm->mmap_sem);
                   info->mmap_size = 0;
                   aio_free_ring(ctx);
                   return -EAGAIN;
           }
   
           dprintk("mmap address: 0x%08lx\n", info->mmap_base);
           info->nr_pages = get_user_pages(current, ctx->mm,
                                           info->mmap_base, nr_pages, 
                                           1, 0, info->ring_pages, NULL);
           up_write(&ctx->mm->mmap_sem);
   
           if (unlikely(info->nr_pages != nr_pages)) {
                   aio_free_ring(ctx);
                   return -EAGAIN;
           }
   
           ctx->user_id = info->mmap_base;
   
           info->nr = nr_events;           /* trusted copy */
   
           ring = kmap_atomic(info->ring_pages[0]);
           ring->nr = nr_events;   /* user copy */
           ring->id = ctx->user_id;
           ring->head = ring->tail = 0;
           ring->magic = AIO_RING_MAGIC;
           ring->compat_features = AIO_RING_COMPAT_FEATURES;
           ring->incompat_features = AIO_RING_INCOMPAT_FEATURES;
           ring->header_length = sizeof(struct aio_ring);
           kunmap_atomic(ring);
   
           return 0;
   }
   
   
   /* aio_ring_event: returns a pointer to the event at the given index from
    * kmap_atomic().  Release the pointer with put_aio_ring_event();
    */
   #define AIO_EVENTS_PER_PAGE     (PAGE_SIZE / sizeof(struct io_event))
   #define AIO_EVENTS_FIRST_PAGE   ((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event))
   #define AIO_EVENTS_OFFSET       (AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE)
   
   #define aio_ring_event(info, nr) ({                                     \
           unsigned pos = (nr) + AIO_EVENTS_OFFSET;                        \
           struct io_event *__event;                                       \
           __event = kmap_atomic(                                          \
                           (info)->ring_pages[pos / AIO_EVENTS_PER_PAGE]); \
           __event += pos % AIO_EVENTS_PER_PAGE;                           \
           __event;                                                        \
   })
   
   #define put_aio_ring_event(event) do {          \
           struct io_event *__event = (event);     \
           (void)__event;                          \
           kunmap_atomic((void *)((unsigned long)__event & PAGE_MASK)); \
   } while(0)
   
   static void ctx_rcu_free(struct rcu_head *head)
   {
           struct kioctx *ctx = container_of(head, struct kioctx, rcu_head);
           kmem_cache_free(kioctx_cachep, ctx);
   }
   
   /* __put_ioctx
    *      Called when the last user of an aio context has gone away,
    *      and the struct needs to be freed.
    */
   static void __put_ioctx(struct kioctx *ctx)
   {
           unsigned nr_events = ctx->max_reqs;
           BUG_ON(ctx->reqs_active);
   
           cancel_delayed_work_sync(&ctx->wq);
           aio_free_ring(ctx);
           mmdrop(ctx->mm);
           ctx->mm = NULL;
           if (nr_events) {
                   spin_lock(&aio_nr_lock);
                   BUG_ON(aio_nr - nr_events > aio_nr);
                   aio_nr -= nr_events;
                   spin_unlock(&aio_nr_lock);
           }
           pr_debug("__put_ioctx: freeing %p\n", ctx);
           call_rcu(&ctx->rcu_head, ctx_rcu_free);
   }
   
   static inline int try_get_ioctx(struct kioctx *kioctx)
   {
           return atomic_inc_not_zero(&kioctx->users);
   }
   
   static inline void put_ioctx(struct kioctx *kioctx)
   {
           BUG_ON(atomic_read(&kioctx->users) <= 0);
           if (unlikely(atomic_dec_and_test(&kioctx->users)))
                   __put_ioctx(kioctx);
   }
   
   /* ioctx_alloc
    *      Allocates and initializes an ioctx.  Returns an ERR_PTR if it failed.
    */
   static struct kioctx *ioctx_alloc(unsigned nr_events)
   {
           struct mm_struct *mm;
           struct kioctx *ctx;
           int err = -ENOMEM;
   
           /* Prevent overflows */
           if ((nr_events > (0x10000000U / sizeof(struct io_event))) ||
               (nr_events > (0x10000000U / sizeof(struct kiocb)))) {
                   pr_debug("ENOMEM: nr_events too high\n");
                   return ERR_PTR(-EINVAL);
           }
   
           if (!nr_events || (unsigned long)nr_events > aio_max_nr)
                   return ERR_PTR(-EAGAIN);
   
           ctx = kmem_cache_zalloc(kioctx_cachep, GFP_KERNEL);
           if (!ctx)
                   return ERR_PTR(-ENOMEM);
   
           ctx->max_reqs = nr_events;
           mm = ctx->mm = current->mm;
           atomic_inc(&mm->mm_count);
   
           atomic_set(&ctx->users, 2);
           spin_lock_init(&ctx->ctx_lock);
           spin_lock_init(&ctx->ring_info.ring_lock);
           init_waitqueue_head(&ctx->wait);
   
           INIT_LIST_HEAD(&ctx->active_reqs);
           INIT_LIST_HEAD(&ctx->run_list);
           INIT_DELAYED_WORK(&ctx->wq, aio_kick_handler);
   
           if (aio_setup_ring(ctx) < 0)
                   goto out_freectx;
   
           /* limit the number of system wide aios */
           spin_lock(&aio_nr_lock);
           if (aio_nr + nr_events > aio_max_nr ||
               aio_nr + nr_events < aio_nr) {
                   spin_unlock(&aio_nr_lock);
                   goto out_cleanup;
           }
           aio_nr += ctx->max_reqs;
           spin_unlock(&aio_nr_lock);
   
           /* now link into global list. */
           spin_lock(&mm->ioctx_lock);
           hlist_add_head_rcu(&ctx->list, &mm->ioctx_list);
           spin_unlock(&mm->ioctx_lock);
   
           dprintk("aio: allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",
                   ctx, ctx->user_id, current->mm, ctx->ring_info.nr);
           return ctx;
   
   out_cleanup:
           err = -EAGAIN;
           aio_free_ring(ctx);
   out_freectx:
           mmdrop(mm);
           kmem_cache_free(kioctx_cachep, ctx);
           dprintk("aio: error allocating ioctx %d\n", err);
           return ERR_PTR(err);
   }
   
   /* kill_ctx
    *      Cancels all outstanding aio requests on an aio context.  Used 
    *      when the processes owning a context have all exited to encourage 
    *      the rapid destruction of the kioctx.
    */
   static void kill_ctx(struct kioctx *ctx)
   {
           int (*cancel)(struct kiocb *, struct io_event *);
           struct task_struct *tsk = current;
           DECLARE_WAITQUEUE(wait, tsk);
           struct io_event res;
   
           spin_lock_irq(&ctx->ctx_lock);
           ctx->dead = 1;
           while (!list_empty(&ctx->active_reqs)) {
                   struct list_head *pos = ctx->active_reqs.next;
                   struct kiocb *iocb = list_kiocb(pos);
                   list_del_init(&iocb->ki_list);
                   cancel = iocb->ki_cancel;
                   kiocbSetCancelled(iocb);
                   if (cancel) {
                           iocb->ki_users++;
                           spin_unlock_irq(&ctx->ctx_lock);
                           cancel(iocb, &res);
                           spin_lock_irq(&ctx->ctx_lock);
                   }
           }
   
           if (!ctx->reqs_active)
                   goto out;
   
           add_wait_queue(&ctx->wait, &wait);
           set_task_state(tsk, TASK_UNINTERRUPTIBLE);
           while (ctx->reqs_active) {
                   spin_unlock_irq(&ctx->ctx_lock);
                   io_schedule();
                   set_task_state(tsk, TASK_UNINTERRUPTIBLE);
                   spin_lock_irq(&ctx->ctx_lock);
           }
           __set_task_state(tsk, TASK_RUNNING);
           remove_wait_queue(&ctx->wait, &wait);
   
   out:
           spin_unlock_irq(&ctx->ctx_lock);
   }
   
   /* wait_on_sync_kiocb:
    *      Waits on the given sync kiocb to complete.
    */
   ssize_t wait_on_sync_kiocb(struct kiocb *iocb)
   {
           while (iocb->ki_users) {
                   set_current_state(TASK_UNINTERRUPTIBLE);
                   if (!iocb->ki_users)
                           break;
                   io_schedule();
           }
           __set_current_state(TASK_RUNNING);
           return iocb->ki_user_data;
   }
   EXPORT_SYMBOL(wait_on_sync_kiocb);
   
   /* exit_aio: called when the last user of mm goes away.  At this point, 
    * there is no way for any new requests to be submited or any of the 
    * io_* syscalls to be called on the context.  However, there may be 
    * outstanding requests which hold references to the context; as they 
    * go away, they will call put_ioctx and release any pinned memory
    * associated with the request (held via struct page * references).
    */
   void exit_aio(struct mm_struct *mm)
   {
           struct kioctx *ctx;
   
           while (!hlist_empty(&mm->ioctx_list)) {
                   ctx = hlist_entry(mm->ioctx_list.first, struct kioctx, list);
                   hlist_del_rcu(&ctx->list);
   
                   kill_ctx(ctx);
   
                   if (1 != atomic_read(&ctx->users))
                           printk(KERN_DEBUG
                                   "exit_aio:ioctx still alive: %d %d %d\n",
                                   atomic_read(&ctx->users), ctx->dead,
                                   ctx->reqs_active);
                   /*
                    * We don't need to bother with munmap() here -
                    * exit_mmap(mm) is coming and it'll unmap everything.
                    * Since aio_free_ring() uses non-zero ->mmap_size
                    * as indicator that it needs to unmap the area,
                    * just set it to 0; aio_free_ring() is the only
                    * place that uses ->mmap_size, so it's safe.
                    * That way we get all munmap done to current->mm -
                    * all other callers have ctx->mm == current->mm.
                    */
                   ctx->ring_info.mmap_size = 0;
                   put_ioctx(ctx);
           }
   }
   
   /* aio_get_req
    *      Allocate a slot for an aio request.  Increments the users count
    * of the kioctx so that the kioctx stays around until all requests are
    * complete.  Returns NULL if no requests are free.
    *
    * Returns with kiocb->users set to 2.  The io submit code path holds
    * an extra reference while submitting the i/o.
    * This prevents races between the aio code path referencing the
    * req (after submitting it) and aio_complete() freeing the req.
    */
   static struct kiocb *__aio_get_req(struct kioctx *ctx)
   {
           struct kiocb *req = NULL;
   
           req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL);
           if (unlikely(!req))
                   return NULL;
   
           req->ki_flags = 0;
           req->ki_users = 2;
           req->ki_key = 0;
           req->ki_ctx = ctx;
           req->ki_cancel = NULL;
           req->ki_retry = NULL;
           req->ki_dtor = NULL;
           req->private = NULL;
           req->ki_iovec = NULL;
           INIT_LIST_HEAD(&req->ki_run_list);
           req->ki_eventfd = NULL;
   
           return req;
   }
   
   /*
    * struct kiocb's are allocated in batches to reduce the number of
    * times the ctx lock is acquired and released.
    */
   #define KIOCB_BATCH_SIZE        32L
   struct kiocb_batch {
           struct list_head head;
           long count; /* number of requests left to allocate */
   };
   
   static void kiocb_batch_init(struct kiocb_batch *batch, long total)
   {
           INIT_LIST_HEAD(&batch->head);
           batch->count = total;
   }
   
   static void kiocb_batch_free(struct kioctx *ctx, struct kiocb_batch *batch)
   {
           struct kiocb *req, *n;
   
           if (list_empty(&batch->head))
                   return;
   
           spin_lock_irq(&ctx->ctx_lock);
           list_for_each_entry_safe(req, n, &batch->head, ki_batch) {
                   list_del(&req->ki_batch);
                   list_del(&req->ki_list);
                   kmem_cache_free(kiocb_cachep, req);
                   ctx->reqs_active--;
           }
           if (unlikely(!ctx->reqs_active && ctx->dead))
                   wake_up_all(&ctx->wait);
           spin_unlock_irq(&ctx->ctx_lock);
   }
   
   /*
    * Allocate a batch of kiocbs.  This avoids taking and dropping the
    * context lock a lot during setup.
    */
   static int kiocb_batch_refill(struct kioctx *ctx, struct kiocb_batch *batch)
   {
           unsigned short allocated, to_alloc;
           long avail;
           struct kiocb *req, *n;
           struct aio_ring *ring;
   
           to_alloc = min(batch->count, KIOCB_BATCH_SIZE);
           for (allocated = 0; allocated < to_alloc; allocated++) {
                   req = __aio_get_req(ctx);
                   if (!req)
                           /* allocation failed, go with what we've got */
                           break;
                   list_add(&req->ki_batch, &batch->head);
           }
   
           if (allocated == 0)
                   goto out;
   
           spin_lock_irq(&ctx->ctx_lock);
           ring = kmap_atomic(ctx->ring_info.ring_pages[0]);
   
           avail = aio_ring_avail(&ctx->ring_info, ring) - ctx->reqs_active;
           BUG_ON(avail < 0);
           if (avail < allocated) {
                   /* Trim back the number of requests. */
                   list_for_each_entry_safe(req, n, &batch->head, ki_batch) {
                           list_del(&req->ki_batch);
                           kmem_cache_free(kiocb_cachep, req);
                           if (--allocated <= avail)
                                   break;
                   }
           }
   
           batch->count -= allocated;
           list_for_each_entry(req, &batch->head, ki_batch) {
                   list_add(&req->ki_list, &ctx->active_reqs);
                   ctx->reqs_active++;
           }
   
           kunmap_atomic(ring);
           spin_unlock_irq(&ctx->ctx_lock);
   
   out:
           return allocated;
   }
   
   static inline struct kiocb *aio_get_req(struct kioctx *ctx,
                                           struct kiocb_batch *batch)
   {
           struct kiocb *req;
   
           if (list_empty(&batch->head))
                   if (kiocb_batch_refill(ctx, batch) == 0)
                           return NULL;
           req = list_first_entry(&batch->head, struct kiocb, ki_batch);
           list_del(&req->ki_batch);
           return req;
   }
   
   static inline void really_put_req(struct kioctx *ctx, struct kiocb *req)
   {
           assert_spin_locked(&ctx->ctx_lock);
   
           if (req->ki_eventfd != NULL)
                   eventfd_ctx_put(req->ki_eventfd);
           if (req->ki_dtor)
                   req->ki_dtor(req);
           if (req->ki_iovec != &req->ki_inline_vec)
                   kfree(req->ki_iovec);
           kmem_cache_free(kiocb_cachep, req);
           ctx->reqs_active--;
   
           if (unlikely(!ctx->reqs_active && ctx->dead))
                   wake_up_all(&ctx->wait);
   }
   
   /* __aio_put_req
    *      Returns true if this put was the last user of the request.
    */
   static int __aio_put_req(struct kioctx *ctx, struct kiocb *req)
   {
           dprintk(KERN_DEBUG "aio_put(%p): f_count=%ld\n",
                   req, atomic_long_read(&req->ki_filp->f_count));
   
           assert_spin_locked(&ctx->ctx_lock);
   
           req->ki_users--;
           BUG_ON(req->ki_users < 0);
           if (likely(req->ki_users))
                   return 0;
           list_del(&req->ki_list);                /* remove from active_reqs */
           req->ki_cancel = NULL;
           req->ki_retry = NULL;
   
           fput(req->ki_filp);
           req->ki_filp = NULL;
           really_put_req(ctx, req);
           return 1;
   }
   
   /* aio_put_req
    *      Returns true if this put was the last user of the kiocb,
    *      false if the request is still in use.
    */
   int aio_put_req(struct kiocb *req)
   {
           struct kioctx *ctx = req->ki_ctx;
           int ret;
           spin_lock_irq(&ctx->ctx_lock);
           ret = __aio_put_req(ctx, req);
           spin_unlock_irq(&ctx->ctx_lock);
           return ret;
   }
   EXPORT_SYMBOL(aio_put_req);
   
   static struct kioctx *lookup_ioctx(unsigned long ctx_id)
   {
           struct mm_struct *mm = current->mm;
           struct kioctx *ctx, *ret = NULL;
           struct hlist_node *n;
   
           rcu_read_lock();
   
           hlist_for_each_entry_rcu(ctx, n, &mm->ioctx_list, list) {
                   /*
                    * RCU protects us against accessing freed memory but
                    * we have to be careful not to get a reference when the
                    * reference count already dropped to 0 (ctx->dead test
                    * is unreliable because of races).
                    */
                   if (ctx->user_id == ctx_id && !ctx->dead && try_get_ioctx(ctx)){
                           ret = ctx;
                           break;
                   }
           }
   
           rcu_read_unlock();
           return ret;
   }
   
   /*
    * Queue up a kiocb to be retried. Assumes that the kiocb
    * has already been marked as kicked, and places it on
    * the retry run list for the corresponding ioctx, if it
    * isn't already queued. Returns 1 if it actually queued
    * the kiocb (to tell the caller to activate the work
    * queue to process it), or 0, if it found that it was
    * already queued.
    */
   static inline int __queue_kicked_iocb(struct kiocb *iocb)
   {
           struct kioctx *ctx = iocb->ki_ctx;
   
           assert_spin_locked(&ctx->ctx_lock);
   
           if (list_empty(&iocb->ki_run_list)) {
                   list_add_tail(&iocb->ki_run_list,
                           &ctx->run_list);
                   return 1;
           }
           return 0;
   }
   
   /* aio_run_iocb
    *      This is the core aio execution routine. It is
    *      invoked both for initial i/o submission and
    *      subsequent retries via the aio_kick_handler.
    *      Expects to be invoked with iocb->ki_ctx->lock
    *      already held. The lock is released and reacquired
    *      as needed during processing.
    *
    * Calls the iocb retry method (already setup for the
    * iocb on initial submission) for operation specific
    * handling, but takes care of most of common retry
    * execution details for a given iocb. The retry method
    * needs to be non-blocking as far as possible, to avoid
    * holding up other iocbs waiting to be serviced by the
    * retry kernel thread.
    *
    * The trickier parts in this code have to do with
    * ensuring that only one retry instance is in progress
    * for a given iocb at any time. Providing that guarantee
    * simplifies the coding of individual aio operations as
    * it avoids various potential races.
    */
   static ssize_t aio_run_iocb(struct kiocb *iocb)
   {
           struct kioctx   *ctx = iocb->ki_ctx;
           ssize_t (*retry)(struct kiocb *);
           ssize_t ret;
   
           if (!(retry = iocb->ki_retry)) {
                   printk("aio_run_iocb: iocb->ki_retry = NULL\n");
                   return 0;
           }
   
           /*
            * We don't want the next retry iteration for this
            * operation to start until this one has returned and
            * updated the iocb state. However, wait_queue functions
            * can trigger a kick_iocb from interrupt context in the
            * meantime, indicating that data is available for the next
            * iteration. We want to remember that and enable the
            * next retry iteration _after_ we are through with
            * this one.
            *
            * So, in order to be able to register a "kick", but
            * prevent it from being queued now, we clear the kick
            * flag, but make the kick code *think* that the iocb is
            * still on the run list until we are actually done.
            * When we are done with this iteration, we check if
            * the iocb was kicked in the meantime and if so, queue
            * it up afresh.
            */
   
           kiocbClearKicked(iocb);
   
           /*
            * This is so that aio_complete knows it doesn't need to
            * pull the iocb off the run list (We can't just call
            * INIT_LIST_HEAD because we don't want a kick_iocb to
            * queue this on the run list yet)
            */
           iocb->ki_run_list.next = iocb->ki_run_list.prev = NULL;
           spin_unlock_irq(&ctx->ctx_lock);
   
           /* Quit retrying if the i/o has been cancelled */
           if (kiocbIsCancelled(iocb)) {
                   ret = -EINTR;
                   aio_complete(iocb, ret, 0);
                   /* must not access the iocb after this */
                   goto out;
           }
   
           /*
            * Now we are all set to call the retry method in async
            * context.
            */
           ret = retry(iocb);
   
           if (ret != -EIOCBRETRY && ret != -EIOCBQUEUED) {
                   /*
                    * There's no easy way to restart the syscall since other AIO's
                    * may be already running. Just fail this IO with EINTR.
                    */
                   if (unlikely(ret == -ERESTARTSYS || ret == -ERESTARTNOINTR ||
                                ret == -ERESTARTNOHAND || ret == -ERESTART_RESTARTBLOCK))
                           ret = -EINTR;
                   aio_complete(iocb, ret, 0);
           }
   out:
           spin_lock_irq(&ctx->ctx_lock);
   
           if (-EIOCBRETRY == ret) {
                   /*
                    * OK, now that we are done with this iteration
                    * and know that there is more left to go,
                    * this is where we let go so that a subsequent
                    * "kick" can start the next iteration
                    */
   
                   /* will make __queue_kicked_iocb succeed from here on */
                   INIT_LIST_HEAD(&iocb->ki_run_list);
                   /* we must queue the next iteration ourselves, if it
                    * has already been kicked */
                   if (kiocbIsKicked(iocb)) {
                           __queue_kicked_iocb(iocb);
   
                           /*
                            * __queue_kicked_iocb will always return 1 here, because
                            * iocb->ki_run_list is empty at this point so it should
                            * be safe to unconditionally queue the context into the
                            * work queue.
                            */
                           aio_queue_work(ctx);
                   }
           }
           return ret;
   }
   
   /*
    * __aio_run_iocbs:
    *      Process all pending retries queued on the ioctx
    *      run list.
    * Assumes it is operating within the aio issuer's mm
    * context.
    */
   static int __aio_run_iocbs(struct kioctx *ctx)
   {
           struct kiocb *iocb;
           struct list_head run_list;
   
           assert_spin_locked(&ctx->ctx_lock);
   
           list_replace_init(&ctx->run_list, &run_list);
           while (!list_empty(&run_list)) {
                   iocb = list_entry(run_list.next, struct kiocb,
                           ki_run_list);
                   list_del(&iocb->ki_run_list);
                   /*
                    * Hold an extra reference while retrying i/o.
                    */
                   iocb->ki_users++;       /* grab extra reference */
                   aio_run_iocb(iocb);
                   __aio_put_req(ctx, iocb);
           }
           if (!list_empty(&ctx->run_list))
                   return 1;
           return 0;
   }
   
   static void aio_queue_work(struct kioctx * ctx)
   {
           unsigned long timeout;
           /*
            * if someone is waiting, get the work started right
            * away, otherwise, use a longer delay
            */
           smp_mb();
           if (waitqueue_active(&ctx->wait))
                   timeout = 1;
           else
                   timeout = HZ/10;
           queue_delayed_work(aio_wq, &ctx->wq, timeout);
   }
   
   /*
    * aio_run_all_iocbs:
    *      Process all pending retries queued on the ioctx
    *      run list, and keep running them until the list
    *      stays empty.
    * Assumes it is operating within the aio issuer's mm context.
    */
   static inline void aio_run_all_iocbs(struct kioctx *ctx)
   {
           spin_lock_irq(&ctx->ctx_lock);
           while (__aio_run_iocbs(ctx))
                   ;
           spin_unlock_irq(&ctx->ctx_lock);
   }
   
   /*
    * aio_kick_handler:
    *      Work queue handler triggered to process pending
    *      retries on an ioctx. Takes on the aio issuer's
    *      mm context before running the iocbs, so that
    *      copy_xxx_user operates on the issuer's address
    *      space.
    * Run on aiod's context.
    */
   static void aio_kick_handler(struct work_struct *work)
   {
           struct kioctx *ctx = container_of(work, struct kioctx, wq.work);
           mm_segment_t oldfs = get_fs();
           struct mm_struct *mm;
           int requeue;
   
           set_fs(USER_DS);
           use_mm(ctx->mm);
           spin_lock_irq(&ctx->ctx_lock);
           requeue =__aio_run_iocbs(ctx);
           mm = ctx->mm;
           spin_unlock_irq(&ctx->ctx_lock);
           unuse_mm(mm);
           set_fs(oldfs);
           /*
            * we're in a worker thread already; no point using non-zero delay
            */
           if (requeue)
                   queue_delayed_work(aio_wq, &ctx->wq, 0);
   }
   
   
   /*
    * Called by kick_iocb to queue the kiocb for retry
    * and if required activate the aio work queue to process
    * it
    */
   static void try_queue_kicked_iocb(struct kiocb *iocb)
   {
           struct kioctx   *ctx = iocb->ki_ctx;
           unsigned long flags;
           int run = 0;
   
           spin_lock_irqsave(&ctx->ctx_lock, flags);
           /* set this inside the lock so that we can't race with aio_run_iocb()
            * testing it and putting the iocb on the run list under the lock */
           if (!kiocbTryKick(iocb))
                   run = __queue_kicked_iocb(iocb);
           spin_unlock_irqrestore(&ctx->ctx_lock, flags);
           if (run)
                   aio_queue_work(ctx);
   }
   
   /*
    * kick_iocb:
    *      Called typically from a wait queue callback context
    *      to trigger a retry of the iocb.
    *      The retry is usually executed by aio workqueue
    *      threads (See aio_kick_handler).
    */
   void kick_iocb(struct kiocb *iocb)
   {
           /* sync iocbs are easy: they can only ever be executing from a 
            * single context. */
           if (is_sync_kiocb(iocb)) {
                   kiocbSetKicked(iocb);
                   wake_up_process(iocb->ki_obj.tsk);
                   return;
           }
   
           try_queue_kicked_iocb(iocb);
   }
   EXPORT_SYMBOL(kick_iocb);
   
   /* aio_complete
    *      Called when the io request on the given iocb is complete.
    *      Returns true if this is the last user of the request.  The 
    *      only other user of the request can be the cancellation code.
    */
   int aio_complete(struct kiocb *iocb, long res, long res2)
   {
           struct kioctx   *ctx = iocb->ki_ctx;
           struct aio_ring_info    *info;
           struct aio_ring *ring;
           struct io_event *event;
           unsigned long   flags;
           unsigned long   tail;
           int             ret;
   
           /*
            * Special case handling for sync iocbs:
            *  - events go directly into the iocb for fast handling
            *  - the sync task with the iocb in its stack holds the single iocb
            *    ref, no other paths have a way to get another ref
            *  - the sync task helpfully left a reference to itself in the iocb
            */
           if (is_sync_kiocb(iocb)) {
                   BUG_ON(iocb->ki_users != 1);
                   iocb->ki_user_data = res;
                   iocb->ki_users = 0;
                   wake_up_process(iocb->ki_obj.tsk);
                   return 1;
           }
   
           info = &ctx->ring_info;
   
           /* add a completion event to the ring buffer.
            * must be done holding ctx->ctx_lock to prevent
            * other code from messing with the tail
            * pointer since we might be called from irq
            * context.
            */
           spin_lock_irqsave(&ctx->ctx_lock, flags);
   
           if (iocb->ki_run_list.prev && !list_empty(&iocb->ki_run_list))
                   list_del_init(&iocb->ki_run_list);
   
           /*
            * cancelled requests don't get events, userland was given one
            * when the event got cancelled.
            */
           if (kiocbIsCancelled(iocb))
                   goto put_rq;
   
           ring = kmap_atomic(info->ring_pages[0]);
   
           tail = info->tail;
           event = aio_ring_event(info, tail);
           if (++tail >= info->nr)
                   tail = 0;
   
           event->obj = (u64)(unsigned long)iocb->ki_obj.user;
           event->data = iocb->ki_user_data;
           event->res = res;
           event->res2 = res2;
   
           dprintk("aio_complete: %p[%lu]: %p: %p %Lx %lx %lx\n",
                   ctx, tail, iocb, iocb->ki_obj.user, iocb->ki_user_data,
                   res, res2);
   
           /* after flagging the request as done, we
            * must never even look at it again
            */
           smp_wmb();      /* make event visible before updating tail */
   
           info->tail = tail;
           ring->tail = tail;
   
           put_aio_ring_event(event);
           kunmap_atomic(ring);
   
           pr_debug("added to ring %p at [%lu]\n", iocb, tail);
   
           /*
            * Check if the user asked us to deliver the result through an
            * eventfd. The eventfd_signal() function is safe to be called
            * from IRQ context.
            */
           if (iocb->ki_eventfd != NULL)
                   eventfd_signal(iocb->ki_eventfd, 1);
   
   put_rq:
           /* everything turned out well, dispose of the aiocb. */
           ret = __aio_put_req(ctx, iocb);
   
           /*
            * We have to order our ring_info tail store above and test
            * of the wait list below outside the wait lock.  This is
            * like in wake_up_bit() where clearing a bit has to be
            * ordered with the unlocked test.
            */
           smp_mb();
   
           if (waitqueue_active(&ctx->wait))
                   wake_up(&ctx->wait);
   
           spin_unlock_irqrestore(&ctx->ctx_lock, flags);
           return ret;
   }
   EXPORT_SYMBOL(aio_complete);
   
   /* aio_read_evt
    *      Pull an event off of the ioctx's event ring.  Returns the number of 
    *      events fetched (0 or 1 ;-)
    *      FIXME: make this use cmpxchg.
    *      TODO: make the ringbuffer user mmap()able (requires FIXME).
    */
  static int aio_read_evt(struct kioctx *ioctx, struct io_event *ent)
  {
          struct aio_ring_info *info = &ioctx->ring_info;
          struct aio_ring *ring;
          unsigned long head;
          int ret = 0;
  
          ring = kmap_atomic(info->ring_pages[0]);
          dprintk("in aio_read_evt h%lu t%lu m%lu\n",
                   (unsigned long)ring->head, (unsigned long)ring->tail,
                   (unsigned long)ring->nr);
  
          if (ring->head == ring->tail)
                  goto out;
  
          spin_lock(&info->ring_lock);
  
          head = ring->head % info->nr;
          if (head != ring->tail) {
                  struct io_event *evp = aio_ring_event(info, head);
                  *ent = *evp;
                  head = (head + 1) % info->nr;
                  smp_mb(); /* finish reading the event before updatng the head */
                  ring->head = head;
                  ret = 1;
                  put_aio_ring_event(evp);
          }
          spin_unlock(&info->ring_lock);
  
  out:
          kunmap_atomic(ring);
          dprintk("leaving aio_read_evt: %d  h%lu t%lu\n", ret,
                   (unsigned long)ring->head, (unsigned long)ring->tail);
          return ret;
  }
  
  struct aio_timeout {
          struct timer_list       timer;
          int                     timed_out;
          struct task_struct      *p;
  };
  
  static void timeout_func(unsigned long data)
  {
          struct aio_timeout *to = (struct aio_timeout *)data;
  
          to->timed_out = 1;
          wake_up_process(to->p);
  }
  
  static inline void init_timeout(struct aio_timeout *to)
  {
          setup_timer_on_stack(&to->timer, timeout_func, (unsigned long) to);
          to->timed_out = 0;
          to->p = current;
  }
  
  static inline void set_timeout(long start_jiffies, struct aio_timeout *to,
                                 const struct timespec *ts)
  {
          to->timer.expires = start_jiffies + timespec_to_jiffies(ts);
          if (time_after(to->timer.expires, jiffies))
                  add_timer(&to->timer);
          else
                  to->timed_out = 1;
  }
  
  static inline void clear_timeout(struct aio_timeout *to)
  {
          del_singleshot_timer_sync(&to->timer);
  }
  
  static int read_events(struct kioctx *ctx,
                          long min_nr, long nr,
                          struct io_event __user *event,
                          struct timespec __user *timeout)
  {
          long                    start_jiffies = jiffies;
          struct task_struct      *tsk = current;
          DECLARE_WAITQUEUE(wait, tsk);
          int                     ret;
          int                     i = 0;
          struct io_event         ent;
          struct aio_timeout      to;
          int                     retry = 0;
  
          /* needed to zero any padding within an entry (there shouldn't be 
           * any, but C is fun!
           */
          memset(&ent, 0, sizeof(ent));
  retry:
          ret = 0;
          while (likely(i < nr)) {
                  ret = aio_read_evt(ctx, &ent);
                  if (unlikely(ret <= 0))
                          break;
  
                  dprintk("read event: %Lx %Lx %Lx %Lx\n",
                          ent.data, ent.obj, ent.res, ent.res2);
  
                  /* Could we split the check in two? */
                  ret = -EFAULT;
                  if (unlikely(copy_to_user(event, &ent, sizeof(ent)))) {
                          dprintk("aio: lost an event due to EFAULT.\n");
                          break;
                  }
                  ret = 0;
  
                  /* Good, event copied to userland, update counts. */
                  event ++;
                  i ++;
          }
  
          if (min_nr <= i)
                  return i;
          if (ret)
                  return ret;
  
          /* End fast path */
  
          /* racey check, but it gets redone */
          if (!retry && unlikely(!list_empty(&ctx->run_list))) {
                  retry = 1;
                  aio_run_all_iocbs(ctx);
                  goto retry;
          }
  
          init_timeout(&to);
          if (timeout) {
                  struct timespec ts;
                  ret = -EFAULT;
                  if (unlikely(copy_from_user(&ts, timeout, sizeof(ts))))
                          goto out;
  
                  set_timeout(start_jiffies, &to, &ts);
          }
  
          while (likely(i < nr)) {
                  add_wait_queue_exclusive(&ctx->wait, &wait);
                  do {
                          set_task_state(tsk, TASK_INTERRUPTIBLE);
                          ret = aio_read_evt(ctx, &ent);
                          if (ret)
                                  break;
                          if (min_nr <= i)
                                  break;
                          if (unlikely(ctx->dead)) {
                                  ret = -EINVAL;
                                  break;
                          }
                          if (to.timed_out)       /* Only check after read evt */
                                  break;
                          /* Try to only show up in io wait if there are ops
                           *  in flight */
                          if (ctx->reqs_active)
                                  io_schedule();
                          else
                                  schedule();
                          if (signal_pending(tsk)) {
                                  ret = -EINTR;
                                  break;
                          }
                          /*ret = aio_read_evt(ctx, &ent);*/
                  } while (1) ;
  
                  set_task_state(tsk, TASK_RUNNING);
                  remove_wait_queue(&ctx->wait, &wait);
  
                  if (unlikely(ret <= 0))
                          break;
  
                  ret = -EFAULT;
                  if (unlikely(copy_to_user(event, &ent, sizeof(ent)))) {
                          dprintk("aio: lost an event due to EFAULT.\n");
                          break;
                  }
  
                  /* Good, event copied to userland, update counts. */
                  event ++;
                  i ++;
          }
  
          if (timeout)
                  clear_timeout(&to);
  out:
          destroy_timer_on_stack(&to.timer);
          return i ? i : ret;
  }
  
  /* Take an ioctx and remove it from the list of ioctx's.  Protects 
   * against races with itself via ->dead.
   */
  static void io_destroy(struct kioctx *ioctx)
  {
          struct mm_struct *mm = current->mm;
          int was_dead;
  
          /* delete the entry from the list is someone else hasn't already */
          spin_lock(&mm->ioctx_lock);
          was_dead = ioctx->dead;
          ioctx->dead = 1;
          hlist_del_rcu(&ioctx->list);
          spin_unlock(&mm->ioctx_lock);
  
          dprintk("aio_release(%p)\n", ioctx);
          if (likely(!was_dead))
                  put_ioctx(ioctx);       /* twice for the list */
  
          kill_ctx(ioctx);
  
          /*
           * Wake up any waiters.  The setting of ctx->dead must be seen
           * by other CPUs at this point.  Right now, we rely on the
           * locking done by the above calls to ensure this consistency.
           */
          wake_up_all(&ioctx->wait);
  }
  
  /* sys_io_setup:
   *      Create an aio_context capable of receiving at least nr_events.
   *      ctxp must not point to an aio_context that already exists, and
   *      must be initialized to 0 prior to the call.  On successful
   *      creation of the aio_context, *ctxp is filled in with the resulting 
   *      handle.  May fail with -EINVAL if *ctxp is not initialized,
   *      if the specified nr_events exceeds internal limits.  May fail 
   *      with -EAGAIN if the specified nr_events exceeds the user's limit 
   *      of available events.  May fail with -ENOMEM if insufficient kernel
   *      resources are available.  May fail with -EFAULT if an invalid
   *      pointer is passed for ctxp.  Will fail with -ENOSYS if not
   *      implemented.
   */
  SYSCALL_DEFINE2(io_setup, unsigned, nr_events, aio_context_t __user *, ctxp)
  {
          struct kioctx *ioctx = NULL;
          unsigned long ctx;
          long ret;
  
          ret = get_user(ctx, ctxp);
          if (unlikely(ret))
                  goto out;
  
          ret = -EINVAL;
          if (unlikely(ctx || nr_events == 0)) {
                  pr_debug("EINVAL: io_setup: ctx %lu nr_events %u\n",
                           ctx, nr_events);
                  goto out;
          }
  
          ioctx = ioctx_alloc(nr_events);
          ret = PTR_ERR(ioctx);
          if (!IS_ERR(ioctx)) {
                  ret = put_user(ioctx->user_id, ctxp);
                  if (ret)
                          io_destroy(ioctx);
                  put_ioctx(ioctx);
          }
  
  out:
          return ret;
  }
  
  /* sys_io_destroy:
   *      Destroy the aio_context specified.  May cancel any outstanding 
   *      AIOs and block on completion.  Will fail with -ENOSYS if not
   *      implemented.  May fail with -EINVAL if the context pointed to
   *      is invalid.
   */
  SYSCALL_DEFINE1(io_destroy, aio_context_t, ctx)
  {
          struct kioctx *ioctx = lookup_ioctx(ctx);
          if (likely(NULL != ioctx)) {
                  io_destroy(ioctx);
                  put_ioctx(ioctx);
                  return 0;
          }
          pr_debug("EINVAL: io_destroy: invalid context id\n");
          return -EINVAL;
  }
  
  static void aio_advance_iovec(struct kiocb *iocb, ssize_t ret)
  {
          struct iovec *iov = &iocb->ki_iovec[iocb->ki_cur_seg];
  
          BUG_ON(ret <= 0);
  
          while (iocb->ki_cur_seg < iocb->ki_nr_segs && ret > 0) {
                  ssize_t this = min((ssize_t)iov->iov_len, ret);
                  iov->iov_base += this;
                  iov->iov_len -= this;
                  iocb->ki_left -= this;
                  ret -= this;
                  if (iov->iov_len == 0) {
                          iocb->ki_cur_seg++;
                          iov++;
                  }
          }
  
          /* the caller should not have done more io than what fit in
           * the remaining iovecs */
          BUG_ON(ret > 0 && iocb->ki_left == 0);
  }
  
  static ssize_t aio_rw_vect_retry(struct kiocb *iocb)
  {
          struct file *file = iocb->ki_filp;
          struct address_space *mapping = file->f_mapping;
          struct inode *inode = mapping->host;
          ssize_t (*rw_op)(struct kiocb *, const struct iovec *,
                           unsigned long, loff_t);
          ssize_t ret = 0;
          unsigned short opcode;
  
          if ((iocb->ki_opcode == IOCB_CMD_PREADV) ||
                  (iocb->ki_opcode == IOCB_CMD_PREAD)) {
                  rw_op = file->f_op->aio_read;
                  opcode = IOCB_CMD_PREADV;
          } else {
                  rw_op = file->f_op->aio_write;
                  opcode = IOCB_CMD_PWRITEV;
          }
  
          /* This matches the pread()/pwrite() logic */
          if (iocb->ki_pos < 0)
                  return -EINVAL;
  
          do {
                  ret = rw_op(iocb, &iocb->ki_iovec[iocb->ki_cur_seg],
                              iocb->ki_nr_segs - iocb->ki_cur_seg,
                              iocb->ki_pos);
                  if (ret > 0)
                          aio_advance_iovec(iocb, ret);
  
          /* retry all partial writes.  retry partial reads as long as its a
           * regular file. */
          } while (ret > 0 && iocb->ki_left > 0 &&
                   (opcode == IOCB_CMD_PWRITEV ||
                    (!S_ISFIFO(inode->i_mode) && !S_ISSOCK(inode->i_mode))));
  
          /* This means we must have transferred all that we could */
          /* No need to retry anymore */
          if ((ret == 0) || (iocb->ki_left == 0))
                  ret = iocb->ki_nbytes - iocb->ki_left;
  
          /* If we managed to write some out we return that, rather than
           * the eventual error. */
          if (opcode == IOCB_CMD_PWRITEV
              && ret < 0 && ret != -EIOCBQUEUED && ret != -EIOCBRETRY
              && iocb->ki_nbytes - iocb->ki_left)
                  ret = iocb->ki_nbytes - iocb->ki_left;
  
          return ret;
  }
  
  static ssize_t aio_fdsync(struct kiocb *iocb)
  {
          struct file *file = iocb->ki_filp;
          ssize_t ret = -EINVAL;
  
          if (file->f_op->aio_fsync)
                  ret = file->f_op->aio_fsync(iocb, 1);
          return ret;
  }
  
  static ssize_t aio_fsync(struct kiocb *iocb)
  {
          struct file *file = iocb->ki_filp;
          ssize_t ret = -EINVAL;
  
          if (file->f_op->aio_fsync)
                  ret = file->f_op->aio_fsync(iocb, 0);
          return ret;
  }
  
  static ssize_t aio_setup_vectored_rw(int type, struct kiocb *kiocb, bool compat)
  {
          ssize_t ret;
  
  #ifdef CONFIG_COMPAT
          if (compat)
                  ret = compat_rw_copy_check_uvector(type,
                                  (struct compat_iovec __user *)kiocb->ki_buf,
                                  kiocb->ki_nbytes, 1, &kiocb->ki_inline_vec,
                                  &kiocb->ki_iovec);
          else
  #endif
                  ret = rw_copy_check_uvector(type,
                                  (struct iovec __user *)kiocb->ki_buf,
                                  kiocb->ki_nbytes, 1, &kiocb->ki_inline_vec,
                                  &kiocb->ki_iovec);
          if (ret < 0)
                  goto out;
  
          ret = rw_verify_area(type, kiocb->ki_filp, &kiocb->ki_pos, ret);
          if (ret < 0)
                  goto out;
  
          kiocb->ki_nr_segs = kiocb->ki_nbytes;
          kiocb->ki_cur_seg = 0;
          /* ki_nbytes/left now reflect bytes instead of segs */
          kiocb->ki_nbytes = ret;
          kiocb->ki_left = ret;
  
          ret = 0;
  out:
          return ret;
  }
  
  static ssize_t aio_setup_single_vector(int type, struct file * file, struct kiocb *kiocb)
  {
          int bytes;
  
          bytes = rw_verify_area(type, file, &kiocb->ki_pos, kiocb->ki_left);
          if (bytes < 0)
                  return bytes;
  
          kiocb->ki_iovec = &kiocb->ki_inline_vec;
          kiocb->ki_iovec->iov_base = kiocb->ki_buf;
          kiocb->ki_iovec->iov_len = bytes;
          kiocb->ki_nr_segs = 1;
          kiocb->ki_cur_seg = 0;
          return 0;
  }
  
  /*
   * aio_setup_iocb:
   *      Performs the initial checks and aio retry method
   *      setup for the kiocb at the time of io submission.
   */
  static ssize_t aio_setup_iocb(struct kiocb *kiocb, bool compat)
  {
          struct file *file = kiocb->ki_filp;
          ssize_t ret = 0;
  
          switch (kiocb->ki_opcode) {
          case IOCB_CMD_PREAD:
                  ret = -EBADF;
                  if (unlikely(!(file->f_mode & FMODE_READ)))
                          break;
                  ret = -EFAULT;
                  if (unlikely(!access_ok(VERIFY_WRITE, kiocb->ki_buf,
                          kiocb->ki_left)))
                          break;
                  ret = aio_setup_single_vector(READ, file, kiocb);
                  if (ret)
                          break;
                  ret = -EINVAL;
                  if (file->f_op->aio_read)
                          kiocb->ki_retry = aio_rw_vect_retry;
                  break;
          case IOCB_CMD_PWRITE:
                  ret = -EBADF;
                  if (unlikely(!(file->f_mode & FMODE_WRITE)))
                          break;
                  ret = -EFAULT;
                  if (unlikely(!access_ok(VERIFY_READ, kiocb->ki_buf,
                          kiocb->ki_left)))
                          break;
                  ret = aio_setup_single_vector(WRITE, file, kiocb);
                  if (ret)
                          break;
                  ret = -EINVAL;
                  if (file->f_op->aio_write)
                          kiocb->ki_retry = aio_rw_vect_retry;
                  break;
          case IOCB_CMD_PREADV:
                  ret = -EBADF;
                  if (unlikely(!(file->f_mode & FMODE_READ)))
                          break;
                  ret = aio_setup_vectored_rw(READ, kiocb, compat);
                  if (ret)
                          break;
                  ret = -EINVAL;
                  if (file->f_op->aio_read)
                          kiocb->ki_retry = aio_rw_vect_retry;
                  break;
          case IOCB_CMD_PWRITEV:
                  ret = -EBADF;
                  if (unlikely(!(file->f_mode & FMODE_WRITE)))
                          break;
                  ret = aio_setup_vectored_rw(WRITE, kiocb, compat);
                  if (ret)
                          break;
                  ret = -EINVAL;
                  if (file->f_op->aio_write)
                          kiocb->ki_retry = aio_rw_vect_retry;
                  break;
          case IOCB_CMD_FDSYNC:
                  ret = -EINVAL;
                  if (file->f_op->aio_fsync)
                          kiocb->ki_retry = aio_fdsync;
                  break;
          case IOCB_CMD_FSYNC:
                  ret = -EINVAL;
                  if (file->f_op->aio_fsync)
                          kiocb->ki_retry = aio_fsync;
                  break;
          default:
                  dprintk("EINVAL: io_submit: no operation provided\n");
                  ret = -EINVAL;
          }
  
          if (!kiocb->ki_retry)
                  return ret;
  
          return 0;
  }
  
  static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
                           struct iocb *iocb, struct kiocb_batch *batch,
                           bool compat)
  {
          struct kiocb *req;
          struct file *file;
          ssize_t ret;
  
          /* enforce forwards compatibility on users */
          if (unlikely(iocb->aio_reserved1 || iocb->aio_reserved2)) {
                  pr_debug("EINVAL: io_submit: reserve field set\n");
                  return -EINVAL;
          }
  
          /* prevent overflows */
          if (unlikely(
              (iocb->aio_buf != (unsigned long)iocb->aio_buf) ||
              (iocb->aio_nbytes != (size_t)iocb->aio_nbytes) ||
              ((ssize_t)iocb->aio_nbytes < 0)
             )) {
                  pr_debug("EINVAL: io_submit: overflow check\n");
                  return -EINVAL;
          }
  
          file = fget(iocb->aio_fildes);
          if (unlikely(!file))
                  return -EBADF;
  
          req = aio_get_req(ctx, batch);  /* returns with 2 references to req */
          if (unlikely(!req)) {
                  fput(file);
                  return -EAGAIN;
          }
          req->ki_filp = file;
          if (iocb->aio_flags & IOCB_FLAG_RESFD) {
                  /*
                   * If the IOCB_FLAG_RESFD flag of aio_flags is set, get an
                   * instance of the file* now. The file descriptor must be
                   * an eventfd() fd, and will be signaled for each completed
                   * event using the eventfd_signal() function.
                   */
                  req->ki_eventfd = eventfd_ctx_fdget((int) iocb->aio_resfd);
                  if (IS_ERR(req->ki_eventfd)) {
                          ret = PTR_ERR(req->ki_eventfd);
                          req->ki_eventfd = NULL;
                          goto out_put_req;
                  }
          }
  
          ret = put_user(req->ki_key, &user_iocb->aio_key);
          if (unlikely(ret)) {
                  dprintk("EFAULT: aio_key\n");
                  goto out_put_req;
          }
  
          req->ki_obj.user = user_iocb;
          req->ki_user_data = iocb->aio_data;
          req->ki_pos = iocb->aio_offset;
  
          req->ki_buf = (char __user *)(unsigned long)iocb->aio_buf;
          req->ki_left = req->ki_nbytes = iocb->aio_nbytes;
          req->ki_opcode = iocb->aio_lio_opcode;
  
          ret = aio_setup_iocb(req, compat);
  
          if (ret)
                  goto out_put_req;
  
          spin_lock_irq(&ctx->ctx_lock);
          /*
           * We could have raced with io_destroy() and are currently holding a
           * reference to ctx which should be destroyed. We cannot submit IO
           * since ctx gets freed as soon as io_submit() puts its reference.  The
           * check here is reliable: io_destroy() sets ctx->dead before waiting
           * for outstanding IO and the barrier between these two is realized by
           * unlock of mm->ioctx_lock and lock of ctx->ctx_lock.  Analogously we
           * increment ctx->reqs_active before checking for ctx->dead and the
           * barrier is realized by unlock and lock of ctx->ctx_lock. Thus if we
           * don't see ctx->dead set here, io_destroy() waits for our IO to
           * finish.
           */
          if (ctx->dead) {
                  spin_unlock_irq(&ctx->ctx_lock);
                  ret = -EINVAL;
                  goto out_put_req;
          }
          aio_run_iocb(req);
          if (!list_empty(&ctx->run_list)) {
                  /* drain the run list */
                  while (__aio_run_iocbs(ctx))
                          ;
          }
          spin_unlock_irq(&ctx->ctx_lock);
  
          aio_put_req(req);       /* drop extra ref to req */
          return 0;
  
  out_put_req:
          aio_put_req(req);       /* drop extra ref to req */
          aio_put_req(req);       /* drop i/o ref to req */
          return ret;
  }
  
  long do_io_submit(aio_context_t ctx_id, long nr,
                    struct iocb __user *__user *iocbpp, bool compat)
  {
          struct kioctx *ctx;
          long ret = 0;
          int i = 0;
          struct blk_plug plug;
          struct kiocb_batch batch;
  
          if (unlikely(nr < 0))
                  return -EINVAL;
  
          if (unlikely(nr > LONG_MAX/sizeof(*iocbpp)))
                  nr = LONG_MAX/sizeof(*iocbpp);
  
          if (unlikely(!access_ok(VERIFY_READ, iocbpp, (nr*sizeof(*iocbpp)))))
                  return -EFAULT;
  
          ctx = lookup_ioctx(ctx_id);
          if (unlikely(!ctx)) {
                  pr_debug("EINVAL: io_submit: invalid context id\n");
                  return -EINVAL;
          }
  
          kiocb_batch_init(&batch, nr);
  
          blk_start_plug(&plug);
  
          /*
           * AKPM: should this return a partial result if some of the IOs were
           * successfully submitted?
           */
          for (i=0; i<nr; i++) {
                  struct iocb __user *user_iocb;
                  struct iocb tmp;
  
                  if (unlikely(__get_user(user_iocb, iocbpp + i))) {
                          ret = -EFAULT;
                          break;
                  }
  
                  if (unlikely(copy_from_user(&tmp, user_iocb, sizeof(tmp)))) {
                          ret = -EFAULT;
                          break;
                  }
  
                  ret = io_submit_one(ctx, user_iocb, &tmp, &batch, compat);
                  if (ret)
                          break;
          }
          blk_finish_plug(&plug);
  
          kiocb_batch_free(ctx, &batch);
          put_ioctx(ctx);
          return i ? i : ret;
  }
  
  /* sys_io_submit:
   *      Queue the nr iocbs pointed to by iocbpp for processing.  Returns
   *      the number of iocbs queued.  May return -EINVAL if the aio_context
   *      specified by ctx_id is invalid, if nr is < 0, if the iocb at
   *      *iocbpp[0] is not properly initialized, if the operation specified
   *      is invalid for the file descriptor in the iocb.  May fail with
   *      -EFAULT if any of the data structures point to invalid data.  May
   *      fail with -EBADF if the file descriptor specified in the first
   *      iocb is invalid.  May fail with -EAGAIN if insufficient resources
   *      are available to queue any iocbs.  Will return 0 if nr is 0.  Will
   *      fail with -ENOSYS if not implemented.
   */
  SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
                  struct iocb __user * __user *, iocbpp)
  {
          return do_io_submit(ctx_id, nr, iocbpp, 0);
  }
  
  /* lookup_kiocb
   *      Finds a given iocb for cancellation.
   */
  static struct kiocb *lookup_kiocb(struct kioctx *ctx, struct iocb __user *iocb,
                                    u32 key)
  {
          struct list_head *pos;
  
          assert_spin_locked(&ctx->ctx_lock);
  
          /* TODO: use a hash or array, this sucks. */
          list_for_each(pos, &ctx->active_reqs) {
                  struct kiocb *kiocb = list_kiocb(pos);
                  if (kiocb->ki_obj.user == iocb && kiocb->ki_key == key)
                          return kiocb;
          }
          return NULL;
  }
  
  /* sys_io_cancel:
   *      Attempts to cancel an iocb previously passed to io_submit.  If
   *      the operation is successfully cancelled, the resulting event is
   *      copied into the memory pointed to by result without being placed
   *      into the completion queue and 0 is returned.  May fail with
   *      -EFAULT if any of the data structures pointed to are invalid.
   *      May fail with -EINVAL if aio_context specified by ctx_id is
   *      invalid.  May fail with -EAGAIN if the iocb specified was not
   *      cancelled.  Will fail with -ENOSYS if not implemented.
   */
  SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
                  struct io_event __user *, result)
  {
          int (*cancel)(struct kiocb *iocb, struct io_event *res);
          struct kioctx *ctx;
          struct kiocb *kiocb;
          u32 key;
          int ret;
  
          ret = get_user(key, &iocb->aio_key);
          if (unlikely(ret))
                  return -EFAULT;
  
          ctx = lookup_ioctx(ctx_id);
          if (unlikely(!ctx))
                  return -EINVAL;
  
          spin_lock_irq(&ctx->ctx_lock);
          ret = -EAGAIN;
          kiocb = lookup_kiocb(ctx, iocb, key);
          if (kiocb && kiocb->ki_cancel) {
                  cancel = kiocb->ki_cancel;
                  kiocb->ki_users ++;
                  kiocbSetCancelled(kiocb);
          } else
                  cancel = NULL;
          spin_unlock_irq(&ctx->ctx_lock);
  
          if (NULL != cancel) {
                  struct io_event tmp;
                  pr_debug("calling cancel\n");
                  memset(&tmp, 0, sizeof(tmp));
                  tmp.obj = (u64)(unsigned long)kiocb->ki_obj.user;
                  tmp.data = kiocb->ki_user_data;
                  ret = cancel(kiocb, &tmp);
                  if (!ret) {
                          /* Cancellation succeeded -- copy the result
                           * into the user's buffer.
                           */
                          if (copy_to_user(result, &tmp, sizeof(tmp)))
                                  ret = -EFAULT;
                  }
          } else
                  ret = -EINVAL;
  
          put_ioctx(ctx);
  
          return ret;
  }
  
  /* io_getevents:
   *      Attempts to read at least min_nr events and up to nr events from
   *      the completion queue for the aio_context specified by ctx_id. If
   *      it succeeds, the number of read events is returned. May fail with
   *      -EINVAL if ctx_id is invalid, if min_nr is out of range, if nr is
   *      out of range, if timeout is out of range.  May fail with -EFAULT
   *      if any of the memory specified is invalid.  May return 0 or
   *      < min_nr if the timeout specified by timeout has elapsed
   *      before sufficient events are available, where timeout == NULL
   *      specifies an infinite timeout. Note that the timeout pointed to by
   *      timeout is relative and will be updated if not NULL and the
   *      operation blocks. Will fail with -ENOSYS if not implemented.
   */
  SYSCALL_DEFINE5(io_getevents, aio_context_t, ctx_id,
                  long, min_nr,
                  long, nr,
                  struct io_event __user *, events,
                  struct timespec __user *, timeout)
  {
          struct kioctx *ioctx = lookup_ioctx(ctx_id);
          long ret = -EINVAL;
  
          if (likely(ioctx)) {
                  if (likely(min_nr <= nr && min_nr >= 0))
                          ret = read_events(ioctx, min_nr, nr, events, timeout);
                  put_ioctx(ioctx);
          }
  
          asmlinkage_protect(5, ret, ctx_id, min_nr, nr, events, timeout);
          return ret;
  }

Cache object: a38481954339695572b18658a289df8c