Initial file dump from open source releaseHEADmaster

1 files changed, 1319 insertions, 0 deletions

diff --git a/fs/aio.c b/fs/aio.c
new file mode 100644
index 00000000..ded94c4f
--- /dev/null
+++ b/fs/aio.c
@@ -0,0 +1,1319 @@
+/*
+ *	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.
+ */
+#define pr_fmt(fmt) "%s: " fmt, __func__
+
+#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>
+
+#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>
+
+#define AIO_RING_MAGIC			0xa10a10a1
+#define AIO_RING_COMPAT_FEATURES	1
+#define AIO_RING_INCOMPAT_FEATURES	0
+struct aio_ring {
+	unsigned	id;	/* kernel internal index number */
+	unsigned	nr;	/* number of io_events */
+	unsigned	head;
+	unsigned	tail;
+
+	unsigned	magic;
+	unsigned	compat_features;
+	unsigned	incompat_features;
+	unsigned	header_length;	/* size of aio_ring */
+
+
+	struct io_event		io_events[0];
+}; /* 128 bytes + ring size */
+
+#define AIO_RING_PAGES	8
+
+struct kioctx {
+	atomic_t		users;
+	atomic_t		dead;
+
+	/* This needs improving */
+	unsigned long		user_id;
+	struct hlist_node	list;
+
+	/*
+	 * This is what userspace passed to io_setup(), it's not used for
+	 * anything but counting against the global max_reqs quota.
+	 *
+	 * The real limit is nr_events - 1, which will be larger (see
+	 * aio_setup_ring())
+	 */
+	unsigned		max_reqs;
+
+	/* Size of ringbuffer, in units of struct io_event */
+	unsigned		nr_events;
+
+	unsigned long		mmap_base;
+	unsigned long		mmap_size;
+
+	struct page		**ring_pages;
+	long			nr_pages;
+
+	struct rcu_head		rcu_head;
+	struct work_struct	rcu_work;
+
+	struct {
+		atomic_t	reqs_active;
+	} ____cacheline_aligned_in_smp;
+
+	struct {
+		spinlock_t	ctx_lock;
+		struct list_head active_reqs;	/* used for cancellation */
+	} ____cacheline_aligned_in_smp;
+
+	struct {
+		struct mutex	ring_lock;
+		wait_queue_head_t wait;
+	} ____cacheline_aligned_in_smp;
+
+	struct {
+		unsigned	tail;
+		spinlock_t	completion_lock;
+	} ____cacheline_aligned_in_smp;
+
+	struct page		*internal_pages[AIO_RING_PAGES];
+};
+
+/*------ 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;
+
+/* 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);
+
+	pr_debug("sizeof(struct page) = %zu\n", sizeof(struct page));
+
+	return 0;
+}
+__initcall(aio_setup);
+
+static void aio_free_ring(struct kioctx *ctx)
+{
+	long i;
+
+	for (i = 0; i < ctx->nr_pages; i++)
+		put_page(ctx->ring_pages[i]);
+
+	if (ctx->ring_pages && ctx->ring_pages != ctx->internal_pages)
+		kfree(ctx->ring_pages);
+}
+
+static int aio_setup_ring(struct kioctx *ctx)
+{
+	struct aio_ring *ring;
+	unsigned nr_events = ctx->max_reqs;
+	struct mm_struct *mm = current->mm;
+	unsigned long size, populate;
+	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);
+
+	ctx->nr_events = 0;
+	ctx->ring_pages = ctx->internal_pages;
+	if (nr_pages > AIO_RING_PAGES) {
+		ctx->ring_pages = kcalloc(nr_pages, sizeof(struct page *),
+					  GFP_KERNEL);
+		if (!ctx->ring_pages)
+			return -ENOMEM;
+	}
+
+	ctx->mmap_size = nr_pages * PAGE_SIZE;
+	pr_debug("attempting mmap of %lu bytes\n", ctx->mmap_size);
+	down_write(&mm->mmap_sem);
+	ctx->mmap_base = do_mmap_pgoff(NULL, 0, ctx->mmap_size,
+				       PROT_READ|PROT_WRITE,
+				       MAP_ANONYMOUS|MAP_PRIVATE, 0, &populate);
+	if (IS_ERR((void *)ctx->mmap_base)) {
+		up_write(&mm->mmap_sem);
+		ctx->mmap_size = 0;
+		aio_free_ring(ctx);
+		return -EAGAIN;
+	}
+
+	pr_debug("mmap address: 0x%08lx\n", ctx->mmap_base);
+	ctx->nr_pages = get_user_pages(current, mm, ctx->mmap_base, nr_pages,
+				       1, 0, ctx->ring_pages, NULL);
+	up_write(&mm->mmap_sem);
+
+	if (unlikely(ctx->nr_pages != nr_pages)) {
+		aio_free_ring(ctx);
+		return -EAGAIN;
+	}
+	if (populate)
+		mm_populate(ctx->mmap_base, populate);
+
+	ctx->user_id = ctx->mmap_base;
+	ctx->nr_events = nr_events; /* trusted copy */
+
+	ring = kmap_atomic(ctx->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);
+	flush_dcache_page(ctx->ring_pages[0]);
+
+	return 0;
+}
+
+#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)
+
+void kiocb_set_cancel_fn(struct kiocb *req, kiocb_cancel_fn *cancel)
+{
+	struct kioctx *ctx = req->ki_ctx;
+	unsigned long flags;
+
+	spin_lock_irqsave(&ctx->ctx_lock, flags);
+
+	if (!req->ki_list.next)
+		list_add(&req->ki_list, &ctx->active_reqs);
+
+	req->ki_cancel = cancel;
+
+	spin_unlock_irqrestore(&ctx->ctx_lock, flags);
+}
+EXPORT_SYMBOL(kiocb_set_cancel_fn);
+
+static int kiocb_cancel(struct kioctx *ctx, struct kiocb *kiocb,
+			struct io_event *res)
+{
+	kiocb_cancel_fn *old, *cancel;
+	int ret = -EINVAL;
+
+	/*
+	 * Don't want to set kiocb->ki_cancel = KIOCB_CANCELLED unless it
+	 * actually has a cancel function, hence the cmpxchg()
+	 */
+
+	cancel = ACCESS_ONCE(kiocb->ki_cancel);
+	do {
+		if (!cancel || cancel == KIOCB_CANCELLED)
+			return ret;
+
+		old = cancel;
+		cancel = cmpxchg(&kiocb->ki_cancel, old, KIOCB_CANCELLED);
+	} while (cancel != old);
+
+	atomic_inc(&kiocb->ki_users);
+	spin_unlock_irq(&ctx->ctx_lock);
+
+	memset(res, 0, sizeof(*res));
+	res->obj = (u64)(unsigned long)kiocb->ki_obj.user;
+	res->data = kiocb->ki_user_data;
+	ret = cancel(kiocb, res);
+
+	spin_lock_irq(&ctx->ctx_lock);
+
+	return ret;
+}
+
+static void free_ioctx_rcu(struct rcu_head *head)
+{
+	struct kioctx *ctx = container_of(head, struct kioctx, rcu_head);
+	kmem_cache_free(kioctx_cachep, ctx);
+}
+
+/*
+ * When this function runs, the kioctx has been removed from the "hash table"
+ * and ctx->users has dropped to 0, so we know no more kiocbs can be submitted -
+ * now it's safe to cancel any that need to be.
+ */
+static void free_ioctx(struct kioctx *ctx)
+{
+	struct aio_ring *ring;
+	struct io_event res;
+	struct kiocb *req;
+	unsigned head, avail;
+
+	spin_lock_irq(&ctx->ctx_lock);
+
+	while (!list_empty(&ctx->active_reqs)) {
+		req = list_first_entry(&ctx->active_reqs,
+				       struct kiocb, ki_list);
+
+		list_del_init(&req->ki_list);
+		kiocb_cancel(ctx, req, &res);
+	}
+
+	spin_unlock_irq(&ctx->ctx_lock);
+
+	ring = kmap_atomic(ctx->ring_pages[0]);
+	head = ring->head;
+	kunmap_atomic(ring);
+
+	while (atomic_read(&ctx->reqs_active) > 0) {
+		wait_event(ctx->wait,
+				head != ctx->tail ||
+				atomic_read(&ctx->reqs_active) <= 0);
+
+		avail = (head <= ctx->tail ? ctx->tail : ctx->nr_events) - head;
+
+		head += avail;
+		head %= ctx->nr_events;
+	}
+
+	WARN_ON(atomic_read(&ctx->reqs_active) < 0);
+
+	aio_free_ring(ctx);
+
+	pr_debug("freeing %p\n", ctx);
+
+	/*
+	 * Here the call_rcu() is between the wait_event() for reqs_active to
+	 * hit 0, and freeing the ioctx.
+	 *
+	 * aio_complete() decrements reqs_active, but it has to touch the ioctx
+	 * after to issue a wakeup so we use rcu.
+	 */
+	call_rcu(&ctx->rcu_head, free_ioctx_rcu);
+}
+
+static void put_ioctx(struct kioctx *ctx)
+{
+	if (unlikely(atomic_dec_and_test(&ctx->users)))
+		free_ioctx(ctx);
+}
+
+/* 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 = current->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;
+
+	atomic_set(&ctx->users, 2);
+	atomic_set(&ctx->dead, 0);
+	spin_lock_init(&ctx->ctx_lock);
+	spin_lock_init(&ctx->completion_lock);
+	mutex_init(&ctx->ring_lock);
+	init_waitqueue_head(&ctx->wait);
+
+	INIT_LIST_HEAD(&ctx->active_reqs);
+
+	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);
+
+	pr_debug("allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",
+		 ctx, ctx->user_id, mm, ctx->nr_events);
+	return ctx;
+
+out_cleanup:
+	err = -EAGAIN;
+	aio_free_ring(ctx);
+out_freectx:
+	kmem_cache_free(kioctx_cachep, ctx);
+	pr_debug("error allocating ioctx %d\n", err);
+	return ERR_PTR(err);
+}
+
+static void kill_ioctx_work(struct work_struct *work)
+{
+	struct kioctx *ctx = container_of(work, struct kioctx, rcu_work);
+
+	wake_up_all(&ctx->wait);
+	put_ioctx(ctx);
+}
+
+static void kill_ioctx_rcu(struct rcu_head *head)
+{
+	struct kioctx *ctx = container_of(head, struct kioctx, rcu_head);
+
+	INIT_WORK(&ctx->rcu_work, kill_ioctx_work);
+	schedule_work(&ctx->rcu_work);
+}
+
+/* kill_ioctx
+ *	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_ioctx(struct mm_struct *mm, struct kioctx *ctx)
+{
+	if (!atomic_xchg(&ctx->dead, 1)) {
+		spin_lock(&mm->ioctx_lock);
+		hlist_del_rcu(&ctx->list);
+		spin_unlock(&mm->ioctx_lock);
+
+		/*
+		 * It'd be more correct to do this in free_ioctx(), after all
+		 * the outstanding kiocbs have finished - but by then io_destroy
+		 * has already returned, so io_setup() could potentially return
+		 * -EAGAIN with no ioctxs actually in use (as far as userspace
+		 *  could tell).
+		 */
+		spin_lock(&aio_nr_lock);
+		BUG_ON(aio_nr - ctx->max_reqs > aio_nr);
+		aio_nr -= ctx->max_reqs;
+		spin_unlock(&aio_nr_lock);
+
+		if (ctx->mmap_size)
+			vm_munmap(ctx->mmap_base, ctx->mmap_size);
+
+		/* Between hlist_del_rcu() and dropping the initial ref */
+		call_rcu(&ctx->rcu_head, kill_ioctx_rcu);
+	}
+}
+
+/* wait_on_sync_kiocb:
+ *	Waits on the given sync kiocb to complete.
+ */
+ssize_t wait_on_sync_kiocb(struct kiocb *iocb)
+{
+	while (atomic_read(&iocb->ki_users)) {
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		if (!atomic_read(&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.
+ *
+ * There may be outstanding kiocbs, but free_ioctx() will explicitly wait on
+ * them.
+ */
+void exit_aio(struct mm_struct *mm)
+{
+	struct kioctx *ctx;
+	struct hlist_node *n;
+
+	hlist_for_each_entry_safe(ctx, n, &mm->ioctx_list, list) {
+		if (1 != atomic_read(&ctx->users))
+			printk(KERN_DEBUG
+				"exit_aio:ioctx still alive: %d %d %d\n",
+				atomic_read(&ctx->users),
+				atomic_read(&ctx->dead),
+				atomic_read(&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.
+		 */
+		ctx->mmap_size = 0;
+
+		kill_ioctx(mm, ctx);
+	}
+}
+
+/* aio_get_req
+ *	Allocate a slot for an aio request.  Increments the ki_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->ki_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 inline struct kiocb *aio_get_req(struct kioctx *ctx)
+{
+	struct kiocb *req;
+
+	if (atomic_read(&ctx->reqs_active) >= ctx->nr_events)
+		return NULL;
+
+	if (atomic_inc_return(&ctx->reqs_active) > ctx->nr_events - 1)
+		goto out_put;
+
+	req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL|__GFP_ZERO);
+	if (unlikely(!req))
+		goto out_put;
+
+	atomic_set(&req->ki_users, 2);
+	req->ki_ctx = ctx;
+
+	return req;
+out_put:
+	atomic_dec(&ctx->reqs_active);
+	return NULL;
+}
+
+static void kiocb_free(struct kiocb *req)
+{
+	if (req->ki_filp)
+		fput(req->ki_filp);
+	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);
+}
+
+void aio_put_req(struct kiocb *req)
+{
+	if (atomic_dec_and_test(&req->ki_users))
+		kiocb_free(req);
+}
+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;
+
+	rcu_read_lock();
+
+	hlist_for_each_entry_rcu(ctx, &mm->ioctx_list, list) {
+		if (ctx->user_id == ctx_id) {
+			atomic_inc(&ctx->users);
+			ret = ctx;
+			break;
+		}
+	}
+
+	rcu_read_unlock();
+	return ret;
+}
+
+/* aio_complete
+ *	Called when the io request on the given iocb is complete.
+ */
+void aio_complete(struct kiocb *iocb, long res, long res2)
+{
+	struct kioctx	*ctx = iocb->ki_ctx;
+	struct aio_ring	*ring;
+	struct io_event	*ev_page, *event;
+	unsigned long	flags;
+	unsigned tail, pos;
+
+	/*
+	 * 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(atomic_read(&iocb->ki_users) != 1);
+		iocb->ki_user_data = res;
+		atomic_set(&iocb->ki_users, 0);
+		wake_up_process(iocb->ki_obj.tsk);
+		return;
+	}
+
+	/*
+	 * Take rcu_read_lock() in case the kioctx is being destroyed, as we
+	 * need to issue a wakeup after decrementing reqs_active.
+	 */
+	rcu_read_lock();
+
+	if (iocb->ki_list.next) {
+		unsigned long flags;
+
+		spin_lock_irqsave(&ctx->ctx_lock, flags);
+		list_del(&iocb->ki_list);
+		spin_unlock_irqrestore(&ctx->ctx_lock, flags);
+	}
+
+	/*
+	 * cancelled requests don't get events, userland was given one
+	 * when the event got cancelled.
+	 */
+	if (unlikely(xchg(&iocb->ki_cancel,
+			  KIOCB_CANCELLED) == KIOCB_CANCELLED)) {
+		atomic_dec(&ctx->reqs_active);
+		/* Still need the wake_up in case free_ioctx is waiting */
+		goto put_rq;
+	}
+
+	/*
+	 * 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->completion_lock, flags);
+
+	tail = ctx->tail;
+	pos = tail + AIO_EVENTS_OFFSET;
+
+	if (++tail >= ctx->nr_events)
+		tail = 0;
+
+	ev_page = kmap_atomic(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
+	event = ev_page + pos % AIO_EVENTS_PER_PAGE;
+
+	event->obj = (u64)(unsigned long)iocb->ki_obj.user;
+	event->data = iocb->ki_user_data;
+	event->res = res;
+	event->res2 = res2;
+
+	kunmap_atomic(ev_page);
+	flush_dcache_page(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
+
+	pr_debug("%p[%u]: %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 */
+
+	ctx->tail = tail;
+
+	ring = kmap_atomic(ctx->ring_pages[0]);
+	ring->tail = tail;
+	kunmap_atomic(ring);
+	flush_dcache_page(ctx->ring_pages[0]);
+
+	spin_unlock_irqrestore(&ctx->completion_lock, flags);
+
+	pr_debug("added to ring %p at [%u]\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. */
+	aio_put_req(iocb);
+	atomic_dec(&ctx->reqs_active);
+
+	/*
+	 * 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);
+
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL(aio_complete);
+
+/* aio_read_events
+ *	Pull an event off of the ioctx's event ring.  Returns the number of
+ *	events fetched
+ */
+static long aio_read_events_ring(struct kioctx *ctx,
+				 struct io_event __user *event, long nr)
+{
+	struct aio_ring *ring;
+	unsigned head, pos;
+	long ret = 0;
+	int copy_ret;
+
+	mutex_lock(&ctx->ring_lock);
+
+	ring = kmap_atomic(ctx->ring_pages[0]);
+	head = ring->head;
+	kunmap_atomic(ring);
+
+	pr_debug("h%u t%u m%u\n", head, ctx->tail, ctx->nr_events);
+
+	if (head == ctx->tail)
+		goto out;
+
+	head %= ctx->nr_events;
+
+	while (ret < nr) {
+		long avail;
+		struct io_event *ev;
+		struct page *page;
+
+		avail = (head <= ctx->tail ? ctx->tail : ctx->nr_events) - head;
+		if (head == ctx->tail)
+			break;
+
+		avail = min(avail, nr - ret);
+		avail = min_t(long, avail, AIO_EVENTS_PER_PAGE -
+			    ((head + AIO_EVENTS_OFFSET) % AIO_EVENTS_PER_PAGE));
+
+		pos = head + AIO_EVENTS_OFFSET;
+		page = ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE];
+		pos %= AIO_EVENTS_PER_PAGE;
+
+		ev = kmap(page);
+		copy_ret = copy_to_user(event + ret, ev + pos,
+					sizeof(*ev) * avail);
+		kunmap(page);
+
+		if (unlikely(copy_ret)) {
+			ret = -EFAULT;
+			goto out;
+		}
+
+		ret += avail;
+		head += avail;
+		head %= ctx->nr_events;
+	}
+
+	ring = kmap_atomic(ctx->ring_pages[0]);
+	ring->head = head;
+	kunmap_atomic(ring);
+	flush_dcache_page(ctx->ring_pages[0]);
+
+	pr_debug("%li  h%u t%u\n", ret, head, ctx->tail);
+out:
+	mutex_unlock(&ctx->ring_lock);
+
+	return ret;
+}
+
+static bool aio_read_events(struct kioctx *ctx, long min_nr, long nr,
+			    struct io_event __user *event, long *i)
+{
+	long ret = aio_read_events_ring(ctx, event + *i, nr - *i);
+
+	if (ret > 0)
+		*i += ret;
+
+	if (unlikely(atomic_read(&ctx->dead)))
+		ret = -EINVAL;
+
+	if (!*i)
+		*i = ret;
+
+	return ret < 0 || *i >= min_nr;
+}
+
+static long read_events(struct kioctx *ctx, long min_nr, long nr,
+			struct io_event __user *event,
+			struct timespec __user *timeout)
+{
+	ktime_t until = { .tv64 = KTIME_MAX };
+	long ret = 0;
+
+	if (timeout) {
+		struct timespec	ts;
+
+		if (unlikely(copy_from_user(&ts, timeout, sizeof(ts))))
+			return -EFAULT;
+
+		until = timespec_to_ktime(ts);
+	}
+
+	/*
+	 * Note that aio_read_events() is being called as the conditional - i.e.
+	 * we're calling it after prepare_to_wait() has set task state to
+	 * TASK_INTERRUPTIBLE.
+	 *
+	 * But aio_read_events() can block, and if it blocks it's going to flip
+	 * the task state back to TASK_RUNNING.
+	 *
+	 * This should be ok, provided it doesn't flip the state back to
+	 * TASK_RUNNING and return 0 too much - that causes us to spin. That
+	 * will only happen if the mutex_lock() call blocks, and we then find
+	 * the ringbuffer empty. So in practice we should be ok, but it's
+	 * something to be aware of when touching this code.
+	 */
+	wait_event_interruptible_hrtimeout(ctx->wait,
+			aio_read_events(ctx, min_nr, nr, event, &ret), until);
+
+	if (!ret && signal_pending(current))
+		ret = -EINTR;
+
+	return ret;
+}
+
+/* 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)
+			kill_ioctx(current->mm, 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)) {
+		kill_ioctx(current->mm, 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);
+}
+
+typedef ssize_t (aio_rw_op)(struct kiocb *, const struct iovec *,
+			    unsigned long, loff_t);
+
+static ssize_t aio_rw_vect_retry(struct kiocb *iocb, int rw, aio_rw_op *rw_op)
+{
+	struct file *file = iocb->ki_filp;
+	struct address_space *mapping = file->f_mapping;
+	struct inode *inode = mapping->host;
+	ssize_t ret = 0;
+
+	/* This matches the pread()/pwrite() logic */
+	if (iocb->ki_pos < 0)
+		return -EINVAL;
+
+	if (rw == WRITE)
+		file_start_write(file);
+	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 &&
+		 (rw == WRITE ||
+		  (!S_ISFIFO(inode->i_mode) && !S_ISSOCK(inode->i_mode))));
+	if (rw == WRITE)
+		file_end_write(file);
+
+	/* 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 (rw == WRITE
+	    && ret < 0 && ret != -EIOCBQUEUED
+	    && iocb->ki_nbytes - iocb->ki_left)
+		ret = iocb->ki_nbytes - iocb->ki_left;
+
+	return ret;
+}
+
+static ssize_t aio_setup_vectored_rw(int rw, struct kiocb *kiocb, bool compat)
+{
+	ssize_t ret;
+
+	kiocb->ki_nr_segs = kiocb->ki_nbytes;
+
+#ifdef CONFIG_COMPAT
+	if (compat)
+		ret = compat_rw_copy_check_uvector(rw,
+				(struct compat_iovec __user *)kiocb->ki_buf,
+				kiocb->ki_nr_segs, 1, &kiocb->ki_inline_vec,
+				&kiocb->ki_iovec);
+	else
+#endif
+		ret = rw_copy_check_uvector(rw,
+				(struct iovec __user *)kiocb->ki_buf,
+				kiocb->ki_nr_segs, 1, &kiocb->ki_inline_vec,
+				&kiocb->ki_iovec);
+	if (ret < 0)
+		return ret;
+
+	/* ki_nbytes now reflect bytes instead of segs */
+	kiocb->ki_nbytes = ret;
+	return 0;
+}
+
+static ssize_t aio_setup_single_vector(int rw, struct kiocb *kiocb)
+{
+	if (unlikely(!access_ok(!rw, kiocb->ki_buf, kiocb->ki_nbytes)))
+		return -EFAULT;
+
+	kiocb->ki_iovec = &kiocb->ki_inline_vec;
+	kiocb->ki_iovec->iov_base = kiocb->ki_buf;
+	kiocb->ki_iovec->iov_len = kiocb->ki_nbytes;
+	kiocb->ki_nr_segs = 1;
+	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_run_iocb(struct kiocb *req, bool compat)
+{
+	struct file *file = req->ki_filp;
+	ssize_t ret;
+	int rw;
+	fmode_t mode;
+	aio_rw_op *rw_op;
+
+	switch (req->ki_opcode) {
+	case IOCB_CMD_PREAD:
+	case IOCB_CMD_PREADV:
+		mode	= FMODE_READ;
+		rw	= READ;
+		rw_op	= file->f_op->aio_read;
+		goto rw_common;
+
+	case IOCB_CMD_PWRITE:
+	case IOCB_CMD_PWRITEV:
+		mode	= FMODE_WRITE;
+		rw	= WRITE;
+		rw_op	= file->f_op->aio_write;
+		goto rw_common;
+rw_common:
+		if (unlikely(!(file->f_mode & mode)))
+			return -EBADF;
+
+		if (!rw_op)
+			return -EINVAL;
+
+		ret = (req->ki_opcode == IOCB_CMD_PREADV ||
+		       req->ki_opcode == IOCB_CMD_PWRITEV)
+			? aio_setup_vectored_rw(rw, req, compat)
+			: aio_setup_single_vector(rw, req);
+		if (ret)
+			return ret;
+
+		ret = rw_verify_area(rw, file, &req->ki_pos, req->ki_nbytes);
+		if (ret < 0)
+			return ret;
+
+		req->ki_nbytes = ret;
+		req->ki_left = ret;
+
+		ret = aio_rw_vect_retry(req, rw, rw_op);
+		break;
+
+	case IOCB_CMD_FDSYNC:
+		if (!file->f_op->aio_fsync)
+			return -EINVAL;
+
+		ret = file->f_op->aio_fsync(req, 1);
+		break;
+
+	case IOCB_CMD_FSYNC:
+		if (!file->f_op->aio_fsync)
+			return -EINVAL;
+
+		ret = file->f_op->aio_fsync(req, 0);
+		break;
+
+	default:
+		pr_debug("EINVAL: no operation provided\n");
+		return -EINVAL;
+	}
+
+	if (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(req, ret, 0);
+	}
+
+	return 0;
+}
+
+static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
+			 struct iocb *iocb, bool compat)
+{
+	struct kiocb *req;
+	ssize_t ret;
+
+	/* enforce forwards compatibility on users */
+	if (unlikely(iocb->aio_reserved1 || iocb->aio_reserved2)) {
+		pr_debug("EINVAL: 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;
+	}
+
+	req = aio_get_req(ctx);
+	if (unlikely(!req))
+		return -EAGAIN;
+
+	req->ki_filp = fget(iocb->aio_fildes);
+	if (unlikely(!req->ki_filp)) {
+		ret = -EBADF;
+		goto out_put_req;
+	}
+
+	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(KIOCB_KEY, &user_iocb->aio_key);
+	if (unlikely(ret)) {
+		pr_debug("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_run_iocb(req, compat);
+	if (ret)
+		goto out_put_req;
+
+	aio_put_req(req);	/* drop extra ref to req */
+	return 0;
+out_put_req:
+	atomic_dec(&ctx->reqs_active);
+	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;
+
+	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: invalid context id\n");
+		return -EINVAL;
+	}
+
+	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, compat);
+		if (ret)
+			break;
+	}
+	blk_finish_plug(&plug);
+
+	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);
+
+	if (key != KIOCB_KEY)
+		return NULL;
+
+	/* 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)
+			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)
+{
+	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);
+
+	kiocb = lookup_kiocb(ctx, iocb, key);
+	if (kiocb)
+		ret = kiocb_cancel(ctx, kiocb, &res);
+	else
+		ret = -EINVAL;
+
+	spin_unlock_irq(&ctx->ctx_lock);
+
+	if (!ret) {
+		/* Cancellation succeeded -- copy the result
+		 * into the user's buffer.
+		 */
+		if (copy_to_user(result, &res, sizeof(res)))
+			ret = -EFAULT;
+	}
+
+	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.  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);
+	}
+	return ret;
+}