Merge tag 'io_uring-2019-03-06' of git://git.kernel.dk/linux-block

Pull io_uring IO interface from Jens Axboe:
 "Second attempt at adding the io_uring interface.

  Since the first one, we've added basic unit testing of the three
  system calls, that resides in liburing like the other unit tests that
  we have so far. It'll take a while to get full coverage of it, but
  we're working towards it. I've also added two basic test programs to
  tools/io_uring. One uses the raw interface and has support for all the
  various features that io_uring supports outside of standard IO, like
  fixed files, fixed IO buffers, and polled IO. The other uses the
  liburing API, and is a simplified version of cp(1).

  This adds support for a new IO interface, io_uring.

  io_uring allows an application to communicate with the kernel through
  two rings, the submission queue (SQ) and completion queue (CQ) ring.
  This allows for very efficient handling of IOs, see the v5 posting for
  some basic numbers:

    https://lore.kernel.org/linux-block/20190116175003.17880-1-axboe@kernel.dk/

  Outside of just efficiency, the interface is also flexible and
  extendable, and allows for future use cases like the upcoming NVMe
  key-value store API, networked IO, and so on. It also supports async
  buffered IO, something that we've always failed to support in the
  kernel.

  Outside of basic IO features, it supports async polled IO as well.
  This particular feature has already been tested at Facebook months ago
  for flash storage boxes, with 25-33% improvements. It makes polled IO
  actually useful for real world use cases, where even basic flash sees
  a nice win in terms of efficiency, latency, and performance. These
  boxes were IOPS bound before, now they are not.

  This series adds three new system calls. One for setting up an
  io_uring instance (io_uring_setup(2)), one for submitting/completing
  IO (io_uring_enter(2)), and one for aux functions like registrating
  file sets, buffers, etc (io_uring_register(2)). Through the help of
  Arnd, I've coordinated the syscall numbers so merge on that front
  should be painless.

  Jon did a writeup of the interface a while back, which (except for
  minor details that have been tweaked) is still accurate. Find that
  here:

    https://lwn.net/Articles/776703/

  Huge thanks to Al Viro for helping getting the reference cycle code
  correct, and to Jann Horn for his extensive reviews focused on both
  security and bugs in general.

  There's a userspace library that provides basic functionality for
  applications that don't need or want to care about how to fiddle with
  the rings directly. It has helpers to allow applications to easily set
  up an io_uring instance, and submit/complete IO through it without
  knowing about the intricacies of the rings. It also includes man pages
  (thanks to Jeff Moyer), and will continue to grow support helper
  functions and features as time progresses. Find it here:

    git://git.kernel.dk/liburing

  Fio has full support for the raw interface, both in the form of an IO
  engine (io_uring), but also with a small test application (t/io_uring)
  that can exercise and benchmark the interface"

* tag 'io_uring-2019-03-06' of git://git.kernel.dk/linux-block:
  io_uring: add a few test tools
  io_uring: allow workqueue item to handle multiple buffered requests
  io_uring: add support for IORING_OP_POLL
  io_uring: add io_kiocb ref count
  io_uring: add submission polling
  io_uring: add file set registration
  net: split out functions related to registering inflight socket files
  io_uring: add support for pre-mapped user IO buffers
  block: implement bio helper to add iter bvec pages to bio
  io_uring: batch io_kiocb allocation
  io_uring: use fget/fput_many() for file references
  fs: add fget_many() and fput_many()
  io_uring: support for IO polling
  io_uring: add fsync support
  Add io_uring IO interface

4 files changed, 2989 insertions, 7 deletions

diff --git a/fs/Makefile b/fs/Makefile
index 23fcd8c164a3..ffeaa6632ab4 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -31,6 +31,7 @@ obj-$(CONFIG_TIMERFD)		+= timerfd.o
 obj-$(CONFIG_EVENTFD)		+= eventfd.o
 obj-$(CONFIG_USERFAULTFD)	+= userfaultfd.o
 obj-$(CONFIG_AIO)               += aio.o
+obj-$(CONFIG_IO_URING)		+= io_uring.o
 obj-$(CONFIG_FS_DAX)		+= dax.o
 obj-$(CONFIG_FS_ENCRYPTION)	+= crypto/
 obj-$(CONFIG_FILE_LOCKING)      += locks.o
diff --git a/fs/file.c b/fs/file.c
index a10487aa0a84..3da91a112bab 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -706,7 +706,7 @@ void do_close_on_exec(struct files_struct *files)
 	spin_unlock(&files->file_lock);
 }
 
-static struct file *__fget(unsigned int fd, fmode_t mask)
+static struct file *__fget(unsigned int fd, fmode_t mask, unsigned int refs)
 {
 	struct files_struct *files = current->files;
 	struct file *file;
@@ -721,7 +721,7 @@ loop:
 		 */
 		if (file->f_mode & mask)
 			file = NULL;
-		else if (!get_file_rcu(file))
+		else if (!get_file_rcu_many(file, refs))
 			goto loop;
 	}
 	rcu_read_unlock();
@@ -729,15 +729,20 @@ loop:
 	return file;
 }
 
+struct file *fget_many(unsigned int fd, unsigned int refs)
+{
+	return __fget(fd, FMODE_PATH, refs);
+}
+
 struct file *fget(unsigned int fd)
 {
-	return __fget(fd, FMODE_PATH);
+	return __fget(fd, FMODE_PATH, 1);
 }
 EXPORT_SYMBOL(fget);
 
 struct file *fget_raw(unsigned int fd)
 {
-	return __fget(fd, 0);
+	return __fget(fd, 0, 1);
 }
 EXPORT_SYMBOL(fget_raw);
 
@@ -768,7 +773,7 @@ static unsigned long __fget_light(unsigned int fd, fmode_t mask)
 			return 0;
 		return (unsigned long)file;
 	} else {
-		file = __fget(fd, mask);
+		file = __fget(fd, mask, 1);
 		if (!file)
 			return 0;
 		return FDPUT_FPUT | (unsigned long)file;
diff --git a/fs/file_table.c b/fs/file_table.c
index 5679e7fcb6b0..155d7514a094 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -326,9 +326,9 @@ void flush_delayed_fput(void)
 
 static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput);
 
-void fput(struct file *file)
+void fput_many(struct file *file, unsigned int refs)
 {
-	if (atomic_long_dec_and_test(&file->f_count)) {
+	if (atomic_long_sub_and_test(refs, &file->f_count)) {
 		struct task_struct *task = current;
 
 		if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
@@ -347,6 +347,11 @@ void fput(struct file *file)
 	}
 }
 
+void fput(struct file *file)
+{
+	fput_many(file, 1);
+}
+
 /*
  * synchronous analog of fput(); for kernel threads that might be needed
  * in some umount() (and thus can't use flush_delayed_fput() without
diff --git a/fs/io_uring.c b/fs/io_uring.c
new file mode 100644
index 000000000000..5d99376d2369
--- /dev/null
+++ b/fs/io_uring.c
@@ -0,0 +1,2971 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Shared application/kernel submission and completion ring pairs, for
+ * supporting fast/efficient IO.
+ *
+ * A note on the read/write ordering memory barriers that are matched between
+ * the application and kernel side. When the application reads the CQ ring
+ * tail, it must use an appropriate smp_rmb() to order with the smp_wmb()
+ * the kernel uses after writing the tail. Failure to do so could cause a
+ * delay in when the application notices that completion events available.
+ * This isn't a fatal condition. Likewise, the application must use an
+ * appropriate smp_wmb() both before writing the SQ tail, and after writing
+ * the SQ tail. The first one orders the sqe writes with the tail write, and
+ * the latter is paired with the smp_rmb() the kernel will issue before
+ * reading the SQ tail on submission.
+ *
+ * Also see the examples in the liburing library:
+ *
+ *	git://git.kernel.dk/liburing
+ *
+ * io_uring also uses READ/WRITE_ONCE() for _any_ store or load that happens
+ * from data shared between the kernel and application. This is done both
+ * for ordering purposes, but also to ensure that once a value is loaded from
+ * data that the application could potentially modify, it remains stable.
+ *
+ * Copyright (C) 2018-2019 Jens Axboe
+ * Copyright (c) 2018-2019 Christoph Hellwig
+ */
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/errno.h>
+#include <linux/syscalls.h>
+#include <linux/compat.h>
+#include <linux/refcount.h>
+#include <linux/uio.h>
+
+#include <linux/sched/signal.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/fdtable.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/mmu_context.h>
+#include <linux/percpu.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+#include <linux/kthread.h>
+#include <linux/blkdev.h>
+#include <linux/bvec.h>
+#include <linux/net.h>
+#include <net/sock.h>
+#include <net/af_unix.h>
+#include <net/scm.h>
+#include <linux/anon_inodes.h>
+#include <linux/sched/mm.h>
+#include <linux/uaccess.h>
+#include <linux/nospec.h>
+#include <linux/sizes.h>
+#include <linux/hugetlb.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "internal.h"
+
+#define IORING_MAX_ENTRIES	4096
+#define IORING_MAX_FIXED_FILES	1024
+
+struct io_uring {
+	u32 head ____cacheline_aligned_in_smp;
+	u32 tail ____cacheline_aligned_in_smp;
+};
+
+struct io_sq_ring {
+	struct io_uring		r;
+	u32			ring_mask;
+	u32			ring_entries;
+	u32			dropped;
+	u32			flags;
+	u32			array[];
+};
+
+struct io_cq_ring {
+	struct io_uring		r;
+	u32			ring_mask;
+	u32			ring_entries;
+	u32			overflow;
+	struct io_uring_cqe	cqes[];
+};
+
+struct io_mapped_ubuf {
+	u64		ubuf;
+	size_t		len;
+	struct		bio_vec *bvec;
+	unsigned int	nr_bvecs;
+};
+
+struct async_list {
+	spinlock_t		lock;
+	atomic_t		cnt;
+	struct list_head	list;
+
+	struct file		*file;
+	off_t			io_end;
+	size_t			io_pages;
+};
+
+struct io_ring_ctx {
+	struct {
+		struct percpu_ref	refs;
+	} ____cacheline_aligned_in_smp;
+
+	struct {
+		unsigned int		flags;
+		bool			compat;
+		bool			account_mem;
+
+		/* SQ ring */
+		struct io_sq_ring	*sq_ring;
+		unsigned		cached_sq_head;
+		unsigned		sq_entries;
+		unsigned		sq_mask;
+		unsigned		sq_thread_idle;
+		struct io_uring_sqe	*sq_sqes;
+	} ____cacheline_aligned_in_smp;
+
+	/* IO offload */
+	struct workqueue_struct	*sqo_wq;
+	struct task_struct	*sqo_thread;	/* if using sq thread polling */
+	struct mm_struct	*sqo_mm;
+	wait_queue_head_t	sqo_wait;
+	unsigned		sqo_stop;
+
+	struct {
+		/* CQ ring */
+		struct io_cq_ring	*cq_ring;
+		unsigned		cached_cq_tail;
+		unsigned		cq_entries;
+		unsigned		cq_mask;
+		struct wait_queue_head	cq_wait;
+		struct fasync_struct	*cq_fasync;
+	} ____cacheline_aligned_in_smp;
+
+	/*
+	 * If used, fixed file set. Writers must ensure that ->refs is dead,
+	 * readers must ensure that ->refs is alive as long as the file* is
+	 * used. Only updated through io_uring_register(2).
+	 */
+	struct file		**user_files;
+	unsigned		nr_user_files;
+
+	/* if used, fixed mapped user buffers */
+	unsigned		nr_user_bufs;
+	struct io_mapped_ubuf	*user_bufs;
+
+	struct user_struct	*user;
+
+	struct completion	ctx_done;
+
+	struct {
+		struct mutex		uring_lock;
+		wait_queue_head_t	wait;
+	} ____cacheline_aligned_in_smp;
+
+	struct {
+		spinlock_t		completion_lock;
+		bool			poll_multi_file;
+		/*
+		 * ->poll_list is protected by the ctx->uring_lock for
+		 * io_uring instances that don't use IORING_SETUP_SQPOLL.
+		 * For SQPOLL, only the single threaded io_sq_thread() will
+		 * manipulate the list, hence no extra locking is needed there.
+		 */
+		struct list_head	poll_list;
+		struct list_head	cancel_list;
+	} ____cacheline_aligned_in_smp;
+
+	struct async_list	pending_async[2];
+
+#if defined(CONFIG_UNIX)
+	struct socket		*ring_sock;
+#endif
+};
+
+struct sqe_submit {
+	const struct io_uring_sqe	*sqe;
+	unsigned short			index;
+	bool				has_user;
+	bool				needs_lock;
+	bool				needs_fixed_file;
+};
+
+struct io_poll_iocb {
+	struct file			*file;
+	struct wait_queue_head		*head;
+	__poll_t			events;
+	bool				woken;
+	bool				canceled;
+	struct wait_queue_entry		wait;
+};
+
+struct io_kiocb {
+	union {
+		struct kiocb		rw;
+		struct io_poll_iocb	poll;
+	};
+
+	struct sqe_submit	submit;
+
+	struct io_ring_ctx	*ctx;
+	struct list_head	list;
+	unsigned int		flags;
+	refcount_t		refs;
+#define REQ_F_FORCE_NONBLOCK	1	/* inline submission attempt */
+#define REQ_F_IOPOLL_COMPLETED	2	/* polled IO has completed */
+#define REQ_F_FIXED_FILE	4	/* ctx owns file */
+#define REQ_F_SEQ_PREV		8	/* sequential with previous */
+	u64			user_data;
+	u64			error;
+
+	struct work_struct	work;
+};
+
+#define IO_PLUG_THRESHOLD		2
+#define IO_IOPOLL_BATCH			8
+
+struct io_submit_state {
+	struct blk_plug		plug;
+
+	/*
+	 * io_kiocb alloc cache
+	 */
+	void			*reqs[IO_IOPOLL_BATCH];
+	unsigned		int free_reqs;
+	unsigned		int cur_req;
+
+	/*
+	 * File reference cache
+	 */
+	struct file		*file;
+	unsigned int		fd;
+	unsigned int		has_refs;
+	unsigned int		used_refs;
+	unsigned int		ios_left;
+};
+
+static struct kmem_cache *req_cachep;
+
+static const struct file_operations io_uring_fops;
+
+struct sock *io_uring_get_socket(struct file *file)
+{
+#if defined(CONFIG_UNIX)
+	if (file->f_op == &io_uring_fops) {
+		struct io_ring_ctx *ctx = file->private_data;
+
+		return ctx->ring_sock->sk;
+	}
+#endif
+	return NULL;
+}
+EXPORT_SYMBOL(io_uring_get_socket);
+
+static void io_ring_ctx_ref_free(struct percpu_ref *ref)
+{
+	struct io_ring_ctx *ctx = container_of(ref, struct io_ring_ctx, refs);
+
+	complete(&ctx->ctx_done);
+}
+
+static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
+{
+	struct io_ring_ctx *ctx;
+	int i;
+
+	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return NULL;
+
+	if (percpu_ref_init(&ctx->refs, io_ring_ctx_ref_free, 0, GFP_KERNEL)) {
+		kfree(ctx);
+		return NULL;
+	}
+
+	ctx->flags = p->flags;
+	init_waitqueue_head(&ctx->cq_wait);
+	init_completion(&ctx->ctx_done);
+	mutex_init(&ctx->uring_lock);
+	init_waitqueue_head(&ctx->wait);
+	for (i = 0; i < ARRAY_SIZE(ctx->pending_async); i++) {
+		spin_lock_init(&ctx->pending_async[i].lock);
+		INIT_LIST_HEAD(&ctx->pending_async[i].list);
+		atomic_set(&ctx->pending_async[i].cnt, 0);
+	}
+	spin_lock_init(&ctx->completion_lock);
+	INIT_LIST_HEAD(&ctx->poll_list);
+	INIT_LIST_HEAD(&ctx->cancel_list);
+	return ctx;
+}
+
+static void io_commit_cqring(struct io_ring_ctx *ctx)
+{
+	struct io_cq_ring *ring = ctx->cq_ring;
+
+	if (ctx->cached_cq_tail != READ_ONCE(ring->r.tail)) {
+		/* order cqe stores with ring update */
+		smp_store_release(&ring->r.tail, ctx->cached_cq_tail);
+
+		/*
+		 * Write sider barrier of tail update, app has read side. See
+		 * comment at the top of this file.
+		 */
+		smp_wmb();
+
+		if (wq_has_sleeper(&ctx->cq_wait)) {
+			wake_up_interruptible(&ctx->cq_wait);
+			kill_fasync(&ctx->cq_fasync, SIGIO, POLL_IN);
+		}
+	}
+}
+
+static struct io_uring_cqe *io_get_cqring(struct io_ring_ctx *ctx)
+{
+	struct io_cq_ring *ring = ctx->cq_ring;
+	unsigned tail;
+
+	tail = ctx->cached_cq_tail;
+	/* See comment at the top of the file */
+	smp_rmb();
+	if (tail + 1 == READ_ONCE(ring->r.head))
+		return NULL;
+
+	ctx->cached_cq_tail++;
+	return &ring->cqes[tail & ctx->cq_mask];
+}
+
+static void io_cqring_fill_event(struct io_ring_ctx *ctx, u64 ki_user_data,
+				 long res, unsigned ev_flags)
+{
+	struct io_uring_cqe *cqe;
+
+	/*
+	 * If we can't get a cq entry, userspace overflowed the
+	 * submission (by quite a lot). Increment the overflow count in
+	 * the ring.
+	 */
+	cqe = io_get_cqring(ctx);
+	if (cqe) {
+		WRITE_ONCE(cqe->user_data, ki_user_data);
+		WRITE_ONCE(cqe->res, res);
+		WRITE_ONCE(cqe->flags, ev_flags);
+	} else {
+		unsigned overflow = READ_ONCE(ctx->cq_ring->overflow);
+
+		WRITE_ONCE(ctx->cq_ring->overflow, overflow + 1);
+	}
+}
+
+static void io_cqring_add_event(struct io_ring_ctx *ctx, u64 ki_user_data,
+				long res, unsigned ev_flags)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&ctx->completion_lock, flags);
+	io_cqring_fill_event(ctx, ki_user_data, res, ev_flags);
+	io_commit_cqring(ctx);
+	spin_unlock_irqrestore(&ctx->completion_lock, flags);
+
+	if (waitqueue_active(&ctx->wait))
+		wake_up(&ctx->wait);
+	if (waitqueue_active(&ctx->sqo_wait))
+		wake_up(&ctx->sqo_wait);
+}
+
+static void io_ring_drop_ctx_refs(struct io_ring_ctx *ctx, unsigned refs)
+{
+	percpu_ref_put_many(&ctx->refs, refs);
+
+	if (waitqueue_active(&ctx->wait))
+		wake_up(&ctx->wait);
+}
+
+static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx,
+				   struct io_submit_state *state)
+{
+	struct io_kiocb *req;
+
+	if (!percpu_ref_tryget(&ctx->refs))
+		return NULL;
+
+	if (!state) {
+		req = kmem_cache_alloc(req_cachep, __GFP_NOWARN);
+		if (unlikely(!req))
+			goto out;
+	} else if (!state->free_reqs) {
+		size_t sz;
+		int ret;
+
+		sz = min_t(size_t, state->ios_left, ARRAY_SIZE(state->reqs));
+		ret = kmem_cache_alloc_bulk(req_cachep, __GFP_NOWARN, sz,
+						state->reqs);
+		if (unlikely(ret <= 0))
+			goto out;
+		state->free_reqs = ret - 1;
+		state->cur_req = 1;
+		req = state->reqs[0];
+	} else {
+		req = state->reqs[state->cur_req];
+		state->free_reqs--;
+		state->cur_req++;
+	}
+
+	req->ctx = ctx;
+	req->flags = 0;
+	refcount_set(&req->refs, 0);
+	return req;
+out:
+	io_ring_drop_ctx_refs(ctx, 1);
+	return NULL;
+}
+
+static void io_free_req_many(struct io_ring_ctx *ctx, void **reqs, int *nr)
+{
+	if (*nr) {
+		kmem_cache_free_bulk(req_cachep, *nr, reqs);
+		io_ring_drop_ctx_refs(ctx, *nr);
+		*nr = 0;
+	}
+}
+
+static void io_free_req(struct io_kiocb *req)
+{
+	if (!refcount_read(&req->refs) || refcount_dec_and_test(&req->refs)) {
+		io_ring_drop_ctx_refs(req->ctx, 1);
+		kmem_cache_free(req_cachep, req);
+	}
+}
+
+/*
+ * Find and free completed poll iocbs
+ */
+static void io_iopoll_complete(struct io_ring_ctx *ctx, unsigned int *nr_events,
+			       struct list_head *done)
+{
+	void *reqs[IO_IOPOLL_BATCH];
+	int file_count, to_free;
+	struct file *file = NULL;
+	struct io_kiocb *req;
+
+	file_count = to_free = 0;
+	while (!list_empty(done)) {
+		req = list_first_entry(done, struct io_kiocb, list);
+		list_del(&req->list);
+
+		io_cqring_fill_event(ctx, req->user_data, req->error, 0);
+
+		reqs[to_free++] = req;
+		(*nr_events)++;
+
+		/*
+		 * Batched puts of the same file, to avoid dirtying the
+		 * file usage count multiple times, if avoidable.
+		 */
+		if (!(req->flags & REQ_F_FIXED_FILE)) {
+			if (!file) {
+				file = req->rw.ki_filp;
+				file_count = 1;
+			} else if (file == req->rw.ki_filp) {
+				file_count++;
+			} else {
+				fput_many(file, file_count);
+				file = req->rw.ki_filp;
+				file_count = 1;
+			}
+		}
+
+		if (to_free == ARRAY_SIZE(reqs))
+			io_free_req_many(ctx, reqs, &to_free);
+	}
+	io_commit_cqring(ctx);
+
+	if (file)
+		fput_many(file, file_count);
+	io_free_req_many(ctx, reqs, &to_free);
+}
+
+static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events,
+			long min)
+{
+	struct io_kiocb *req, *tmp;
+	LIST_HEAD(done);
+	bool spin;
+	int ret;
+
+	/*
+	 * Only spin for completions if we don't have multiple devices hanging
+	 * off our complete list, and we're under the requested amount.
+	 */
+	spin = !ctx->poll_multi_file && *nr_events < min;
+
+	ret = 0;
+	list_for_each_entry_safe(req, tmp, &ctx->poll_list, list) {
+		struct kiocb *kiocb = &req->rw;
+
+		/*
+		 * Move completed entries to our local list. If we find a
+		 * request that requires polling, break out and complete
+		 * the done list first, if we have entries there.
+		 */
+		if (req->flags & REQ_F_IOPOLL_COMPLETED) {
+			list_move_tail(&req->list, &done);
+			continue;
+		}
+		if (!list_empty(&done))
+			break;
+
+		ret = kiocb->ki_filp->f_op->iopoll(kiocb, spin);
+		if (ret < 0)
+			break;
+
+		if (ret && spin)
+			spin = false;
+		ret = 0;
+	}
+
+	if (!list_empty(&done))
+		io_iopoll_complete(ctx, nr_events, &done);
+
+	return ret;
+}
+
+/*
+ * Poll for a mininum of 'min' events. Note that if min == 0 we consider that a
+ * non-spinning poll check - we'll still enter the driver poll loop, but only
+ * as a non-spinning completion check.
+ */
+static int io_iopoll_getevents(struct io_ring_ctx *ctx, unsigned int *nr_events,
+				long min)
+{
+	while (!list_empty(&ctx->poll_list)) {
+		int ret;
+
+		ret = io_do_iopoll(ctx, nr_events, min);
+		if (ret < 0)
+			return ret;
+		if (!min || *nr_events >= min)
+			return 0;
+	}
+
+	return 1;
+}
+
+/*
+ * We can't just wait for polled events to come to us, we have to actively
+ * find and complete them.
+ */
+static void io_iopoll_reap_events(struct io_ring_ctx *ctx)
+{
+	if (!(ctx->flags & IORING_SETUP_IOPOLL))
+		return;
+
+	mutex_lock(&ctx->uring_lock);
+	while (!list_empty(&ctx->poll_list)) {
+		unsigned int nr_events = 0;
+
+		io_iopoll_getevents(ctx, &nr_events, 1);
+	}
+	mutex_unlock(&ctx->uring_lock);
+}
+
+static int io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events,
+			   long min)
+{
+	int ret = 0;
+
+	do {
+		int tmin = 0;
+
+		if (*nr_events < min)
+			tmin = min - *nr_events;
+
+		ret = io_iopoll_getevents(ctx, nr_events, tmin);
+		if (ret <= 0)
+			break;
+		ret = 0;
+	} while (min && !*nr_events && !need_resched());
+
+	return ret;
+}
+
+static void kiocb_end_write(struct kiocb *kiocb)
+{
+	if (kiocb->ki_flags & IOCB_WRITE) {
+		struct inode *inode = file_inode(kiocb->ki_filp);
+
+		/*
+		 * Tell lockdep we inherited freeze protection from submission
+		 * thread.
+		 */
+		if (S_ISREG(inode->i_mode))
+			__sb_writers_acquired(inode->i_sb, SB_FREEZE_WRITE);
+		file_end_write(kiocb->ki_filp);
+	}
+}
+
+static void io_fput(struct io_kiocb *req)
+{
+	if (!(req->flags & REQ_F_FIXED_FILE))
+		fput(req->rw.ki_filp);
+}
+
+static void io_complete_rw(struct kiocb *kiocb, long res, long res2)
+{
+	struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw);
+
+	kiocb_end_write(kiocb);
+
+	io_fput(req);
+	io_cqring_add_event(req->ctx, req->user_data, res, 0);
+	io_free_req(req);
+}
+
+static void io_complete_rw_iopoll(struct kiocb *kiocb, long res, long res2)
+{
+	struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw);
+
+	kiocb_end_write(kiocb);
+
+	req->error = res;
+	if (res != -EAGAIN)
+		req->flags |= REQ_F_IOPOLL_COMPLETED;
+}
+
+/*
+ * After the iocb has been issued, it's safe to be found on the poll list.
+ * Adding the kiocb to the list AFTER submission ensures that we don't
+ * find it from a io_iopoll_getevents() thread before the issuer is done
+ * accessing the kiocb cookie.
+ */
+static void io_iopoll_req_issued(struct io_kiocb *req)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+
+	/*
+	 * Track whether we have multiple files in our lists. This will impact
+	 * how we do polling eventually, not spinning if we're on potentially
+	 * different devices.
+	 */
+	if (list_empty(&ctx->poll_list)) {
+		ctx->poll_multi_file = false;
+	} else if (!ctx->poll_multi_file) {
+		struct io_kiocb *list_req;
+
+		list_req = list_first_entry(&ctx->poll_list, struct io_kiocb,
+						list);
+		if (list_req->rw.ki_filp != req->rw.ki_filp)
+			ctx->poll_multi_file = true;
+	}
+
+	/*
+	 * For fast devices, IO may have already completed. If it has, add
+	 * it to the front so we find it first.
+	 */
+	if (req->flags & REQ_F_IOPOLL_COMPLETED)
+		list_add(&req->list, &ctx->poll_list);
+	else
+		list_add_tail(&req->list, &ctx->poll_list);
+}
+
+static void io_file_put(struct io_submit_state *state, struct file *file)
+{
+	if (!state) {
+		fput(file);
+	} else if (state->file) {
+		int diff = state->has_refs - state->used_refs;
+
+		if (diff)
+			fput_many(state->file, diff);
+		state->file = NULL;
+	}
+}
+
+/*
+ * Get as many references to a file as we have IOs left in this submission,
+ * assuming most submissions are for one file, or at least that each file
+ * has more than one submission.
+ */
+static struct file *io_file_get(struct io_submit_state *state, int fd)
+{
+	if (!state)
+		return fget(fd);
+
+	if (state->file) {
+		if (state->fd == fd) {
+			state->used_refs++;
+			state->ios_left--;
+			return state->file;
+		}
+		io_file_put(state, NULL);
+	}
+	state->file = fget_many(fd, state->ios_left);
+	if (!state->file)
+		return NULL;
+
+	state->fd = fd;
+	state->has_refs = state->ios_left;
+	state->used_refs = 1;
+	state->ios_left--;
+	return state->file;
+}
+
+/*
+ * If we tracked the file through the SCM inflight mechanism, we could support
+ * any file. For now, just ensure that anything potentially problematic is done
+ * inline.
+ */
+static bool io_file_supports_async(struct file *file)
+{
+	umode_t mode = file_inode(file)->i_mode;
+
+	if (S_ISBLK(mode) || S_ISCHR(mode))
+		return true;
+	if (S_ISREG(mode) && file->f_op != &io_uring_fops)
+		return true;
+
+	return false;
+}
+
+static int io_prep_rw(struct io_kiocb *req, const struct sqe_submit *s,
+		      bool force_nonblock, struct io_submit_state *state)
+{
+	const struct io_uring_sqe *sqe = s->sqe;
+	struct io_ring_ctx *ctx = req->ctx;
+	struct kiocb *kiocb = &req->rw;
+	unsigned ioprio, flags;
+	int fd, ret;
+
+	/* For -EAGAIN retry, everything is already prepped */
+	if (kiocb->ki_filp)
+		return 0;
+
+	flags = READ_ONCE(sqe->flags);
+	fd = READ_ONCE(sqe->fd);
+
+	if (flags & IOSQE_FIXED_FILE) {
+		if (unlikely(!ctx->user_files ||
+		    (unsigned) fd >= ctx->nr_user_files))
+			return -EBADF;
+		kiocb->ki_filp = ctx->user_files[fd];
+		req->flags |= REQ_F_FIXED_FILE;
+	} else {
+		if (s->needs_fixed_file)
+			return -EBADF;
+		kiocb->ki_filp = io_file_get(state, fd);
+		if (unlikely(!kiocb->ki_filp))
+			return -EBADF;
+		if (force_nonblock && !io_file_supports_async(kiocb->ki_filp))
+			force_nonblock = false;
+	}
+	kiocb->ki_pos = READ_ONCE(sqe->off);
+	kiocb->ki_flags = iocb_flags(kiocb->ki_filp);
+	kiocb->ki_hint = ki_hint_validate(file_write_hint(kiocb->ki_filp));
+
+	ioprio = READ_ONCE(sqe->ioprio);
+	if (ioprio) {
+		ret = ioprio_check_cap(ioprio);
+		if (ret)
+			goto out_fput;
+
+		kiocb->ki_ioprio = ioprio;
+	} else
+		kiocb->ki_ioprio = get_current_ioprio();
+
+	ret = kiocb_set_rw_flags(kiocb, READ_ONCE(sqe->rw_flags));
+	if (unlikely(ret))
+		goto out_fput;
+	if (force_nonblock) {
+		kiocb->ki_flags |= IOCB_NOWAIT;
+		req->flags |= REQ_F_FORCE_NONBLOCK;
+	}
+	if (ctx->flags & IORING_SETUP_IOPOLL) {
+		ret = -EOPNOTSUPP;
+		if (!(kiocb->ki_flags & IOCB_DIRECT) ||
+		    !kiocb->ki_filp->f_op->iopoll)
+			goto out_fput;
+
+		req->error = 0;
+		kiocb->ki_flags |= IOCB_HIPRI;
+		kiocb->ki_complete = io_complete_rw_iopoll;
+	} else {
+		if (kiocb->ki_flags & IOCB_HIPRI) {
+			ret = -EINVAL;
+			goto out_fput;
+		}
+		kiocb->ki_complete = io_complete_rw;
+	}
+	return 0;
+out_fput:
+	if (!(flags & IOSQE_FIXED_FILE)) {
+		/*
+		 * in case of error, we didn't use this file reference. drop it.
+		 */
+		if (state)
+			state->used_refs--;
+		io_file_put(state, kiocb->ki_filp);
+	}
+	return ret;
+}
+
+static inline void io_rw_done(struct kiocb *kiocb, ssize_t ret)
+{
+	switch (ret) {
+	case -EIOCBQUEUED:
+		break;
+	case -ERESTARTSYS:
+	case -ERESTARTNOINTR:
+	case -ERESTARTNOHAND:
+	case -ERESTART_RESTARTBLOCK:
+		/*
+		 * We can't just restart the syscall, since previously
+		 * submitted sqes may already be in progress. Just fail this
+		 * IO with EINTR.
+		 */
+		ret = -EINTR;
+		/* fall through */
+	default:
+		kiocb->ki_complete(kiocb, ret, 0);
+	}
+}
+
+static int io_import_fixed(struct io_ring_ctx *ctx, int rw,
+			   const struct io_uring_sqe *sqe,
+			   struct iov_iter *iter)
+{
+	size_t len = READ_ONCE(sqe->len);
+	struct io_mapped_ubuf *imu;
+	unsigned index, buf_index;
+	size_t offset;
+	u64 buf_addr;
+
+	/* attempt to use fixed buffers without having provided iovecs */
+	if (unlikely(!ctx->user_bufs))
+		return -EFAULT;
+
+	buf_index = READ_ONCE(sqe->buf_index);
+	if (unlikely(buf_index >= ctx->nr_user_bufs))
+		return -EFAULT;
+
+	index = array_index_nospec(buf_index, ctx->nr_user_bufs);
+	imu = &ctx->user_bufs[index];
+	buf_addr = READ_ONCE(sqe->addr);
+
+	/* overflow */
+	if (buf_addr + len < buf_addr)
+		return -EFAULT;
+	/* not inside the mapped region */
+	if (buf_addr < imu->ubuf || buf_addr + len > imu->ubuf + imu->len)
+		return -EFAULT;
+
+	/*
+	 * May not be a start of buffer, set size appropriately
+	 * and advance us to the beginning.
+	 */
+	offset = buf_addr - imu->ubuf;
+	iov_iter_bvec(iter, rw, imu->bvec, imu->nr_bvecs, offset + len);
+	if (offset)
+		iov_iter_advance(iter, offset);
+	return 0;
+}
+
+static int io_import_iovec(struct io_ring_ctx *ctx, int rw,
+			   const struct sqe_submit *s, struct iovec **iovec,
+			   struct iov_iter *iter)
+{
+	const struct io_uring_sqe *sqe = s->sqe;
+	void __user *buf = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	size_t sqe_len = READ_ONCE(sqe->len);
+	u8 opcode;
+
+	/*
+	 * We're reading ->opcode for the second time, but the first read
+	 * doesn't care whether it's _FIXED or not, so it doesn't matter
+	 * whether ->opcode changes concurrently. The first read does care
+	 * about whether it is a READ or a WRITE, so we don't trust this read
+	 * for that purpose and instead let the caller pass in the read/write
+	 * flag.
+	 */
+	opcode = READ_ONCE(sqe->opcode);
+	if (opcode == IORING_OP_READ_FIXED ||
+	    opcode == IORING_OP_WRITE_FIXED) {
+		ssize_t ret = io_import_fixed(ctx, rw, sqe, iter);
+		*iovec = NULL;
+		return ret;
+	}
+
+	if (!s->has_user)
+		return -EFAULT;
+
+#ifdef CONFIG_COMPAT
+	if (ctx->compat)
+		return compat_import_iovec(rw, buf, sqe_len, UIO_FASTIOV,
+						iovec, iter);
+#endif
+
+	return import_iovec(rw, buf, sqe_len, UIO_FASTIOV, iovec, iter);
+}
+
+/*
+ * Make a note of the last file/offset/direction we punted to async
+ * context. We'll use this information to see if we can piggy back a
+ * sequential request onto the previous one, if it's still hasn't been
+ * completed by the async worker.
+ */
+static void io_async_list_note(int rw, struct io_kiocb *req, size_t len)
+{
+	struct async_list *async_list = &req->ctx->pending_async[rw];
+	struct kiocb *kiocb = &req->rw;
+	struct file *filp = kiocb->ki_filp;
+	off_t io_end = kiocb->ki_pos + len;
+
+	if (filp == async_list->file && kiocb->ki_pos == async_list->io_end) {
+		unsigned long max_pages;
+
+		/* Use 8x RA size as a decent limiter for both reads/writes */
+		max_pages = filp->f_ra.ra_pages;
+		if (!max_pages)
+			max_pages = VM_MAX_READAHEAD >> (PAGE_SHIFT - 10);
+		max_pages *= 8;
+
+		/* If max pages are exceeded, reset the state */
+		len >>= PAGE_SHIFT;
+		if (async_list->io_pages + len <= max_pages) {
+			req->flags |= REQ_F_SEQ_PREV;
+			async_list->io_pages += len;
+		} else {
+			io_end = 0;
+			async_list->io_pages = 0;
+		}
+	}
+
+	/* New file? Reset state. */
+	if (async_list->file != filp) {
+		async_list->io_pages = 0;
+		async_list->file = filp;
+	}
+	async_list->io_end = io_end;
+}
+
+static ssize_t io_read(struct io_kiocb *req, const struct sqe_submit *s,
+		       bool force_nonblock, struct io_submit_state *state)
+{
+	struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
+	struct kiocb *kiocb = &req->rw;
+	struct iov_iter iter;
+	struct file *file;
+	size_t iov_count;
+	ssize_t ret;
+
+	ret = io_prep_rw(req, s, force_nonblock, state);
+	if (ret)
+		return ret;
+	file = kiocb->ki_filp;
+
+	ret = -EBADF;
+	if (unlikely(!(file->f_mode & FMODE_READ)))
+		goto out_fput;
+	ret = -EINVAL;
+	if (unlikely(!file->f_op->read_iter))
+		goto out_fput;
+
+	ret = io_import_iovec(req->ctx, READ, s, &iovec, &iter);
+	if (ret)
+		goto out_fput;
+
+	iov_count = iov_iter_count(&iter);
+	ret = rw_verify_area(READ, file, &kiocb->ki_pos, iov_count);
+	if (!ret) {
+		ssize_t ret2;
+
+		/* Catch -EAGAIN return for forced non-blocking submission */
+		ret2 = call_read_iter(file, kiocb, &iter);
+		if (!force_nonblock || ret2 != -EAGAIN) {
+			io_rw_done(kiocb, ret2);
+		} else {
+			/*
+			 * If ->needs_lock is true, we're already in async
+			 * context.
+			 */
+			if (!s->needs_lock)
+				io_async_list_note(READ, req, iov_count);
+			ret = -EAGAIN;
+		}
+	}
+	kfree(iovec);
+out_fput:
+	/* Hold on to the file for -EAGAIN */
+	if (unlikely(ret && ret != -EAGAIN))
+		io_fput(req);
+	return ret;
+}
+
+static ssize_t io_write(struct io_kiocb *req, const struct sqe_submit *s,
+			bool force_nonblock, struct io_submit_state *state)
+{
+	struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
+	struct kiocb *kiocb = &req->rw;
+	struct iov_iter iter;
+	struct file *file;
+	size_t iov_count;
+	ssize_t ret;
+
+	ret = io_prep_rw(req, s, force_nonblock, state);
+	if (ret)
+		return ret;
+
+	ret = -EBADF;
+	file = kiocb->ki_filp;
+	if (unlikely(!(file->f_mode & FMODE_WRITE)))
+		goto out_fput;
+	ret = -EINVAL;
+	if (unlikely(!file->f_op->write_iter))
+		goto out_fput;
+
+	ret = io_import_iovec(req->ctx, WRITE, s, &iovec, &iter);
+	if (ret)
+		goto out_fput;
+
+	iov_count = iov_iter_count(&iter);
+
+	ret = -EAGAIN;
+	if (force_nonblock && !(kiocb->ki_flags & IOCB_DIRECT)) {
+		/* If ->needs_lock is true, we're already in async context. */
+		if (!s->needs_lock)
+			io_async_list_note(WRITE, req, iov_count);
+		goto out_free;
+	}
+
+	ret = rw_verify_area(WRITE, file, &kiocb->ki_pos, iov_count);
+	if (!ret) {
+		/*
+		 * Open-code file_start_write here to grab freeze protection,
+		 * which will be released by another thread in
+		 * io_complete_rw().  Fool lockdep by telling it the lock got
+		 * released so that it doesn't complain about the held lock when
+		 * we return to userspace.
+		 */
+		if (S_ISREG(file_inode(file)->i_mode)) {
+			__sb_start_write(file_inode(file)->i_sb,
+						SB_FREEZE_WRITE, true);
+			__sb_writers_release(file_inode(file)->i_sb,
+						SB_FREEZE_WRITE);
+		}
+		kiocb->ki_flags |= IOCB_WRITE;
+		io_rw_done(kiocb, call_write_iter(file, kiocb, &iter));
+	}
+out_free:
+	kfree(iovec);
+out_fput:
+	/* Hold on to the file for -EAGAIN */
+	if (unlikely(ret && ret != -EAGAIN))
+		io_fput(req);
+	return ret;
+}
+
+/*
+ * IORING_OP_NOP just posts a completion event, nothing else.
+ */
+static int io_nop(struct io_kiocb *req, u64 user_data)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+	long err = 0;
+
+	if (unlikely(ctx->flags & IORING_SETUP_IOPOLL))
+		return -EINVAL;
+
+	/*
+	 * Twilight zone - it's possible that someone issued an opcode that
+	 * has a file attached, then got -EAGAIN on submission, and changed
+	 * the sqe before we retried it from async context. Avoid dropping
+	 * a file reference for this malicious case, and flag the error.
+	 */
+	if (req->rw.ki_filp) {
+		err = -EBADF;
+		io_fput(req);
+	}
+	io_cqring_add_event(ctx, user_data, err, 0);
+	io_free_req(req);
+	return 0;
+}
+
+static int io_prep_fsync(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+	unsigned flags;
+	int fd;
+
+	/* Prep already done */
+	if (req->rw.ki_filp)
+		return 0;
+
+	if (unlikely(ctx->flags & IORING_SETUP_IOPOLL))
+		return -EINVAL;
+	if (unlikely(sqe->addr || sqe->ioprio || sqe->buf_index))
+		return -EINVAL;
+
+	fd = READ_ONCE(sqe->fd);
+	flags = READ_ONCE(sqe->flags);
+
+	if (flags & IOSQE_FIXED_FILE) {
+		if (unlikely(!ctx->user_files || fd >= ctx->nr_user_files))
+			return -EBADF;
+		req->rw.ki_filp = ctx->user_files[fd];
+		req->flags |= REQ_F_FIXED_FILE;
+	} else {
+		req->rw.ki_filp = fget(fd);
+		if (unlikely(!req->rw.ki_filp))
+			return -EBADF;
+	}
+
+	return 0;
+}
+
+static int io_fsync(struct io_kiocb *req, const struct io_uring_sqe *sqe,
+		    bool force_nonblock)
+{
+	loff_t sqe_off = READ_ONCE(sqe->off);
+	loff_t sqe_len = READ_ONCE(sqe->len);
+	loff_t end = sqe_off + sqe_len;
+	unsigned fsync_flags;
+	int ret;
+
+	fsync_flags = READ_ONCE(sqe->fsync_flags);
+	if (unlikely(fsync_flags & ~IORING_FSYNC_DATASYNC))
+		return -EINVAL;
+
+	ret = io_prep_fsync(req, sqe);
+	if (ret)
+		return ret;
+
+	/* fsync always requires a blocking context */
+	if (force_nonblock)
+		return -EAGAIN;
+
+	ret = vfs_fsync_range(req->rw.ki_filp, sqe_off,
+				end > 0 ? end : LLONG_MAX,
+				fsync_flags & IORING_FSYNC_DATASYNC);
+
+	io_fput(req);
+	io_cqring_add_event(req->ctx, sqe->user_data, ret, 0);
+	io_free_req(req);
+	return 0;
+}
+
+static void io_poll_remove_one(struct io_kiocb *req)
+{
+	struct io_poll_iocb *poll = &req->poll;
+
+	spin_lock(&poll->head->lock);
+	WRITE_ONCE(poll->canceled, true);
+	if (!list_empty(&poll->wait.entry)) {
+		list_del_init(&poll->wait.entry);
+		queue_work(req->ctx->sqo_wq, &req->work);
+	}
+	spin_unlock(&poll->head->lock);
+
+	list_del_init(&req->list);
+}
+
+static void io_poll_remove_all(struct io_ring_ctx *ctx)
+{
+	struct io_kiocb *req;
+
+	spin_lock_irq(&ctx->completion_lock);
+	while (!list_empty(&ctx->cancel_list)) {
+		req = list_first_entry(&ctx->cancel_list, struct io_kiocb,list);
+		io_poll_remove_one(req);
+	}
+	spin_unlock_irq(&ctx->completion_lock);
+}
+
+/*
+ * Find a running poll command that matches one specified in sqe->addr,
+ * and remove it if found.
+ */
+static int io_poll_remove(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+	struct io_kiocb *poll_req, *next;
+	int ret = -ENOENT;
+
+	if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
+		return -EINVAL;
+	if (sqe->ioprio || sqe->off || sqe->len || sqe->buf_index ||
+	    sqe->poll_events)
+		return -EINVAL;
+
+	spin_lock_irq(&ctx->completion_lock);
+	list_for_each_entry_safe(poll_req, next, &ctx->cancel_list, list) {
+		if (READ_ONCE(sqe->addr) == poll_req->user_data) {
+			io_poll_remove_one(poll_req);
+			ret = 0;
+			break;
+		}
+	}
+	spin_unlock_irq(&ctx->completion_lock);
+
+	io_cqring_add_event(req->ctx, sqe->user_data, ret, 0);
+	io_free_req(req);
+	return 0;
+}
+
+static void io_poll_complete(struct io_kiocb *req, __poll_t mask)
+{
+	io_cqring_add_event(req->ctx, req->user_data, mangle_poll(mask), 0);
+	io_fput(req);
+	io_free_req(req);
+}
+
+static void io_poll_complete_work(struct work_struct *work)
+{
+	struct io_kiocb *req = container_of(work, struct io_kiocb, work);
+	struct io_poll_iocb *poll = &req->poll;
+	struct poll_table_struct pt = { ._key = poll->events };
+	struct io_ring_ctx *ctx = req->ctx;
+	__poll_t mask = 0;
+
+	if (!READ_ONCE(poll->canceled))
+		mask = vfs_poll(poll->file, &pt) & poll->events;
+
+	/*
+	 * Note that ->ki_cancel callers also delete iocb from active_reqs after
+	 * calling ->ki_cancel.  We need the ctx_lock roundtrip here to
+	 * synchronize with them.  In the cancellation case the list_del_init
+	 * itself is not actually needed, but harmless so we keep it in to
+	 * avoid further branches in the fast path.
+	 */
+	spin_lock_irq(&ctx->completion_lock);
+	if (!mask && !READ_ONCE(poll->canceled)) {
+		add_wait_queue(poll->head, &poll->wait);
+		spin_unlock_irq(&ctx->completion_lock);
+		return;
+	}
+	list_del_init(&req->list);
+	spin_unlock_irq(&ctx->completion_lock);
+
+	io_poll_complete(req, mask);
+}
+
+static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
+			void *key)
+{
+	struct io_poll_iocb *poll = container_of(wait, struct io_poll_iocb,
+							wait);
+	struct io_kiocb *req = container_of(poll, struct io_kiocb, poll);
+	struct io_ring_ctx *ctx = req->ctx;
+	__poll_t mask = key_to_poll(key);
+
+	poll->woken = true;
+
+	/* for instances that support it check for an event match first: */
+	if (mask) {
+		unsigned long flags;
+
+		if (!(mask & poll->events))
+			return 0;
+
+		/* try to complete the iocb inline if we can: */
+		if (spin_trylock_irqsave(&ctx->completion_lock, flags)) {
+			list_del(&req->list);
+			spin_unlock_irqrestore(&ctx->completion_lock, flags);
+
+			list_del_init(&poll->wait.entry);
+			io_poll_complete(req, mask);
+			return 1;
+		}
+	}
+
+	list_del_init(&poll->wait.entry);
+	queue_work(ctx->sqo_wq, &req->work);
+	return 1;
+}
+
+struct io_poll_table {
+	struct poll_table_struct pt;
+	struct io_kiocb *req;
+	int error;
+};
+
+static void io_poll_queue_proc(struct file *file, struct wait_queue_head *head,
+			       struct poll_table_struct *p)
+{
+	struct io_poll_table *pt = container_of(p, struct io_poll_table, pt);
+
+	if (unlikely(pt->req->poll.head)) {
+		pt->error = -EINVAL;
+		return;
+	}
+
+	pt->error = 0;
+	pt->req->poll.head = head;
+	add_wait_queue(head, &pt->req->poll.wait);
+}
+
+static int io_poll_add(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_poll_iocb *poll = &req->poll;
+	struct io_ring_ctx *ctx = req->ctx;
+	struct io_poll_table ipt;
+	unsigned flags;
+	__poll_t mask;
+	u16 events;
+	int fd;
+
+	if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
+		return -EINVAL;
+	if (sqe->addr || sqe->ioprio || sqe->off || sqe->len || sqe->buf_index)
+		return -EINVAL;
+
+	INIT_WORK(&req->work, io_poll_complete_work);
+	events = READ_ONCE(sqe->poll_events);
+	poll->events = demangle_poll(events) | EPOLLERR | EPOLLHUP;
+
+	flags = READ_ONCE(sqe->flags);
+	fd = READ_ONCE(sqe->fd);
+
+	if (flags & IOSQE_FIXED_FILE) {
+		if (unlikely(!ctx->user_files || fd >= ctx->nr_user_files))
+			return -EBADF;
+		poll->file = ctx->user_files[fd];
+		req->flags |= REQ_F_FIXED_FILE;
+	} else {
+		poll->file = fget(fd);
+	}
+	if (unlikely(!poll->file))
+		return -EBADF;
+
+	poll->head = NULL;
+	poll->woken = false;
+	poll->canceled = false;
+
+	ipt.pt._qproc = io_poll_queue_proc;
+	ipt.pt._key = poll->events;
+	ipt.req = req;
+	ipt.error = -EINVAL; /* same as no support for IOCB_CMD_POLL */
+
+	/* initialized the list so that we can do list_empty checks */
+	INIT_LIST_HEAD(&poll->wait.entry);
+	init_waitqueue_func_entry(&poll->wait, io_poll_wake);
+
+	/* one for removal from waitqueue, one for this function */
+	refcount_set(&req->refs, 2);
+
+	mask = vfs_poll(poll->file, &ipt.pt) & poll->events;
+	if (unlikely(!poll->head)) {
+		/* we did not manage to set up a waitqueue, done */
+		goto out;
+	}
+
+	spin_lock_irq(&ctx->completion_lock);
+	spin_lock(&poll->head->lock);
+	if (poll->woken) {
+		/* wake_up context handles the rest */
+		mask = 0;
+		ipt.error = 0;
+	} else if (mask || ipt.error) {
+		/* if we get an error or a mask we are done */
+		WARN_ON_ONCE(list_empty(&poll->wait.entry));
+		list_del_init(&poll->wait.entry);
+	} else {
+		/* actually waiting for an event */
+		list_add_tail(&req->list, &ctx->cancel_list);
+	}
+	spin_unlock(&poll->head->lock);
+	spin_unlock_irq(&ctx->completion_lock);
+
+out:
+	if (unlikely(ipt.error)) {
+		if (!(flags & IOSQE_FIXED_FILE))
+			fput(poll->file);
+		/*
+		 * Drop one of our refs to this req, __io_submit_sqe() will
+		 * drop the other one since we're returning an error.
+		 */
+		io_free_req(req);
+		return ipt.error;
+	}
+
+	if (mask)
+		io_poll_complete(req, mask);
+	io_free_req(req);
+	return 0;
+}
+
+static int __io_submit_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
+			   const struct sqe_submit *s, bool force_nonblock,
+			   struct io_submit_state *state)
+{
+	ssize_t ret;
+	int opcode;
+
+	if (unlikely(s->index >= ctx->sq_entries))
+		return -EINVAL;
+	req->user_data = READ_ONCE(s->sqe->user_data);
+
+	opcode = READ_ONCE(s->sqe->opcode);
+	switch (opcode) {
+	case IORING_OP_NOP:
+		ret = io_nop(req, req->user_data);
+		break;
+	case IORING_OP_READV:
+		if (unlikely(s->sqe->buf_index))
+			return -EINVAL;
+		ret = io_read(req, s, force_nonblock, state);
+		break;
+	case IORING_OP_WRITEV:
+		if (unlikely(s->sqe->buf_index))
+			return -EINVAL;
+		ret = io_write(req, s, force_nonblock, state);
+		break;
+	case IORING_OP_READ_FIXED:
+		ret = io_read(req, s, force_nonblock, state);
+		break;
+	case IORING_OP_WRITE_FIXED:
+		ret = io_write(req, s, force_nonblock, state);
+		break;
+	case IORING_OP_FSYNC:
+		ret = io_fsync(req, s->sqe, force_nonblock);
+		break;
+	case IORING_OP_POLL_ADD:
+		ret = io_poll_add(req, s->sqe);
+		break;
+	case IORING_OP_POLL_REMOVE:
+		ret = io_poll_remove(req, s->sqe);
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	if (ret)
+		return ret;
+
+	if (ctx->flags & IORING_SETUP_IOPOLL) {
+		if (req->error == -EAGAIN)
+			return -EAGAIN;
+
+		/* workqueue context doesn't hold uring_lock, grab it now */
+		if (s->needs_lock)
+			mutex_lock(&ctx->uring_lock);
+		io_iopoll_req_issued(req);
+		if (s->needs_lock)
+			mutex_unlock(&ctx->uring_lock);
+	}
+
+	return 0;
+}
+
+static struct async_list *io_async_list_from_sqe(struct io_ring_ctx *ctx,
+						 const struct io_uring_sqe *sqe)
+{
+	switch (sqe->opcode) {
+	case IORING_OP_READV:
+	case IORING_OP_READ_FIXED:
+		return &ctx->pending_async[READ];
+	case IORING_OP_WRITEV:
+	case IORING_OP_WRITE_FIXED:
+		return &ctx->pending_async[WRITE];
+	default:
+		return NULL;
+	}
+}
+
+static inline bool io_sqe_needs_user(const struct io_uring_sqe *sqe)
+{
+	u8 opcode = READ_ONCE(sqe->opcode);
+
+	return !(opcode == IORING_OP_READ_FIXED ||
+		 opcode == IORING_OP_WRITE_FIXED);
+}
+
+static void io_sq_wq_submit_work(struct work_struct *work)
+{
+	struct io_kiocb *req = container_of(work, struct io_kiocb, work);
+	struct io_ring_ctx *ctx = req->ctx;
+	struct mm_struct *cur_mm = NULL;
+	struct async_list *async_list;
+	LIST_HEAD(req_list);
+	mm_segment_t old_fs;
+	int ret;
+
+	async_list = io_async_list_from_sqe(ctx, req->submit.sqe);
+restart:
+	do {
+		struct sqe_submit *s = &req->submit;
+		const struct io_uring_sqe *sqe = s->sqe;
+
+		/* Ensure we clear previously set forced non-block flag */
+		req->flags &= ~REQ_F_FORCE_NONBLOCK;
+		req->rw.ki_flags &= ~IOCB_NOWAIT;
+
+		ret = 0;
+		if (io_sqe_needs_user(sqe) && !cur_mm) {
+			if (!mmget_not_zero(ctx->sqo_mm)) {
+				ret = -EFAULT;
+			} else {
+				cur_mm = ctx->sqo_mm;
+				use_mm(cur_mm);
+				old_fs = get_fs();
+				set_fs(USER_DS);
+			}
+		}
+
+		if (!ret) {
+			s->has_user = cur_mm != NULL;
+			s->needs_lock = true;
+			do {
+				ret = __io_submit_sqe(ctx, req, s, false, NULL);
+				/*
+				 * We can get EAGAIN for polled IO even though
+				 * we're forcing a sync submission from here,
+				 * since we can't wait for request slots on the
+				 * block side.
+				 */
+				if (ret != -EAGAIN)
+					break;
+				cond_resched();
+			} while (1);
+		}
+		if (ret) {
+			io_cqring_add_event(ctx, sqe->user_data, ret, 0);
+			io_free_req(req);
+		}
+
+		/* async context always use a copy of the sqe */
+		kfree(sqe);
+
+		if (!async_list)
+			break;
+		if (!list_empty(&req_list)) {
+			req = list_first_entry(&req_list, struct io_kiocb,
+						list);
+			list_del(&req->list);
+			continue;
+		}
+		if (list_empty(&async_list->list))
+			break;
+
+		req = NULL;
+		spin_lock(&async_list->lock);
+		if (list_empty(&async_list->list)) {
+			spin_unlock(&async_list->lock);
+			break;
+		}
+		list_splice_init(&async_list->list, &req_list);
+		spin_unlock(&async_list->lock);
+
+		req = list_first_entry(&req_list, struct io_kiocb, list);
+		list_del(&req->list);
+	} while (req);
+
+	/*
+	 * Rare case of racing with a submitter. If we find the count has
+	 * dropped to zero AND we have pending work items, then restart
+	 * the processing. This is a tiny race window.
+	 */
+	if (async_list) {
+		ret = atomic_dec_return(&async_list->cnt);
+		while (!ret && !list_empty(&async_list->list)) {
+			spin_lock(&async_list->lock);
+			atomic_inc(&async_list->cnt);
+			list_splice_init(&async_list->list, &req_list);
+			spin_unlock(&async_list->lock);
+
+			if (!list_empty(&req_list)) {
+				req = list_first_entry(&req_list,
+							struct io_kiocb, list);
+				list_del(&req->list);
+				goto restart;
+			}
+			ret = atomic_dec_return(&async_list->cnt);
+		}
+	}
+
+	if (cur_mm) {
+		set_fs(old_fs);
+		unuse_mm(cur_mm);
+		mmput(cur_mm);
+	}
+}
+
+/*
+ * See if we can piggy back onto previously submitted work, that is still
+ * running. We currently only allow this if the new request is sequential
+ * to the previous one we punted.
+ */
+static bool io_add_to_prev_work(struct async_list *list, struct io_kiocb *req)
+{
+	bool ret = false;
+
+	if (!list)
+		return false;
+	if (!(req->flags & REQ_F_SEQ_PREV))
+		return false;
+	if (!atomic_read(&list->cnt))
+		return false;
+
+	ret = true;
+	spin_lock(&list->lock);
+	list_add_tail(&req->list, &list->list);
+	if (!atomic_read(&list->cnt)) {
+		list_del_init(&req->list);
+		ret = false;
+	}
+	spin_unlock(&list->lock);
+	return ret;
+}
+
+static int io_submit_sqe(struct io_ring_ctx *ctx, struct sqe_submit *s,
+			 struct io_submit_state *state)
+{
+	struct io_kiocb *req;
+	ssize_t ret;
+
+	/* enforce forwards compatibility on users */
+	if (unlikely(s->sqe->flags & ~IOSQE_FIXED_FILE))
+		return -EINVAL;
+
+	req = io_get_req(ctx, state);
+	if (unlikely(!req))
+		return -EAGAIN;
+
+	req->rw.ki_filp = NULL;
+
+	ret = __io_submit_sqe(ctx, req, s, true, state);
+	if (ret == -EAGAIN) {
+		struct io_uring_sqe *sqe_copy;
+
+		sqe_copy = kmalloc(sizeof(*sqe_copy), GFP_KERNEL);
+		if (sqe_copy) {
+			struct async_list *list;
+
+			memcpy(sqe_copy, s->sqe, sizeof(*sqe_copy));
+			s->sqe = sqe_copy;
+
+			memcpy(&req->submit, s, sizeof(*s));
+			list = io_async_list_from_sqe(ctx, s->sqe);
+			if (!io_add_to_prev_work(list, req)) {
+				if (list)
+					atomic_inc(&list->cnt);
+				INIT_WORK(&req->work, io_sq_wq_submit_work);
+				queue_work(ctx->sqo_wq, &req->work);
+			}
+			ret = 0;
+		}
+	}
+	if (ret)
+		io_free_req(req);
+
+	return ret;
+}
+
+/*
+ * Batched submission is done, ensure local IO is flushed out.
+ */
+static void io_submit_state_end(struct io_submit_state *state)
+{
+	blk_finish_plug(&state->plug);
+	io_file_put(state, NULL);
+	if (state->free_reqs)
+		kmem_cache_free_bulk(req_cachep, state->free_reqs,
+					&state->reqs[state->cur_req]);
+}
+
+/*
+ * Start submission side cache.
+ */
+static void io_submit_state_start(struct io_submit_state *state,
+				  struct io_ring_ctx *ctx, unsigned max_ios)
+{
+	blk_start_plug(&state->plug);
+	state->free_reqs = 0;
+	state->file = NULL;
+	state->ios_left = max_ios;
+}
+
+static void io_commit_sqring(struct io_ring_ctx *ctx)
+{
+	struct io_sq_ring *ring = ctx->sq_ring;
+
+	if (ctx->cached_sq_head != READ_ONCE(ring->r.head)) {
+		/*
+		 * Ensure any loads from the SQEs are done at this point,
+		 * since once we write the new head, the application could
+		 * write new data to them.
+		 */
+		smp_store_release(&ring->r.head, ctx->cached_sq_head);
+
+		/*
+		 * write side barrier of head update, app has read side. See
+		 * comment at the top of this file
+		 */
+		smp_wmb();
+	}
+}
+
+/*
+ * Undo last io_get_sqring()
+ */
+static void io_drop_sqring(struct io_ring_ctx *ctx)
+{
+	ctx->cached_sq_head--;
+}
+
+/*
+ * Fetch an sqe, if one is available. Note that s->sqe will point to memory
+ * that is mapped by userspace. This means that care needs to be taken to
+ * ensure that reads are stable, as we cannot rely on userspace always
+ * being a good citizen. If members of the sqe are validated and then later
+ * used, it's important that those reads are done through READ_ONCE() to
+ * prevent a re-load down the line.
+ */
+static bool io_get_sqring(struct io_ring_ctx *ctx, struct sqe_submit *s)
+{
+	struct io_sq_ring *ring = ctx->sq_ring;
+	unsigned head;
+
+	/*
+	 * The cached sq head (or cq tail) serves two purposes:
+	 *
+	 * 1) allows us to batch the cost of updating the user visible
+	 *    head updates.
+	 * 2) allows the kernel side to track the head on its own, even
+	 *    though the application is the one updating it.
+	 */
+	head = ctx->cached_sq_head;
+	/* See comment at the top of this file */
+	smp_rmb();
+	if (head == READ_ONCE(ring->r.tail))
+		return false;
+
+	head = READ_ONCE(ring->array[head & ctx->sq_mask]);
+	if (head < ctx->sq_entries) {
+		s->index = head;
+		s->sqe = &ctx->sq_sqes[head];
+		ctx->cached_sq_head++;
+		return true;
+	}
+
+	/* drop invalid entries */
+	ctx->cached_sq_head++;
+	ring->dropped++;
+	/* See comment at the top of this file */
+	smp_wmb();
+	return false;
+}
+
+static int io_submit_sqes(struct io_ring_ctx *ctx, struct sqe_submit *sqes,
+			  unsigned int nr, bool has_user, bool mm_fault)
+{
+	struct io_submit_state state, *statep = NULL;
+	int ret, i, submitted = 0;
+
+	if (nr > IO_PLUG_THRESHOLD) {
+		io_submit_state_start(&state, ctx, nr);
+		statep = &state;
+	}
+
+	for (i = 0; i < nr; i++) {
+		if (unlikely(mm_fault)) {
+			ret = -EFAULT;
+		} else {
+			sqes[i].has_user = has_user;
+			sqes[i].needs_lock = true;
+			sqes[i].needs_fixed_file = true;
+			ret = io_submit_sqe(ctx, &sqes[i], statep);
+		}
+		if (!ret) {
+			submitted++;
+			continue;
+		}
+
+		io_cqring_add_event(ctx, sqes[i].sqe->user_data, ret, 0);
+	}
+
+	if (statep)
+		io_submit_state_end(&state);
+
+	return submitted;
+}
+
+static int io_sq_thread(void *data)
+{
+	struct sqe_submit sqes[IO_IOPOLL_BATCH];
+	struct io_ring_ctx *ctx = data;
+	struct mm_struct *cur_mm = NULL;
+	mm_segment_t old_fs;
+	DEFINE_WAIT(wait);
+	unsigned inflight;
+	unsigned long timeout;
+
+	old_fs = get_fs();
+	set_fs(USER_DS);
+
+	timeout = inflight = 0;
+	while (!kthread_should_stop() && !ctx->sqo_stop) {
+		bool all_fixed, mm_fault = false;
+		int i;
+
+		if (inflight) {
+			unsigned nr_events = 0;
+
+			if (ctx->flags & IORING_SETUP_IOPOLL) {
+				/*
+				 * We disallow the app entering submit/complete
+				 * with polling, but we still need to lock the
+				 * ring to prevent racing with polled issue
+				 * that got punted to a workqueue.
+				 */
+				mutex_lock(&ctx->uring_lock);
+				io_iopoll_check(ctx, &nr_events, 0);
+				mutex_unlock(&ctx->uring_lock);
+			} else {
+				/*
+				 * Normal IO, just pretend everything completed.
+				 * We don't have to poll completions for that.
+				 */
+				nr_events = inflight;
+			}
+
+			inflight -= nr_events;
+			if (!inflight)
+				timeout = jiffies + ctx->sq_thread_idle;
+		}
+
+		if (!io_get_sqring(ctx, &sqes[0])) {
+			/*
+			 * We're polling. If we're within the defined idle
+			 * period, then let us spin without work before going
+			 * to sleep.
+			 */
+			if (inflight || !time_after(jiffies, timeout)) {
+				cpu_relax();
+				continue;
+			}
+
+			/*
+			 * Drop cur_mm before scheduling, we can't hold it for
+			 * long periods (or over schedule()). Do this before
+			 * adding ourselves to the waitqueue, as the unuse/drop
+			 * may sleep.
+			 */
+			if (cur_mm) {
+				unuse_mm(cur_mm);
+				mmput(cur_mm);
+				cur_mm = NULL;
+			}
+
+			prepare_to_wait(&ctx->sqo_wait, &wait,
+						TASK_INTERRUPTIBLE);
+
+			/* Tell userspace we may need a wakeup call */
+			ctx->sq_ring->flags |= IORING_SQ_NEED_WAKEUP;
+			smp_wmb();
+
+			if (!io_get_sqring(ctx, &sqes[0])) {
+				if (kthread_should_stop()) {
+					finish_wait(&ctx->sqo_wait, &wait);
+					break;
+				}
+				if (signal_pending(current))
+					flush_signals(current);
+				schedule();
+				finish_wait(&ctx->sqo_wait, &wait);
+
+				ctx->sq_ring->flags &= ~IORING_SQ_NEED_WAKEUP;
+				smp_wmb();
+				continue;
+			}
+			finish_wait(&ctx->sqo_wait, &wait);
+
+			ctx->sq_ring->flags &= ~IORING_SQ_NEED_WAKEUP;
+			smp_wmb();
+		}
+
+		i = 0;
+		all_fixed = true;
+		do {
+			if (all_fixed && io_sqe_needs_user(sqes[i].sqe))
+				all_fixed = false;
+
+			i++;
+			if (i == ARRAY_SIZE(sqes))
+				break;
+		} while (io_get_sqring(ctx, &sqes[i]));
+
+		/* Unless all new commands are FIXED regions, grab mm */
+		if (!all_fixed && !cur_mm) {
+			mm_fault = !mmget_not_zero(ctx->sqo_mm);
+			if (!mm_fault) {
+				use_mm(ctx->sqo_mm);
+				cur_mm = ctx->sqo_mm;
+			}
+		}
+
+		inflight += io_submit_sqes(ctx, sqes, i, cur_mm != NULL,
+						mm_fault);
+
+		/* Commit SQ ring head once we've consumed all SQEs */
+		io_commit_sqring(ctx);
+	}
+
+	set_fs(old_fs);
+	if (cur_mm) {
+		unuse_mm(cur_mm);
+		mmput(cur_mm);
+	}
+	return 0;
+}
+
+static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit)
+{
+	struct io_submit_state state, *statep = NULL;
+	int i, ret = 0, submit = 0;
+
+	if (to_submit > IO_PLUG_THRESHOLD) {
+		io_submit_state_start(&state, ctx, to_submit);
+		statep = &state;
+	}
+
+	for (i = 0; i < to_submit; i++) {
+		struct sqe_submit s;
+
+		if (!io_get_sqring(ctx, &s))
+			break;
+
+		s.has_user = true;
+		s.needs_lock = false;
+		s.needs_fixed_file = false;
+
+		ret = io_submit_sqe(ctx, &s, statep);
+		if (ret) {
+			io_drop_sqring(ctx);
+			break;
+		}
+
+		submit++;
+	}
+	io_commit_sqring(ctx);
+
+	if (statep)
+		io_submit_state_end(statep);
+
+	return submit ? submit : ret;
+}
+
+static unsigned io_cqring_events(struct io_cq_ring *ring)
+{
+	return READ_ONCE(ring->r.tail) - READ_ONCE(ring->r.head);
+}
+
+/*
+ * Wait until events become available, if we don't already have some. The
+ * application must reap them itself, as they reside on the shared cq ring.
+ */
+static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
+			  const sigset_t __user *sig, size_t sigsz)
+{
+	struct io_cq_ring *ring = ctx->cq_ring;
+	sigset_t ksigmask, sigsaved;
+	DEFINE_WAIT(wait);
+	int ret;
+
+	/* See comment at the top of this file */
+	smp_rmb();
+	if (io_cqring_events(ring) >= min_events)
+		return 0;
+
+	if (sig) {
+		ret = set_user_sigmask(sig, &ksigmask, &sigsaved, sigsz);
+		if (ret)
+			return ret;
+	}
+
+	do {
+		prepare_to_wait(&ctx->wait, &wait, TASK_INTERRUPTIBLE);
+
+		ret = 0;
+		/* See comment at the top of this file */
+		smp_rmb();
+		if (io_cqring_events(ring) >= min_events)
+			break;
+
+		schedule();
+
+		ret = -EINTR;
+		if (signal_pending(current))
+			break;
+	} while (1);
+
+	finish_wait(&ctx->wait, &wait);
+
+	if (sig)
+		restore_user_sigmask(sig, &sigsaved);
+
+	return READ_ONCE(ring->r.head) == READ_ONCE(ring->r.tail) ? ret : 0;
+}
+
+static void __io_sqe_files_unregister(struct io_ring_ctx *ctx)
+{
+#if defined(CONFIG_UNIX)
+	if (ctx->ring_sock) {
+		struct sock *sock = ctx->ring_sock->sk;
+		struct sk_buff *skb;
+
+		while ((skb = skb_dequeue(&sock->sk_receive_queue)) != NULL)
+			kfree_skb(skb);
+	}
+#else
+	int i;
+
+	for (i = 0; i < ctx->nr_user_files; i++)
+		fput(ctx->user_files[i]);
+#endif
+}
+
+static int io_sqe_files_unregister(struct io_ring_ctx *ctx)
+{
+	if (!ctx->user_files)
+		return -ENXIO;
+
+	__io_sqe_files_unregister(ctx);
+	kfree(ctx->user_files);
+	ctx->user_files = NULL;
+	ctx->nr_user_files = 0;
+	return 0;
+}
+
+static void io_sq_thread_stop(struct io_ring_ctx *ctx)
+{
+	if (ctx->sqo_thread) {
+		ctx->sqo_stop = 1;
+		mb();
+		kthread_stop(ctx->sqo_thread);
+		ctx->sqo_thread = NULL;
+	}
+}
+
+static void io_finish_async(struct io_ring_ctx *ctx)
+{
+	io_sq_thread_stop(ctx);
+
+	if (ctx->sqo_wq) {
+		destroy_workqueue(ctx->sqo_wq);
+		ctx->sqo_wq = NULL;
+	}
+}
+
+#if defined(CONFIG_UNIX)
+static void io_destruct_skb(struct sk_buff *skb)
+{
+	struct io_ring_ctx *ctx = skb->sk->sk_user_data;
+
+	io_finish_async(ctx);
+	unix_destruct_scm(skb);
+}
+
+/*
+ * Ensure the UNIX gc is aware of our file set, so we are certain that
+ * the io_uring can be safely unregistered on process exit, even if we have
+ * loops in the file referencing.
+ */
+static int __io_sqe_files_scm(struct io_ring_ctx *ctx, int nr, int offset)
+{
+	struct sock *sk = ctx->ring_sock->sk;
+	struct scm_fp_list *fpl;
+	struct sk_buff *skb;
+	int i;
+
+	if (!capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) {
+		unsigned long inflight = ctx->user->unix_inflight + nr;
+
+		if (inflight > task_rlimit(current, RLIMIT_NOFILE))
+			return -EMFILE;
+	}
+
+	fpl = kzalloc(sizeof(*fpl), GFP_KERNEL);
+	if (!fpl)
+		return -ENOMEM;
+
+	skb = alloc_skb(0, GFP_KERNEL);
+	if (!skb) {
+		kfree(fpl);
+		return -ENOMEM;
+	}
+
+	skb->sk = sk;
+	skb->destructor = io_destruct_skb;
+
+	fpl->user = get_uid(ctx->user);
+	for (i = 0; i < nr; i++) {
+		fpl->fp[i] = get_file(ctx->user_files[i + offset]);
+		unix_inflight(fpl->user, fpl->fp[i]);
+	}
+
+	fpl->max = fpl->count = nr;
+	UNIXCB(skb).fp = fpl;
+	refcount_add(skb->truesize, &sk->sk_wmem_alloc);
+	skb_queue_head(&sk->sk_receive_queue, skb);
+
+	for (i = 0; i < nr; i++)
+		fput(fpl->fp[i]);
+
+	return 0;
+}
+
+/*
+ * If UNIX sockets are enabled, fd passing can cause a reference cycle which
+ * causes regular reference counting to break down. We rely on the UNIX
+ * garbage collection to take care of this problem for us.
+ */
+static int io_sqe_files_scm(struct io_ring_ctx *ctx)
+{
+	unsigned left, total;
+	int ret = 0;
+
+	total = 0;
+	left = ctx->nr_user_files;
+	while (left) {
+		unsigned this_files = min_t(unsigned, left, SCM_MAX_FD);
+		int ret;
+
+		ret = __io_sqe_files_scm(ctx, this_files, total);
+		if (ret)
+			break;
+		left -= this_files;
+		total += this_files;
+	}
+
+	if (!ret)
+		return 0;
+
+	while (total < ctx->nr_user_files) {
+		fput(ctx->user_files[total]);
+		total++;
+	}
+
+	return ret;
+}
+#else
+static int io_sqe_files_scm(struct io_ring_ctx *ctx)
+{
+	return 0;
+}
+#endif
+
+static int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg,
+				 unsigned nr_args)
+{
+	__s32 __user *fds = (__s32 __user *) arg;
+	int fd, ret = 0;
+	unsigned i;
+
+	if (ctx->user_files)
+		return -EBUSY;
+	if (!nr_args)
+		return -EINVAL;
+	if (nr_args > IORING_MAX_FIXED_FILES)
+		return -EMFILE;
+
+	ctx->user_files = kcalloc(nr_args, sizeof(struct file *), GFP_KERNEL);
+	if (!ctx->user_files)
+		return -ENOMEM;
+
+	for (i = 0; i < nr_args; i++) {
+		ret = -EFAULT;
+		if (copy_from_user(&fd, &fds[i], sizeof(fd)))
+			break;
+
+		ctx->user_files[i] = fget(fd);
+
+		ret = -EBADF;
+		if (!ctx->user_files[i])
+			break;
+		/*
+		 * Don't allow io_uring instances to be registered. If UNIX
+		 * isn't enabled, then this causes a reference cycle and this
+		 * instance can never get freed. If UNIX is enabled we'll
+		 * handle it just fine, but there's still no point in allowing
+		 * a ring fd as it doesn't support regular read/write anyway.
+		 */
+		if (ctx->user_files[i]->f_op == &io_uring_fops) {
+			fput(ctx->user_files[i]);
+			break;
+		}
+		ctx->nr_user_files++;
+		ret = 0;
+	}
+
+	if (ret) {
+		for (i = 0; i < ctx->nr_user_files; i++)
+			fput(ctx->user_files[i]);
+
+		kfree(ctx->user_files);
+		ctx->nr_user_files = 0;
+		return ret;
+	}
+
+	ret = io_sqe_files_scm(ctx);
+	if (ret)
+		io_sqe_files_unregister(ctx);
+
+	return ret;
+}
+
+static int io_sq_offload_start(struct io_ring_ctx *ctx,
+			       struct io_uring_params *p)
+{
+	int ret;
+
+	init_waitqueue_head(&ctx->sqo_wait);
+	mmgrab(current->mm);
+	ctx->sqo_mm = current->mm;
+
+	ctx->sq_thread_idle = msecs_to_jiffies(p->sq_thread_idle);
+	if (!ctx->sq_thread_idle)
+		ctx->sq_thread_idle = HZ;
+
+	ret = -EINVAL;
+	if (!cpu_possible(p->sq_thread_cpu))
+		goto err;
+
+	if (ctx->flags & IORING_SETUP_SQPOLL) {
+		if (p->flags & IORING_SETUP_SQ_AFF) {
+			int cpu;
+
+			cpu = array_index_nospec(p->sq_thread_cpu, NR_CPUS);
+			ctx->sqo_thread = kthread_create_on_cpu(io_sq_thread,
+							ctx, cpu,
+							"io_uring-sq");
+		} else {
+			ctx->sqo_thread = kthread_create(io_sq_thread, ctx,
+							"io_uring-sq");
+		}
+		if (IS_ERR(ctx->sqo_thread)) {
+			ret = PTR_ERR(ctx->sqo_thread);
+			ctx->sqo_thread = NULL;
+			goto err;
+		}
+		wake_up_process(ctx->sqo_thread);
+	} else if (p->flags & IORING_SETUP_SQ_AFF) {
+		/* Can't have SQ_AFF without SQPOLL */
+		ret = -EINVAL;
+		goto err;
+	}
+
+	/* Do QD, or 2 * CPUS, whatever is smallest */
+	ctx->sqo_wq = alloc_workqueue("io_ring-wq", WQ_UNBOUND | WQ_FREEZABLE,
+			min(ctx->sq_entries - 1, 2 * num_online_cpus()));
+	if (!ctx->sqo_wq) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	return 0;
+err:
+	io_sq_thread_stop(ctx);
+	mmdrop(ctx->sqo_mm);
+	ctx->sqo_mm = NULL;
+	return ret;
+}
+
+static void io_unaccount_mem(struct user_struct *user, unsigned long nr_pages)
+{
+	atomic_long_sub(nr_pages, &user->locked_vm);
+}
+
+static int io_account_mem(struct user_struct *user, unsigned long nr_pages)
+{
+	unsigned long page_limit, cur_pages, new_pages;
+
+	/* Don't allow more pages than we can safely lock */
+	page_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
+
+	do {
+		cur_pages = atomic_long_read(&user->locked_vm);
+		new_pages = cur_pages + nr_pages;
+		if (new_pages > page_limit)
+			return -ENOMEM;
+	} while (atomic_long_cmpxchg(&user->locked_vm, cur_pages,
+					new_pages) != cur_pages);
+
+	return 0;
+}
+
+static void io_mem_free(void *ptr)
+{
+	struct page *page = virt_to_head_page(ptr);
+
+	if (put_page_testzero(page))
+		free_compound_page(page);
+}
+
+static void *io_mem_alloc(size_t size)
+{
+	gfp_t gfp_flags = GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN | __GFP_COMP |
+				__GFP_NORETRY;
+
+	return (void *) __get_free_pages(gfp_flags, get_order(size));
+}
+
+static unsigned long ring_pages(unsigned sq_entries, unsigned cq_entries)
+{
+	struct io_sq_ring *sq_ring;
+	struct io_cq_ring *cq_ring;
+	size_t bytes;
+
+	bytes = struct_size(sq_ring, array, sq_entries);
+	bytes += array_size(sizeof(struct io_uring_sqe), sq_entries);
+	bytes += struct_size(cq_ring, cqes, cq_entries);
+
+	return (bytes + PAGE_SIZE - 1) / PAGE_SIZE;
+}
+
+static int io_sqe_buffer_unregister(struct io_ring_ctx *ctx)
+{
+	int i, j;
+
+	if (!ctx->user_bufs)
+		return -ENXIO;
+
+	for (i = 0; i < ctx->nr_user_bufs; i++) {
+		struct io_mapped_ubuf *imu = &ctx->user_bufs[i];
+
+		for (j = 0; j < imu->nr_bvecs; j++)
+			put_page(imu->bvec[j].bv_page);
+
+		if (ctx->account_mem)
+			io_unaccount_mem(ctx->user, imu->nr_bvecs);
+		kfree(imu->bvec);
+		imu->nr_bvecs = 0;
+	}
+
+	kfree(ctx->user_bufs);
+	ctx->user_bufs = NULL;
+	ctx->nr_user_bufs = 0;
+	return 0;
+}
+
+static int io_copy_iov(struct io_ring_ctx *ctx, struct iovec *dst,
+		       void __user *arg, unsigned index)
+{
+	struct iovec __user *src;
+
+#ifdef CONFIG_COMPAT
+	if (ctx->compat) {
+		struct compat_iovec __user *ciovs;
+		struct compat_iovec ciov;
+
+		ciovs = (struct compat_iovec __user *) arg;
+		if (copy_from_user(&ciov, &ciovs[index], sizeof(ciov)))
+			return -EFAULT;
+
+		dst->iov_base = (void __user *) (unsigned long) ciov.iov_base;
+		dst->iov_len = ciov.iov_len;
+		return 0;
+	}
+#endif
+	src = (struct iovec __user *) arg;
+	if (copy_from_user(dst, &src[index], sizeof(*dst)))
+		return -EFAULT;
+	return 0;
+}
+
+static int io_sqe_buffer_register(struct io_ring_ctx *ctx, void __user *arg,
+				  unsigned nr_args)
+{
+	struct vm_area_struct **vmas = NULL;
+	struct page **pages = NULL;
+	int i, j, got_pages = 0;
+	int ret = -EINVAL;
+
+	if (ctx->user_bufs)
+		return -EBUSY;
+	if (!nr_args || nr_args > UIO_MAXIOV)
+		return -EINVAL;
+
+	ctx->user_bufs = kcalloc(nr_args, sizeof(struct io_mapped_ubuf),
+					GFP_KERNEL);
+	if (!ctx->user_bufs)
+		return -ENOMEM;
+
+	for (i = 0; i < nr_args; i++) {
+		struct io_mapped_ubuf *imu = &ctx->user_bufs[i];
+		unsigned long off, start, end, ubuf;
+		int pret, nr_pages;
+		struct iovec iov;
+		size_t size;
+
+		ret = io_copy_iov(ctx, &iov, arg, i);
+		if (ret)
+			break;
+
+		/*
+		 * Don't impose further limits on the size and buffer
+		 * constraints here, we'll -EINVAL later when IO is
+		 * submitted if they are wrong.
+		 */
+		ret = -EFAULT;
+		if (!iov.iov_base || !iov.iov_len)
+			goto err;
+
+		/* arbitrary limit, but we need something */
+		if (iov.iov_len > SZ_1G)
+			goto err;
+
+		ubuf = (unsigned long) iov.iov_base;
+		end = (ubuf + iov.iov_len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+		start = ubuf >> PAGE_SHIFT;
+		nr_pages = end - start;
+
+		if (ctx->account_mem) {
+			ret = io_account_mem(ctx->user, nr_pages);
+			if (ret)
+				goto err;
+		}
+
+		ret = 0;
+		if (!pages || nr_pages > got_pages) {
+			kfree(vmas);
+			kfree(pages);
+			pages = kmalloc_array(nr_pages, sizeof(struct page *),
+						GFP_KERNEL);
+			vmas = kmalloc_array(nr_pages,
+					sizeof(struct vm_area_struct *),
+					GFP_KERNEL);
+			if (!pages || !vmas) {
+				ret = -ENOMEM;
+				if (ctx->account_mem)
+					io_unaccount_mem(ctx->user, nr_pages);
+				goto err;
+			}
+			got_pages = nr_pages;
+		}
+
+		imu->bvec = kmalloc_array(nr_pages, sizeof(struct bio_vec),
+						GFP_KERNEL);
+		ret = -ENOMEM;
+		if (!imu->bvec) {
+			if (ctx->account_mem)
+				io_unaccount_mem(ctx->user, nr_pages);
+			goto err;
+		}
+
+		ret = 0;
+		down_read(&current->mm->mmap_sem);
+		pret = get_user_pages_longterm(ubuf, nr_pages, FOLL_WRITE,
+						pages, vmas);
+		if (pret == nr_pages) {
+			/* don't support file backed memory */
+			for (j = 0; j < nr_pages; j++) {
+				struct vm_area_struct *vma = vmas[j];
+
+				if (vma->vm_file &&
+				    !is_file_hugepages(vma->vm_file)) {
+					ret = -EOPNOTSUPP;
+					break;
+				}
+			}
+		} else {
+			ret = pret < 0 ? pret : -EFAULT;
+		}
+		up_read(&current->mm->mmap_sem);
+		if (ret) {
+			/*
+			 * if we did partial map, or found file backed vmas,
+			 * release any pages we did get
+			 */
+			if (pret > 0) {
+				for (j = 0; j < pret; j++)
+					put_page(pages[j]);
+			}
+			if (ctx->account_mem)
+				io_unaccount_mem(ctx->user, nr_pages);
+			goto err;
+		}
+
+		off = ubuf & ~PAGE_MASK;
+		size = iov.iov_len;
+		for (j = 0; j < nr_pages; j++) {
+			size_t vec_len;
+
+			vec_len = min_t(size_t, size, PAGE_SIZE - off);
+			imu->bvec[j].bv_page = pages[j];
+			imu->bvec[j].bv_len = vec_len;
+			imu->bvec[j].bv_offset = off;
+			off = 0;
+			size -= vec_len;
+		}
+		/* store original address for later verification */
+		imu->ubuf = ubuf;
+		imu->len = iov.iov_len;
+		imu->nr_bvecs = nr_pages;
+
+		ctx->nr_user_bufs++;
+	}
+	kfree(pages);
+	kfree(vmas);
+	return 0;
+err:
+	kfree(pages);
+	kfree(vmas);
+	io_sqe_buffer_unregister(ctx);
+	return ret;
+}
+
+static void io_ring_ctx_free(struct io_ring_ctx *ctx)
+{
+	io_finish_async(ctx);
+	if (ctx->sqo_mm)
+		mmdrop(ctx->sqo_mm);
+
+	io_iopoll_reap_events(ctx);
+	io_sqe_buffer_unregister(ctx);
+	io_sqe_files_unregister(ctx);
+
+#if defined(CONFIG_UNIX)
+	if (ctx->ring_sock)
+		sock_release(ctx->ring_sock);
+#endif
+
+	io_mem_free(ctx->sq_ring);
+	io_mem_free(ctx->sq_sqes);
+	io_mem_free(ctx->cq_ring);
+
+	percpu_ref_exit(&ctx->refs);
+	if (ctx->account_mem)
+		io_unaccount_mem(ctx->user,
+				ring_pages(ctx->sq_entries, ctx->cq_entries));
+	free_uid(ctx->user);
+	kfree(ctx);
+}
+
+static __poll_t io_uring_poll(struct file *file, poll_table *wait)
+{
+	struct io_ring_ctx *ctx = file->private_data;
+	__poll_t mask = 0;
+
+	poll_wait(file, &ctx->cq_wait, wait);
+	/* See comment at the top of this file */
+	smp_rmb();
+	if (READ_ONCE(ctx->sq_ring->r.tail) + 1 != ctx->cached_sq_head)
+		mask |= EPOLLOUT | EPOLLWRNORM;
+	if (READ_ONCE(ctx->cq_ring->r.head) != ctx->cached_cq_tail)
+		mask |= EPOLLIN | EPOLLRDNORM;
+
+	return mask;
+}
+
+static int io_uring_fasync(int fd, struct file *file, int on)
+{
+	struct io_ring_ctx *ctx = file->private_data;
+
+	return fasync_helper(fd, file, on, &ctx->cq_fasync);
+}
+
+static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx)
+{
+	mutex_lock(&ctx->uring_lock);
+	percpu_ref_kill(&ctx->refs);
+	mutex_unlock(&ctx->uring_lock);
+
+	io_poll_remove_all(ctx);
+	io_iopoll_reap_events(ctx);
+	wait_for_completion(&ctx->ctx_done);
+	io_ring_ctx_free(ctx);
+}
+
+static int io_uring_release(struct inode *inode, struct file *file)
+{
+	struct io_ring_ctx *ctx = file->private_data;
+
+	file->private_data = NULL;
+	io_ring_ctx_wait_and_kill(ctx);
+	return 0;
+}
+
+static int io_uring_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	loff_t offset = (loff_t) vma->vm_pgoff << PAGE_SHIFT;
+	unsigned long sz = vma->vm_end - vma->vm_start;
+	struct io_ring_ctx *ctx = file->private_data;
+	unsigned long pfn;
+	struct page *page;
+	void *ptr;
+
+	switch (offset) {
+	case IORING_OFF_SQ_RING:
+		ptr = ctx->sq_ring;
+		break;
+	case IORING_OFF_SQES:
+		ptr = ctx->sq_sqes;
+		break;
+	case IORING_OFF_CQ_RING:
+		ptr = ctx->cq_ring;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	page = virt_to_head_page(ptr);
+	if (sz > (PAGE_SIZE << compound_order(page)))
+		return -EINVAL;
+
+	pfn = virt_to_phys(ptr) >> PAGE_SHIFT;
+	return remap_pfn_range(vma, vma->vm_start, pfn, sz, vma->vm_page_prot);
+}
+
+SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
+		u32, min_complete, u32, flags, const sigset_t __user *, sig,
+		size_t, sigsz)
+{
+	struct io_ring_ctx *ctx;
+	long ret = -EBADF;
+	int submitted = 0;
+	struct fd f;
+
+	if (flags & ~(IORING_ENTER_GETEVENTS | IORING_ENTER_SQ_WAKEUP))
+		return -EINVAL;
+
+	f = fdget(fd);
+	if (!f.file)
+		return -EBADF;
+
+	ret = -EOPNOTSUPP;
+	if (f.file->f_op != &io_uring_fops)
+		goto out_fput;
+
+	ret = -ENXIO;
+	ctx = f.file->private_data;
+	if (!percpu_ref_tryget(&ctx->refs))
+		goto out_fput;
+
+	/*
+	 * For SQ polling, the thread will do all submissions and completions.
+	 * Just return the requested submit count, and wake the thread if
+	 * we were asked to.
+	 */
+	if (ctx->flags & IORING_SETUP_SQPOLL) {
+		if (flags & IORING_ENTER_SQ_WAKEUP)
+			wake_up(&ctx->sqo_wait);
+		submitted = to_submit;
+		goto out_ctx;
+	}
+
+	ret = 0;
+	if (to_submit) {
+		to_submit = min(to_submit, ctx->sq_entries);
+
+		mutex_lock(&ctx->uring_lock);
+		submitted = io_ring_submit(ctx, to_submit);
+		mutex_unlock(&ctx->uring_lock);
+
+		if (submitted < 0)
+			goto out_ctx;
+	}
+	if (flags & IORING_ENTER_GETEVENTS) {
+		unsigned nr_events = 0;
+
+		min_complete = min(min_complete, ctx->cq_entries);
+
+		/*
+		 * The application could have included the 'to_submit' count
+		 * in how many events it wanted to wait for. If we failed to
+		 * submit the desired count, we may need to adjust the number
+		 * of events to poll/wait for.
+		 */
+		if (submitted < to_submit)
+			min_complete = min_t(unsigned, submitted, min_complete);
+
+		if (ctx->flags & IORING_SETUP_IOPOLL) {
+			mutex_lock(&ctx->uring_lock);
+			ret = io_iopoll_check(ctx, &nr_events, min_complete);
+			mutex_unlock(&ctx->uring_lock);
+		} else {
+			ret = io_cqring_wait(ctx, min_complete, sig, sigsz);
+		}
+	}
+
+out_ctx:
+	io_ring_drop_ctx_refs(ctx, 1);
+out_fput:
+	fdput(f);
+	return submitted ? submitted : ret;
+}
+
+static const struct file_operations io_uring_fops = {
+	.release	= io_uring_release,
+	.mmap		= io_uring_mmap,
+	.poll		= io_uring_poll,
+	.fasync		= io_uring_fasync,
+};
+
+static int io_allocate_scq_urings(struct io_ring_ctx *ctx,
+				  struct io_uring_params *p)
+{
+	struct io_sq_ring *sq_ring;
+	struct io_cq_ring *cq_ring;
+	size_t size;
+
+	sq_ring = io_mem_alloc(struct_size(sq_ring, array, p->sq_entries));
+	if (!sq_ring)
+		return -ENOMEM;
+
+	ctx->sq_ring = sq_ring;
+	sq_ring->ring_mask = p->sq_entries - 1;
+	sq_ring->ring_entries = p->sq_entries;
+	ctx->sq_mask = sq_ring->ring_mask;
+	ctx->sq_entries = sq_ring->ring_entries;
+
+	size = array_size(sizeof(struct io_uring_sqe), p->sq_entries);
+	if (size == SIZE_MAX)
+		return -EOVERFLOW;
+
+	ctx->sq_sqes = io_mem_alloc(size);
+	if (!ctx->sq_sqes) {
+		io_mem_free(ctx->sq_ring);
+		return -ENOMEM;
+	}
+
+	cq_ring = io_mem_alloc(struct_size(cq_ring, cqes, p->cq_entries));
+	if (!cq_ring) {
+		io_mem_free(ctx->sq_ring);
+		io_mem_free(ctx->sq_sqes);
+		return -ENOMEM;
+	}
+
+	ctx->cq_ring = cq_ring;
+	cq_ring->ring_mask = p->cq_entries - 1;
+	cq_ring->ring_entries = p->cq_entries;
+	ctx->cq_mask = cq_ring->ring_mask;
+	ctx->cq_entries = cq_ring->ring_entries;
+	return 0;
+}
+
+/*
+ * Allocate an anonymous fd, this is what constitutes the application
+ * visible backing of an io_uring instance. The application mmaps this
+ * fd to gain access to the SQ/CQ ring details. If UNIX sockets are enabled,
+ * we have to tie this fd to a socket for file garbage collection purposes.
+ */
+static int io_uring_get_fd(struct io_ring_ctx *ctx)
+{
+	struct file *file;
+	int ret;
+
+#if defined(CONFIG_UNIX)
+	ret = sock_create_kern(&init_net, PF_UNIX, SOCK_RAW, IPPROTO_IP,
+				&ctx->ring_sock);
+	if (ret)
+		return ret;
+#endif
+
+	ret = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
+	if (ret < 0)
+		goto err;
+
+	file = anon_inode_getfile("[io_uring]", &io_uring_fops, ctx,
+					O_RDWR | O_CLOEXEC);
+	if (IS_ERR(file)) {
+		put_unused_fd(ret);
+		ret = PTR_ERR(file);
+		goto err;
+	}
+
+#if defined(CONFIG_UNIX)
+	ctx->ring_sock->file = file;
+	ctx->ring_sock->sk->sk_user_data = ctx;
+#endif
+	fd_install(ret, file);
+	return ret;
+err:
+#if defined(CONFIG_UNIX)
+	sock_release(ctx->ring_sock);
+	ctx->ring_sock = NULL;
+#endif
+	return ret;
+}
+
+static int io_uring_create(unsigned entries, struct io_uring_params *p)
+{
+	struct user_struct *user = NULL;
+	struct io_ring_ctx *ctx;
+	bool account_mem;
+	int ret;
+
+	if (!entries || entries > IORING_MAX_ENTRIES)
+		return -EINVAL;
+
+	/*
+	 * Use twice as many entries for the CQ ring. It's possible for the
+	 * application to drive a higher depth than the size of the SQ ring,
+	 * since the sqes are only used at submission time. This allows for
+	 * some flexibility in overcommitting a bit.
+	 */
+	p->sq_entries = roundup_pow_of_two(entries);
+	p->cq_entries = 2 * p->sq_entries;
+
+	user = get_uid(current_user());
+	account_mem = !capable(CAP_IPC_LOCK);
+
+	if (account_mem) {
+		ret = io_account_mem(user,
+				ring_pages(p->sq_entries, p->cq_entries));
+		if (ret) {
+			free_uid(user);
+			return ret;
+		}
+	}
+
+	ctx = io_ring_ctx_alloc(p);
+	if (!ctx) {
+		if (account_mem)
+			io_unaccount_mem(user, ring_pages(p->sq_entries,
+								p->cq_entries));
+		free_uid(user);
+		return -ENOMEM;
+	}
+	ctx->compat = in_compat_syscall();
+	ctx->account_mem = account_mem;
+	ctx->user = user;
+
+	ret = io_allocate_scq_urings(ctx, p);
+	if (ret)
+		goto err;
+
+	ret = io_sq_offload_start(ctx, p);
+	if (ret)
+		goto err;
+
+	ret = io_uring_get_fd(ctx);
+	if (ret < 0)
+		goto err;
+
+	memset(&p->sq_off, 0, sizeof(p->sq_off));
+	p->sq_off.head = offsetof(struct io_sq_ring, r.head);
+	p->sq_off.tail = offsetof(struct io_sq_ring, r.tail);
+	p->sq_off.ring_mask = offsetof(struct io_sq_ring, ring_mask);
+	p->sq_off.ring_entries = offsetof(struct io_sq_ring, ring_entries);
+	p->sq_off.flags = offsetof(struct io_sq_ring, flags);
+	p->sq_off.dropped = offsetof(struct io_sq_ring, dropped);
+	p->sq_off.array = offsetof(struct io_sq_ring, array);
+
+	memset(&p->cq_off, 0, sizeof(p->cq_off));
+	p->cq_off.head = offsetof(struct io_cq_ring, r.head);
+	p->cq_off.tail = offsetof(struct io_cq_ring, r.tail);
+	p->cq_off.ring_mask = offsetof(struct io_cq_ring, ring_mask);
+	p->cq_off.ring_entries = offsetof(struct io_cq_ring, ring_entries);
+	p->cq_off.overflow = offsetof(struct io_cq_ring, overflow);
+	p->cq_off.cqes = offsetof(struct io_cq_ring, cqes);
+	return ret;
+err:
+	io_ring_ctx_wait_and_kill(ctx);
+	return ret;
+}
+
+/*
+ * Sets up an aio uring context, and returns the fd. Applications asks for a
+ * ring size, we return the actual sq/cq ring sizes (among other things) in the
+ * params structure passed in.
+ */
+static long io_uring_setup(u32 entries, struct io_uring_params __user *params)
+{
+	struct io_uring_params p;
+	long ret;
+	int i;
+
+	if (copy_from_user(&p, params, sizeof(p)))
+		return -EFAULT;
+	for (i = 0; i < ARRAY_SIZE(p.resv); i++) {
+		if (p.resv[i])
+			return -EINVAL;
+	}
+
+	if (p.flags & ~(IORING_SETUP_IOPOLL | IORING_SETUP_SQPOLL |
+			IORING_SETUP_SQ_AFF))
+		return -EINVAL;
+
+	ret = io_uring_create(entries, &p);
+	if (ret < 0)
+		return ret;
+
+	if (copy_to_user(params, &p, sizeof(p)))
+		return -EFAULT;
+
+	return ret;
+}
+
+SYSCALL_DEFINE2(io_uring_setup, u32, entries,
+		struct io_uring_params __user *, params)
+{
+	return io_uring_setup(entries, params);
+}
+
+static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
+			       void __user *arg, unsigned nr_args)
+{
+	int ret;
+
+	percpu_ref_kill(&ctx->refs);
+	wait_for_completion(&ctx->ctx_done);
+
+	switch (opcode) {
+	case IORING_REGISTER_BUFFERS:
+		ret = io_sqe_buffer_register(ctx, arg, nr_args);
+		break;
+	case IORING_UNREGISTER_BUFFERS:
+		ret = -EINVAL;
+		if (arg || nr_args)
+			break;
+		ret = io_sqe_buffer_unregister(ctx);
+		break;
+	case IORING_REGISTER_FILES:
+		ret = io_sqe_files_register(ctx, arg, nr_args);
+		break;
+	case IORING_UNREGISTER_FILES:
+		ret = -EINVAL;
+		if (arg || nr_args)
+			break;
+		ret = io_sqe_files_unregister(ctx);
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	/* bring the ctx back to life */
+	reinit_completion(&ctx->ctx_done);
+	percpu_ref_reinit(&ctx->refs);
+	return ret;
+}
+
+SYSCALL_DEFINE4(io_uring_register, unsigned int, fd, unsigned int, opcode,
+		void __user *, arg, unsigned int, nr_args)
+{
+	struct io_ring_ctx *ctx;
+	long ret = -EBADF;
+	struct fd f;
+
+	f = fdget(fd);
+	if (!f.file)
+		return -EBADF;
+
+	ret = -EOPNOTSUPP;
+	if (f.file->f_op != &io_uring_fops)
+		goto out_fput;
+
+	ctx = f.file->private_data;
+
+	mutex_lock(&ctx->uring_lock);
+	ret = __io_uring_register(ctx, opcode, arg, nr_args);
+	mutex_unlock(&ctx->uring_lock);
+out_fput:
+	fdput(f);
+	return ret;
+}
+
+static int __init io_uring_init(void)
+{
+	req_cachep = KMEM_CACHE(io_kiocb, SLAB_HWCACHE_ALIGN | SLAB_PANIC);
+	return 0;
+};
+__initcall(io_uring_init);