1/*
   2 *	An async IO implementation for Linux
   3 *	Written by Benjamin LaHaise <bcrl@kvack.org>
   4 *
   5 *	Implements an efficient asynchronous io interface.
   6 *
   7 *	Copyright 2000, 2001, 2002 Red Hat, Inc.  All Rights Reserved.
   8 *
   9 *	See ../COPYING for licensing terms.
  10 */
  11#define pr_fmt(fmt) "%s: " fmt, __func__
  12
  13#include <linux/kernel.h>
  14#include <linux/init.h>
  15#include <linux/errno.h>
  16#include <linux/time.h>
  17#include <linux/aio_abi.h>
  18#include <linux/export.h>
  19#include <linux/syscalls.h>
  20#include <linux/backing-dev.h>
  21#include <linux/uio.h>
  22
  23#include <linux/sched.h>
  24#include <linux/fs.h>
  25#include <linux/file.h>
  26#include <linux/mm.h>
  27#include <linux/mman.h>
  28#include <linux/mmu_context.h>
  29#include <linux/percpu.h>
  30#include <linux/slab.h>
  31#include <linux/timer.h>
  32#include <linux/aio.h>
  33#include <linux/highmem.h>
  34#include <linux/workqueue.h>
  35#include <linux/security.h>
  36#include <linux/eventfd.h>
  37#include <linux/blkdev.h>
  38#include <linux/compat.h>
  39#include <linux/migrate.h>
  40#include <linux/ramfs.h>
  41#include <linux/percpu-refcount.h>
  42#include <linux/mount.h>
  43
  44#include <asm/kmap_types.h>
  45#include <asm/uaccess.h>
  46
  47#include "internal.h"
  48
  49#define AIO_RING_MAGIC			0xa10a10a1
  50#define AIO_RING_COMPAT_FEATURES	1
  51#define AIO_RING_INCOMPAT_FEATURES	0
  52struct aio_ring {
  53	unsigned	id;	/* kernel internal index number */
  54	unsigned	nr;	/* number of io_events */
  55	unsigned	head;	/* Written to by userland or under ring_lock
  56				 * mutex by aio_read_events_ring(). */
  57	unsigned	tail;
  58
  59	unsigned	magic;
  60	unsigned	compat_features;
  61	unsigned	incompat_features;
  62	unsigned	header_length;	/* size of aio_ring */
  63
  64
  65	struct io_event		io_events[0];
  66}; /* 128 bytes + ring size */
  67
  68#define AIO_RING_PAGES	8
  69
  70struct kioctx_table {
  71	struct rcu_head	rcu;
  72	unsigned	nr;
  73	struct kioctx	*table[];
  74};
  75
  76struct kioctx_cpu {
  77	unsigned		reqs_available;
  78};
  79
  80struct ctx_rq_wait {
  81	struct completion comp;
  82	atomic_t count;
  83};
  84
  85struct kioctx {
  86	struct percpu_ref	users;
  87	atomic_t		dead;
  88
  89	struct percpu_ref	reqs;
  90
  91	unsigned long		user_id;
  92
  93	struct __percpu kioctx_cpu *cpu;
  94
  95	/*
  96	 * For percpu reqs_available, number of slots we move to/from global
  97	 * counter at a time:
  98	 */
  99	unsigned		req_batch;
 100	/*
 101	 * This is what userspace passed to io_setup(), it's not used for
 102	 * anything but counting against the global max_reqs quota.
 103	 *
 104	 * The real limit is nr_events - 1, which will be larger (see
 105	 * aio_setup_ring())
 106	 */
 107	unsigned		max_reqs;
 108
 109	/* Size of ringbuffer, in units of struct io_event */
 110	unsigned		nr_events;
 111
 112	unsigned long		mmap_base;
 113	unsigned long		mmap_size;
 114
 115	struct page		**ring_pages;
 116	long			nr_pages;
 117
 118	struct work_struct	free_work;
 119
 120	/*
 121	 * signals when all in-flight requests are done
 122	 */
 123	struct ctx_rq_wait	*rq_wait;
 124
 125	struct {
 126		/*
 127		 * This counts the number of available slots in the ringbuffer,
 128		 * so we avoid overflowing it: it's decremented (if positive)
 129		 * when allocating a kiocb and incremented when the resulting
 130		 * io_event is pulled off the ringbuffer.
 131		 *
 132		 * We batch accesses to it with a percpu version.
 133		 */
 134		atomic_t	reqs_available;
 135	} ____cacheline_aligned_in_smp;
 136
 137	struct {
 138		spinlock_t	ctx_lock;
 139		struct list_head active_reqs;	/* used for cancellation */
 140	} ____cacheline_aligned_in_smp;
 141
 142	struct {
 143		struct mutex	ring_lock;
 144		wait_queue_head_t wait;
 145	} ____cacheline_aligned_in_smp;
 146
 147	struct {
 148		unsigned	tail;
 149		unsigned	completed_events;
 150		spinlock_t	completion_lock;
 151	} ____cacheline_aligned_in_smp;
 152
 153	struct page		*internal_pages[AIO_RING_PAGES];
 154	struct file		*aio_ring_file;
 155
 156	unsigned		id;
 157};
 158
 159/*
 160 * We use ki_cancel == KIOCB_CANCELLED to indicate that a kiocb has been either
 161 * cancelled or completed (this makes a certain amount of sense because
 162 * successful cancellation - io_cancel() - does deliver the completion to
 163 * userspace).
 164 *
 165 * And since most things don't implement kiocb cancellation and we'd really like
 166 * kiocb completion to be lockless when possible, we use ki_cancel to
 167 * synchronize cancellation and completion - we only set it to KIOCB_CANCELLED
 168 * with xchg() or cmpxchg(), see batch_complete_aio() and kiocb_cancel().
 169 */
 170#define KIOCB_CANCELLED		((void *) (~0ULL))
 171
 172struct aio_kiocb {
 173	struct kiocb		common;
 174
 175	struct kioctx		*ki_ctx;
 176	kiocb_cancel_fn		*ki_cancel;
 177
 178	struct iocb __user	*ki_user_iocb;	/* user's aiocb */
 179	__u64			ki_user_data;	/* user's data for completion */
 180
 181	struct list_head	ki_list;	/* the aio core uses this
 182						 * for cancellation */
 183
 184	/*
 185	 * If the aio_resfd field of the userspace iocb is not zero,
 186	 * this is the underlying eventfd context to deliver events to.
 187	 */
 188	struct eventfd_ctx	*ki_eventfd;
 189};
 190
 191/*------ sysctl variables----*/
 192static DEFINE_SPINLOCK(aio_nr_lock);
 193unsigned long aio_nr;		/* current system wide number of aio requests */
 194unsigned long aio_max_nr = 0x10000; /* system wide maximum number of aio requests */
 195/*----end sysctl variables---*/
 196
 197static struct kmem_cache	*kiocb_cachep;
 198static struct kmem_cache	*kioctx_cachep;
 199
 200static struct vfsmount *aio_mnt;
 201
 202static const struct file_operations aio_ring_fops;
 203static const struct address_space_operations aio_ctx_aops;
 204
 205static struct file *aio_private_file(struct kioctx *ctx, loff_t nr_pages)
 206{
 207	struct qstr this = QSTR_INIT("[aio]", 5);
 208	struct file *file;
 209	struct path path;
 210	struct inode *inode = alloc_anon_inode(aio_mnt->mnt_sb);
 211	if (IS_ERR(inode))
 212		return ERR_CAST(inode);
 213
 214	inode->i_mapping->a_ops = &aio_ctx_aops;
 215	inode->i_mapping->private_data = ctx;
 216	inode->i_size = PAGE_SIZE * nr_pages;
 217
 218	path.dentry = d_alloc_pseudo(aio_mnt->mnt_sb, &this);
 219	if (!path.dentry) {
 220		iput(inode);
 221		return ERR_PTR(-ENOMEM);
 222	}
 223	path.mnt = mntget(aio_mnt);
 224
 225	d_instantiate(path.dentry, inode);
 226	file = alloc_file(&path, FMODE_READ | FMODE_WRITE, &aio_ring_fops);
 227	if (IS_ERR(file)) {
 228		path_put(&path);
 229		return file;
 230	}
 231
 232	file->f_flags = O_RDWR;
 
 233	return file;
 234}
 235
 236static struct dentry *aio_mount(struct file_system_type *fs_type,
 237				int flags, const char *dev_name, void *data)
 238{
 239	static const struct dentry_operations ops = {
 240		.d_dname	= simple_dname,
 241	};
 242	return mount_pseudo(fs_type, "aio:", NULL, &ops, AIO_RING_MAGIC);
 243}
 244
 245/* aio_setup
 246 *	Creates the slab caches used by the aio routines, panic on
 247 *	failure as this is done early during the boot sequence.
 248 */
 249static int __init aio_setup(void)
 250{
 251	static struct file_system_type aio_fs = {
 252		.name		= "aio",
 253		.mount		= aio_mount,
 254		.kill_sb	= kill_anon_super,
 255	};
 256	aio_mnt = kern_mount(&aio_fs);
 257	if (IS_ERR(aio_mnt))
 258		panic("Failed to create aio fs mount.");
 259
 260	kiocb_cachep = KMEM_CACHE(aio_kiocb, SLAB_HWCACHE_ALIGN|SLAB_PANIC);
 261	kioctx_cachep = KMEM_CACHE(kioctx,SLAB_HWCACHE_ALIGN|SLAB_PANIC);
 262
 263	pr_debug("sizeof(struct page) = %zu\n", sizeof(struct page));
 264
 265	return 0;
 266}
 267__initcall(aio_setup);
 268
 269static void put_aio_ring_file(struct kioctx *ctx)
 270{
 271	struct file *aio_ring_file = ctx->aio_ring_file;
 272	if (aio_ring_file) {
 273		truncate_setsize(aio_ring_file->f_inode, 0);
 274
 275		/* Prevent further access to the kioctx from migratepages */
 276		spin_lock(&aio_ring_file->f_inode->i_mapping->private_lock);
 277		aio_ring_file->f_inode->i_mapping->private_data = NULL;
 278		ctx->aio_ring_file = NULL;
 279		spin_unlock(&aio_ring_file->f_inode->i_mapping->private_lock);
 280
 281		fput(aio_ring_file);
 282	}
 283}
 284
 285static void aio_free_ring(struct kioctx *ctx)
 286{
 287	int i;
 288
 289	/* Disconnect the kiotx from the ring file.  This prevents future
 290	 * accesses to the kioctx from page migration.
 291	 */
 292	put_aio_ring_file(ctx);
 293
 294	for (i = 0; i < ctx->nr_pages; i++) {
 295		struct page *page;
 296		pr_debug("pid(%d) [%d] page->count=%d\n", current->pid, i,
 297				page_count(ctx->ring_pages[i]));
 298		page = ctx->ring_pages[i];
 299		if (!page)
 300			continue;
 301		ctx->ring_pages[i] = NULL;
 302		put_page(page);
 303	}
 304
 305	if (ctx->ring_pages && ctx->ring_pages != ctx->internal_pages) {
 306		kfree(ctx->ring_pages);
 307		ctx->ring_pages = NULL;
 308	}
 309}
 310
 311static int aio_ring_mremap(struct vm_area_struct *vma)
 312{
 313	struct file *file = vma->vm_file;
 314	struct mm_struct *mm = vma->vm_mm;
 315	struct kioctx_table *table;
 316	int i, res = -EINVAL;
 317
 318	spin_lock(&mm->ioctx_lock);
 319	rcu_read_lock();
 320	table = rcu_dereference(mm->ioctx_table);
 321	for (i = 0; i < table->nr; i++) {
 322		struct kioctx *ctx;
 323
 324		ctx = table->table[i];
 325		if (ctx && ctx->aio_ring_file == file) {
 326			if (!atomic_read(&ctx->dead)) {
 327				ctx->user_id = ctx->mmap_base = vma->vm_start;
 328				res = 0;
 329			}
 330			break;
 331		}
 332	}
 333
 334	rcu_read_unlock();
 335	spin_unlock(&mm->ioctx_lock);
 336	return res;
 337}
 338
 339static const struct vm_operations_struct aio_ring_vm_ops = {
 340	.mremap		= aio_ring_mremap,
 341#if IS_ENABLED(CONFIG_MMU)
 342	.fault		= filemap_fault,
 343	.map_pages	= filemap_map_pages,
 344	.page_mkwrite	= filemap_page_mkwrite,
 345#endif
 346};
 347
 348static int aio_ring_mmap(struct file *file, struct vm_area_struct *vma)
 349{
 350	vma->vm_flags |= VM_DONTEXPAND;
 351	vma->vm_ops = &aio_ring_vm_ops;
 352	return 0;
 353}
 354
 355static const struct file_operations aio_ring_fops = {
 356	.mmap = aio_ring_mmap,
 357};
 358
 
 
 
 
 
 359#if IS_ENABLED(CONFIG_MIGRATION)
 360static int aio_migratepage(struct address_space *mapping, struct page *new,
 361			struct page *old, enum migrate_mode mode)
 362{
 363	struct kioctx *ctx;
 364	unsigned long flags;
 365	pgoff_t idx;
 366	int rc;
 367
 368	rc = 0;
 369
 370	/* mapping->private_lock here protects against the kioctx teardown.  */
 371	spin_lock(&mapping->private_lock);
 372	ctx = mapping->private_data;
 373	if (!ctx) {
 374		rc = -EINVAL;
 375		goto out;
 376	}
 377
 378	/* The ring_lock mutex.  The prevents aio_read_events() from writing
 379	 * to the ring's head, and prevents page migration from mucking in
 380	 * a partially initialized kiotx.
 381	 */
 382	if (!mutex_trylock(&ctx->ring_lock)) {
 383		rc = -EAGAIN;
 384		goto out;
 385	}
 386
 387	idx = old->index;
 388	if (idx < (pgoff_t)ctx->nr_pages) {
 389		/* Make sure the old page hasn't already been changed */
 390		if (ctx->ring_pages[idx] != old)
 391			rc = -EAGAIN;
 392	} else
 393		rc = -EINVAL;
 394
 395	if (rc != 0)
 396		goto out_unlock;
 397
 398	/* Writeback must be complete */
 399	BUG_ON(PageWriteback(old));
 400	get_page(new);
 401
 402	rc = migrate_page_move_mapping(mapping, new, old, NULL, mode, 1);
 403	if (rc != MIGRATEPAGE_SUCCESS) {
 404		put_page(new);
 405		goto out_unlock;
 406	}
 407
 408	/* Take completion_lock to prevent other writes to the ring buffer
 409	 * while the old page is copied to the new.  This prevents new
 410	 * events from being lost.
 411	 */
 412	spin_lock_irqsave(&ctx->completion_lock, flags);
 413	migrate_page_copy(new, old);
 414	BUG_ON(ctx->ring_pages[idx] != old);
 415	ctx->ring_pages[idx] = new;
 416	spin_unlock_irqrestore(&ctx->completion_lock, flags);
 417
 418	/* The old page is no longer accessible. */
 419	put_page(old);
 420
 421out_unlock:
 422	mutex_unlock(&ctx->ring_lock);
 423out:
 424	spin_unlock(&mapping->private_lock);
 425	return rc;
 426}
 427#endif
 428
 429static const struct address_space_operations aio_ctx_aops = {
 430	.set_page_dirty = __set_page_dirty_no_writeback,
 431#if IS_ENABLED(CONFIG_MIGRATION)
 432	.migratepage	= aio_migratepage,
 433#endif
 434};
 435
 436static int aio_setup_ring(struct kioctx *ctx)
 437{
 438	struct aio_ring *ring;
 439	unsigned nr_events = ctx->max_reqs;
 440	struct mm_struct *mm = current->mm;
 441	unsigned long size, unused;
 442	int nr_pages;
 443	int i;
 444	struct file *file;
 445
 446	/* Compensate for the ring buffer's head/tail overlap entry */
 447	nr_events += 2;	/* 1 is required, 2 for good luck */
 448
 449	size = sizeof(struct aio_ring);
 450	size += sizeof(struct io_event) * nr_events;
 451
 452	nr_pages = PFN_UP(size);
 453	if (nr_pages < 0)
 454		return -EINVAL;
 455
 456	file = aio_private_file(ctx, nr_pages);
 457	if (IS_ERR(file)) {
 458		ctx->aio_ring_file = NULL;
 459		return -ENOMEM;
 460	}
 461
 462	ctx->aio_ring_file = file;
 463	nr_events = (PAGE_SIZE * nr_pages - sizeof(struct aio_ring))
 464			/ sizeof(struct io_event);
 465
 466	ctx->ring_pages = ctx->internal_pages;
 467	if (nr_pages > AIO_RING_PAGES) {
 468		ctx->ring_pages = kcalloc(nr_pages, sizeof(struct page *),
 469					  GFP_KERNEL);
 470		if (!ctx->ring_pages) {
 471			put_aio_ring_file(ctx);
 472			return -ENOMEM;
 473		}
 474	}
 475
 476	for (i = 0; i < nr_pages; i++) {
 477		struct page *page;
 478		page = find_or_create_page(file->f_inode->i_mapping,
 479					   i, GFP_HIGHUSER | __GFP_ZERO);
 480		if (!page)
 481			break;
 482		pr_debug("pid(%d) page[%d]->count=%d\n",
 483			 current->pid, i, page_count(page));
 484		SetPageUptodate(page);
 
 485		unlock_page(page);
 486
 487		ctx->ring_pages[i] = page;
 488	}
 489	ctx->nr_pages = i;
 490
 491	if (unlikely(i != nr_pages)) {
 492		aio_free_ring(ctx);
 493		return -ENOMEM;
 494	}
 495
 496	ctx->mmap_size = nr_pages * PAGE_SIZE;
 497	pr_debug("attempting mmap of %lu bytes\n", ctx->mmap_size);
 498
 499	down_write(&mm->mmap_sem);
 500	ctx->mmap_base = do_mmap_pgoff(ctx->aio_ring_file, 0, ctx->mmap_size,
 501				       PROT_READ | PROT_WRITE,
 502				       MAP_SHARED, 0, &unused);
 503	up_write(&mm->mmap_sem);
 504	if (IS_ERR((void *)ctx->mmap_base)) {
 505		ctx->mmap_size = 0;
 506		aio_free_ring(ctx);
 507		return -ENOMEM;
 508	}
 509
 510	pr_debug("mmap address: 0x%08lx\n", ctx->mmap_base);
 511
 512	ctx->user_id = ctx->mmap_base;
 513	ctx->nr_events = nr_events; /* trusted copy */
 514
 515	ring = kmap_atomic(ctx->ring_pages[0]);
 516	ring->nr = nr_events;	/* user copy */
 517	ring->id = ~0U;
 518	ring->head = ring->tail = 0;
 519	ring->magic = AIO_RING_MAGIC;
 520	ring->compat_features = AIO_RING_COMPAT_FEATURES;
 521	ring->incompat_features = AIO_RING_INCOMPAT_FEATURES;
 522	ring->header_length = sizeof(struct aio_ring);
 523	kunmap_atomic(ring);
 524	flush_dcache_page(ctx->ring_pages[0]);
 525
 526	return 0;
 527}
 528
 529#define AIO_EVENTS_PER_PAGE	(PAGE_SIZE / sizeof(struct io_event))
 530#define AIO_EVENTS_FIRST_PAGE	((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event))
 531#define AIO_EVENTS_OFFSET	(AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE)
 532
 533void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel)
 534{
 535	struct aio_kiocb *req = container_of(iocb, struct aio_kiocb, common);
 536	struct kioctx *ctx = req->ki_ctx;
 537	unsigned long flags;
 538
 539	spin_lock_irqsave(&ctx->ctx_lock, flags);
 540
 541	if (!req->ki_list.next)
 542		list_add(&req->ki_list, &ctx->active_reqs);
 543
 544	req->ki_cancel = cancel;
 545
 546	spin_unlock_irqrestore(&ctx->ctx_lock, flags);
 547}
 548EXPORT_SYMBOL(kiocb_set_cancel_fn);
 549
 550static int kiocb_cancel(struct aio_kiocb *kiocb)
 551{
 552	kiocb_cancel_fn *old, *cancel;
 553
 554	/*
 555	 * Don't want to set kiocb->ki_cancel = KIOCB_CANCELLED unless it
 556	 * actually has a cancel function, hence the cmpxchg()
 557	 */
 558
 559	cancel = ACCESS_ONCE(kiocb->ki_cancel);
 560	do {
 561		if (!cancel || cancel == KIOCB_CANCELLED)
 562			return -EINVAL;
 563
 564		old = cancel;
 565		cancel = cmpxchg(&kiocb->ki_cancel, old, KIOCB_CANCELLED);
 566	} while (cancel != old);
 567
 568	return cancel(&kiocb->common);
 569}
 570
 571static void free_ioctx(struct work_struct *work)
 572{
 573	struct kioctx *ctx = container_of(work, struct kioctx, free_work);
 574
 575	pr_debug("freeing %p\n", ctx);
 576
 577	aio_free_ring(ctx);
 578	free_percpu(ctx->cpu);
 579	percpu_ref_exit(&ctx->reqs);
 580	percpu_ref_exit(&ctx->users);
 581	kmem_cache_free(kioctx_cachep, ctx);
 582}
 583
 584static void free_ioctx_reqs(struct percpu_ref *ref)
 585{
 586	struct kioctx *ctx = container_of(ref, struct kioctx, reqs);
 587
 588	/* At this point we know that there are no any in-flight requests */
 589	if (ctx->rq_wait && atomic_dec_and_test(&ctx->rq_wait->count))
 590		complete(&ctx->rq_wait->comp);
 591
 592	INIT_WORK(&ctx->free_work, free_ioctx);
 593	schedule_work(&ctx->free_work);
 594}
 595
 596/*
 597 * When this function runs, the kioctx has been removed from the "hash table"
 598 * and ctx->users has dropped to 0, so we know no more kiocbs can be submitted -
 599 * now it's safe to cancel any that need to be.
 600 */
 601static void free_ioctx_users(struct percpu_ref *ref)
 602{
 603	struct kioctx *ctx = container_of(ref, struct kioctx, users);
 604	struct aio_kiocb *req;
 605
 606	spin_lock_irq(&ctx->ctx_lock);
 607
 608	while (!list_empty(&ctx->active_reqs)) {
 609		req = list_first_entry(&ctx->active_reqs,
 610				       struct aio_kiocb, ki_list);
 611
 612		list_del_init(&req->ki_list);
 613		kiocb_cancel(req);
 614	}
 615
 616	spin_unlock_irq(&ctx->ctx_lock);
 617
 618	percpu_ref_kill(&ctx->reqs);
 619	percpu_ref_put(&ctx->reqs);
 620}
 621
 622static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
 623{
 624	unsigned i, new_nr;
 625	struct kioctx_table *table, *old;
 626	struct aio_ring *ring;
 627
 628	spin_lock(&mm->ioctx_lock);
 629	table = rcu_dereference_raw(mm->ioctx_table);
 
 630
 631	while (1) {
 632		if (table)
 633			for (i = 0; i < table->nr; i++)
 634				if (!table->table[i]) {
 635					ctx->id = i;
 636					table->table[i] = ctx;
 
 637					spin_unlock(&mm->ioctx_lock);
 638
 639					/* While kioctx setup is in progress,
 640					 * we are protected from page migration
 641					 * changes ring_pages by ->ring_lock.
 642					 */
 643					ring = kmap_atomic(ctx->ring_pages[0]);
 644					ring->id = ctx->id;
 645					kunmap_atomic(ring);
 646					return 0;
 647				}
 648
 649		new_nr = (table ? table->nr : 1) * 4;
 
 
 650		spin_unlock(&mm->ioctx_lock);
 651
 652		table = kzalloc(sizeof(*table) + sizeof(struct kioctx *) *
 653				new_nr, GFP_KERNEL);
 654		if (!table)
 655			return -ENOMEM;
 656
 657		table->nr = new_nr;
 658
 659		spin_lock(&mm->ioctx_lock);
 660		old = rcu_dereference_raw(mm->ioctx_table);
 
 661
 662		if (!old) {
 663			rcu_assign_pointer(mm->ioctx_table, table);
 664		} else if (table->nr > old->nr) {
 665			memcpy(table->table, old->table,
 666			       old->nr * sizeof(struct kioctx *));
 667
 668			rcu_assign_pointer(mm->ioctx_table, table);
 669			kfree_rcu(old, rcu);
 670		} else {
 671			kfree(table);
 672			table = old;
 673		}
 674	}
 675}
 676
 677static void aio_nr_sub(unsigned nr)
 678{
 679	spin_lock(&aio_nr_lock);
 680	if (WARN_ON(aio_nr - nr > aio_nr))
 681		aio_nr = 0;
 682	else
 683		aio_nr -= nr;
 684	spin_unlock(&aio_nr_lock);
 685}
 686
 687/* ioctx_alloc
 688 *	Allocates and initializes an ioctx.  Returns an ERR_PTR if it failed.
 689 */
 690static struct kioctx *ioctx_alloc(unsigned nr_events)
 691{
 692	struct mm_struct *mm = current->mm;
 693	struct kioctx *ctx;
 694	int err = -ENOMEM;
 695
 696	/*
 697	 * We keep track of the number of available ringbuffer slots, to prevent
 698	 * overflow (reqs_available), and we also use percpu counters for this.
 699	 *
 700	 * So since up to half the slots might be on other cpu's percpu counters
 701	 * and unavailable, double nr_events so userspace sees what they
 702	 * expected: additionally, we move req_batch slots to/from percpu
 703	 * counters at a time, so make sure that isn't 0:
 704	 */
 705	nr_events = max(nr_events, num_possible_cpus() * 4);
 706	nr_events *= 2;
 707
 708	/* Prevent overflows */
 709	if (nr_events > (0x10000000U / sizeof(struct io_event))) {
 
 710		pr_debug("ENOMEM: nr_events too high\n");
 711		return ERR_PTR(-EINVAL);
 712	}
 713
 714	if (!nr_events || (unsigned long)nr_events > (aio_max_nr * 2UL))
 715		return ERR_PTR(-EAGAIN);
 716
 717	ctx = kmem_cache_zalloc(kioctx_cachep, GFP_KERNEL);
 718	if (!ctx)
 719		return ERR_PTR(-ENOMEM);
 720
 721	ctx->max_reqs = nr_events;
 722
 723	spin_lock_init(&ctx->ctx_lock);
 724	spin_lock_init(&ctx->completion_lock);
 725	mutex_init(&ctx->ring_lock);
 726	/* Protect against page migration throughout kiotx setup by keeping
 727	 * the ring_lock mutex held until setup is complete. */
 728	mutex_lock(&ctx->ring_lock);
 729	init_waitqueue_head(&ctx->wait);
 730
 731	INIT_LIST_HEAD(&ctx->active_reqs);
 732
 733	if (percpu_ref_init(&ctx->users, free_ioctx_users, 0, GFP_KERNEL))
 734		goto err;
 735
 736	if (percpu_ref_init(&ctx->reqs, free_ioctx_reqs, 0, GFP_KERNEL))
 737		goto err;
 738
 739	ctx->cpu = alloc_percpu(struct kioctx_cpu);
 740	if (!ctx->cpu)
 741		goto err;
 742
 743	err = aio_setup_ring(ctx);
 744	if (err < 0)
 745		goto err;
 746
 747	atomic_set(&ctx->reqs_available, ctx->nr_events - 1);
 748	ctx->req_batch = (ctx->nr_events - 1) / (num_possible_cpus() * 4);
 749	if (ctx->req_batch < 1)
 750		ctx->req_batch = 1;
 751
 752	/* limit the number of system wide aios */
 753	spin_lock(&aio_nr_lock);
 754	if (aio_nr + nr_events > (aio_max_nr * 2UL) ||
 755	    aio_nr + nr_events < aio_nr) {
 756		spin_unlock(&aio_nr_lock);
 757		err = -EAGAIN;
 758		goto err_ctx;
 759	}
 760	aio_nr += ctx->max_reqs;
 761	spin_unlock(&aio_nr_lock);
 762
 763	percpu_ref_get(&ctx->users);	/* io_setup() will drop this ref */
 764	percpu_ref_get(&ctx->reqs);	/* free_ioctx_users() will drop this */
 765
 766	err = ioctx_add_table(ctx, mm);
 767	if (err)
 768		goto err_cleanup;
 769
 770	/* Release the ring_lock mutex now that all setup is complete. */
 771	mutex_unlock(&ctx->ring_lock);
 772
 773	pr_debug("allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",
 774		 ctx, ctx->user_id, mm, ctx->nr_events);
 775	return ctx;
 776
 777err_cleanup:
 778	aio_nr_sub(ctx->max_reqs);
 779err_ctx:
 780	atomic_set(&ctx->dead, 1);
 781	if (ctx->mmap_size)
 782		vm_munmap(ctx->mmap_base, ctx->mmap_size);
 783	aio_free_ring(ctx);
 784err:
 785	mutex_unlock(&ctx->ring_lock);
 786	free_percpu(ctx->cpu);
 787	percpu_ref_exit(&ctx->reqs);
 788	percpu_ref_exit(&ctx->users);
 789	kmem_cache_free(kioctx_cachep, ctx);
 790	pr_debug("error allocating ioctx %d\n", err);
 791	return ERR_PTR(err);
 792}
 793
 794/* kill_ioctx
 795 *	Cancels all outstanding aio requests on an aio context.  Used
 796 *	when the processes owning a context have all exited to encourage
 797 *	the rapid destruction of the kioctx.
 798 */
 799static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx,
 800		      struct ctx_rq_wait *wait)
 801{
 802	struct kioctx_table *table;
 
 803
 804	spin_lock(&mm->ioctx_lock);
 805	if (atomic_xchg(&ctx->dead, 1)) {
 
 
 
 
 
 806		spin_unlock(&mm->ioctx_lock);
 807		return -EINVAL;
 808	}
 809
 810	table = rcu_dereference_raw(mm->ioctx_table);
 811	WARN_ON(ctx != table->table[ctx->id]);
 812	table->table[ctx->id] = NULL;
 813	spin_unlock(&mm->ioctx_lock);
 814
 815	/* percpu_ref_kill() will do the necessary call_rcu() */
 816	wake_up_all(&ctx->wait);
 
 
 
 
 
 
 817
 818	/*
 819	 * It'd be more correct to do this in free_ioctx(), after all
 820	 * the outstanding kiocbs have finished - but by then io_destroy
 821	 * has already returned, so io_setup() could potentially return
 822	 * -EAGAIN with no ioctxs actually in use (as far as userspace
 823	 *  could tell).
 824	 */
 825	aio_nr_sub(ctx->max_reqs);
 826
 827	if (ctx->mmap_size)
 828		vm_munmap(ctx->mmap_base, ctx->mmap_size);
 
 
 
 
 
 829
 830	ctx->rq_wait = wait;
 831	percpu_ref_kill(&ctx->users);
 832	return 0;
 
 
 
 
 
 
 
 
 
 
 833}
 
 834
 835/*
 836 * exit_aio: called when the last user of mm goes away.  At this point, there is
 837 * no way for any new requests to be submited or any of the io_* syscalls to be
 838 * called on the context.
 839 *
 840 * There may be outstanding kiocbs, but free_ioctx() will explicitly wait on
 841 * them.
 842 */
 843void exit_aio(struct mm_struct *mm)
 844{
 845	struct kioctx_table *table = rcu_dereference_raw(mm->ioctx_table);
 846	struct ctx_rq_wait wait;
 847	int i, skipped;
 848
 849	if (!table)
 850		return;
 
 851
 852	atomic_set(&wait.count, table->nr);
 853	init_completion(&wait.comp);
 
 
 
 
 
 
 854
 855	skipped = 0;
 856	for (i = 0; i < table->nr; ++i) {
 857		struct kioctx *ctx = table->table[i];
 858
 859		if (!ctx) {
 860			skipped++;
 861			continue;
 862		}
 863
 864		/*
 865		 * We don't need to bother with munmap() here - exit_mmap(mm)
 866		 * is coming and it'll unmap everything. And we simply can't,
 867		 * this is not necessarily our ->mm.
 868		 * Since kill_ioctx() uses non-zero ->mmap_size as indicator
 869		 * that it needs to unmap the area, just set it to 0.
 
 870		 */
 871		ctx->mmap_size = 0;
 872		kill_ioctx(mm, ctx, &wait);
 873	}
 874
 875	if (!atomic_sub_and_test(skipped, &wait.count)) {
 876		/* Wait until all IO for the context are done. */
 877		wait_for_completion(&wait.comp);
 878	}
 879
 880	RCU_INIT_POINTER(mm->ioctx_table, NULL);
 881	kfree(table);
 882}
 883
 884static void put_reqs_available(struct kioctx *ctx, unsigned nr)
 885{
 886	struct kioctx_cpu *kcpu;
 887	unsigned long flags;
 888
 889	local_irq_save(flags);
 890	kcpu = this_cpu_ptr(ctx->cpu);
 891	kcpu->reqs_available += nr;
 892
 
 893	while (kcpu->reqs_available >= ctx->req_batch * 2) {
 894		kcpu->reqs_available -= ctx->req_batch;
 895		atomic_add(ctx->req_batch, &ctx->reqs_available);
 896	}
 897
 898	local_irq_restore(flags);
 899}
 900
 901static bool get_reqs_available(struct kioctx *ctx)
 902{
 903	struct kioctx_cpu *kcpu;
 904	bool ret = false;
 905	unsigned long flags;
 906
 907	local_irq_save(flags);
 908	kcpu = this_cpu_ptr(ctx->cpu);
 
 909	if (!kcpu->reqs_available) {
 910		int old, avail = atomic_read(&ctx->reqs_available);
 911
 912		do {
 913			if (avail < ctx->req_batch)
 914				goto out;
 915
 916			old = avail;
 917			avail = atomic_cmpxchg(&ctx->reqs_available,
 918					       avail, avail - ctx->req_batch);
 919		} while (avail != old);
 920
 921		kcpu->reqs_available += ctx->req_batch;
 922	}
 923
 924	ret = true;
 925	kcpu->reqs_available--;
 926out:
 927	local_irq_restore(flags);
 928	return ret;
 929}
 930
 931/* refill_reqs_available
 932 *	Updates the reqs_available reference counts used for tracking the
 933 *	number of free slots in the completion ring.  This can be called
 934 *	from aio_complete() (to optimistically update reqs_available) or
 935 *	from aio_get_req() (the we're out of events case).  It must be
 936 *	called holding ctx->completion_lock.
 937 */
 938static void refill_reqs_available(struct kioctx *ctx, unsigned head,
 939                                  unsigned tail)
 940{
 941	unsigned events_in_ring, completed;
 942
 943	/* Clamp head since userland can write to it. */
 944	head %= ctx->nr_events;
 945	if (head <= tail)
 946		events_in_ring = tail - head;
 947	else
 948		events_in_ring = ctx->nr_events - (head - tail);
 949
 950	completed = ctx->completed_events;
 951	if (events_in_ring < completed)
 952		completed -= events_in_ring;
 953	else
 954		completed = 0;
 955
 956	if (!completed)
 957		return;
 958
 959	ctx->completed_events -= completed;
 960	put_reqs_available(ctx, completed);
 961}
 962
 963/* user_refill_reqs_available
 964 *	Called to refill reqs_available when aio_get_req() encounters an
 965 *	out of space in the completion ring.
 966 */
 967static void user_refill_reqs_available(struct kioctx *ctx)
 968{
 969	spin_lock_irq(&ctx->completion_lock);
 970	if (ctx->completed_events) {
 971		struct aio_ring *ring;
 972		unsigned head;
 973
 974		/* Access of ring->head may race with aio_read_events_ring()
 975		 * here, but that's okay since whether we read the old version
 976		 * or the new version, and either will be valid.  The important
 977		 * part is that head cannot pass tail since we prevent
 978		 * aio_complete() from updating tail by holding
 979		 * ctx->completion_lock.  Even if head is invalid, the check
 980		 * against ctx->completed_events below will make sure we do the
 981		 * safe/right thing.
 982		 */
 983		ring = kmap_atomic(ctx->ring_pages[0]);
 984		head = ring->head;
 985		kunmap_atomic(ring);
 986
 987		refill_reqs_available(ctx, head, ctx->tail);
 988	}
 989
 990	spin_unlock_irq(&ctx->completion_lock);
 991}
 992
 993/* aio_get_req
 994 *	Allocate a slot for an aio request.
 995 * Returns NULL if no requests are free.
 996 */
 997static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx)
 998{
 999	struct aio_kiocb *req;
1000
1001	if (!get_reqs_available(ctx)) {
1002		user_refill_reqs_available(ctx);
1003		if (!get_reqs_available(ctx))
1004			return NULL;
1005	}
1006
1007	req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL|__GFP_ZERO);
1008	if (unlikely(!req))
1009		goto out_put;
1010
1011	percpu_ref_get(&ctx->reqs);
1012
1013	req->ki_ctx = ctx;
1014	return req;
1015out_put:
1016	put_reqs_available(ctx, 1);
1017	return NULL;
1018}
1019
1020static void kiocb_free(struct aio_kiocb *req)
1021{
1022	if (req->common.ki_filp)
1023		fput(req->common.ki_filp);
1024	if (req->ki_eventfd != NULL)
1025		eventfd_ctx_put(req->ki_eventfd);
1026	kmem_cache_free(kiocb_cachep, req);
1027}
1028
1029static struct kioctx *lookup_ioctx(unsigned long ctx_id)
1030{
1031	struct aio_ring __user *ring  = (void __user *)ctx_id;
1032	struct mm_struct *mm = current->mm;
1033	struct kioctx *ctx, *ret = NULL;
1034	struct kioctx_table *table;
1035	unsigned id;
1036
1037	if (get_user(id, &ring->id))
1038		return NULL;
1039
1040	rcu_read_lock();
1041	table = rcu_dereference(mm->ioctx_table);
1042
1043	if (!table || id >= table->nr)
1044		goto out;
1045
1046	ctx = table->table[id];
1047	if (ctx && ctx->user_id == ctx_id) {
1048		percpu_ref_get(&ctx->users);
1049		ret = ctx;
1050	}
1051out:
1052	rcu_read_unlock();
1053	return ret;
1054}
1055
1056/* aio_complete
1057 *	Called when the io request on the given iocb is complete.
1058 */
1059static void aio_complete(struct kiocb *kiocb, long res, long res2)
1060{
1061	struct aio_kiocb *iocb = container_of(kiocb, struct aio_kiocb, common);
1062	struct kioctx	*ctx = iocb->ki_ctx;
1063	struct aio_ring	*ring;
1064	struct io_event	*ev_page, *event;
1065	unsigned tail, pos, head;
1066	unsigned long	flags;
 
1067
1068	/*
1069	 * Special case handling for sync iocbs:
1070	 *  - events go directly into the iocb for fast handling
1071	 *  - the sync task with the iocb in its stack holds the single iocb
1072	 *    ref, no other paths have a way to get another ref
1073	 *  - the sync task helpfully left a reference to itself in the iocb
1074	 */
1075	BUG_ON(is_sync_kiocb(kiocb));
 
 
 
 
 
 
1076
1077	if (iocb->ki_list.next) {
1078		unsigned long flags;
1079
1080		spin_lock_irqsave(&ctx->ctx_lock, flags);
1081		list_del(&iocb->ki_list);
1082		spin_unlock_irqrestore(&ctx->ctx_lock, flags);
1083	}
1084
1085	/*
1086	 * Add a completion event to the ring buffer. Must be done holding
1087	 * ctx->completion_lock to prevent other code from messing with the tail
1088	 * pointer since we might be called from irq context.
1089	 */
1090	spin_lock_irqsave(&ctx->completion_lock, flags);
1091
1092	tail = ctx->tail;
1093	pos = tail + AIO_EVENTS_OFFSET;
1094
1095	if (++tail >= ctx->nr_events)
1096		tail = 0;
1097
1098	ev_page = kmap_atomic(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
1099	event = ev_page + pos % AIO_EVENTS_PER_PAGE;
1100
1101	event->obj = (u64)(unsigned long)iocb->ki_user_iocb;
1102	event->data = iocb->ki_user_data;
1103	event->res = res;
1104	event->res2 = res2;
1105
1106	kunmap_atomic(ev_page);
1107	flush_dcache_page(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
1108
1109	pr_debug("%p[%u]: %p: %p %Lx %lx %lx\n",
1110		 ctx, tail, iocb, iocb->ki_user_iocb, iocb->ki_user_data,
1111		 res, res2);
1112
1113	/* after flagging the request as done, we
1114	 * must never even look at it again
1115	 */
1116	smp_wmb();	/* make event visible before updating tail */
1117
1118	ctx->tail = tail;
1119
1120	ring = kmap_atomic(ctx->ring_pages[0]);
1121	head = ring->head;
1122	ring->tail = tail;
1123	kunmap_atomic(ring);
1124	flush_dcache_page(ctx->ring_pages[0]);
1125
1126	ctx->completed_events++;
1127	if (ctx->completed_events > 1)
1128		refill_reqs_available(ctx, head, tail);
1129	spin_unlock_irqrestore(&ctx->completion_lock, flags);
1130
1131	pr_debug("added to ring %p at [%u]\n", iocb, tail);
1132
1133	/*
1134	 * Check if the user asked us to deliver the result through an
1135	 * eventfd. The eventfd_signal() function is safe to be called
1136	 * from IRQ context.
1137	 */
1138	if (iocb->ki_eventfd != NULL)
1139		eventfd_signal(iocb->ki_eventfd, 1);
1140
1141	/* everything turned out well, dispose of the aiocb. */
1142	kiocb_free(iocb);
1143
1144	/*
1145	 * We have to order our ring_info tail store above and test
1146	 * of the wait list below outside the wait lock.  This is
1147	 * like in wake_up_bit() where clearing a bit has to be
1148	 * ordered with the unlocked test.
1149	 */
1150	smp_mb();
1151
1152	if (waitqueue_active(&ctx->wait))
1153		wake_up(&ctx->wait);
1154
1155	percpu_ref_put(&ctx->reqs);
1156}
 
1157
1158/* aio_read_events_ring
1159 *	Pull an event off of the ioctx's event ring.  Returns the number of
1160 *	events fetched
1161 */
1162static long aio_read_events_ring(struct kioctx *ctx,
1163				 struct io_event __user *event, long nr)
1164{
1165	struct aio_ring *ring;
1166	unsigned head, tail, pos;
1167	long ret = 0;
1168	int copy_ret;
1169
1170	/*
1171	 * The mutex can block and wake us up and that will cause
1172	 * wait_event_interruptible_hrtimeout() to schedule without sleeping
1173	 * and repeat. This should be rare enough that it doesn't cause
1174	 * peformance issues. See the comment in read_events() for more detail.
1175	 */
1176	sched_annotate_sleep();
1177	mutex_lock(&ctx->ring_lock);
1178
1179	/* Access to ->ring_pages here is protected by ctx->ring_lock. */
1180	ring = kmap_atomic(ctx->ring_pages[0]);
1181	head = ring->head;
1182	tail = ring->tail;
1183	kunmap_atomic(ring);
1184
1185	/*
1186	 * Ensure that once we've read the current tail pointer, that
1187	 * we also see the events that were stored up to the tail.
1188	 */
1189	smp_rmb();
1190
1191	pr_debug("h%u t%u m%u\n", head, tail, ctx->nr_events);
1192
1193	if (head == tail)
1194		goto out;
1195
1196	head %= ctx->nr_events;
1197	tail %= ctx->nr_events;
1198
1199	while (ret < nr) {
1200		long avail;
1201		struct io_event *ev;
1202		struct page *page;
1203
1204		avail = (head <= tail ?  tail : ctx->nr_events) - head;
1205		if (head == tail)
1206			break;
1207
1208		avail = min(avail, nr - ret);
1209		avail = min_t(long, avail, AIO_EVENTS_PER_PAGE -
1210			    ((head + AIO_EVENTS_OFFSET) % AIO_EVENTS_PER_PAGE));
1211
1212		pos = head + AIO_EVENTS_OFFSET;
1213		page = ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE];
1214		pos %= AIO_EVENTS_PER_PAGE;
1215
1216		ev = kmap(page);
1217		copy_ret = copy_to_user(event + ret, ev + pos,
1218					sizeof(*ev) * avail);
1219		kunmap(page);
1220
1221		if (unlikely(copy_ret)) {
1222			ret = -EFAULT;
1223			goto out;
1224		}
1225
1226		ret += avail;
1227		head += avail;
1228		head %= ctx->nr_events;
1229	}
1230
1231	ring = kmap_atomic(ctx->ring_pages[0]);
1232	ring->head = head;
1233	kunmap_atomic(ring);
1234	flush_dcache_page(ctx->ring_pages[0]);
1235
1236	pr_debug("%li  h%u t%u\n", ret, head, tail);
 
 
1237out:
1238	mutex_unlock(&ctx->ring_lock);
1239
1240	return ret;
1241}
1242
1243static bool aio_read_events(struct kioctx *ctx, long min_nr, long nr,
1244			    struct io_event __user *event, long *i)
1245{
1246	long ret = aio_read_events_ring(ctx, event + *i, nr - *i);
1247
1248	if (ret > 0)
1249		*i += ret;
1250
1251	if (unlikely(atomic_read(&ctx->dead)))
1252		ret = -EINVAL;
1253
1254	if (!*i)
1255		*i = ret;
1256
1257	return ret < 0 || *i >= min_nr;
1258}
1259
1260static long read_events(struct kioctx *ctx, long min_nr, long nr,
1261			struct io_event __user *event,
1262			struct timespec __user *timeout)
1263{
1264	ktime_t until = { .tv64 = KTIME_MAX };
1265	long ret = 0;
1266
1267	if (timeout) {
1268		struct timespec	ts;
1269
1270		if (unlikely(copy_from_user(&ts, timeout, sizeof(ts))))
1271			return -EFAULT;
1272
1273		until = timespec_to_ktime(ts);
1274	}
1275
1276	/*
1277	 * Note that aio_read_events() is being called as the conditional - i.e.
1278	 * we're calling it after prepare_to_wait() has set task state to
1279	 * TASK_INTERRUPTIBLE.
1280	 *
1281	 * But aio_read_events() can block, and if it blocks it's going to flip
1282	 * the task state back to TASK_RUNNING.
1283	 *
1284	 * This should be ok, provided it doesn't flip the state back to
1285	 * TASK_RUNNING and return 0 too much - that causes us to spin. That
1286	 * will only happen if the mutex_lock() call blocks, and we then find
1287	 * the ringbuffer empty. So in practice we should be ok, but it's
1288	 * something to be aware of when touching this code.
1289	 */
1290	if (until.tv64 == 0)
1291		aio_read_events(ctx, min_nr, nr, event, &ret);
1292	else
1293		wait_event_interruptible_hrtimeout(ctx->wait,
1294				aio_read_events(ctx, min_nr, nr, event, &ret),
1295				until);
1296
1297	if (!ret && signal_pending(current))
1298		ret = -EINTR;
1299
1300	return ret;
1301}
1302
1303/* sys_io_setup:
1304 *	Create an aio_context capable of receiving at least nr_events.
1305 *	ctxp must not point to an aio_context that already exists, and
1306 *	must be initialized to 0 prior to the call.  On successful
1307 *	creation of the aio_context, *ctxp is filled in with the resulting 
1308 *	handle.  May fail with -EINVAL if *ctxp is not initialized,
1309 *	if the specified nr_events exceeds internal limits.  May fail 
1310 *	with -EAGAIN if the specified nr_events exceeds the user's limit 
1311 *	of available events.  May fail with -ENOMEM if insufficient kernel
1312 *	resources are available.  May fail with -EFAULT if an invalid
1313 *	pointer is passed for ctxp.  Will fail with -ENOSYS if not
1314 *	implemented.
1315 */
1316SYSCALL_DEFINE2(io_setup, unsigned, nr_events, aio_context_t __user *, ctxp)
1317{
1318	struct kioctx *ioctx = NULL;
1319	unsigned long ctx;
1320	long ret;
1321
1322	ret = get_user(ctx, ctxp);
1323	if (unlikely(ret))
1324		goto out;
1325
1326	ret = -EINVAL;
1327	if (unlikely(ctx || nr_events == 0)) {
1328		pr_debug("EINVAL: ctx %lu nr_events %u\n",
1329		         ctx, nr_events);
1330		goto out;
1331	}
1332
1333	ioctx = ioctx_alloc(nr_events);
1334	ret = PTR_ERR(ioctx);
1335	if (!IS_ERR(ioctx)) {
1336		ret = put_user(ioctx->user_id, ctxp);
1337		if (ret)
1338			kill_ioctx(current->mm, ioctx, NULL);
1339		percpu_ref_put(&ioctx->users);
1340	}
1341
1342out:
1343	return ret;
1344}
1345
1346/* sys_io_destroy:
1347 *	Destroy the aio_context specified.  May cancel any outstanding 
1348 *	AIOs and block on completion.  Will fail with -ENOSYS if not
1349 *	implemented.  May fail with -EINVAL if the context pointed to
1350 *	is invalid.
1351 */
1352SYSCALL_DEFINE1(io_destroy, aio_context_t, ctx)
1353{
1354	struct kioctx *ioctx = lookup_ioctx(ctx);
1355	if (likely(NULL != ioctx)) {
1356		struct ctx_rq_wait wait;
1357		int ret;
1358
1359		init_completion(&wait.comp);
1360		atomic_set(&wait.count, 1);
1361
1362		/* Pass requests_done to kill_ioctx() where it can be set
1363		 * in a thread-safe way. If we try to set it here then we have
1364		 * a race condition if two io_destroy() called simultaneously.
1365		 */
1366		ret = kill_ioctx(current->mm, ioctx, &wait);
1367		percpu_ref_put(&ioctx->users);
1368
1369		/* Wait until all IO for the context are done. Otherwise kernel
1370		 * keep using user-space buffers even if user thinks the context
1371		 * is destroyed.
1372		 */
1373		if (!ret)
1374			wait_for_completion(&wait.comp);
1375
1376		return ret;
1377	}
1378	pr_debug("EINVAL: invalid context id\n");
1379	return -EINVAL;
1380}
1381
1382typedef ssize_t (rw_iter_op)(struct kiocb *, struct iov_iter *);
 
1383
1384static int aio_setup_vectored_rw(int rw, char __user *buf, size_t len,
1385				 struct iovec **iovec,
1386				 bool compat,
1387				 struct iov_iter *iter)
 
1388{
 
 
 
 
1389#ifdef CONFIG_COMPAT
1390	if (compat)
1391		return compat_import_iovec(rw,
1392				(struct compat_iovec __user *)buf,
1393				len, UIO_FASTIOV, iovec, iter);
 
1394#endif
1395	return import_iovec(rw, (struct iovec __user *)buf,
1396				len, UIO_FASTIOV, iovec, iter);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1397}
1398
1399/*
1400 * aio_run_iocb:
1401 *	Performs the initial checks and io submission.
 
1402 */
1403static ssize_t aio_run_iocb(struct kiocb *req, unsigned opcode,
1404			    char __user *buf, size_t len, bool compat)
1405{
1406	struct file *file = req->ki_filp;
1407	ssize_t ret;
 
1408	int rw;
1409	fmode_t mode;
1410	rw_iter_op *iter_op;
1411	struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
1412	struct iov_iter iter;
1413
1414	switch (opcode) {
1415	case IOCB_CMD_PREAD:
1416	case IOCB_CMD_PREADV:
1417		mode	= FMODE_READ;
1418		rw	= READ;
1419		iter_op	= file->f_op->read_iter;
1420		goto rw_common;
1421
1422	case IOCB_CMD_PWRITE:
1423	case IOCB_CMD_PWRITEV:
1424		mode	= FMODE_WRITE;
1425		rw	= WRITE;
1426		iter_op	= file->f_op->write_iter;
1427		goto rw_common;
1428rw_common:
1429		if (unlikely(!(file->f_mode & mode)))
1430			return -EBADF;
1431
1432		if (!iter_op)
1433			return -EINVAL;
1434
1435		if (opcode == IOCB_CMD_PREADV || opcode == IOCB_CMD_PWRITEV)
1436			ret = aio_setup_vectored_rw(rw, buf, len,
1437						&iovec, compat, &iter);
1438		else {
1439			ret = import_single_range(rw, buf, len, iovec, &iter);
1440			iovec = NULL;
1441		}
1442		if (!ret)
1443			ret = rw_verify_area(rw, file, &req->ki_pos,
1444					     iov_iter_count(&iter));
1445		if (ret < 0) {
1446			kfree(iovec);
 
1447			return ret;
1448		}
1449
1450		len = ret;
 
 
 
 
 
 
 
1451
1452		if (rw == WRITE)
1453			file_start_write(file);
1454
1455		ret = iter_op(req, &iter);
1456
1457		if (rw == WRITE)
1458			file_end_write(file);
1459		kfree(iovec);
1460		break;
1461
1462	case IOCB_CMD_FDSYNC:
1463		if (!file->f_op->aio_fsync)
1464			return -EINVAL;
1465
1466		ret = file->f_op->aio_fsync(req, 1);
1467		break;
1468
1469	case IOCB_CMD_FSYNC:
1470		if (!file->f_op->aio_fsync)
1471			return -EINVAL;
1472
1473		ret = file->f_op->aio_fsync(req, 0);
1474		break;
1475
1476	default:
1477		pr_debug("EINVAL: no operation provided\n");
1478		return -EINVAL;
1479	}
1480
 
 
 
1481	if (ret != -EIOCBQUEUED) {
1482		/*
1483		 * There's no easy way to restart the syscall since other AIO's
1484		 * may be already running. Just fail this IO with EINTR.
1485		 */
1486		if (unlikely(ret == -ERESTARTSYS || ret == -ERESTARTNOINTR ||
1487			     ret == -ERESTARTNOHAND ||
1488			     ret == -ERESTART_RESTARTBLOCK))
1489			ret = -EINTR;
1490		aio_complete(req, ret, 0);
1491	}
1492
1493	return 0;
1494}
1495
1496static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
1497			 struct iocb *iocb, bool compat)
1498{
1499	struct aio_kiocb *req;
1500	ssize_t ret;
1501
1502	/* enforce forwards compatibility on users */
1503	if (unlikely(iocb->aio_reserved1 || iocb->aio_reserved2)) {
1504		pr_debug("EINVAL: reserve field set\n");
1505		return -EINVAL;
1506	}
1507
1508	/* prevent overflows */
1509	if (unlikely(
1510	    (iocb->aio_buf != (unsigned long)iocb->aio_buf) ||
1511	    (iocb->aio_nbytes != (size_t)iocb->aio_nbytes) ||
1512	    ((ssize_t)iocb->aio_nbytes < 0)
1513	   )) {
1514		pr_debug("EINVAL: overflow check\n");
1515		return -EINVAL;
1516	}
1517
1518	req = aio_get_req(ctx);
1519	if (unlikely(!req))
1520		return -EAGAIN;
1521
1522	req->common.ki_filp = fget(iocb->aio_fildes);
1523	if (unlikely(!req->common.ki_filp)) {
1524		ret = -EBADF;
1525		goto out_put_req;
1526	}
1527	req->common.ki_pos = iocb->aio_offset;
1528	req->common.ki_complete = aio_complete;
1529	req->common.ki_flags = iocb_flags(req->common.ki_filp);
1530
1531	if (iocb->aio_flags & IOCB_FLAG_RESFD) {
1532		/*
1533		 * If the IOCB_FLAG_RESFD flag of aio_flags is set, get an
1534		 * instance of the file* now. The file descriptor must be
1535		 * an eventfd() fd, and will be signaled for each completed
1536		 * event using the eventfd_signal() function.
1537		 */
1538		req->ki_eventfd = eventfd_ctx_fdget((int) iocb->aio_resfd);
1539		if (IS_ERR(req->ki_eventfd)) {
1540			ret = PTR_ERR(req->ki_eventfd);
1541			req->ki_eventfd = NULL;
1542			goto out_put_req;
1543		}
1544
1545		req->common.ki_flags |= IOCB_EVENTFD;
1546	}
1547
1548	ret = put_user(KIOCB_KEY, &user_iocb->aio_key);
1549	if (unlikely(ret)) {
1550		pr_debug("EFAULT: aio_key\n");
1551		goto out_put_req;
1552	}
1553
1554	req->ki_user_iocb = user_iocb;
1555	req->ki_user_data = iocb->aio_data;
 
 
1556
1557	ret = aio_run_iocb(&req->common, iocb->aio_lio_opcode,
1558			   (char __user *)(unsigned long)iocb->aio_buf,
1559			   iocb->aio_nbytes,
1560			   compat);
1561	if (ret)
1562		goto out_put_req;
1563
1564	return 0;
1565out_put_req:
1566	put_reqs_available(ctx, 1);
1567	percpu_ref_put(&ctx->reqs);
1568	kiocb_free(req);
1569	return ret;
1570}
1571
1572long do_io_submit(aio_context_t ctx_id, long nr,
1573		  struct iocb __user *__user *iocbpp, bool compat)
1574{
1575	struct kioctx *ctx;
1576	long ret = 0;
1577	int i = 0;
1578	struct blk_plug plug;
1579
1580	if (unlikely(nr < 0))
1581		return -EINVAL;
1582
1583	if (unlikely(nr > LONG_MAX/sizeof(*iocbpp)))
1584		nr = LONG_MAX/sizeof(*iocbpp);
1585
1586	if (unlikely(!access_ok(VERIFY_READ, iocbpp, (nr*sizeof(*iocbpp)))))
1587		return -EFAULT;
1588
1589	ctx = lookup_ioctx(ctx_id);
1590	if (unlikely(!ctx)) {
1591		pr_debug("EINVAL: invalid context id\n");
1592		return -EINVAL;
1593	}
1594
1595	blk_start_plug(&plug);
1596
1597	/*
1598	 * AKPM: should this return a partial result if some of the IOs were
1599	 * successfully submitted?
1600	 */
1601	for (i=0; i<nr; i++) {
1602		struct iocb __user *user_iocb;
1603		struct iocb tmp;
1604
1605		if (unlikely(__get_user(user_iocb, iocbpp + i))) {
1606			ret = -EFAULT;
1607			break;
1608		}
1609
1610		if (unlikely(copy_from_user(&tmp, user_iocb, sizeof(tmp)))) {
1611			ret = -EFAULT;
1612			break;
1613		}
1614
1615		ret = io_submit_one(ctx, user_iocb, &tmp, compat);
1616		if (ret)
1617			break;
1618	}
1619	blk_finish_plug(&plug);
1620
1621	percpu_ref_put(&ctx->users);
1622	return i ? i : ret;
1623}
1624
1625/* sys_io_submit:
1626 *	Queue the nr iocbs pointed to by iocbpp for processing.  Returns
1627 *	the number of iocbs queued.  May return -EINVAL if the aio_context
1628 *	specified by ctx_id is invalid, if nr is < 0, if the iocb at
1629 *	*iocbpp[0] is not properly initialized, if the operation specified
1630 *	is invalid for the file descriptor in the iocb.  May fail with
1631 *	-EFAULT if any of the data structures point to invalid data.  May
1632 *	fail with -EBADF if the file descriptor specified in the first
1633 *	iocb is invalid.  May fail with -EAGAIN if insufficient resources
1634 *	are available to queue any iocbs.  Will return 0 if nr is 0.  Will
1635 *	fail with -ENOSYS if not implemented.
1636 */
1637SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
1638		struct iocb __user * __user *, iocbpp)
1639{
1640	return do_io_submit(ctx_id, nr, iocbpp, 0);
1641}
1642
1643/* lookup_kiocb
1644 *	Finds a given iocb for cancellation.
1645 */
1646static struct aio_kiocb *
1647lookup_kiocb(struct kioctx *ctx, struct iocb __user *iocb, u32 key)
1648{
1649	struct aio_kiocb *kiocb;
1650
1651	assert_spin_locked(&ctx->ctx_lock);
1652
1653	if (key != KIOCB_KEY)
1654		return NULL;
1655
1656	/* TODO: use a hash or array, this sucks. */
1657	list_for_each_entry(kiocb, &ctx->active_reqs, ki_list) {
1658		if (kiocb->ki_user_iocb == iocb)
 
1659			return kiocb;
1660	}
1661	return NULL;
1662}
1663
1664/* sys_io_cancel:
1665 *	Attempts to cancel an iocb previously passed to io_submit.  If
1666 *	the operation is successfully cancelled, the resulting event is
1667 *	copied into the memory pointed to by result without being placed
1668 *	into the completion queue and 0 is returned.  May fail with
1669 *	-EFAULT if any of the data structures pointed to are invalid.
1670 *	May fail with -EINVAL if aio_context specified by ctx_id is
1671 *	invalid.  May fail with -EAGAIN if the iocb specified was not
1672 *	cancelled.  Will fail with -ENOSYS if not implemented.
1673 */
1674SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
1675		struct io_event __user *, result)
1676{
1677	struct kioctx *ctx;
1678	struct aio_kiocb *kiocb;
1679	u32 key;
1680	int ret;
1681
1682	ret = get_user(key, &iocb->aio_key);
1683	if (unlikely(ret))
1684		return -EFAULT;
1685
1686	ctx = lookup_ioctx(ctx_id);
1687	if (unlikely(!ctx))
1688		return -EINVAL;
1689
1690	spin_lock_irq(&ctx->ctx_lock);
1691
1692	kiocb = lookup_kiocb(ctx, iocb, key);
1693	if (kiocb)
1694		ret = kiocb_cancel(kiocb);
1695	else
1696		ret = -EINVAL;
1697
1698	spin_unlock_irq(&ctx->ctx_lock);
1699
1700	if (!ret) {
1701		/*
1702		 * The result argument is no longer used - the io_event is
1703		 * always delivered via the ring buffer. -EINPROGRESS indicates
1704		 * cancellation is progress:
1705		 */
1706		ret = -EINPROGRESS;
1707	}
1708
1709	percpu_ref_put(&ctx->users);
1710
1711	return ret;
1712}
1713
1714/* io_getevents:
1715 *	Attempts to read at least min_nr events and up to nr events from
1716 *	the completion queue for the aio_context specified by ctx_id. If
1717 *	it succeeds, the number of read events is returned. May fail with
1718 *	-EINVAL if ctx_id is invalid, if min_nr is out of range, if nr is
1719 *	out of range, if timeout is out of range.  May fail with -EFAULT
1720 *	if any of the memory specified is invalid.  May return 0 or
1721 *	< min_nr if the timeout specified by timeout has elapsed
1722 *	before sufficient events are available, where timeout == NULL
1723 *	specifies an infinite timeout. Note that the timeout pointed to by
1724 *	timeout is relative.  Will fail with -ENOSYS if not implemented.
1725 */
1726SYSCALL_DEFINE5(io_getevents, aio_context_t, ctx_id,
1727		long, min_nr,
1728		long, nr,
1729		struct io_event __user *, events,
1730		struct timespec __user *, timeout)
1731{
1732	struct kioctx *ioctx = lookup_ioctx(ctx_id);
1733	long ret = -EINVAL;
1734
1735	if (likely(ioctx)) {
1736		if (likely(min_nr <= nr && min_nr >= 0))
1737			ret = read_events(ioctx, min_nr, nr, events, timeout);
1738		percpu_ref_put(&ioctx->users);
1739	}
1740	return ret;
1741}