cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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aio.c (62458B)


      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 *	Copyright 2018 Christoph Hellwig.
      9 *
     10 *	See ../COPYING for licensing terms.
     11 */
     12#define pr_fmt(fmt) "%s: " fmt, __func__
     13
     14#include <linux/kernel.h>
     15#include <linux/init.h>
     16#include <linux/errno.h>
     17#include <linux/time.h>
     18#include <linux/aio_abi.h>
     19#include <linux/export.h>
     20#include <linux/syscalls.h>
     21#include <linux/backing-dev.h>
     22#include <linux/refcount.h>
     23#include <linux/uio.h>
     24
     25#include <linux/sched/signal.h>
     26#include <linux/fs.h>
     27#include <linux/file.h>
     28#include <linux/mm.h>
     29#include <linux/mman.h>
     30#include <linux/percpu.h>
     31#include <linux/slab.h>
     32#include <linux/timer.h>
     33#include <linux/aio.h>
     34#include <linux/highmem.h>
     35#include <linux/workqueue.h>
     36#include <linux/security.h>
     37#include <linux/eventfd.h>
     38#include <linux/blkdev.h>
     39#include <linux/compat.h>
     40#include <linux/migrate.h>
     41#include <linux/ramfs.h>
     42#include <linux/percpu-refcount.h>
     43#include <linux/mount.h>
     44#include <linux/pseudo_fs.h>
     45
     46#include <linux/uaccess.h>
     47#include <linux/nospec.h>
     48
     49#include "internal.h"
     50
     51#define KIOCB_KEY		0
     52
     53#define AIO_RING_MAGIC			0xa10a10a1
     54#define AIO_RING_COMPAT_FEATURES	1
     55#define AIO_RING_INCOMPAT_FEATURES	0
     56struct aio_ring {
     57	unsigned	id;	/* kernel internal index number */
     58	unsigned	nr;	/* number of io_events */
     59	unsigned	head;	/* Written to by userland or under ring_lock
     60				 * mutex by aio_read_events_ring(). */
     61	unsigned	tail;
     62
     63	unsigned	magic;
     64	unsigned	compat_features;
     65	unsigned	incompat_features;
     66	unsigned	header_length;	/* size of aio_ring */
     67
     68
     69	struct io_event		io_events[];
     70}; /* 128 bytes + ring size */
     71
     72/*
     73 * Plugging is meant to work with larger batches of IOs. If we don't
     74 * have more than the below, then don't bother setting up a plug.
     75 */
     76#define AIO_PLUG_THRESHOLD	2
     77
     78#define AIO_RING_PAGES	8
     79
     80struct kioctx_table {
     81	struct rcu_head		rcu;
     82	unsigned		nr;
     83	struct kioctx __rcu	*table[];
     84};
     85
     86struct kioctx_cpu {
     87	unsigned		reqs_available;
     88};
     89
     90struct ctx_rq_wait {
     91	struct completion comp;
     92	atomic_t count;
     93};
     94
     95struct kioctx {
     96	struct percpu_ref	users;
     97	atomic_t		dead;
     98
     99	struct percpu_ref	reqs;
    100
    101	unsigned long		user_id;
    102
    103	struct __percpu kioctx_cpu *cpu;
    104
    105	/*
    106	 * For percpu reqs_available, number of slots we move to/from global
    107	 * counter at a time:
    108	 */
    109	unsigned		req_batch;
    110	/*
    111	 * This is what userspace passed to io_setup(), it's not used for
    112	 * anything but counting against the global max_reqs quota.
    113	 *
    114	 * The real limit is nr_events - 1, which will be larger (see
    115	 * aio_setup_ring())
    116	 */
    117	unsigned		max_reqs;
    118
    119	/* Size of ringbuffer, in units of struct io_event */
    120	unsigned		nr_events;
    121
    122	unsigned long		mmap_base;
    123	unsigned long		mmap_size;
    124
    125	struct page		**ring_pages;
    126	long			nr_pages;
    127
    128	struct rcu_work		free_rwork;	/* see free_ioctx() */
    129
    130	/*
    131	 * signals when all in-flight requests are done
    132	 */
    133	struct ctx_rq_wait	*rq_wait;
    134
    135	struct {
    136		/*
    137		 * This counts the number of available slots in the ringbuffer,
    138		 * so we avoid overflowing it: it's decremented (if positive)
    139		 * when allocating a kiocb and incremented when the resulting
    140		 * io_event is pulled off the ringbuffer.
    141		 *
    142		 * We batch accesses to it with a percpu version.
    143		 */
    144		atomic_t	reqs_available;
    145	} ____cacheline_aligned_in_smp;
    146
    147	struct {
    148		spinlock_t	ctx_lock;
    149		struct list_head active_reqs;	/* used for cancellation */
    150	} ____cacheline_aligned_in_smp;
    151
    152	struct {
    153		struct mutex	ring_lock;
    154		wait_queue_head_t wait;
    155	} ____cacheline_aligned_in_smp;
    156
    157	struct {
    158		unsigned	tail;
    159		unsigned	completed_events;
    160		spinlock_t	completion_lock;
    161	} ____cacheline_aligned_in_smp;
    162
    163	struct page		*internal_pages[AIO_RING_PAGES];
    164	struct file		*aio_ring_file;
    165
    166	unsigned		id;
    167};
    168
    169/*
    170 * First field must be the file pointer in all the
    171 * iocb unions! See also 'struct kiocb' in <linux/fs.h>
    172 */
    173struct fsync_iocb {
    174	struct file		*file;
    175	struct work_struct	work;
    176	bool			datasync;
    177	struct cred		*creds;
    178};
    179
    180struct poll_iocb {
    181	struct file		*file;
    182	struct wait_queue_head	*head;
    183	__poll_t		events;
    184	bool			cancelled;
    185	bool			work_scheduled;
    186	bool			work_need_resched;
    187	struct wait_queue_entry	wait;
    188	struct work_struct	work;
    189};
    190
    191/*
    192 * NOTE! Each of the iocb union members has the file pointer
    193 * as the first entry in their struct definition. So you can
    194 * access the file pointer through any of the sub-structs,
    195 * or directly as just 'ki_filp' in this struct.
    196 */
    197struct aio_kiocb {
    198	union {
    199		struct file		*ki_filp;
    200		struct kiocb		rw;
    201		struct fsync_iocb	fsync;
    202		struct poll_iocb	poll;
    203	};
    204
    205	struct kioctx		*ki_ctx;
    206	kiocb_cancel_fn		*ki_cancel;
    207
    208	struct io_event		ki_res;
    209
    210	struct list_head	ki_list;	/* the aio core uses this
    211						 * for cancellation */
    212	refcount_t		ki_refcnt;
    213
    214	/*
    215	 * If the aio_resfd field of the userspace iocb is not zero,
    216	 * this is the underlying eventfd context to deliver events to.
    217	 */
    218	struct eventfd_ctx	*ki_eventfd;
    219};
    220
    221/*------ sysctl variables----*/
    222static DEFINE_SPINLOCK(aio_nr_lock);
    223static unsigned long aio_nr;		/* current system wide number of aio requests */
    224static unsigned long aio_max_nr = 0x10000; /* system wide maximum number of aio requests */
    225/*----end sysctl variables---*/
    226#ifdef CONFIG_SYSCTL
    227static struct ctl_table aio_sysctls[] = {
    228	{
    229		.procname	= "aio-nr",
    230		.data		= &aio_nr,
    231		.maxlen		= sizeof(aio_nr),
    232		.mode		= 0444,
    233		.proc_handler	= proc_doulongvec_minmax,
    234	},
    235	{
    236		.procname	= "aio-max-nr",
    237		.data		= &aio_max_nr,
    238		.maxlen		= sizeof(aio_max_nr),
    239		.mode		= 0644,
    240		.proc_handler	= proc_doulongvec_minmax,
    241	},
    242	{}
    243};
    244
    245static void __init aio_sysctl_init(void)
    246{
    247	register_sysctl_init("fs", aio_sysctls);
    248}
    249#else
    250#define aio_sysctl_init() do { } while (0)
    251#endif
    252
    253static struct kmem_cache	*kiocb_cachep;
    254static struct kmem_cache	*kioctx_cachep;
    255
    256static struct vfsmount *aio_mnt;
    257
    258static const struct file_operations aio_ring_fops;
    259static const struct address_space_operations aio_ctx_aops;
    260
    261static struct file *aio_private_file(struct kioctx *ctx, loff_t nr_pages)
    262{
    263	struct file *file;
    264	struct inode *inode = alloc_anon_inode(aio_mnt->mnt_sb);
    265	if (IS_ERR(inode))
    266		return ERR_CAST(inode);
    267
    268	inode->i_mapping->a_ops = &aio_ctx_aops;
    269	inode->i_mapping->private_data = ctx;
    270	inode->i_size = PAGE_SIZE * nr_pages;
    271
    272	file = alloc_file_pseudo(inode, aio_mnt, "[aio]",
    273				O_RDWR, &aio_ring_fops);
    274	if (IS_ERR(file))
    275		iput(inode);
    276	return file;
    277}
    278
    279static int aio_init_fs_context(struct fs_context *fc)
    280{
    281	if (!init_pseudo(fc, AIO_RING_MAGIC))
    282		return -ENOMEM;
    283	fc->s_iflags |= SB_I_NOEXEC;
    284	return 0;
    285}
    286
    287/* aio_setup
    288 *	Creates the slab caches used by the aio routines, panic on
    289 *	failure as this is done early during the boot sequence.
    290 */
    291static int __init aio_setup(void)
    292{
    293	static struct file_system_type aio_fs = {
    294		.name		= "aio",
    295		.init_fs_context = aio_init_fs_context,
    296		.kill_sb	= kill_anon_super,
    297	};
    298	aio_mnt = kern_mount(&aio_fs);
    299	if (IS_ERR(aio_mnt))
    300		panic("Failed to create aio fs mount.");
    301
    302	kiocb_cachep = KMEM_CACHE(aio_kiocb, SLAB_HWCACHE_ALIGN|SLAB_PANIC);
    303	kioctx_cachep = KMEM_CACHE(kioctx,SLAB_HWCACHE_ALIGN|SLAB_PANIC);
    304	aio_sysctl_init();
    305	return 0;
    306}
    307__initcall(aio_setup);
    308
    309static void put_aio_ring_file(struct kioctx *ctx)
    310{
    311	struct file *aio_ring_file = ctx->aio_ring_file;
    312	struct address_space *i_mapping;
    313
    314	if (aio_ring_file) {
    315		truncate_setsize(file_inode(aio_ring_file), 0);
    316
    317		/* Prevent further access to the kioctx from migratepages */
    318		i_mapping = aio_ring_file->f_mapping;
    319		spin_lock(&i_mapping->private_lock);
    320		i_mapping->private_data = NULL;
    321		ctx->aio_ring_file = NULL;
    322		spin_unlock(&i_mapping->private_lock);
    323
    324		fput(aio_ring_file);
    325	}
    326}
    327
    328static void aio_free_ring(struct kioctx *ctx)
    329{
    330	int i;
    331
    332	/* Disconnect the kiotx from the ring file.  This prevents future
    333	 * accesses to the kioctx from page migration.
    334	 */
    335	put_aio_ring_file(ctx);
    336
    337	for (i = 0; i < ctx->nr_pages; i++) {
    338		struct page *page;
    339		pr_debug("pid(%d) [%d] page->count=%d\n", current->pid, i,
    340				page_count(ctx->ring_pages[i]));
    341		page = ctx->ring_pages[i];
    342		if (!page)
    343			continue;
    344		ctx->ring_pages[i] = NULL;
    345		put_page(page);
    346	}
    347
    348	if (ctx->ring_pages && ctx->ring_pages != ctx->internal_pages) {
    349		kfree(ctx->ring_pages);
    350		ctx->ring_pages = NULL;
    351	}
    352}
    353
    354static int aio_ring_mremap(struct vm_area_struct *vma)
    355{
    356	struct file *file = vma->vm_file;
    357	struct mm_struct *mm = vma->vm_mm;
    358	struct kioctx_table *table;
    359	int i, res = -EINVAL;
    360
    361	spin_lock(&mm->ioctx_lock);
    362	rcu_read_lock();
    363	table = rcu_dereference(mm->ioctx_table);
    364	for (i = 0; i < table->nr; i++) {
    365		struct kioctx *ctx;
    366
    367		ctx = rcu_dereference(table->table[i]);
    368		if (ctx && ctx->aio_ring_file == file) {
    369			if (!atomic_read(&ctx->dead)) {
    370				ctx->user_id = ctx->mmap_base = vma->vm_start;
    371				res = 0;
    372			}
    373			break;
    374		}
    375	}
    376
    377	rcu_read_unlock();
    378	spin_unlock(&mm->ioctx_lock);
    379	return res;
    380}
    381
    382static const struct vm_operations_struct aio_ring_vm_ops = {
    383	.mremap		= aio_ring_mremap,
    384#if IS_ENABLED(CONFIG_MMU)
    385	.fault		= filemap_fault,
    386	.map_pages	= filemap_map_pages,
    387	.page_mkwrite	= filemap_page_mkwrite,
    388#endif
    389};
    390
    391static int aio_ring_mmap(struct file *file, struct vm_area_struct *vma)
    392{
    393	vma->vm_flags |= VM_DONTEXPAND;
    394	vma->vm_ops = &aio_ring_vm_ops;
    395	return 0;
    396}
    397
    398static const struct file_operations aio_ring_fops = {
    399	.mmap = aio_ring_mmap,
    400};
    401
    402#if IS_ENABLED(CONFIG_MIGRATION)
    403static int aio_migratepage(struct address_space *mapping, struct page *new,
    404			struct page *old, enum migrate_mode mode)
    405{
    406	struct kioctx *ctx;
    407	unsigned long flags;
    408	pgoff_t idx;
    409	int rc;
    410
    411	/*
    412	 * We cannot support the _NO_COPY case here, because copy needs to
    413	 * happen under the ctx->completion_lock. That does not work with the
    414	 * migration workflow of MIGRATE_SYNC_NO_COPY.
    415	 */
    416	if (mode == MIGRATE_SYNC_NO_COPY)
    417		return -EINVAL;
    418
    419	rc = 0;
    420
    421	/* mapping->private_lock here protects against the kioctx teardown.  */
    422	spin_lock(&mapping->private_lock);
    423	ctx = mapping->private_data;
    424	if (!ctx) {
    425		rc = -EINVAL;
    426		goto out;
    427	}
    428
    429	/* The ring_lock mutex.  The prevents aio_read_events() from writing
    430	 * to the ring's head, and prevents page migration from mucking in
    431	 * a partially initialized kiotx.
    432	 */
    433	if (!mutex_trylock(&ctx->ring_lock)) {
    434		rc = -EAGAIN;
    435		goto out;
    436	}
    437
    438	idx = old->index;
    439	if (idx < (pgoff_t)ctx->nr_pages) {
    440		/* Make sure the old page hasn't already been changed */
    441		if (ctx->ring_pages[idx] != old)
    442			rc = -EAGAIN;
    443	} else
    444		rc = -EINVAL;
    445
    446	if (rc != 0)
    447		goto out_unlock;
    448
    449	/* Writeback must be complete */
    450	BUG_ON(PageWriteback(old));
    451	get_page(new);
    452
    453	rc = migrate_page_move_mapping(mapping, new, old, 1);
    454	if (rc != MIGRATEPAGE_SUCCESS) {
    455		put_page(new);
    456		goto out_unlock;
    457	}
    458
    459	/* Take completion_lock to prevent other writes to the ring buffer
    460	 * while the old page is copied to the new.  This prevents new
    461	 * events from being lost.
    462	 */
    463	spin_lock_irqsave(&ctx->completion_lock, flags);
    464	migrate_page_copy(new, old);
    465	BUG_ON(ctx->ring_pages[idx] != old);
    466	ctx->ring_pages[idx] = new;
    467	spin_unlock_irqrestore(&ctx->completion_lock, flags);
    468
    469	/* The old page is no longer accessible. */
    470	put_page(old);
    471
    472out_unlock:
    473	mutex_unlock(&ctx->ring_lock);
    474out:
    475	spin_unlock(&mapping->private_lock);
    476	return rc;
    477}
    478#endif
    479
    480static const struct address_space_operations aio_ctx_aops = {
    481	.dirty_folio	= noop_dirty_folio,
    482#if IS_ENABLED(CONFIG_MIGRATION)
    483	.migratepage	= aio_migratepage,
    484#endif
    485};
    486
    487static int aio_setup_ring(struct kioctx *ctx, unsigned int nr_events)
    488{
    489	struct aio_ring *ring;
    490	struct mm_struct *mm = current->mm;
    491	unsigned long size, unused;
    492	int nr_pages;
    493	int i;
    494	struct file *file;
    495
    496	/* Compensate for the ring buffer's head/tail overlap entry */
    497	nr_events += 2;	/* 1 is required, 2 for good luck */
    498
    499	size = sizeof(struct aio_ring);
    500	size += sizeof(struct io_event) * nr_events;
    501
    502	nr_pages = PFN_UP(size);
    503	if (nr_pages < 0)
    504		return -EINVAL;
    505
    506	file = aio_private_file(ctx, nr_pages);
    507	if (IS_ERR(file)) {
    508		ctx->aio_ring_file = NULL;
    509		return -ENOMEM;
    510	}
    511
    512	ctx->aio_ring_file = file;
    513	nr_events = (PAGE_SIZE * nr_pages - sizeof(struct aio_ring))
    514			/ sizeof(struct io_event);
    515
    516	ctx->ring_pages = ctx->internal_pages;
    517	if (nr_pages > AIO_RING_PAGES) {
    518		ctx->ring_pages = kcalloc(nr_pages, sizeof(struct page *),
    519					  GFP_KERNEL);
    520		if (!ctx->ring_pages) {
    521			put_aio_ring_file(ctx);
    522			return -ENOMEM;
    523		}
    524	}
    525
    526	for (i = 0; i < nr_pages; i++) {
    527		struct page *page;
    528		page = find_or_create_page(file->f_mapping,
    529					   i, GFP_HIGHUSER | __GFP_ZERO);
    530		if (!page)
    531			break;
    532		pr_debug("pid(%d) page[%d]->count=%d\n",
    533			 current->pid, i, page_count(page));
    534		SetPageUptodate(page);
    535		unlock_page(page);
    536
    537		ctx->ring_pages[i] = page;
    538	}
    539	ctx->nr_pages = i;
    540
    541	if (unlikely(i != nr_pages)) {
    542		aio_free_ring(ctx);
    543		return -ENOMEM;
    544	}
    545
    546	ctx->mmap_size = nr_pages * PAGE_SIZE;
    547	pr_debug("attempting mmap of %lu bytes\n", ctx->mmap_size);
    548
    549	if (mmap_write_lock_killable(mm)) {
    550		ctx->mmap_size = 0;
    551		aio_free_ring(ctx);
    552		return -EINTR;
    553	}
    554
    555	ctx->mmap_base = do_mmap(ctx->aio_ring_file, 0, ctx->mmap_size,
    556				 PROT_READ | PROT_WRITE,
    557				 MAP_SHARED, 0, &unused, NULL);
    558	mmap_write_unlock(mm);
    559	if (IS_ERR((void *)ctx->mmap_base)) {
    560		ctx->mmap_size = 0;
    561		aio_free_ring(ctx);
    562		return -ENOMEM;
    563	}
    564
    565	pr_debug("mmap address: 0x%08lx\n", ctx->mmap_base);
    566
    567	ctx->user_id = ctx->mmap_base;
    568	ctx->nr_events = nr_events; /* trusted copy */
    569
    570	ring = kmap_atomic(ctx->ring_pages[0]);
    571	ring->nr = nr_events;	/* user copy */
    572	ring->id = ~0U;
    573	ring->head = ring->tail = 0;
    574	ring->magic = AIO_RING_MAGIC;
    575	ring->compat_features = AIO_RING_COMPAT_FEATURES;
    576	ring->incompat_features = AIO_RING_INCOMPAT_FEATURES;
    577	ring->header_length = sizeof(struct aio_ring);
    578	kunmap_atomic(ring);
    579	flush_dcache_page(ctx->ring_pages[0]);
    580
    581	return 0;
    582}
    583
    584#define AIO_EVENTS_PER_PAGE	(PAGE_SIZE / sizeof(struct io_event))
    585#define AIO_EVENTS_FIRST_PAGE	((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event))
    586#define AIO_EVENTS_OFFSET	(AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE)
    587
    588void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel)
    589{
    590	struct aio_kiocb *req = container_of(iocb, struct aio_kiocb, rw);
    591	struct kioctx *ctx = req->ki_ctx;
    592	unsigned long flags;
    593
    594	if (WARN_ON_ONCE(!list_empty(&req->ki_list)))
    595		return;
    596
    597	spin_lock_irqsave(&ctx->ctx_lock, flags);
    598	list_add_tail(&req->ki_list, &ctx->active_reqs);
    599	req->ki_cancel = cancel;
    600	spin_unlock_irqrestore(&ctx->ctx_lock, flags);
    601}
    602EXPORT_SYMBOL(kiocb_set_cancel_fn);
    603
    604/*
    605 * free_ioctx() should be RCU delayed to synchronize against the RCU
    606 * protected lookup_ioctx() and also needs process context to call
    607 * aio_free_ring().  Use rcu_work.
    608 */
    609static void free_ioctx(struct work_struct *work)
    610{
    611	struct kioctx *ctx = container_of(to_rcu_work(work), struct kioctx,
    612					  free_rwork);
    613	pr_debug("freeing %p\n", ctx);
    614
    615	aio_free_ring(ctx);
    616	free_percpu(ctx->cpu);
    617	percpu_ref_exit(&ctx->reqs);
    618	percpu_ref_exit(&ctx->users);
    619	kmem_cache_free(kioctx_cachep, ctx);
    620}
    621
    622static void free_ioctx_reqs(struct percpu_ref *ref)
    623{
    624	struct kioctx *ctx = container_of(ref, struct kioctx, reqs);
    625
    626	/* At this point we know that there are no any in-flight requests */
    627	if (ctx->rq_wait && atomic_dec_and_test(&ctx->rq_wait->count))
    628		complete(&ctx->rq_wait->comp);
    629
    630	/* Synchronize against RCU protected table->table[] dereferences */
    631	INIT_RCU_WORK(&ctx->free_rwork, free_ioctx);
    632	queue_rcu_work(system_wq, &ctx->free_rwork);
    633}
    634
    635/*
    636 * When this function runs, the kioctx has been removed from the "hash table"
    637 * and ctx->users has dropped to 0, so we know no more kiocbs can be submitted -
    638 * now it's safe to cancel any that need to be.
    639 */
    640static void free_ioctx_users(struct percpu_ref *ref)
    641{
    642	struct kioctx *ctx = container_of(ref, struct kioctx, users);
    643	struct aio_kiocb *req;
    644
    645	spin_lock_irq(&ctx->ctx_lock);
    646
    647	while (!list_empty(&ctx->active_reqs)) {
    648		req = list_first_entry(&ctx->active_reqs,
    649				       struct aio_kiocb, ki_list);
    650		req->ki_cancel(&req->rw);
    651		list_del_init(&req->ki_list);
    652	}
    653
    654	spin_unlock_irq(&ctx->ctx_lock);
    655
    656	percpu_ref_kill(&ctx->reqs);
    657	percpu_ref_put(&ctx->reqs);
    658}
    659
    660static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
    661{
    662	unsigned i, new_nr;
    663	struct kioctx_table *table, *old;
    664	struct aio_ring *ring;
    665
    666	spin_lock(&mm->ioctx_lock);
    667	table = rcu_dereference_raw(mm->ioctx_table);
    668
    669	while (1) {
    670		if (table)
    671			for (i = 0; i < table->nr; i++)
    672				if (!rcu_access_pointer(table->table[i])) {
    673					ctx->id = i;
    674					rcu_assign_pointer(table->table[i], ctx);
    675					spin_unlock(&mm->ioctx_lock);
    676
    677					/* While kioctx setup is in progress,
    678					 * we are protected from page migration
    679					 * changes ring_pages by ->ring_lock.
    680					 */
    681					ring = kmap_atomic(ctx->ring_pages[0]);
    682					ring->id = ctx->id;
    683					kunmap_atomic(ring);
    684					return 0;
    685				}
    686
    687		new_nr = (table ? table->nr : 1) * 4;
    688		spin_unlock(&mm->ioctx_lock);
    689
    690		table = kzalloc(struct_size(table, table, new_nr), GFP_KERNEL);
    691		if (!table)
    692			return -ENOMEM;
    693
    694		table->nr = new_nr;
    695
    696		spin_lock(&mm->ioctx_lock);
    697		old = rcu_dereference_raw(mm->ioctx_table);
    698
    699		if (!old) {
    700			rcu_assign_pointer(mm->ioctx_table, table);
    701		} else if (table->nr > old->nr) {
    702			memcpy(table->table, old->table,
    703			       old->nr * sizeof(struct kioctx *));
    704
    705			rcu_assign_pointer(mm->ioctx_table, table);
    706			kfree_rcu(old, rcu);
    707		} else {
    708			kfree(table);
    709			table = old;
    710		}
    711	}
    712}
    713
    714static void aio_nr_sub(unsigned nr)
    715{
    716	spin_lock(&aio_nr_lock);
    717	if (WARN_ON(aio_nr - nr > aio_nr))
    718		aio_nr = 0;
    719	else
    720		aio_nr -= nr;
    721	spin_unlock(&aio_nr_lock);
    722}
    723
    724/* ioctx_alloc
    725 *	Allocates and initializes an ioctx.  Returns an ERR_PTR if it failed.
    726 */
    727static struct kioctx *ioctx_alloc(unsigned nr_events)
    728{
    729	struct mm_struct *mm = current->mm;
    730	struct kioctx *ctx;
    731	int err = -ENOMEM;
    732
    733	/*
    734	 * Store the original nr_events -- what userspace passed to io_setup(),
    735	 * for counting against the global limit -- before it changes.
    736	 */
    737	unsigned int max_reqs = nr_events;
    738
    739	/*
    740	 * We keep track of the number of available ringbuffer slots, to prevent
    741	 * overflow (reqs_available), and we also use percpu counters for this.
    742	 *
    743	 * So since up to half the slots might be on other cpu's percpu counters
    744	 * and unavailable, double nr_events so userspace sees what they
    745	 * expected: additionally, we move req_batch slots to/from percpu
    746	 * counters at a time, so make sure that isn't 0:
    747	 */
    748	nr_events = max(nr_events, num_possible_cpus() * 4);
    749	nr_events *= 2;
    750
    751	/* Prevent overflows */
    752	if (nr_events > (0x10000000U / sizeof(struct io_event))) {
    753		pr_debug("ENOMEM: nr_events too high\n");
    754		return ERR_PTR(-EINVAL);
    755	}
    756
    757	if (!nr_events || (unsigned long)max_reqs > aio_max_nr)
    758		return ERR_PTR(-EAGAIN);
    759
    760	ctx = kmem_cache_zalloc(kioctx_cachep, GFP_KERNEL);
    761	if (!ctx)
    762		return ERR_PTR(-ENOMEM);
    763
    764	ctx->max_reqs = max_reqs;
    765
    766	spin_lock_init(&ctx->ctx_lock);
    767	spin_lock_init(&ctx->completion_lock);
    768	mutex_init(&ctx->ring_lock);
    769	/* Protect against page migration throughout kiotx setup by keeping
    770	 * the ring_lock mutex held until setup is complete. */
    771	mutex_lock(&ctx->ring_lock);
    772	init_waitqueue_head(&ctx->wait);
    773
    774	INIT_LIST_HEAD(&ctx->active_reqs);
    775
    776	if (percpu_ref_init(&ctx->users, free_ioctx_users, 0, GFP_KERNEL))
    777		goto err;
    778
    779	if (percpu_ref_init(&ctx->reqs, free_ioctx_reqs, 0, GFP_KERNEL))
    780		goto err;
    781
    782	ctx->cpu = alloc_percpu(struct kioctx_cpu);
    783	if (!ctx->cpu)
    784		goto err;
    785
    786	err = aio_setup_ring(ctx, nr_events);
    787	if (err < 0)
    788		goto err;
    789
    790	atomic_set(&ctx->reqs_available, ctx->nr_events - 1);
    791	ctx->req_batch = (ctx->nr_events - 1) / (num_possible_cpus() * 4);
    792	if (ctx->req_batch < 1)
    793		ctx->req_batch = 1;
    794
    795	/* limit the number of system wide aios */
    796	spin_lock(&aio_nr_lock);
    797	if (aio_nr + ctx->max_reqs > aio_max_nr ||
    798	    aio_nr + ctx->max_reqs < aio_nr) {
    799		spin_unlock(&aio_nr_lock);
    800		err = -EAGAIN;
    801		goto err_ctx;
    802	}
    803	aio_nr += ctx->max_reqs;
    804	spin_unlock(&aio_nr_lock);
    805
    806	percpu_ref_get(&ctx->users);	/* io_setup() will drop this ref */
    807	percpu_ref_get(&ctx->reqs);	/* free_ioctx_users() will drop this */
    808
    809	err = ioctx_add_table(ctx, mm);
    810	if (err)
    811		goto err_cleanup;
    812
    813	/* Release the ring_lock mutex now that all setup is complete. */
    814	mutex_unlock(&ctx->ring_lock);
    815
    816	pr_debug("allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",
    817		 ctx, ctx->user_id, mm, ctx->nr_events);
    818	return ctx;
    819
    820err_cleanup:
    821	aio_nr_sub(ctx->max_reqs);
    822err_ctx:
    823	atomic_set(&ctx->dead, 1);
    824	if (ctx->mmap_size)
    825		vm_munmap(ctx->mmap_base, ctx->mmap_size);
    826	aio_free_ring(ctx);
    827err:
    828	mutex_unlock(&ctx->ring_lock);
    829	free_percpu(ctx->cpu);
    830	percpu_ref_exit(&ctx->reqs);
    831	percpu_ref_exit(&ctx->users);
    832	kmem_cache_free(kioctx_cachep, ctx);
    833	pr_debug("error allocating ioctx %d\n", err);
    834	return ERR_PTR(err);
    835}
    836
    837/* kill_ioctx
    838 *	Cancels all outstanding aio requests on an aio context.  Used
    839 *	when the processes owning a context have all exited to encourage
    840 *	the rapid destruction of the kioctx.
    841 */
    842static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx,
    843		      struct ctx_rq_wait *wait)
    844{
    845	struct kioctx_table *table;
    846
    847	spin_lock(&mm->ioctx_lock);
    848	if (atomic_xchg(&ctx->dead, 1)) {
    849		spin_unlock(&mm->ioctx_lock);
    850		return -EINVAL;
    851	}
    852
    853	table = rcu_dereference_raw(mm->ioctx_table);
    854	WARN_ON(ctx != rcu_access_pointer(table->table[ctx->id]));
    855	RCU_INIT_POINTER(table->table[ctx->id], NULL);
    856	spin_unlock(&mm->ioctx_lock);
    857
    858	/* free_ioctx_reqs() will do the necessary RCU synchronization */
    859	wake_up_all(&ctx->wait);
    860
    861	/*
    862	 * It'd be more correct to do this in free_ioctx(), after all
    863	 * the outstanding kiocbs have finished - but by then io_destroy
    864	 * has already returned, so io_setup() could potentially return
    865	 * -EAGAIN with no ioctxs actually in use (as far as userspace
    866	 *  could tell).
    867	 */
    868	aio_nr_sub(ctx->max_reqs);
    869
    870	if (ctx->mmap_size)
    871		vm_munmap(ctx->mmap_base, ctx->mmap_size);
    872
    873	ctx->rq_wait = wait;
    874	percpu_ref_kill(&ctx->users);
    875	return 0;
    876}
    877
    878/*
    879 * exit_aio: called when the last user of mm goes away.  At this point, there is
    880 * no way for any new requests to be submited or any of the io_* syscalls to be
    881 * called on the context.
    882 *
    883 * There may be outstanding kiocbs, but free_ioctx() will explicitly wait on
    884 * them.
    885 */
    886void exit_aio(struct mm_struct *mm)
    887{
    888	struct kioctx_table *table = rcu_dereference_raw(mm->ioctx_table);
    889	struct ctx_rq_wait wait;
    890	int i, skipped;
    891
    892	if (!table)
    893		return;
    894
    895	atomic_set(&wait.count, table->nr);
    896	init_completion(&wait.comp);
    897
    898	skipped = 0;
    899	for (i = 0; i < table->nr; ++i) {
    900		struct kioctx *ctx =
    901			rcu_dereference_protected(table->table[i], true);
    902
    903		if (!ctx) {
    904			skipped++;
    905			continue;
    906		}
    907
    908		/*
    909		 * We don't need to bother with munmap() here - exit_mmap(mm)
    910		 * is coming and it'll unmap everything. And we simply can't,
    911		 * this is not necessarily our ->mm.
    912		 * Since kill_ioctx() uses non-zero ->mmap_size as indicator
    913		 * that it needs to unmap the area, just set it to 0.
    914		 */
    915		ctx->mmap_size = 0;
    916		kill_ioctx(mm, ctx, &wait);
    917	}
    918
    919	if (!atomic_sub_and_test(skipped, &wait.count)) {
    920		/* Wait until all IO for the context are done. */
    921		wait_for_completion(&wait.comp);
    922	}
    923
    924	RCU_INIT_POINTER(mm->ioctx_table, NULL);
    925	kfree(table);
    926}
    927
    928static void put_reqs_available(struct kioctx *ctx, unsigned nr)
    929{
    930	struct kioctx_cpu *kcpu;
    931	unsigned long flags;
    932
    933	local_irq_save(flags);
    934	kcpu = this_cpu_ptr(ctx->cpu);
    935	kcpu->reqs_available += nr;
    936
    937	while (kcpu->reqs_available >= ctx->req_batch * 2) {
    938		kcpu->reqs_available -= ctx->req_batch;
    939		atomic_add(ctx->req_batch, &ctx->reqs_available);
    940	}
    941
    942	local_irq_restore(flags);
    943}
    944
    945static bool __get_reqs_available(struct kioctx *ctx)
    946{
    947	struct kioctx_cpu *kcpu;
    948	bool ret = false;
    949	unsigned long flags;
    950
    951	local_irq_save(flags);
    952	kcpu = this_cpu_ptr(ctx->cpu);
    953	if (!kcpu->reqs_available) {
    954		int old, avail = atomic_read(&ctx->reqs_available);
    955
    956		do {
    957			if (avail < ctx->req_batch)
    958				goto out;
    959
    960			old = avail;
    961			avail = atomic_cmpxchg(&ctx->reqs_available,
    962					       avail, avail - ctx->req_batch);
    963		} while (avail != old);
    964
    965		kcpu->reqs_available += ctx->req_batch;
    966	}
    967
    968	ret = true;
    969	kcpu->reqs_available--;
    970out:
    971	local_irq_restore(flags);
    972	return ret;
    973}
    974
    975/* refill_reqs_available
    976 *	Updates the reqs_available reference counts used for tracking the
    977 *	number of free slots in the completion ring.  This can be called
    978 *	from aio_complete() (to optimistically update reqs_available) or
    979 *	from aio_get_req() (the we're out of events case).  It must be
    980 *	called holding ctx->completion_lock.
    981 */
    982static void refill_reqs_available(struct kioctx *ctx, unsigned head,
    983                                  unsigned tail)
    984{
    985	unsigned events_in_ring, completed;
    986
    987	/* Clamp head since userland can write to it. */
    988	head %= ctx->nr_events;
    989	if (head <= tail)
    990		events_in_ring = tail - head;
    991	else
    992		events_in_ring = ctx->nr_events - (head - tail);
    993
    994	completed = ctx->completed_events;
    995	if (events_in_ring < completed)
    996		completed -= events_in_ring;
    997	else
    998		completed = 0;
    999
   1000	if (!completed)
   1001		return;
   1002
   1003	ctx->completed_events -= completed;
   1004	put_reqs_available(ctx, completed);
   1005}
   1006
   1007/* user_refill_reqs_available
   1008 *	Called to refill reqs_available when aio_get_req() encounters an
   1009 *	out of space in the completion ring.
   1010 */
   1011static void user_refill_reqs_available(struct kioctx *ctx)
   1012{
   1013	spin_lock_irq(&ctx->completion_lock);
   1014	if (ctx->completed_events) {
   1015		struct aio_ring *ring;
   1016		unsigned head;
   1017
   1018		/* Access of ring->head may race with aio_read_events_ring()
   1019		 * here, but that's okay since whether we read the old version
   1020		 * or the new version, and either will be valid.  The important
   1021		 * part is that head cannot pass tail since we prevent
   1022		 * aio_complete() from updating tail by holding
   1023		 * ctx->completion_lock.  Even if head is invalid, the check
   1024		 * against ctx->completed_events below will make sure we do the
   1025		 * safe/right thing.
   1026		 */
   1027		ring = kmap_atomic(ctx->ring_pages[0]);
   1028		head = ring->head;
   1029		kunmap_atomic(ring);
   1030
   1031		refill_reqs_available(ctx, head, ctx->tail);
   1032	}
   1033
   1034	spin_unlock_irq(&ctx->completion_lock);
   1035}
   1036
   1037static bool get_reqs_available(struct kioctx *ctx)
   1038{
   1039	if (__get_reqs_available(ctx))
   1040		return true;
   1041	user_refill_reqs_available(ctx);
   1042	return __get_reqs_available(ctx);
   1043}
   1044
   1045/* aio_get_req
   1046 *	Allocate a slot for an aio request.
   1047 * Returns NULL if no requests are free.
   1048 *
   1049 * The refcount is initialized to 2 - one for the async op completion,
   1050 * one for the synchronous code that does this.
   1051 */
   1052static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx)
   1053{
   1054	struct aio_kiocb *req;
   1055
   1056	req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL);
   1057	if (unlikely(!req))
   1058		return NULL;
   1059
   1060	if (unlikely(!get_reqs_available(ctx))) {
   1061		kmem_cache_free(kiocb_cachep, req);
   1062		return NULL;
   1063	}
   1064
   1065	percpu_ref_get(&ctx->reqs);
   1066	req->ki_ctx = ctx;
   1067	INIT_LIST_HEAD(&req->ki_list);
   1068	refcount_set(&req->ki_refcnt, 2);
   1069	req->ki_eventfd = NULL;
   1070	return req;
   1071}
   1072
   1073static struct kioctx *lookup_ioctx(unsigned long ctx_id)
   1074{
   1075	struct aio_ring __user *ring  = (void __user *)ctx_id;
   1076	struct mm_struct *mm = current->mm;
   1077	struct kioctx *ctx, *ret = NULL;
   1078	struct kioctx_table *table;
   1079	unsigned id;
   1080
   1081	if (get_user(id, &ring->id))
   1082		return NULL;
   1083
   1084	rcu_read_lock();
   1085	table = rcu_dereference(mm->ioctx_table);
   1086
   1087	if (!table || id >= table->nr)
   1088		goto out;
   1089
   1090	id = array_index_nospec(id, table->nr);
   1091	ctx = rcu_dereference(table->table[id]);
   1092	if (ctx && ctx->user_id == ctx_id) {
   1093		if (percpu_ref_tryget_live(&ctx->users))
   1094			ret = ctx;
   1095	}
   1096out:
   1097	rcu_read_unlock();
   1098	return ret;
   1099}
   1100
   1101static inline void iocb_destroy(struct aio_kiocb *iocb)
   1102{
   1103	if (iocb->ki_eventfd)
   1104		eventfd_ctx_put(iocb->ki_eventfd);
   1105	if (iocb->ki_filp)
   1106		fput(iocb->ki_filp);
   1107	percpu_ref_put(&iocb->ki_ctx->reqs);
   1108	kmem_cache_free(kiocb_cachep, iocb);
   1109}
   1110
   1111/* aio_complete
   1112 *	Called when the io request on the given iocb is complete.
   1113 */
   1114static void aio_complete(struct aio_kiocb *iocb)
   1115{
   1116	struct kioctx	*ctx = iocb->ki_ctx;
   1117	struct aio_ring	*ring;
   1118	struct io_event	*ev_page, *event;
   1119	unsigned tail, pos, head;
   1120	unsigned long	flags;
   1121
   1122	/*
   1123	 * Add a completion event to the ring buffer. Must be done holding
   1124	 * ctx->completion_lock to prevent other code from messing with the tail
   1125	 * pointer since we might be called from irq context.
   1126	 */
   1127	spin_lock_irqsave(&ctx->completion_lock, flags);
   1128
   1129	tail = ctx->tail;
   1130	pos = tail + AIO_EVENTS_OFFSET;
   1131
   1132	if (++tail >= ctx->nr_events)
   1133		tail = 0;
   1134
   1135	ev_page = kmap_atomic(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
   1136	event = ev_page + pos % AIO_EVENTS_PER_PAGE;
   1137
   1138	*event = iocb->ki_res;
   1139
   1140	kunmap_atomic(ev_page);
   1141	flush_dcache_page(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
   1142
   1143	pr_debug("%p[%u]: %p: %p %Lx %Lx %Lx\n", ctx, tail, iocb,
   1144		 (void __user *)(unsigned long)iocb->ki_res.obj,
   1145		 iocb->ki_res.data, iocb->ki_res.res, iocb->ki_res.res2);
   1146
   1147	/* after flagging the request as done, we
   1148	 * must never even look at it again
   1149	 */
   1150	smp_wmb();	/* make event visible before updating tail */
   1151
   1152	ctx->tail = tail;
   1153
   1154	ring = kmap_atomic(ctx->ring_pages[0]);
   1155	head = ring->head;
   1156	ring->tail = tail;
   1157	kunmap_atomic(ring);
   1158	flush_dcache_page(ctx->ring_pages[0]);
   1159
   1160	ctx->completed_events++;
   1161	if (ctx->completed_events > 1)
   1162		refill_reqs_available(ctx, head, tail);
   1163	spin_unlock_irqrestore(&ctx->completion_lock, flags);
   1164
   1165	pr_debug("added to ring %p at [%u]\n", iocb, tail);
   1166
   1167	/*
   1168	 * Check if the user asked us to deliver the result through an
   1169	 * eventfd. The eventfd_signal() function is safe to be called
   1170	 * from IRQ context.
   1171	 */
   1172	if (iocb->ki_eventfd)
   1173		eventfd_signal(iocb->ki_eventfd, 1);
   1174
   1175	/*
   1176	 * We have to order our ring_info tail store above and test
   1177	 * of the wait list below outside the wait lock.  This is
   1178	 * like in wake_up_bit() where clearing a bit has to be
   1179	 * ordered with the unlocked test.
   1180	 */
   1181	smp_mb();
   1182
   1183	if (waitqueue_active(&ctx->wait))
   1184		wake_up(&ctx->wait);
   1185}
   1186
   1187static inline void iocb_put(struct aio_kiocb *iocb)
   1188{
   1189	if (refcount_dec_and_test(&iocb->ki_refcnt)) {
   1190		aio_complete(iocb);
   1191		iocb_destroy(iocb);
   1192	}
   1193}
   1194
   1195/* aio_read_events_ring
   1196 *	Pull an event off of the ioctx's event ring.  Returns the number of
   1197 *	events fetched
   1198 */
   1199static long aio_read_events_ring(struct kioctx *ctx,
   1200				 struct io_event __user *event, long nr)
   1201{
   1202	struct aio_ring *ring;
   1203	unsigned head, tail, pos;
   1204	long ret = 0;
   1205	int copy_ret;
   1206
   1207	/*
   1208	 * The mutex can block and wake us up and that will cause
   1209	 * wait_event_interruptible_hrtimeout() to schedule without sleeping
   1210	 * and repeat. This should be rare enough that it doesn't cause
   1211	 * peformance issues. See the comment in read_events() for more detail.
   1212	 */
   1213	sched_annotate_sleep();
   1214	mutex_lock(&ctx->ring_lock);
   1215
   1216	/* Access to ->ring_pages here is protected by ctx->ring_lock. */
   1217	ring = kmap_atomic(ctx->ring_pages[0]);
   1218	head = ring->head;
   1219	tail = ring->tail;
   1220	kunmap_atomic(ring);
   1221
   1222	/*
   1223	 * Ensure that once we've read the current tail pointer, that
   1224	 * we also see the events that were stored up to the tail.
   1225	 */
   1226	smp_rmb();
   1227
   1228	pr_debug("h%u t%u m%u\n", head, tail, ctx->nr_events);
   1229
   1230	if (head == tail)
   1231		goto out;
   1232
   1233	head %= ctx->nr_events;
   1234	tail %= ctx->nr_events;
   1235
   1236	while (ret < nr) {
   1237		long avail;
   1238		struct io_event *ev;
   1239		struct page *page;
   1240
   1241		avail = (head <= tail ?  tail : ctx->nr_events) - head;
   1242		if (head == tail)
   1243			break;
   1244
   1245		pos = head + AIO_EVENTS_OFFSET;
   1246		page = ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE];
   1247		pos %= AIO_EVENTS_PER_PAGE;
   1248
   1249		avail = min(avail, nr - ret);
   1250		avail = min_t(long, avail, AIO_EVENTS_PER_PAGE - pos);
   1251
   1252		ev = kmap(page);
   1253		copy_ret = copy_to_user(event + ret, ev + pos,
   1254					sizeof(*ev) * avail);
   1255		kunmap(page);
   1256
   1257		if (unlikely(copy_ret)) {
   1258			ret = -EFAULT;
   1259			goto out;
   1260		}
   1261
   1262		ret += avail;
   1263		head += avail;
   1264		head %= ctx->nr_events;
   1265	}
   1266
   1267	ring = kmap_atomic(ctx->ring_pages[0]);
   1268	ring->head = head;
   1269	kunmap_atomic(ring);
   1270	flush_dcache_page(ctx->ring_pages[0]);
   1271
   1272	pr_debug("%li  h%u t%u\n", ret, head, tail);
   1273out:
   1274	mutex_unlock(&ctx->ring_lock);
   1275
   1276	return ret;
   1277}
   1278
   1279static bool aio_read_events(struct kioctx *ctx, long min_nr, long nr,
   1280			    struct io_event __user *event, long *i)
   1281{
   1282	long ret = aio_read_events_ring(ctx, event + *i, nr - *i);
   1283
   1284	if (ret > 0)
   1285		*i += ret;
   1286
   1287	if (unlikely(atomic_read(&ctx->dead)))
   1288		ret = -EINVAL;
   1289
   1290	if (!*i)
   1291		*i = ret;
   1292
   1293	return ret < 0 || *i >= min_nr;
   1294}
   1295
   1296static long read_events(struct kioctx *ctx, long min_nr, long nr,
   1297			struct io_event __user *event,
   1298			ktime_t until)
   1299{
   1300	long ret = 0;
   1301
   1302	/*
   1303	 * Note that aio_read_events() is being called as the conditional - i.e.
   1304	 * we're calling it after prepare_to_wait() has set task state to
   1305	 * TASK_INTERRUPTIBLE.
   1306	 *
   1307	 * But aio_read_events() can block, and if it blocks it's going to flip
   1308	 * the task state back to TASK_RUNNING.
   1309	 *
   1310	 * This should be ok, provided it doesn't flip the state back to
   1311	 * TASK_RUNNING and return 0 too much - that causes us to spin. That
   1312	 * will only happen if the mutex_lock() call blocks, and we then find
   1313	 * the ringbuffer empty. So in practice we should be ok, but it's
   1314	 * something to be aware of when touching this code.
   1315	 */
   1316	if (until == 0)
   1317		aio_read_events(ctx, min_nr, nr, event, &ret);
   1318	else
   1319		wait_event_interruptible_hrtimeout(ctx->wait,
   1320				aio_read_events(ctx, min_nr, nr, event, &ret),
   1321				until);
   1322	return ret;
   1323}
   1324
   1325/* sys_io_setup:
   1326 *	Create an aio_context capable of receiving at least nr_events.
   1327 *	ctxp must not point to an aio_context that already exists, and
   1328 *	must be initialized to 0 prior to the call.  On successful
   1329 *	creation of the aio_context, *ctxp is filled in with the resulting 
   1330 *	handle.  May fail with -EINVAL if *ctxp is not initialized,
   1331 *	if the specified nr_events exceeds internal limits.  May fail 
   1332 *	with -EAGAIN if the specified nr_events exceeds the user's limit 
   1333 *	of available events.  May fail with -ENOMEM if insufficient kernel
   1334 *	resources are available.  May fail with -EFAULT if an invalid
   1335 *	pointer is passed for ctxp.  Will fail with -ENOSYS if not
   1336 *	implemented.
   1337 */
   1338SYSCALL_DEFINE2(io_setup, unsigned, nr_events, aio_context_t __user *, ctxp)
   1339{
   1340	struct kioctx *ioctx = NULL;
   1341	unsigned long ctx;
   1342	long ret;
   1343
   1344	ret = get_user(ctx, ctxp);
   1345	if (unlikely(ret))
   1346		goto out;
   1347
   1348	ret = -EINVAL;
   1349	if (unlikely(ctx || nr_events == 0)) {
   1350		pr_debug("EINVAL: ctx %lu nr_events %u\n",
   1351		         ctx, nr_events);
   1352		goto out;
   1353	}
   1354
   1355	ioctx = ioctx_alloc(nr_events);
   1356	ret = PTR_ERR(ioctx);
   1357	if (!IS_ERR(ioctx)) {
   1358		ret = put_user(ioctx->user_id, ctxp);
   1359		if (ret)
   1360			kill_ioctx(current->mm, ioctx, NULL);
   1361		percpu_ref_put(&ioctx->users);
   1362	}
   1363
   1364out:
   1365	return ret;
   1366}
   1367
   1368#ifdef CONFIG_COMPAT
   1369COMPAT_SYSCALL_DEFINE2(io_setup, unsigned, nr_events, u32 __user *, ctx32p)
   1370{
   1371	struct kioctx *ioctx = NULL;
   1372	unsigned long ctx;
   1373	long ret;
   1374
   1375	ret = get_user(ctx, ctx32p);
   1376	if (unlikely(ret))
   1377		goto out;
   1378
   1379	ret = -EINVAL;
   1380	if (unlikely(ctx || nr_events == 0)) {
   1381		pr_debug("EINVAL: ctx %lu nr_events %u\n",
   1382		         ctx, nr_events);
   1383		goto out;
   1384	}
   1385
   1386	ioctx = ioctx_alloc(nr_events);
   1387	ret = PTR_ERR(ioctx);
   1388	if (!IS_ERR(ioctx)) {
   1389		/* truncating is ok because it's a user address */
   1390		ret = put_user((u32)ioctx->user_id, ctx32p);
   1391		if (ret)
   1392			kill_ioctx(current->mm, ioctx, NULL);
   1393		percpu_ref_put(&ioctx->users);
   1394	}
   1395
   1396out:
   1397	return ret;
   1398}
   1399#endif
   1400
   1401/* sys_io_destroy:
   1402 *	Destroy the aio_context specified.  May cancel any outstanding 
   1403 *	AIOs and block on completion.  Will fail with -ENOSYS if not
   1404 *	implemented.  May fail with -EINVAL if the context pointed to
   1405 *	is invalid.
   1406 */
   1407SYSCALL_DEFINE1(io_destroy, aio_context_t, ctx)
   1408{
   1409	struct kioctx *ioctx = lookup_ioctx(ctx);
   1410	if (likely(NULL != ioctx)) {
   1411		struct ctx_rq_wait wait;
   1412		int ret;
   1413
   1414		init_completion(&wait.comp);
   1415		atomic_set(&wait.count, 1);
   1416
   1417		/* Pass requests_done to kill_ioctx() where it can be set
   1418		 * in a thread-safe way. If we try to set it here then we have
   1419		 * a race condition if two io_destroy() called simultaneously.
   1420		 */
   1421		ret = kill_ioctx(current->mm, ioctx, &wait);
   1422		percpu_ref_put(&ioctx->users);
   1423
   1424		/* Wait until all IO for the context are done. Otherwise kernel
   1425		 * keep using user-space buffers even if user thinks the context
   1426		 * is destroyed.
   1427		 */
   1428		if (!ret)
   1429			wait_for_completion(&wait.comp);
   1430
   1431		return ret;
   1432	}
   1433	pr_debug("EINVAL: invalid context id\n");
   1434	return -EINVAL;
   1435}
   1436
   1437static void aio_remove_iocb(struct aio_kiocb *iocb)
   1438{
   1439	struct kioctx *ctx = iocb->ki_ctx;
   1440	unsigned long flags;
   1441
   1442	spin_lock_irqsave(&ctx->ctx_lock, flags);
   1443	list_del(&iocb->ki_list);
   1444	spin_unlock_irqrestore(&ctx->ctx_lock, flags);
   1445}
   1446
   1447static void aio_complete_rw(struct kiocb *kiocb, long res)
   1448{
   1449	struct aio_kiocb *iocb = container_of(kiocb, struct aio_kiocb, rw);
   1450
   1451	if (!list_empty_careful(&iocb->ki_list))
   1452		aio_remove_iocb(iocb);
   1453
   1454	if (kiocb->ki_flags & IOCB_WRITE) {
   1455		struct inode *inode = file_inode(kiocb->ki_filp);
   1456
   1457		/*
   1458		 * Tell lockdep we inherited freeze protection from submission
   1459		 * thread.
   1460		 */
   1461		if (S_ISREG(inode->i_mode))
   1462			__sb_writers_acquired(inode->i_sb, SB_FREEZE_WRITE);
   1463		file_end_write(kiocb->ki_filp);
   1464	}
   1465
   1466	iocb->ki_res.res = res;
   1467	iocb->ki_res.res2 = 0;
   1468	iocb_put(iocb);
   1469}
   1470
   1471static int aio_prep_rw(struct kiocb *req, const struct iocb *iocb)
   1472{
   1473	int ret;
   1474
   1475	req->ki_complete = aio_complete_rw;
   1476	req->private = NULL;
   1477	req->ki_pos = iocb->aio_offset;
   1478	req->ki_flags = iocb_flags(req->ki_filp);
   1479	if (iocb->aio_flags & IOCB_FLAG_RESFD)
   1480		req->ki_flags |= IOCB_EVENTFD;
   1481	if (iocb->aio_flags & IOCB_FLAG_IOPRIO) {
   1482		/*
   1483		 * If the IOCB_FLAG_IOPRIO flag of aio_flags is set, then
   1484		 * aio_reqprio is interpreted as an I/O scheduling
   1485		 * class and priority.
   1486		 */
   1487		ret = ioprio_check_cap(iocb->aio_reqprio);
   1488		if (ret) {
   1489			pr_debug("aio ioprio check cap error: %d\n", ret);
   1490			return ret;
   1491		}
   1492
   1493		req->ki_ioprio = iocb->aio_reqprio;
   1494	} else
   1495		req->ki_ioprio = get_current_ioprio();
   1496
   1497	ret = kiocb_set_rw_flags(req, iocb->aio_rw_flags);
   1498	if (unlikely(ret))
   1499		return ret;
   1500
   1501	req->ki_flags &= ~IOCB_HIPRI; /* no one is going to poll for this I/O */
   1502	return 0;
   1503}
   1504
   1505static ssize_t aio_setup_rw(int rw, const struct iocb *iocb,
   1506		struct iovec **iovec, bool vectored, bool compat,
   1507		struct iov_iter *iter)
   1508{
   1509	void __user *buf = (void __user *)(uintptr_t)iocb->aio_buf;
   1510	size_t len = iocb->aio_nbytes;
   1511
   1512	if (!vectored) {
   1513		ssize_t ret = import_single_range(rw, buf, len, *iovec, iter);
   1514		*iovec = NULL;
   1515		return ret;
   1516	}
   1517
   1518	return __import_iovec(rw, buf, len, UIO_FASTIOV, iovec, iter, compat);
   1519}
   1520
   1521static inline void aio_rw_done(struct kiocb *req, ssize_t ret)
   1522{
   1523	switch (ret) {
   1524	case -EIOCBQUEUED:
   1525		break;
   1526	case -ERESTARTSYS:
   1527	case -ERESTARTNOINTR:
   1528	case -ERESTARTNOHAND:
   1529	case -ERESTART_RESTARTBLOCK:
   1530		/*
   1531		 * There's no easy way to restart the syscall since other AIO's
   1532		 * may be already running. Just fail this IO with EINTR.
   1533		 */
   1534		ret = -EINTR;
   1535		fallthrough;
   1536	default:
   1537		req->ki_complete(req, ret);
   1538	}
   1539}
   1540
   1541static int aio_read(struct kiocb *req, const struct iocb *iocb,
   1542			bool vectored, bool compat)
   1543{
   1544	struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
   1545	struct iov_iter iter;
   1546	struct file *file;
   1547	int ret;
   1548
   1549	ret = aio_prep_rw(req, iocb);
   1550	if (ret)
   1551		return ret;
   1552	file = req->ki_filp;
   1553	if (unlikely(!(file->f_mode & FMODE_READ)))
   1554		return -EBADF;
   1555	if (unlikely(!file->f_op->read_iter))
   1556		return -EINVAL;
   1557
   1558	ret = aio_setup_rw(READ, iocb, &iovec, vectored, compat, &iter);
   1559	if (ret < 0)
   1560		return ret;
   1561	ret = rw_verify_area(READ, file, &req->ki_pos, iov_iter_count(&iter));
   1562	if (!ret)
   1563		aio_rw_done(req, call_read_iter(file, req, &iter));
   1564	kfree(iovec);
   1565	return ret;
   1566}
   1567
   1568static int aio_write(struct kiocb *req, const struct iocb *iocb,
   1569			 bool vectored, bool compat)
   1570{
   1571	struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
   1572	struct iov_iter iter;
   1573	struct file *file;
   1574	int ret;
   1575
   1576	ret = aio_prep_rw(req, iocb);
   1577	if (ret)
   1578		return ret;
   1579	file = req->ki_filp;
   1580
   1581	if (unlikely(!(file->f_mode & FMODE_WRITE)))
   1582		return -EBADF;
   1583	if (unlikely(!file->f_op->write_iter))
   1584		return -EINVAL;
   1585
   1586	ret = aio_setup_rw(WRITE, iocb, &iovec, vectored, compat, &iter);
   1587	if (ret < 0)
   1588		return ret;
   1589	ret = rw_verify_area(WRITE, file, &req->ki_pos, iov_iter_count(&iter));
   1590	if (!ret) {
   1591		/*
   1592		 * Open-code file_start_write here to grab freeze protection,
   1593		 * which will be released by another thread in
   1594		 * aio_complete_rw().  Fool lockdep by telling it the lock got
   1595		 * released so that it doesn't complain about the held lock when
   1596		 * we return to userspace.
   1597		 */
   1598		if (S_ISREG(file_inode(file)->i_mode)) {
   1599			sb_start_write(file_inode(file)->i_sb);
   1600			__sb_writers_release(file_inode(file)->i_sb, SB_FREEZE_WRITE);
   1601		}
   1602		req->ki_flags |= IOCB_WRITE;
   1603		aio_rw_done(req, call_write_iter(file, req, &iter));
   1604	}
   1605	kfree(iovec);
   1606	return ret;
   1607}
   1608
   1609static void aio_fsync_work(struct work_struct *work)
   1610{
   1611	struct aio_kiocb *iocb = container_of(work, struct aio_kiocb, fsync.work);
   1612	const struct cred *old_cred = override_creds(iocb->fsync.creds);
   1613
   1614	iocb->ki_res.res = vfs_fsync(iocb->fsync.file, iocb->fsync.datasync);
   1615	revert_creds(old_cred);
   1616	put_cred(iocb->fsync.creds);
   1617	iocb_put(iocb);
   1618}
   1619
   1620static int aio_fsync(struct fsync_iocb *req, const struct iocb *iocb,
   1621		     bool datasync)
   1622{
   1623	if (unlikely(iocb->aio_buf || iocb->aio_offset || iocb->aio_nbytes ||
   1624			iocb->aio_rw_flags))
   1625		return -EINVAL;
   1626
   1627	if (unlikely(!req->file->f_op->fsync))
   1628		return -EINVAL;
   1629
   1630	req->creds = prepare_creds();
   1631	if (!req->creds)
   1632		return -ENOMEM;
   1633
   1634	req->datasync = datasync;
   1635	INIT_WORK(&req->work, aio_fsync_work);
   1636	schedule_work(&req->work);
   1637	return 0;
   1638}
   1639
   1640static void aio_poll_put_work(struct work_struct *work)
   1641{
   1642	struct poll_iocb *req = container_of(work, struct poll_iocb, work);
   1643	struct aio_kiocb *iocb = container_of(req, struct aio_kiocb, poll);
   1644
   1645	iocb_put(iocb);
   1646}
   1647
   1648/*
   1649 * Safely lock the waitqueue which the request is on, synchronizing with the
   1650 * case where the ->poll() provider decides to free its waitqueue early.
   1651 *
   1652 * Returns true on success, meaning that req->head->lock was locked, req->wait
   1653 * is on req->head, and an RCU read lock was taken.  Returns false if the
   1654 * request was already removed from its waitqueue (which might no longer exist).
   1655 */
   1656static bool poll_iocb_lock_wq(struct poll_iocb *req)
   1657{
   1658	wait_queue_head_t *head;
   1659
   1660	/*
   1661	 * While we hold the waitqueue lock and the waitqueue is nonempty,
   1662	 * wake_up_pollfree() will wait for us.  However, taking the waitqueue
   1663	 * lock in the first place can race with the waitqueue being freed.
   1664	 *
   1665	 * We solve this as eventpoll does: by taking advantage of the fact that
   1666	 * all users of wake_up_pollfree() will RCU-delay the actual free.  If
   1667	 * we enter rcu_read_lock() and see that the pointer to the queue is
   1668	 * non-NULL, we can then lock it without the memory being freed out from
   1669	 * under us, then check whether the request is still on the queue.
   1670	 *
   1671	 * Keep holding rcu_read_lock() as long as we hold the queue lock, in
   1672	 * case the caller deletes the entry from the queue, leaving it empty.
   1673	 * In that case, only RCU prevents the queue memory from being freed.
   1674	 */
   1675	rcu_read_lock();
   1676	head = smp_load_acquire(&req->head);
   1677	if (head) {
   1678		spin_lock(&head->lock);
   1679		if (!list_empty(&req->wait.entry))
   1680			return true;
   1681		spin_unlock(&head->lock);
   1682	}
   1683	rcu_read_unlock();
   1684	return false;
   1685}
   1686
   1687static void poll_iocb_unlock_wq(struct poll_iocb *req)
   1688{
   1689	spin_unlock(&req->head->lock);
   1690	rcu_read_unlock();
   1691}
   1692
   1693static void aio_poll_complete_work(struct work_struct *work)
   1694{
   1695	struct poll_iocb *req = container_of(work, struct poll_iocb, work);
   1696	struct aio_kiocb *iocb = container_of(req, struct aio_kiocb, poll);
   1697	struct poll_table_struct pt = { ._key = req->events };
   1698	struct kioctx *ctx = iocb->ki_ctx;
   1699	__poll_t mask = 0;
   1700
   1701	if (!READ_ONCE(req->cancelled))
   1702		mask = vfs_poll(req->file, &pt) & req->events;
   1703
   1704	/*
   1705	 * Note that ->ki_cancel callers also delete iocb from active_reqs after
   1706	 * calling ->ki_cancel.  We need the ctx_lock roundtrip here to
   1707	 * synchronize with them.  In the cancellation case the list_del_init
   1708	 * itself is not actually needed, but harmless so we keep it in to
   1709	 * avoid further branches in the fast path.
   1710	 */
   1711	spin_lock_irq(&ctx->ctx_lock);
   1712	if (poll_iocb_lock_wq(req)) {
   1713		if (!mask && !READ_ONCE(req->cancelled)) {
   1714			/*
   1715			 * The request isn't actually ready to be completed yet.
   1716			 * Reschedule completion if another wakeup came in.
   1717			 */
   1718			if (req->work_need_resched) {
   1719				schedule_work(&req->work);
   1720				req->work_need_resched = false;
   1721			} else {
   1722				req->work_scheduled = false;
   1723			}
   1724			poll_iocb_unlock_wq(req);
   1725			spin_unlock_irq(&ctx->ctx_lock);
   1726			return;
   1727		}
   1728		list_del_init(&req->wait.entry);
   1729		poll_iocb_unlock_wq(req);
   1730	} /* else, POLLFREE has freed the waitqueue, so we must complete */
   1731	list_del_init(&iocb->ki_list);
   1732	iocb->ki_res.res = mangle_poll(mask);
   1733	spin_unlock_irq(&ctx->ctx_lock);
   1734
   1735	iocb_put(iocb);
   1736}
   1737
   1738/* assumes we are called with irqs disabled */
   1739static int aio_poll_cancel(struct kiocb *iocb)
   1740{
   1741	struct aio_kiocb *aiocb = container_of(iocb, struct aio_kiocb, rw);
   1742	struct poll_iocb *req = &aiocb->poll;
   1743
   1744	if (poll_iocb_lock_wq(req)) {
   1745		WRITE_ONCE(req->cancelled, true);
   1746		if (!req->work_scheduled) {
   1747			schedule_work(&aiocb->poll.work);
   1748			req->work_scheduled = true;
   1749		}
   1750		poll_iocb_unlock_wq(req);
   1751	} /* else, the request was force-cancelled by POLLFREE already */
   1752
   1753	return 0;
   1754}
   1755
   1756static int aio_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
   1757		void *key)
   1758{
   1759	struct poll_iocb *req = container_of(wait, struct poll_iocb, wait);
   1760	struct aio_kiocb *iocb = container_of(req, struct aio_kiocb, poll);
   1761	__poll_t mask = key_to_poll(key);
   1762	unsigned long flags;
   1763
   1764	/* for instances that support it check for an event match first: */
   1765	if (mask && !(mask & req->events))
   1766		return 0;
   1767
   1768	/*
   1769	 * Complete the request inline if possible.  This requires that three
   1770	 * conditions be met:
   1771	 *   1. An event mask must have been passed.  If a plain wakeup was done
   1772	 *	instead, then mask == 0 and we have to call vfs_poll() to get
   1773	 *	the events, so inline completion isn't possible.
   1774	 *   2. The completion work must not have already been scheduled.
   1775	 *   3. ctx_lock must not be busy.  We have to use trylock because we
   1776	 *	already hold the waitqueue lock, so this inverts the normal
   1777	 *	locking order.  Use irqsave/irqrestore because not all
   1778	 *	filesystems (e.g. fuse) call this function with IRQs disabled,
   1779	 *	yet IRQs have to be disabled before ctx_lock is obtained.
   1780	 */
   1781	if (mask && !req->work_scheduled &&
   1782	    spin_trylock_irqsave(&iocb->ki_ctx->ctx_lock, flags)) {
   1783		struct kioctx *ctx = iocb->ki_ctx;
   1784
   1785		list_del_init(&req->wait.entry);
   1786		list_del(&iocb->ki_list);
   1787		iocb->ki_res.res = mangle_poll(mask);
   1788		if (iocb->ki_eventfd && !eventfd_signal_allowed()) {
   1789			iocb = NULL;
   1790			INIT_WORK(&req->work, aio_poll_put_work);
   1791			schedule_work(&req->work);
   1792		}
   1793		spin_unlock_irqrestore(&ctx->ctx_lock, flags);
   1794		if (iocb)
   1795			iocb_put(iocb);
   1796	} else {
   1797		/*
   1798		 * Schedule the completion work if needed.  If it was already
   1799		 * scheduled, record that another wakeup came in.
   1800		 *
   1801		 * Don't remove the request from the waitqueue here, as it might
   1802		 * not actually be complete yet (we won't know until vfs_poll()
   1803		 * is called), and we must not miss any wakeups.  POLLFREE is an
   1804		 * exception to this; see below.
   1805		 */
   1806		if (req->work_scheduled) {
   1807			req->work_need_resched = true;
   1808		} else {
   1809			schedule_work(&req->work);
   1810			req->work_scheduled = true;
   1811		}
   1812
   1813		/*
   1814		 * If the waitqueue is being freed early but we can't complete
   1815		 * the request inline, we have to tear down the request as best
   1816		 * we can.  That means immediately removing the request from its
   1817		 * waitqueue and preventing all further accesses to the
   1818		 * waitqueue via the request.  We also need to schedule the
   1819		 * completion work (done above).  Also mark the request as
   1820		 * cancelled, to potentially skip an unneeded call to ->poll().
   1821		 */
   1822		if (mask & POLLFREE) {
   1823			WRITE_ONCE(req->cancelled, true);
   1824			list_del_init(&req->wait.entry);
   1825
   1826			/*
   1827			 * Careful: this *must* be the last step, since as soon
   1828			 * as req->head is NULL'ed out, the request can be
   1829			 * completed and freed, since aio_poll_complete_work()
   1830			 * will no longer need to take the waitqueue lock.
   1831			 */
   1832			smp_store_release(&req->head, NULL);
   1833		}
   1834	}
   1835	return 1;
   1836}
   1837
   1838struct aio_poll_table {
   1839	struct poll_table_struct	pt;
   1840	struct aio_kiocb		*iocb;
   1841	bool				queued;
   1842	int				error;
   1843};
   1844
   1845static void
   1846aio_poll_queue_proc(struct file *file, struct wait_queue_head *head,
   1847		struct poll_table_struct *p)
   1848{
   1849	struct aio_poll_table *pt = container_of(p, struct aio_poll_table, pt);
   1850
   1851	/* multiple wait queues per file are not supported */
   1852	if (unlikely(pt->queued)) {
   1853		pt->error = -EINVAL;
   1854		return;
   1855	}
   1856
   1857	pt->queued = true;
   1858	pt->error = 0;
   1859	pt->iocb->poll.head = head;
   1860	add_wait_queue(head, &pt->iocb->poll.wait);
   1861}
   1862
   1863static int aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb)
   1864{
   1865	struct kioctx *ctx = aiocb->ki_ctx;
   1866	struct poll_iocb *req = &aiocb->poll;
   1867	struct aio_poll_table apt;
   1868	bool cancel = false;
   1869	__poll_t mask;
   1870
   1871	/* reject any unknown events outside the normal event mask. */
   1872	if ((u16)iocb->aio_buf != iocb->aio_buf)
   1873		return -EINVAL;
   1874	/* reject fields that are not defined for poll */
   1875	if (iocb->aio_offset || iocb->aio_nbytes || iocb->aio_rw_flags)
   1876		return -EINVAL;
   1877
   1878	INIT_WORK(&req->work, aio_poll_complete_work);
   1879	req->events = demangle_poll(iocb->aio_buf) | EPOLLERR | EPOLLHUP;
   1880
   1881	req->head = NULL;
   1882	req->cancelled = false;
   1883	req->work_scheduled = false;
   1884	req->work_need_resched = false;
   1885
   1886	apt.pt._qproc = aio_poll_queue_proc;
   1887	apt.pt._key = req->events;
   1888	apt.iocb = aiocb;
   1889	apt.queued = false;
   1890	apt.error = -EINVAL; /* same as no support for IOCB_CMD_POLL */
   1891
   1892	/* initialized the list so that we can do list_empty checks */
   1893	INIT_LIST_HEAD(&req->wait.entry);
   1894	init_waitqueue_func_entry(&req->wait, aio_poll_wake);
   1895
   1896	mask = vfs_poll(req->file, &apt.pt) & req->events;
   1897	spin_lock_irq(&ctx->ctx_lock);
   1898	if (likely(apt.queued)) {
   1899		bool on_queue = poll_iocb_lock_wq(req);
   1900
   1901		if (!on_queue || req->work_scheduled) {
   1902			/*
   1903			 * aio_poll_wake() already either scheduled the async
   1904			 * completion work, or completed the request inline.
   1905			 */
   1906			if (apt.error) /* unsupported case: multiple queues */
   1907				cancel = true;
   1908			apt.error = 0;
   1909			mask = 0;
   1910		}
   1911		if (mask || apt.error) {
   1912			/* Steal to complete synchronously. */
   1913			list_del_init(&req->wait.entry);
   1914		} else if (cancel) {
   1915			/* Cancel if possible (may be too late though). */
   1916			WRITE_ONCE(req->cancelled, true);
   1917		} else if (on_queue) {
   1918			/*
   1919			 * Actually waiting for an event, so add the request to
   1920			 * active_reqs so that it can be cancelled if needed.
   1921			 */
   1922			list_add_tail(&aiocb->ki_list, &ctx->active_reqs);
   1923			aiocb->ki_cancel = aio_poll_cancel;
   1924		}
   1925		if (on_queue)
   1926			poll_iocb_unlock_wq(req);
   1927	}
   1928	if (mask) { /* no async, we'd stolen it */
   1929		aiocb->ki_res.res = mangle_poll(mask);
   1930		apt.error = 0;
   1931	}
   1932	spin_unlock_irq(&ctx->ctx_lock);
   1933	if (mask)
   1934		iocb_put(aiocb);
   1935	return apt.error;
   1936}
   1937
   1938static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb,
   1939			   struct iocb __user *user_iocb, struct aio_kiocb *req,
   1940			   bool compat)
   1941{
   1942	req->ki_filp = fget(iocb->aio_fildes);
   1943	if (unlikely(!req->ki_filp))
   1944		return -EBADF;
   1945
   1946	if (iocb->aio_flags & IOCB_FLAG_RESFD) {
   1947		struct eventfd_ctx *eventfd;
   1948		/*
   1949		 * If the IOCB_FLAG_RESFD flag of aio_flags is set, get an
   1950		 * instance of the file* now. The file descriptor must be
   1951		 * an eventfd() fd, and will be signaled for each completed
   1952		 * event using the eventfd_signal() function.
   1953		 */
   1954		eventfd = eventfd_ctx_fdget(iocb->aio_resfd);
   1955		if (IS_ERR(eventfd))
   1956			return PTR_ERR(eventfd);
   1957
   1958		req->ki_eventfd = eventfd;
   1959	}
   1960
   1961	if (unlikely(put_user(KIOCB_KEY, &user_iocb->aio_key))) {
   1962		pr_debug("EFAULT: aio_key\n");
   1963		return -EFAULT;
   1964	}
   1965
   1966	req->ki_res.obj = (u64)(unsigned long)user_iocb;
   1967	req->ki_res.data = iocb->aio_data;
   1968	req->ki_res.res = 0;
   1969	req->ki_res.res2 = 0;
   1970
   1971	switch (iocb->aio_lio_opcode) {
   1972	case IOCB_CMD_PREAD:
   1973		return aio_read(&req->rw, iocb, false, compat);
   1974	case IOCB_CMD_PWRITE:
   1975		return aio_write(&req->rw, iocb, false, compat);
   1976	case IOCB_CMD_PREADV:
   1977		return aio_read(&req->rw, iocb, true, compat);
   1978	case IOCB_CMD_PWRITEV:
   1979		return aio_write(&req->rw, iocb, true, compat);
   1980	case IOCB_CMD_FSYNC:
   1981		return aio_fsync(&req->fsync, iocb, false);
   1982	case IOCB_CMD_FDSYNC:
   1983		return aio_fsync(&req->fsync, iocb, true);
   1984	case IOCB_CMD_POLL:
   1985		return aio_poll(req, iocb);
   1986	default:
   1987		pr_debug("invalid aio operation %d\n", iocb->aio_lio_opcode);
   1988		return -EINVAL;
   1989	}
   1990}
   1991
   1992static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
   1993			 bool compat)
   1994{
   1995	struct aio_kiocb *req;
   1996	struct iocb iocb;
   1997	int err;
   1998
   1999	if (unlikely(copy_from_user(&iocb, user_iocb, sizeof(iocb))))
   2000		return -EFAULT;
   2001
   2002	/* enforce forwards compatibility on users */
   2003	if (unlikely(iocb.aio_reserved2)) {
   2004		pr_debug("EINVAL: reserve field set\n");
   2005		return -EINVAL;
   2006	}
   2007
   2008	/* prevent overflows */
   2009	if (unlikely(
   2010	    (iocb.aio_buf != (unsigned long)iocb.aio_buf) ||
   2011	    (iocb.aio_nbytes != (size_t)iocb.aio_nbytes) ||
   2012	    ((ssize_t)iocb.aio_nbytes < 0)
   2013	   )) {
   2014		pr_debug("EINVAL: overflow check\n");
   2015		return -EINVAL;
   2016	}
   2017
   2018	req = aio_get_req(ctx);
   2019	if (unlikely(!req))
   2020		return -EAGAIN;
   2021
   2022	err = __io_submit_one(ctx, &iocb, user_iocb, req, compat);
   2023
   2024	/* Done with the synchronous reference */
   2025	iocb_put(req);
   2026
   2027	/*
   2028	 * If err is 0, we'd either done aio_complete() ourselves or have
   2029	 * arranged for that to be done asynchronously.  Anything non-zero
   2030	 * means that we need to destroy req ourselves.
   2031	 */
   2032	if (unlikely(err)) {
   2033		iocb_destroy(req);
   2034		put_reqs_available(ctx, 1);
   2035	}
   2036	return err;
   2037}
   2038
   2039/* sys_io_submit:
   2040 *	Queue the nr iocbs pointed to by iocbpp for processing.  Returns
   2041 *	the number of iocbs queued.  May return -EINVAL if the aio_context
   2042 *	specified by ctx_id is invalid, if nr is < 0, if the iocb at
   2043 *	*iocbpp[0] is not properly initialized, if the operation specified
   2044 *	is invalid for the file descriptor in the iocb.  May fail with
   2045 *	-EFAULT if any of the data structures point to invalid data.  May
   2046 *	fail with -EBADF if the file descriptor specified in the first
   2047 *	iocb is invalid.  May fail with -EAGAIN if insufficient resources
   2048 *	are available to queue any iocbs.  Will return 0 if nr is 0.  Will
   2049 *	fail with -ENOSYS if not implemented.
   2050 */
   2051SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
   2052		struct iocb __user * __user *, iocbpp)
   2053{
   2054	struct kioctx *ctx;
   2055	long ret = 0;
   2056	int i = 0;
   2057	struct blk_plug plug;
   2058
   2059	if (unlikely(nr < 0))
   2060		return -EINVAL;
   2061
   2062	ctx = lookup_ioctx(ctx_id);
   2063	if (unlikely(!ctx)) {
   2064		pr_debug("EINVAL: invalid context id\n");
   2065		return -EINVAL;
   2066	}
   2067
   2068	if (nr > ctx->nr_events)
   2069		nr = ctx->nr_events;
   2070
   2071	if (nr > AIO_PLUG_THRESHOLD)
   2072		blk_start_plug(&plug);
   2073	for (i = 0; i < nr; i++) {
   2074		struct iocb __user *user_iocb;
   2075
   2076		if (unlikely(get_user(user_iocb, iocbpp + i))) {
   2077			ret = -EFAULT;
   2078			break;
   2079		}
   2080
   2081		ret = io_submit_one(ctx, user_iocb, false);
   2082		if (ret)
   2083			break;
   2084	}
   2085	if (nr > AIO_PLUG_THRESHOLD)
   2086		blk_finish_plug(&plug);
   2087
   2088	percpu_ref_put(&ctx->users);
   2089	return i ? i : ret;
   2090}
   2091
   2092#ifdef CONFIG_COMPAT
   2093COMPAT_SYSCALL_DEFINE3(io_submit, compat_aio_context_t, ctx_id,
   2094		       int, nr, compat_uptr_t __user *, iocbpp)
   2095{
   2096	struct kioctx *ctx;
   2097	long ret = 0;
   2098	int i = 0;
   2099	struct blk_plug plug;
   2100
   2101	if (unlikely(nr < 0))
   2102		return -EINVAL;
   2103
   2104	ctx = lookup_ioctx(ctx_id);
   2105	if (unlikely(!ctx)) {
   2106		pr_debug("EINVAL: invalid context id\n");
   2107		return -EINVAL;
   2108	}
   2109
   2110	if (nr > ctx->nr_events)
   2111		nr = ctx->nr_events;
   2112
   2113	if (nr > AIO_PLUG_THRESHOLD)
   2114		blk_start_plug(&plug);
   2115	for (i = 0; i < nr; i++) {
   2116		compat_uptr_t user_iocb;
   2117
   2118		if (unlikely(get_user(user_iocb, iocbpp + i))) {
   2119			ret = -EFAULT;
   2120			break;
   2121		}
   2122
   2123		ret = io_submit_one(ctx, compat_ptr(user_iocb), true);
   2124		if (ret)
   2125			break;
   2126	}
   2127	if (nr > AIO_PLUG_THRESHOLD)
   2128		blk_finish_plug(&plug);
   2129
   2130	percpu_ref_put(&ctx->users);
   2131	return i ? i : ret;
   2132}
   2133#endif
   2134
   2135/* sys_io_cancel:
   2136 *	Attempts to cancel an iocb previously passed to io_submit.  If
   2137 *	the operation is successfully cancelled, the resulting event is
   2138 *	copied into the memory pointed to by result without being placed
   2139 *	into the completion queue and 0 is returned.  May fail with
   2140 *	-EFAULT if any of the data structures pointed to are invalid.
   2141 *	May fail with -EINVAL if aio_context specified by ctx_id is
   2142 *	invalid.  May fail with -EAGAIN if the iocb specified was not
   2143 *	cancelled.  Will fail with -ENOSYS if not implemented.
   2144 */
   2145SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
   2146		struct io_event __user *, result)
   2147{
   2148	struct kioctx *ctx;
   2149	struct aio_kiocb *kiocb;
   2150	int ret = -EINVAL;
   2151	u32 key;
   2152	u64 obj = (u64)(unsigned long)iocb;
   2153
   2154	if (unlikely(get_user(key, &iocb->aio_key)))
   2155		return -EFAULT;
   2156	if (unlikely(key != KIOCB_KEY))
   2157		return -EINVAL;
   2158
   2159	ctx = lookup_ioctx(ctx_id);
   2160	if (unlikely(!ctx))
   2161		return -EINVAL;
   2162
   2163	spin_lock_irq(&ctx->ctx_lock);
   2164	/* TODO: use a hash or array, this sucks. */
   2165	list_for_each_entry(kiocb, &ctx->active_reqs, ki_list) {
   2166		if (kiocb->ki_res.obj == obj) {
   2167			ret = kiocb->ki_cancel(&kiocb->rw);
   2168			list_del_init(&kiocb->ki_list);
   2169			break;
   2170		}
   2171	}
   2172	spin_unlock_irq(&ctx->ctx_lock);
   2173
   2174	if (!ret) {
   2175		/*
   2176		 * The result argument is no longer used - the io_event is
   2177		 * always delivered via the ring buffer. -EINPROGRESS indicates
   2178		 * cancellation is progress:
   2179		 */
   2180		ret = -EINPROGRESS;
   2181	}
   2182
   2183	percpu_ref_put(&ctx->users);
   2184
   2185	return ret;
   2186}
   2187
   2188static long do_io_getevents(aio_context_t ctx_id,
   2189		long min_nr,
   2190		long nr,
   2191		struct io_event __user *events,
   2192		struct timespec64 *ts)
   2193{
   2194	ktime_t until = ts ? timespec64_to_ktime(*ts) : KTIME_MAX;
   2195	struct kioctx *ioctx = lookup_ioctx(ctx_id);
   2196	long ret = -EINVAL;
   2197
   2198	if (likely(ioctx)) {
   2199		if (likely(min_nr <= nr && min_nr >= 0))
   2200			ret = read_events(ioctx, min_nr, nr, events, until);
   2201		percpu_ref_put(&ioctx->users);
   2202	}
   2203
   2204	return ret;
   2205}
   2206
   2207/* io_getevents:
   2208 *	Attempts to read at least min_nr events and up to nr events from
   2209 *	the completion queue for the aio_context specified by ctx_id. If
   2210 *	it succeeds, the number of read events is returned. May fail with
   2211 *	-EINVAL if ctx_id is invalid, if min_nr is out of range, if nr is
   2212 *	out of range, if timeout is out of range.  May fail with -EFAULT
   2213 *	if any of the memory specified is invalid.  May return 0 or
   2214 *	< min_nr if the timeout specified by timeout has elapsed
   2215 *	before sufficient events are available, where timeout == NULL
   2216 *	specifies an infinite timeout. Note that the timeout pointed to by
   2217 *	timeout is relative.  Will fail with -ENOSYS if not implemented.
   2218 */
   2219#ifdef CONFIG_64BIT
   2220
   2221SYSCALL_DEFINE5(io_getevents, aio_context_t, ctx_id,
   2222		long, min_nr,
   2223		long, nr,
   2224		struct io_event __user *, events,
   2225		struct __kernel_timespec __user *, timeout)
   2226{
   2227	struct timespec64	ts;
   2228	int			ret;
   2229
   2230	if (timeout && unlikely(get_timespec64(&ts, timeout)))
   2231		return -EFAULT;
   2232
   2233	ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);
   2234	if (!ret && signal_pending(current))
   2235		ret = -EINTR;
   2236	return ret;
   2237}
   2238
   2239#endif
   2240
   2241struct __aio_sigset {
   2242	const sigset_t __user	*sigmask;
   2243	size_t		sigsetsize;
   2244};
   2245
   2246SYSCALL_DEFINE6(io_pgetevents,
   2247		aio_context_t, ctx_id,
   2248		long, min_nr,
   2249		long, nr,
   2250		struct io_event __user *, events,
   2251		struct __kernel_timespec __user *, timeout,
   2252		const struct __aio_sigset __user *, usig)
   2253{
   2254	struct __aio_sigset	ksig = { NULL, };
   2255	struct timespec64	ts;
   2256	bool interrupted;
   2257	int ret;
   2258
   2259	if (timeout && unlikely(get_timespec64(&ts, timeout)))
   2260		return -EFAULT;
   2261
   2262	if (usig && copy_from_user(&ksig, usig, sizeof(ksig)))
   2263		return -EFAULT;
   2264
   2265	ret = set_user_sigmask(ksig.sigmask, ksig.sigsetsize);
   2266	if (ret)
   2267		return ret;
   2268
   2269	ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);
   2270
   2271	interrupted = signal_pending(current);
   2272	restore_saved_sigmask_unless(interrupted);
   2273	if (interrupted && !ret)
   2274		ret = -ERESTARTNOHAND;
   2275
   2276	return ret;
   2277}
   2278
   2279#if defined(CONFIG_COMPAT_32BIT_TIME) && !defined(CONFIG_64BIT)
   2280
   2281SYSCALL_DEFINE6(io_pgetevents_time32,
   2282		aio_context_t, ctx_id,
   2283		long, min_nr,
   2284		long, nr,
   2285		struct io_event __user *, events,
   2286		struct old_timespec32 __user *, timeout,
   2287		const struct __aio_sigset __user *, usig)
   2288{
   2289	struct __aio_sigset	ksig = { NULL, };
   2290	struct timespec64	ts;
   2291	bool interrupted;
   2292	int ret;
   2293
   2294	if (timeout && unlikely(get_old_timespec32(&ts, timeout)))
   2295		return -EFAULT;
   2296
   2297	if (usig && copy_from_user(&ksig, usig, sizeof(ksig)))
   2298		return -EFAULT;
   2299
   2300
   2301	ret = set_user_sigmask(ksig.sigmask, ksig.sigsetsize);
   2302	if (ret)
   2303		return ret;
   2304
   2305	ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);
   2306
   2307	interrupted = signal_pending(current);
   2308	restore_saved_sigmask_unless(interrupted);
   2309	if (interrupted && !ret)
   2310		ret = -ERESTARTNOHAND;
   2311
   2312	return ret;
   2313}
   2314
   2315#endif
   2316
   2317#if defined(CONFIG_COMPAT_32BIT_TIME)
   2318
   2319SYSCALL_DEFINE5(io_getevents_time32, __u32, ctx_id,
   2320		__s32, min_nr,
   2321		__s32, nr,
   2322		struct io_event __user *, events,
   2323		struct old_timespec32 __user *, timeout)
   2324{
   2325	struct timespec64 t;
   2326	int ret;
   2327
   2328	if (timeout && get_old_timespec32(&t, timeout))
   2329		return -EFAULT;
   2330
   2331	ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);
   2332	if (!ret && signal_pending(current))
   2333		ret = -EINTR;
   2334	return ret;
   2335}
   2336
   2337#endif
   2338
   2339#ifdef CONFIG_COMPAT
   2340
   2341struct __compat_aio_sigset {
   2342	compat_uptr_t		sigmask;
   2343	compat_size_t		sigsetsize;
   2344};
   2345
   2346#if defined(CONFIG_COMPAT_32BIT_TIME)
   2347
   2348COMPAT_SYSCALL_DEFINE6(io_pgetevents,
   2349		compat_aio_context_t, ctx_id,
   2350		compat_long_t, min_nr,
   2351		compat_long_t, nr,
   2352		struct io_event __user *, events,
   2353		struct old_timespec32 __user *, timeout,
   2354		const struct __compat_aio_sigset __user *, usig)
   2355{
   2356	struct __compat_aio_sigset ksig = { 0, };
   2357	struct timespec64 t;
   2358	bool interrupted;
   2359	int ret;
   2360
   2361	if (timeout && get_old_timespec32(&t, timeout))
   2362		return -EFAULT;
   2363
   2364	if (usig && copy_from_user(&ksig, usig, sizeof(ksig)))
   2365		return -EFAULT;
   2366
   2367	ret = set_compat_user_sigmask(compat_ptr(ksig.sigmask), ksig.sigsetsize);
   2368	if (ret)
   2369		return ret;
   2370
   2371	ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);
   2372
   2373	interrupted = signal_pending(current);
   2374	restore_saved_sigmask_unless(interrupted);
   2375	if (interrupted && !ret)
   2376		ret = -ERESTARTNOHAND;
   2377
   2378	return ret;
   2379}
   2380
   2381#endif
   2382
   2383COMPAT_SYSCALL_DEFINE6(io_pgetevents_time64,
   2384		compat_aio_context_t, ctx_id,
   2385		compat_long_t, min_nr,
   2386		compat_long_t, nr,
   2387		struct io_event __user *, events,
   2388		struct __kernel_timespec __user *, timeout,
   2389		const struct __compat_aio_sigset __user *, usig)
   2390{
   2391	struct __compat_aio_sigset ksig = { 0, };
   2392	struct timespec64 t;
   2393	bool interrupted;
   2394	int ret;
   2395
   2396	if (timeout && get_timespec64(&t, timeout))
   2397		return -EFAULT;
   2398
   2399	if (usig && copy_from_user(&ksig, usig, sizeof(ksig)))
   2400		return -EFAULT;
   2401
   2402	ret = set_compat_user_sigmask(compat_ptr(ksig.sigmask), ksig.sigsetsize);
   2403	if (ret)
   2404		return ret;
   2405
   2406	ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);
   2407
   2408	interrupted = signal_pending(current);
   2409	restore_saved_sigmask_unless(interrupted);
   2410	if (interrupted && !ret)
   2411		ret = -ERESTARTNOHAND;
   2412
   2413	return ret;
   2414}
   2415#endif