Release 4.7 fs/aio.c
/*
* An async IO implementation for Linux
* Written by Benjamin LaHaise <bcrl@kvack.org>
*
* Implements an efficient asynchronous io interface.
*
* Copyright 2000, 2001, 2002 Red Hat, Inc. All Rights Reserved.
*
* See ../COPYING for licensing terms.
*/
#define pr_fmt(fmt) "%s: " fmt, __func__
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/time.h>
#include <linux/aio_abi.h>
#include <linux/export.h>
#include <linux/syscalls.h>
#include <linux/backing-dev.h>
#include <linux/uio.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/mmu_context.h>
#include <linux/percpu.h>
#include <linux/slab.h>
#include <linux/timer.h>
#include <linux/aio.h>
#include <linux/highmem.h>
#include <linux/workqueue.h>
#include <linux/security.h>
#include <linux/eventfd.h>
#include <linux/blkdev.h>
#include <linux/compat.h>
#include <linux/migrate.h>
#include <linux/ramfs.h>
#include <linux/percpu-refcount.h>
#include <linux/mount.h>
#include <asm/kmap_types.h>
#include <asm/uaccess.h>
#include "internal.h"
#define AIO_RING_MAGIC 0xa10a10a1
#define AIO_RING_COMPAT_FEATURES 1
#define AIO_RING_INCOMPAT_FEATURES 0
struct aio_ring {
unsigned id; /* kernel internal index number */
unsigned nr; /* number of io_events */
unsigned head; /* Written to by userland or under ring_lock
* mutex by aio_read_events_ring(). */
unsigned tail;
unsigned magic;
unsigned compat_features;
unsigned incompat_features;
unsigned header_length; /* size of aio_ring */
struct io_event io_events[0];
}; /* 128 bytes + ring size */
#define AIO_RING_PAGES 8
struct kioctx_table {
struct rcu_head rcu;
unsigned nr;
struct kioctx *table[];
};
struct kioctx_cpu {
unsigned reqs_available;
};
struct ctx_rq_wait {
struct completion comp;
atomic_t count;
};
struct kioctx {
struct percpu_ref users;
atomic_t dead;
struct percpu_ref reqs;
unsigned long user_id;
struct __percpu kioctx_cpu *cpu;
/*
* For percpu reqs_available, number of slots we move to/from global
* counter at a time:
*/
unsigned req_batch;
/*
* This is what userspace passed to io_setup(), it's not used for
* anything but counting against the global max_reqs quota.
*
* The real limit is nr_events - 1, which will be larger (see
* aio_setup_ring())
*/
unsigned max_reqs;
/* Size of ringbuffer, in units of struct io_event */
unsigned nr_events;
unsigned long mmap_base;
unsigned long mmap_size;
struct page **ring_pages;
long nr_pages;
struct work_struct free_work;
/*
* signals when all in-flight requests are done
*/
struct ctx_rq_wait *rq_wait;
struct {
/*
* This counts the number of available slots in the ringbuffer,
* so we avoid overflowing it: it's decremented (if positive)
* when allocating a kiocb and incremented when the resulting
* io_event is pulled off the ringbuffer.
*
* We batch accesses to it with a percpu version.
*/
atomic_t reqs_available;
}
____cacheline_aligned_in_smp;
struct {
spinlock_t ctx_lock;
struct list_head active_reqs; /* used for cancellation */
}
____cacheline_aligned_in_smp;
struct {
struct mutex ring_lock;
wait_queue_head_t wait;
}
____cacheline_aligned_in_smp;
struct {
unsigned tail;
unsigned completed_events;
spinlock_t completion_lock;
}
____cacheline_aligned_in_smp;
struct page *internal_pages[AIO_RING_PAGES];
struct file *aio_ring_file;
unsigned id;
};
/*
* We use ki_cancel == KIOCB_CANCELLED to indicate that a kiocb has been either
* cancelled or completed (this makes a certain amount of sense because
* successful cancellation - io_cancel() - does deliver the completion to
* userspace).
*
* And since most things don't implement kiocb cancellation and we'd really like
* kiocb completion to be lockless when possible, we use ki_cancel to
* synchronize cancellation and completion - we only set it to KIOCB_CANCELLED
* with xchg() or cmpxchg(), see batch_complete_aio() and kiocb_cancel().
*/
#define KIOCB_CANCELLED ((void *) (~0ULL))
struct aio_kiocb {
struct kiocb common;
struct kioctx *ki_ctx;
kiocb_cancel_fn *ki_cancel;
struct iocb __user *ki_user_iocb; /* user's aiocb */
__u64 ki_user_data; /* user's data for completion */
struct list_head ki_list; /* the aio core uses this
* for cancellation */
/*
* If the aio_resfd field of the userspace iocb is not zero,
* this is the underlying eventfd context to deliver events to.
*/
struct eventfd_ctx *ki_eventfd;
};
/*------ sysctl variables----*/
static DEFINE_SPINLOCK(aio_nr_lock);
unsigned long aio_nr;
/* current system wide number of aio requests */
unsigned long aio_max_nr = 0x10000;
/* system wide maximum number of aio requests */
/*----end sysctl variables---*/
static struct kmem_cache *kiocb_cachep;
static struct kmem_cache *kioctx_cachep;
static struct vfsmount *aio_mnt;
static const struct file_operations aio_ring_fops;
static const struct address_space_operations aio_ctx_aops;
static struct file *aio_private_file(struct kioctx *ctx, loff_t nr_pages)
{
struct qstr this = QSTR_INIT("[aio]", 5);
struct file *file;
struct path path;
struct inode *inode = alloc_anon_inode(aio_mnt->mnt_sb);
if (IS_ERR(inode))
return ERR_CAST(inode);
inode->i_mapping->a_ops = &aio_ctx_aops;
inode->i_mapping->private_data = ctx;
inode->i_size = PAGE_SIZE * nr_pages;
path.dentry = d_alloc_pseudo(aio_mnt->mnt_sb, &this);
if (!path.dentry) {
iput(inode);
return ERR_PTR(-ENOMEM);
}
path.mnt = mntget(aio_mnt);
d_instantiate(path.dentry, inode);
file = alloc_file(&path, FMODE_READ | FMODE_WRITE, &aio_ring_fops);
if (IS_ERR(file)) {
path_put(&path);
return file;
}
file->f_flags = O_RDWR;
return file;
}
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| Total | 181 | 100.00% | 2 | 100.00% |
static struct dentry *aio_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
{
static const struct dentry_operations ops = {
.d_dname = simple_dname,
};
return mount_pseudo(fs_type, "aio:", NULL, &ops, AIO_RING_MAGIC);
}
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| Total | 53 | 100.00% | 2 | 100.00% |
/* aio_setup
* Creates the slab caches used by the aio routines, panic on
* failure as this is done early during the boot sequence.
*/
static int __init aio_setup(void)
{
static struct file_system_type aio_fs = {
.name = "aio",
.mount = aio_mount,
.kill_sb = kill_anon_super,
};
aio_mnt = kern_mount(&aio_fs);
if (IS_ERR(aio_mnt))
panic("Failed to create aio fs mount.");
kiocb_cachep = KMEM_CACHE(aio_kiocb, SLAB_HWCACHE_ALIGN|SLAB_PANIC);
kioctx_cachep = KMEM_CACHE(kioctx,SLAB_HWCACHE_ALIGN|SLAB_PANIC);
pr_debug("sizeof(struct page) = %zu\n", sizeof(struct page));
return 0;
}
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benjamin lahaise | benjamin lahaise | 78 | 89.66% | 2 | 28.57% |
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christoph lameter | christoph lameter | 2 | 2.30% | 1 | 14.29% |
kent overstreet | kent overstreet | 1 | 1.15% | 1 | 14.29% |
christoph hellwig | christoph hellwig | 1 | 1.15% | 1 | 14.29% |
stephen hemminger | stephen hemminger | 1 | 1.15% | 1 | 14.29% |
| Total | 87 | 100.00% | 7 | 100.00% |
__initcall(aio_setup);
static void put_aio_ring_file(struct kioctx *ctx)
{
struct file *aio_ring_file = ctx->aio_ring_file;
if (aio_ring_file) {
truncate_setsize(aio_ring_file->f_inode, 0);
/* Prevent further access to the kioctx from migratepages */
spin_lock(&aio_ring_file->f_inode->i_mapping->private_lock);
aio_ring_file->f_inode->i_mapping->private_data = NULL;
ctx->aio_ring_file = NULL;
spin_unlock(&aio_ring_file->f_inode->i_mapping->private_lock);
fput(aio_ring_file);
}
}
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benjamin lahaise | benjamin lahaise | 72 | 88.89% | 2 | 66.67% |
gu zheng | gu zheng | 9 | 11.11% | 1 | 33.33% |
| Total | 81 | 100.00% | 3 | 100.00% |
static void aio_free_ring(struct kioctx *ctx)
{
int i;
/* Disconnect the kiotx from the ring file. This prevents future
* accesses to the kioctx from page migration.
*/
put_aio_ring_file(ctx);
for (i = 0; i < ctx->nr_pages; i++) {
struct page *page;
pr_debug("pid(%d) [%d] page->count=%d\n", current->pid, i,
page_count(ctx->ring_pages[i]));
page = ctx->ring_pages[i];
if (!page)
continue;
ctx->ring_pages[i] = NULL;
put_page(page);
}
if (ctx->ring_pages && ctx->ring_pages != ctx->internal_pages) {
kfree(ctx->ring_pages);
ctx->ring_pages = NULL;
}
}
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kent overstreet | kent overstreet | 6 | 4.96% | 1 | 14.29% |
| Total | 121 | 100.00% | 7 | 100.00% |
static int aio_ring_mremap(struct vm_area_struct *vma)
{
struct file *file = vma->vm_file;
struct mm_struct *mm = vma->vm_mm;
struct kioctx_table *table;
int i, res = -EINVAL;
spin_lock(&mm->ioctx_lock);
rcu_read_lock();
table = rcu_dereference(mm->ioctx_table);
for (i = 0; i < table->nr; i++) {
struct kioctx *ctx;
ctx = table->table[i];
if (ctx && ctx->aio_ring_file == file) {
if (!atomic_read(&ctx->dead)) {
ctx->user_id = ctx->mmap_base = vma->vm_start;
res = 0;
}
break;
}
}
rcu_read_unlock();
spin_unlock(&mm->ioctx_lock);
return res;
}
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oleg nesterov | oleg nesterov | 5 | 3.36% | 1 | 25.00% |
| Total | 149 | 100.00% | 4 | 100.00% |
static const struct vm_operations_struct aio_ring_vm_ops = {
.mremap = aio_ring_mremap,
#if IS_ENABLED(CONFIG_MMU)
.fault = filemap_fault,
.map_pages = filemap_map_pages,
.page_mkwrite = filemap_page_mkwrite,
#endif
};
static int aio_ring_mmap(struct file *file, struct vm_area_struct *vma)
{
vma->vm_flags |= VM_DONTEXPAND;
vma->vm_ops = &aio_ring_vm_ops;
return 0;
}
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static const struct file_operations aio_ring_fops = {
.mmap = aio_ring_mmap,
};
#if IS_ENABLED(CONFIG_MIGRATION)
static int aio_migratepage(struct address_space *mapping, struct page *new,
struct page *old, enum migrate_mode mode)
{
struct kioctx *ctx;
unsigned long flags;
pgoff_t idx;
int rc;
rc = 0;
/* mapping->private_lock here protects against the kioctx teardown. */
spin_lock(&mapping->private_lock);
ctx = mapping->private_data;
if (!ctx) {
rc = -EINVAL;
goto out;
}
/* The ring_lock mutex. The prevents aio_read_events() from writing
* to the ring's head, and prevents page migration from mucking in
* a partially initialized kiotx.
*/
if (!mutex_trylock(&ctx->ring_lock)) {
rc = -EAGAIN;
goto out;
}
idx = old->index;
if (idx < (pgoff_t)ctx->nr_pages) {
/* Make sure the old page hasn't already been changed */
if (ctx->ring_pages[idx] != old)
rc = -EAGAIN;
} else
rc = -EINVAL;
if (rc != 0)
goto out_unlock;
/* Writeback must be complete */
BUG_ON(PageWriteback(old));
get_page(new);
rc = migrate_page_move_mapping(mapping, new, old, NULL, mode, 1);
if (rc != MIGRATEPAGE_SUCCESS) {
put_page(new);
goto out_unlock;
}
/* Take completion_lock to prevent other writes to the ring buffer
* while the old page is copied to the new. This prevents new
* events from being lost.
*/
spin_lock_irqsave(&ctx->completion_lock, flags);
migrate_page_copy(new, old);
BUG_ON(ctx->ring_pages[idx] != old);
ctx->ring_pages[idx] = new;
spin_unlock_irqrestore(&ctx->completion_lock, flags);
/* The old page is no longer accessible. */
put_page(old);
out_unlock:
mutex_unlock(&ctx->ring_lock);
out:
spin_unlock(&mapping->private_lock);
return rc;
}
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#endif
static const struct address_space_operations aio_ctx_aops = {
.set_page_dirty = __set_page_dirty_no_writeback,
#if IS_ENABLED(CONFIG_MIGRATION)
.migratepage = aio_migratepage,
#endif
};
static int aio_setup_ring(struct kioctx *ctx)
{
struct aio_ring *ring;
unsigned nr_events = ctx->max_reqs;
struct mm_struct *mm = current->mm;
unsigned long size, unused;
int nr_pages;
int i;
struct file *file;
/* Compensate for the ring buffer's head/tail overlap entry */
nr_events += 2; /* 1 is required, 2 for good luck */
size = sizeof(struct aio_ring);
size += sizeof(struct io_event) * nr_events;
nr_pages = PFN_UP(size);
if (nr_pages < 0)
return -EINVAL;
file = aio_private_file(ctx, nr_pages);
if (IS_ERR(file)) {
ctx->aio_ring_file = NULL;
return -ENOMEM;
}
ctx->aio_ring_file = file;
nr_events = (PAGE_SIZE * nr_pages - sizeof(struct aio_ring))
/ sizeof(struct io_event);
ctx->ring_pages = ctx->internal_pages;
if (nr_pages > AIO_RING_PAGES) {
ctx->ring_pages = kcalloc(nr_pages, sizeof(struct page *),
GFP_KERNEL);
if (!ctx->ring_pages) {
put_aio_ring_file(ctx);
return -ENOMEM;
}
}
for (i = 0; i < nr_pages; i++) {
struct page *page;
page = find_or_create_page(file->f_inode->i_mapping,
i, GFP_HIGHUSER | __GFP_ZERO);
if (!page)
break;
pr_debug("pid(%d) page[%d]->count=%d\n",
current->pid, i, page_count(page));
SetPageUptodate(page);
unlock_page(page);
ctx->ring_pages[i] = page;
}
ctx->nr_pages = i;
if (unlikely(i != nr_pages)) {
aio_free_ring(ctx);
return -ENOMEM;
}
ctx->mmap_size = nr_pages * PAGE_SIZE;
pr_debug("attempting mmap of %lu bytes\n", ctx->mmap_size);
if (down_write_killable(&mm->mmap_sem)) {
ctx->mmap_size = 0;
aio_free_ring(ctx);
return -EINTR;
}
ctx->mmap_base = do_mmap_pgoff(ctx->aio_ring_file, 0, ctx->mmap_size,
PROT_READ | PROT_WRITE,
MAP_SHARED, 0, &unused);
up_write(&mm->mmap_sem);
if (IS_ERR((void *)ctx->mmap_base)) {
ctx->mmap_size = 0;
aio_free_ring(ctx);
return -ENOMEM;
}
pr_debug("mmap address: 0x%08lx\n", ctx->mmap_base);
ctx->user_id = ctx->mmap_base;
ctx->nr_events = nr_events; /* trusted copy */
ring = kmap_atomic(ctx->ring_pages[0]);
ring->nr = nr_events; /* user copy */
ring->id = ~0U;
ring->head = ring->tail = 0;
ring->magic = AIO_RING_MAGIC;
ring->compat_features = AIO_RING_COMPAT_FEATURES;
ring->incompat_features = AIO_RING_INCOMPAT_FEATURES;
ring->header_length = sizeof(struct aio_ring);
kunmap_atomic(ring);
flush_dcache_page(ctx->ring_pages[0]);
return 0;
}
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zach brown | zach brown | 9 | 1.74% | 1 | 6.25% |
michel lespinasse | michel lespinasse | 3 | 0.58% | 2 | 12.50% |
oliver neukum | oliver neukum | 1 | 0.19% | 1 | 6.25% |
al viro | al viro | 1 | 0.19% | 1 | 6.25% |
| Total | 516 | 100.00% | 16 | 100.00% |
#define AIO_EVENTS_PER_PAGE (PAGE_SIZE / sizeof(struct io_event))
#define AIO_EVENTS_FIRST_PAGE ((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event))
#define AIO_EVENTS_OFFSET (AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE)
void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel)
{
struct aio_kiocb *req = container_of(iocb, struct aio_kiocb, common);
struct kioctx *ctx = req->ki_ctx;
unsigned long flags;
spin_lock_irqsave(&ctx->ctx_lock, flags);
if (!req->ki_list.next)
list_add(&req->ki_list, &ctx->active_reqs);
req->ki_cancel = cancel;
spin_unlock_irqrestore(&ctx->ctx_lock, flags);
}
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| Total | 90 | 100.00% | 2 | 100.00% |
EXPORT_SYMBOL(kiocb_set_cancel_fn);
static int kiocb_cancel(struct aio_kiocb *kiocb)
{
kiocb_cancel_fn *old, *cancel;
/*
* Don't want to set kiocb->ki_cancel = KIOCB_CANCELLED unless it
* actually has a cancel function, hence the cmpxchg()
*/
cancel = ACCESS_ONCE(kiocb->ki_cancel);
do {
if (!cancel || cancel == KIOCB_CANCELLED)
return -EINVAL;
old = cancel;
cancel = cmpxchg(&kiocb->ki_cancel, old, KIOCB_CANCELLED);
} while (cancel != old);
return cancel(&kiocb->common);
}
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| Total | 78 | 100.00% | 4 | 100.00% |
static void free_ioctx(struct work_struct *work)
{
struct kioctx *ctx = container_of(work, struct kioctx, free_work);
pr_debug("freeing %p\n", ctx);
aio_free_ring(ctx);
free_percpu(ctx->cpu);
percpu_ref_exit(&ctx->reqs);
percpu_ref_exit(&ctx->users);
kmem_cache_free(kioctx_cachep, ctx);
}
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jens axboe | jens axboe | 1 | 1.47% | 1 | 16.67% |
| Total | 68 | 100.00% | 6 | 100.00% |
static void free_ioctx_reqs(struct percpu_ref *ref)
{
struct kioctx *ctx = container_of(ref, struct kioctx, reqs);
/* At this point we know that there are no any in-flight requests */
if (ctx->rq_wait && atomic_dec_and_test(&ctx->rq_wait->count))
complete(&ctx->rq_wait->comp);
INIT_WORK(&ctx->free_work, free_ioctx);
schedule_work(&ctx->free_work);
}
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| Total | 71 | 100.00% | 5 | 100.00% |
/*
* When this function runs, the kioctx has been removed from the "hash table"
* and ctx->users has dropped to 0, so we know no more kiocbs can be submitted -
* now it's safe to cancel any that need to be.
*/
static void free_ioctx_users(struct percpu_ref *ref)
{
struct kioctx *ctx = container_of(ref, struct kioctx, users);
struct aio_kiocb *req;
spin_lock_irq(&ctx->ctx_lock);
while (!list_empty(&ctx->active_reqs)) {
req = list_first_entry(&ctx->active_reqs,
struct aio_kiocb, ki_list);
list_del_init(&req->ki_list);
kiocb_cancel(req);
}
spin_unlock_irq(&ctx->ctx_lock);
percpu_ref_kill(&ctx->reqs);
percpu_ref_put(&ctx->reqs);
}
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| Total | 104 | 100.00% | 6 | 100.00% |
static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
{
unsigned i, new_nr;
struct kioctx_table *table, *old;
struct aio_ring *ring;
spin_lock(&mm->ioctx_lock);
table = rcu_dereference_raw(mm->ioctx_table);
while (1) {
if (table)
for (i = 0; i < table->nr; i++)
if (!table->table[i]) {
ctx->id = i;
table->table[i] = ctx;
spin_unlock(&mm->ioctx_lock);
/* While kioctx setup is in progress,
* we are protected from page migration
* changes ring_pages by ->ring_lock.
*/
ring = kmap_atomic(ctx->ring_pages[0]);
ring->id = ctx->id;
kunmap_atomic(ring);
return 0;
}
new_nr = (table ? table->nr : 1) * 4;
spin_unlock(&mm->ioctx_lock);
table = kzalloc(sizeof(*table) + sizeof(struct kioctx *) *
new_nr, GFP_KERNEL);
if (!table)
return -ENOMEM;
table->nr = new_nr;
spin_lock(&mm->ioctx_lock);
old = rcu_dereference_raw(mm->ioctx_table);
if (!old) {
rcu_assign_pointer(mm->ioctx_table, table);
} else if (table->nr > old->nr) {
memcpy(table->table, old->table,
old->nr * sizeof(struct kioctx *));
rcu_assign_pointer(mm->ioctx_table, table);
kfree_rcu(old, rcu);
} else {
kfree(table);
table = old;
}
}
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
benjamin lahaise | benjamin lahaise | 285 | 96.61% | 3 | 50.00% |
kent overstreet | kent overstreet | 8 | 2.71% | 2 | 33.33% |
oleg nesterov | oleg nesterov | 2 | 0.68% | 1 | 16.67% |
| Total | 295 | 100.00% | 6 | 100.00% |
static void aio_nr_sub(unsigned nr)
{
spin_lock(&aio_nr_lock);
if (WARN_ON(aio_nr - nr > aio_nr))
aio_nr = 0;
else
aio_nr -= nr;
spin_unlock(&aio_nr_lock);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
kent overstreet | kent overstreet | 41 | 100.00% | 1 | 100.00% |
| Total | 41 | 100.00% | 1 | 100.00% |
/* ioctx_alloc
* Allocates and initializes an ioctx. Returns an ERR_PTR if it failed.
*/
static struct kioctx *ioctx_alloc(unsigned nr_events)
{
struct mm_struct *mm = current->mm;
struct kioctx *ctx;
int err = -ENOMEM;
/*
* We keep track of the number of available ringbuffer slots, to prevent
* overflow (reqs_available), and we also use percpu counters for this.
*
* So since up to half the slots might be on other cpu's percpu counters
* and unavailable, double nr_events so userspace sees what they
* expected: additionally, we move req_batch slots to/from percpu
* counters at a time, so make sure that isn't 0:
*/
nr_events = max(nr_events, num_possible_cpus() * 4);
nr_events *= 2;
/* Prevent overflows */
if (nr_events > (0x10000000U / sizeof(struct io_event))) {
pr_debug("ENOMEM: nr_events too high\n");
return ERR_PTR(-EINVAL);
}
if (!nr_events || (unsigned long)nr_events > (aio_max_nr * 2UL))
return ERR_PTR(-EAGAIN);
ctx = kmem_cache_zalloc(kioctx_cachep, GFP_KERNEL);
if (!ctx)
return ERR_PTR(-ENOMEM);
ctx->max_reqs = nr_events;
spin_lock_init(&ctx->ctx_lock);
spin_lock_init(&ctx->completion_lock);
mutex_init(&ctx->ring_lock);
/* Protect against page migration throughout kiotx setup by keeping
* the ring_lock mutex held until setup is complete. */
mutex_lock(&ctx->ring_lock);
init_waitqueue_head