/*
* An async IO implementation for Linux
* Written by Benjamin LaHaise <[email protected]>
*
* Implements an efficient asynchronous io interface.
*
* Copyright 2000, 2001, 2002 Red Hat, Inc. All Rights Reserved.
* Copyright 2018 Christoph Hellwig.
*
* 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/refcount.h>
#include <linux/uio.h>
#include <linux/sched/signal.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/mman.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 <linux/pseudo_fs.h>
#include <linux/uaccess.h>
#include <linux/nospec.h>
#include "internal.h"
#define KIOCB_KEY 0
#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[];
}; /* 128 bytes + ring size */
/*
* Plugging is meant to work with larger batches of IOs. If we don't
* have more than the below, then don't bother setting up a plug.
*/
#define AIO_PLUG_THRESHOLD 2
#define AIO_RING_PAGES 8
struct kioctx_table {
struct rcu_head rcu;
unsigned nr;
struct kioctx __rcu *table[] __counted_by(nr);
};
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 kioctx_cpu __percpu *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 folio **ring_folios;
long nr_pages;
struct rcu_work free_rwork; /* see free_ioctx() */
/*
* 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 folio *internal_folios[AIO_RING_PAGES];
struct file *aio_ring_file;
unsigned id;
};
/*
* First field must be the file pointer in all the
* iocb unions! See also 'struct kiocb' in <linux/fs.h>
*/
struct fsync_iocb {
struct file *file;
struct work_struct work;
bool datasync;
struct cred *creds;
};
struct poll_iocb {
struct file *file;
struct wait_queue_head *head;
__poll_t events;
bool cancelled;
bool work_scheduled;
bool work_need_resched;
struct wait_queue_entry wait;
struct work_struct work;
};
/*
* NOTE! Each of the iocb union members has the file pointer
* as the first entry in their struct definition. So you can
* access the file pointer through any of the sub-structs,
* or directly as just 'ki_filp' in this struct.
*/
struct aio_kiocb {
union {
struct file *ki_filp;
struct kiocb rw;
struct fsync_iocb fsync;
struct poll_iocb poll;
};
struct kioctx *ki_ctx;
kiocb_cancel_fn *ki_cancel;
struct io_event ki_res;
struct list_head ki_list; /* the aio core uses this
* for cancellation */
refcount_t ki_refcnt;
/*
* 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);
static unsigned long aio_nr; /* current system wide number of aio requests */
static unsigned long aio_max_nr = 0x10000; /* system wide maximum number of aio requests */
/*----end sysctl variables---*/
#ifdef CONFIG_SYSCTL
static struct ctl_table aio_sysctls[] = {
{
.procname = "aio-nr",
.data = &aio_nr,
.maxlen = sizeof(aio_nr),
.mode = 0444,
.proc_handler = proc_doulongvec_minmax,
},
{
.procname = "aio-max-nr",
.data = &aio_max_nr,
.maxlen = sizeof(aio_max_nr),
.mode = 0644,
.proc_handler = proc_doulongvec_minmax,
},
};
static void __init aio_sysctl_init(void)
{
register_sysctl_init("fs", aio_sysctls);
}
#else
#define aio_sysctl_init() do { } while (0)
#endif
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 file *file;
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->i_private_data = ctx;
inode->i_size = PAGE_SIZE * nr_pages;
file = alloc_file_pseudo(inode, aio_mnt, "[aio]",
O_RDWR, &aio_ring_fops);
if (IS_ERR(file))
iput(inode);
return file;
}
static int aio_init_fs_context(struct fs_context *fc)
{
if (!init_pseudo(fc, AIO_RING_MAGIC))
return -ENOMEM;
fc->s_iflags |= SB_I_NOEXEC;
return 0;
}
/* 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",
.init_fs_context = aio_init_fs_context,
.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);
aio_sysctl_init();
return 0;
}
__initcall(aio_setup);
static void put_aio_ring_file(struct kioctx *ctx)
{
struct file *aio_ring_file = ctx->aio_ring_file;
struct address_space *i_mapping;
if (aio_ring_file) {
truncate_setsize(file_inode(aio_ring_file), 0);
/* Prevent further access to the kioctx from migratepages */
i_mapping = aio_ring_file->f_mapping;
spin_lock(&i_mapping->i_private_lock);
i_mapping->i_private_data = NULL;
ctx->aio_ring_file = NULL;
spin_unlock(&i_mapping->i_private_lock);
fput(aio_ring_file);
}
}
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 folio *folio = ctx->ring_folios[i];
if (!folio)
continue;
pr_debug("pid(%d) [%d] folio->count=%d\n", current->pid, i,
folio_ref_count(folio));
ctx->ring_folios[i] = NULL;
folio_put(folio);
}
if (ctx->ring_folios && ctx->ring_folios != ctx->internal_folios) {
kfree(ctx->ring_folios);
ctx->ring_folios = NULL;
}
}
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);
if (!table)
goto out_unlock;
for (i = 0; i < table->nr; i++) {
struct kioctx *ctx;
ctx = rcu_dereference(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;
}
}
out_unlock:
rcu_read_unlock();
spin_unlock(&mm->ioctx_lock);
return res;
}
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)
{
vm_flags_set(vma, VM_DONTEXPAND);
vma->vm_ops = &aio_ring_vm_ops;
return 0;
}
static const struct file_operations aio_ring_fops = {
.mmap = aio_ring_mmap,
};
#if IS_ENABLED(CONFIG_MIGRATION)
static int aio_migrate_folio(struct address_space *mapping, struct folio *dst,
struct folio *src, enum migrate_mode mode)
{
struct kioctx *ctx;
unsigned long flags;
pgoff_t idx;
int rc = 0;
/* mapping->i_private_lock here protects against the kioctx teardown. */
spin_lock(&mapping->i_private_lock);
ctx = mapping->i_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 = src->index;
if (idx < (pgoff_t)ctx->nr_pages) {
/* Make sure the old folio hasn't already been changed */
if (ctx->ring_folios[idx] != src)
rc = -EAGAIN;
} else
rc = -EINVAL;
if (rc != 0)
goto out_unlock;
/* Writeback must be complete */
BUG_ON(folio_test_writeback(src));
folio_get(dst);
rc = folio_migrate_mapping(mapping, dst, src, 1);
if (rc != MIGRATEPAGE_SUCCESS) {
folio_put(dst);
goto out_unlock;
}
/* Take completion_lock to prevent other writes to the ring buffer
* while the old folio is copied to the new. This prevents new
* events from being lost.
*/
spin_lock_irqsave(&ctx->completion_lock, flags);
folio_copy(dst, src);
folio_migrate_flags(dst, src);
BUG_ON(ctx->ring_folios[idx] != src);
ctx->ring_folios[idx] = dst;
spin_unlock_irqrestore(&ctx->completion_lock, flags);
/* The old folio is no longer accessible. */
folio_put(src);
out_unlock:
mutex_unlock(&ctx->ring_lock);
out:
spin_unlock(&mapping->i_private_lock);
return rc;
}
#else
#define aio_migrate_folio NULL
#endif
static const struct address_space_operations aio_ctx_aops = {
.dirty_folio = noop_dirty_folio,
.migrate_folio = aio_migrate_folio,
};
static int aio_setup_ring(struct kioctx *ctx, unsigned int nr_events)
{
struct aio_ring *ring;
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_folios = ctx->internal_folios;
if (nr_pages > AIO_RING_PAGES) {
ctx->ring_folios = kcalloc(nr_pages, sizeof(struct folio *),
GFP_KERNEL);
if (!ctx->ring_folios) {
put_aio_ring_file(ctx);
return -ENOMEM;
}
}
for (i = 0; i < nr_pages; i++) {
struct folio *folio;
folio = __filemap_get_folio(file->f_mapping, i,
FGP_LOCK | FGP_ACCESSED | FGP_CREAT,
GFP_USER | __GFP_ZERO);
if (IS_ERR(folio))
break;
pr_debug("pid(%d) [%d] folio->count=%d\n", current->pid, i,
folio_ref_count(folio));
folio_end_read(folio, true);
ctx->ring_folios[i] = folio;
}
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 (mmap_write_lock_killable(mm)) {
ctx->mmap_size = 0;
aio_free_ring(ctx);
return -EINTR;
}
ctx->mmap_base = do_mmap(ctx->aio_ring_file, 0, ctx->mmap_size,
PROT_READ | PROT_WRITE,
MAP_SHARED, 0, 0, &unused, NULL);
mmap_write_unlock(mm);
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 = folio_address(ctx->ring_folios[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);
flush_dcache_folio(ctx->ring_folios[0]);
return 0;
}
#define AIO_EVENTS_PER_PAGE (PAGE_SIZE / sizeof(struct io_event))
#define AIO_EVENTS_FIRST_PAGE ((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event))
#define AIO_EVENTS_OFFSET (AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE)
void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel)
{
struct aio_kiocb *req;
struct kioctx *ctx;
unsigned long flags;
/*
* kiocb didn't come from aio or is neither a read nor a write, hence
* ignore it.
*/
if (!(iocb->ki_flags & IOCB_AIO_RW))
return;
req = container_of(iocb, struct aio_kiocb, rw);
if (WARN_ON_ONCE(!list_empty(&req->ki_list)))
return;
ctx = req->ki_ctx;
spin_lock_irqsave(&ctx->ctx_lock, flags);
list_add_tail(&req->ki_list, &ctx->active_reqs);
req->ki_cancel = cancel;
spin_unlock_irqrestore(&ctx->ctx_lock, flags);
}
EXPORT_SYMBOL(kiocb_set_cancel_fn);
/*
* free_ioctx() should be RCU delayed to synchronize against the RCU
* protected lookup_ioctx() and also needs process context to call
* aio_free_ring(). Use rcu_work.
*/
static void free_ioctx(struct work_struct *work)
{
struct kioctx *ctx = container_of(to_rcu_work(work), struct kioctx,
free_rwork);
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);
}
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);
/* Synchronize against RCU protected table->table[] dereferences */
INIT_RCU_WORK(&ctx->free_rwork, free_ioctx);
queue_rcu_work(system_wq, &ctx->free_rwork);
}
/*
* 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);
req->ki_cancel(&req->rw);
list_del_init(&req->ki_list);
}
spin_unlock_irq(&ctx->ctx_lock);
percpu_ref_kill(&ctx->reqs);
percpu_ref_put(&ctx->reqs);
}
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 (!rcu_access_pointer(table->table[i])) {
ctx->id = i;
rcu_assign_pointer(table->table[i], ctx);
spin_unlock(&mm->ioctx_lock);
/* While kioctx setup is in progress,
* we are protected from page migration
* changes ring_folios by ->ring_lock.
*/
ring = folio_address(ctx->ring_folios[0]);
ring->id = ctx->id;
return 0;
}
new_nr = (table ? table->nr : 1) * 4;
spin_unlock(&mm->ioctx_lock);
table = kzalloc(struct_size(table, table, 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;
}
}
}
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);
}
/* 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;
/*
* Store the original nr_events -- what userspace passed to io_setup(),
* for counting against the global limit -- before it changes.
*/
unsigned int max_reqs = nr_events;
/*
* 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)max_reqs > aio_max_nr)
return ERR_PTR(-EAGAIN);
ctx = kmem_cache_zalloc(kioctx_cachep, GFP_KERNEL);
if (!ctx)
return ERR_PTR(-ENOMEM);
ctx->max_reqs = max_reqs;
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(&ctx->wait);
INIT_LIST_HEAD(&ctx->active_reqs);
if (percpu_ref_init(&ctx->users, free_ioctx_users, 0, GFP_KERNEL))
goto err;
if (percpu_ref_init(&ctx->reqs, free_ioctx_reqs, 0, GFP_KERNEL))
goto err;
ctx->cpu = alloc_percpu(struct kioctx_cpu);
if (!ctx->cpu)
goto err;
err = aio_setup_ring(ctx, nr_events);
if (err < 0)
goto err;
atomic_set(&ctx->reqs_available, ctx->nr_events - 1);
ctx->req_batch = (ctx->nr_events - 1) / (num_possible_cpus() * 4);
if (ctx->req_batch < 1)
ctx->req_batch = 1;
/* limit the number of system wide aios */
spin_lock(&aio_nr_lock);
if (aio_nr + ctx->max_reqs > aio_max_nr ||
aio_nr + ctx->max_reqs < aio_nr) {
spin_unlock(&aio_nr_lock);
err = -EAGAIN;
goto err_ctx;
}
aio_nr += ctx->max_reqs;
spin_unlock(&aio_nr_lock);
percpu_ref_get(&ctx->users); /* io_setup() will drop this ref */
percpu_ref_get(&ctx->reqs); /* free_ioctx_users() will drop this */
err = ioctx_add_table(ctx, mm);
if (err)
goto err_cleanup;
/* Release the ring_lock mutex now that all setup is complete. */
mutex_unlock(&ctx->ring_lock);
pr_debug("allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",
ctx, ctx->user_id, mm, ctx->nr_events);
return ctx;
err_cleanup:
aio_nr_sub(ctx->max_reqs);
err_ctx:
atomic_set(&ctx->dead, 1);
if (ctx->mmap_size)
vm_munmap(ctx->mmap_base, ctx->mmap_size);
aio_free_ring(ctx);
err:
mutex_unlock(&ctx->ring_lock);
free_percpu(ctx->cpu);
percpu_ref_exit(&ctx->reqs);
percpu_ref_exit(&ctx->users);
kmem_cache_free(kioctx_cachep, ctx);
pr_debug("error allocating ioctx %d\n", err);
return ERR_PTR(err);
}
/* kill_ioctx
* Cancels all outstanding aio requests on an aio context. Used
* when the processes owning a context have all exited to encourage
* the rapid destruction of the kioctx.
*/
static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx,
struct ctx_rq_wait *wait)
{
struct kioctx_table *table;
spin_lock(&mm->ioctx_lock);
if (atomic_xchg(&ctx->dead, 1)) {
spin_unlock(&mm->ioctx_lock);
return -EINVAL;
}
table = rcu_dereference_raw(mm->ioctx_table);
WARN_ON(ctx != rcu_access_pointer(table->table[ctx->id]));
RCU_INIT_POINTER(table->table[ctx->id], NULL);
spin_unlock(&mm->ioctx_lock);
/* free_ioctx_reqs() will do the necessary RCU synchronization */
wake_up_all(&ctx->wait);
/*
* It'd be more correct to do this in free_ioctx(), after all
* the outstanding kiocbs have finished - but by then io_destroy
* has already returned, so io_setup() could potentially return
* -EAGAIN with no ioctxs actually in use (as far as userspace
* could tell).
*/
aio_nr_sub(ctx->max_reqs);
if (ctx->mmap_size)
vm_munmap(ctx->mmap_base, ctx->mmap_size);
ctx->rq_wait = wait;
percpu_ref_kill(&ctx->users);
return 0;
}
/*
* exit_aio: called when the last user of mm goes away. At this point, there is
* no way for any new requests to be submited or any of the io_* syscalls to be
* called on the context.
*
* There may be outstanding kiocbs, but free_ioctx() will explicitly wait on
* them.
*/
void exit_aio(struct mm_struct *mm)
{
struct kioctx_table *table = rcu_dereference_raw(mm->ioctx_table);
struct ctx_rq_wait wait;
int i, skipped;
if (!table)
return;
atomic_set(&wait.count, table->nr);
init_completion(&wait.comp);
skipped = 0;
for (i = 0; i < table->nr; ++i) {
struct kioctx *ctx =
rcu_dereference_protected(table->table[i], true);
if (!ctx) {
skipped++;
continue;
}
/*
* We don't need to bother with munmap() here - exit_mmap(mm)
* is coming and it'll unmap everything. And we simply can't,
* this is not necessarily our ->mm.
* Since kill_ioctx() uses non-zero ->mmap_size as indicator
* that it needs to unmap the area, just set it to 0.
*/
ctx->mmap_size = 0;
kill_ioctx(mm, ctx, &wait);
}
if (!atomic_sub_and_test(skipped, &wait.count)) {
/* Wait until all IO for the context are done. */
wait_for_completion(&wait.comp);
}
RCU_INIT_POINTER(mm->ioctx_table, NULL);
kfree(table);
}
static void put_reqs_available(struct kioctx *ctx, unsigned nr)
{
struct kioctx_cpu *kcpu;
unsigned long flags;
local_irq_save(flags);
kcpu = this_cpu_ptr(ctx->cpu);
kcpu->reqs_available += nr;
while (kcpu->reqs_available >= ctx->req_batch * 2) {
kcpu->reqs_available -= ctx->req_batch;
atomic_add(ctx->req_batch, &ctx->reqs_available);
}
local_irq_restore(flags);
}
static bool __get_reqs_available(struct kioctx *ctx)
{
struct kioctx_cpu *kcpu;
bool ret = false;
unsigned long flags;
local_irq_save(flags);
kcpu = this_cpu_ptr(ctx->cpu);
if (!kcpu->reqs_available) {
int avail = atomic_read(&ctx->reqs_available);
do {
if (avail < ctx->req_batch)
goto out;
} while (!atomic_try_cmpxchg(&ctx->reqs_available,
&avail, avail - ctx->req_batch));
kcpu->reqs_available += ctx->req_batch;
}
ret = true;
kcpu->reqs_available--;
out:
local_irq_restore(flags);
return ret;
}
/* refill_reqs_available
* Updates the reqs_available reference counts used for tracking the
* number of free slots in the completion ring. This can be called
* from aio_complete() (to optimistically update reqs_available) or
* from aio_get_req() (the we're out of events case). It must be
* called holding ctx->completion_lock.
*/
static void refill_reqs_available(struct kioctx *ctx, unsigned head,
unsigned tail)
{
unsigned events_in_ring, completed;
/* Clamp head since userland can write to it. */
head %= ctx->nr_events;
if (head <= tail)
events_in_ring = tail - head;
else
events_in_ring = ctx->nr_events - (head - tail);
completed = ctx->completed_events;
if (events_in_ring < completed)
completed -= events_in_ring;
else
completed = 0;
if (!completed)
return;
ctx->completed_events -= completed;
put_reqs_available(ctx, completed);
}
/* user_refill_reqs_available
* Called to refill reqs_available when aio_get_req() encounters an
* out of space in the completion ring.
*/
static void user_refill_reqs_available(struct kioctx *ctx)
{
spin_lock_irq(&ctx->completion_lock);
if (ctx->completed_events) {
struct aio_ring *ring;
unsigned head;
/* Access of ring->head may race with aio_read_events_ring()
* here, but that's okay since whether we read the old version
* or the new version, and either will be valid. The important
* part is that head cannot pass tail since we prevent
* aio_complete() from updating tail by holding
* ctx->completion_lock. Even if head is invalid, the check
* against ctx->completed_events below will make sure we do the
* safe/right thing.
*/
ring = folio_address(ctx->ring_folios[0]);
head = ring->head;
refill_reqs_available(ctx, head, ctx->tail);
}
spin_unlock_irq(&ctx->completion_lock);
}
static bool get_reqs_available(struct kioctx *ctx)
{
if (__get_reqs_available(ctx))
return true;
user_refill_reqs_available(ctx);
return __get_reqs_available(ctx);
}
/* aio_get_req
* Allocate a slot for an aio request.
* Returns NULL if no requests are free.
*
* The refcount is initialized to 2 - one for the async op completion,
* one for the synchronous code that does this.
*/
static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx)
{
struct aio_kiocb *req;
req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL);
if (unlikely(!req))
return NULL;
if (unlikely(!get_reqs_available(ctx))) {
kmem_cache_free(kiocb_cachep, req);
return NULL;
}
percpu_ref_get(&ctx->reqs);
req->ki_ctx = ctx;
INIT_LIST_HEAD(&req->ki_list);
refcount_set(&req->ki_refcnt, 2);
req->ki_eventfd = NULL;
return req;
}
static struct kioctx *lookup_ioctx(unsigned long ctx_id)
{
struct aio_ring __user *ring = (void __user *)ctx_id;
struct mm_struct *mm = current->mm;
struct kioctx *ctx, *ret = NULL;
struct kioctx_table *table;
unsigned id;
if (get_user(id, &ring->id))
return NULL;
rcu_read_lock();
table = rcu_dereference(mm->ioctx_table);
if (!table || id >= table->nr)
goto out;
id = array_index_nospec(id, table->nr);
ctx = rcu_dereference(table->table[id]);
if (ctx && ctx->user_id == ctx_id) {
if (percpu_ref_tryget_live(&ctx->users))
ret = ctx;
}
out:
rcu_read_unlock();
return ret;
}
static inline void iocb_destroy(struct aio_kiocb *iocb)
{
if (iocb->ki_eventfd)
eventfd_ctx_put(iocb->ki_eventfd);
if (iocb->ki_filp)
fput(iocb->ki_filp);
percpu_ref_put(&iocb->ki_ctx->reqs);
kmem_cache_free(kiocb_cachep, iocb);
}
struct aio_waiter {
struct wait_queue_entry w;
size_t min_nr;
};
/* aio_complete
* Called when the io request on the given iocb is complete.
*/
static void aio_complete(struct aio_kiocb *iocb)
{
struct kioctx *ctx = iocb->ki_ctx;
struct aio_ring *ring;
struct io_event *ev_page, *event;
unsigned tail, pos, head, avail;
unsigned long flags;
/*
* Add a completion event to the ring buffer. Must be done holding
* ctx->completion_lock to prevent other code from messing with the tail
* pointer since we might be called from irq context.
*/
spin_lock_irqsave(&ctx->completion_lock, flags);
tail = ctx->tail;
pos = tail + AIO_EVENTS_OFFSET;
if (++tail >= ctx->nr_events)
tail = 0;
ev_page = folio_address(ctx->ring_folios[pos / AIO_EVENTS_PER_PAGE]);
event = ev_page + pos % AIO_EVENTS_PER_PAGE;
*event = iocb->ki_res;
flush_dcache_folio(ctx->ring_folios[pos / AIO_EVENTS_PER_PAGE]);
pr_debug("%p[%u]: %p: %p %Lx %Lx %Lx\n", ctx, tail, iocb,
(void __user *)(unsigned long)iocb->ki_res.obj,
iocb->ki_res.data, iocb->ki_res.res, iocb->ki_res.res2);
/* after flagging the request as done, we
* must never even look at it again
*/
smp_wmb(); /* make event visible before updating tail */
ctx->tail = tail;
ring = folio_address(ctx->ring_folios[0]);
head = ring->head;
ring->tail = tail;
flush_dcache_folio(ctx->ring_folios[0]);
ctx->completed_events++;
if (ctx->completed_events > 1)
refill_reqs_available(ctx, head, tail);
avail = tail > head
? tail - head
: tail + ctx->nr_events - head;
spin_unlock_irqrestore(&ctx->completion_lock, flags);
pr_debug("added to ring %p at [%u]\n", iocb, tail);
/*
* Check if the user asked us to deliver the result through an
* eventfd. The eventfd_signal() function is safe to be called
* from IRQ context.
*/
if (iocb->ki_eventfd)
eventfd_signal(iocb->ki_eventfd);
/*
* We have to order our ring_info tail store above and test
* of the wait list below outside the wait lock. This is
* like in wake_up_bit() where clearing a bit has to be
* ordered with the unlocked test.
*/
smp_mb();
if (waitqueue_active(&ctx->wait)) {
struct aio_waiter *curr, *next;
unsigned long flags;
spin_lock_irqsave(&ctx->wait.lock, flags);
list_for_each_entry_safe(curr, next, &ctx->wait.head, w.entry)
if (avail >= curr->min_nr) {
wake_up_process(curr->w.private);
list_del_init_careful(&curr->w.entry);
}
spin_unlock_irqrestore(&ctx->wait.lock, flags);
}
}
static inline void iocb_put(struct aio_kiocb *iocb)
{
if (refcount_dec_and_test(&iocb->ki_refcnt)) {
aio_complete(iocb);
iocb_destroy(iocb);
}
}
/* aio_read_events_ring
* Pull an event off of the ioctx's event ring. Returns the number of
* events fetched
*/
static long aio_read_events_ring(struct kioctx *ctx,
struct io_event __user *event, long nr)
{
struct aio_ring *ring;
unsigned head, tail, pos;
long ret = 0;
int copy_ret;
/*
* The mutex can block and wake us up and that will cause
* wait_event_interruptible_hrtimeout() to schedule without sleeping
* and repeat. This should be rare enough that it doesn't cause
* peformance issues. See the comment in read_events() for more detail.
*/
sched_annotate_sleep();
mutex_lock(&ctx->ring_lock);
/* Access to ->ring_folios here is protected by ctx->ring_lock. */
ring = folio_address(ctx->ring_folios[0]);
head = ring->head;
tail = ring->tail;
/*
* Ensure that once we've read the current tail pointer, that
* we also see the events that were stored up to the tail.
*/
smp_rmb();
pr_debug("h%u t%u m%u\n", head, tail, ctx->nr_events);
if (head == tail)
goto out;
head %= ctx->nr_events;
tail %= ctx->nr_events;
while (ret < nr) {
long avail;
struct io_event *ev;
struct folio *folio;
avail = (head <= tail ? tail : ctx->nr_events) - head;
if (head == tail)
break;
pos = head + AIO_EVENTS_OFFSET;
folio = ctx->ring_folios[pos / AIO_EVENTS_PER_PAGE];
pos %= AIO_EVENTS_PER_PAGE;
avail = min(avail, nr - ret);
avail = min_t(long, avail, AIO_EVENTS_PER_PAGE - pos);
ev = folio_address(folio);
copy_ret = copy_to_user(event + ret, ev + pos,
sizeof(*ev) * avail);
if (unlikely(copy_ret)) {
ret = -EFAULT;
goto out;
}
ret += avail;
head += avail;
head %= ctx->nr_events;
}
ring = folio_address(ctx->ring_folios[0]);
ring->head = head;
flush_dcache_folio(ctx->ring_folios[0]);
pr_debug("%li h%u t%u\n", ret, head, tail);
out:
mutex_unlock(&ctx->ring_lock);
return ret;
}
static bool aio_read_events(struct kioctx *ctx, long min_nr, long nr,
struct io_event __user *event, long *i)
{
long ret = aio_read_events_ring(ctx, event + *i, nr - *i);
if (ret > 0)
*i += ret;
if (unlikely(atomic_read(&ctx->dead)))
ret = -EINVAL;
if (!*i)
*i = ret;
return ret < 0 || *i >= min_nr;
}
static long read_events(struct kioctx *ctx, long min_nr, long nr,
struct io_event __user *event,
ktime_t until)
{
struct hrtimer_sleeper t;
struct aio_waiter w;
long ret = 0, ret2 = 0;
/*
* Note that aio_read_events() is being called as the conditional - i.e.
* we're calling it after prepare_to_wait() has set task state to
* TASK_INTERRUPTIBLE.
*
* But aio_read_events() can block, and if it blocks it's going to flip
* the task state back to TASK_RUNNING.
*
* This should be ok, provided it doesn't flip the state back to
* TASK_RUNNING and return 0 too much - that causes us to spin. That
* will only happen if the mutex_lock() call blocks, and we then find
* the ringbuffer empty. So in practice we should be ok, but it's
* something to be aware of when touching this code.
*/
aio_read_events(ctx, min_nr, nr, event, &ret);
if (until == 0 || ret < 0 || ret >= min_nr)
return ret;
hrtimer_init_sleeper_on_stack(&t, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
if (until != KTIME_MAX) {
hrtimer_set_expires_range_ns(&t.timer, until, current->timer_slack_ns);
hrtimer_sleeper_start_expires(&t, HRTIMER_MODE_REL);
}
init_wait(&w.w);
while (1) {
unsigned long nr_got = ret;
w.min_nr = min_nr - ret;
ret2 = prepare_to_wait_event(&ctx->wait, &w.w, TASK_INTERRUPTIBLE);
if (!ret2 && !t.task)
ret2 = -ETIME;
if (aio_read_events(ctx, min_nr, nr, event, &ret) || ret2)
break;
if (nr_got == ret)
schedule();
}
finish_wait(&ctx->wait, &w.w);
hrtimer_cancel(&t.timer);
destroy_hrtimer_on_stack(&t.timer);
return ret;
}
/* sys_io_setup:
* Create an aio_context capable of receiving at least nr_events.
* ctxp must not point to an aio_context that already exists, and
* must be initialized to 0 prior to the call. On successful
* creation of the aio_context, *ctxp is filled in with the resulting
* handle. May fail with -EINVAL if *ctxp is not initialized,
* if the specified nr_events exceeds internal limits. May fail
* with -EAGAIN if the specified nr_events exceeds the user's limit
* of available events. May fail with -ENOMEM if insufficient kernel
* resources are available. May fail with -EFAULT if an invalid
* pointer is passed for ctxp. Will fail with -ENOSYS if not
* implemented.
*/
SYSCALL_DEFINE2(io_setup, unsigned, nr_events, aio_context_t __user *, ctxp)
{
struct kioctx *ioctx = NULL;
unsigned long ctx;
long ret;
ret = get_user(ctx, ctxp);
if (unlikely(ret))
goto out;
ret = -EINVAL;
if (unlikely(ctx || nr_events == 0)) {
pr_debug("EINVAL: ctx %lu nr_events %u\n",
ctx, nr_events);
goto out;
}
ioctx = ioctx_alloc(nr_events);
ret = PTR_ERR(ioctx);
if (!IS_ERR(ioctx)) {
ret = put_user(ioctx->user_id, ctxp);
if (ret)
kill_ioctx(current->mm, ioctx, NULL);
percpu_ref_put(&ioctx->users);
}
out:
return ret;
}
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE2(io_setup, unsigned, nr_events, u32 __user *, ctx32p)
{
struct kioctx *ioctx = NULL;
unsigned long ctx;
long ret;
ret = get_user(ctx, ctx32p);
if (unlikely(ret))
goto out;
ret = -EINVAL;
if (unlikely(ctx || nr_events == 0)) {
pr_debug("EINVAL: ctx %lu nr_events %u\n",
ctx, nr_events);
goto out;
}
ioctx = ioctx_alloc(nr_events);
ret = PTR_ERR(ioctx);
if (!IS_ERR(ioctx)) {
/* truncating is ok because it's a user address */
ret = put_user((u32)ioctx->user_id, ctx32p);
if (ret)
kill_ioctx(current->mm, ioctx, NULL);
percpu_ref_put(&ioctx->users);
}
out:
return ret;
}
#endif
/* sys_io_destroy:
* Destroy the aio_context specified. May cancel any outstanding
* AIOs and block on completion. Will fail with -ENOSYS if not
* implemented. May fail with -EINVAL if the context pointed to
* is invalid.
*/
SYSCALL_DEFINE1(io_destroy, aio_context_t, ctx)
{
struct kioctx *ioctx = lookup_ioctx(ctx);
if (likely(NULL != ioctx)) {
struct ctx_rq_wait wait;
int ret;
init_completion(&wait.comp);
atomic_set(&wait.count, 1);
/* Pass requests_done to kill_ioctx() where it can be set
* in a thread-safe way. If we try to set it here then we have
* a race condition if two io_destroy() called simultaneously.
*/
ret = kill_ioctx(current->mm, ioctx, &wait);
percpu_ref_put(&ioctx->users);
/* Wait until all IO for the context are done. Otherwise kernel
* keep using user-space buffers even if user thinks the context
* is destroyed.
*/
if (!ret)
wait_for_completion(&wait.comp);
return ret;
}
pr_debug("EINVAL: invalid context id\n");
return -EINVAL;
}
static void aio_remove_iocb(struct aio_kiocb *iocb)
{
struct kioctx *ctx = iocb->ki_ctx;
unsigned long flags;
spin_lock_irqsave(&ctx->ctx_lock, flags);
list_del(&iocb->ki_list);
spin_unlock_irqrestore(&ctx->ctx_lock, flags);
}
static void aio_complete_rw(struct kiocb *kiocb, long res)
{
struct aio_kiocb *iocb = container_of(kiocb, struct aio_kiocb, rw);
if (!list_empty_careful(&iocb->ki_list))
aio_remove_iocb(iocb);
if (kiocb->ki_flags & IOCB_WRITE) {
struct inode *inode = file_inode(kiocb->ki_filp);
if (S_ISREG(inode->i_mode))
kiocb_end_write(kiocb);
}
iocb->ki_res.res = res;
iocb->ki_res.res2 = 0;
iocb_put(iocb);
}
static int aio_prep_rw(struct kiocb *req, const struct iocb *iocb, int rw_type)
{
int ret;
req->ki_complete = aio_complete_rw;
req->private = NULL;
req->ki_pos = iocb->aio_offset;
req->ki_flags = req->ki_filp->f_iocb_flags | IOCB_AIO_RW;
if (iocb->aio_flags & IOCB_FLAG_RESFD)
req->ki_flags |= IOCB_EVENTFD;
if (iocb->aio_flags & IOCB_FLAG_IOPRIO) {
/*
* If the IOCB_FLAG_IOPRIO flag of aio_flags is set, then
* aio_reqprio is interpreted as an I/O scheduling
* class and priority.
*/
ret = ioprio_check_cap(iocb->aio_reqprio);
if (ret) {
pr_debug("aio ioprio check cap error: %d\n", ret);
return ret;
}
req->ki_ioprio = iocb->aio_reqprio;
} else
req->ki_ioprio = get_current_ioprio();
ret = kiocb_set_rw_flags(req, iocb->aio_rw_flags, rw_type);
if (unlikely(ret))
return ret;
req->ki_flags &= ~IOCB_HIPRI; /* no one is going to poll for this I/O */
return 0;
}
static ssize_t aio_setup_rw(int rw, const struct iocb *iocb,
struct iovec **iovec, bool vectored, bool compat,
struct iov_iter *iter)
{
void __user *buf = (void __user *)(uintptr_t)iocb->aio_buf;
size_t len = iocb->aio_nbytes;
if (!vectored) {
ssize_t ret = import_ubuf(rw, buf, len, iter);
*iovec = NULL;
return ret;
}
return __import_iovec(rw, buf, len, UIO_FASTIOV, iovec, iter, compat);
}
static inline void aio_rw_done(struct kiocb *req, ssize_t ret)
{
switch (ret) {
case -EIOCBQUEUED:
break;
case -ERESTARTSYS:
case -ERESTARTNOINTR:
case -ERESTARTNOHAND:
case -ERESTART_RESTARTBLOCK:
/*
* There's no easy way to restart the syscall since other AIO's
* may be already running. Just fail this IO with EINTR.
*/
ret = -EINTR;
fallthrough;
default:
req->ki_complete(req, ret);
}
}
static int aio_read(struct kiocb *req, const struct iocb *iocb,
bool vectored, bool compat)
{
struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
struct iov_iter iter;
struct file *file;
int ret;
ret = aio_prep_rw(req, iocb, READ);
if (ret)
return ret;
file = req->ki_filp;
if (unlikely(!(file->f_mode & FMODE_READ)))
return -EBADF;
if (unlikely(!file->f_op->read_iter))
return -EINVAL;
ret = aio_setup_rw(ITER_DEST, iocb, &iovec, vectored, compat, &iter);
if (ret < 0)
return ret;
ret = rw_verify_area(READ, file, &req->ki_pos, iov_iter_count(&iter));
if (!ret)
aio_rw_done(req, file->f_op->read_iter(req, &iter));
kfree(iovec);
return ret;
}
static int aio_write(struct kiocb *req, const struct iocb *iocb,
bool vectored, bool compat)
{
struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
struct iov_iter iter;
struct file *file;
int ret;
ret = aio_prep_rw(req, iocb, WRITE);
if (ret)
return ret;
file = req->ki_filp;
if (unlikely(!(file->f_mode & FMODE_WRITE)))
return -EBADF;
if (unlikely(!file->f_op->write_iter))
return -EINVAL;
ret = aio_setup_rw(ITER_SOURCE, iocb, &iovec, vectored, compat, &iter);
if (ret < 0)
return ret;
ret = rw_verify_area(WRITE, file, &req->ki_pos, iov_iter_count(&iter));
if (!ret) {
if (S_ISREG(file_inode(file)->i_mode))
kiocb_start_write(req);
req->ki_flags |= IOCB_WRITE;
aio_rw_done(req, file->f_op->write_iter(req, &iter));
}
kfree(iovec);
return ret;
}
static void aio_fsync_work(struct work_struct *work)
{
struct aio_kiocb *iocb = container_of(work, struct aio_kiocb, fsync.work);
const struct cred *old_cred = override_creds(iocb->fsync.creds);
iocb->ki_res.res = vfs_fsync(iocb->fsync.file, iocb->fsync.datasync);
revert_creds(old_cred);
put_cred(iocb->fsync.creds);
iocb_put(iocb);
}
static int aio_fsync(struct fsync_iocb *req, const struct iocb *iocb,
bool datasync)
{
if (unlikely(iocb->aio_buf || iocb->aio_offset || iocb->aio_nbytes ||
iocb->aio_rw_flags))
return -EINVAL;
if (unlikely(!req->file->f_op->fsync))
return -EINVAL;
req->creds = prepare_creds();
if (!req->creds)
return -ENOMEM;
req->datasync = datasync;
INIT_WORK(&req->work, aio_fsync_work);
schedule_work(&req->work);
return 0;
}
static void aio_poll_put_work(struct work_struct *work)
{
struct poll_iocb *req = container_of(work, struct poll_iocb, work);
struct aio_kiocb *iocb = container_of(req, struct aio_kiocb, poll);
iocb_put(iocb);
}
/*
* Safely lock the waitqueue which the request is on, synchronizing with the
* case where the ->poll() provider decides to free its waitqueue early.
*
* Returns true on success, meaning that req->head->lock was locked, req->wait
* is on req->head, and an RCU read lock was taken. Returns false if the
* request was already removed from its waitqueue (which might no longer exist).
*/
static bool poll_iocb_lock_wq(struct poll_iocb *req)
{
wait_queue_head_t *head;
/*
* While we hold the waitqueue lock and the waitqueue is nonempty,
* wake_up_pollfree() will wait for us. However, taking the waitqueue
* lock in the first place can race with the waitqueue being freed.
*
* We solve this as eventpoll does: by taking advantage of the fact that
* all users of wake_up_pollfree() will RCU-delay the actual free. If
* we enter rcu_read_lock() and see that the pointer to the queue is
* non-NULL, we can then lock it without the memory being freed out from
* under us, then check whether the request is still on the queue.
*
* Keep holding rcu_read_lock() as long as we hold the queue lock, in
* case the caller deletes the entry from the queue, leaving it empty.
* In that case, only RCU prevents the queue memory from being freed.
*/
rcu_read_lock();
head = smp_load_acquire(&req->head);
if (head) {
spin_lock(&head->lock);
if (!list_empty(&req->wait.entry))
return true;
spin_unlock(&head->lock);
}
rcu_read_unlock();
return false;
}
static void poll_iocb_unlock_wq(struct poll_iocb *req)
{
spin_unlock(&req->head->lock);
rcu_read_unlock();
}
static void aio_poll_complete_work(struct work_struct *work)
{
struct poll_iocb *req = container_of(work, struct poll_iocb, work);
struct aio_kiocb *iocb = container_of(req, struct aio_kiocb, poll);
struct poll_table_struct pt = { ._key = req->events };
struct kioctx *ctx = iocb->ki_ctx;
__poll_t mask = 0;
if (!READ_ONCE(req->cancelled))
mask = vfs_poll(req->file, &pt) & req->events;
/*
* Note that ->ki_cancel callers also delete iocb from active_reqs after
* calling ->ki_cancel. We need the ctx_lock roundtrip here to
* synchronize with them. In the cancellation case the list_del_init
* itself is not actually needed, but harmless so we keep it in to
* avoid further branches in the fast path.
*/
spin_lock_irq(&ctx->ctx_lock);
if (poll_iocb_lock_wq(req)) {
if (!mask && !READ_ONCE(req->cancelled)) {
/*
* The request isn't actually ready to be completed yet.
* Reschedule completion if another wakeup came in.
*/
if (req->work_need_resched) {
schedule_work(&req->work);
req->work_need_resched = false;
} else {
req->work_scheduled = false;
}
poll_iocb_unlock_wq(req);
spin_unlock_irq(&ctx->ctx_lock);
return;
}
list_del_init(&req->wait.entry);
poll_iocb_unlock_wq(req);
} /* else, POLLFREE has freed the waitqueue, so we must complete */
list_del_init(&iocb->ki_list);
iocb->ki_res.res = mangle_poll(mask);
spin_unlock_irq(&ctx->ctx_lock);
iocb_put(iocb);
}
/* assumes we are called with irqs disabled */
static int aio_poll_cancel(struct kiocb *iocb)
{
struct aio_kiocb *aiocb = container_of(iocb, struct aio_kiocb, rw);
struct poll_iocb *req = &aiocb->poll;
if (poll_iocb_lock_wq(req)) {
WRITE_ONCE(req->cancelled, true);
if (!req->work_scheduled) {
schedule_work(&aiocb->poll.work);
req->work_scheduled = true;
}
poll_iocb_unlock_wq(req);
} /* else, the request was force-cancelled by POLLFREE already */
return 0;
}
static int aio_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
void *key)
{
struct poll_iocb *req = container_of(wait, struct poll_iocb, wait);
struct aio_kiocb *iocb = container_of(req, struct aio_kiocb, poll);
__poll_t mask = key_to_poll(key);
unsigned long flags;
/* for instances that support it check for an event match first: */
if (mask && !(mask & req->events))
return 0;
/*
* Complete the request inline if possible. This requires that three
* conditions be met:
* 1. An event mask must have been passed. If a plain wakeup was done
* instead, then mask == 0 and we have to call vfs_poll() to get
* the events, so inline completion isn't possible.
* 2. The completion work must not have already been scheduled.
* 3. ctx_lock must not be busy. We have to use trylock because we
* already hold the waitqueue lock, so this inverts the normal
* locking order. Use irqsave/irqrestore because not all
* filesystems (e.g. fuse) call this function with IRQs disabled,
* yet IRQs have to be disabled before ctx_lock is obtained.
*/
if (mask && !req->work_scheduled &&
spin_trylock_irqsave(&iocb->ki_ctx->ctx_lock, flags)) {
struct kioctx *ctx = iocb->ki_ctx;
list_del_init(&req->wait.entry);
list_del(&iocb->ki_list);
iocb->ki_res.res = mangle_poll(mask);
if (iocb->ki_eventfd && !eventfd_signal_allowed()) {
iocb = NULL;
INIT_WORK(&req->work, aio_poll_put_work);
schedule_work(&req->work);
}
spin_unlock_irqrestore(&ctx->ctx_lock, flags);
if (iocb)
iocb_put(iocb);
} else {
/*
* Schedule the completion work if needed. If it was already
* scheduled, record that another wakeup came in.
*
* Don't remove the request from the waitqueue here, as it might
* not actually be complete yet (we won't know until vfs_poll()
* is called), and we must not miss any wakeups. POLLFREE is an
* exception to this; see below.
*/
if (req->work_scheduled) {
req->work_need_resched = true;
} else {
schedule_work(&req->work);
req->work_scheduled = true;
}
/*
* If the waitqueue is being freed early but we can't complete
* the request inline, we have to tear down the request as best
* we can. That means immediately removing the request from its
* waitqueue and preventing all further accesses to the
* waitqueue via the request. We also need to schedule the
* completion work (done above). Also mark the request as
* cancelled, to potentially skip an unneeded call to ->poll().
*/
if (mask & POLLFREE) {
WRITE_ONCE(req->cancelled, true);
list_del_init(&req->wait.entry);
/*
* Careful: this *must* be the last step, since as soon
* as req->head is NULL'ed out, the request can be
* completed and freed, since aio_poll_complete_work()
* will no longer need to take the waitqueue lock.
*/
smp_store_release(&req->head, NULL);
}
}
return 1;
}
struct aio_poll_table {
struct poll_table_struct pt;
struct aio_kiocb *iocb;
bool queued;
int error;
};
static void
aio_poll_queue_proc(struct file *file, struct wait_queue_head *head,
struct poll_table_struct *p)
{
struct aio_poll_table *pt = container_of(p, struct aio_poll_table, pt);
/* multiple wait queues per file are not supported */
if (unlikely(pt->queued)) {
pt->error = -EINVAL;
return;
}
pt->queued = true;
pt->error = 0;
pt->iocb->poll.head = head;
add_wait_queue(head, &pt->iocb->poll.wait);
}
static int aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb)
{
struct kioctx *ctx = aiocb->ki_ctx;
struct poll_iocb *req = &aiocb->poll;
struct aio_poll_table apt;
bool cancel = false;
__poll_t mask;
/* reject any unknown events outside the normal event mask. */
if ((u16)iocb->aio_buf != iocb->aio_buf)
return -EINVAL;
/* reject fields that are not defined for poll */
if (iocb->aio_offset || iocb->aio_nbytes || iocb->aio_rw_flags)
return -EINVAL;
INIT_WORK(&req->work, aio_poll_complete_work);
req->events = demangle_poll(iocb->aio_buf) | EPOLLERR | EPOLLHUP;
req->head = NULL;
req->cancelled = false;
req->work_scheduled = false;
req->work_need_resched = false;
apt.pt._qproc = aio_poll_queue_proc;
apt.pt._key = req->events;
apt.iocb = aiocb;
apt.queued = false;
apt.error = -EINVAL; /* same as no support for IOCB_CMD_POLL */
/* initialized the list so that we can do list_empty checks */
INIT_LIST_HEAD(&req->wait.entry);
init_waitqueue_func_entry(&req->wait, aio_poll_wake);
mask = vfs_poll(req->file, &apt.pt) & req->events;
spin_lock_irq(&ctx->ctx_lock);
if (likely(apt.queued)) {
bool on_queue = poll_iocb_lock_wq(req);
if (!on_queue || req->work_scheduled) {
/*
* aio_poll_wake() already either scheduled the async
* completion work, or completed the request inline.
*/
if (apt.error) /* unsupported case: multiple queues */
cancel = true;
apt.error = 0;
mask = 0;
}
if (mask || apt.error) {
/* Steal to complete synchronously. */
list_del_init(&req->wait.entry);
} else if (cancel) {
/* Cancel if possible (may be too late though). */
WRITE_ONCE(req->cancelled, true);
} else if (on_queue) {
/*
* Actually waiting for an event, so add the request to
* active_reqs so that it can be cancelled if needed.
*/
list_add_tail(&aiocb->ki_list, &ctx->active_reqs);
aiocb->ki_cancel = aio_poll_cancel;
}
if (on_queue)
poll_iocb_unlock_wq(req);
}
if (mask) { /* no async, we'd stolen it */
aiocb->ki_res.res = mangle_poll(mask);
apt.error = 0;
}
spin_unlock_irq(&ctx->ctx_lock);
if (mask)
iocb_put(aiocb);
return apt.error;
}
static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb,
struct iocb __user *user_iocb, struct aio_kiocb *req,
bool compat)
{
req->ki_filp = fget(iocb->aio_fildes);
if (unlikely(!req->ki_filp))
return -EBADF;
if (iocb->aio_flags & IOCB_FLAG_RESFD) {
struct eventfd_ctx *eventfd;
/*
* If the IOCB_FLAG_RESFD flag of aio_flags is set, get an
* instance of the file* now. The file descriptor must be
* an eventfd() fd, and will be signaled for each completed
* event using the eventfd_signal() function.
*/
eventfd = eventfd_ctx_fdget(iocb->aio_resfd);
if (IS_ERR(eventfd))
return PTR_ERR(eventfd);
req->ki_eventfd = eventfd;
}
if (unlikely(put_user(KIOCB_KEY, &user_iocb->aio_key))) {
pr_debug("EFAULT: aio_key\n");
return -EFAULT;
}
req->ki_res.obj = (u64)(unsigned long)user_iocb;
req->ki_res.data = iocb->aio_data;
req->ki_res.res = 0;
req->ki_res.res2 = 0;
switch (iocb->aio_lio_opcode) {
case IOCB_CMD_PREAD:
return aio_read(&req->rw, iocb, false, compat);
case IOCB_CMD_PWRITE:
return aio_write(&req->rw, iocb, false, compat);
case IOCB_CMD_PREADV:
return aio_read(&req->rw, iocb, true, compat);
case IOCB_CMD_PWRITEV:
return aio_write(&req->rw, iocb, true, compat);
case IOCB_CMD_FSYNC:
return aio_fsync(&req->fsync, iocb, false);
case IOCB_CMD_FDSYNC:
return aio_fsync(&req->fsync, iocb, true);
case IOCB_CMD_POLL:
return aio_poll(req, iocb);
default:
pr_debug("invalid aio operation %d\n", iocb->aio_lio_opcode);
return -EINVAL;
}
}
static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
bool compat)
{
struct aio_kiocb *req;
struct iocb iocb;
int err;
if (unlikely(copy_from_user(&iocb, user_iocb, sizeof(iocb))))
return -EFAULT;
/* enforce forwards compatibility on users */
if (unlikely(iocb.aio_reserved2)) {
pr_debug("EINVAL: reserve field set\n");
return -EINVAL;
}
/* prevent overflows */
if (unlikely(
(iocb.aio_buf != (unsigned long)iocb.aio_buf) ||
(iocb.aio_nbytes != (size_t)iocb.aio_nbytes) ||
((ssize_t)iocb.aio_nbytes < 0)
)) {
pr_debug("EINVAL: overflow check\n");
return -EINVAL;
}
req = aio_get_req(ctx);
if (unlikely(!req))
return -EAGAIN;
err = __io_submit_one(ctx, &iocb, user_iocb, req, compat);
/* Done with the synchronous reference */
iocb_put(req);
/*
* If err is 0, we'd either done aio_complete() ourselves or have
* arranged for that to be done asynchronously. Anything non-zero
* means that we need to destroy req ourselves.
*/
if (unlikely(err)) {
iocb_destroy(req);
put_reqs_available(ctx, 1);
}
return err;
}
/* sys_io_submit:
* Queue the nr iocbs pointed to by iocbpp for processing. Returns
* the number of iocbs queued. May return -EINVAL if the aio_context
* specified by ctx_id is invalid, if nr is < 0, if the iocb at
* *iocbpp[0] is not properly initialized, if the operation specified
* is invalid for the file descriptor in the iocb. May fail with
* -EFAULT if any of the data structures point to invalid data. May
* fail with -EBADF if the file descriptor specified in the first
* iocb is invalid. May fail with -EAGAIN if insufficient resources
* are available to queue any iocbs. Will return 0 if nr is 0. Will
* fail with -ENOSYS if not implemented.
*/
SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
struct iocb __user * __user *, iocbpp)
{
struct kioctx *ctx;
long ret = 0;
int i = 0;
struct blk_plug plug;
if (unlikely(nr < 0))
return -EINVAL;
ctx = lookup_ioctx(ctx_id);
if (unlikely(!ctx)) {
pr_debug("EINVAL: invalid context id\n");
return -EINVAL;
}
if (nr > ctx->nr_events)
nr = ctx->nr_events;
if (nr > AIO_PLUG_THRESHOLD)
blk_start_plug(&plug);
for (i = 0; i < nr; i++) {
struct iocb __user *user_iocb;
if (unlikely(get_user(user_iocb, iocbpp + i))) {
ret = -EFAULT;
break;
}
ret = io_submit_one(ctx, user_iocb, false);
if (ret)
break;
}
if (nr > AIO_PLUG_THRESHOLD)
blk_finish_plug(&plug);
percpu_ref_put(&ctx->users);
return i ? i : ret;
}
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE3(io_submit, compat_aio_context_t, ctx_id,
int, nr, compat_uptr_t __user *, iocbpp)
{
struct kioctx *ctx;
long ret = 0;
int i = 0;
struct blk_plug plug;
if (unlikely(nr < 0))
return -EINVAL;
ctx = lookup_ioctx(ctx_id);
if (unlikely(!ctx)) {
pr_debug("EINVAL: invalid context id\n");
return -EINVAL;
}
if (nr > ctx->nr_events)
nr = ctx->nr_events;
if (nr > AIO_PLUG_THRESHOLD)
blk_start_plug(&plug);
for (i = 0; i < nr; i++) {
compat_uptr_t user_iocb;
if (unlikely(get_user(user_iocb, iocbpp + i))) {
ret = -EFAULT;
break;
}
ret = io_submit_one(ctx, compat_ptr(user_iocb), true);
if (ret)
break;
}
if (nr > AIO_PLUG_THRESHOLD)
blk_finish_plug(&plug);
percpu_ref_put(&ctx->users);
return i ? i : ret;
}
#endif
/* sys_io_cancel:
* Attempts to cancel an iocb previously passed to io_submit. If
* the operation is successfully cancelled, the resulting event is
* copied into the memory pointed to by result without being placed
* into the completion queue and 0 is returned. May fail with
* -EFAULT if any of the data structures pointed to are invalid.
* May fail with -EINVAL if aio_context specified by ctx_id is
* invalid. May fail with -EAGAIN if the iocb specified was not
* cancelled. Will fail with -ENOSYS if not implemented.
*/
SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
struct io_event __user *, result)
{
struct kioctx *ctx;
struct aio_kiocb *kiocb;
int ret = -EINVAL;
u32 key;
u64 obj = (u64)(unsigned long)iocb;
if (unlikely(get_user(key, &iocb->aio_key)))
return -EFAULT;
if (unlikely(key != KIOCB_KEY))
return -EINVAL;
ctx = lookup_ioctx(ctx_id);
if (unlikely(!ctx))
return -EINVAL;
spin_lock_irq(&ctx->ctx_lock);
/* TODO: use a hash or array, this sucks. */
list_for_each_entry(kiocb, &ctx->active_reqs, ki_list) {
if (kiocb->ki_res.obj == obj) {
ret = kiocb->ki_cancel(&kiocb->rw);
list_del_init(&kiocb->ki_list);
break;
}
}
spin_unlock_irq(&ctx->ctx_lock);
if (!ret) {
/*
* The result argument is no longer used - the io_event is
* always delivered via the ring buffer. -EINPROGRESS indicates
* cancellation is progress:
*/
ret = -EINPROGRESS;
}
percpu_ref_put(&ctx->users);
return ret;
}
static long do_io_getevents(aio_context_t ctx_id,
long min_nr,
long nr,
struct io_event __user *events,
struct timespec64 *ts)
{
ktime_t until = ts ? timespec64_to_ktime(*ts) : KTIME_MAX;
struct kioctx *ioctx = lookup_ioctx(ctx_id);
long ret = -EINVAL;
if (likely(ioctx)) {
if (likely(min_nr <= nr && min_nr >= 0))
ret = read_events(ioctx, min_nr, nr, events, until);
percpu_ref_put(&ioctx->users);
}
return ret;
}
/* io_getevents:
* Attempts to read at least min_nr events and up to nr events from
* the completion queue for the aio_context specified by ctx_id. If
* it succeeds, the number of read events is returned. May fail with
* -EINVAL if ctx_id is invalid, if min_nr is out of range, if nr is
* out of range, if timeout is out of range. May fail with -EFAULT
* if any of the memory specified is invalid. May return 0 or
* < min_nr if the timeout specified by timeout has elapsed
* before sufficient events are available, where timeout == NULL
* specifies an infinite timeout. Note that the timeout pointed to by
* timeout is relative. Will fail with -ENOSYS if not implemented.
*/
#ifdef CONFIG_64BIT
SYSCALL_DEFINE5(io_getevents, aio_context_t, ctx_id,
long, min_nr,
long, nr,
struct io_event __user *, events,
struct __kernel_timespec __user *, timeout)
{
struct timespec64 ts;
int ret;
if (timeout && unlikely(get_timespec64(&ts, timeout)))
return -EFAULT;
ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);
if (!ret && signal_pending(current))
ret = -EINTR;
return ret;
}
#endif
struct __aio_sigset {
const sigset_t __user *sigmask;
size_t sigsetsize;
};
SYSCALL_DEFINE6(io_pgetevents,
aio_context_t, ctx_id,
long, min_nr,
long, nr,
struct io_event __user *, events,
struct __kernel_timespec __user *, timeout,
const struct __aio_sigset __user *, usig)
{
struct __aio_sigset ksig = { NULL, };
struct timespec64 ts;
bool interrupted;
int ret;
if (timeout && unlikely(get_timespec64(&ts, timeout)))
return -EFAULT;
if (usig && copy_from_user(&ksig, usig, sizeof(ksig)))
return -EFAULT;
ret = set_user_sigmask(ksig.sigmask, ksig.sigsetsize);
if (ret)
return ret;
ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);
interrupted = signal_pending(current);
restore_saved_sigmask_unless(interrupted);
if (interrupted && !ret)
ret = -ERESTARTNOHAND;
return ret;
}
#if defined(CONFIG_COMPAT_32BIT_TIME) && !defined(CONFIG_64BIT)
SYSCALL_DEFINE6(io_pgetevents_time32,
aio_context_t, ctx_id,
long, min_nr,
long, nr,
struct io_event __user *, events,
struct old_timespec32 __user *, timeout,
const struct __aio_sigset __user *, usig)
{
struct __aio_sigset ksig = { NULL, };
struct timespec64 ts;
bool interrupted;
int ret;
if (timeout && unlikely(get_old_timespec32(&ts, timeout)))
return -EFAULT;
if (usig && copy_from_user(&ksig, usig, sizeof(ksig)))
return -EFAULT;
ret = set_user_sigmask(ksig.sigmask, ksig.sigsetsize);
if (ret)
return ret;
ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);
interrupted = signal_pending(current);
restore_saved_sigmask_unless(interrupted);
if (interrupted && !ret)
ret = -ERESTARTNOHAND;
return ret;
}
#endif
#if defined(CONFIG_COMPAT_32BIT_TIME)
SYSCALL_DEFINE5(io_getevents_time32, __u32, ctx_id,
__s32, min_nr,
__s32, nr,
struct io_event __user *, events,
struct old_timespec32 __user *, timeout)
{
struct timespec64 t;
int ret;
if (timeout && get_old_timespec32(&t, timeout))
return -EFAULT;
ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);
if (!ret && signal_pending(current))
ret = -EINTR;
return ret;
}
#endif
#ifdef CONFIG_COMPAT
struct __compat_aio_sigset {
compat_uptr_t sigmask;
compat_size_t sigsetsize;
};
#if defined(CONFIG_COMPAT_32BIT_TIME)
COMPAT_SYSCALL_DEFINE6(io_pgetevents,
compat_aio_context_t, ctx_id,
compat_long_t, min_nr,
compat_long_t, nr,
struct io_event __user *, events,
struct old_timespec32 __user *, timeout,
const struct __compat_aio_sigset __user *, usig)
{
struct __compat_aio_sigset ksig = { 0, };
struct timespec64 t;
bool interrupted;
int ret;
if (timeout && get_old_timespec32(&t, timeout))
return -EFAULT;
if (usig && copy_from_user(&ksig, usig, sizeof(ksig)))
return -EFAULT;
ret = set_compat_user_sigmask(compat_ptr(ksig.sigmask), ksig.sigsetsize);
if (ret)
return ret;
ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);
interrupted = signal_pending(current);
restore_saved_sigmask_unless(interrupted);
if (interrupted && !ret)
ret = -ERESTARTNOHAND;
return ret;
}
#endif
COMPAT_SYSCALL_DEFINE6(io_pgetevents_time64,
compat_aio_context_t, ctx_id,
compat_long_t, min_nr,
compat_long_t, nr,
struct io_event __user *, events,
struct __kernel_timespec __user *, timeout,
const struct __compat_aio_sigset __user *, usig)
{
struct __compat_aio_sigset ksig = { 0, };
struct timespec64 t;
bool interrupted;
int ret;
if (timeout && get_timespec64(&t, timeout))
return -EFAULT;
if (usig && copy_from_user(&ksig, usig, sizeof(ksig)))
return -EFAULT;
ret = set_compat_user_sigmask(compat_ptr(ksig.sigmask), ksig.sigsetsize);
if (ret)
return ret;
ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);
interrupted = signal_pending(current);
restore_saved_sigmask_unless(interrupted);
if (interrupted && !ret)
ret = -ERESTARTNOHAND;
return ret;
}
#endif
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