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Merge branch 'work.aio' of git://git.kernel.org/pub/scm/linux/kernel/…
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…git/viro/vfs

Pull vfs aio updates from Al Viro:
 "Christoph's aio poll, saner this time around.

  This time it's pretty much local to fs/aio.c. Hopefully race-free..."

* 'work.aio' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  aio: allow direct aio poll comletions for keyed wakeups
  aio: implement IOCB_CMD_POLL
  aio: add a iocb refcount
  timerfd: add support for keyed wakeups
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@torvalds
torvalds committed Aug 14, 2018
2 parents 4d2a073 + e8693bc commit f2be269
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Showing 3 changed files with 209 additions and 11 deletions.
208 changes: 204 additions & 4 deletions fs/aio.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
* 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.
*/
Expand All @@ -18,6 +19,7 @@
#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>
Expand Down Expand Up @@ -164,10 +166,21 @@ struct fsync_iocb {
bool datasync;
};

struct poll_iocb {
struct file *file;
struct wait_queue_head *head;
__poll_t events;
bool woken;
bool cancelled;
struct wait_queue_entry wait;
struct work_struct work;
};

struct aio_kiocb {
union {
struct kiocb rw;
struct fsync_iocb fsync;
struct poll_iocb poll;
};

struct kioctx *ki_ctx;
Expand All @@ -178,6 +191,7 @@ struct aio_kiocb {

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,
Expand Down Expand Up @@ -999,6 +1013,7 @@ static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx)

percpu_ref_get(&ctx->reqs);
INIT_LIST_HEAD(&req->ki_list);
refcount_set(&req->ki_refcnt, 0);
req->ki_ctx = ctx;
return req;
out_put:
Expand Down Expand Up @@ -1033,6 +1048,15 @@ static struct kioctx *lookup_ioctx(unsigned long ctx_id)
return ret;
}

static inline void iocb_put(struct aio_kiocb *iocb)
{
if (refcount_read(&iocb->ki_refcnt) == 0 ||
refcount_dec_and_test(&iocb->ki_refcnt)) {
percpu_ref_put(&iocb->ki_ctx->reqs);
kmem_cache_free(kiocb_cachep, iocb);
}
}

/* aio_complete
* Called when the io request on the given iocb is complete.
*/
Expand Down Expand Up @@ -1102,8 +1126,6 @@ static void aio_complete(struct aio_kiocb *iocb, long res, long res2)
eventfd_ctx_put(iocb->ki_eventfd);
}

kmem_cache_free(kiocb_cachep, iocb);

/*
* We have to order our ring_info tail store above and test
* of the wait list below outside the wait lock. This is
Expand All @@ -1114,8 +1136,7 @@ static void aio_complete(struct aio_kiocb *iocb, long res, long res2)

if (waitqueue_active(&ctx->wait))
wake_up(&ctx->wait);

percpu_ref_put(&ctx->reqs);
iocb_put(iocb);
}

/* aio_read_events_ring
Expand Down Expand Up @@ -1576,6 +1597,182 @@ static int aio_fsync(struct fsync_iocb *req, struct iocb *iocb, bool datasync)
return 0;
}

static inline void aio_poll_complete(struct aio_kiocb *iocb, __poll_t mask)
{
struct file *file = iocb->poll.file;

aio_complete(iocb, mangle_poll(mask), 0);
fput(file);
}

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 (!mask && !READ_ONCE(req->cancelled)) {
add_wait_queue(req->head, &req->wait);
spin_unlock_irq(&ctx->ctx_lock);
return;
}
list_del_init(&iocb->ki_list);
spin_unlock_irq(&ctx->ctx_lock);

aio_poll_complete(iocb, mask);
}

/* 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;

spin_lock(&req->head->lock);
WRITE_ONCE(req->cancelled, true);
if (!list_empty(&req->wait.entry)) {
list_del_init(&req->wait.entry);
schedule_work(&aiocb->poll.work);
}
spin_unlock(&req->head->lock);

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);

req->woken = true;

/* for instances that support it check for an event match first: */
if (mask) {
if (!(mask & req->events))
return 0;

/* try to complete the iocb inline if we can: */
if (spin_trylock(&iocb->ki_ctx->ctx_lock)) {
list_del(&iocb->ki_list);
spin_unlock(&iocb->ki_ctx->ctx_lock);

list_del_init(&req->wait.entry);
aio_poll_complete(iocb, mask);
return 1;
}
}

list_del_init(&req->wait.entry);
schedule_work(&req->work);
return 1;
}

struct aio_poll_table {
struct poll_table_struct pt;
struct aio_kiocb *iocb;
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->iocb->poll.head)) {
pt->error = -EINVAL;
return;
}

pt->error = 0;
pt->iocb->poll.head = head;
add_wait_queue(head, &pt->iocb->poll.wait);
}

static ssize_t aio_poll(struct aio_kiocb *aiocb, struct iocb *iocb)
{
struct kioctx *ctx = aiocb->ki_ctx;
struct poll_iocb *req = &aiocb->poll;
struct aio_poll_table apt;
__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->file = fget(iocb->aio_fildes);
if (unlikely(!req->file))
return -EBADF;

apt.pt._qproc = aio_poll_queue_proc;
apt.pt._key = req->events;
apt.iocb = aiocb;
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);

/* one for removal from waitqueue, one for this function */
refcount_set(&aiocb->ki_refcnt, 2);

mask = vfs_poll(req->file, &apt.pt) & req->events;
if (unlikely(!req->head)) {
/* we did not manage to set up a waitqueue, done */
goto out;
}

spin_lock_irq(&ctx->ctx_lock);
spin_lock(&req->head->lock);
if (req->woken) {
/* wake_up context handles the rest */
mask = 0;
apt.error = 0;
} else if (mask || apt.error) {
/* if we get an error or a mask we are done */
WARN_ON_ONCE(list_empty(&req->wait.entry));
list_del_init(&req->wait.entry);
} else {
/* actually waiting for an event */
list_add_tail(&aiocb->ki_list, &ctx->active_reqs);
aiocb->ki_cancel = aio_poll_cancel;
}
spin_unlock(&req->head->lock);
spin_unlock_irq(&ctx->ctx_lock);

out:
if (unlikely(apt.error)) {
fput(req->file);
return apt.error;
}

if (mask)
aio_poll_complete(aiocb, mask);
iocb_put(aiocb);
return 0;
}

static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
bool compat)
{
Expand Down Expand Up @@ -1649,6 +1846,9 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
case IOCB_CMD_FDSYNC:
ret = aio_fsync(&req->fsync, &iocb, true);
break;
case IOCB_CMD_POLL:
ret = aio_poll(req, &iocb);
break;
default:
pr_debug("invalid aio operation %d\n", iocb.aio_lio_opcode);
ret = -EINVAL;
Expand Down
6 changes: 3 additions & 3 deletions fs/timerfd.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -66,7 +66,7 @@ static void timerfd_triggered(struct timerfd_ctx *ctx)
spin_lock_irqsave(&ctx->wqh.lock, flags);
ctx->expired = 1;
ctx->ticks++;
wake_up_locked(&ctx->wqh);
wake_up_locked_poll(&ctx->wqh, EPOLLIN);
spin_unlock_irqrestore(&ctx->wqh.lock, flags);
}

Expand Down Expand Up @@ -107,7 +107,7 @@ void timerfd_clock_was_set(void)
if (ctx->moffs != moffs) {
ctx->moffs = KTIME_MAX;
ctx->ticks++;
wake_up_locked(&ctx->wqh);
wake_up_locked_poll(&ctx->wqh, EPOLLIN);
}
spin_unlock_irqrestore(&ctx->wqh.lock, flags);
}
Expand Down Expand Up @@ -345,7 +345,7 @@ static long timerfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg
spin_lock_irq(&ctx->wqh.lock);
if (!timerfd_canceled(ctx)) {
ctx->ticks = ticks;
wake_up_locked(&ctx->wqh);
wake_up_locked_poll(&ctx->wqh, EPOLLIN);
} else
ret = -ECANCELED;
spin_unlock_irq(&ctx->wqh.lock);
Expand Down
6 changes: 2 additions & 4 deletions include/uapi/linux/aio_abi.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -38,10 +38,8 @@ enum {
IOCB_CMD_PWRITE = 1,
IOCB_CMD_FSYNC = 2,
IOCB_CMD_FDSYNC = 3,
/* These two are experimental.
* IOCB_CMD_PREADX = 4,
* IOCB_CMD_POLL = 5,
*/
/* 4 was the experimental IOCB_CMD_PREADX */
IOCB_CMD_POLL = 5,
IOCB_CMD_NOOP = 6,
IOCB_CMD_PREADV = 7,
IOCB_CMD_PWRITEV = 8,
Expand Down

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