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eventfd: convert to f_op->read_iter()

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eventfd is using ->read() as it's file_operations read handler, but
this prevents passing in information about whether a given IO operation
is blocking or not. We can only use the file flags for that. To support
async (-EAGAIN/poll based) retries for io_uring, we need ->read_iter()
support. Convert eventfd to using ->read_iter().

With ->read_iter(), we can support IOCB_NOWAIT. Ensure the fd setup
is done such that we set file->f_mode with FMODE_NOWAIT.

[missing include added]

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Jens Axboe 2020-05-01 13:11:09 -06:00 committed by Al Viro
parent 8f3d9f3542
commit 12aceb89b0
1 changed files with 38 additions and 26 deletions
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58
fs/eventfd.c
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@ -23,6 +23,7 @@
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/idr.h>
#include <linux/uio.h>
DEFINE_PER_CPU(int, eventfd_wake_count);
@ -216,32 +217,32 @@ int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_entry_t *w
}
EXPORT_SYMBOL_GPL(eventfd_ctx_remove_wait_queue);
static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count,
loff_t *ppos)
static ssize_t eventfd_read(struct kiocb *iocb, struct iov_iter *to)
{
struct file *file = iocb->ki_filp;
struct eventfd_ctx *ctx = file->private_data;
ssize_t res;
__u64 ucnt = 0;
DECLARE_WAITQUEUE(wait, current);
if (count < sizeof(ucnt))
if (iov_iter_count(to) < sizeof(ucnt))
return -EINVAL;
spin_lock_irq(&ctx->wqh.lock);
res = -EAGAIN;
if (ctx->count > 0)
res = sizeof(ucnt);
else if (!(file->f_flags & O_NONBLOCK)) {
if (!ctx->count) {
if ((file->f_flags & O_NONBLOCK) ||
(iocb->ki_flags & IOCB_NOWAIT)) {
spin_unlock_irq(&ctx->wqh.lock);
return -EAGAIN;
}
__add_wait_queue(&ctx->wqh, &wait);
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);
if (ctx->count > 0) {
res = sizeof(ucnt);
if (ctx->count)
break;
}
if (signal_pending(current)) {
res = -ERESTARTSYS;
break;
__remove_wait_queue(&ctx->wqh, &wait);
__set_current_state(TASK_RUNNING);
spin_unlock_irq(&ctx->wqh.lock);
return -ERESTARTSYS;
}
spin_unlock_irq(&ctx->wqh.lock);
schedule();
@ -250,17 +251,14 @@ static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count,
__remove_wait_queue(&ctx->wqh, &wait);
__set_current_state(TASK_RUNNING);
}
if (likely(res > 0)) {
eventfd_ctx_do_read(ctx, &ucnt);
if (waitqueue_active(&ctx->wqh))
wake_up_locked_poll(&ctx->wqh, EPOLLOUT);
}
spin_unlock_irq(&ctx->wqh.lock);
if (res > 0 && put_user(ucnt, (__u64 __user *)buf))
if (unlikely(copy_to_iter(&ucnt, sizeof(ucnt), to) != sizeof(ucnt)))
return -EFAULT;
return res;
return sizeof(ucnt);
}
static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t count,
@ -329,7 +327,7 @@ static const struct file_operations eventfd_fops = {
#endif
.release = eventfd_release,
.poll = eventfd_poll,
.read = eventfd_read,
.read_iter = eventfd_read,
.write = eventfd_write,
.llseek = noop_llseek,
};
@ -406,6 +404,7 @@ EXPORT_SYMBOL_GPL(eventfd_ctx_fileget);
static int do_eventfd(unsigned int count, int flags)
{
struct eventfd_ctx *ctx;
struct file *file;
int fd;
/* Check the EFD_* constants for consistency. */
@ -425,11 +424,24 @@ static int do_eventfd(unsigned int count, int flags)
ctx->flags = flags;
ctx->id = ida_simple_get(&eventfd_ida, 0, 0, GFP_KERNEL);
fd = anon_inode_getfd("[eventfd]", &eventfd_fops, ctx,
O_RDWR | (flags & EFD_SHARED_FCNTL_FLAGS));
flags &= EFD_SHARED_FCNTL_FLAGS;
flags |= O_RDWR;
fd = get_unused_fd_flags(flags);
if (fd < 0)
eventfd_free_ctx(ctx);
goto err;
file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx, flags);
if (IS_ERR(file)) {
put_unused_fd(fd);
fd = PTR_ERR(file);
goto err;
}
file->f_mode |= FMODE_NOWAIT;
fd_install(fd, file);
return fd;
err:
eventfd_free_ctx(ctx);
return fd;
}