Adding Maxim Patlasov, who did the AIO mode in fuse.
On Tue, 2015-01-27 at 18:55 +0100, Christoph Hellwig wrote:
> The AIO interface is fairly complex because it tries to allow
> filesystems to always work async and then wakeup a synchronous
> caller through aio_complete. It turns out that basically no one
> does this to avoid the complexity and context switches, with the
> solve exception of fuse, so remove that possibility to simplify
> the code.
>
> XXX: fix up fuse.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> drivers/usb/gadget/function/f_fs.c | 4 ++--
> fs/aio.c | 24 +-----------------------
> fs/ecryptfs/file.c | 6 ------
> fs/fuse/file.c | 7 +++++--
> fs/read_write.c | 26 ++++++++------------------
> include/linux/aio.h | 4 ----
> net/socket.c | 9 +++------
> 7 files changed, 19 insertions(+), 61 deletions(-)
>
> diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> index 63314ed..debd78b 100644
> --- a/drivers/usb/gadget/function/f_fs.c
> +++ b/drivers/usb/gadget/function/f_fs.c
> @@ -969,7 +969,7 @@ static ssize_t ffs_epfile_aio_write(struct kiocb *kiocb,
> if (unlikely(!io_data))
> return -ENOMEM;
>
> - io_data->aio = true;
> + io_data->aio = !is_sync_kiocb(kiocb);
> io_data->read = false;
> io_data->kiocb = kiocb;
> io_data->iovec = iovec;
> @@ -1005,7 +1005,7 @@ static ssize_t ffs_epfile_aio_read(struct kiocb *kiocb,
> return -ENOMEM;
> }
>
> - io_data->aio = true;
> + io_data->aio = !is_sync_kiocb(kiocb);
> io_data->read = true;
> io_data->kiocb = kiocb;
> io_data->iovec = iovec_copy;
> diff --git a/fs/aio.c b/fs/aio.c
> index 1b7893e..0ee25d6 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -791,22 +791,6 @@ static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx,
> return 0;
> }
>
> -/* wait_on_sync_kiocb:
> - * Waits on the given sync kiocb to complete.
> - */
> -ssize_t wait_on_sync_kiocb(struct kiocb *req)
> -{
> - while (!req->ki_ctx) {
> - set_current_state(TASK_UNINTERRUPTIBLE);
> - if (req->ki_ctx)
> - break;
> - io_schedule();
> - }
> - __set_current_state(TASK_RUNNING);
> - return req->ki_user_data;
> -}
> -EXPORT_SYMBOL(wait_on_sync_kiocb);
> -
> /*
> * 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
> @@ -1038,13 +1022,7 @@ void aio_complete(struct kiocb *iocb, long res, long res2)
> * ref, no other paths have a way to get another ref
> * - the sync task helpfully left a reference to itself in the iocb
> */
> - if (is_sync_kiocb(iocb)) {
> - iocb->ki_user_data = res;
> - smp_wmb();
> - iocb->ki_ctx = ERR_PTR(-EXDEV);
> - wake_up_process(iocb->ki_obj.tsk);
> - return;
> - }
> + BUG_ON(is_sync_kiocb(iocb));
>
> if (iocb->ki_list.next) {
> unsigned long flags;
> diff --git a/fs/ecryptfs/file.c b/fs/ecryptfs/file.c
> index 6f4e659..a36da88 100644
> --- a/fs/ecryptfs/file.c
> +++ b/fs/ecryptfs/file.c
> @@ -52,12 +52,6 @@ static ssize_t ecryptfs_read_update_atime(struct kiocb *iocb,
> struct file *file = iocb->ki_filp;
>
> rc = generic_file_read_iter(iocb, to);
> - /*
> - * Even though this is a async interface, we need to wait
> - * for IO to finish to update atime
> - */
> - if (-EIOCBQUEUED == rc)
> - rc = wait_on_sync_kiocb(iocb);
> if (rc >= 0) {
> path = ecryptfs_dentry_to_lower_path(file->f_path.dentry);
> touch_atime(path);
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 760b2c5..9c27312 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -2841,8 +2841,10 @@ fuse_direct_IO(int rw, struct kiocb *iocb, struct iov_iter *iter,
> /*
> * By default, we want to optimize all I/Os with async request
> * submission to the client filesystem if supported.
> + *
> + * XXX: need to add back support for this mode..
> */
> - io->async = async_dio;
> + io->async = async_dio && !is_sync_kiocb(iocb);
> io->iocb = iocb;
>
> /*
> @@ -2865,7 +2867,8 @@ fuse_direct_IO(int rw, struct kiocb *iocb, struct iov_iter *iter,
> if (!is_sync_kiocb(iocb))
> return -EIOCBQUEUED;
>
> - ret = wait_on_sync_kiocb(iocb);
> + // XXX: need fuse specific replacement
> +// ret = wait_on_sync_kiocb(iocb);
> } else {
> kfree(io);
> }
> diff --git a/fs/read_write.c b/fs/read_write.c
> index ab4f26a..adab608 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -347,9 +347,7 @@ ssize_t vfs_iter_read(struct file *file, struct iov_iter *iter, loff_t *ppos)
>
> iter->type |= READ;
> ret = file->f_op->read_iter(&kiocb, iter);
> - if (ret == -EIOCBQUEUED)
> - ret = wait_on_sync_kiocb(&kiocb);
> -
> + BUG_ON(ret == -EIOCBQUEUED);
> if (ret > 0)
> *ppos = kiocb.ki_pos;
> return ret;
> @@ -370,9 +368,7 @@ ssize_t vfs_iter_write(struct file *file, struct iov_iter *iter, loff_t *ppos)
>
> iter->type |= WRITE;
> ret = file->f_op->write_iter(&kiocb, iter);
> - if (ret == -EIOCBQUEUED)
> - ret = wait_on_sync_kiocb(&kiocb);
> -
> + BUG_ON(ret == -EIOCBQUEUED);
> if (ret > 0)
> *ppos = kiocb.ki_pos;
> return ret;
> @@ -429,8 +425,7 @@ ssize_t do_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *pp
> kiocb.ki_nbytes = len;
>
> ret = filp->f_op->aio_read(&kiocb, &iov, 1, kiocb.ki_pos);
> - if (-EIOCBQUEUED == ret)
> - ret = wait_on_sync_kiocb(&kiocb);
> + BUG_ON(ret == -EIOCBQUEUED);
> *ppos = kiocb.ki_pos;
> return ret;
> }
> @@ -450,8 +445,7 @@ ssize_t new_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *p
> iov_iter_init(&iter, READ, &iov, 1, len);
>
> ret = filp->f_op->read_iter(&kiocb, &iter);
> - if (-EIOCBQUEUED == ret)
> - ret = wait_on_sync_kiocb(&kiocb);
> + BUG_ON(ret == -EIOCBQUEUED);
> *ppos = kiocb.ki_pos;
> return ret;
> }
> @@ -513,8 +507,7 @@ ssize_t do_sync_write(struct file *filp, const char __user *buf, size_t len, lof
> kiocb.ki_nbytes = len;
>
> ret = filp->f_op->aio_write(&kiocb, &iov, 1, kiocb.ki_pos);
> - if (-EIOCBQUEUED == ret)
> - ret = wait_on_sync_kiocb(&kiocb);
> + BUG_ON(ret == -EIOCBQUEUED);
> *ppos = kiocb.ki_pos;
> return ret;
> }
> @@ -534,8 +527,7 @@ ssize_t new_sync_write(struct file *filp, const char __user *buf, size_t len, lo
> iov_iter_init(&iter, WRITE, &iov, 1, len);
>
> ret = filp->f_op->write_iter(&kiocb, &iter);
> - if (-EIOCBQUEUED == ret)
> - ret = wait_on_sync_kiocb(&kiocb);
> + BUG_ON(ret == -EIOCBQUEUED);
> *ppos = kiocb.ki_pos;
> return ret;
> }
> @@ -723,8 +715,7 @@ static ssize_t do_iter_readv_writev(struct file *filp, int rw, const struct iove
>
> iov_iter_init(&iter, rw, iov, nr_segs, len);
> ret = fn(&kiocb, &iter);
> - if (ret == -EIOCBQUEUED)
> - ret = wait_on_sync_kiocb(&kiocb);
> + BUG_ON(ret == -EIOCBQUEUED);
> *ppos = kiocb.ki_pos;
> return ret;
> }
> @@ -740,8 +731,7 @@ static ssize_t do_sync_readv_writev(struct file *filp, const struct iovec *iov,
> kiocb.ki_nbytes = len;
>
> ret = fn(&kiocb, iov, nr_segs, kiocb.ki_pos);
> - if (ret == -EIOCBQUEUED)
> - ret = wait_on_sync_kiocb(&kiocb);
> + BUG_ON(ret == -EIOCBQUEUED);
> *ppos = kiocb.ki_pos;
> return ret;
> }
> diff --git a/include/linux/aio.h b/include/linux/aio.h
> index d9c92da..57c86c0 100644
> --- a/include/linux/aio.h
> +++ b/include/linux/aio.h
> @@ -37,7 +37,6 @@ struct kiocb {
>
> union {
> void __user *user;
> - struct task_struct *tsk;
> } ki_obj;
>
> __u64 ki_user_data; /* user's data for completion */
> @@ -64,13 +63,11 @@ static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
> *kiocb = (struct kiocb) {
> .ki_ctx = NULL,
> .ki_filp = filp,
> - .ki_obj.tsk = current,
> };
> }
>
> /* prototypes */
> #ifdef CONFIG_AIO
> -extern ssize_t wait_on_sync_kiocb(struct kiocb *iocb);
> extern void aio_complete(struct kiocb *iocb, long res, long res2);
> struct mm_struct;
> extern void exit_aio(struct mm_struct *mm);
> @@ -78,7 +75,6 @@ extern long do_io_submit(aio_context_t ctx_id, long nr,
> struct iocb __user *__user *iocbpp, bool compat);
> void kiocb_set_cancel_fn(struct kiocb *req, kiocb_cancel_fn *cancel);
> #else
> -static inline ssize_t wait_on_sync_kiocb(struct kiocb *iocb) { return 0; }
> static inline void aio_complete(struct kiocb *iocb, long res, long res2) { }
> struct mm_struct;
> static inline void exit_aio(struct mm_struct *mm) { }
> diff --git a/net/socket.c b/net/socket.c
> index a2c33a4..4032931 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -642,8 +642,7 @@ static int do_sock_sendmsg(struct socket *sock, struct msghdr *msg,
> iocb.private = &siocb;
> ret = nosec ? __sock_sendmsg_nosec(&iocb, sock, msg, size) :
> __sock_sendmsg(&iocb, sock, msg, size);
> - if (-EIOCBQUEUED == ret)
> - ret = wait_on_sync_kiocb(&iocb);
> + BUG_ON(-EIOCBQUEUED == ret);
> return ret;
> }
>
> @@ -785,8 +784,7 @@ int sock_recvmsg(struct socket *sock, struct msghdr *msg,
> init_sync_kiocb(&iocb, NULL);
> iocb.private = &siocb;
> ret = __sock_recvmsg(&iocb, sock, msg, size, flags);
> - if (-EIOCBQUEUED == ret)
> - ret = wait_on_sync_kiocb(&iocb);
> + BUG_ON(-EIOCBQUEUED == ret);
> return ret;
> }
> EXPORT_SYMBOL(sock_recvmsg);
> @@ -801,8 +799,7 @@ static int sock_recvmsg_nosec(struct socket *sock, struct msghdr *msg,
> init_sync_kiocb(&iocb, NULL);
> iocb.private = &siocb;
> ret = __sock_recvmsg_nosec(&iocb, sock, msg, size, flags);
> - if (-EIOCBQUEUED == ret)
> - ret = wait_on_sync_kiocb(&iocb);
> + BUG_ON(-EIOCBQUEUED == ret);
> return ret;
> }
>
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