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    SubjectRe: [PATCH V8 15/33] aio: add aio support for iov_iter arguments
    Sorry for the lack of response. Getting back to this.

    On 08/21/2013 08:55 AM, Benjamin LaHaise wrote:
    > On Thu, Jul 25, 2013 at 12:50:41PM -0500, Dave Kleikamp wrote:
    >> This adds iocb cmds which specify that memory is held in iov_iter
    >> structures. This lets kernel callers specify memory that can be
    >> expressed in an iov_iter, which includes pages in bio_vec arrays.
    >>
    >> Only kernel callers can provide an iov_iter so it doesn't make a lot of
    >> sense to expose the IOCB_CMD values for this as part of the user space
    >> ABI.
    >
    > I don't think adding the IOCB_CMD_{READ,WRITE}_ITER operations to
    > include/uapi/linux/aio_abi.h is the right thing to do here -- they're
    > never going to be used by userland, and care certainly not part of the
    > abi we're presenting to userland. I'd suggest moving these opcodes to
    > include/linux/aio.h.

    Agreed.

    > Also, if you make the values > 16 bits, userland
    > will never be able to pass them in inadvertently (although things look
    > okay if that does happen at present).

    I'd have to change the declaration of ki_opcode to an int. This
    shouldn't be a problem since it'll be padded to a long anyway.

    >
    > -ben
    >
    >> But kernel callers should also be able to perform the usual aio
    >> operations which suggests using the the existing operation namespace and
    >> support code.
    >>
    >> Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
    >> Cc: Zach Brown <zab@zabbo.net>
    >> ---
    >> fs/aio.c | 67 ++++++++++++++++++++++++++++++++++++++++++++
    >> include/linux/aio.h | 3 ++
    >> include/uapi/linux/aio_abi.h | 2 ++
    >> 3 files changed, 72 insertions(+)
    >>
    >> diff --git a/fs/aio.c b/fs/aio.c
    >> index c65ba13..0da82c0 100644
    >> --- a/fs/aio.c
    >> +++ b/fs/aio.c
    >> @@ -991,6 +991,48 @@ static ssize_t aio_setup_single_vector(int rw, struct kiocb *kiocb)
    >> return 0;
    >> }
    >>
    >> +static ssize_t aio_read_iter(struct kiocb *iocb)
    >> +{
    >> + struct file *file = iocb->ki_filp;
    >> + ssize_t ret;
    >> +
    >> + if (unlikely(!is_kernel_kiocb(iocb)))
    >> + return -EINVAL;
    >> +
    >> + if (unlikely(!(file->f_mode & FMODE_READ)))
    >> + return -EBADF;
    >> +
    >> + ret = security_file_permission(file, MAY_READ);
    >> + if (unlikely(ret))
    >> + return ret;
    >> +
    >> + if (!file->f_op->read_iter)
    >> + return -EINVAL;
    >> +
    >> + return file->f_op->read_iter(iocb, iocb->ki_iter, iocb->ki_pos);
    >> +}
    >> +
    >> +static ssize_t aio_write_iter(struct kiocb *iocb)
    >> +{
    >> + struct file *file = iocb->ki_filp;
    >> + ssize_t ret;
    >> +
    >> + if (unlikely(!is_kernel_kiocb(iocb)))
    >> + return -EINVAL;
    >> +
    >> + if (unlikely(!(file->f_mode & FMODE_WRITE)))
    >> + return -EBADF;
    >> +
    >> + ret = security_file_permission(file, MAY_WRITE);
    >> + if (unlikely(ret))
    >> + return ret;
    >> +
    >> + if (!file->f_op->write_iter)
    >> + return -EINVAL;
    >> +
    >> + return file->f_op->write_iter(iocb, iocb->ki_iter, iocb->ki_pos);
    >> +}
    >> +
    >> /*
    >> * aio_setup_iocb:
    >> * Performs the initial checks and aio retry method
    >> @@ -1042,6 +1084,14 @@ rw_common:
    >> ret = aio_rw_vect_retry(req, rw, rw_op);
    >> break;
    >>
    >> + case IOCB_CMD_READ_ITER:
    >> + ret = aio_read_iter(req);
    >> + break;
    >> +
    >> + case IOCB_CMD_WRITE_ITER:
    >> + ret = aio_write_iter(req);
    >> + break;
    >> +
    >> case IOCB_CMD_FDSYNC:
    >> if (!file->f_op->aio_fsync)
    >> return -EINVAL;
    >> @@ -1116,6 +1166,23 @@ void aio_kernel_init_rw(struct kiocb *iocb, struct file *filp,
    >> }
    >> EXPORT_SYMBOL_GPL(aio_kernel_init_rw);
    >>
    >> +/*
    >> + * The iter count must be set before calling here. Some filesystems uses
    >> + * iocb->ki_left as an indicator of the size of an IO.
    >> + */
    >> +void aio_kernel_init_iter(struct kiocb *iocb, struct file *filp,
    >> + unsigned short op, struct iov_iter *iter, loff_t off)
    >> +{
    >> + iocb->ki_filp = filp;
    >> + iocb->ki_iter = iter;
    >> + iocb->ki_opcode = op;
    >> + iocb->ki_pos = off;
    >> + iocb->ki_nbytes = iov_iter_count(iter);
    >> + iocb->ki_left = iocb->ki_nbytes;
    >> + iocb->ki_ctx = (void *)-1;
    >> +}
    >> +EXPORT_SYMBOL_GPL(aio_kernel_init_iter);
    >> +
    >> void aio_kernel_init_callback(struct kiocb *iocb,
    >> void (*complete)(u64 user_data, long res),
    >> u64 user_data)
    >> diff --git a/include/linux/aio.h b/include/linux/aio.h
    >> index 014a75d..64d059d 100644
    >> --- a/include/linux/aio.h
    >> +++ b/include/linux/aio.h
    >> @@ -66,6 +66,7 @@ struct kiocb {
    >> * this is the underlying eventfd context to deliver events to.
    >> */
    >> struct eventfd_ctx *ki_eventfd;
    >> + struct iov_iter *ki_iter;
    >> };
    >>
    >> static inline bool is_sync_kiocb(struct kiocb *kiocb)
    >> @@ -102,6 +103,8 @@ struct kiocb *aio_kernel_alloc(gfp_t gfp);
    >> void aio_kernel_free(struct kiocb *iocb);
    >> void aio_kernel_init_rw(struct kiocb *iocb, struct file *filp,
    >> unsigned short op, void *ptr, size_t nr, loff_t off);
    >> +void aio_kernel_init_iter(struct kiocb *iocb, struct file *filp,
    >> + unsigned short op, struct iov_iter *iter, loff_t off);
    >> void aio_kernel_init_callback(struct kiocb *iocb,
    >> void (*complete)(u64 user_data, long res),
    >> u64 user_data);
    >> diff --git a/include/uapi/linux/aio_abi.h b/include/uapi/linux/aio_abi.h
    >> index bb2554f..22ce4bd 100644
    >> --- a/include/uapi/linux/aio_abi.h
    >> +++ b/include/uapi/linux/aio_abi.h
    >> @@ -44,6 +44,8 @@ enum {
    >> IOCB_CMD_NOOP = 6,
    >> IOCB_CMD_PREADV = 7,
    >> IOCB_CMD_PWRITEV = 8,
    >> + IOCB_CMD_READ_ITER = 9,
    >> + IOCB_CMD_WRITE_ITER = 10,
    >> };
    >>
    >> /*
    >> --
    >> 1.8.3.4


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