[PATCH v6 1/6] libfs: define simple_read_iter_from_buffer

[Dmitry Kasatkin]

Looks good to me.


On Tue, Aug 15, 2017 at 5:43 PM, Mimi Zohar <zohar at linux.vnet.ibm.com> wrote:
> In preparation for defining an integrity_read file operation
> method for efivarfs, define a simple_read_iter_from_buffer()
> function.
>
> (Based on Al's code as posted in thread.)
>
> Suggested-by: Al Viro <viro at zeniv.linux.org.uk>
> Signed-off-by: Mimi Zohar <zohar at linux.vnet.ibm.com>
> Cc: Matthew Garrett <mjg59 at srcf.ucam.org>
>
> ---
> Changelog v6:
> - defined as a separate patch
>
>  fs/libfs.c         | 32 ++++++++++++++++++++++++++++++++
>  include/linux/fs.h |  2 ++
>  2 files changed, 34 insertions(+)
>
> diff --git a/fs/libfs.c b/fs/libfs.c
> index 3aabe553fc45..b6e304c6828b 100644
> --- a/fs/libfs.c
> +++ b/fs/libfs.c
> @@ -16,6 +16,7 @@
>  #include <linux/exportfs.h>
>  #include <linux/writeback.h>
>  #include <linux/buffer_head.h> /* sync_mapping_buffers */
> +#include <linux/uio.h>
>
>  #include <linux/uaccess.h>
>
> @@ -676,6 +677,37 @@ ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
>  EXPORT_SYMBOL(simple_write_to_buffer);
>
>  /**
> + * simple_read_iter_from_buffer - copy data from the buffer to user space
> + * @iocb: struct containing the file, the current position and other info
> + * @to: the user space buffer to read to
> + * @from: the buffer to read from
> + * @available: the size of the buffer
> + *
> + * The simple_read_iter_from_buffer() function reads up to @available bytes
> + * from the current buffer into the user space buffer.
> + *
> + * On success, the current buffer offset is advanced by the number of bytes
> + * read, or a negative value is returned on error.
> + **/
> +ssize_t simple_read_iter_from_buffer(struct kiocb *iocb, struct iov_iter *to,
> +                                    const void *from, size_t available)
> +{
> +       loff_t pos = iocb->ki_pos;
> +       size_t ret;
> +
> +       if (pos < 0)
> +               return -EINVAL;
> +       if (pos >= available)
> +               return 0;
> +       ret = copy_to_iter(from + pos, available - pos, to);
> +       if (!ret && iov_iter_count(to))
> +               return -EFAULT;
> +       iocb->ki_pos = pos + ret;
> +       return ret;
> +}
> +EXPORT_SYMBOL(simple_read_iter_from_buffer);
> +
> +/**
>   * memory_read_from_buffer - copy data from the buffer
>   * @to: the kernel space buffer to read to
>   * @count: the maximum number of bytes to read
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 6e1fd5d21248..fdec9b763b54 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -3097,6 +3097,8 @@ extern void simple_release_fs(struct vfsmount **mount, int *count);
>
>  extern ssize_t simple_read_from_buffer(void __user *to, size_t count,
>                         loff_t *ppos, const void *from, size_t available);
> +extern ssize_t simple_read_iter_from_buffer(struct kiocb *iocb,
> +               struct iov_iter *to, const void *from, size_t available);
>  extern ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
>                 const void __user *from, size_t count);
>
> --
> 2.7.4
>
> --
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-- 
Thanks,
Dmitry
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