Re: [PATCH] fideduperange.2: fix the discussion of maximum sizes

[Omar Sandoval <osandov@osandov.com>]

On Tue, Nov 22, 2016 at 08:22:22PM -0800, Darrick J. Wong wrote:
> Fix the discussion of the limitations on the dest_count and src_length
> parameters to the fideduperange ioctl to reflect what's actually in the
> kernel.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  man2/ioctl_fideduperange.2 |   12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/man2/ioctl_fideduperange.2 b/man2/ioctl_fideduperange.2
> index 2112d10..59f0ea9 100644
> --- a/man2/ioctl_fideduperange.2
> +++ b/man2/ioctl_fideduperange.2
> @@ -95,7 +95,7 @@ struct file_dedupe_range_info {
>  .in
>  
>  Each deduplication operation targets
> -.IR length
> +.IR src_length
>  bytes in file descriptor
>  .IR dest_fd
>  at offset
> @@ -108,8 +108,14 @@ During the call,
>  must be open for reading and
>  .IR dest_fd
>  must be open for writing.
> -For any call to this ioctl, there may not be more than 65,536
> -requests attached; each request may not exceed 16MiB.
> +The combined size of the struct
> +.IR file_dedupe_range
> +and the struct
> +.IR file_dedupe_range_info
> +array must not exceed the system page size.
> +The maximum size of
> +.IR src_length
> +is filesystem dependent and is typically 16MiB.
>  By convention, the storage used by
>  .IR src_fd
>  is mapped into

Might be worth it to clarify that the file_dedupe_range_info limit is a
hard limit that will result in an error if exceeded and that the
src_length limit is silently enforced. These semantics suck...

-- 
Omar