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Re: Feature Request for cp(1) utility, consider Btrfs ioctl clone range

From: Jeff liu
Subject: Re: Feature Request for cp(1) utility, consider Btrfs ioctl clone range support
Date: Fri, 19 Aug 2011 22:32:24 +0800

btw, I have posted a patch to make cp --reflink option works for OCFS2 too,

Is it acceptable?


> Hi Pádraig,
> Thanks for your comments!
>> On 08/10/2011 10:31 AM, Jeff Liu wrote:
>>> Hello,
>>> I just found a cool feature in Btrfs for cloning partially source file
>>> to the destination by specifying the desired offset and length to be copied.
>>> The call interface is something like below:
>>> struct btrfs_clone_range_args cr;
>>> cr.src_fd = source_desc;
>>> cr.src_offset = (uint64_t) offset;
>>> cr.src_length = (uint64_t) length;
>>> cr.dest_offset = (uint64_t) d_offset;
>>> ioctl(dest_fd, BTRFS_IOC_CLONE_RANGE, &args);
>>> cp(1) has already works with "reflink" supported for a long time, IMHO,
>>> this new feature could improve it to some extent.
>>> Is it acceptable to add a new option like
>>> "--reflink-range=src_offset,src_length,dst_offset" to clone partially
>>> source file?
>>> In this way, if reflink-range is triggered, cp(1) will try to parse the
>>> offset and length which are separated by comma,
>>> then try to clone src_length bytes from src_offset to the destination
>>> file started at dst_offset.
>>> if reflink-range failed, just let cp(1) fail with appropriate error info.
>>> I'd like to implement it if you guys think it does make sense. :-P.
>> IMHO I don't think this level of control is needed in `cp`.
> If you think it became useful to other coreutils stuff in the future, please 
> let me know, I would like to work on it.
> Regards,
> -Jeff
>> cheers,
>> Pádraig.

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