linux-kernel - Re: [PATCH] fuse: Add support for fuse stacked I/O

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Message-ID: <56A0171C.6050108@codeaurora.org>
Date:	Wed, 20 Jan 2016 15:24:12 -0800
From:	Nikhilesh Reddy <reddyn@...eaurora.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Andy Lutomirski <luto@...capital.net>,
	Nikolaus Rath <nikolaus@...h.org>,
	fuse-devel <fuse-devel@...ts.sourceforge.net>,
	Al Viro <viro@...iv.linux.org.uk>,
	Greg KH <gregkh@...uxfoundation.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>, Jan Kara <jack@...e.cz>,
	Theodore Ts'o <tytso@....edu>, sven.utcke@....de,
	Miklos Szeredi <miklos@...redi.hu>,
	Richard Weinberger <richard@....at>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Antonio SJ Musumeci <trapexit@...wn.link>
Subject: Re: [PATCH] fuse: Add support for fuse stacked I/O

On 01/18/2016 06:57 PM, Nikhilesh Reddy wrote:
> On 01/15/2016 01:53 PM, Linus Torvalds wrote:
>> On Fri, Jan 15, 2016 at 1:46 PM, Andy Lutomirski <luto@...capital.net>
>> wrote:
>>
>>> If mmap sets vm_file to the underlying thing, wouldn't CRIU and
>>> anything else that uses map_files get confused?  Or did you have
>>> something else in mind?
>>
>> Why would they care?
>>
>> Also, I don't think you actually need to change vm_file - we have this
>> whole notion of "inode->i_data" vs "inode->i_mapping".
>>
>> So I think you could set the "i_mapping" of the fuse inode to be the
>> i_mapping of the passed-through-to inode, and it should just work.
>>
>> And no, I didn't look into this very deeply, and maybe there is some
>> annoying detail that would make that not work well. But that's part of
>> the whole point of the i_mapping indirection: so that you can share
>> the page cache when you have two separate anchor points. I think coda
>> uses it for the local caching, and block devices use it to not have
>> mapping aliases between different inodex that all are the same block
>> device.
>>
>>                   Linus
>>
>
> Hi
>
> Thanks for your support.
>
> I am looking  into adding the mmap by change the i_mmaping but seems to
> be getting stuck for some stress tests.
>
> Once i get that debugged and working i will definitely send out a new
> patch with that functionality.
>
> ( Sending it as a second patch will help make it easier to go through
> the legal redtape and procedures i am forced to follow).
>
> For now i am going to update the current patch and call it "passthrough"
> as you suggested and also update the commit message giving  a clearer
> explanation of the motivation.
>
> Once i get it tested I can send it out for consideration and review
>
> Please do let me know if you have any questions or concerns on this and
> i will try my best to address them all.
>
>
I have just sent out the latest version of the patch in the email with 
the subject
[PATCH v3] fuse: Add support for passthrough read/write

Please do let me know if you have any questions or concerns on this and
i will try my best to address them all.

-- 
Thanks
Nikhilesh Reddy

Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.