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SubjectRe: [PATCH] fuse: Add support for fuse stacked I/O
On 01/15/2016 01:53 PM, Linus Torvalds wrote:
> On Fri, Jan 15, 2016 at 1:46 PM, Andy Lutomirski <> 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


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.

Nikhilesh Reddy

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

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