[FYI] tux3: Core changes

Rik van Riel riel at redhat.com
Wed May 20 12:53:16 PDT 2015

On 05/20/2015 12:22 PM, Daniel Phillips wrote:
> On 05/20/2015 07:44 AM, Jan Kara wrote:
>> On Tue 19-05-15 13:33:31, David Lang wrote:

>>   Yeah, that's what I meant. If you create a function which manipulates
>> page cache, you better make it work with other functions manipulating page
>> cache. Otherwise it's a landmine waiting to be tripped by some unsuspecting
>> developer. Sure you can document all the conditions under which the
>> function is safe to use but a function that has several paragraphs in front
>> of it explaning when it is safe to use isn't very good API...
> Violent agreement, of course. To put it in concrete terms, each of
> the page fork support functions must be examined and determined
> sane. They are:
>  * cow_replace_page_cache
>  * cow_delete_from_page_cache
>  * cow_clone_page
>  * page_cow_one
>  * page_cow_file
> Would it be useful to drill down into those, starting from the top
> of the list?

How do these interact with other page cache functions, like
find_get_page() ?

How does tux3 prevent a user of find_get_page() from reading from
or writing into the pre-COW page, instead of the current page?

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