Re: Re: Warning on memory offline (and possible in usual migration?)

[Badari Pulavarty <pbadari@gmail.com>]

On Thu, 2008-05-01 at 08:29 +0900, kamezawa.hiroyu@jp.fujitsu.com wrote:
> >
> >One issue that I am still not clear on is (in particular for memory 
> >offline) is how exactly to determine if a page is under read I/O. I 
> >initially thought simply checking for PageUptodate would do the trick.
> >
> All troublesome case I found was "write". In my understanding,
> at generic bufferted file write, xxx_write_begin() -> write -> xxx_write_end()
>  sequence is used. xxx_write_begin locks a page and xxx_write_end unlock it. 
> (and xxx_write_end() set a page to be Uptodate in usual case.)
> So,it seems we can depend on that a page is locked or not.

You can wait for PG_writeback to be cleared to wait for IO to finish.

Thanks,
Badari

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