Re: [PATCH v3 1/4] fs: kiocb: introduce IOCB_DONT_DIRTY_PAGE flag for direct IO

[Christoph Hellwig]

On Thu, May 07, 2015 at 08:12:31PM +0800, Ming Lei wrote:
> In case of loop, it is quite specific about dirtying READ pages in
> direct IO because fs over loop has considered dirtying these pages
> already.
> 
> For other cases of ITER_BVEC or ITER_KVEC, if the page is
> anonymous or mapped, dirtying is still needed, otherwise
> the new written data may be dropped like direct-io from user space.

But those would be user pages.  Anyone who passes a kernel page doesn't
expect it do be dirtied for normal kernel interfaces.
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