Re: [PATCH] aio: propogate post-EIOCBQUEUED errors to completion event

[Zach Brown <zach.brown@oracle.com>]

> > There are some strange O_DIRECT corner cases in here such that the  
> > 'last
> > writer' may actually be a 'last reader' and winning can mean have  
> > a copy
> > of the page in page cache older than the copy on disk.
>
> As long as it is marked dirty so that it eventually gets synced to  
> disk,
> it shouldn't matter.

No, Chris is pointing out that an an O_DIRECT write can leave clean  
read pages in the page cache.

All it takes is giving a source buffer for the write which is an mmap 
()ed apeture of the region that is being written to.  If you get the  
offsets right you can get the get_user_pages() down in fs/direct-io.c  
will populate the page cache before the actual O_DIRECT write gets to  
it.

- z
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