Re: [PATCH 1/3] thp: reduce indentation level in change_huge_pmd()

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On Thu, Dec 07, 2017 at 11:22:50AM +0100, Jack Wang wrote:
> From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> 
> commit 0a85e51d37645e9ce57e5e1a30859e07810ed07c upstream.
> 
> Patch series "thp: fix few MADV_DONTNEED races"
> 
> For MADV_DONTNEED to work properly with huge pages, it's critical to not
> clear pmd intermittently unless you hold down_write(mmap_sem).
> 
> Otherwise MADV_DONTNEED can miss the THP which can lead to userspace
> breakage.
> 
> See example of such race in commit message of patch 2/4.
> 
> All these races are found by code inspection.  I haven't seen them
> triggered.  I don't think it's worth to apply them to stable@.
> 
> This patch (of 4):

What about all 4 of these?

And should this also go into 4.9?  I don't want to include fixes into
4.4-stable without them also being in 4.9-stable, as that would be a
regression for people upgrading.

thanks,

greg k-h



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