linux-kernel - Re: [patch 1/2] mm, doc: cleanup and clarify munmap behavior for hugetlb memory

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Message-ID: <alpine.DEB.2.10.1504021536210.15536@chino.kir.corp.google.com>
Date:	Thu, 2 Apr 2015 15:40:56 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Hugh Dickins <hughd@...gle.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Jonathan Corbet <corbet@....net>,
	Davide Libenzi <davidel@...ilserver.org>,
	Luiz Capitulino <lcapitulino@...hat.com>,
	Shuah Khan <shuahkh@....samsung.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Joern Engel <joern@...fs.org>,
	Jianguo Wu <wujianguo@...wei.com>,
	Eric B Munson <emunson@...mai.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: Re: [patch 1/2] mm, doc: cleanup and clarify munmap behavior for
 hugetlb memory

On Sun, 29 Mar 2015, Hugh Dickins wrote:

> > munmap(2) of hugetlb memory requires a length that is hugepage aligned,
> > otherwise it may fail.  Add this to the documentation.
> 
> Thanks for taking this on, David.  But although munmap(2) is the one
> Davide called out, it goes beyond that, doesn't it?  To mprotect and
> madvise and ...
> 

Yes, good point, munmap(2) isn't special in this case, the alignment to 
the native page size of the platform should apply to madvise, mbind, 
mincore, mlock, mprotect, remap_file_pages, etc.

I'd hesitate to compile any authoritative list on the behavior in 
Documentation/vm/hugetlbpage.txt since it would exclude future extensions, 
but I'll update it to be more inclusive of other mm syscalls rather than 
specify only munmap(2).
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