linux-kernel - Re: [PATCH] get_user_pages(..., write==1, ...) may return with readable pte.

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Message-ID: <20061014101507.GA6316@lnx-holt.americas.sgi.com>
Date:	Sat, 14 Oct 2006 05:15:07 -0500
From:	Robin Holt <holt@....com>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Robin Holt <holt@....com>, Hugh Dickins <hugh@...itas.com>,
	Linus Torvalds <torvalds@...l.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] get_user_pages(..., write==1, ...) may return with readable pte.

> dup_mmap holds mmap_sem for write. get_user_pages caller must hold it
> for read.

I could have sworn I checked for that and found a down_read(), but
now that I look when I have some time, it is clearly a down_write().
Sorry for the distraction.

It is a user job that is passing data between hosts.  The host is
under heavy memory pressure and one rank of the MPI job gets silent
data corruption.

Thanks and sorry for wasting your time,
Robin
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