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Message-ID: <Pine.LNX.4.64.0907301248090.27155@sister.anvils> Date: Thu, 30 Jul 2009 12:48:56 +0100 (BST) From: Hugh Dickins <hugh.dickins@...cali.co.uk> To: Robin Holt <holt@....com> cc: Laurent Pinchart <laurent.pinchart@...net.be>, linux-kernel@...r.kernel.org, v4l2_linux <linux-media@...r.kernel.org> Subject: Re: Is get_user_pages() enough to prevent pages from being swapped out ? On Thu, 30 Jul 2009, Robin Holt wrote: > > > On Wednesday 29 July 2009 17:26:11 Hugh Dickins wrote: > ... > > > > On the other hand, despite the raised reference count, under memory > > > > pressure that page might get unmapped from the user pagetable, and > > > > might even be written out to swap in its half-dirty state (though > > One thing you did not mention in the above description is that the page > is marked clean by the write-out to swap. I am not sure I recall the > method of mapping involved here, but it is necessary to ensure the page > is marked dirty again before the driver releases it. If the page is > not marked dirty as part of your method of releasing it, the changes > you have made between when the page was first written out and when you > are freeing it will get lost. Yes indeed: thanks, Robin. Hugh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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