linux-kernel - Re: [PATCH v3 12/13] dax: handle truncate of dma-busy pages

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Message-ID: <20171021081140.GA21101@lst.de>
Date:   Sat, 21 Oct 2017 10:11:40 +0200
From:   Christoph Hellwig <hch@....de>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Christoph Hellwig <hch@....de>, Jeff Layton <jlayton@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jan Kara <jack@...e.cz>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Dave Chinner <david@...morbit.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Linux MM <linux-mm@...ck.org>, Jeff Moyer <jmoyer@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        linux-xfs@...r.kernel.org,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>
Subject: Re: [PATCH v3 12/13] dax: handle truncate of dma-busy pages

On Fri, Oct 20, 2017 at 10:27:22AM -0700, Dan Williams wrote:
> I'll take a look at hooking this up through a page-idle callback. Can
> I get some breadcrumbs to grep for from XFS folks on how to set/clear
> the busy state of extents?

As Brian pointed out it's the xfs_extent_busy.c file (and I pointed
out the same in a reply to the previous series).  Be careful because
you'll need a refcount or flags now that there are different busy
reasons.

I still think we'd be better off just blocking on an elevated page
count directly in truncate as that will avoid all the busy list
manipulations.