linux-kernel - Re: [PATCH] dax: Fix missed PMD wakeups

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Message-ID: <20190711030855.GO32320@bombadil.infradead.org>
Date:   Wed, 10 Jul 2019 20:08:55 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Jan Kara <jack@...e.cz>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Boaz Harrosh <openosd@...il.com>,
        stable <stable@...r.kernel.org>,
        Robert Barror <robert.barror@...el.com>,
        Seema Pandit <seema.pandit@...el.com>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dax: Fix missed PMD wakeups

On Wed, Jul 10, 2019 at 09:02:04PM +0200, Jan Kara wrote:
> @@ -848,7 +853,7 @@ static int dax_writeback_one(struct xa_state *xas, struct dax_device *dax_dev,
>  	if (unlikely(dax_is_locked(entry))) {
>  		void *old_entry = entry;
>  
> -		entry = get_unlocked_entry(xas);
> +		entry = get_unlocked_entry(xas, 0);
>  
>  		/* Entry got punched out / reallocated? */
>  		if (!entry || WARN_ON_ONCE(!xa_is_value(entry)))

I'm not sure about this one.  Are we sure there will never be a dirty
PMD entry?  Even if we can't create one today, it feels like a bit of
a landmine to leave for someone who creates one in the future.