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

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Message-ID: <20190710202647.GA7269@quack2.suse.cz>
Date:   Wed, 10 Jul 2019 22:26:47 +0200
From:   Jan Kara <jack@...e.cz>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Jan Kara <jack@...e.cz>, 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 10-07-19 13:15:39, Matthew Wilcox wrote:
> On Wed, Jul 10, 2019 at 09:02:04PM +0200, Jan Kara wrote:
> > +#define DAX_ENTRY_CONFLICT dax_make_entry(pfn_to_pfn_t(1), DAX_EMPTY)
> 
> I was hoping to get rid of DAX_EMPTY ... it's almost unused now.  Once
> we switch to having a single DAX_LOCK value instead of a single bit,
> I think it can go away, freeing up two bits.
> 
> If you really want a special DAX_ENTRY_CONFLICT, I think we can make
> one in the 2..4094 range.
> 
> That aside, this looks pretty similar to the previous patch I sent, so
> if you're now happy with this, let's add
> 
> #define XA_DAX_CONFLICT_ENTRY xa_mk_internal(258)
> 
> to xarray.h and do it that way?

Yeah, that would work for me as well. The chosen value for DAX_ENTRY_CONFLICT
was pretty arbitrary. Or we could possibly use:

#define DAX_ENTRY_CONFLICT XA_ZERO_ENTRY

so that we don't leak DAX-specific internal definition into xarray.h?

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR