Re: [Virtio-fs] [PATCH v3 2/3] dax: Add a wakeup mode parameter to put_unlocked_entry()

[Dan Williams]

On Tue, Apr 20, 2021 at 7:01 AM Vivek Goyal <vgoyal@xxxxxxxxxx> wrote:
>
> On Tue, Apr 20, 2021 at 09:34:20AM +0200, Greg Kurz wrote:
> > On Mon, 19 Apr 2021 17:36:35 -0400
> > Vivek Goyal <vgoyal@xxxxxxxxxx> wrote:
> >
> > > As of now put_unlocked_entry() always wakes up next waiter. In next
> > > patches we want to wake up all waiters at one callsite. Hence, add a
> > > parameter to the function.
> > >
> > > This patch does not introduce any change of behavior.
> > >
> > > Suggested-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> > > Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
> > > ---
> > >  fs/dax.c | 13 +++++++------
> > >  1 file changed, 7 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/fs/dax.c b/fs/dax.c
> > > index 00978d0838b1..f19d76a6a493 100644
> > > --- a/fs/dax.c
> > > +++ b/fs/dax.c
> > > @@ -275,11 +275,12 @@ static void wait_entry_unlocked(struct xa_state *xas, void *entry)
> > >     finish_wait(wq, &ewait.wait);
> > >  }
> > >
> > > -static void put_unlocked_entry(struct xa_state *xas, void *entry)
> > > +static void put_unlocked_entry(struct xa_state *xas, void *entry,
> > > +                          enum dax_entry_wake_mode mode)
> > >  {
> > >     /* If we were the only waiter woken, wake the next one */
> >
> > With this change, the comment is no longer accurate since the
> > function can now wake all waiters if passed mode == WAKE_ALL.
> > Also, it paraphrases the code which is simple enough, so I'd
> > simply drop it.
> >
> > This is minor though and it shouldn't prevent this fix to go
> > forward.
> >
> > Reviewed-by: Greg Kurz <groug@xxxxxxxx>
>
> Ok, here is the updated patch which drops that comment line.
>
> Vivek

Hi Vivek,

Can you get in the habit of not replying inline with new patches like
this? Collect the review feedback, take a pause, and resend the full
series so tooling like b4 and patchwork can track when a new posting
supersedes a previous one. As is, this inline style inflicts manual
effort on the maintainer.

>
> Subject: dax: Add a wakeup mode parameter to put_unlocked_entry()
>
> As of now put_unlocked_entry() always wakes up next waiter. In next
> patches we want to wake up all waiters at one callsite. Hence, add a
> parameter to the function.
>
> This patch does not introduce any change of behavior.
>
> Suggested-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
> ---
>  fs/dax.c |   14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> Index: redhat-linux/fs/dax.c
> ===================================================================
> --- redhat-linux.orig/fs/dax.c  2021-04-20 09:55:45.105069893 -0400
> +++ redhat-linux/fs/dax.c       2021-04-20 09:56:27.685822730 -0400
> @@ -275,11 +275,11 @@ static void wait_entry_unlocked(struct x
>         finish_wait(wq, &ewait.wait);
>  }
>
> -static void put_unlocked_entry(struct xa_state *xas, void *entry)
> +static void put_unlocked_entry(struct xa_state *xas, void *entry,
> +                              enum dax_entry_wake_mode mode)
>  {
> -       /* If we were the only waiter woken, wake the next one */
>         if (entry && !dax_is_conflict(entry))
> -               dax_wake_entry(xas, entry, WAKE_NEXT);
> +               dax_wake_entry(xas, entry, mode);
>  }
>
>  /*
> @@ -633,7 +633,7 @@ struct page *dax_layout_busy_page_range(
>                         entry = get_unlocked_entry(&xas, 0);
>                 if (entry)
>                         page = dax_busy_page(entry);
> -               put_unlocked_entry(&xas, entry);
> +               put_unlocked_entry(&xas, entry, WAKE_NEXT);
>                 if (page)
>                         break;
>                 if (++scanned % XA_CHECK_SCHED)
> @@ -675,7 +675,7 @@ static int __dax_invalidate_entry(struct
>         mapping->nrexceptional--;
>         ret = 1;
>  out:
> -       put_unlocked_entry(&xas, entry);
> +       put_unlocked_entry(&xas, entry, WAKE_NEXT);
>         xas_unlock_irq(&xas);
>         return ret;
>  }
> @@ -954,7 +954,7 @@ static int dax_writeback_one(struct xa_s
>         return ret;
>
>   put_unlocked:
> -       put_unlocked_entry(xas, entry);
> +       put_unlocked_entry(xas, entry, WAKE_NEXT);
>         return ret;
>  }
>
> @@ -1695,7 +1695,7 @@ dax_insert_pfn_mkwrite(struct vm_fault *
>         /* Did we race with someone splitting entry or so? */
>         if (!entry || dax_is_conflict(entry) ||
>             (order == 0 && !dax_is_pte_entry(entry))) {
> -               put_unlocked_entry(&xas, entry);
> +               put_unlocked_entry(&xas, entry, WAKE_NEXT);
>                 xas_unlock_irq(&xas);
>                 trace_dax_insert_pfn_mkwrite_no_entry(mapping->host, vmf,
>                                                       VM_FAULT_NOPAGE);
>