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

Vivek Goyal
2021-04-20T14:00:48Z

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@redhat.com> 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@intel.com>
> > Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> > ---
> > 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@kaod.org>

Ok, here is the updated patch which drops that comment line.

Vivek

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@intel.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
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);