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

[Vivek Goyal]

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

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);