linux-kernel - Re: [PATCH v2 3/4] mm/vmap: get rid of one single unlink

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Date:   Mon, 27 May 2019 11:37:26 +0200
From:   Uladzislau Rezki <urezki@...il.com>
To:     Hillf Danton <hdanton@...a.com>
Cc:     "Uladzislau Rezki (Sony)" <urezki@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Roman Gushchin <guro@...com>, Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Garnier <thgarnie@...gle.com>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joelaf@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...e.hu>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH v2 3/4] mm/vmap: get rid of one single unlink_va() when
 merge

On Mon, May 27, 2019 at 11:07:12AM +0800, Hillf Danton wrote:
> 
> On Mon, 27 May 2019 05:22:28 +0800 Uladzislau Rezki (Sony) wrote:
> > It does not make sense to try to "unlink" the node that is
> > definitely not linked with a list nor tree. On the first
> > merge step VA just points to the previously disconnected
> > busy area.
> > 
> > On the second step, check if the node has been merged and do
> > "unlink" if so, because now it points to an object that must
> > be linked.
> > 
> > Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
> > ---
> 
> Acked-by: Hillf Danton <hdanton@...a.com>
> 
Thanks!

> >  mm/vmalloc.c | 9 +++------
> >  1 file changed, 3 insertions(+), 6 deletions(-)
> > 
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index b553047aa05b..6f91136f2cc8 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -718,9 +718,6 @@ merge_or_add_vmap_area(struct vmap_area *va,
> >  			/* Check and update the tree if needed. */
> >  			augment_tree_propagate_from(sibling);
> > 
> > -			/* Remove this VA, it has been merged. */
> > -			unlink_va(va, root);
> > -
> >  			/* Free vmap_area object. */
> >  			kmem_cache_free(vmap_area_cachep, va);
> > 
> > @@ -745,12 +742,12 @@ merge_or_add_vmap_area(struct vmap_area *va,
> >  			/* Check and update the tree if needed. */
> >  			augment_tree_propagate_from(sibling);
> >
> > -			/* Remove this VA, it has been merged. */
> > -			unlink_va(va, root);
> > +			/* Remove this VA, if it has been merged. */
> > +			if (merged)
> > +				unlink_va(va, root);
> >
> The change makes the code much easier to read, thanks.
> What is more, checking merged makes the polished comment unnecessary, imo.
> And it can be applied, I think, to the above hunk.
> 
That is odd. Will remove it.

--
Vlad Rezki