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Message-ID: <20220127163601.sby4qvqitwj2nvin@revolver>
Date: Thu, 27 Jan 2022 16:36:10 +0000
From: Liam Howlett <liam.howlett@...cle.com>
To: Vlastimil Babka <vbabka@...e.cz>
CC: Matthew Wilcox <willy@...radead.org>,
"maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Song Liu <songliubraving@...com>,
Davidlohr Bueso <dave@...olabs.net>,
"Paul E . McKenney" <paulmck@...nel.org>,
Laurent Dufour <ldufour@...ux.ibm.com>,
David Rientjes <rientjes@...gle.com>,
Axel Rasmussen <axelrasmussen@...gle.com>,
Suren Baghdasaryan <surenb@...gle.com>,
Rik van Riel <riel@...riel.com>,
Peter Zijlstra <peterz@...radead.org>,
Michel Lespinasse <walken.cr@...il.com>,
Jerome Glisse <jglisse@...hat.com>,
Minchan Kim <minchan@...gle.com>,
Joel Fernandes <joelaf@...gle.com>,
Rom Lemarchand <romlem@...gle.com>
Subject: Re: [PATCH v4 64/66] nommu: Remove uses of VMA linked list
* Vlastimil Babka <vbabka@...e.cz> [220120 12:06]:
> On 1/20/22 16:54, Matthew Wilcox wrote:
> > On Thu, Jan 20, 2022 at 04:06:21PM +0100, Vlastimil Babka wrote:
> >> On 12/1/21 15:30, Liam Howlett wrote:
> >> > From: "Matthew Wilcox (Oracle)" <willy@...radead.org>
> >> >
> >> > Use the maple tree or VMA iterator instead. This is faster and will
> >> > allow us to shrink the VMA.
> >> >
> >> > Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> >> > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> >>
> >> Acked-by: Vlastimil Babka <vbabka@...e.cz>
> >>
> >> But I think some fixup needed:
> >>
> >> > @@ -1456,12 +1458,14 @@ void exit_mmap(struct mm_struct *mm)
> >> >
> >> > mm->total_vm = 0;
> >> >
> >> > - while ((vma = mm->mmap)) {
> >> > - mm->mmap = vma->vm_next;
> >> > + mmap_write_lock(mm);
> >>
> >> If locking was missing, should have been added sooner than now?
> >
> > I don't think so? This is the exit_mmap() path, so we know nobody
> > has access to the mm. We didn't need to hold the lock at this point
> > before, but now for_each_vma() will check we're holding the mmap_lock.
>
> It has crossed my mind that it is there to make asserts happy, in which case
> a clarifying comment would be useful.
I will add the comment.
>
> >> > + for_each_vma(vmi, vma) {
> >> > delete_vma_from_mm(vma);
> >> > delete_vma(mm, vma);
> >> > cond_resched();
> >> > }
> >> > + __mt_destroy(&mm->mm_mt);
> >>
> >> And this at the point mm_mt was added?
> >
> > You mean we should have been calling __mt_destroy() earlier in the
> > patch series?
>
> Yeah.
>
> > Umm ... I'll defer to Liam on that one.
Yes, I will move this to the correct patch.
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