linux-kernel - Re: [PATCH v4 64/66] nommu: Remove uses of VMA linked list

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Date:   Thu, 20 Jan 2022 16:06:21 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Liam Howlett <liam.howlett@...cle.com>,
        "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>
Cc:     Song Liu <songliubraving@...com>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Matthew Wilcox <willy@...radead.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

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?

> +	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?

> +	mmap_write_unlock(mm);
>  }
>  
>  int vm_brk(unsigned long addr, unsigned long len)