linux-kernel - Re: [PATCH v4 48/66] fork: Use VMA iterator

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Date:   Wed, 19 Jan 2022 17:51:37 +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 48/66] fork: Use VMA iterator

On 12/1/21 15:30, Liam Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> 
> The VMA iterator is faster than the linked list and removing the linked
> list will shrink the vm_area_struct.
> 
> 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>

> ---
>  kernel/fork.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 3493117c8d35..6de302e93519 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1228,13 +1228,16 @@ int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
>  	/* Forbid mm->exe_file change if old file still mapped. */
>  	old_exe_file = get_mm_exe_file(mm);
>  	if (old_exe_file) {
> +		VMA_ITERATOR(vmi, mm, 0);
>  		mmap_read_lock(mm);
> -		for (vma = mm->mmap; vma && !ret; vma = vma->vm_next) {
> +		for_each_vma(vmi, vma) {
>  			if (!vma->vm_file)
>  				continue;
>  			if (path_equal(&vma->vm_file->f_path,
> -				       &old_exe_file->f_path))
> +				       &old_exe_file->f_path)) {
>  				ret = -EBUSY;
> +				break;
> +			}
>  		}
>  		mmap_read_unlock(mm);
>  		fput(old_exe_file);