linux-kernel - Re: [PATCH 03/10] mm: abstract duplicated policy comparison

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Message-ID: <20240806145014.7e2c8557@mordecai.tesarici.cz>
Date: Tue, 6 Aug 2024 14:50:14 +0200
From: Petr Tesařík <petr@...arici.cz>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, Andrew Morton
 <akpm@...ux-foundation.org>, "Liam R . Howlett" <Liam.Howlett@...cle.com>,
 Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH 03/10] mm: abstract duplicated policy comparison

On Mon,  5 Aug 2024 13:13:50 +0100
Lorenzo Stoakes <lorenzo.stoakes@...cle.com> wrote:

> Both can_vma_merge_before() and can_vma_merge_after() are invoked after
> checking for compatible VMA NUMA policy, we can simply move this to
> is_mergeable_vma() and abstract this altogether.
> 
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> ---
>  mm/mmap.c | 8 +++-----
>  mm/vma.c  | 9 ++++-----
>  2 files changed, 7 insertions(+), 10 deletions(-)
> 
> diff --git a/mm/mmap.c b/mm/mmap.c
> index f931000c561f..721ced6e37b0 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1422,8 +1422,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
>  
>  	/* Attempt to expand an old mapping */
>  	/* Check next */
> -	if (next && next->vm_start == end && !vma_policy(next) &&
> -	    can_vma_merge_before(&vmg)) {
> +	if (next && next->vm_start == end && can_vma_merge_before(&vmg)) {
>  		merge_end = next->vm_end;
>  		vma = next;
>  		vmg.pgoff = next->vm_pgoff - pglen;
> @@ -1435,8 +1434,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
>  	}
>  
>  	/* Check prev */
> -	if (prev && prev->vm_end == addr && !vma_policy(prev) &&
> -	    can_vma_merge_after(&vmg)) {
> +	if (prev && prev->vm_end == addr && can_vma_merge_after(&vmg)) {
>  		merge_start = prev->vm_start;
>  		vma = prev;
>  		vmg.pgoff = prev->vm_pgoff;
> @@ -1798,7 +1796,7 @@ static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *vma,
>  	 * Expand the existing vma if possible; Note that singular lists do not
>  	 * occur after forking, so the expand will only happen on new VMAs.
>  	 */
> -	if (vma && vma->vm_end == addr && !vma_policy(vma)) {
> +	if (vma && vma->vm_end == addr) {
>  		struct vma_merge_struct vmg = {
>  			.prev = vma,
>  			.flags = flags,
> diff --git a/mm/vma.c b/mm/vma.c
> index 20c4ce7712c0..b452b472a085 100644
> --- a/mm/vma.c
> +++ b/mm/vma.c
> @@ -19,6 +19,8 @@ static inline bool is_mergeable_vma(struct vma_merge_struct *vmg, bool merge_nex
>  	 */
>  	bool may_remove_vma = merge_next;
>  
> +	if (!mpol_equal(vmg->policy, vma_policy(vma)))
> +		return false;
>  	/*
>  	 * VM_SOFTDIRTY should not prevent from VMA merging, if we
>  	 * match the flags but dirty bit -- the caller should mark
> @@ -971,17 +973,14 @@ static struct vm_area_struct *vma_merge(struct vma_merge_struct *vmg)
>  		vma_pgoff = prev->vm_pgoff;
>  
>  		/* Can we merge the predecessor? */
> -		if (addr == prev->vm_end && mpol_equal(vma_policy(prev), vmg->policy)
> -		    && can_vma_merge_after(vmg)) {
> -
> +		if (addr == prev->vm_end && can_vma_merge_after(vmg)) {
>  			merge_prev = true;
>  			vma_prev(vmg->vmi);
>  		}
>  	}
>  
>  	/* Can we merge the successor? */
> -	if (next && mpol_equal(vmg->policy, vma_policy(next)) &&
> -	    can_vma_merge_before(vmg)) {
> +	if (next && can_vma_merge_before(vmg)) {
>  		merge_next = true;
>  	}
>  

Looks good.

Petr T