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From: Matthew Wilcox <willy@infradead.org>
To: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/5] mm: migrate: Move the page count validation to the proper place
Date: Thu, 5 Aug 2021 16:17:35 +0100	[thread overview]
Message-ID: <YQwBD55FZyoY+C5D@casper.infradead.org> (raw)
In-Reply-To: <1f7e1d083864fbb17a20a9c8349d2e8b427e20a3.1628174413.git.baolin.wang@linux.alibaba.com>

On Thu, Aug 05, 2021 at 11:05:56PM +0800, Baolin Wang wrote:
> We've got the expected count for anonymous page or file page by
> expected_page_refs() at the beginning of migrate_page_move_mapping(),
> thus we should move the page count validation a little forward to
> reduce duplicated code.

Please add an explanation to the changelog for why it's safe to pull
this out from under the i_pages lock.

> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> ---
>  mm/migrate.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 239b238..5559571 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -386,11 +386,10 @@ int folio_migrate_mapping(struct address_space *mapping,
>  	int expected_count = expected_page_refs(mapping, &folio->page) + extra_count;
>  	long nr = folio_nr_pages(folio);
>  
> -	if (!mapping) {
> -		/* Anonymous page without mapping */
> -		if (folio_ref_count(folio) != expected_count)
> -			return -EAGAIN;
> +	if (folio_ref_count(folio) != expected_count)
> +		return -EAGAIN;
>  
> +	if (!mapping) {
>  		/* No turning back from here */
>  		newfolio->index = folio->index;
>  		newfolio->mapping = folio->mapping;
> @@ -404,8 +403,7 @@ int folio_migrate_mapping(struct address_space *mapping,
>  	newzone = folio_zone(newfolio);
>  
>  	xas_lock_irq(&xas);
> -	if (folio_ref_count(folio) != expected_count ||
> -	    xas_load(&xas) != folio) {
> +	if (xas_load(&xas) != folio) {
>  		xas_unlock_irq(&xas);
>  		return -EAGAIN;
>  	}
> -- 
> 1.8.3.1
> 
> 

  reply	other threads:[~2021-08-05 15:17 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-05 15:05 [PATCH 0/5] Some cleanup for page migration Baolin Wang
2021-08-05 15:05 ` [PATCH 1/5] mm: migrate: Move the page count validation to the proper place Baolin Wang
2021-08-05 15:17   ` Matthew Wilcox [this message]
2021-08-06  3:07     ` Baolin Wang
2021-08-07  2:02       ` Matthew Wilcox
2021-08-08  2:55         ` Baolin Wang
2021-08-08 10:26           ` Matthew Wilcox
2021-08-08 15:13             ` Baolin Wang
2021-08-08 16:01               ` Matthew Wilcox
2021-08-09  4:19                 ` Baolin Wang
2021-08-05 15:05 ` [PATCH 2/5] mm: migrate: Introduce a local variable to get the number of pages Baolin Wang
2021-08-05 17:42   ` Yang Shi
2021-08-05 15:05 ` [PATCH 3/5] mm: migrate: Fix the incorrect function name in comments Baolin Wang
2021-08-05 17:26   ` Yang Shi
2021-08-09 13:59   ` Alistair Popple
2021-08-05 15:05 ` [PATCH 4/5] mm: migrate: Change to use bool type for 'page_was_mapped' Baolin Wang
2021-08-05 17:34   ` Yang Shi
2021-08-05 15:06 ` [PATCH 5/5] mm: migrate: Remove redundant goto labels Baolin Wang
2021-08-05 19:54   ` Yang Shi
2021-08-06  3:20     ` Baolin Wang
2021-08-06 17:17       ` Yang Shi
2021-08-08  2:56         ` Baolin Wang

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