From: Baolin Wang <baolin.wang@linux.alibaba.com>
To: Matthew Wilcox <willy@infradead.org>
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: Fri, 6 Aug 2021 11:07:18 +0800 [thread overview]
Message-ID: <a02346d7-1a79-eb92-cb1f-033e6b58fa3f@linux.alibaba.com> (raw)
In-Reply-To: <YQwBD55FZyoY+C5D@casper.infradead.org>
Hi Matthew,
> 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.
Sure. In folio_migrate_mapping(), we are sure that the migration page
was isolated from lru list and locked, so I think there are no race to
get the page count without i_pages lock. Please correct me if I missed
something else. Thanks.
>
>> 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
>>
>>
next prev parent reply other threads:[~2021-08-06 3:06 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
2021-08-06 3:07 ` Baolin Wang [this message]
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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