From: John Hubbard <jhubbard@nvidia.com>
To: "Huang, Ying" <ying.huang@intel.com>,
Alistair Popple <apopple@nvidia.com>
Cc: Yang Shi <shy828301@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Zi Yan <ziy@nvidia.com>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
Oscar Salvador <osalvador@suse.de>,
Matthew Wilcox <willy@infradead.org>
Subject: Re: [RFC 2/6] mm/migrate_pages: split unmap_and_move() to _unmap() and _move()
Date: Tue, 27 Sep 2022 18:44:53 -0700 [thread overview]
Message-ID: <240bbb01-1f26-71ee-233a-ad65313ac358@nvidia.com> (raw)
In-Reply-To: <87czbg2s3b.fsf@yhuang6-desk2.ccr.corp.intel.com>
On 9/27/22 18:41, Huang, Ying wrote:
>>>> I also agree that we cannot make any rules such as "do not lock > 1 page
>>>> at the same time, elsewhere in the kernel", because it is already
>>>> happening, for example in page-writeback.c, which locks PAGEVEC_SIZE
>>>> (15) pages per batch [1].
>>
>> That's not really the case though. The inner loop of write_cache_page()
>> only ever locks one page at a time, either directly via the
>> unlock_page() on L2338 (those goto's are amazing) or indirectly via
>> (*writepage)() on L2359.
>>
>> So there's no deadlock potential there because unlocking any previously
>> locked page(s) doesn't depend on obtaining the lock for another page.
>> Unless I've missed something?
>
> Yes. This is my understanding too after checking ext4_writepage().
>
Yes, I missed the ".writepage() shall unlock the page" design point. Now
it seems much more reasonable and safer. :)
thanks,
--
John Hubbard
NVIDIA
next prev parent reply other threads:[~2022-09-28 1:45 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-21 6:06 [RFC 0/6] migrate_pages(): batch TLB flushing Huang Ying
2022-09-21 6:06 ` [RFC 1/6] mm/migrate_pages: separate huge page and normal pages migration Huang Ying
2022-09-21 15:55 ` Zi Yan
2022-09-22 1:14 ` Huang, Ying
2022-09-22 6:03 ` Baolin Wang
2022-09-22 6:22 ` Huang, Ying
2022-09-21 6:06 ` [RFC 2/6] mm/migrate_pages: split unmap_and_move() to _unmap() and _move() Huang Ying
2022-09-21 16:08 ` Zi Yan
2022-09-22 1:15 ` Huang, Ying
2022-09-22 6:36 ` Baolin Wang
2022-09-26 9:28 ` Alistair Popple
2022-09-26 18:06 ` Yang Shi
2022-09-27 0:02 ` Alistair Popple
2022-09-27 1:51 ` Huang, Ying
2022-09-27 20:34 ` John Hubbard
2022-09-27 20:57 ` Yang Shi
2022-09-28 0:59 ` Alistair Popple
2022-09-28 1:41 ` Huang, Ying
2022-09-28 1:44 ` John Hubbard [this message]
2022-09-28 1:49 ` Yang Shi
2022-09-28 1:56 ` John Hubbard
2022-09-28 2:14 ` Yang Shi
2022-09-28 2:57 ` John Hubbard
2022-09-28 3:25 ` Yang Shi
2022-09-28 3:39 ` Yang Shi
2022-09-27 20:56 ` Yang Shi
2022-09-27 20:54 ` Yang Shi
2022-09-21 6:06 ` [RFC 3/6] mm/migrate_pages: restrict number of pages to migrate in batch Huang Ying
2022-09-21 16:10 ` Zi Yan
2022-09-21 16:15 ` Zi Yan
2022-09-22 1:15 ` Huang, Ying
2022-09-21 6:06 ` [RFC 4/6] mm/migrate_pages: batch _unmap and _move Huang Ying
2022-09-21 6:06 ` [RFC 5/6] mm/migrate_pages: share more code between " Huang Ying
2022-09-21 6:06 ` [RFC 6/6] mm/migrate_pages: batch flushing TLB Huang Ying
2022-09-21 15:47 ` [RFC 0/6] migrate_pages(): batch TLB flushing Zi Yan
2022-09-22 1:45 ` Huang, Ying
2022-09-22 3:47 ` haoxin
2022-09-22 4:36 ` Huang, Ying
2022-09-22 12:50 ` Bharata B Rao
2022-09-23 7:52 ` Huang, Ying
2022-09-27 10:46 ` Bharata B Rao
2022-09-28 1:46 ` Huang, Ying
2022-09-26 9:11 ` Alistair Popple
2022-09-27 11:21 ` haoxin
2022-09-28 2:01 ` Huang, Ying
2022-09-28 3:33 ` haoxin
2022-09-28 4:53 ` Huang, Ying
2022-11-01 14:49 ` Hesham Almatary
2022-11-02 3:14 ` Huang, Ying
2022-11-02 14:13 ` Hesham Almatary
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