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From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Jan Kara <jack@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org
Subject: Re: [PATCH] mm: Fix THP handling in invalidate_mapping_pages()
Date: Mon, 19 Jun 2017 16:25:10 +0300	[thread overview]
Message-ID: <20170619132510.4uzwyww43g5jt5si@node.shutemov.name> (raw)
In-Reply-To: <20170619124723.21656-1-jack@suse.cz>

On Mon, Jun 19, 2017 at 02:47:23PM +0200, Jan Kara wrote:
> The condition checking for THP straddling end of invalidated range is
> wrong - it checks 'index' against 'end' but 'index' has been already
> advanced to point to the end of THP and thus the condition can never be
> true. As a result THP straddling 'end' has been fully invalidated. Given
> the nature of invalidate_mapping_pages(), this could be only performance
> issue. In fact, we are lucky the condition is wrong because if it was
> ever true, we'd leave locked page behind.
> 
> Fix the condition checking for THP straddling 'end' and also properly
> unlock the page. Also update the comment before the condition to explain
> why we decide not to invalidate the page as it was not clear to me and I
> had to ask Kirill.
> 
> Signed-off-by: Jan Kara <jack@suse.cz>

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

Thanks a lot for the fix.

-- 
 Kirill A. Shutemov

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      reply	other threads:[~2017-06-19 13:25 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-19 12:47 [PATCH] mm: Fix THP handling in invalidate_mapping_pages() Jan Kara
2017-06-19 13:25 ` Kirill A. Shutemov [this message]

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