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From: Matthew Wilcox <willy@infradead.org>
To: Rongwei Wang <rongwei.wang@linux.alibaba.com>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: rectify a page bad reason
Date: Tue, 29 Dec 2020 12:13:53 +0000	[thread overview]
Message-ID: <20201229121353.GB28221@casper.infradead.org> (raw)
In-Reply-To: <20201229031156.3861-1-rongwei.wang@linux.alibaba.com>

On Tue, Dec 29, 2020 at 11:11:56AM +0800, Rongwei Wang wrote:
> When I was doing some memory-related projects, it always reported error
> "nonzero mapcount", but its judgment condition was that _mapcount was not equal
> to -1, so I felt the original string was a bit inappropriate, so I tried to
> update it.

But '_mapcount' of -1 _is_ a mapcount of 0.  If we need to improve the
documentation somewhere, that'd be better than changing this message.

I do wonder if we want to add:

	if (unlikely(page_has_type(page))
		bad_reason = "page still typed";

It's covered by the non-zero mapcount case, but is slightly misleading.

>  	if (unlikely(atomic_read(&page->_mapcount) != -1))
> -		bad_reason = "nonzero mapcount";
> +		bad_reason = "non-(-1) _mapcount";
>  	if (unlikely(page->mapping != NULL))
>  		bad_reason = "non-NULL mapping";
>  	if (unlikely(page_ref_count(page) != 0))
> -- 
> 1.8.3.1
> 
> 

      parent reply	other threads:[~2020-12-29 12:14 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-29  3:11 [PATCH] mm: rectify a page bad reason Rongwei Wang
     [not found] ` <CAPSr9jFf4HoODzubWx-JkVKK69YGx0vgaesuVU8od-qyyGOjpw@mail.gmail.com>
2020-12-29  7:22   ` Rongwei Wang
2020-12-29 12:13 ` Matthew Wilcox [this message]

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