From: Matthew Wilcox <willy@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Nick Piggin <npiggin@suse.de>, Hugh Dickins <hughd@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] page_alloc: Fix freeing non-compound pages
Date: Tue, 22 Sep 2020 15:35:59 +0100 [thread overview]
Message-ID: <20200922143559.GF32101@casper.infradead.org> (raw)
In-Reply-To: <20200922140017.26387-1-willy@infradead.org>
On Tue, Sep 22, 2020 at 03:00:17PM +0100, Matthew Wilcox (Oracle) wrote:
> void __free_pages(struct page *page, unsigned int order)
> {
> if (put_page_testzero(page))
> free_the_page(page, order);
> + else
> + while (order-- > 0)
> + free_the_page(page + (1 << order), order);
> }
> EXPORT_SYMBOL(__free_pages);
... a three line patch and one of them is wrong.
- else
+ else if (!PageHead(page))
Anyone got a smart idea about how to _test_ this code path? I'm
wondering about loading one kernel module which wanders through memmap
calling
if (page_cache_get_speculative(page)) put_page(page);
and another kernel module that calls
__free_pages(alloc_page(GFP_KERNEL, 1), 1);
and putting in a printk to let me know when we hit it.
next prev parent reply other threads:[~2020-09-22 14:36 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-22 14:00 [PATCH] page_alloc: Fix freeing non-compound pages Matthew Wilcox (Oracle)
2020-09-22 14:35 ` Matthew Wilcox [this message]
2020-09-24 9:00 ` peterz
2020-09-24 11:07 ` Matthew Wilcox
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