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Date: Mon, 23 Mar 2020 13:22:48 -0700 From: Matthew Wilcox <willy@...radead.org> To: Andrew Morton <akpm@...ux-foundation.org> Cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>, linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org, linux-btrfs@...r.kernel.org, linux-erofs@...ts.ozlabs.org, linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net, cluster-devel@...hat.com, ocfs2-devel@....oracle.com, linux-xfs@...r.kernel.org, Christoph Hellwig <hch@....de>, William Kucharski <william.kucharski@...cle.com> Subject: [PATCH v10 14/25] mm: Document why we don't set PageReadahead From: "Matthew Wilcox (Oracle)" <willy@...radead.org> If the page is already in cache, we don't set PageReadahead on it. Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org> Reviewed-by: Christoph Hellwig <hch@....de> Reviewed-by: William Kucharski <william.kucharski@...cle.com> --- mm/readahead.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/mm/readahead.c b/mm/readahead.c index ae231a5312cb..73cb59ed5cff 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -195,9 +195,12 @@ void page_cache_readahead_unbounded(struct address_space *mapping, if (page && !xa_is_value(page)) { /* - * Page already present? Kick off the current batch of - * contiguous pages before continuing with the next - * batch. + * Page already present? Kick off the current batch + * of contiguous pages before continuing with the + * next batch. This page may be the one we would + * have intended to mark as Readahead, but we don't + * have a stable reference to this page, and it's + * not worth getting one just for that. */ read_pages(&rac, &page_pool, true); continue; -- 2.25.1
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