[PATCH v9 14/25] mm: Document why we don't set PageReadahead
From: Matthew Wilcox <willy@infradead.org>
Date: 2020-03-20 14:24:27
Also in:
linux-btrfs, linux-f2fs-devel, linux-fsdevel, linux-mm, linux-xfs, lkml, ocfs2-devel
Subsystem:
memory management, page cache, the rest · Maintainers:
Andrew Morton, Matthew Wilcox, Linus Torvalds
From: "Matthew Wilcox (Oracle)" <willy@infradead.org> If the page is already in cache, we don't set PageReadahead on it. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: William Kucharski <redacted> --- mm/readahead.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/mm/readahead.c b/mm/readahead.c
index 8ee9036fd681..0afb55a49909 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