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authorMatthew Wilcox (Oracle) <willy@infradead.org>2020-06-01 21:46:54 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-02 10:59:07 -0700
commit2d8163e4899dad92175eedd1c2326c875eaa74fa (patch)
tree61764d0d42d61e5bac5b94b56be6a8d18f751961 /mm/readahead.c
parent2c684234d36f7e8c80414e4a772911d407e821fa (diff)
downloadlinux-2d8163e4899dad92175eedd1c2326c875eaa74fa.tar.bz2
mm: document why we don't set PageReadahead
If the page is already in cache, we don't set PageReadahead on it. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: William Kucharski <william.kucharski@oracle.com> Cc: Chao Yu <yuchao0@huawei.com> Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: Darrick J. Wong <darrick.wong@oracle.com> Cc: Dave Chinner <dchinner@redhat.com> Cc: Eric Biggers <ebiggers@google.com> Cc: Gao Xiang <gaoxiang25@huawei.com> Cc: Jaegeuk Kim <jaegeuk@kernel.org> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Joseph Qi <joseph.qi@linux.alibaba.com> Cc: Junxiao Bi <junxiao.bi@oracle.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com> Cc: Miklos Szeredi <mszeredi@redhat.com> Link: http://lkml.kernel.org/r/20200414150233.24495-15-willy@infradead.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/readahead.c')
-rw-r--r--mm/readahead.c9
1 files 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;