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-rw-r--r--include/linux/page-flags.h5
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 77de28bfefb0..acf7988fd640 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -63,6 +63,11 @@
* page_waitqueue(page) is a wait queue of all tasks waiting for the page
* to become unlocked.
*
+ * PG_swapbacked is set when a page uses swap as a backing storage. This are
+ * usually PageAnon or shmem pages but please note that even anonymous pages
+ * might lose their PG_swapbacked flag when they simply can be dropped (e.g. as
+ * a result of MADV_FREE).
+ *
* PG_uptodate tells whether the page's contents is valid. When a read
* completes, the page becomes uptodate, unless a disk I/O error happened.
*