From: SeongJae Park <sj@kernel.org>
Date: Sat, 7 Mar 2026 19:53:52 +0000 (-0800)
Subject: mm/damon: document non-zero length damon_region assumption
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3802e1d98e92ca6abdd25446b802f405fef83da0;p=thirdparty%2Fkernel%2Flinux.git

mm/damon: document non-zero length damon_region assumption

DAMON regions are assumed to always be non-zero length.  There was a
confusion [1] about it, probably due to lack of the documentation.
Document it.

Link: https://lkml.kernel.org/r/20260307195356.203753-5-sj@kernel.org
Link: https://lore.kernel.org/20251231070029.79682-1-sj@kernel.org/ [1]
Signed-off-by: SeongJae Park <sj@kernel.org>
Acked-by: wang lian <lianux.mm@gmail.com>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: David Gow <davidgow@google.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 60e6da3012fad..7d0265d029541 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -55,6 +55,8 @@ struct damon_size_range {
  * @list:		List head for siblings.
  * @age:		Age of this region.
  *
+ * For any use case, @ar should be non-zero positive size.
+ *
  * @nr_accesses is reset to zero for every &damon_attrs->aggr_interval and be
  * increased for every &damon_attrs->sample_interval if an access to the region
  * during the last sampling interval is found.  The update of this field should