[PATCH v1 1/1] Docs/mm/damon: Document DAMON actions when TRANSPARENT_HUGEPAGE is off

[gutierrez.asier]

From: Asier Gutierrez <gutierrez.asier@xxxxxxxxxxxxxxxxxxx>

MADV_HUGEPAGE and MADV_NOHUGEPAGE are guarded and they
are not available when compiling the kernel without TRANSPARENT_HUGEPAGE
option. The DAMON behaviour is to silently fail[1] in when DAMOS_HUGEPAGE or
DAMOS_NOHUGEPAGE are used, but TRANSPARENT_HUGEPAGE is disabled. Update the
DAMON documentation to reflect this behaviour.

[1]: https://lore.kernel.org/damon/66131775-180b-4b9f-b7ce-61a3e077b6e6@xxxxxxxxxxxxxxxxxxx/T/#m278d3c9bbedcceaf2efa51e3dc7b40a40654e51c

Signed-off-by: Asier Gutierrez <gutierrez.asier@xxxxxxxxxxxxxxxxxxx>
---
 Documentation/mm/damon/design.rst | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst
index 29fff20b3c2a..478eab4a186a 100644
--- a/Documentation/mm/damon/design.rst
+++ b/Documentation/mm/damon/design.rst
@@ -460,9 +460,13 @@ that supports each action are as below.
  - ``pageout``: Reclaim the region.
    Supported by ``vaddr``, ``fvaddr`` and ``paddr`` operations set.
  - ``hugepage``: Call ``madvise()`` for the region with ``MADV_HUGEPAGE``.
-   Supported by ``vaddr`` and ``fvaddr`` operations set.
+   Supported by ``vaddr`` and ``fvaddr`` operations set. When
+   TRANSPARENT_HUGEPAGE is disabled, the application of the action will just
+   fail.
  - ``nohugepage``: Call ``madvise()`` for the region with ``MADV_NOHUGEPAGE``.
-   Supported by ``vaddr`` and ``fvaddr`` operations set.
+   Supported by ``vaddr`` and ``fvaddr`` operations set. When
+   TRANSPARENT_HUGEPAGE is disabled, the application of the action will just
+   fail.
  - ``lru_prio``: Prioritize the region on its LRU lists.
    Supported by ``paddr`` operations set.
  - ``lru_deprio``: Deprioritize the region on its LRU lists.
-- 
2.43.0