[RFC PATCH 3/3] docs: hugetlbpage.rst: add hugetlb migration description

[Baolin Wang]

Add some description of the hugetlb migration strategy.

Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
---
 Documentation/admin-guide/mm/hugetlbpage.rst | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/admin-guide/mm/hugetlbpage.rst b/Documentation/admin-guide/mm/hugetlbpage.rst
index e4d4b4a8dc97..68d7bc2165c9 100644
--- a/Documentation/admin-guide/mm/hugetlbpage.rst
+++ b/Documentation/admin-guide/mm/hugetlbpage.rst
@@ -376,6 +376,13 @@ Note that the number of overcommit and reserve pages remain global quantities,
 as we don't know until fault time, when the faulting task's mempolicy is
 applied, from which node the huge page allocation will be attempted.
 
+The hugetlb may be migrated between the per-node hugepages pool in the following
+scenarios: memory offline, memory failure, longterm pinning, syscalls(mbind,
+migrate_pages, move_pages), alloc_contig_range() and alloc_contig_pages(). Now
+only memory offline, memory failure and syscalls allow fallback to allocate a
+new hugetlb on a different node if the current node is unable to allocate during
+hugetlb migration, that means these 3 cases can break the per-node hugepages pool.
+
 .. _using_huge_pages:
 
 Using Huge Pages
-- 
2.39.3