On 13 Apr 2026, at 16:47, Matthew Wilcox wrote: > On Mon, Apr 13, 2026 at 03:20:30PM -0400, Zi Yan wrote: >> +++ b/tools/testing/selftests/mm/guard-regions.c >> @@ -2205,7 +2205,7 @@ TEST_F(guard_regions, collapse) >> >> /* >> * We must close and re-open local-file backed as read-only for >> - * CONFIG_READ_ONLY_THP_FOR_FS to work. >> + * MADV_COLLAPSE to work. > > Is this true? Does MADV_COLLAPSE refuse to work on writable files? > Should we delete some code here as well as fix the comment? ;-)
file_thp_enabled() used by __thp_vma_allowable_orders() refuses writable files with inode_is_open_for_write(). That should prevent MADV_COLLAPSE from working on writable files. Best Regards, Yan, Zi
