On Fri, Apr 26, 2024 at 04:46:11PM -0700, Luis Chamberlain wrote: > On Thu, Apr 25, 2024 at 05:47:28PM -0700, Luis Chamberlain wrote: > > On Thu, Apr 25, 2024 at 09:10:16PM +0100, Matthew Wilcox wrote: > > > On Thu, Apr 25, 2024 at 01:37:40PM +0200, Pankaj Raghav (Samsung) wrote: > > > > From: Pankaj Raghav <p.raghav@xxxxxxxxxxx> > > > > > > > > using that API for LBS is resulting in an NULL ptr dereference > > > > error in the writeback path [1]. > > > > > > > > [1] https://gist.github.com/mcgrof/d12f586ec6ebe32b2472b5d634c397df > > > > > > How would I go about reproducing this? Well so the below fixes this but I am not sure if this is correct. folio_mark_dirty() at least says that a folio should not be truncated while its running. I am not sure if we should try to split folios then even though we check for writeback once. truncate_inode_partial_folio() will folio_wait_writeback() but it will split_folio() before checking for claiming to fail to truncate with folio_test_dirty(). But since the folio is locked its not clear why this should be possible. diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 83955362d41c..90195506211a 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3058,7 +3058,7 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list, if (new_order >= folio_order(folio)) return -EINVAL; - if (folio_test_writeback(folio)) + if (folio_test_dirty(folio) || folio_test_writeback(folio)) return -EBUSY; if (!folio_test_anon(folio)) {
