New tmpfs use of !PageUptodate pages for fallocate() is triggering the WARNING: at mm/page-writeback.c:1990 when __set_page_dirty_nobuffers() is called from migrate_page_copy() for compaction. It is anomalous that migration should use __set_page_dirty_nobuffers() on an address_space that does not participate in dirty and writeback accounting; and this has also been observed to insert surprising dirty tags into a tmpfs radix_tree, despite tmpfs not using tags at all. We should probably give migrate_page_copy() a better way to preserve the tag and migrate accounting info, when mapping_cap_account_dirty(). But that needs some more work: so in the interim, avoid the warning by using a simple SetPageDirty on PageSwapBacked pages. Reported-by: Dave Jones <davej@xxxxxxxxxx> Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> --- mm/migrate.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- 3.4.0+/mm/migrate.c 2012-05-27 10:01:43.104049010 -0700 +++ linux/mm/migrate.c 2012-06-01 00:10:58.080098749 -0700 @@ -436,7 +436,10 @@ void migrate_page_copy(struct page *newp * is actually a signal that all of the page has become dirty. * Whereas only part of our page may be dirty. */ - __set_page_dirty_nobuffers(newpage); + if (PageSwapBacked(page)) + SetPageDirty(newpage); + else + __set_page_dirty_nobuffers(newpage); } mlock_migrate_page(newpage, page); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>