From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> commit 8897277acfef7f70fdecc054073bea2542fc7a1b upstream. Folios of order 1 have no space to store the deferred list. This is not a problem for the page cache as file-backed folios are never placed on the deferred list. All we need to do is prevent the core MM from touching the deferred list for order 1 folios and remove the code which prevented us from allocating order 1 folios. Link: https://lore.kernel.org/linux-mm/90344ea7-4eec-47ee-5996-0c22f42d6a6a@xxxxxxxxxx/ Link: https://lkml.kernel.org/r/20240226205534.1603748-3-zi.yan@xxxxxxxx Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx> Cc: Michal Koutny <mkoutny@xxxxxxxx> Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx> Cc: Ryan Roberts <ryan.roberts@xxxxxxx> Cc: Yang Shi <shy828301@xxxxxxxxx> Cc: Yu Zhao <yuzhao@xxxxxxxxxx> Cc: Zach O'Keefe <zokeefe@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/filemap.c | 2 -- mm/huge_memory.c | 19 +++++++++++++++---- mm/internal.h | 3 +-- mm/readahead.c | 3 --- 4 files changed, 16 insertions(+), 11 deletions(-) --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1957,8 +1957,6 @@ no_page: gfp_t alloc_gfp = gfp; err = -ENOMEM; - if (order == 1) - order = 0; if (order > 0) alloc_gfp |= __GFP_NORETRY | __GFP_NOWARN; folio = filemap_alloc_folio(alloc_gfp, order); --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -569,8 +569,10 @@ struct deferred_split *get_deferred_spli void folio_prep_large_rmappable(struct folio *folio) { - VM_BUG_ON_FOLIO(folio_order(folio) < 2, folio); - INIT_LIST_HEAD(&folio->_deferred_list); + if (!folio || !folio_test_large(folio)) + return; + if (folio_order(folio) > 1) + INIT_LIST_HEAD(&folio->_deferred_list); folio_set_large_rmappable(folio); } @@ -2720,7 +2722,8 @@ int split_huge_page_to_list(struct page /* Prevent deferred_split_scan() touching ->_refcount */ spin_lock(&ds_queue->split_queue_lock); if (folio_ref_freeze(folio, 1 + extra_pins)) { - if (!list_empty(&folio->_deferred_list)) { + if (folio_order(folio) > 1 && + !list_empty(&folio->_deferred_list)) { ds_queue->split_queue_len--; list_del(&folio->_deferred_list); } @@ -2771,6 +2774,9 @@ void folio_undo_large_rmappable(struct f struct deferred_split *ds_queue; unsigned long flags; + if (folio_order(folio) <= 1) + return; + /* * At this point, there is no one trying to add the folio to * deferred_list. If folio is not in deferred_list, it's safe @@ -2796,7 +2802,12 @@ void deferred_split_folio(struct folio * #endif unsigned long flags; - VM_BUG_ON_FOLIO(folio_order(folio) < 2, folio); + /* + * Order 1 folios have no space for a deferred list, but we also + * won't waste much memory by not adding them to the deferred list. + */ + if (folio_order(folio) <= 1) + return; /* * The try_to_unmap() in page reclaim path might reach here too, --- a/mm/internal.h +++ b/mm/internal.h @@ -419,8 +419,7 @@ static inline struct folio *page_rmappab { struct folio *folio = (struct folio *)page; - if (folio && folio_order(folio) > 1) - folio_prep_large_rmappable(folio); + folio_prep_large_rmappable(folio); return folio; } --- a/mm/readahead.c +++ b/mm/readahead.c @@ -519,9 +519,6 @@ void page_cache_ra_order(struct readahea /* Don't allocate pages past EOF */ while (index + (1UL << order) - 1 > limit) order--; - /* THP machinery does not support order-1 */ - if (order == 1) - order = 0; err = ra_alloc_folio(ractl, index, mark, order, gfp); if (err) break; Patches currently in stable-queue which might be from willy@xxxxxxxxxxxxx are queue-6.6/mm-support-order-1-folios-in-the-page-cache.patch queue-6.6/mm-always-initialise-folio-_deferred_list.patch queue-6.6/mm-refactor-folio_undo_large_rmappable.patch queue-6.6/mm-thp-fix-deferred-split-unqueue-naming-and-locking.patch queue-6.6/mm-add-page_rmappable_folio-wrapper.patch queue-6.6/mm-readahead-do-not-allow-order-1-folio.patch
