From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> 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/ Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> --- include/linux/huge_mm.h | 7 +++++-- mm/filemap.c | 2 -- mm/huge_memory.c | 23 ++++++++++++++++++----- mm/internal.h | 4 +--- mm/readahead.c | 3 --- 5 files changed, 24 insertions(+), 15 deletions(-) diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index 5adb86af35fc..916a2a539517 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -263,7 +263,7 @@ unsigned long thp_vma_allowable_orders(struct vm_area_struct *vma, unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags); -void folio_prep_large_rmappable(struct folio *folio); +struct folio *folio_prep_large_rmappable(struct folio *folio); bool can_split_folio(struct folio *folio, int *pextra_pins); int split_huge_page_to_list(struct page *page, struct list_head *list); static inline int split_huge_page(struct page *page) @@ -410,7 +410,10 @@ static inline unsigned long thp_vma_allowable_orders(struct vm_area_struct *vma, return 0; } -static inline void folio_prep_large_rmappable(struct folio *folio) {} +static inline struct folio *folio_prep_large_rmappable(struct folio *folio) +{ + return folio; +} #define transparent_hugepage_flags 0UL diff --git a/mm/filemap.c b/mm/filemap.c index 7a6e15c47150..c8205a534532 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1922,8 +1922,6 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index, gfp_t alloc_gfp = gfp; err = -ENOMEM; - if (order == 1) - order = 0; if (order < min_order) order = min_order; if (order > 0) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index d897efc51025..6ec3417638a1 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -788,11 +788,15 @@ struct deferred_split *get_deferred_split_queue(struct folio *folio) } #endif -void folio_prep_large_rmappable(struct folio *folio) +struct folio *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 folio; + if (folio_order(folio) > 1) + INIT_LIST_HEAD(&folio->_deferred_list); folio_set_large_rmappable(folio); + + return folio; } static inline bool is_transparent_hugepage(struct folio *folio) @@ -3095,7 +3099,8 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) /* 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); } @@ -3146,6 +3151,9 @@ void folio_undo_large_rmappable(struct folio *folio) 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 @@ -3171,7 +3179,12 @@ void deferred_split_folio(struct folio *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, diff --git a/mm/internal.h b/mm/internal.h index f309a010d50f..5174b5b0c344 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -419,9 +419,7 @@ static inline struct folio *page_rmappable_folio(struct page *page) { struct folio *folio = (struct folio *)page; - if (folio && folio_order(folio) > 1) - folio_prep_large_rmappable(folio); - return folio; + return folio_prep_large_rmappable(folio); } static inline void prep_compound_head(struct page *page, unsigned int order) diff --git a/mm/readahead.c b/mm/readahead.c index a361fba18674..7d5f6a8792a8 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -560,9 +560,6 @@ void page_cache_ra_order(struct readahead_control *ractl, /* Don't allocate pages past EOF */ while (order > min_order && index + (1UL << order) - 1 > limit) order--; - /* THP machinery does not support order-1 */ - if (order == 1) - order = 0; if (order < min_order) order = min_order; -- 2.43.0
