From: "Matthew Wilcox (Oracle)" willy@infradead.org
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@google... Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org Signed-off-by: Zi Yan ziy@nvidia.com --- mm/filemap.c | 2 -- mm/huge_memory.c | 19 +++++++++++++++---- mm/internal.h | 3 +-- mm/readahead.c | 3 --- 4 files changed, 16 insertions(+), 11 deletions(-)
diff --git a/mm/filemap.c b/mm/filemap.c index b7a21551fbc7..b4858d89f1b1 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1912,8 +1912,6 @@ 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 > 0) alloc_gfp |= __GFP_NORETRY | __GFP_NOWARN; folio = filemap_alloc_folio(alloc_gfp, order); diff --git a/mm/huge_memory.c b/mm/huge_memory.c index b20e535e874c..9840f312c08f 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -790,8 +790,10 @@ struct deferred_split *get_deferred_split_queue(struct folio *folio)
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); }
@@ -3114,7 +3116,8 @@ 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); } @@ -3165,6 +3168,9 @@ 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 @@ -3190,7 +3196,12 @@ 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 2b7efffbe4d7..c4853ebfa030 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -420,8 +420,7 @@ 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); + folio_prep_large_rmappable(folio); return folio; }
diff --git a/mm/readahead.c b/mm/readahead.c index 1e74455f908e..130c0e7df99f 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -514,9 +514,6 @@ void page_cache_ra_order(struct readahead_control *ractl, /* 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;