From: "Matthew Wilcox (Oracle)" willy@infradead.org
mainline inclusion from mainline-v6.9-rc1 commit 8897277acfef7f70fdecc054073bea2542fc7a1b category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I9OCYO CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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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... Link: https://lkml.kernel.org/r/20240226205534.1603748-3-zi.yan@sent.com Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org Signed-off-by: Zi Yan ziy@nvidia.com Cc: David Hildenbrand david@redhat.com Cc: Hugh Dickins hughd@google.com Cc: Kirill A. Shutemov kirill.shutemov@linux.intel.com Cc: Luis Chamberlain mcgrof@kernel.org Cc: Michal Koutny mkoutny@suse.com Cc: Roman Gushchin roman.gushchin@linux.dev Cc: Ryan Roberts ryan.roberts@arm.com Cc: Yang Shi shy828301@gmail.com Cc: Yu Zhao yuzhao@google.com Cc: Zach O'Keefe zokeefe@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Liu Shixin liushixin2@huawei.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 058d79840bc7..7bbe26aa9cc8 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1940,8 +1940,6 @@ 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 21ec24a6658b..700bb6146600 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -792,8 +792,10 @@ 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); }
@@ -2981,7 +2983,8 @@ 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); } @@ -3032,6 +3035,9 @@ 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 @@ -3057,7 +3063,12 @@ 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 28085201b863..f2e7972d4a3e 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -512,8 +512,7 @@ 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 f79eb574055c..5464f0bee669 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -528,9 +528,6 @@ 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;