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Shutemov" , "Matthew Wilcox (Oracle)" Cc: Ryan Roberts , Hugh Dickins , David Hildenbrand , Yang Shi , Miaohe Lin , Kefeng Wang , Yu Zhao , John Hubbard , Baolin Wang , linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Zi Yan Subject: [PATCH v6 6/7] mm/truncate: use buddy allocator like folio split for truncate operation. 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For example, to truncate a order-4 folio [0, 1, 2, 3, 4, 5, ..., 15] between [3, 10] (inclusive), folio_split() splits the folio to [0,1], [2], [3], [4..7], [8..15] and [3], [4..7] can be dropped and [8..15] is kept with zeros in [8..10], then another folio_split() is done at 10, so [8..10] can be dropped. One possible optimization is to make folio_split() to split a folio based on a given range, like [3..10] above. But that complicates folio_split(), so it will be investigated when necessary. Signed-off-by: Zi Yan --- include/linux/huge_mm.h | 36 ++++++++++++++++++++++++++++++++++++ mm/huge_memory.c | 4 ++-- mm/truncate.c | 31 ++++++++++++++++++++++++++++++- 3 files changed, 68 insertions(+), 3 deletions(-) diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index e1bea54820ff..2bd181142b96 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -341,6 +341,36 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list, unsigned int new_order); int min_order_for_split(struct folio *folio); int split_folio_to_list(struct folio *folio, struct list_head *list); +bool uniform_split_supported(struct folio *folio, unsigned int new_order, + bool warns); +bool non_uniform_split_supported(struct folio *folio, unsigned int new_order, + bool warns); +int folio_split(struct folio *folio, unsigned int new_order, struct page *page, + struct list_head *list); +/* + * try_folio_split - try to split a @folio at @page using non uniform split. + * @folio: folio to be split + * @page: split to order-0 at the given page + * @list: store the after-split folios + * + * Try to split a @folio at @page using non uniform split to order-0, if + * non uniform split is not supported, fall back to uniform split. + * + * Return: 0: split is successful, otherwise split failed. + */ +static inline int try_folio_split(struct folio *folio, struct page *page, + struct list_head *list) +{ + int ret = min_order_for_split(folio); + + if (ret < 0) + return ret; + + if (!non_uniform_split_supported(folio, 0, false)) + return split_huge_page_to_list_to_order(&folio->page, list, + ret); + return folio_split(folio, ret, page, list); +} static inline int split_huge_page(struct page *page) { struct folio *folio = page_folio(page); @@ -533,6 +563,12 @@ static inline int split_folio_to_list(struct folio *folio, struct list_head *lis return 0; } +static inline int try_folio_split(struct folio *folio, struct page *page, + struct list_head *list) +{ + return 0; +} + static inline void deferred_split_folio(struct folio *folio, bool partially_mapped) {} #define split_huge_pmd(__vma, __pmd, __address) \ do { } while (0) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index dad6819901a8..06087c8d0931 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3534,7 +3534,7 @@ static int __split_unmapped_folio(struct folio *folio, int new_order, return ret; } -static bool non_uniform_split_supported(struct folio *folio, unsigned int new_order, +bool non_uniform_split_supported(struct folio *folio, unsigned int new_order, bool warns) { /* order-1 is not supported for anonymous THP. */ @@ -3567,7 +3567,7 @@ static bool non_uniform_split_supported(struct folio *folio, unsigned int new_or } /* See comments in non_uniform_split_supported() */ -static bool uniform_split_supported(struct folio *folio, unsigned int new_order, +bool uniform_split_supported(struct folio *folio, unsigned int new_order, bool warns) { if (folio_test_anon(folio) && new_order == 1) { diff --git a/mm/truncate.c b/mm/truncate.c index e922ceb66c44..6a1f5d21679c 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -178,6 +178,7 @@ bool truncate_inode_partial_folio(struct folio *folio, loff_t start, loff_t end) { loff_t pos = folio_pos(folio); unsigned int offset, length; + struct page *split_at, *split_at2; if (pos < start) offset = start - pos; @@ -207,8 +208,36 @@ bool truncate_inode_partial_folio(struct folio *folio, loff_t start, loff_t end) folio_invalidate(folio, offset, length); if (!folio_test_large(folio)) return true; - if (split_folio(folio) == 0) + + split_at = folio_page(folio, PAGE_ALIGN_DOWN(offset) / PAGE_SIZE); + split_at2 = folio_page(folio, + PAGE_ALIGN_DOWN(offset + length) / PAGE_SIZE); + + if (!try_folio_split(folio, split_at, NULL)) { + /* + * try to split at offset + length to make sure folios within + * the range can be dropped, especially to avoid memory waste + * for shmem truncate + */ + struct folio *folio2 = page_folio(split_at2); + + if (!folio_try_get(folio2)) + goto no_split; + + if (!folio_test_large(folio2)) + goto out; + + if (!folio_trylock(folio2)) + goto out; + + /* split result does not matter here */ + try_folio_split(folio2, split_at2, NULL); + folio_unlock(folio2); +out: + folio_put(folio2); +no_split: return true; + } if (folio_test_dirty(folio)) return false; truncate_inode_folio(folio->mapping, folio); -- 2.47.2