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Shuemov" , Ryan Roberts , Yang Shi , Yu Zhao Subject: [PATCH RESEND v3 1/2] mm/filemap: use xas_try_split() in __filemap_add_folio() Date: Fri, 14 Mar 2025 18:21:12 -0400 Message-ID: <20250314222113.711703-2-ziy@nvidia.com> X-Mailer: git-send-email 2.47.2 In-Reply-To: <20250314222113.711703-1-ziy@nvidia.com> References: <20250314222113.711703-1-ziy@nvidia.com> X-ClientProxiedBy: BLAP220CA0028.NAMP220.PROD.OUTLOOK.COM (2603:10b6:208:32c::33) To DS7PR12MB9473.namprd12.prod.outlook.com (2603:10b6:8:252::5) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS7PR12MB9473:EE_|PH7PR12MB9076:EE_ X-MS-Office365-Filtering-Correlation-Id: d13e0440-fadb-40e2-b10a-08dd63468eee X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|7416014|376014|1800799024; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DS7PR12MB9473.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(366016)(7416014)(376014)(1800799024);DIR:OUT;SFP:1101; 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Instead of splitting all n slots, only the m slots covered by the folio need to be split and the remaining n-m shadow entries can be retained with orders ranging from m to n-1. This method only requires (n/XA_CHUNK_SHIFT) - (m/XA_CHUNK_SHIFT) new xa_nodes instead of (n % XA_CHUNK_SHIFT) * ((n/XA_CHUNK_SHIFT) - (m/XA_CHUNK_SHIFT)) new xa_nodes, compared to the original xas_split_alloc() + xas_split() one. For example, to insert an order-0 folio when an order-9 shadow entry is present (assuming XA_CHUNK_SHIFT is 6), 1 xa_node is needed instead of 8. xas_try_split_min_order() is introduced to reduce the number of calls to xas_try_split() during split. Cc: Baolin Wang Cc: Hugh Dickins Cc: Kairui Song Cc: Miaohe Lin Cc: Mattew Wilcox Cc: David Hildenbrand Cc: John Hubbard Cc: Kefeng Wang Cc: Kirill A. Shuemov Cc: Ryan Roberts Cc: Yang Shi Cc: Yu Zhao Signed-off-by: Zi Yan --- include/linux/xarray.h | 7 +++++++ lib/xarray.c | 25 +++++++++++++++++++++++ mm/filemap.c | 45 +++++++++++++++++------------------------- 3 files changed, 50 insertions(+), 27 deletions(-) diff --git a/include/linux/xarray.h b/include/linux/xarray.h index 4010195201c9..78eede109b1a 100644 --- a/include/linux/xarray.h +++ b/include/linux/xarray.h @@ -1556,6 +1556,7 @@ int xas_get_order(struct xa_state *xas); void xas_split(struct xa_state *, void *entry, unsigned int order); void xas_split_alloc(struct xa_state *, void *entry, unsigned int order, gfp_t); void xas_try_split(struct xa_state *xas, void *entry, unsigned int order); +unsigned int xas_try_split_min_order(unsigned int order); #else static inline int xa_get_order(struct xarray *xa, unsigned long index) { @@ -1582,6 +1583,12 @@ static inline void xas_try_split(struct xa_state *xas, void *entry, unsigned int order) { } + +static inline unsigned int xas_try_split_min_order(unsigned int order) +{ + return 0; +} + #endif /** diff --git a/lib/xarray.c b/lib/xarray.c index 3bae48558e21..9644b18af18d 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -1134,6 +1134,28 @@ void xas_split(struct xa_state *xas, void *entry, unsigned int order) } EXPORT_SYMBOL_GPL(xas_split); +/** + * xas_try_split_min_order() - Minimal split order xas_try_split() can accept + * @order: Current entry order. + * + * xas_try_split() can split a multi-index entry to smaller than @order - 1 if + * no new xa_node is needed. This function provides the minimal order + * xas_try_split() supports. + * + * Return: the minimal order xas_try_split() supports + * + * Context: Any context. + * + */ +unsigned int xas_try_split_min_order(unsigned int order) +{ + if (order % XA_CHUNK_SHIFT == 0) + return order == 0 ? 0 : order - 1; + + return order - (order % XA_CHUNK_SHIFT); +} +EXPORT_SYMBOL_GPL(xas_try_split_min_order); + /** * xas_try_split() - Try to split a multi-index entry. * @xas: XArray operation state. @@ -1145,6 +1167,9 @@ EXPORT_SYMBOL_GPL(xas_split); * needed, the function will use GFP_NOWAIT to get one if xas->xa_alloc is * NULL. If more new xa_node are needed, the function gives EINVAL error. * + * NOTE: use xas_try_split_min_order() to get next split order instead of + * @order - 1 if you want to minmize xas_try_split() calls. + * * Context: Any context. The caller should hold the xa_lock. */ void xas_try_split(struct xa_state *xas, void *entry, unsigned int order) diff --git a/mm/filemap.c b/mm/filemap.c index 152993a86de3..cc69f174f76b 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -857,11 +857,10 @@ EXPORT_SYMBOL_GPL(replace_page_cache_folio); noinline int __filemap_add_folio(struct address_space *mapping, struct folio *folio, pgoff_t index, gfp_t gfp, void **shadowp) { - XA_STATE(xas, &mapping->i_pages, index); - void *alloced_shadow = NULL; - int alloced_order = 0; + XA_STATE_ORDER(xas, &mapping->i_pages, index, folio_order(folio)); bool huge; long nr; + unsigned int forder = folio_order(folio); VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); VM_BUG_ON_FOLIO(folio_test_swapbacked(folio), folio); @@ -870,7 +869,6 @@ noinline int __filemap_add_folio(struct address_space *mapping, mapping_set_update(&xas, mapping); VM_BUG_ON_FOLIO(index & (folio_nr_pages(folio) - 1), folio); - xas_set_order(&xas, index, folio_order(folio)); huge = folio_test_hugetlb(folio); nr = folio_nr_pages(folio); @@ -880,7 +878,7 @@ noinline int __filemap_add_folio(struct address_space *mapping, folio->index = xas.xa_index; for (;;) { - int order = -1, split_order = 0; + int order = -1; void *entry, *old = NULL; xas_lock_irq(&xas); @@ -898,21 +896,25 @@ noinline int __filemap_add_folio(struct address_space *mapping, order = xas_get_order(&xas); } - /* entry may have changed before we re-acquire the lock */ - if (alloced_order && (old != alloced_shadow || order != alloced_order)) { - xas_destroy(&xas); - alloced_order = 0; - } - if (old) { - if (order > 0 && order > folio_order(folio)) { + if (order > 0 && order > forder) { + unsigned int split_order = max(forder, + xas_try_split_min_order(order)); + /* How to handle large swap entries? */ BUG_ON(shmem_mapping(mapping)); - if (!alloced_order) { - split_order = order; - goto unlock; + + while (order > forder) { + xas_set_order(&xas, index, split_order); + xas_try_split(&xas, old, order); + if (xas_error(&xas)) + goto unlock; + order = split_order; + split_order = + max(xas_try_split_min_order( + split_order), + forder); } - xas_split(&xas, old, order); xas_reset(&xas); } if (shadowp) @@ -936,17 +938,6 @@ noinline int __filemap_add_folio(struct address_space *mapping, unlock: xas_unlock_irq(&xas); - /* split needed, alloc here and retry. */ - if (split_order) { - xas_split_alloc(&xas, old, split_order, gfp); - if (xas_error(&xas)) - goto error; - alloced_shadow = old; - alloced_order = split_order; - xas_reset(&xas); - continue; - } - if (!xas_nomem(&xas, gfp)) break; }