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Shuemov" , Ryan Roberts , Yang Shi , Yu Zhao Subject: [PATCH v3 1/2] mm/filemap: use xas_try_split() in __filemap_add_folio() Date: Wed, 26 Feb 2025 16:08:53 -0500 Message-ID: <20250226210854.2045816-2-ziy@nvidia.com> X-Mailer: git-send-email 2.47.2 In-Reply-To: <20250226210854.2045816-1-ziy@nvidia.com> References: <20250226210854.2045816-1-ziy@nvidia.com> X-ClientProxiedBy: MN2PR14CA0007.namprd14.prod.outlook.com (2603:10b6:208:23e::12) To DS7PR12MB9473.namprd12.prod.outlook.com (2603:10b6:8:252::5) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS7PR12MB9473:EE_|SA1PR12MB7221:EE_ X-MS-Office365-Filtering-Correlation-Id: 97cebf45-10c6-44ee-1896-08dd56a9c9b8 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|7416014|1800799024|7053199007; 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)(376014)(7416014)(1800799024)(7053199007);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. Signed-off-by: Zi Yan 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 --- 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 bc197c96d171..8067182d3e43 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -1133,6 +1133,28 @@ 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. @@ -1144,6 +1166,9 @@ 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 2b860b59a521..cfb49ed659a1 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; }