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Shuemov" , Ryan Roberts , Yang Shi , Yu Zhao Subject: [PATCH RESEND v3 2/2] mm/shmem: use xas_try_split() in shmem_split_large_entry() Date: Fri, 14 Mar 2025 18:21:13 -0400 Message-ID: <20250314222113.711703-3-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: BLAP220CA0016.NAMP220.PROD.OUTLOOK.COM (2603:10b6:208:32c::21) 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: 1d2b7342-8ed7-4ce9-c9d5-08dd63468fb2 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 1 slot covered by the folio need to be split and the remaining n-1 shadow entries can be retained with orders ranging from 0 to n-1. This method only requires (n/XA_CHUNK_SHIFT) new xa_nodes instead of (n % XA_CHUNK_SHIFT) * (n/XA_CHUNK_SHIFT) new xa_nodes, compared to the original xas_split_alloc() + xas_split() one. For example, to split an order-9 large swap entry (assuming XA_CHUNK_SHIFT is 6), 1 xa_node is needed instead of 8. xas_try_split_min_order() is used to reduce the number of calls to xas_try_split() during split. Cc: Baolin Wang Cc: Hugh Dickins Cc: Kairui Song Cc: Mattew Wilcox Cc: Miaohe Lin Cc: David Hildenbrand Cc: John Hubbard Cc: Kefeng Wang Cc: Kirill A. Shuemov Cc: Ryan Roberts Cc: Yang Shi Cc: Yu Zhao Reviewed-by: Baolin Wang Tested-by: Baolin Wang Signed-off-by: Zi Yan --- mm/shmem.c | 59 ++++++++++++++++++++++++++---------------------------- 1 file changed, 28 insertions(+), 31 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index 5586903950b3..7b738d8d6581 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2153,15 +2153,16 @@ static int shmem_split_large_entry(struct inode *inode, pgoff_t index, { struct address_space *mapping = inode->i_mapping; XA_STATE_ORDER(xas, &mapping->i_pages, index, 0); - void *alloced_shadow = NULL; - int alloced_order = 0, i; + int split_order = 0, entry_order; + int i; /* Convert user data gfp flags to xarray node gfp flags */ gfp &= GFP_RECLAIM_MASK; for (;;) { - int order = -1, split_order = 0; void *old = NULL; + int cur_order; + pgoff_t swap_index; xas_lock_irq(&xas); old = xas_load(&xas); @@ -2170,60 +2171,56 @@ static int shmem_split_large_entry(struct inode *inode, pgoff_t index, goto unlock; } - order = xas_get_order(&xas); + entry_order = xas_get_order(&xas); - /* Swap 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 (!entry_order) + goto unlock; /* Try to split large swap entry in pagecache */ - if (order > 0) { - if (!alloced_order) { - split_order = order; + cur_order = entry_order; + swap_index = round_down(index, 1 << entry_order); + + split_order = xas_try_split_min_order(cur_order); + + while (cur_order > 0) { + pgoff_t aligned_index = + round_down(index, 1 << cur_order); + pgoff_t swap_offset = aligned_index - swap_index; + + xas_set_order(&xas, index, split_order); + xas_try_split(&xas, old, cur_order); + if (xas_error(&xas)) goto unlock; - } - xas_split(&xas, old, order); /* * Re-set the swap entry after splitting, and the swap * offset of the original large entry must be continuous. */ - for (i = 0; i < 1 << order; i++) { - pgoff_t aligned_index = round_down(index, 1 << order); + for (i = 0; i < 1 << cur_order; + i += (1 << split_order)) { swp_entry_t tmp; - tmp = swp_entry(swp_type(swap), swp_offset(swap) + i); + tmp = swp_entry(swp_type(swap), + swp_offset(swap) + swap_offset + + i); __xa_store(&mapping->i_pages, aligned_index + i, swp_to_radix_entry(tmp), 0); } + cur_order = split_order; + split_order = xas_try_split_min_order(split_order); } 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; } -error: if (xas_error(&xas)) return xas_error(&xas); - return alloced_order; + return entry_order; } /*