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Fri, 23 Jan 2026 14:47:57 +0800 (CST) Received: from kwepemr500001.china.huawei.com (unknown [7.202.194.229]) by mail.maildlp.com (Postfix) with ESMTPS id F302A40565; Fri, 23 Jan 2026 14:51:22 +0800 (CST) Received: from [10.174.179.179] (10.174.179.179) by kwepemr500001.china.huawei.com (7.202.194.229) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Fri, 23 Jan 2026 14:51:22 +0800 Message-ID: Date: Fri, 23 Jan 2026 14:51:21 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] mm/khugepaged: free empty xa_nodes when rollbacks in collapse_file To: Matthew Wilcox CC: , , , , , , , , , , , , , , References: <20260121062243.1893129-1-tujinjiang@huawei.com> From: Jinjiang Tu In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.179] X-ClientProxiedBy: kwepems100001.china.huawei.com (7.221.188.238) To kwepemr500001.china.huawei.com (7.202.194.229) X-Rspamd-Queue-Id: 3975EA0007 X-Stat-Signature: mi7zqacx1eiba18m5xgciajk41ktfqc5 X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1769151088-66887 X-HE-Meta: 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 wTcAoAu0 YaMXkyq8AMDErvr81/uycjgsJrhU6goAfz1PMSFtT7ZWPfRExqFLxHRMXdpDpazdB3+BRKWicb7+wdToUbzj/uYQZ977nXYOld9jUo9wCh1EL0zpj5zJ0aYaSCIPlYuWspr/iwDmSsTHFi8MCuvk3OK7CUsykHi0sYldC7dzpscA/1D1URq8eOSxf9vRKQ4bWG2MbmaQ20Es8XcT4wtmRf3YQdJEXtlzhXjBA0lDje3LfN3a2s0HzaG6MQgTBnIFQx9A+OngGy06RM5KipU45l4RxkSP59yAbMn18I+UIqAcXLFjkjXiJE/aXW6wsNbrk5fiMtyMLPnR9K66Rqj7CHsfIEU1/gECrpYS+hBwTTBdmi9pNpqZSNKdK8ltjx2Hi+uO6 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 在 2026/1/21 14:38, Matthew Wilcox 写道: > On Wed, Jan 21, 2026 at 02:22:43PM +0800, Jinjiang Tu wrote: >> collapse_file() calls xas_create_range() to pre-create all slots needed. >> If collapse_file() finally fails, these pre-created slots are empty nodes >> and aren't destroyed. > try this instead > > diff --git a/fs/inode.c b/fs/inode.c > index cff1d3af0d57..85886af1e7ab 100644 > --- a/fs/inode.c > +++ b/fs/inode.c > @@ -744,22 +744,18 @@ void dump_mapping(const struct address_space *mapping) > > void clear_inode(struct inode *inode) > { > - /* > - * We have to cycle the i_pages lock here because reclaim can be in the > - * process of removing the last page (in __filemap_remove_folio()) > - * and we must not free the mapping under it. > - */ > - xa_lock_irq(&inode->i_data.i_pages); > - BUG_ON(inode->i_data.nrpages); > /* > * Almost always, mapping_empty(&inode->i_data) here; but there are > * two known and long-standing ways in which nodes may get left behind > * (when deep radix-tree node allocation failed partway; or when THP > - * collapse_file() failed). Until those two known cases are cleaned up, > - * or a cleanup function is called here, do not BUG_ON(!mapping_empty), > - * nor even WARN_ON(!mapping_empty). > + * collapse_file() failed). > + * > + * xa_destroy() also cycles the lock for us, which is needed because > + * reclaim can be in the process of removing the last folio (in > + * __filemap_remove_folio()) and we must not free the mapping under it. > */ > - xa_unlock_irq(&inode->i_data.i_pages); > + xa_destroy(&inode->i_data.i_pages); > + BUG_ON(inode->i_data.nrpages); > BUG_ON(!list_empty(&inode->i_data.i_private_list)); > BUG_ON(!(inode->i_state & I_FREEING)); > BUG_ON(inode->i_state & I_CLEAR); Hi, Matthew This appoach is much simpler. Could you please send a formal patch?