From patchwork Fri Jun 3 05:37:31 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Shiyang Ruan X-Patchwork-Id: 12868550 Received: from heian.cn.fujitsu.com (mail.cn.fujitsu.com [183.91.158.132]) by smtp.subspace.kernel.org (Postfix) with ESMTP id BDB6EEA2 for ; Fri, 3 Jun 2022 05:37:57 +0000 (UTC) IronPort-Data: A9a23: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 IronPort-HdrOrdr: A9a23:EKLKZa1k3lNUWa/c9zVaBQqjBFQkLtp133Aq2lEZdPRUGvb4qynIpoVj6faUskdoZJhOo6HiBEDtexzhHNtOkO0s1NSZLW/bUQmTXeNfBOLZqlWKcUCTygce79YGT0EUMr3N5DZB4/oSmDPIdurI3uP3jJyAtKPPyWt3VwF2Z+VF5wd9MAySFUp7X2B9dOAEPavZ9sxavCChZHhSSsy6A0MOV+/Fq8aOu4nhZXc9dmMawTjLnTW186T7DhTd+h8fVglEybAk/XOAsyGR3NTZj82G X-IronPort-AV: E=Sophos;i="5.88,333,1635177600"; d="scan'208";a="124686808" Received: from unknown (HELO cn.fujitsu.com) ([10.167.33.5]) by heian.cn.fujitsu.com with ESMTP; 03 Jun 2022 13:37:51 +0800 Received: from G08CNEXMBPEKD05.g08.fujitsu.local (unknown [10.167.33.204]) by cn.fujitsu.com (Postfix) with ESMTP id 0D5D84D17199; Fri, 3 Jun 2022 13:37:47 +0800 (CST) Received: from G08CNEXJMPEKD02.g08.fujitsu.local (10.167.33.202) by G08CNEXMBPEKD05.g08.fujitsu.local (10.167.33.204) with Microsoft SMTP Server (TLS) id 15.0.1497.23; Fri, 3 Jun 2022 13:37:47 +0800 Received: from G08CNEXCHPEKD07.g08.fujitsu.local (10.167.33.80) by G08CNEXJMPEKD02.g08.fujitsu.local (10.167.33.202) with Microsoft SMTP Server (TLS) id 15.0.1497.23; Fri, 3 Jun 2022 13:37:47 +0800 Received: from irides.mr.mr (10.167.225.141) by G08CNEXCHPEKD07.g08.fujitsu.local (10.167.33.209) with Microsoft SMTP Server id 15.0.1497.23 via Frontend Transport; Fri, 3 Jun 2022 13:37:46 +0800 From: Shiyang Ruan To: , , , , CC: , , , , , , , , , , , Christoph Hellwig Subject: [PATCH v2 07/14] fsdax: set a CoW flag when associate reflink mappings Date: Fri, 3 Jun 2022 13:37:31 +0800 Message-ID: <20220603053738.1218681-8-ruansy.fnst@fujitsu.com> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220603053738.1218681-1-ruansy.fnst@fujitsu.com> References: <20220603053738.1218681-1-ruansy.fnst@fujitsu.com> Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-yoursite-MailScanner-ID: 0D5D84D17199.A4D5C X-yoursite-MailScanner: Found to be clean X-yoursite-MailScanner-From: ruansy.fnst@fujitsu.com X-Spam-Status: No Introduce a PAGE_MAPPING_DAX_COW flag to support association with CoW file mappings. In this case, since the dax-rmap has already took the responsibility to look up for shared files by given dax page, the page->mapping is no longer to used for rmap but for marking that this dax page is shared. And to make sure disassociation works fine, we use page->index as refcount, and clear page->mapping to the initial state when page->index is decreased to 0. With the help of this new flag, it is able to distinguish normal case and CoW case, and keep the warning in normal case. Signed-off-by: Shiyang Ruan Reviewed-by: Christoph Hellwig Reviewed-by: Darrick J. Wong --- fs/dax.c | 50 +++++++++++++++++++++++++++++++------- include/linux/page-flags.h | 6 +++++ 2 files changed, 47 insertions(+), 9 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 65e44d78b3bb..b59b864017ad 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -334,13 +334,35 @@ static unsigned long dax_end_pfn(void *entry) for (pfn = dax_to_pfn(entry); \ pfn < dax_end_pfn(entry); pfn++) +static inline bool dax_mapping_is_cow(struct address_space *mapping) +{ + return (unsigned long)mapping == PAGE_MAPPING_DAX_COW; +} + /* - * TODO: for reflink+dax we need a way to associate a single page with - * multiple address_space instances at different linear_page_index() - * offsets. + * Set the page->mapping with FS_DAX_MAPPING_COW flag, increase the refcount. + */ +static inline void dax_mapping_set_cow(struct page *page) +{ + if ((uintptr_t)page->mapping != PAGE_MAPPING_DAX_COW) { + /* + * Reset the index if the page was already mapped + * regularly before. + */ + if (page->mapping) + page->index = 1; + page->mapping = (void *)PAGE_MAPPING_DAX_COW; + } + page->index++; +} + +/* + * When it is called in dax_insert_entry(), the cow flag will indicate that + * whether this entry is shared by multiple files. If so, set the page->mapping + * FS_DAX_MAPPING_COW, and use page->index as refcount. */ static void dax_associate_entry(void *entry, struct address_space *mapping, - struct vm_area_struct *vma, unsigned long address) + struct vm_area_struct *vma, unsigned long address, bool cow) { unsigned long size = dax_entry_size(entry), pfn, index; int i = 0; @@ -352,9 +374,13 @@ static void dax_associate_entry(void *entry, struct address_space *mapping, for_each_mapped_pfn(entry, pfn) { struct page *page = pfn_to_page(pfn); - WARN_ON_ONCE(page->mapping); - page->mapping = mapping; - page->index = index + i++; + if (cow) { + dax_mapping_set_cow(page); + } else { + WARN_ON_ONCE(page->mapping); + page->mapping = mapping; + page->index = index + i++; + } } } @@ -370,7 +396,12 @@ static void dax_disassociate_entry(void *entry, struct address_space *mapping, struct page *page = pfn_to_page(pfn); WARN_ON_ONCE(trunc && page_ref_count(page) > 1); - WARN_ON_ONCE(page->mapping && page->mapping != mapping); + if (dax_mapping_is_cow(page->mapping)) { + /* keep the CoW flag if this page is still shared */ + if (page->index-- > 0) + continue; + } else + WARN_ON_ONCE(page->mapping && page->mapping != mapping); page->mapping = NULL; page->index = 0; } @@ -830,7 +861,8 @@ static void *dax_insert_entry(struct xa_state *xas, void *old; dax_disassociate_entry(entry, mapping, false); - dax_associate_entry(new_entry, mapping, vmf->vma, vmf->address); + dax_associate_entry(new_entry, mapping, vmf->vma, vmf->address, + false); /* * Only swap our new entry into the page cache if the current * entry is a zero page or an empty entry. If a normal PTE or diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index e66f7aa3191d..a5263a21b72f 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -650,6 +650,12 @@ __PAGEFLAG(Reported, reported, PF_NO_COMPOUND) #define PAGE_MAPPING_KSM (PAGE_MAPPING_ANON | PAGE_MAPPING_MOVABLE) #define PAGE_MAPPING_FLAGS (PAGE_MAPPING_ANON | PAGE_MAPPING_MOVABLE) +/* + * Different with flags above, this flag is used only for fsdax mode. It + * indicates that this page->mapping is now under reflink case. + */ +#define PAGE_MAPPING_DAX_COW 0x1 + static __always_inline bool folio_mapping_flags(struct folio *folio) { return ((unsigned long)folio->mapping & PAGE_MAPPING_FLAGS) != 0;