From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chao Yu Subject: Re: [PATCH 2/2] f2fs: support {d,id,did,x}node checksum Date: Sat, 10 Feb 2018 10:52:18 +0800 Message-ID: <5f22d645-001d-a132-f0bd-2dba1f6daaea@kernel.org> References: <20180127094301.29154-1-yuchao0@huawei.com> <20180127094301.29154-2-yuchao0@huawei.com> <20180131020213.GA86468@jaegeuk-macbookpro.roam.corp.google.com> <20180131221531.GC12901@jaegeuk-macbookpro.roam.corp.google.com> <55f144df-4419-3642-5b35-c8885cdb7354@kernel.org> <20180210014140.GB1885@jaegeuk-macbookpro.roam.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from sfi-mx-3.v28.ch3.sourceforge.com ([172.29.28.193] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1ekLHL-0006kQ-Sj for linux-f2fs-devel@lists.sourceforge.net; Sat, 10 Feb 2018 02:52:39 +0000 Received: from mail.kernel.org ([198.145.29.99]) by sfi-mx-3.v28.ch3.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) id 1ekLHK-00014W-Sn for linux-f2fs-devel@lists.sourceforge.net; Sat, 10 Feb 2018 02:52:39 +0000 In-Reply-To: <20180210014140.GB1885@jaegeuk-macbookpro.roam.corp.google.com> Content-Language: en-US List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net To: Jaegeuk Kim Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net On 2018/2/10 9:41, Jaegeuk Kim wrote: > On 02/01, Chao Yu wrote: >> >> >> On 2018/2/1 6:15, Jaegeuk Kim wrote: >>> On 01/31, Chao Yu wrote: >>>> On 2018/1/31 10:02, Jaegeuk Kim wrote: >>>>> What if we want to add more entries in addition to node_checksum? Do we have >>>>> to add a new feature flag at every time? How about adding a layout value instead >>>> >>>> Hmm.. for previous implementation, IMO, we'd better add a new feature flag at >>>> every time, otherwise, w/ extra_nsize only, in current image, we can know a >>>> valid range of extended area in node block, but we don't know which >>>> fields/features are valid/enabled or not. >>>> >>>> One more thing is that if we can add one feature flag for each field, we got one >>>> more chance to disable it dynamically. >>>> >>>>> of extra_nsize? For example, layout #1 means node_checksum with extra_nsize=X? >>>>> >>>>> >>>>> What does 1017 mean? We need to make this structure more flexibly for new >>>> >>>> Yes, using raw 1017 is not appropriate here. >>>> >>>>> entries. Like this? >>>>> union { >>>>> struct node_v1; >>>>> struct node_v2; >>>>> struct node_v3; >>>>> ... >>>>> struct direct_node dn; >>>>> struct indirect_node in; >>>>> }; >>>>> }; >>>>> >>>>> struct node_v1 { >>>>> __le32 data[DEF_ADDRS_PER_BLOCK - V1_NSIZE=1]; >>>>> __le32 node_checksum; >>>>> } >>>>> >>>>> struct node_v2 { >>>>> __le32 data[DEF_ADDRS_PER_BLOCK - V2_NSIZE=500]; >>>> >>>> Hmm.. If we only need to add one more 4 bytes field in struct node_v2, but >>>> V2_NSIZE is defined as fixed 500, there must be 492 bytes wasted. >>>> >>>> Or we can define V2_NSIZE as 8, but if there comes more and more extended >>>> fields, node version count can be a large number, it results in complicated >>>> version recognization and handling. >>>> >>>> One more question is how can we control which fields are valid or not in >>>> comp[Vx_NSIZE]? >>>> >>>> >>>> Anyway, what I'm thinking is maybe we can restructure layout of node block like >>>> the one used by f2fs_inode: >>>> >>>> struct f2fs_node { >>>> union { >>>> struct f2fs_inode i; >>>> union { >>>> struct { >>>> __le32 node_checksum; >>>> __le32 feature_field_1; >>>> __le32 feature_field_2; >>>> .... >>>> __le32 addr[]; >>>> >>>> }; >>>> struct direct_node dn; >>>> struct indirect_node in; >>>> }; >>>> }; >>>> struct node_footer footer; >>>> } __packed; >>>> >>>> Moving all extended fields to the head of f2fs_node, so we don't have to use >>>> macro to indicate actual size of addr. >>> >>> Thinking what'd be the best way. My concern is, once getting more entries, we >> >> OK, I think we need more discussion.. ;) >> >>> can't set each of features individually. Like the second entry should have >> >> Oh, that will be hard. If we have to avoid that, we have to tag in somewhere >> e.g. f2fs_inode::i_flags2 to indicate which new field in f2fs_node is valid, for >> example: >> >> #define F2FS_NODE_CHECKSUM 0x0001 >> #define F2FS_NODE_FIELD1 0x0002 >> #define F2FS_NODE_FIELD2 0x0004 >> >> union { >> struct { >> __le32 node_checksum; >> __le32 field_1; >> __le32 field_2; >> .... >> __le32 addr[]; >> }; >> struct direct_node dn; >> struct indirect_node in; >> }; >> >> f2fs_inode::i_flags2 = F2FS_NODE_CHECKSUM | F2FS_NODE_FIELD1 >> indicates that f2fs_node::node_checksum and f2fs_node::field_1 are valid; >> >> f2fs_inode::i_flags2 = F2FS_NODE_FIELD1 | F2FS_NODE_FIELD2 >> indicates that f2fs_node::field_1 and f2fs_node::field_2 are valid. > > So, that's why I thought we may need a sort of each formats. Hmm.. if we have two new added fields, there are (2 << 2) combinations of all formats, as: struct original { __le32 data[DEF_ADDRS_PER_BLOCK]; } struct node_v1 { __le32 data[DEF_ADDRS_PER_BLOCK - V1_NSIZE=1]; __le32 field_1; } struct node_v2 { __le32 data[DEF_ADDRS_PER_BLOCK - V2_NSIZE=1]; __le32 field_2; } struct node_v2 { __le32 data[DEF_ADDRS_PER_BLOCK - V3_NSIZE=2]; __le32 field_1; __le32 field_2; } If we add more new fields, the node version will increase sharply due to there is (n << 2) combination with n fields. Right? Any thoughts to reduce maintaining overhead on those node versions structures? Thanks, > >> >> Any thoughts? >> >> Thanks, >> >>> enabled node_checksum, which we may not want to do. >>> >>>> >>>> Thanks, >>>> >>>>> __le32 comp[V2_NSIZE]; >>>>> } >>>>> ... >>>>> >>>>>> + }; >>>>>> + struct direct_node dn; >>>>>> + struct indirect_node in; >>>>>> + }; >>>>>> }; >>>>>> struct node_footer footer; >>>>>> } __packed; >>>>>> -- >>>>>> 2.15.0.55.gc2ece9dc4de6 >>>>> >>>>> . >>>>> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot