From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jaegeuk Kim Subject: Re: [PATCH 2/2] f2fs: support {d,id,did,x}node checksum Date: Fri, 9 Feb 2018 17:41:40 -0800 Message-ID: <20180210014140.GB1885@jaegeuk-macbookpro.roam.corp.google.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <55f144df-4419-3642-5b35-c8885cdb7354@kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: Chao Yu Cc: Chao Yu , linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org List-Id: linux-f2fs-devel.lists.sourceforge.net 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. > > 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 > >>> > >>> . > >>>