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: Fri, 13 Apr 2018 16:40:20 +0800 Message-ID: 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> <5f22d645-001d-a132-f0bd-2dba1f6daaea@kernel.org> <558ea6b1-e57d-5910-d931-a47f143cca25@huawei.com> <3782ed9e-741d-d711-3937-bc8127566982@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <3782ed9e-741d-d711-3937-bc8127566982@kernel.org> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Jaegeuk Kim Cc: Chao Yu , linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org List-Id: linux-f2fs-devel.lists.sourceforge.net Ping again.. Do you have time to discuss this? On 2018/2/27 22:16, Chao Yu wrote: > Ping, > > On 2018/2/13 15:34, Chao Yu wrote: >> Hi Jaegeuk, >> >> On 2018/2/10 10:52, Chao Yu wrote: >>> 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? >> >> Do you have time to explain more about the design of multiple version structure >> for node block, I'm still be confused about two things: >> 1. what will we do if we want to add one new field in node structure. >> 2. how can we recognize which fields are valid and which ones are invalid. >> >> Thanks, >> >>> >>> 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 >>>>>>>> >>>>>>>> . >>>>>>>> >>> >>> . >>> >> > > . >