* Re: [PATCH v2] Ext4 documentation fixes. [not found] <CA+UE=SPyMXZUhHFm0KgvihPdaE=yH5ra6n1C4XhKgM6aGheo=A@mail.gmail.com> @ 2019-08-23 3:18 ` Theodore Y. Ts'o [not found] ` <71dfe444-3efb-5f1c-d8a1-bb0e98002fd1@mixmax.com> [not found] ` <DEDD6BA5-6E18-4ED6-9EF6-E11EDA593700@dilger.ca> 1 sibling, 1 reply; 5+ messages in thread From: Theodore Y. Ts'o @ 2019-08-23 3:18 UTC (permalink / raw) To: Ayush Ranjan Cc: Andreas Dilger, Jonathan Corbet, Ext4 Developers List, linux-doc, Linux Kernel Mailing List On Thu, Aug 15, 2019 at 09:11:51AM -0700, Ayush Ranjan wrote: > This commit aims to fix the following issues in ext4 documentation: > - Flexible block group docs said that the aim was to group block > metadata together instead of block group metadata. > - The documentation consistly uses "location" instead of "block number". > It is easy to confuse location to be an absolute offset on disk. Added > a line to clarify all location values are in terms of block numbers. > - Dirent2 docs said that the rec_len field is shortened instead of the > name_len field. > - Typo in bg_checksum description. > - Inode size is 160 bytes now, and hence i_extra_isize is now 32. > - Cluster size formula was incorrect, it did not include the +10 to > s_log_cluster_size value. > - Typo: there were two s_wtime_hi in the superblock struct. > - Superblock struct was outdated, added the new fields which were part > of s_reserved earlier. > - Multiple mount protection seems to be implemented in fs/ext4/mmp.c. > > Signed-off-by: Ayush Ranjan <ayushr2@illinois.edu> Fixed with one minor typo fix: > diff --git a/Documentation/filesystems/ext4/group_descr.rst > b/Documentation/filesystems/ext4/group_descr.rst > index 0f783ed88..feb5c613d 100644 > --- a/Documentation/filesystems/ext4/group_descr.rst > +++ b/Documentation/filesystems/ext4/group_descr.rst > @@ -100,7 +100,7 @@ The block group descriptor is laid out in ``struct > ext4_group_desc``. > - \_\_le16 > - bg\_checksum > - Group descriptor checksum; crc16(sb\_uuid+group+desc) if the > - RO\_COMPAT\_GDT\_CSUM feature is set, or crc32c(sb\_uuid+group\_desc) & > + RO\_COMPAT\_GDT\_CSUM feature is set, or crc32c(sb\_uuid+group+desc) & > 0xFFFF if the RO\_COMPAT\_METADATA\_CSUM feature is set. The correct checksum should be "crc16(sb\_uuid+group\_desc)" or "crc32c(sb\_uuid+group\_desc)". That is, it's previous line which needed modification. - Ted ^ permalink raw reply [flat|nested] 5+ messages in thread
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* Re: [PATCH v2] Ext4 documentation fixes. [not found] ` <71dfe444-3efb-5f1c-d8a1-bb0e98002fd1@mixmax.com> @ 2019-08-23 14:16 ` Theodore Y. Ts'o 0 siblings, 0 replies; 5+ messages in thread From: Theodore Y. Ts'o @ 2019-08-23 14:16 UTC (permalink / raw) To: Ayush Ranjan Cc: Andreas Dilger, Jonathan Corbet, Ext4 Developers List, linux-doc, Linux Kernel Mailing List On Fri, Aug 23, 2019 at 04:56:42AM +0000, Ayush Ranjan wrote: > Hey Ted! > Thanks for reviewing! The comment in fs/ext4/ext4.h:ext4_group_desc:bg_checksum > says that the crc16 checksum formula should be crc16(sb_uuid+group+desc). I > think group over here denotes group number. > > Briefly looking through fs/ext4/super.c:ext4_group_desc_csum() suggests that: > - For the new metadata_csum algorithm, only the group number and the block > descriptor are included in the checksum. So the formula should be > crc32c(group+desc) & 0xFFF (this looks like a bug as this should also include sb > UUID?) > - For the old crc16 algorithm, the sb UUID, group number and the block > descriptor are included in the checksum. So the formula should be > crc16(sb\_uuid+group+desc). (should remain unchanged) Thanks for the research and explanation. I think I'm going to change that to be: crc{16,32c}(sb_uuid + group_num + bg_desc) That should make it clearer what is meant. - Ted > > Ayush Ranjan > University of Illinois - Urbana Champaign | May 2020 > Bachelors of Science in Computer Science and Mathematics > Business Minor | Gies College of Business > > > On Fri, Aug 23, 2019 at 8:48 AM Theodore Y. Ts'o <tytso@mit.edu> wrote: > > > > On Thu, Aug 15, 2019 at 09:11:51AM -0700, Ayush Ranjan wrote: > > > This commit aims to fix the following issues in ext4 documentation: > > > - Flexible block group docs said that the aim was to group block > > > metadata together instead of block group metadata. > > > - The documentation consistly uses "location" instead of "block number". > > > It is easy to confuse location to be an absolute offset on disk. Added > > > a line to clarify all location values are in terms of block numbers. > > > - Dirent2 docs said that the rec_len field is shortened instead of the > > > name_len field. > > > - Typo in bg_checksum description. > > > - Inode size is 160 bytes now, and hence i_extra_isize is now 32. > > > - Cluster size formula was incorrect, it did not include the +10 to > > > s_log_cluster_size value. > > > - Typo: there were two s_wtime_hi in the superblock struct. > > > - Superblock struct was outdated, added the new fields which were part > > > of s_reserved earlier. > > > - Multiple mount protection seems to be implemented in fs/ext4/mmp.c. > > > > > > Signed-off-by: Ayush Ranjan <ayushr2@illinois.edu> > > > > Fixed with one minor typo fix: > > > > > diff --git a/Documentation/filesystems/ext4/group_descr.rst > > > b/Documentation/filesystems/ext4/group_descr.rst > > > index 0f783ed88..feb5c613d 100644 > > > --- a/Documentation/filesystems/ext4/group_descr.rst > > > +++ b/Documentation/filesystems/ext4/group_descr.rst > > > @@ -100,7 +100,7 @@ The block group descriptor is laid out in ``struct > > > ext4_group_desc``. > > > - \_\_le16 > > > - bg\_checksum > > > - Group descriptor checksum; crc16(sb\_uuid+group+desc) if the > > > - RO\_COMPAT\_GDT\_CSUM feature is set, or > crc32c(sb\_uuid+group\_desc) & > > > + RO\_COMPAT\_GDT\_CSUM feature is set, or crc32c(sb\_uuid+group+desc) > & > > > 0xFFFF if the RO\_COMPAT\_METADATA\_CSUM feature is set. > > > > The correct checksum should be "crc16(sb\_uuid+group\_desc)" or > > "crc32c(sb\_uuid+group\_desc)". That is, it's previous line which > > needed modification. > > > > - Ted ^ permalink raw reply [flat|nested] 5+ messages in thread
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* Re: [PATCH v2] Ext4 documentation fixes. [not found] ` <DEDD6BA5-6E18-4ED6-9EF6-E11EDA593700@dilger.ca> @ 2019-08-24 21:24 ` Jonathan Corbet 2019-08-24 23:09 ` Theodore Y. Ts'o 0 siblings, 1 reply; 5+ messages in thread From: Jonathan Corbet @ 2019-08-24 21:24 UTC (permalink / raw) To: Andreas Dilger Cc: Ayush Ranjan, Theodore Ts'o, Andreas Dilger, Ext4 Developers List, linux-doc, Linux Kernel Mailing List On Thu, 15 Aug 2019 09:16:23 -0700 Andreas Dilger <adilger@dilger.ca> wrote: > On Aug 15, 2019, at 09:11, Ayush Ranjan <ayushr2@illinois.edu> wrote: > > > > This commit aims to fix the following issues in ext4 documentation: > > - Flexible block group docs said that the aim was to group block > > metadata together instead of block group metadata. > > - The documentation consistly uses "location" instead of "block number". > > It is easy to confuse location to be an absolute offset on disk. Added > > a line to clarify all location values are in terms of block numbers. > > - Dirent2 docs said that the rec_len field is shortened instead of the > > name_len field. > > - Typo in bg_checksum description. > > - Inode size is 160 bytes now, and hence i_extra_isize is now 32. > > - Cluster size formula was incorrect, it did not include the +10 to > > s_log_cluster_size value. > > - Typo: there were two s_wtime_hi in the superblock struct. > > - Superblock struct was outdated, added the new fields which were part > > of s_reserved earlier. > > - Multiple mount protection seems to be implemented in fs/ext4/mmp.c. > > > > Signed-off-by: Ayush Ranjan <ayushr2@illinois.edu> > > Reviewed-by: Andreas Dilger <adilger@dilger.ca> I've applied this to the docs tree. However, Ayush: the patch was rather badly corrupted by your mail client. I managed to fix it up, but please in the future verify that you can email a patch to yourself and apply it before submitting it. There may be some useful hints in Documentation/process/email-clients.rst . Thanks, jon ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] Ext4 documentation fixes. 2019-08-24 21:24 ` Jonathan Corbet @ 2019-08-24 23:09 ` Theodore Y. Ts'o 2019-08-25 14:42 ` Jonathan Corbet 0 siblings, 1 reply; 5+ messages in thread From: Theodore Y. Ts'o @ 2019-08-24 23:09 UTC (permalink / raw) To: Jonathan Corbet Cc: Andreas Dilger, Ayush Ranjan, Andreas Dilger, Ext4 Developers List, linux-doc, Linux Kernel Mailing List On Sat, Aug 24, 2019 at 03:24:53PM -0600, Jonathan Corbet wrote: > I've applied this to the docs tree. > > However, Ayush: the patch was rather badly corrupted by your mail client. > I managed to fix it up, but please in the future verify that you can email > a patch to yourself and apply it before submitting it. There may be some > useful hints in Documentation/process/email-clients.rst . Hi Jon, If you haven't pushed out your doc tree, can you please drop it? I've already applied an (improved) version of this patch to the ext4 tree, and I actually have some plans to do further fixups of ext4 on-disk format documentation in the ext4 tree. So it would be easier if we keep ext4 documentation updates in the ext4 git tree. Thanks, - Ted ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] Ext4 documentation fixes. 2019-08-24 23:09 ` Theodore Y. Ts'o @ 2019-08-25 14:42 ` Jonathan Corbet 0 siblings, 0 replies; 5+ messages in thread From: Jonathan Corbet @ 2019-08-25 14:42 UTC (permalink / raw) To: Theodore Y. Ts'o Cc: Andreas Dilger, Ayush Ranjan, Andreas Dilger, Ext4 Developers List, linux-doc, Linux Kernel Mailing List On Sat, 24 Aug 2019 19:09:30 -0400 "Theodore Y. Ts'o" <tytso@mit.edu> wrote: > If you haven't pushed out your doc tree, can you please drop it? I've > already applied an (improved) version of this patch to the ext4 tree, > and I actually have some plans to do further fixups of ext4 on-disk > format documentation in the ext4 tree. So it would be easier if we > keep ext4 documentation updates in the ext4 git tree. Sigh...I checked linux-next first and saw no signs of activity there. Oh well; I guess I can disappear that change. jon ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2019-08-25 14:42 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- [not found] <CA+UE=SPyMXZUhHFm0KgvihPdaE=yH5ra6n1C4XhKgM6aGheo=A@mail.gmail.com> 2019-08-23 3:18 ` [PATCH v2] Ext4 documentation fixes Theodore Y. Ts'o [not found] ` <71dfe444-3efb-5f1c-d8a1-bb0e98002fd1@mixmax.com> 2019-08-23 14:16 ` Theodore Y. Ts'o [not found] ` <DEDD6BA5-6E18-4ED6-9EF6-E11EDA593700@dilger.ca> 2019-08-24 21:24 ` Jonathan Corbet 2019-08-24 23:09 ` Theodore Y. Ts'o 2019-08-25 14:42 ` Jonathan Corbet
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