c6464d3f99
[PITFALLS] There are several hidden pitfalls of the existing traverse_directory(): - Hand written preorder traversal There is already a better written standard library function, nftw() doing exactly what we need. - Over-designed path list To properly handle the directory change, we have structure directory_name_entry, to record every inode until rootdir. But it has two string members, dir_name and path, which is a little confusing and overkilled. As for preorder traversal, we will never need to read the parent's filename, just its btrfs inode number. And it's exported while no one utilizes it out of mkfs/rootdir.c. - Weird inode numbers We use the inode number from st->st_ino, with an extra offset. This by itself is not safe, if the rootdir has child directories in another filesystem. And this results very weird inode numbers, e.g: item 0 key (256 INODE_ITEM 0) itemoff 16123 itemsize 160 item 6 key (88347519 INODE_ITEM 0) itemoff 15815 itemsize 160 item 16 key (88347520 INODE_ITEM 0) itemoff 15363 itemsize 160 item 20 key (88347521 INODE_ITEM 0) itemoff 15119 itemsize 160 item 24 key (88347522 INODE_ITEM 0) itemoff 14875 itemsize 160 item 26 key (88347523 INODE_ITEM 0) itemoff 14700 itemsize 160 item 28 key (88347524 INODE_ITEM 0) itemoff 14525 itemsize 160 item 30 key (88347557 INODE_ITEM 0) itemoff 14350 itemsize 160 item 32 key (88347566 INODE_ITEM 0) itemoff 14175 itemsize 160 Which is far from a regular fs created by copying the data. - Weird directory inode size calculation Unlike kernel, which updated the directory inode size every time new child inodes are added, we calculate the directory inode size by searching all its children first, then later new inodes linked to this directory won't touch the inode size. - Bad hard link detection and cross mount point handling The hard link detection is purely based on the st_ino returned from the host filesystem, this means we do not have extra checks whether the inode is even inside the same fs. And we directly reuse st_nlink from the host filesystem, if there is a hard link out of rootdir, the st_nlink will be incorrect and cause a corrupted fs. Enhance all these points by: - Use nftw() to do the preorder traversal It also provides the extra level detection, which is pretty handy. - Use a simple local inode_entry to record each parent The only value is a u64 to record the inode number. And one simple rootdir_path structure to record the list of inode_entry, alone with the current level. This rootdir_path structure along with two helpers, rootdir_path_push() and rootdir_path_pop(), along with the preorder traversal provided by nftw(), are enough for us to record all the parent directories until the rootdir. - Grab new inode number properly Just call btrfs_get_free_objectid() to grab a proper inode number, other than using some weird calculated value. - Treat every inode as a new one This means we will have no hard link support for now. But I still believe it's a good trade-off, especially considering the old handling is buggy for several corner cases. - Use btrfs_insert_inode() and btrfs_add_link() to update directory inode automatically With all the refactoring, the code is shorter and easier to read. Reviewed-by: Boris Burkov <boris@bur.io> Signed-off-by: Qu Wenruo <wqu@suse.com> |
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| ci | ||
| cmds | ||
| common | ||
| config | ||
| convert | ||
| crypto | ||
| Documentation | ||
| image | ||
| include | ||
| kernel-lib | ||
| kernel-shared | ||
| libbtrfs | ||
| libbtrfsutil | ||
| mkfs | ||
| tests | ||
| tune | ||
| .codespellrc | ||
| .editorconfig | ||
| .gitignore | ||
| .readthedocs.yaml | ||
| 64-btrfs-dm.rules | ||
| 64-btrfs-zoned.rules | ||
| autogen.sh | ||
| btrfs-completion | ||
| btrfs-corrupt-block.c | ||
| btrfs-crc.c | ||
| btrfs-debugfs | ||
| btrfs-find-root.c | ||
| btrfs-map-logical.c | ||
| btrfs-sb-mod.c | ||
| btrfs-select-super.c | ||
| btrfs.c | ||
| CHANGES | ||
| configure.ac | ||
| COPYING | ||
| fsck.btrfs | ||
| inject-error | ||
| INSTALL | ||
| Makefile | ||
| Makefile.extrawarn | ||
| Makefile.inc.in | ||
| README.md | ||
| show-blocks | ||
| VERSION | ||
Btrfs-progs
Userspace utilities to manage btrfs filesystems. License: GPLv2.
Btrfs is a copy on write (COW) filesystem for Linux aimed at implementing advanced features while focusing on fault tolerance, repair and easy administration.
This repository hosts following utilities and also documentation:
- btrfs — the main administration tool (manual page)
- mkfs.btrfs — utility to create the filesystem (manual page)
- all-in-one binary in the busybox style with mkfs.btrfs, btrfs-image and other tools built-in (standalone tools)
- libbtrfsutil (LGPL v2.1) — C and python 3 bindings, see libbtrfsutil/README.md for more
- btrfsutil python bindings published at https://pypi.org/project/btrfsutil
- manual pages and documentation source published at btrfs.readthedocs.io (RTD)
See INSTALL for build instructions, tests/README.md for testing information and ci/README.md for CI information.
Release cycle
The major version releases are time-based and follow the cycle of the linux kernel releases. The cycle usually takes 2 months. A minor version releases may happen in the meantime if there are bug fixes or minor useful improvements queued.
The release tags are signed with a GPG key ID F2B4 1200 C54E FB30 380C 1756 C565 D5F9 D76D 583B,
release tarballs are hosted at kernel.org.
See file CHANGES or changelogs on RTD.
Releases with changelog are also published at Github release page.
Static binaries
For each release there are static binaries of btrfs and btrfs.box provided.
These can be used in rescue environments and are built for x86_64
architecture (with maximum backward compatibility), inside the Github Actions
workflow.
The btrfs.box is an all-in-one tool in the busybox
style, the functionality is determined by the binary names (either symlink,
hradlink or a file copy).
Feature compatibility
The btrfs-progs of version X.Y declare support of kernel features of the same version. New progs on old kernel are expected to work, limited only by features provided by the kernel.
Build compatibility
Build is supported on the GNU C library as the primary target, and on the musl libc and uClibc-ng.
The supported compilers are gcc (minimal version 4.8) and clang (minimal version 3.4).
Build tests are done on several distributions, see Github actions workflow.
Reporting bugs
There are several ways, each has its own specifics and audience that can give feedback or work on a fix. The following list is sorted in the order of preference:
- Github issue tracker
- to the mailing list linux-btrfs@vger.kernel.org -- (not required to subscribe), beware that the mail might get overlooked in other traffic
- IRC (irc.libera.chat #btrfs) -- good for discussions eg. if a bug is already known, but reports could miss developers' attention
- please don't use https://bugzilla.kernel.org for btrfs-progs bugs
Development
The development takes place in the mailing list (linux-btrfs@vger.kernel.org) or at Github (issues, pull requests). Changes should be split to logical parts if possible, documentation may be included in the same patch as to code or separately.
The development model of btrfs-progs shares a lot with the kernel model. The
- one logical change per patch: e.g. not mixing bugfixes, cleanups, features etc., sometimes it's not clear and will be usually pointed out during reviews
- proper subject line: e.g. prefix with btrfs-progs: subpart, ... ,
descriptive yet not too long, see
git log --onelinefor some inspiration - proper changelog: the changelogs are often missing or lacking explanation why the change was made, or how is something broken, what are user-visible effects of the bug or the fix, how does an improvement help or the intended usecase
- the Signed-off-by line is not mandatory for less significant changes
(typos, documentation) but is desired as this documents who authored the
change, you can read more about the
The Developer's Certificate of Origin (chapter 11)
- if you are not used to the signed-off style, your contributions won't be rejected just because of it's missing, the Author: tag will be added as a substitute in order to allow contributions without much bothering with formalities
Pull requests
The pull requests on Github may be used for code or documentation contributions. There are basic build checks enabled in the Github actions CI for pull requests. The status can be checked at the workflow page.
- open a PR against branches devel or master
- push update to the same branch if you need to
- close the PR in case it's wrong, a mistake or needs rework
- if you're sure the changes don't need a CI build verification, please add
[skip ci]to the changelog
Source code coding style and preferences follow the
kernel coding style.
You can find the editor settings in .editorconfig and use the
EditorConfig plugin to let your editor use that,
or update your editor settings manually.
Testing
The documentation for writing and running tests can be found in tests/ and continuous integration/container images in ci/.
Development branches are tested by Github Action workflows.
Code coverage provided by codecov.io can be found here.
Documentation updates
Documentation fixes or updates do not need much explanation so sticking to the code rules in the previous section is not necessary. GitHub pull requests are OK, patches could be sent to me directly and not required to be also in the mailing list. Pointing out typos via IRC also works, although might get accidentally lost in the noise.
Documentation sources are written in RST and built by sphinx.
Third-party sources
Build dependencies are listed in INSTALL. Implementation of checksum/hash functions is provided by copies of the respective sources to avoid adding dependencies that would make deployments in rescue or limited environments harder. The implementations are portable and there are optimized versions for some architectures. Optionally it's possible to use libgcrypt, libsodium, libkcapi, Botan or OpenSSL implementations.
The builtin implementations uses the following sources: CRC32C, XXHASH, SHA256, BLAKE2.
Some other code is borrowed from kernel, eg. the raid5 tables or data structure implementation (list, rb-tree).