e79f18a4a7
Unlike kernel, in btrfs-progs btrfs_start_transaction() never checks if there is enough metadata space. This can lead to very dangerous situation where there is no metadata space left at all, deadlocking future tree operations. This patch introduces a very basic version of metadata/system free space check by: - Check if there is enough metadata/system space left If there is enough, go as usual. - If there is not enough space left, try allocating a new chunk - Recheck if the new space can meet our demand If not, return ERR_PTR(-ENOSPC). Otherwise, allocate a new trans handle to the caller. This is possible thanks to the simplified transaction model in btrfs-progs: - We don't allow joining a transaction This means we don't need to handle complex cases like data ordered extents, which need to reserve space first, then join the current transaction and use the reserved blocks. - We don't allow multiple transaction handles for one transaction Since btrfs-progs is single threaded, we always start a transaction and then commit it. However there is a feature that must be an exception for the new metadata/system free space check: - btrfs check --init-extent-tree As all the meta/system free space check is based on the space info, which is loaded from block group items. Thus when rebuilding extent tree, we can no longer have an accurate view, thus we have to disable the feature for the whole execution if we're rebuilding the extent tree. For now, there is no regression exposed during the self tests, but I really hope this can be an extra safety net to prevent causing ENOSPC deadlock in btrfs-progs. Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com> |
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|---|---|---|
| .github/workflows | ||
| Documentation | ||
| check | ||
| ci | ||
| cmds | ||
| common | ||
| config | ||
| convert | ||
| crypto | ||
| image | ||
| include | ||
| kernel-lib | ||
| kernel-shared | ||
| libbtrfs | ||
| libbtrfsutil | ||
| mkfs | ||
| tests | ||
| tune | ||
| .editorconfig | ||
| .gitignore | ||
| 64-btrfs-dm.rules | ||
| 64-btrfs-zoned.rules | ||
| CHANGES | ||
| COPYING | ||
| INSTALL | ||
| Makefile | ||
| Makefile.extrawarn | ||
| Makefile.inc.in | ||
| README.md | ||
| VERSION | ||
| 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 | ||
| configure.ac | ||
| fsck.btrfs | ||
| inject-error | ||
| quick-test.c | ||
| show-blocks | ||
README.md
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
- 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.
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 (first time contributors' pull requests may need an approval). 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 testing documentation can be found in tests/ and continuous integration/container images in ci/.
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 or libkcapi implementations.
- CRC32C: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/
- XXHASH: https://github.com/Cyan4973/xxHash
- SHA256: https://tools.ietf.org/html/rfc4634
- BLAKE2: https://github.com/BLAKE2/BLAKE2
Some other code is borrowed from kernel, eg. the raid5 tables or data structure implementation (list, rb-tree).