ce5684c62e
When searching the extent tree for the target extent item, we can miss it
if the extent item is the first item in a leaf and if there is a previous
leaf in the extent tree.
For example, if we call btrfs-map-logical like this:
$ btrfs-map-logical -l 5382144 /dev/sdc
And we have the following extent tree layout:
leaf 5386240 items 26 free space 2505 generation 7 owner EXTENT_TREE
leaf 5386240 flags 0x1(WRITTEN) backref revision 1
(...)
item 25 key (5373952 METADATA_ITEM 0) itemoff 3155 itemsize 33
refs 1 gen 7 flags TREE_BLOCK
tree block skinny level 0
(176 0x5) tree block backref root FS_TREE
leaf 5480448 items 56 free space 276 generation 7 owner EXTENT_TREE
leaf 5480448 flags 0x1(WRITTEN) backref revision 1
(...)
item 0 key (5382144 METADATA_ITEM 0) itemoff 3962 itemsize 33
refs 1 gen 7 flags TREE_BLOCK
tree block skinny level 0
(176 0x7) tree block backref root CSUM_TREE
(...)
Then the following happens:
1) We enter map_one_extent() with search_forward == 0 and
*logical_ret == 5382144;
2) We search for the key (5382144 0 0) which leaves us with a path
pointing to leaf 5386240 at slot 26 - one slot beyond the last item;
3) We then call:
btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0])
Which is not valid since there's no item at that slot, but since the
area of the leaf where an item at that slot should be is zeroed out,
we end up getting a key of (0 0 0);
4) We then enter the "if" statement bellow, since key.type is 0, and call
btrfs_previous_extent_item(), which leaves at slot 25 of leaf 5386240,
point to the extent item of the extent 5373952.
The requested extent, 5382144, is the first item of the next leaf
(5480448), but we totally miss it;
5) We return to the caller, the main() function, with 'cur_logical'
pointing to the metadata extent at 5373952, and not to the requested
one at 5382144.
In the last while loop of main() we have 'cur_logical' == 5373952,
which makes the loop have no iterations and therefore the local
variable 'found' remains with a value of 0, and then the program fails
like this:
$ btrfs-map-logical -l 5382144 /dev/sdc
ERROR: no extent found at range [5382144,5386240)
Fix this by never accessing beyond the last slot of a leaf. If we ever end
up at a slot beyond the last item in a leaf, just call btrfs_next_leaf()
and process the first item in the returned path.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
||
|---|---|---|
| .github/workflows | ||
| Documentation | ||
| check | ||
| ci | ||
| cmds | ||
| common | ||
| config | ||
| convert | ||
| crypto | ||
| image | ||
| include | ||
| kernel-lib | ||
| kernel-shared | ||
| libbtrfs | ||
| libbtrfsutil | ||
| mkfs | ||
| tests | ||
| tune | ||
| .codespellrc | ||
| .editorconfig | ||
| .gitignore | ||
| .readthedocs.yaml | ||
| 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 | ||
| 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
- 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).