[BUG]
Commit 723427d7e6 ("btrfs-progs: check: change the way lowmem mode
traverses metadata") introduces a regression which could make some fsck
self test case to fail.
For fsck test case 004-no-dir-item, btrfs check --mode=lowmem --repair
can cause BUG_ON() with ret = -17 (-EEXIST) when committing transaction.
The problem happens with the following backtrace:
./btrfs(+0x22045)[0x555d0dade045]
./btrfs(+0x2216f)[0x555d0dade16f]
./btrfs(+0x29df1)[0x555d0dae5df1]
./btrfs(+0x2a142)[0x555d0dae6142]
./btrfs(btrfs_alloc_free_block+0x78)[0x555d0dae6202]
./btrfs(__btrfs_cow_block+0x177)[0x555d0dad00a2]
./btrfs(btrfs_cow_block+0x116)[0x555d0dad05a8]
./btrfs(commit_tree_roots+0x91)[0x555d0db1fd4f]
./btrfs(btrfs_commit_transaction+0x18c)[0x555d0db20100]
./btrfs(btrfs_fix_super_size+0x190)[0x555d0db005a4]
./btrfs(btrfs_fix_device_and_super_size+0x177)[0x555d0db00771]
./btrfs(cmd_check+0x1757)[0x555d0db4f6ab]
./btrfs(main+0x138)[0x555d0dace5dd]
/usr/lib/libc.so.6(__libc_start_main+0xea)[0x7fa5e4613f6a]
./btrfs(_start+0x2a)[0x555d0dacddda]
The bug is triggered by that, extent allocator considers range
[29360128, 29376512) as free and allocates it. However when inserting
EXTENT_ITEM, btrfs finds there is already one tree block (fs tree root),
returning -EEXIST and causing the later BUG_ON().
[CAUSE]
The cause is in repair mode, lowmem check always pins all metadata
blocks. However pinned metadata blocks will be unpined when transaction
commits, and will be marked as *FREE* space.
So later extent allocator will consider such range free and allocates
them incorrectly.
[FIX]
Don't pin metadata blocks without valid reason or preparation (like
discard all free space cache to re-calculate free space on next write).
Fixes: 723427d7e6 ("btrfs-progs: check: change the way lowmem mode traverses metadata")
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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:
btrfs — the main administration tool (manual page)
mkfs.btrfs — utility to create the filesystem (manual page)
See INSTALL for build instructions and tests/README.md for
testing 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 wiki.
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:
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.freenode.net #btrfs) -- good for discussions eg. if a bug is already
known, but reports could miss developers' attention
bugzilla.kernel.org -- (requires
registration), set the product to Filesystems and component Btrfs, please put
'btrfs-progs' into the subject so it's clear that it's not a kernel bug
report
Development
The patch submissions, development or general discussions take place at
linux-btrfs@vger.kernel.org mailinglist, subsciption is not required to post.
The GitHub pull requests will not be accepted directly, the preferred way is to
send patches to the mailinglist instead. You can link to a branch in any git
repository if the mails do not make it to the mailinglist or just for
convenience (makes it easier to test).
The development model of btrfs-progs shares a lot with the kernel model. The
github way is different in some ways. We, the upstream community, expect that
the patches meet some criteria (often lacking in github contributions):
one logical change per patch: eg. not mixing bugfixes, cleanups, features
etc., sometimes it's not clear and will be usually pointed out during reviews
proper subject line: eg. prefix with btrfs-progs: subpart, ... ,
descriptive yet not too long, see git log --oneline for 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
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
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
mailinglist. Pointing out typos via IRC also works, although might get
accidentally lost in the noise.
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