f3e3d9cc35
[BUG]
There is a bug report about bad signal timing could lead to read-only
fs during balance:
BTRFS info (device xvdb): balance: start -d -m -s
BTRFS info (device xvdb): relocating block group 73001861120 flags metadata
BTRFS info (device xvdb): found 12236 extents, stage: move data extents
BTRFS info (device xvdb): relocating block group 71928119296 flags data
BTRFS info (device xvdb): found 3 extents, stage: move data extents
BTRFS info (device xvdb): found 3 extents, stage: update data pointers
BTRFS info (device xvdb): relocating block group 60922265600 flags metadata
BTRFS: error (device xvdb) in btrfs_drop_snapshot:5505: errno=-4 unknown
BTRFS info (device xvdb): forced readonly
BTRFS info (device xvdb): balance: ended with status: -4
[CAUSE]
The direct cause is the -EINTR from the following call chain when a
fatal signal is pending:
relocate_block_group()
|- clean_dirty_subvols()
|- btrfs_drop_snapshot()
|- btrfs_start_transaction()
|- btrfs_delayed_refs_rsv_refill()
|- btrfs_reserve_metadata_bytes()
|- __reserve_metadata_bytes()
|- wait_reserve_ticket()
|- prepare_to_wait_event();
|- ticket->error = -EINTR;
Normally this behavior is fine for most btrfs_start_transaction()
callers, as they need to catch any other error, same for the signal, and
exit ASAP.
However for balance, especially for the clean_dirty_subvols() case, we're
already doing cleanup works, getting -EINTR from btrfs_drop_snapshot()
could cause a lot of unexpected problems.
From the mentioned forced read-only report, to later balance error due
to half dropped reloc trees.
[FIX]
Fix this problem by using btrfs_join_transaction() if
btrfs_drop_snapshot() is called from relocation context.
Since btrfs_join_transaction() won't get interrupted by signal, we can
continue the cleanup.
CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>3
Signed-off-by: David Sterba <dsterba@suse.com>
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.