mirror of
https://github.com/torvalds/linux.git
synced 2024-11-23 04:31:50 +00:00
A mirror of the official Linux kernel repository just in case
303591a0a9
The log quiesce mechanism historically terminates by marking the log clean with an unmount record. The primary objective is to indicate that log recovery is no longer required after the quiesce has flushed all in-core changes and written back filesystem metadata. While this is perfectly fine, it is somewhat hacky as currently used in certain contexts. For example, filesystem freeze quiesces (i.e. cleans) the log and immediately redirties it with a dummy superblock transaction to ensure that log recovery runs in the event of a crash. While this functions correctly, cleaning the log from freeze context is clearly superfluous given the current redirtying behavior. Instead, the desired behavior can be achieved by simply covering the log. This effectively retires all on-disk log items from the active range of the log by issuing two synchronous and sequential dummy superblock update transactions that serve to update the on-disk log head and tail. The subtle difference is that the log technically remains dirty due to the lack of an unmount record, though recovery is effectively a no-op due to the content of the checkpoints being clean (i.e. the unmodified on-disk superblock). Log covering currently runs in the background and only triggers once the filesystem and log has idled. The purpose of the background mechanism is to prevent log recovery from replaying the most recently logged items long after those items may have been written back. In the quiesce path, the log has been deliberately idled by forcing the log and pushing the AIL until empty in a context where no further mutable filesystem operations are allowed. Therefore, we can cover the log as the final step in the log quiesce codepath to reflect that all previously active items have been successfully written back. This facilitates selective log covering from certain contexts (i.e. freeze) that only seek to quiesce, but not necessarily clean the log. Note that as a side effect of this change, log covering now occurs when cleaning the log as well. This is harmless, facilitates subsequent cleanups, and is mostly temporary as various operations switch to use explicit log covering. Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Allison Henderson <allison.henderson@oracle.com> |
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| 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 | ||
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.