545aa41f5c
XFS shutdown deadlocks have been reproduced by fstest generic/475. The deadlock signature involves log I/O completion running error handling to abort logged items and waiting for an inode cluster buffer lock in the buffer item unpin handler. The buffer lock is held by xfsaild attempting to flush an inode. The buffer happens to be pinned and so xfs_iflush() triggers an async log force to begin work required to get it unpinned. The log force is blocked waiting on the commit completion, which never occurs and thus leaves the filesystem deadlocked. The root problem is that aborted log I/O completion pots commit completion behind callback completion, which is unexpected for async log forces. Under normal running conditions, an async log force returns to the caller once the CIL ctx has been formatted/submitted and the commit completion event triggered at the tail end of xlog_cil_push(). If the filesystem has shutdown, however, we rely on xlog_cil_committed() to trigger the completion event and it happens to do so after running log item unpin callbacks. This makes it unsafe to invoke an async log force from contexts that hold locks that might also be required in log completion processing. To address this problem, wake commit completion waiters before aborting log items in the log I/O completion handler. This ensures that an async log force will not deadlock on held locks if the filesystem happens to shutdown. Note that it is still unsafe to issue a sync log force while holding such locks because a sync log force explicitly waits on the force completion, which occurs after log I/O completion processing. Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> |
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| 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.