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[ Upstream commit 8c81dd46ef3c416b3b95e3020fb90dbd44e6140b ] Forcing the log to disk after reading the agf is wrong, we might be calling xfs_log_force with XFS_LOG_SYNC with a metadata lock held. This can cause a deadlock when racing a fstrim with a filesystem shutdown. The deadlock has been identified due a miscalculation bug in device-mapper dm-thin, which returns lack of space to its users earlier than the device itself really runs out of space, changing the device-mapper volume into an error state. The problem happened while filling the filesystem with a single file, triggering the bug in device-mapper, consequently causing an IO error and shutting down the filesystem. If such file is removed, and fstrim executed before the XFS finishes the shut down process, the fstrim process will end up holding the buffer lock, and going to sleep on the cil wait queue. At this point, the shut down process will try to wake up all the threads waiting on the cil wait queue, but for this, it will try to hold the same buffer log already held my the fstrim, locking up the filesystem. Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.