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When executing generic/388 on a ppc64le machine, we notice the following call trace, VFS: brelse: Trying to free free buffer WARNING: CPU: 0 PID: 6637 at /root/repos/linux/fs/buffer.c:1195 __brelse+0x84/0xc0 Call Trace: __brelse+0x80/0xc0 (unreliable) invalidate_bh_lru+0x78/0xc0 on_each_cpu_mask+0xa8/0x130 on_each_cpu_cond_mask+0x130/0x170 invalidate_bh_lrus+0x44/0x60 invalidate_bdev+0x38/0x70 ext4_put_super+0x294/0x560 generic_shutdown_super+0xb0/0x170 kill_block_super+0x38/0xb0 deactivate_locked_super+0xa4/0xf0 cleanup_mnt+0x164/0x1d0 task_work_run+0x110/0x160 do_notify_resume+0x414/0x460 ret_from_except_lite+0x70/0x74 The warning happens because flush_descriptor() drops bh reference it does not own. The bh reference acquired by jbd2_journal_get_descriptor_buffer() is owned by the log_bufs list and gets released when this list is processed. The reference for doing IO is only acquired in write_dirty_buffer() later in flush_descriptor(). Reported-by: Harish Sriram <harish@linux.ibm.com> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Chandan Rajendra <chandan@linux.ibm.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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.