660e9269d8
commit 742b06b5628f2cd23cb51a034cb54dc33c6162c5 upstream.
We hit a BUG at fs/buffer.c:3057 if we detached the nbd device
before unmounting ext4 filesystem.
The typical chain of events leading to the BUG:
jbd2_write_superblock
submit_bh
submit_bh_wbc
BUG_ON(!buffer_mapped(bh));
The block device is removed and all the pages are invalidated. JBD2
was trying to write journal superblock to the block device which is
no longer present.
Fix this by checking the journal superblock's buffer head prior to
submitting.
Reported-by: Eric Ren <renzhen@linux.alibaba.com>
Signed-off-by: Jiufei Xue <jiufei.xue@linux.alibaba.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: stable@kernel.org
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.