afb585a97f
This implements journal callbacks j_submit|finish_inode_data_buffers()
with different behavior for data=journal: to write-protect pages under
commit, preventing changes to buffers writeably mapped to userspace.
If a buffer's content changes between commit's checksum calculation
and write-out to disk, it can cause journal recovery/mount failures
upon a kernel crash or power loss.
[ 27.334874] EXT4-fs: Warning: mounting with data=journal disables delayed allocation, dioread_nolock, and O_DIRECT support!
[ 27.339492] JBD2: Invalid checksum recovering data block 8705 in log
[ 27.342716] JBD2: recovery failed
[ 27.343316] EXT4-fs (loop0): error loading journal
mount: /ext4: can't read superblock on /dev/loop0.
In j_submit_inode_data_buffers() we write-protect the inode's pages
with write_cache_pages() and redirty w/ writepage callback if needed.
In j_finish_inode_data_buffers() there is nothing do to.
And in order to use the callbacks, inodes are added to the inode list
in transaction in __ext4_journalled_writepage() and ext4_page_mkwrite().
In ext4_page_mkwrite() we must make sure that the buffers are attached
to the transaction as jbddirty with write_end_fn(), as already done in
__ext4_journalled_writepage().
Signed-off-by: Mauricio Faria de Oliveira <mfo@canonical.com>
Reported-by: Dann Frazier <dann.frazier@canonical.com>
Reported-by: kernel test robot <lkp@intel.com> # wbc.nr_to_write
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20201006004841.600488-5-mfo@canonical.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.