52802e9a03
commit f28cef9e4daca11337cb9f144cdebedaab69d78c upstream. The attr fork can transition from shortform to leaf format while empty if the first xattr doesn't fit in shortform. While this empty leaf block state is intended to be transient, it is technically not due to the transactional implementation of the xattr set operation. We historically have a couple of bandaids to work around this problem. The first is to hold the buffer after the format conversion to prevent premature writeback of the empty leaf buffer and the second is to bypass the xattr count check in the verifier during recovery. The latter assumes that the xattr set is also in the log and will be recovered into the buffer soon after the empty leaf buffer is reconstructed. This is not guaranteed, however. If the filesystem crashes after the format conversion but before the xattr set that induced it, only the format conversion may exist in the log. When recovered, this creates a latent corrupted state on the inode as any subsequent attempts to read the buffer fail due to verifier failure. This includes further attempts to set xattrs on the inode or attempts to destroy the attr fork, which prevents the inode from ever being removed from the unlinked list. To avoid this condition, accept that an empty attr leaf block is a valid state and remove the count check from the verifier. This means that on rare occasions an attr fork might exist in an unexpected state, but is otherwise consistent and functional. Note that we retain the logic to avoid racing with metadata writeback to reduce the window where this can occur. 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> Reviewed-by: Christoph Hellwig <hch@lst.de> Acked-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Chandan Babu R <chandan.babu@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.