xfs: don't report half-built inodes to fserror

xfs: don't report half-built inodes to fserror

Sam Sun apparently found a syzbot way to fuzz a filesystem such that
xfs_iget_cache_miss would free the inode before the fserror code could
catch up.  Frustratingly he doesn't use the syzbot dashboard so there's
no C reproducer and not even a full error report, so I'm guessing that:

Inodes that are being constructed or torn down inside XFS are not
visible to the VFS.  They should never be reported to fserror.
Also, any inode that has been freshly allocated in _cache_miss should be
marked INEW immediately because, well, it's an incompletely constructed
inode that isn't yet visible to the VFS.

Reported-by: Sam Sun <samsun1006219@gmail.com>
Fixes: 5eb4cb18e445d0 ("xfs: convey metadata health events to the health monitor")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>