btrfs: report filesystem shutdown via fserror

btrfs: report filesystem shutdown via fserror

Commit 347b7042fb26 ("Merge patch series "fs: generic file IO error
reporting"") has introduced a common framework for reporting errors to
fsnotify in a standard way.

One of the functions being introduced is fserror_report_shutdown() that,
when combined with the experimental support for shutdown in btrfs, it
means that user-space can also easily detect whenever a btrfs filesystem
has been marked as shutdown.

Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>