gfs2: add a helper function to get_log_header that can be used elsewhere

Move and re-order the error checks and hash/crc computations into another
function __get_log_header() so it can be used in scenarios where buffer_heads
are not being used for the log header.

Signed-off-by: Abhi Das <adas@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
diff --git a/fs/gfs2/recovery.h b/fs/gfs2/recovery.h
index 11fdfab..11d8124 100644
--- a/fs/gfs2/recovery.h
+++ b/fs/gfs2/recovery.h
@@ -31,6 +31,9 @@ extern int gfs2_find_jhead(struct gfs2_jdesc *jd,
 		    struct gfs2_log_header_host *head);
 extern int gfs2_recover_journal(struct gfs2_jdesc *gfs2_jd, bool wait);
 extern void gfs2_recover_func(struct work_struct *work);
+extern int __get_log_header(struct gfs2_sbd *sdp,
+			    const struct gfs2_log_header *lh, unsigned int blkno,
+			    struct gfs2_log_header_host *head);
 
 #endif /* __RECOVERY_DOT_H__ */