xfs: Validate log space at mount time

index 304b3d0..2a631d9 100644
@@ -30,6 +30,7 @@
 #include "xfs_alloc_btree.h"
 #include "xfs_ialloc_btree.h"
 #include "xfs_log_recover.h"
+#include "xfs_log_rlimit.h"
 #include "xfs_trans_priv.h"
 #include "xfs_dinode.h"
 #include "xfs_inode.h"

@@ -631,6 +632,17 @@ xfs_log_mount(
 	}
 
 	/*
+	 * Validate the given log space and drop a critical message via syslog
+	 * if the log size is too small that would lead to some unexpected
+	 * situations in transaction log space reservation stage.
+	 * Note: we can't just reject the mount if the validation fails.  This
+	 * would mean that people would have to downgrade their kernel just to
+	 * remedy the situation as there is no way to grow the log (short of
+	 * black magic surgery with xfs_db).
+	 */
+	xfs_log_validate_logspace(mp);
+
+	/*
 	 * Initialize the AIL now we have a log.
 	 */
 	error = xfs_trans_ail_init(mp);