bcachefs: Switch reconstruct_alloc to a mount option

Right now this is the only way of repairing bucket gens in the future
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bcachefs.h

@@ -285,9 +285,7 @@ do {									\
 		"Force reads to use the reconstruct path, when reading"	\
 		"from erasure coded extents")				\
 	BCH_DEBUG_PARAM(test_restart_gc,				\
-		"Test restarting mark and sweep gc when bucket gens change")\
-	BCH_DEBUG_PARAM(test_reconstruct_alloc,				\
-		"Test reconstructing the alloc btree")
+		"Test restarting mark and sweep gc when bucket gens change")
 
 #define BCH_DEBUG_PARAMS_ALL() BCH_DEBUG_PARAMS_ALWAYS() BCH_DEBUG_PARAMS_DEBUG()
 

fs/bcachefs/opts.h

@@ -258,6 +258,11 @@ enum opt_type {
 	  OPT_BOOL(),							\
 	  NO_SB_OPT,			false,				\
 	  NULL,		"Don\'t start filesystem, only open devices")	\
+	x(reconstruct_alloc,		u8,				\
+	  OPT_MOUNT,							\
+	  OPT_BOOL(),							\
+	  NO_SB_OPT,			false,				\
+	  NULL,		"Reconstruct alloc btree")			\
 	x(version_upgrade,		u8,				\
 	  OPT_MOUNT,							\
 	  OPT_BOOL(),							\

fs/bcachefs/recovery.c

@@ -659,7 +659,7 @@ static int read_btree_roots(struct bch_fs *c)
 			continue;
 
 		if (i == BTREE_ID_ALLOC &&
-		    test_reconstruct_alloc(c)) {
+		    c->opts.reconstruct_alloc) {
 			c->sb.compat &= ~(1ULL << BCH_COMPAT_FEAT_ALLOC_INFO);
 			continue;
 		}