bcachefs: Add an option to control sharding new inode numbers

We're seeing a bug where inode creates end up spinning in
bch2_inode_create - disabling sharding will simplify what we're testing.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/bcachefs_format.h

@@ -1348,6 +1348,7 @@ LE64_BITMASK(BCH_SB_GC_RESERVE_BYTES,	struct bch_sb, flags[2],  4, 64);
 
 LE64_BITMASK(BCH_SB_ERASURE_CODE,	struct bch_sb, flags[3],  0, 16);
 LE64_BITMASK(BCH_SB_METADATA_TARGET,	struct bch_sb, flags[3], 16, 28);
+LE64_BITMASK(BCH_SB_SHARD_INUMS,	struct bch_sb, flags[3], 28, 29);
 
 /*
  * Features:

fs/bcachefs/inode.c

@@ -479,16 +479,23 @@ struct btree_iter *bch2_inode_create(struct btree_trans *trans,
 	struct bkey_s_c k;
 	u64 min, max, start, pos, *hint;
 	int ret = 0;
+	unsigned bits = (c->opts.inodes_32bit ? 31 : 63);
 
-	u64 cpu = raw_smp_processor_id();
-	unsigned bits = (c->opts.inodes_32bit
-		? 31 : 63) - c->inode_shard_bits;
+	if (c->opts.shard_inode_numbers) {
+		u64 cpu = raw_smp_processor_id();
 
-	min = (cpu << bits);
-	max = (cpu << bits) | ~(ULLONG_MAX << bits);
+		bits -= c->inode_shard_bits;
 
-	min = max_t(u64, min, BLOCKDEV_INODE_MAX);
-	hint = c->unused_inode_hints + cpu;
+		min = (cpu << bits);
+		max = (cpu << bits) | ~(ULLONG_MAX << bits);
+
+		min = max_t(u64, min, BLOCKDEV_INODE_MAX);
+		hint = c->unused_inode_hints + cpu;
+	} else {
+		min = BLOCKDEV_INODE_MAX;
+		max = ~(ULLONG_MAX << bits);
+		hint = c->unused_inode_hints;
+	}
 
 	start = READ_ONCE(*hint);
 

fs/bcachefs/opts.h

@@ -165,8 +165,13 @@ enum opt_type {
 	x(inodes_32bit,			u8,				\
 	  OPT_FORMAT|OPT_MOUNT|OPT_RUNTIME,				\
 	  OPT_BOOL(),							\
-	  BCH_SB_INODE_32BIT,		false,				\
+	  BCH_SB_INODE_32BIT,		true,				\
 	  NULL,		"Constrain inode numbers to 32 bits")		\
+	x(shard_inode_numbers,		u8,				\
+	  OPT_FORMAT|OPT_MOUNT|OPT_RUNTIME,				\
+	  OPT_BOOL(),							\
+	  BCH_SB_SHARD_INUMS,		false,				\
+	  NULL,		"Shard new inode numbers by CPU id")		\
 	x(gc_reserve_percent,		u8,				\
 	  OPT_FORMAT|OPT_MOUNT|OPT_RUNTIME,				\
 	  OPT_UINT(5, 21),						\