bcachefs: Check for duplicate device ptrs in bch2_bkey_ptrs_invalid()

This is something we clearly should be checking for, but weren't -
oops.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/extents.c

@@ -1045,11 +1045,13 @@ static const char *extent_ptr_invalid(const struct bch_fs *c,
 const char *bch2_bkey_ptrs_invalid(const struct bch_fs *c, struct bkey_s_c k)
 {
 	struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(k);
+	struct bch_devs_list devs;
 	const union bch_extent_entry *entry;
 	struct bch_extent_crc_unpacked crc;
 	unsigned size_ondisk = k.k->size;
 	const char *reason;
 	unsigned nonce = UINT_MAX;
+	unsigned i;
 
 	if (k.k->type == KEY_TYPE_btree_ptr)
 		size_ondisk = c->opts.btree_node_size;
@@ -1100,6 +1102,12 @@ const char *bch2_bkey_ptrs_invalid(const struct bch_fs *c, struct bkey_s_c k)
 		}
 	}
 
+	devs = bch2_bkey_devs(k);
+	bubble_sort(devs.devs, devs.nr, u8_cmp);
+	for (i = 0; i + 1 < devs.nr; i++)
+		if (devs.devs[i] == devs.devs[i + 1])
+			return "multiple ptrs to same device";
+
 	return NULL;
 }
 

fs/bcachefs/replicas.c

@@ -11,11 +11,6 @@ static int bch2_cpu_replicas_to_sb_replicas(struct bch_fs *,
 
 /* Replicas tracking - in memory: */
 
-static inline int u8_cmp(u8 l, u8 r)
-{
-	return cmp_int(l, r);
-}
-
 static void verify_replicas_entry(struct bch_replicas_entry *e)
 {
 #ifdef CONFIG_BCACHEFS_DEBUG

fs/bcachefs/util.h

@@ -750,4 +750,9 @@ u64 *bch2_acc_percpu_u64s(u64 __percpu *, unsigned);
 
 #define cmp_int(l, r)		((l > r) - (l < r))
 
+static inline int u8_cmp(u8 l, u8 r)
+{
+	return cmp_int(l, r);
+}
+
 #endif /* _BCACHEFS_UTIL_H */