bcachefs: Fix integer overflow in bch2_disk_reservation_get()

The sectors argument shouldn't have been a u32 - it can be up to U32_MAX
(i.e. fallocate creating persistent reservations), and if replication is
enabled we'll overflow when we calculate the real number of sectors to
reserve. Oops.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/buckets.c

@@ -2109,7 +2109,7 @@ int bch2_trans_mark_update(struct btree_trans *trans,
 #define SECTORS_CACHE	1024
 
 int bch2_disk_reservation_add(struct bch_fs *c, struct disk_reservation *res,
-			      unsigned sectors, int flags)
+			      u64 sectors, int flags)
 {
 	struct bch_fs_pcpu *pcpu;
 	u64 old, v, get;

fs/bcachefs/buckets.h

@@ -283,7 +283,7 @@ static inline void bch2_disk_reservation_put(struct bch_fs *c,
 
 int bch2_disk_reservation_add(struct bch_fs *,
 			      struct disk_reservation *,
-			     unsigned, int);
+			      u64, int);
 
 static inline struct disk_reservation
 bch2_disk_reservation_init(struct bch_fs *c, unsigned nr_replicas)
@@ -300,8 +300,7 @@ bch2_disk_reservation_init(struct bch_fs *c, unsigned nr_replicas)
 
 static inline int bch2_disk_reservation_get(struct bch_fs *c,
 					    struct disk_reservation *res,
-					    unsigned sectors,
-					    unsigned nr_replicas,
+					    u64 sectors, unsigned nr_replicas,
 					    int flags)
 {
 	*res = bch2_disk_reservation_init(c, nr_replicas);