bcachefs: Prefer struct_size over open coded arithmetic
This is an effort to get rid of all multiplications from allocation
functions in order to prevent integer overflows [1][2].
As the "op" variable is a pointer to "struct promote_op" and this
structure ends in a flexible array:
struct promote_op {
[...]
struct bio_vec bi_inline_vecs[];
};
and the "t" variable is a pointer to "struct journal_seq_blacklist_table"
and this structure also ends in a flexible array:
struct journal_seq_blacklist_table {
[...]
struct journal_seq_blacklist_table_entry {
u64 start;
u64 end;
bool dirty;
} entries[];
};
the preferred way in the kernel is to use the struct_size() helper to
do the arithmetic instead of the argument "size + size * count" in the
kzalloc() functions.
This way, the code is more readable and safer.
Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
Link: https://github.com/KSPP/linux/issues/160
Signed-off-by: Erick Archer <erick.archer@gmx.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>