Re: [PATCH v2] bcachefs: Prefer struct_size over open coded arithmetic

[Kent Overstreet]

On Sun, Mar 10, 2024 at 12:02:26PM +0100, Erick Archer wrote:
> 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 [1]
> Link: https://github.com/KSPP/linux/issues/160 [2]
> Signed-off-by: Erick Archer <erick.archer@xxxxxxx>

applied