On 5/27/21 10:43 PM, Noah Goldstein wrote:
> On Mon, May 24, 2021 at 7:51 PM Pavel Begunkov <asml.silence@xxxxxxxxx> wrote:
>> -static void io_free_file_tables(struct io_file_table *table, unsigned nr_files)
>> +static void io_free_page_table(void **table, size_t size)
>> {
>> - unsigned i, nr_tables = DIV_ROUND_UP(nr_files, IORING_MAX_FILES_TABLE);
>> + unsigned i, nr_tables = DIV_ROUND_UP(size, PAGE_SIZE);
>>
>> for (i = 0; i < nr_tables; i++)
>> - kfree(table->files[i]);
>> - kfree(table->files);
>> - table->files = NULL;
>> + kfree(table[i]);
>> + kfree(table);
>> +}
>> +
>> +static void **io_alloc_page_table(size_t size)
>> +{
>> + unsigned i, nr_tables = DIV_ROUND_UP(size, PAGE_SIZE);
>> + size_t init_size = size;
>> + void **table;
>> +
>> + table = kcalloc(nr_tables, sizeof(*table), GFP_KERNEL);
>> + if (!table)
>> + return NULL;
>> +
>> + for (i = 0; i < nr_tables; i++) {
>> + unsigned int this_size = min(size, PAGE_SIZE);
>> +
>> + table[i] = kzalloc(this_size, GFP_KERNEL);
>> + if (!table[i]) {
>> + io_free_page_table(table, init_size);
>> + return NULL;
> Unless zalloc returns non-NULL for size == 0, you are guranteed to do
> this for size <= PAGE_SIZE * (nr_tables - 1). Possibly worth calculating early?
Far from being a fast path, so would rather keep it simpler
and cleaner
>
> If you calculate early you could then make the loop:
>
> for (i = 0; i < nr_tables - 1; i++) {
> table[i] = kzalloc(PAGE_SIZE, GFP_KERNEL);
> if (!table[i]) {
> io_free_page_table(table, init_size);
> return NULL;
> }
> }
>
> table[i] = kzalloc(size - (nr_tables - 1) * PAGE_SIZE, GFP_KERNEL);
> if (!table[i]) {
> io_free_page_table(table, init_size);
> return NULL;
> }
>
> Which is almost certainly faster.
--
Pavel Begunkov
