On 2022/5/10 8:45, NeilBrown wrote:
> On Mon, 09 May 2022, Miaohe Lin wrote:
>> Add helper swap_offset_available() to remove some duplicated codes.
>> Minor readability improvement.
>
> I don't think that putting the spin_lock() inside the inline helper is
> good for readability.
> If the function was called
> swap_offset_available_and_locked()
Yes, swap_offset_available_and_locked should be more suitable as we do the spin_lock
inside it. Will do this in next version.
Thanks!
>
> it might be ok. Otherwise I would rather the spin_lock() was called
> when the function returned true.
>
> Thanks,
> NeilBrown
>
>>
>> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
>> ---
>> mm/swapfile.c | 33 +++++++++++++++++----------------
>> 1 file changed, 17 insertions(+), 16 deletions(-)
>>
>> diff --git a/mm/swapfile.c b/mm/swapfile.c
>> index c90298a0561a..d5d3e2d03d28 100644
>> --- a/mm/swapfile.c
>> +++ b/mm/swapfile.c
>> @@ -776,6 +776,21 @@ static void set_cluster_next(struct swap_info_struct *si, unsigned long next)
>> this_cpu_write(*si->cluster_next_cpu, next);
>> }
>>
>> +static inline bool swap_offset_available(struct swap_info_struct *si, unsigned long offset)
>> +{
>> + if (data_race(!si->swap_map[offset])) {
>> + spin_lock(&si->lock);
>> + return true;
>> + }
>> +
>> + if (vm_swap_full() && READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) {
>> + spin_lock(&si->lock);
>> + return true;
>> + }
>> +
>> + return false;
>> +}
>> +
>> static int scan_swap_map_slots(struct swap_info_struct *si,
>> unsigned char usage, int nr,
>> swp_entry_t slots[])
>> @@ -953,15 +968,8 @@ static int scan_swap_map_slots(struct swap_info_struct *si,
>> scan:
>> spin_unlock(&si->lock);
>> while (++offset <= READ_ONCE(si->highest_bit)) {
>> - if (data_race(!si->swap_map[offset])) {
>> - spin_lock(&si->lock);
>> + if (swap_offset_available(si, offset))
>> goto checks;
>> - }
>> - if (vm_swap_full() &&
>> - READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) {
>> - spin_lock(&si->lock);
>> - goto checks;
>> - }
>> if (unlikely(--latency_ration < 0)) {
>> cond_resched();
>> latency_ration = LATENCY_LIMIT;
>> @@ -970,15 +978,8 @@ static int scan_swap_map_slots(struct swap_info_struct *si,
>> }
>> offset = si->lowest_bit;
>> while (offset < scan_base) {
>> - if (data_race(!si->swap_map[offset])) {
>> - spin_lock(&si->lock);
>> + if (swap_offset_available(si, offset))
>> goto checks;
>> - }
>> - if (vm_swap_full() &&
>> - READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) {
>> - spin_lock(&si->lock);
>> - goto checks;
>> - }
>> if (unlikely(--latency_ration < 0)) {
>> cond_resched();
>> latency_ration = LATENCY_LIMIT;
>> --
>> 2.23.0
>>
>>
> .
>
