After commit c60aa176c6de8 ("swapfile: swap allocation cycle if
nonrot"), swap allocation is cyclic. Current approach is done with two
separate loop on the upper and lower half. This looks a little
redundant.
>From another point of view, the loop iterates [lowest_bit, highest_bit]
range starting with (offset + 1) but except scan_base. So we can
simplify the loop with condition (next_offset() != scan_base) by
introducing next_offset() which makes sure offset fit in that range
with correct order.
Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
CC: Hugh Dickins <hughd@xxxxxxxxxx>
---
mm/swapfile.c | 26 +++++++++-----------------
1 file changed, 9 insertions(+), 17 deletions(-)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 95024f9b691a..42c5c2010bfc 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -729,6 +729,14 @@ static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
}
}
+static unsigned long next_offset(struct swap_info_struct *si,
+ unsigned long *offset)
+{
+ if (++(*offset) > si->highest_bit)
+ *offset = si->lowest_bit;
+ return *offset;
+}
+
static int scan_swap_map_slots(struct swap_info_struct *si,
unsigned char usage, int nr,
swp_entry_t slots[])
@@ -883,7 +891,7 @@ static int scan_swap_map_slots(struct swap_info_struct *si,
scan:
spin_unlock(&si->lock);
- while (++offset <= si->highest_bit) {
+ while (next_offset(si, &offset) != scan_base) {
if (!si->swap_map[offset]) {
spin_lock(&si->lock);
goto checks;
@@ -897,22 +905,6 @@ static int scan_swap_map_slots(struct swap_info_struct *si,
latency_ration = LATENCY_LIMIT;
}
}
- offset = si->lowest_bit;
- while (offset < scan_base) {
- if (!si->swap_map[offset]) {
- spin_lock(&si->lock);
- goto checks;
- }
- if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
- spin_lock(&si->lock);
- goto checks;
- }
- if (unlikely(--latency_ration < 0)) {
- cond_resched();
- latency_ration = LATENCY_LIMIT;
- }
- offset++;
- }
spin_lock(&si->lock);
no_page:
--
2.23.0
