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Subject[PATCH 1/3] vmevent: Implement equal-to attribute state
This complements GT and LT, making it possible to combine GE and LE
operators. We'll use it for blended attributes: the special attributes
will return either 0 or <threshold>, so to make two-way notifications
we will pass LT | EQ bits.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
---
include/linux/vmevent.h | 6 +++++-
mm/vmevent.c | 22 +++++++++++++++-------
2 files changed, 20 insertions(+), 8 deletions(-)
diff --git a/include/linux/vmevent.h b/include/linux/vmevent.h
index ca97cf0..aae0d24 100644
--- a/include/linux/vmevent.h
+++ b/include/linux/vmevent.h
@@ -27,9 +27,13 @@ enum {
*/
VMEVENT_ATTR_STATE_VALUE_GT = (1UL << 1),
/*
+ * Sample value is equal to user-specified value
+ */
+ VMEVENT_ATTR_STATE_VALUE_EQ = (1UL << 2),
+ /*
* One-shot mode.
*/
- VMEVENT_ATTR_STATE_ONE_SHOT = (1UL << 2),
+ VMEVENT_ATTR_STATE_ONE_SHOT = (1UL << 3),

/* Saved state, used internally by the kernel for one-shot mode. */
__VMEVENT_ATTR_STATE_VALUE_WAS_LT = (1UL << 30),
diff --git a/mm/vmevent.c b/mm/vmevent.c
index 47ed448..9f1520b 100644
--- a/mm/vmevent.c
+++ b/mm/vmevent.c
@@ -87,28 +87,39 @@ static bool vmevent_match(struct vmevent_watch *watch)
u32 state = attr->state;
bool attr_lt = state & VMEVENT_ATTR_STATE_VALUE_LT;
bool attr_gt = state & VMEVENT_ATTR_STATE_VALUE_GT;
+ bool attr_eq = state & VMEVENT_ATTR_STATE_VALUE_EQ;

if (!state)
continue;

- if (attr_lt || attr_gt) {
+ if (attr_lt || attr_gt || attr_eq) {
bool one_shot = state & VMEVENT_ATTR_STATE_ONE_SHOT;
u32 was_lt_mask = __VMEVENT_ATTR_STATE_VALUE_WAS_LT;
u32 was_gt_mask = __VMEVENT_ATTR_STATE_VALUE_WAS_GT;
u64 value = vmevent_sample_attr(watch, attr);
bool lt = value < attr->value;
bool gt = value > attr->value;
+ bool eq = value == attr->value;
bool was_lt = state & was_lt_mask;
bool was_gt = state & was_gt_mask;
+ bool was_eq = was_lt && was_gt;
bool ret = false;

- if (((attr_lt && lt) || (attr_gt && gt)) && !one_shot)
+ if (((attr_lt && lt) || (attr_gt && gt) ||
+ (attr_eq && eq)) && !one_shot)
return true;

- if (attr_lt && lt && was_lt) {
+ if (attr_eq && eq && was_eq) {
return false;
- } else if (attr_gt && gt && was_gt) {
+ } else if (attr_lt && lt && was_lt && !was_eq) {
return false;
+ } else if (attr_gt && gt && was_gt && !was_eq) {
+ return false;
+ } else if (eq) {
+ state |= was_lt_mask;
+ state |= was_gt_mask;
+ if (attr_eq)
+ ret = true;
} else if (lt) {
state |= was_lt_mask;
state &= ~was_gt_mask;
@@ -119,9 +130,6 @@ static bool vmevent_match(struct vmevent_watch *watch)
state &= ~was_lt_mask;
if (attr_gt)
ret = true;
- } else {
- state &= ~was_lt_mask;
- state &= ~was_gt_mask;
}

attr->state = state;
--
1.7.9.2


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