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Subject[PATCH v3 03/12] perf, mmap: Factor out perf_alloc/free_rb()
Date
From: Robert Richter <robert.richter@linaro.org>

Factor out code to allocate and deallocate ringbuffers. We need this
later to setup the sampling buffer for persistent events.

While at this, replacing get_current_user() with get_uid(user).

Signed-off-by: Robert Richter <robert.richter@linaro.org>
Signed-off-by: Robert Richter <rric@kernel.org>
---
kernel/events/core.c | 75 +++++++++++++++++++++++++++++-------------------
kernel/events/internal.h | 3 ++
2 files changed, 48 insertions(+), 30 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index c9a5d4c..24810d5 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3124,8 +3124,44 @@ static void free_event_rcu(struct rcu_head *head)
}

static void ring_buffer_put(struct ring_buffer *rb);
+static void ring_buffer_attach(struct perf_event *event, struct ring_buffer *rb);
static void ring_buffer_detach(struct perf_event *event, struct ring_buffer *rb);

+/*
+ * Must be called with &event->mmap_mutex held. event->rb must be
+ * NULL. perf_alloc_rb() requires &event->mmap_count to be incremented
+ * on success which corresponds to &rb->mmap_count that is initialized
+ * with 1.
+ */
+int perf_alloc_rb(struct perf_event *event, int nr_pages, int flags)
+{
+ struct ring_buffer *rb;
+
+ rb = rb_alloc(nr_pages,
+ event->attr.watermark ? event->attr.wakeup_watermark : 0,
+ event->cpu, flags);
+ if (!rb)
+ return -ENOMEM;
+
+ atomic_set(&rb->mmap_count, 1);
+ ring_buffer_attach(event, rb);
+ rcu_assign_pointer(event->rb, rb);
+
+ perf_event_update_userpage(event);
+
+ return 0;
+}
+
+/* Must be called with &event->mmap_mutex held. event->rb must be set. */
+void perf_free_rb(struct perf_event *event)
+{
+ struct ring_buffer *rb = event->rb;
+
+ rcu_assign_pointer(event->rb, NULL);
+ ring_buffer_detach(event, rb);
+ ring_buffer_put(rb);
+}
+
static void unaccount_event_cpu(struct perf_event *event, int cpu)
{
if (event->parent)
@@ -3177,6 +3213,7 @@ static void __free_event(struct perf_event *event)

call_rcu(&event->rcu_head, free_event_rcu);
}
+
static void free_event(struct perf_event *event)
{
irq_work_sync(&event->pending);
@@ -3184,8 +3221,6 @@ static void free_event(struct perf_event *event)
unaccount_event(event);

if (event->rb) {
- struct ring_buffer *rb;
-
/*
* Can happen when we close an event with re-directed output.
*
@@ -3193,12 +3228,8 @@ static void free_event(struct perf_event *event)
* over us; possibly making our ring_buffer_put() the last.
*/
mutex_lock(&event->mmap_mutex);
- rb = event->rb;
- if (rb) {
- rcu_assign_pointer(event->rb, NULL);
- ring_buffer_detach(event, rb);
- ring_buffer_put(rb); /* could be last */
- }
+ if (event->rb)
+ perf_free_rb(event);
mutex_unlock(&event->mmap_mutex);
}

@@ -3798,11 +3829,8 @@ static void ring_buffer_detach_all(struct ring_buffer *rb)
* still restart the iteration to make sure we're not now
* iterating the wrong list.
*/
- if (event->rb == rb) {
- rcu_assign_pointer(event->rb, NULL);
- ring_buffer_detach(event, rb);
- ring_buffer_put(rb); /* can't be last, we still have one */
- }
+ if (event->rb == rb)
+ perf_free_rb(event);
mutex_unlock(&event->mmap_mutex);
put_event(event);

@@ -3938,7 +3966,6 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
unsigned long user_locked, user_lock_limit;
struct user_struct *user = current_user();
unsigned long locked, lock_limit;
- struct ring_buffer *rb;
unsigned long vma_size;
unsigned long nr_pages;
long user_extra, extra;
@@ -4022,27 +4049,15 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
if (vma->vm_flags & VM_WRITE)
flags |= RING_BUFFER_WRITABLE;

- rb = rb_alloc(nr_pages,
- event->attr.watermark ? event->attr.wakeup_watermark : 0,
- event->cpu, flags);
-
- if (!rb) {
- ret = -ENOMEM;
+ ret = perf_alloc_rb(event, nr_pages, flags);
+ if (ret)
goto unlock;
- }

- atomic_set(&rb->mmap_count, 1);
- rb->mmap_locked = extra;
- rb->mmap_user = get_current_user();
+ event->rb->mmap_locked = extra;
+ event->rb->mmap_user = get_uid(user);

atomic_long_add(user_extra, &user->locked_vm);
vma->vm_mm->pinned_vm += extra;
-
- ring_buffer_attach(event, rb);
- rcu_assign_pointer(event->rb, rb);
-
- perf_event_update_userpage(event);
-
unlock:
if (!ret)
atomic_inc(&event->mmap_count);
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index 96a07d2..8ddaf57 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -190,4 +190,7 @@ static inline void put_event(struct perf_event *event)
__put_event(event);
}

+extern int perf_alloc_rb(struct perf_event *event, int nr_pages, int flags);
+extern void perf_free_rb(struct perf_event *event);
+
#endif /* _KERNEL_EVENTS_INTERNAL_H */
--
1.8.3.2


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