Allow MADV_COLLAPSE behavior for process_madvise(2) if caller has
CAP_SYS_ADMIN or is requesting collapse of it's own memory.
This is useful for the development of userspace agents that seek to
optimize THP utilization system-wide by using userspace signals to
prioritize what memory is most deserving of being THP-backed.
Signed-off-by: Zach O'Keefe <zokeefe@xxxxxxxxxx>
---
mm/madvise.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/mm/madvise.c b/mm/madvise.c
index eccac2620226..b19e2f4b924c 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1171,13 +1171,15 @@ madvise_behavior_valid(int behavior)
}
static bool
-process_madvise_behavior_valid(int behavior)
+process_madvise_behavior_valid(int behavior, struct task_struct *task)
{
switch (behavior) {
case MADV_COLD:
case MADV_PAGEOUT:
case MADV_WILLNEED:
return true;
+ case MADV_COLLAPSE:
+ return task == current || capable(CAP_SYS_ADMIN);
default:
return false;
}
@@ -1455,7 +1457,7 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
goto free_iov;
}
- if (!process_madvise_behavior_valid(behavior)) {
+ if (!process_madvise_behavior_valid(behavior, task)) {
ret = -EINVAL;
goto release_task;
}
--
2.36.1.255.ge46751e96f-goog
