[PATCH 2/2] io_uring: return locked and pinned page accounting

Pavel Begunkov
2020-07-18T08:33:23Z

Locked and pinned memory accounting in io_{,un}account_mem() depends on
having ->sqo_mm, which is NULL after a recent change for non SQPOLL'ed
io_ring. That disables the accounting.

Return ->sqo_mm initialisation back, and do __io_sq_thread_acquire_mm()
based on IORING_SETUP_SQPOLL flag.

Fixes: 8eb06d7e8dd85 ("io_uring: fix missing ->mm on exit")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
fs/io_uring.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index e535152fefab..57e1f26b6a6b 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -980,7 +980,8 @@ static void io_sq_thread_drop_mm(void)
static int __io_sq_thread_acquire_mm(struct io_ring_ctx *ctx)
{
if (!current->mm) {
- if (unlikely(!ctx->sqo_mm || !mmget_not_zero(ctx->sqo_mm)))
+ if (unlikely(!(ctx->flags & IORING_SETUP_SQPOLL) ||
+ !mmget_not_zero(ctx->sqo_mm)))
return -EFAULT;
kthread_use_mm(ctx->sqo_mm);
}
@@ -7244,10 +7245,10 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx,
{
int ret;

- if (ctx->flags & IORING_SETUP_SQPOLL) {
- mmgrab(current->mm);
- ctx->sqo_mm = current->mm;
+ mmgrab(current->mm);
+ ctx->sqo_mm = current->mm;

+ if (ctx->flags & IORING_SETUP_SQPOLL) {
ret = -EPERM;
if (!capable(CAP_SYS_ADMIN))
goto err;
--
2.24.0