[PATCH 1/2] io_uring: don't miscount pinned memory

Pavel Begunkov
2020-07-18T08:33:20Z

io_sqe_buffer_unregister() uses cxt->sqo_mm for memory accounting, but
io_ring_ctx_free() drops ->sqo_mm before leaving pinned_vm
over-accounted. Postpone mm cleanup for when it's not needed anymore.

Fixes: 309758254ea62 ("io_uring: report pinned memory usage")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
fs/io_uring.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 644e5727389c..e535152fefab 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7655,12 +7655,12 @@ static void io_destroy_buffers(struct io_ring_ctx *ctx)
static void io_ring_ctx_free(struct io_ring_ctx *ctx)
{
io_finish_async(ctx);
+ io_sqe_buffer_unregister(ctx);
if (ctx->sqo_mm) {
mmdrop(ctx->sqo_mm);
ctx->sqo_mm = NULL;
}

- io_sqe_buffer_unregister(ctx);
io_sqe_files_unregister(ctx);
io_eventfd_unregister(ctx);
io_destroy_buffers(ctx);
--
2.24.0