From: Pavel Begunkov <asml.silence@gmail.com>
Date: Sat, 18 Jul 2020 08:31:20 +0000 (+0300)
Subject: io_uring: don't miscount pinned memory
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=5dbcad51f78434e782d0470b8b5fc4380700c35f;p=linux.git

io_uring: don't miscount pinned memory

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>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 6e5ea7991c081..ba7ce103667b5 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7670,12 +7670,12 @@ 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);