[RFC 1/1] io_uring: use valid mm in io_req_work_grab_env() in SQPOLL mode

[Bijan Mottahedeh <bijan.mottahedeh@xxxxxxxxxx>]

If current->mm is not set in SQPOLL mode, then use ctx->sqo_mm;
otherwise fail thre request.

Signed-off-by: Bijan Mottahedeh <bijan.mottahedeh@xxxxxxxxxx>
---
 fs/io_uring.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index cb696ab..fd53ea6 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1062,8 +1062,18 @@ static inline void io_req_work_grab_env(struct io_kiocb *req,
 					const struct io_op_def *def)
 {
 	if (!req->work.mm && def->needs_mm) {
-		mmgrab(current->mm);
-		req->work.mm = current->mm;
+		struct mm_struct *mm = current->mm;
+
+		if (!mm) {
+			if (req->ctx && req->ctx->sqo_thread)
+				mm = req->ctx->sqo_mm;
+			else
+				req->work.flags |= IO_WQ_WORK_CANCEL;
+		}
+		if (mm) {
+			mmgrab(mm);
+			req->work.mm = mm;
+		}
 	}
 	if (!req->work.creds)
 		req->work.creds = get_current_cred();
-- 
1.8.3.1