From: Jackie Liu <liuyun01@kylinos.cn>
Date: Mon, 9 Sep 2019 20:50:39 +0800
Subject: io_uring: fix wrong sequence setting logic
Git-commit: 8776f3fa15a5cd213c4dfab7ddaf557983374ea6
Patch-mainline: 5.4-rc1
References: bnc#1151927 5.3.4

Sqo_thread will get sqring in batches, which will cause
ctx->cached_sq_head to be added in batches. if one of these
sqes is set with the DRAIN flag, then he will never get a
chance to process, and finally sqo_thread will not exit.

Fixes: de0617e4671 ("io_uring: add support for marking commands as draining")
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 fs/io_uring.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -288,6 +288,7 @@ struct io_ring_ctx {
 struct sqe_submit {
 	const struct io_uring_sqe	*sqe;
 	unsigned short			index;
+	u32				sequence;
 	bool				has_user;
 	bool				needs_lock;
 	bool				needs_fixed_file;
@@ -2040,7 +2041,7 @@ static int io_req_set_file(struct io_rin
 
 	if (flags & IOSQE_IO_DRAIN) {
 		req->flags |= REQ_F_IO_DRAIN;
-		req->sequence = ctx->cached_sq_head - 1;
+		req->sequence = s->sequence;
 	}
 
 	if (!io_op_needs_file(s->sqe))
@@ -2247,6 +2248,7 @@ static bool io_get_sqring(struct io_ring
 	if (head < ctx->sq_entries) {
 		s->index = head;
 		s->sqe = &ctx->sq_sqes[head];
+		s->sequence = ctx->cached_sq_head;
 		ctx->cached_sq_head++;
 		return true;
 	}