linux-kernel - [PATCH 5.2 186/313] io_uring: fix wrong sequence setting logic

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Date:   Thu,  3 Oct 2019 17:52:44 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jackie Liu <liuyun01@...inos.cn>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.2 186/313] io_uring: fix wrong sequence setting logic

From: Jackie Liu <liuyun01@...inos.cn>

[ Upstream commit 8776f3fa15a5cd213c4dfab7ddaf557983374ea6 ]

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@...inos.cn>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/io_uring.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 03cd8f5bba850..701936f2bde39 100644
--- 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;
@@ -1894,7 +1895,7 @@ static int io_req_set_file(struct io_ring_ctx *ctx, const struct sqe_submit *s,
 
 	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))
@@ -2050,6 +2051,7 @@ static bool io_get_sqring(struct io_ring_ctx *ctx, struct sqe_submit *s)
 	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;
 	}
-- 
2.20.1