[PATCH AUTOSEL 5.1 006/375] io_uring: use cpu_online() to check p->sq_thread_cpu instead of cpu_possible()

Sasha Levin
2019-05-22T19:21:28Z

From: Shenghui Wang <shhuiw@foxmail.com>

[ Upstream commit 7889f44dd9cee15aff1c3f7daf81ca4dfed48fc7 ]

This issue is found by running liburing/test/io_uring_setup test.

When test run, the testcase "attempt to bind to invalid cpu" would not
pass with messages like:
io_uring_setup(1, 0xbfc2f7c8), \
flags: IORING_SETUP_SQPOLL|IORING_SETUP_SQ_AFF, \
resv: 0x00000000 0x00000000 0x00000000 0x00000000 0x00000000, \
sq_thread_cpu: 2
expected -1, got 3
FAIL

On my system, there is:
CPU(s) possible : 0-3
CPU(s) online : 0-1
CPU(s) offline : 2-3
CPU(s) present : 0-1

The sq_thread_cpu 2 is offline on my system, so the bind should fail.
But cpu_possible() will pass the check. We shouldn't be able to bind
to an offline cpu. Use cpu_online() to do the check.

After the change, the testcase run as expected: EINVAL will be returned
for cpu offlined.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Shenghui Wang <shhuiw@foxmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 84efb8956734f..30a5687a17b65 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2334,7 +2334,7 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx,
nr_cpu_ids);

ret = -EINVAL;
- if (!cpu_possible(cpu))
+ if (!cpu_online(cpu))
goto err;

ctx->sqo_thread = kthread_create_on_cpu(io_sq_thread,
--
2.20.1