linux-kernel - [PATCH] io_uring: fix the bug of child process can't do io task

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Message-Id: <20200915130245.89585-1-zhuyinyin@bytedance.com>
Date:   Tue, 15 Sep 2020 21:02:45 +0800
From:   Yinyin Zhu <zhuyinyin@...edance.com>
To:     viro@...iv.linux.org.uk, axboe@...nel.dk
Cc:     linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, zhuyinyin@...edance.com
Subject: [PATCH] io_uring: fix the bug of child process can't do io task

when parent process setup a io_uring_instance, the ctx->sqo_mm was
assigned of parent process'mm. Then it fork a child
process. So the child process inherits the io_uring_instance fd from
parent process. Then the child process submit a io task to the io_uring
instance. The kworker will do the io task actually, and use
the ctx->sqo_mm as its mm, but this ctx->sqo_mm is parent process's mm,
not the child process's mm. so child do the io task unsuccessfully. To
fix this bug, when a process submit a io task to the kworker, assign the
ctx->sqo_mm with this process's mm.

Signed-off-by: Yinyin Zhu <zhuyinyin@...edance.com>
---
 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 f115fff39cf4..f5d6bd54a625 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -514,7 +514,7 @@ static inline void io_queue_async_work(struct io_ring_ctx *ctx,
 	}

 	req->files = current->files;
-
+	ctx->sqo_mm = current->mm;
 	spin_lock_irqsave(&ctx->task_lock, flags);
 	list_add(&req->task_list, &ctx->task_list);
 	req->work_task = NULL;
-- 
2.11.0