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io_uring: fix iopoll -EAGAIN handling 

req->iopoll() is not necessarily called by a task that submitted a
request. Because of that, it's dangerous to grab_env() and punt async on
-EGAIN, potentially grabbing another task's mm and corrupting its
memory.

Do resubmit from the submitter task context.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2020-06-28 12:52:38 +03:00 committed by Jens Axboe
parent 3adfecaa64
commit f3a6fa2267
1 changed files with 4 additions and 7 deletions
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11
fs/io_uring.c
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@ -892,6 +892,7 @@ enum io_mem_account {
ACCT_PINNED,
};
static bool io_rw_reissue(struct io_kiocb *req, long res);
static void io_cqring_fill_event(struct io_kiocb *req, long res);
static void io_put_req(struct io_kiocb *req);
static void io_double_put_req(struct io_kiocb *req);
@ -1873,14 +1874,9 @@ static void io_iopoll_queue(struct list_head *again)
req = list_first_entry(again, struct io_kiocb, list);
list_del(&req->list);
/* shouldn't happen unless io_uring is dying, cancel reqs */
if (unlikely(!current->mm)) {
/* should have ->mm unless io_uring is dying, kill reqs then */
if (unlikely(!current->mm) || !io_rw_reissue(req, -EAGAIN))
io_complete_rw_common(&req->rw.kiocb, -EAGAIN, NULL);
continue;
}
refcount_inc(&req->refs);
io_queue_async_work(req);
} while (!list_empty(again));
}
@ -2387,6 +2383,7 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe,
kiocb->ki_flags |= IOCB_HIPRI;
kiocb->ki_complete = io_complete_rw_iopoll;
req->iopoll_completed = 0;
io_get_req_task(req);
} else {
if (kiocb->ki_flags & IOCB_HIPRI)
return -EINVAL;