kernel: don't call do_exit() for PF_IO_WORKER threads

stable inclusion
from stable-v5.10.162
commit 831cb78a2a5e86fe705ef4e3095c7cbc587c6a57
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6LQMS

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=831cb78a2a5e86fe705ef4e3095c7cbc587c6a57



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[ Upstream commit 10442994 ]

Right now we're never calling get_signal() from PF_IO_WORKER threads, but
in preparation for doing so, don't handle a fatal signal for them. The
workers have state they need to cleanup when exiting, so just return
instead of calling do_exit() on their behalf. The threads themselves will
detect a fatal signal and do proper shutdown.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>