swap_readpage(): avoid blk_wake_io_task() if !synchronous

swap_readpage() sets waiter = bio->bi_private even if synchronous = F,
this means that the caller can get the spurious wakeup after return.

This can be fatal if blk_wake_io_task() does
set_current_state(TASK_RUNNING) after the caller does
set_special_state(), in the worst case the kernel can crash in
do_task_dead().

Link: http://lkml.kernel.org/r/[email protected]
Fixes: 0619317ff8baa2d ("block: add polled wakeup task helper")
Signed-off-by: Oleg Nesterov <[email protected]>
Reported-by: Qian Cai <[email protected]>
Acked-by: Hugh Dickins <[email protected]>
Reviewed-by: Jens Axboe <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions