tree 8e05279baf327e9b85e8cfd47675bada6c32ce2a
parent 464dca612bc6bceceafadfb4bf28f1a27ccc4632
author Pavel Begunkov <asml.silence@gmail.com> 1614084022 +0000
committer Jens Axboe <axboe@kernel.dk> 1618184519 -0600

io_uring: allocate memory for overflowed CQEs

Instead of using a request itself for overflowed CQE stashing, allocate a
separate entry. The disadvantage is that the allocation may fail and it
will be accounted as lost (see rings->cq_overflow), so we lose reliability
in case of memory pressure if the application is driving the CQ ring into
overflow. However, it opens a way for for multiple CQEs per an SQE and
even generating SQE-less CQEs.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
[axboe: use GFP_ATOMIC | __GFP_ACCOUNT]
Signed-off-by: Jens Axboe <axboe@kernel.dk>