io_uring: allocate memory for overflowed CQEs

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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>

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Pavel Begunkov 2021-02-23 12:40:22 +00:00 • committed by Jens Axboe

parent 464dca612b

commit 6c2450ae55

1 changed files with 46 additions and 55 deletions

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fs/io_uring.c

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