On 10/27/22 5:27 PM, Jens Axboe wrote: > On 10/27/22 4:14 PM, Pavel Begunkov wrote: >> There are ways to deprive bioset mempool of requests using pcpu caches >> and never return them back, which breaks forward progress guarantees bioset >> tried to provide. Fix it. >> >> Pavel Begunkov (2): >> mempool: introduce mempool_is_saturated >> bio: don't rob bios from starving bioset >> >> block/bio.c | 2 ++ >> include/linux/mempool.h | 5 +++++ >> 2 files changed, 7 insertions(+) >> > > This isn't really a concern for 6.1 and earlier, because the caching is > just for polled IO. Polled IO will not be grabbing any of the reserved > inflight units on the mempool side, which is what guarantees the forward > progress. > > It'll be a concern for the 6.2 irq based general caching, so it would > need to be handled there. So perhaps this can be a pre-series for a > reposting of that patchset. Just a followup, since we had some out-of-band discussion. This is a potential concern on the bio side, though not on the request side. But this approach is racy, we'll figure something else out. -- Jens Axboe
