On Wed, Oct 09, 2024 at 12:57:48PM +0100, Pavel Begunkov wrote: > On 10/6/24 10:47, Ming Lei wrote: > > On Fri, Oct 04, 2024 at 04:32:04PM +0100, Pavel Begunkov wrote: > > > On 9/12/24 11:49, Ming Lei wrote: > > > ... > > ... > > > > @@ -473,6 +494,7 @@ enum { > > > > REQ_F_BUFFERS_COMMIT_BIT, > > > > REQ_F_SQE_GROUP_LEADER_BIT, > > > > REQ_F_SQE_GROUP_DEP_BIT, > > > > + REQ_F_GROUP_KBUF_BIT, > > > > /* not a real bit, just to check we're not overflowing the space */ > > > > __REQ_F_LAST_BIT, > > > > @@ -557,6 +579,8 @@ enum { > > > > REQ_F_SQE_GROUP_LEADER = IO_REQ_FLAG(REQ_F_SQE_GROUP_LEADER_BIT), > > > > /* sqe group with members depending on leader */ > > > > REQ_F_SQE_GROUP_DEP = IO_REQ_FLAG(REQ_F_SQE_GROUP_DEP_BIT), > > > > + /* group lead provides kbuf for members, set for both lead and member */ > > > > + REQ_F_GROUP_KBUF = IO_REQ_FLAG(REQ_F_GROUP_KBUF_BIT), > > > > > > We have a huge flag problem here. It's a 4th group flag, that gives > > > me an idea that it's overabused. We're adding state machines based on > > > them "set group, clear group, but if last set it again. And clear > > > group lead if refs are of particular value". And it's not really > > > clear what these two flags are here for or what they do. > > > > > > From what I see you need here just one flag to mark requests > > > that provide a buffer, ala REQ_F_PROVIDING_KBUF. On the import > > > side: > > > > > > if ((req->flags & GROUP) && (req->lead->flags & REQ_F_PROVIDING_KBUF)) > > > ... > > > > > > And when you kill the request: > > > > > > if (req->flags & REQ_F_PROVIDING_KBUF) > > > io_group_kbuf_drop(); > > > > REQ_F_PROVIDING_KBUF may be killed too, and the check helper can become: > > > > bool io_use_group_provided_buf(req) > > { > > return (req->flags & GROUP) && req->lead->grp_buf; > > } > > ->grp_kbuf is unionised, so for that to work you need to ensure that > only a buffer providing cmd / request could be a leader of a group, > which doesn't sound right. Yes, both 'req->lead->flags & REQ_F_PROVIDING_KBUF' and 'req->lead->grp_buf' may not work because the helper may be called in ->prep(), when req->lead isn't setup yet. Another idea is to reuse one of the three unused flags(LINK, HARDLINK and DRAIN) of members for marking GROUP_KBUF, then it is aligned with BUFFER_SELECT and implementation can be cleaner, what do you think of this approach? Thanks, Ming