linux-kernel - Re: [PATCH 3/3] 9p: Add mempools for RPCs

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Message-ID: <1877940.0u7pHPiiHj@silver>
Date:   Mon, 04 Jul 2022 15:39:32 +0200
From:   Christian Schoenebeck <linux_oss@...debyte.com>
To:     Kent Overstreet <kent.overstreet@...il.com>,
        Dominique Martinet <asmadeus@...ewreck.org>
Cc:     linux-kernel@...r.kernel.org, v9fs-developer@...ts.sourceforge.net,
        Eric Van Hensbergen <ericvh@...il.com>,
        Latchesar Ionkov <lucho@...kov.net>
Subject: Re: [PATCH 3/3] 9p: Add mempools for RPCs

On Montag, 4. Juli 2022 15:06:31 CEST Kent Overstreet wrote:
> On Mon, Jul 04, 2022 at 01:12:51PM +0200, Christian Schoenebeck wrote:
> > On Montag, 4. Juli 2022 05:38:46 CEST Dominique Martinet wrote:
> > > +Christian, sorry I just noticed you weren't in Ccs again --
> > > the patches are currently there if you want a look:
> > > https://evilpiepirate.org/git/bcachefs.git/log/?h=9p_mempool
> > 
> > I wonder whether it would make sense to update 9p section in MAINTAINERS
> > to
> > better reflect current reality, at least in a way such that contributors
> > would CC me right away?
> > 
> > Eric, Latchesar, what do you think?
> > 
> > > > @@ -270,10 +276,8 @@ p9_tag_alloc(struct p9_client *c, int8_t type,
> > > > unsigned int max_size)>
> > > > 
> > > >  	if (!req)
> > > >  	
> > > >  		return ERR_PTR(-ENOMEM);
> > > > 
> > > > -	if (p9_fcall_init(c, &req->tc, alloc_msize))
> > > > -		goto free_req;
> > > > -	if (p9_fcall_init(c, &req->rc, alloc_msize))
> > > > -		goto free;
> > > > +	p9_fcall_init(c, &req->tc, 0, alloc_msize);
> > > > +	p9_fcall_init(c, &req->rc, 1, alloc_msize);
> > > 
> > > mempool allocation never fails, correct?
> > > 
> > > (don't think this needs a comment, just making sure here)
> > > 
> > > This all looks good to me, will queue it up in my -next branch after
> > > running some tests next weekend and hopefully submit when 5.20 opens
> > > with the code making smaller allocs more common.
> > 
> > Hoo, Dominique, please hold your horses. I currently can't keep up with
> > reviewing and testing all pending 9p patches right now.
> > 
> > Personally I would hold these patches back for now. They would make sense
> > on current situation on master, because ATM basically all 9p requests
> > simply allocate exactly 'msize' for any 9p request.
> 
> Err, why?
> 
> These patches are pretty simple, and they fix a bug that's affecting users
> right now (and has been for ages)

So simple that it already had one obvious bug (at least). But as it seems that 
Dominique already supports your patch, I refrain from enumerating more 
reasons.

> > However that's exactly what I was going to address with my already posted
> > patches (relevant patches regarding this issue here being 9..12):
> > https://lore.kernel.org/all/cover.1640870037.git.linux_oss@crudebyte.com/
> > And in the cover letter (section "STILL TODO" ... "3.") I was suggesting
> > to
> > subsequently subdivide kmem_cache_alloc() into e.g. 4 allocation size
> > categories? Because that's what my already posted patches do anyway.
> 
> Yeah that sounds like you're just reimplementing kmalloc.

Quite exaggerated statement.

Best regards,
Christian Schoenebeck