linux-kernel - Re: [PATCH 6/6] Drop flex

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Message-ID: <20181213180917.GB4127@hmswarspite.think-freely.org>
Date:   Thu, 13 Dec 2018 13:09:17 -0500
From:   Neil Horman <nhorman@...driver.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Xin Long <lucien.xin@...il.com>, kent.overstreet@...il.com,
        LKML <linux-kernel@...r.kernel.org>, dave.hansen@...el.com,
        davem <davem@...emloft.net>, Oleg Babin <obabin@...tuozzo.com>,
        Konstantin Khorenko <khorenko@...tuozzo.com>
Subject: Re: [PATCH 6/6] Drop flex_arrays

On Thu, Dec 13, 2018 at 08:45:33AM -0800, Matthew Wilcox wrote:
> On Thu, Dec 13, 2018 at 10:51:49AM -0500, Neil Horman wrote:
> > On Thu, Dec 13, 2018 at 06:41:11AM -0800, Matthew Wilcox wrote:
> > > On Thu, Dec 13, 2018 at 09:30:47PM +0900, Xin Long wrote:
> > > > On Sat, Sep 8, 2018 at 1:57 AM Kent Overstreet
> > > > <kent.overstreet@...il.com> wrote:
> > > > >
> > > > > All existing users have been converted to generic radix trees
> > > > NAK, SCTP is still using flex_arrays,
> > > > # grep flex_array net/sctp/*
> > > > 
> > > > This patch will break the build.
> > > 
> > > sctp added that user after this patch was sent.  Please stop adding
> > > flexarray users!
> > > 
> > > This particular user should probably have just used kvmalloc.
> > > 
> > 
> > No, I don't think thats right.
> > 
> > This appears to have been sent on September 7th.  Commit
> > 0d493b4d0be352b5e361e4fa0bc3efe952d8b10e, which added the use of flex_arrays to
> > sctp, seems to have been merged on August 10th, a month prior.
> 
> Are you seriously suggesting anybody sending cleanups needs to be
> monitoring every single email list to see if anybody has added a new user?
> Removing the flexarray has been advertised since May.
> https://lkml.org/lkml/2018/5/22/1142
> 
I don't see how thats any more egregious than everyone else having to monitor
for removals of code thats in the tree at some indeterminate future.  The long and the short of it
is that a new flex_array user was added in the intervening 7 months that this
patch has been waiting to go in, and it will now break if merged.  I'm sorry we
started using it during that time, but it got missed by everyone in the chain
that merged it, and hasn't been noticed in the 4 months since.  It is what it
is, and now it needs to be undone. 

> > regardless, however, sctp has a current in-tree use of flex_arrays, and merging
> > this patch will break the build without a respin.
> 
> Great.  I await your patch to replace the flexarray usage.
Sure, we'll get to it as soon as we can, or, if you are in a hurry, you can
replace the same usage, like you've done for all the other users in this series.

Neil