linux-kernel - RE: [PATCH 03/18] x86/resctrl: Create helper for RMID allocation and mondata dir creation

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Date:   Fri, 6 Jan 2023 03:23:27 +0000
From:   "Yu, Fenghua" <fenghua.yu@...el.com>
To:     James Morse <james.morse@....com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "Chatre, Reinette" <reinette.chatre@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Babu Moger <Babu.Moger@....com>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        "carl@...amperecomputing.com" <carl@...amperecomputing.com>,
        "lcherian@...vell.com" <lcherian@...vell.com>,
        "bobo.shaobowang@...wei.com" <bobo.shaobowang@...wei.com>,
        "tan.shaopeng@...itsu.com" <tan.shaopeng@...itsu.com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        Xin Hao <xhao@...ux.alibaba.com>,
        "xingxin.hx@...nanolis.org" <xingxin.hx@...nanolis.org>,
        "baolin.wang@...ux.alibaba.com" <baolin.wang@...ux.alibaba.com>,
        "peternewman@...gle.com" <peternewman@...gle.com>
Subject: RE: [PATCH 03/18] x86/resctrl: Create helper for RMID allocation and
 mondata dir creation

Hi, James,

> James Morse <james.morse@....com> writes:
> 
> RMID are allocated for each monitor or control group directory, because each
> of these needs its own RMID. For control groups,
> rdtgroup_mkdir_ctrl_mon() later goes on to allocate the CLOSID.
> 
> MPAM's equivalent of RMID are not an independent number, so can't be
> allocated until the CLOSID is known. An RMID allocation for one CLOSID may fail,
> whereas another may succeed depending on how many monitor groups a
> control group has.
> 
> The RMID allocation needs to move to be after the CLOSID has been allocated.
> 
> To make a subsequent change that does this easier to read, move the RMID
> allocation and mondata dir creation to a helper.
> 
> Signed-off-by: James Morse <james.morse@....com>
> ---
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 42 +++++++++++++++++---------
>  1 file changed, 27 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 9ce4746778f4..841294ad6263 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -2868,6 +2868,30 @@ static int rdtgroup_init_alloc(struct rdtgroup *rdtgrp)
>  	return 0;
>  }
> 
> +static int mkdir_rdt_prepare_rmid_alloc(struct rdtgroup *rdtgrp) {
> +	int ret;
> +
> +	if (!rdt_mon_capable)
> +		return 0;
> +
> +	ret = alloc_rmid();
> +	if (ret < 0) {
> +		rdt_last_cmd_puts("Out of RMIDs\n");
> +		return ret;
> +	}
> +	rdtgrp->mon.rmid = ret;
> +
> +	ret = mkdir_mondata_all(rdtgrp->kn, rdtgrp, &rdtgrp-
> >mon.mon_data_kn);
> +	if (ret) {
> +		rdt_last_cmd_puts("kernfs subdir error\n");
> +		free_rmid(rdtgrp->closid, rdtgrp->mon.rmid);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
>  static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
>  			     const char *name, umode_t mode,
>  			     enum rdt_group_type rtype, struct rdtgroup **r)
> @@ -2933,20 +2957,10 @@ static int mkdir_rdt_prepare(struct kernfs_node
> *parent_kn,
>  		goto out_destroy;
>  	}
> 
> -	if (rdt_mon_capable) {
> -		ret = alloc_rmid();
> -		if (ret < 0) {
> -			rdt_last_cmd_puts("Out of RMIDs\n");
> -			goto out_destroy;
> -		}
> -		rdtgrp->mon.rmid = ret;
> +	ret = mkdir_rdt_prepare_rmid_alloc(rdtgrp);
> +	if (ret)
> +		goto out_destroy;
> 
> -		ret = mkdir_mondata_all(kn, rdtgrp, &rdtgrp-
> >mon.mon_data_kn);
> -		if (ret) {
> -			rdt_last_cmd_puts("kernfs subdir error\n");
> -			goto out_idfree;
> -		}
> -	}
>  	kernfs_activate(kn);
> 
>  	/*
> @@ -2954,8 +2968,6 @@ static int mkdir_rdt_prepare(struct kernfs_node
> *parent_kn,
>  	 */
>  	return 0;
> 
> -out_idfree:
> -	free_rmid(rdtgrp->closid, rdtgrp->mon.rmid);
>  out_destroy:
>  	kernfs_put(rdtgrp->kn);
>  	kernfs_remove(rdtgrp->kn);

Why not free allocated rmid? Rmid leak without freed.

Thanks.

-Fenghua