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SubjectRE: [PATCH 04/18] x86/resctrl: Move rmid allocation out of mkdir_rdt_prepare()
Date
Hi James,

> 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.
>
> Move the RMID allocation out of mkdir_rdt_prepare() to occur in its caller, after
> the mkdir_rdt_prepare() call. This allows the RMID allocator to know the
> CLOSID.
>
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
> arch/x86/kernel/cpu/resctrl/rdtgroup.c | 29
> +++++++++++++++++++-------
> 1 file changed, 22 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 841294ad6263..c67083a8a5f5 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -2892,6 +2892,12 @@ static int mkdir_rdt_prepare_rmid_alloc(struct
> rdtgroup *rdtgrp)
> return 0;
> }
>
> +static void mkdir_rdt_prepare_rmid_free(struct rdtgroup *rgrp) {
> + if (rdt_mon_capable)
> + free_rmid(rgrp->closid, rgrp->mon.rmid); }
> +
> static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
> const char *name, umode_t mode,
> enum rdt_group_type rtype, struct rdtgroup **r)
> @@ -2957,10 +2963,6 @@ static int mkdir_rdt_prepare(struct kernfs_node
> *parent_kn,
> goto out_destroy;
> }
>
> - ret = mkdir_rdt_prepare_rmid_alloc(rdtgrp);
> - if (ret)
> - goto out_destroy;
> -
> kernfs_activate(kn);
>
> /*
> @@ -2981,7 +2983,6 @@ static int mkdir_rdt_prepare(struct kernfs_node
> *parent_kn, static void mkdir_rdt_prepare_clean(struct rdtgroup *rgrp) {
> kernfs_remove(rgrp->kn);
> - free_rmid(rgrp->closid, rgrp->mon.rmid);
> rdtgroup_remove(rgrp);
> }
>
> @@ -3003,12 +3004,19 @@ static int rdtgroup_mkdir_mon(struct kernfs_node
> *parent_kn,
> prgrp = rdtgrp->mon.parent;
> rdtgrp->closid = prgrp->closid;
>
> + ret = mkdir_rdt_prepare_rmid_alloc(rdtgrp);
> + if (ret) {
> + mkdir_rdt_prepare_clean(rdtgrp);
> + goto out_unlock;
> + }
> +
> /*
> * Add the rdtgrp to the list of rdtgrps the parent
> * ctrl_mon group has to track.
> */
> list_add_tail(&rdtgrp->mon.crdtgrp_list, &prgrp->mon.crdtgrp_list);
>
> +out_unlock:
> rdtgroup_kn_unlock(parent_kn);

Is there any case that a lock is not unlocked here?

Best regards,
Shaopeng Tan

> return ret;
> }
> @@ -3039,10 +3047,15 @@ static int rdtgroup_mkdir_ctrl_mon(struct
> kernfs_node *parent_kn,
> ret = 0;
>
> rdtgrp->closid = closid;
> - ret = rdtgroup_init_alloc(rdtgrp);
> - if (ret < 0)
> +
> + ret = mkdir_rdt_prepare_rmid_alloc(rdtgrp);
> + if (ret)
> goto out_id_free;
>
> + ret = rdtgroup_init_alloc(rdtgrp);
> + if (ret < 0)
> + goto out_rmid_free;
> +
> list_add(&rdtgrp->rdtgroup_list, &rdt_all_groups);
>
> if (rdt_mon_capable) {
> @@ -3061,6 +3074,8 @@ static int rdtgroup_mkdir_ctrl_mon(struct
> kernfs_node *parent_kn,
>
> out_del_list:
> list_del(&rdtgrp->rdtgroup_list);
> +out_rmid_free:
> + mkdir_rdt_prepare_rmid_free(rdtgrp);
> out_id_free:
> closid_free(closid);
> out_common_fail:
> --
> 2.30.2

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