From bb38d4571964ccc223892e9600e7d9a5cbf43414 Mon Sep 17 00:00:00 2001 From: Reinette Chatre Date: Tue, 30 Jun 2026 21:27:09 -0700 Subject: [PATCH] fs/resctrl: Communicate resource group deleted error via last_cmd_status User space expects last_cmd_status to contain additional information if any resctrl command fails. A resctrl command may be blocked on the rdtgroup_mutex waiting for another command to finish and find that once the mutex is available that the resource group has since been deleted. In this scenario the command will fail while last_cmd_status contains either "ok" if the last_cmd_status buffer is empty or an outdated error from a previous command failure if last_cmd_status buffer has content. Include clearing of last_cmd_status buffer as part of rdtgroup_kn_lock_live() that is used to obtain access and needed locking to a resource group before attempting a command on the group. With the last_cmd_status buffer ready, provide an appropriate message to user space if the resource group has been deleted. No last_cmd_status treatment is needed for the remaining failure of rdtgroup_kn_lock_live() encountering a non-existent resource group since that could only occur during an attempt to obtain a resource group lock on a file in info/ which is an invalid usage. Signed-off-by: Reinette Chatre Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Tony Luck Tested-by: Babu Moger Link: https://patch.msgid.link/9982141ec6f3ec18e0c53d7feabb19651583cf0e.1782857711.git.reinette.chatre@intel.com --- fs/resctrl/ctrlmondata.c | 3 --- fs/resctrl/monitor.c | 2 -- fs/resctrl/rdtgroup.c | 20 +++++++++++--------- 3 files changed, 11 insertions(+), 14 deletions(-) diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c index 8d5a8b1e659a..18ec9f564b5a 100644 --- a/fs/resctrl/ctrlmondata.c +++ b/fs/resctrl/ctrlmondata.c @@ -317,7 +317,6 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of, rdtgroup_kn_unlock(of->kn); return -ENOENT; } - rdt_last_cmd_clear(); /* Valid input requires a trailing newline */ if (nbytes == 0 || buf[nbytes - 1] != '\n') { @@ -434,7 +433,6 @@ int rdtgroup_schemata_show(struct kernfs_open_file *of, } } else if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED) { if (!rdtgrp->plr->d) { - rdt_last_cmd_clear(); rdt_last_cmd_puts("Cache domain offline\n"); ret = -ENODEV; } else { @@ -475,7 +473,6 @@ ssize_t rdtgroup_mba_mbps_event_write(struct kernfs_open_file *of, rdtgroup_kn_unlock(of->kn); return -ENOENT; } - rdt_last_cmd_clear(); /* Valid input requires a trailing newline */ if (nbytes == 0 || buf[nbytes - 1] != '\n') { diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c index b50da2b02594..73413cb128ea 100644 --- a/fs/resctrl/monitor.c +++ b/fs/resctrl/monitor.c @@ -1696,7 +1696,6 @@ int mbm_L3_assignments_show(struct kernfs_open_file *of, struct seq_file *s, voi goto out_unlock; } - rdt_last_cmd_clear(); if (!resctrl_arch_mbm_cntr_assign_enabled(r)) { rdt_last_cmd_puts("mbm_event counter assignment mode is not enabled\n"); ret = -EINVAL; @@ -1836,7 +1835,6 @@ ssize_t mbm_L3_assignments_write(struct kernfs_open_file *of, char *buf, rdtgroup_kn_unlock(of->kn); return -ENOENT; } - rdt_last_cmd_clear(); /* Valid input requires a trailing newline */ if (nbytes == 0 || buf[nbytes - 1] != '\n') { diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c index 72347d11f0da..08d58c4e9acb 100644 --- a/fs/resctrl/rdtgroup.c +++ b/fs/resctrl/rdtgroup.c @@ -359,7 +359,6 @@ static int rdtgroup_cpus_show(struct kernfs_open_file *of, if (rdtgrp) { if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED) { if (!rdtgrp->plr->d) { - rdt_last_cmd_clear(); rdt_last_cmd_puts("Cache domain offline\n"); ret = -ENODEV; } else { @@ -522,8 +521,6 @@ static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of, goto out_unlock; } - rdt_last_cmd_clear(); - if (!buf) { rdt_last_cmd_printf("%s: Invalid input\n", is_cpu_list(of) ? "cpus_list" : "cpus"); @@ -788,7 +785,6 @@ static ssize_t rdtgroup_tasks_write(struct kernfs_open_file *of, rdtgroup_kn_unlock(of->kn); return -ENOENT; } - rdt_last_cmd_clear(); if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED || rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) { @@ -1529,7 +1525,6 @@ static ssize_t rdtgroup_mode_write(struct kernfs_open_file *of, return -ENOENT; } - rdt_last_cmd_clear(); /* Valid input requires a trailing newline */ if (nbytes == 0 || buf[nbytes - 1] != '\n') { rdt_last_cmd_puts("mode: Invalid input\n"); @@ -1666,7 +1661,6 @@ static int rdtgroup_size_show(struct kernfs_open_file *of, if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED) { if (!rdtgrp->plr->d) { - rdt_last_cmd_clear(); rdt_last_cmd_puts("Cache domain offline\n"); ret = -ENODEV; } else { @@ -2726,10 +2720,20 @@ struct rdtgroup *rdtgroup_kn_lock_live(struct kernfs_node *kn) cpus_read_lock(); mutex_lock(&rdtgroup_mutex); + rdt_last_cmd_clear(); /* Was this group deleted while we waited? */ - if (rdtgrp->flags & RDT_DELETED) + if (rdtgrp->flags & RDT_DELETED) { + /* + * It is safe to dereference kn to obtain the resource group's + * name because one extra reference to kn is obtained + * during resource group creation that will be released by + * rdtgroup_remove() called by rdtgroup_kn_put(). + */ + rdt_last_cmd_printf("Resource group %s deleted. No commands possible.\n", + rdt_kn_name(rdtgrp->kn)); return NULL; + } return rdtgrp; } @@ -3943,8 +3947,6 @@ static int mkdir_rdt_prepare(struct kernfs_node *parent_kn, goto out_unlock; } - rdt_last_cmd_clear(); - /* * Check that the parent directory for a monitor group is a "mon_groups" * directory.