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Message-Id: <20251126020825.1511671-1-chenridong@huaweicloud.com>
Date: Wed, 26 Nov 2025 02:08:25 +0000
From: Chen Ridong <chenridong@...weicloud.com>
To: tj@...nel.org,
hannes@...xchg.org,
mkoutny@...e.com
Cc: cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org,
lujialin4@...wei.com,
chenridong@...wei.com
Subject: [PATCH -next] cgroup: Use descriptor table to unify mount flag management
From: Chen Ridong <chenridong@...wei.com>
The cgroup2 mount flags (e.g. nsdelegate, favordynmods) were previously
handled via scattered switch-case and conditional checks across
parameter parsing, flag application, and option display paths. This
leads to redundant code and increased maintenance cost when adding/removing
flags.
Introduce a `cgroup_mount_flag_desc` descriptor table to centralize the
mapping between flag bits, names, and apply functions. Refactor the
relevant paths to use this table for unified management:
1. cgroup2_parse_param: Replace switch-case with table lookup
2. apply_cgroup_root_flags: Replace multiple conditionals with table
iteration
3. cgroup_show_options: Replace hardcoded seq_puts with table-driven output
No functional change intended, and the mount option output format remains
compatible with the original implementation.
Signed-off-by: Chen Ridong <chenridong@...wei.com>
---
kernel/cgroup/cgroup.c | 107 +++++++++++++++++++----------------------
1 file changed, 49 insertions(+), 58 deletions(-)
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index e717208cfb18..1e4033d05c29 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -2005,6 +2005,36 @@ static const struct fs_parameter_spec cgroup2_fs_parameters[] = {
{}
};
+struct cgroup_mount_flag_desc {
+ u64 flag;
+ const char *name;
+ void (*apply)(struct cgroup_root *root, u64 bit, bool enable);
+};
+
+static void apply_cgroup_favor_flags(struct cgroup_root *root,
+ u64 bit, bool enable)
+{
+ return cgroup_favor_dynmods(root, enable);
+}
+
+static void __apply_cgroup_root_flags(struct cgroup_root *root,
+ u64 bit, bool enable)
+{
+ if (enable)
+ root->flags |= bit;
+ else
+ root->flags &= ~bit;
+}
+
+static const struct cgroup_mount_flag_desc mount_flags_desc[nr__cgroup2_params] = {
+{CGRP_ROOT_NS_DELEGATE, "nsdelegate", __apply_cgroup_root_flags},
+{CGRP_ROOT_FAVOR_DYNMODS, "favordynmods", apply_cgroup_favor_flags},
+{CGRP_ROOT_MEMORY_LOCAL_EVENTS, "memory_localevents", __apply_cgroup_root_flags},
+{CGRP_ROOT_MEMORY_RECURSIVE_PROT, "memory_recursiveprot", __apply_cgroup_root_flags},
+{CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING, "memory_hugetlb_accounting", __apply_cgroup_root_flags},
+{CGRP_ROOT_PIDS_LOCAL_EVENTS, "pids_localevents", __apply_cgroup_root_flags}
+};
+
static int cgroup2_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
@@ -2014,28 +2044,11 @@ static int cgroup2_parse_param(struct fs_context *fc, struct fs_parameter *param
opt = fs_parse(fc, cgroup2_fs_parameters, param, &result);
if (opt < 0)
return opt;
+ if (opt >= nr__cgroup2_params)
+ return -EINVAL;
- switch (opt) {
- case Opt_nsdelegate:
- ctx->flags |= CGRP_ROOT_NS_DELEGATE;
- return 0;
- case Opt_favordynmods:
- ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;
- return 0;
- case Opt_memory_localevents:
- ctx->flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS;
- return 0;
- case Opt_memory_recursiveprot:
- ctx->flags |= CGRP_ROOT_MEMORY_RECURSIVE_PROT;
- return 0;
- case Opt_memory_hugetlb_accounting:
- ctx->flags |= CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;
- return 0;
- case Opt_pids_localevents:
- ctx->flags |= CGRP_ROOT_PIDS_LOCAL_EVENTS;
- return 0;
- }
- return -EINVAL;
+ ctx->flags |= mount_flags_desc[opt].flag;
+ return 0;
}
struct cgroup_of_peak *of_peak(struct kernfs_open_file *of)
@@ -2047,51 +2060,29 @@ struct cgroup_of_peak *of_peak(struct kernfs_open_file *of)
static void apply_cgroup_root_flags(unsigned int root_flags)
{
- if (current->nsproxy->cgroup_ns == &init_cgroup_ns) {
- if (root_flags & CGRP_ROOT_NS_DELEGATE)
- cgrp_dfl_root.flags |= CGRP_ROOT_NS_DELEGATE;
- else
- cgrp_dfl_root.flags &= ~CGRP_ROOT_NS_DELEGATE;
-
- cgroup_favor_dynmods(&cgrp_dfl_root,
- root_flags & CGRP_ROOT_FAVOR_DYNMODS);
-
- if (root_flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS)
- cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS;
- else
- cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_LOCAL_EVENTS;
+ int i;
- if (root_flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT)
- cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_RECURSIVE_PROT;
- else
- cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_RECURSIVE_PROT;
+ if (current->nsproxy->cgroup_ns != &init_cgroup_ns)
+ return;
- if (root_flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING)
- cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;
- else
- cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;
+ for (i = 0; i < nr__cgroup2_params; ++i) {
+ bool enable;
- if (root_flags & CGRP_ROOT_PIDS_LOCAL_EVENTS)
- cgrp_dfl_root.flags |= CGRP_ROOT_PIDS_LOCAL_EVENTS;
- else
- cgrp_dfl_root.flags &= ~CGRP_ROOT_PIDS_LOCAL_EVENTS;
+ enable = root_flags & mount_flags_desc[i].flag;
+ mount_flags_desc[i].apply(&cgrp_dfl_root, mount_flags_desc[i].flag, enable);
}
}
static int cgroup_show_options(struct seq_file *seq, struct kernfs_root *kf_root)
{
- if (cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE)
- seq_puts(seq, ",nsdelegate");
- if (cgrp_dfl_root.flags & CGRP_ROOT_FAVOR_DYNMODS)
- seq_puts(seq, ",favordynmods");
- if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS)
- seq_puts(seq, ",memory_localevents");
- if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT)
- seq_puts(seq, ",memory_recursiveprot");
- if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING)
- seq_puts(seq, ",memory_hugetlb_accounting");
- if (cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS)
- seq_puts(seq, ",pids_localevents");
+ int i;
+
+ for (i = 0; i < nr__cgroup2_params; ++i) {
+ if (cgrp_dfl_root.flags & mount_flags_desc[i].flag) {
+ seq_puts(seq, ",");
+ seq_puts(seq, mount_flags_desc[i].name);
+ }
+ }
return 0;
}
--
2.34.1
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