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Message-Id: <20250124-netcon_cpu-v3-4-12a0d286ba1d@debian.org>
Date: Fri, 24 Jan 2025 07:16:43 -0800
From: Breno Leitao <leitao@...ian.org>
To: Andrew Lunn <andrew+netdev@...n.ch>,
"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Simon Horman <horms@...nel.org>, Jonathan Corbet <corbet@....net>,
Shuah Khan <shuah@...nel.org>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
rdunlap@...radead.org, Breno Leitao <leitao@...ian.org>,
kernel-team@...a.com
Subject: [PATCH RFC net-next v3 4/8] netconsole: Introduce configfs helpers
for sysdata features
This patch introduces a bitfield to store sysdata features in the
netconsole_target struct. It also adds configfs helpers to enable
or disable the CPU_NR feature, which populates the CPU number in
sysdata.
The patch provides the necessary infrastructure to set or unset the
CPU_NR feature, but does not modify the message itself.
Signed-off-by: Breno Leitao <leitao@...ian.org>
---
drivers/net/netconsole.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 81 insertions(+)
diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 1c197da806962a751a3da8794def6a97cff5f701..4cefa43555aada25769b705dd8c8c89964f51a52 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -97,6 +97,15 @@ struct netconsole_target_stats {
struct u64_stats_sync syncp;
};
+/* Features enabled in sysdata. Contrary to userdata, this data is populated by
+ * the kernel. The fields are designed as bitwise flags, allowing multiple
+ * features to be set in sysdata_fields.
+ */
+enum sysdata_feature {
+ /* Populate the CPU that sends the message */
+ CPU_NR = BIT(0),
+};
+
/**
* struct netconsole_target - Represents a configured netconsole target.
* @list: Links this target into the target_list.
@@ -104,6 +113,7 @@ struct netconsole_target_stats {
* @userdata_group: Links to the userdata configfs hierarchy
* @extradata_complete: Cached, formatted string of append
* @userdata_length: String length of usedata in extradata_complete.
+ * @sysdata_fields: Sysdata features enabled.
* @stats: Packet send stats for the target. Used for debugging.
* @enabled: On / off knob to enable / disable target.
* Visible from userspace (read-write).
@@ -131,6 +141,8 @@ struct netconsole_target {
struct config_group userdata_group;
char extradata_complete[MAX_EXTRADATA_ENTRY_LEN * MAX_EXTRADATA_ITEMS];
size_t userdata_length;
+ /* bit-wise with sysdata_feature bits */
+ u32 sysdata_fields;
#endif
struct netconsole_target_stats stats;
bool enabled;
@@ -398,6 +410,19 @@ static ssize_t transmit_errors_show(struct config_item *item, char *buf)
return sysfs_emit(buf, "%llu\n", xmit_drop_count + enomem_count);
}
+/* configfs helper to display if cpu_nr sysdata feature is enabled */
+static ssize_t sysdata_cpu_nr_show(struct config_item *item, char *buf)
+{
+ struct netconsole_target *nt = to_target(item->ci_parent);
+ bool cpu_nr_enabled;
+
+ mutex_lock(&dynamic_netconsole_mutex);
+ cpu_nr_enabled = nt->sysdata_fields & CPU_NR;
+ mutex_unlock(&dynamic_netconsole_mutex);
+
+ return sysfs_emit(buf, "%d\n", cpu_nr_enabled);
+}
+
/*
* This one is special -- targets created through the configfs interface
* are not enabled (and the corresponding netpoll activated) by default.
@@ -792,7 +817,62 @@ static ssize_t userdatum_value_store(struct config_item *item, const char *buf,
return ret;
}
+/* disable_sysdata_feature - Disable sysdata feature and clean sysdata
+ * @nt: target that is diabling the feature
+ * @feature: feature being disabled
+ */
+static void disable_sysdata_feature(struct netconsole_target *nt,
+ enum sysdata_feature feature)
+{
+ nt->sysdata_fields &= ~feature;
+ nt->extradata_complete[nt->userdata_length] = 0;
+}
+
+/* configfs helper to sysdata cpu_nr feature */
+static ssize_t sysdata_cpu_nr_store(struct config_item *item, const char *buf,
+ size_t count)
+{
+ struct netconsole_target *nt = to_target(item->ci_parent);
+ bool cpu_nr_enabled, curr;
+ ssize_t ret;
+
+ ret = kstrtobool(buf, &cpu_nr_enabled);
+ if (ret)
+ return ret;
+
+ mutex_lock(&dynamic_netconsole_mutex);
+ curr = nt->sysdata_fields & CPU_NR;
+ if (cpu_nr_enabled == curr)
+ /* no change requested */
+ goto unlock_ok;
+
+ if (cpu_nr_enabled &&
+ count_extradata_entries(nt) >= MAX_EXTRADATA_ITEMS) {
+ /* user wants the new feature, but there is no space in the
+ * buffer.
+ */
+ ret = -ENOSPC;
+ goto unlock;
+ }
+
+ if (cpu_nr_enabled)
+ nt->sysdata_fields |= CPU_NR;
+ else
+ /* This is special because extradata_complete might have
+ * remaining data from previous sysdata, and it needs to be
+ * cleaned.
+ */
+ disable_sysdata_feature(nt, CPU_NR);
+
+unlock_ok:
+ ret = strnlen(buf, count);
+unlock:
+ mutex_unlock(&dynamic_netconsole_mutex);
+ return ret;
+}
+
CONFIGFS_ATTR(userdatum_, value);
+CONFIGFS_ATTR(sysdata_, cpu_nr);
static struct configfs_attribute *userdatum_attrs[] = {
&userdatum_attr_value,
@@ -852,6 +932,7 @@ static void userdatum_drop(struct config_group *group, struct config_item *item)
}
static struct configfs_attribute *userdata_attrs[] = {
+ &sysdata_attr_cpu_nr,
NULL,
};
--
2.43.5
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