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Subject[PATCH v5 3/6] powerpc/fadump: reorganize /sys/kernel/fadump_* sysfs files
Date
As the number of FADump sysfs files increases it is hard to manage all of
them inside /sys/kernel directory. It's better to have all the FADump
related sysfs files in a dedicated directory /sys/kernel/fadump. But in
order to maintain backward compatibility a symlink has been added for every
sysfs that has moved to new location.

As the FADump sysfs files are now part of a dedicated directory there is no
need to prefix their name with fadump_, hence sysfs file names are also
updated. For example fadump_enabled sysfs file is now referred as enabled.

Also consolidate ABI documentation for all the FADump sysfs files in a
single file Documentation/ABI/testing/sysfs-kernel-fadump.

Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
---
Documentation/ABI/testing/sysfs-kernel-fadump | 33 +++++++
arch/powerpc/kernel/fadump.c | 95 ++++++++++++-------
2 files changed, 94 insertions(+), 34 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-kernel-fadump

diff --git a/Documentation/ABI/testing/sysfs-kernel-fadump b/Documentation/ABI/testing/sysfs-kernel-fadump
new file mode 100644
index 000000000000..5d988b919e81
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-fadump
@@ -0,0 +1,33 @@
+What: /sys/kernel/fadump/*
+Date: Dec 2019
+Contact: linuxppc-dev@lists.ozlabs.org
+Description:
+ The /sys/kernel/fadump/* is a collection of FADump sysfs
+ file provide information about the configuration status
+ of Firmware Assisted Dump (FADump).
+
+What: /sys/kernel/fadump/enabled
+Date: Dec 2019
+Contact: linuxppc-dev@lists.ozlabs.org
+Description: read only
+ Primarily used to identify whether the FADump is enabled in
+ the kernel or not.
+User: Kdump service
+
+What: /sys/kernel/fadump/registered
+Date: Dec 2019
+Contact: linuxppc-dev@lists.ozlabs.org
+Description: read/write
+ Helps to control the dump collect feature from userspace.
+ Setting 1 to this file enables the system to collect the
+ dump and 0 to disable it.
+User: Kdump service
+
+What: /sys/kernel/fadump/release_mem
+Date: Dec 2019
+Contact: linuxppc-dev@lists.ozlabs.org
+Description: write only
+ This is a special sysfs file and only available when
+ the system is booted to capture the vmcore using FADump.
+ It is used to release the memory reserved by FADump to
+ save the crash dump.
diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index ed59855430b9..35ecb51edc50 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -44,6 +44,13 @@ struct fadump_mrange_info reserved_mrange_info = { "reserved", NULL, 0, 0, 0 };
#ifdef CONFIG_CMA
static struct cma *fadump_cma;

+#define CREATE_SYMLINK(target, symlink_name) do {\
+ rc = compat_only_sysfs_link_entry_to_kobj(kernel_kobj, fadump_kobj, \
+ target, symlink_name); \
+ if (rc) \
+ pr_err("unable to create %s symlink (%d)", symlink_name, rc); \
+} while (0)
+
/*
* fadump_cma_init() - Initialize CMA area from a fadump reserved memory
*
@@ -1323,9 +1330,9 @@ static void fadump_invalidate_release_mem(void)
fw_dump.ops->fadump_init_mem_struct(&fw_dump);
}

-static ssize_t fadump_release_memory_store(struct kobject *kobj,
- struct kobj_attribute *attr,
- const char *buf, size_t count)
+static ssize_t release_mem_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
{
int input = -1;

@@ -1350,23 +1357,23 @@ static ssize_t fadump_release_memory_store(struct kobject *kobj,
return count;
}

-static ssize_t fadump_enabled_show(struct kobject *kobj,
- struct kobj_attribute *attr,
- char *buf)
+static ssize_t enabled_show(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ char *buf)
{
return sprintf(buf, "%d\n", fw_dump.fadump_enabled);
}

-static ssize_t fadump_register_show(struct kobject *kobj,
- struct kobj_attribute *attr,
- char *buf)
+static ssize_t registered_show(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ char *buf)
{
return sprintf(buf, "%d\n", fw_dump.dump_registered);
}

-static ssize_t fadump_register_store(struct kobject *kobj,
- struct kobj_attribute *attr,
- const char *buf, size_t count)
+static ssize_t registered_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
{
int ret = 0;
int input = -1;
@@ -1418,15 +1425,22 @@ static int fadump_region_show(struct seq_file *m, void *private)
return 0;
}

-static struct kobj_attribute fadump_release_attr = __ATTR(fadump_release_mem,
- 0200, NULL,
- fadump_release_memory_store);
-static struct kobj_attribute fadump_attr = __ATTR(fadump_enabled,
- 0444, fadump_enabled_show,
- NULL);
-static struct kobj_attribute fadump_register_attr = __ATTR(fadump_registered,
- 0644, fadump_register_show,
- fadump_register_store);
+struct kobject *fadump_kobj;
+EXPORT_SYMBOL_GPL(fadump_kobj);
+
+static struct kobj_attribute release_attr = __ATTR_WO(release_mem);
+static struct kobj_attribute enable_attr = __ATTR_RO(enabled);
+static struct kobj_attribute register_attr = __ATTR_RW(registered);
+
+static struct attribute *fadump_attrs[] = {
+ &enable_attr.attr,
+ &register_attr.attr,
+ NULL,
+};
+
+static struct attribute_group fadump_group = {
+ .attrs = fadump_attrs,
+};

DEFINE_SHOW_ATTRIBUTE(fadump_region);

@@ -1435,16 +1449,11 @@ static void fadump_init_files(void)
struct dentry *debugfs_file;
int rc = 0;

- rc = sysfs_create_file(kernel_kobj, &fadump_attr.attr);
- if (rc)
- printk(KERN_ERR "fadump: unable to create sysfs file"
- " fadump_enabled (%d)\n", rc);
-
- rc = sysfs_create_file(kernel_kobj, &fadump_register_attr.attr);
- if (rc)
- printk(KERN_ERR "fadump: unable to create sysfs file"
- " fadump_registered (%d)\n", rc);
-
+ fadump_kobj = kobject_create_and_add("fadump", kernel_kobj);
+ if (!fadump_kobj) {
+ pr_err("failed to create fadump kobject\n");
+ return;
+ }
debugfs_file = debugfs_create_file("fadump_region", 0444,
powerpc_debugfs_root, NULL,
&fadump_region_fops);
@@ -1453,11 +1462,29 @@ static void fadump_init_files(void)
" fadump_region\n");

if (fw_dump.dump_active) {
- rc = sysfs_create_file(kernel_kobj, &fadump_release_attr.attr);
+ rc = sysfs_create_file(fadump_kobj, &release_attr.attr);
if (rc)
- printk(KERN_ERR "fadump: unable to create sysfs file"
- " fadump_release_mem (%d)\n", rc);
+ pr_err("unable to create release_mem sysfs file (%d)\n",
+ rc);
}
+
+ rc = sysfs_create_group(fadump_kobj, &fadump_group);
+ if (rc) {
+ pr_err("sysfs group creation failed (%d)", rc);
+ return;
+ }
+
+ /* The FADump sysfs are moved from kernel_kobj to fadump_kobj need to
+ * create symlink at old location to maintain backward compatibility.
+ *
+ * - fadump_enabled -> fadump/enabled
+ * - fadump_registered -> fadump/registered
+ * - fadump_release_mem -> fadump/release_mem
+ */
+ CREATE_SYMLINK("enabled", "fadump_enabled");
+ CREATE_SYMLINK("registered", "fadump_registered");
+ if (fw_dump.dump_active)
+ CREATE_SYMLINK("release_mem", "fadump_release_mem");
return;
}

--
2.17.2
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