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[PATCH v5 12/18] x86/intel_rdt: Add "info" files to resctrl file system

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  [PATCH v5 12/18] x86/intel_rdt: Add "info" files to resctrl file system "Fenghua Yu" <fenghua.yu@intel.com> - 2016-10-22 15:30 +0200
    Re: [PATCH v5 12/18] x86/intel_rdt: Add "info" files to resctrl file  system Thomas Gleixner <tglx@linutronix.de> - 2016-10-26 16:50 +0200
      Re: [PATCH v5 12/18] x86/intel_rdt: Add "info" files to resctrl  file system "Luck, Tony" <tony.luck@intel.com> - 2016-10-26 17:50 +0200
        Re: [PATCH v5 12/18] x86/intel_rdt: Add "info" files to resctrl file  system Thomas Gleixner <tglx@linutronix.de> - 2016-10-26 19:40 +0200
      Re: [PATCH v5 12/18] x86/intel_rdt: Add "info" files to resctrl file  system Fenghua Yu <fenghua.yu@intel.com> - 2016-10-27 20:20 +0200
        Re: [PATCH v5 12/18] x86/intel_rdt: Add "info" files to resctrl file  system Thomas Gleixner <tglx@linutronix.de> - 2016-10-27 20:30 +0200
          Re: [PATCH v5 12/18] x86/intel_rdt: Add "info" files to resctrl file  system Fenghua Yu <fenghua.yu@intel.com> - 2016-10-27 20:40 +0200

#1506514 — [PATCH v5 12/18] x86/intel_rdt: Add "info" files to resctrl file system

From: Fenghua Yu <fenghua.yu@intel.com>

For the convenience of applications we make the decoded values of some
of the CPUID values available in read-only (0444) files.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
---
 arch/x86/include/asm/intel_rdt.h         |  24 ++++
 arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 186 +++++++++++++++++++++++++++++++
 2 files changed, 210 insertions(+)

diff --git a/arch/x86/include/asm/intel_rdt.h b/arch/x86/include/asm/intel_rdt.h
index 8e1d002..39ed561 100644
--- a/arch/x86/include/asm/intel_rdt.h
+++ b/arch/x86/include/asm/intel_rdt.h
@@ -25,6 +25,30 @@ extern struct list_head rdt_all_groups;
 int __init rdtgroup_init(void);
 
 /**
+ * struct rftype - describe each file in the resctrl file system
+ * @name: file name
+ * @mode: access mode
+ * @kf_ops: operations
+ * @seq_show: show content of the file
+ * @write: write to the file
+ */
+struct rftype {
+	char			*name;
+	umode_t			mode;
+	struct kernfs_ops	*kf_ops;
+
+	int (*seq_show)(struct kernfs_open_file *of,
+			struct seq_file *sf, void *v);
+	/*
+	 * write() is the generic write callback which maps directly to
+	 * kernfs write operation and overrides all other operations.
+	 * Maximum write size is determined by ->max_write_len.
+	 */
+	ssize_t (*write)(struct kernfs_open_file *of,
+			 char *buf, size_t nbytes, loff_t off);
+};
+
+/**
  * struct rdt_resource - attributes of an RDT resource
  * @enabled:			Is this feature enabled on this machine
  * @capable:			Is this feature available on this machine
diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index 6c9061d..dd0d584 100644
--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -23,6 +23,8 @@
 #include <linux/fs.h>
 #include <linux/sysfs.h>
 #include <linux/kernfs.h>
+#include <linux/seq_file.h>
+#include <linux/sched.h>
 #include <linux/slab.h>
 
 #include <uapi/linux/magic.h>
@@ -34,6 +36,176 @@ struct kernfs_root *rdt_root;
 struct rdtgroup rdtgroup_default;
 LIST_HEAD(rdt_all_groups);
 
+/* Kernel fs node for "info" directory under root */
+static struct kernfs_node *kn_info;
+
+/* set uid and gid of rdtgroup dirs and files to that of the creator */
+static int rdtgroup_kn_set_ugid(struct kernfs_node *kn)
+{
+	struct iattr iattr = { .ia_valid = ATTR_UID | ATTR_GID,
+				.ia_uid = current_fsuid(),
+				.ia_gid = current_fsgid(), };
+
+	if (uid_eq(iattr.ia_uid, GLOBAL_ROOT_UID) &&
+	    gid_eq(iattr.ia_gid, GLOBAL_ROOT_GID))
+		return 0;
+
+	return kernfs_setattr(kn, &iattr);
+}
+
+static int rdtgroup_add_file(struct kernfs_node *parent_kn, struct rftype *rft)
+{
+	struct kernfs_node *kn;
+	int ret;
+
+	kn = __kernfs_create_file(parent_kn, rft->name, rft->mode,
+				  0, rft->kf_ops, rft, NULL, NULL);
+	if (IS_ERR(kn))
+		return PTR_ERR(kn);
+
+	ret = rdtgroup_kn_set_ugid(kn);
+	if (ret) {
+		kernfs_remove(kn);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int rdtgroup_add_files(struct kernfs_node *kn, struct rftype *rfts,
+			      int len)
+{
+	struct rftype *rft;
+	int ret;
+
+	lockdep_assert_held(&rdtgroup_mutex);
+
+	for (rft = rfts; rft < rfts + len; rft++) {
+		ret = rdtgroup_add_file(kn, rft);
+		if (ret)
+			goto error;
+	}
+
+	return 0;
+error:
+	pr_warn("%s: failed to add %s, err=%d\n", __func__, rft->name, ret);
+	while (--rft >= rfts)
+		kernfs_remove_by_name(kn, rft->name);
+	return ret;
+}
+
+static int rdtgroup_seqfile_show(struct seq_file *m, void *arg)
+{
+	struct kernfs_open_file *of = m->private;
+	struct rftype *rft = of->kn->priv;
+
+	if (rft->seq_show)
+		return rft->seq_show(of, m, arg);
+	return 0;
+}
+
+static ssize_t rdtgroup_file_write(struct kernfs_open_file *of, char *buf,
+				   size_t nbytes, loff_t off)
+{
+	struct rftype *rft = of->kn->priv;
+
+	if (rft->write)
+		return rft->write(of, buf, nbytes, off);
+
+	return -EINVAL;
+}
+
+static struct kernfs_ops rdtgroup_kf_single_ops = {
+	.atomic_write_len	= PAGE_SIZE,
+	.write			= rdtgroup_file_write,
+	.seq_show		= rdtgroup_seqfile_show,
+};
+
+static int rdt_num_closid_show(struct kernfs_open_file *of,
+			       struct seq_file *seq, void *v)
+{
+	struct rdt_resource *r = of->kn->parent->priv;
+
+	seq_printf(seq, "%d\n", r->num_closid);
+
+	return 0;
+}
+
+static int rdt_cbm_val_show(struct kernfs_open_file *of,
+			    struct seq_file *seq, void *v)
+{
+	struct rdt_resource *r = of->kn->parent->priv;
+
+	seq_printf(seq, "%x\n", r->max_cbm);
+
+	return 0;
+}
+
+/* rdtgroup information files for one cache resource. */
+static struct rftype res_info_files[] = {
+	{
+		.name		= "num_closid",
+		.mode		= 0444,
+		.kf_ops		= &rdtgroup_kf_single_ops,
+		.seq_show	= rdt_num_closid_show,
+	},
+	{
+		.name		= "cbm_val",
+		.mode		= 0444,
+		.kf_ops		= &rdtgroup_kf_single_ops,
+		.seq_show	= rdt_cbm_val_show,
+	},
+};
+
+static int rdtgroup_create_info_dir(struct kernfs_node *parent_kn)
+{
+	struct kernfs_node *kn_subdir;
+	struct rdt_resource *r;
+	int ret;
+
+	/* create the directory */
+	kn_info = kernfs_create_dir(parent_kn, "info", parent_kn->mode, NULL);
+	if (IS_ERR(kn_info))
+		return PTR_ERR(kn_info);
+	kernfs_get(kn_info);
+
+	for_each_enabled_rdt_resource(r) {
+		kn_subdir = kernfs_create_dir(kn_info, r->name,
+					      kn_info->mode, r);
+		if (IS_ERR(kn_subdir)) {
+			ret = PTR_ERR(kn_subdir);
+			goto out_destroy;
+		}
+		kernfs_get(kn_subdir);
+		ret = rdtgroup_kn_set_ugid(kn_subdir);
+		if (ret)
+			goto out_destroy;
+		ret = rdtgroup_add_files(kn_subdir, res_info_files,
+					 ARRAY_SIZE(res_info_files));
+		if (ret)
+			goto out_destroy;
+		kernfs_activate(kn_subdir);
+	}
+
+	/*
+	 * This extra ref will be put in kernfs_remove() and guarantees
+	 * that @rdtgrp->kn is always accessible.
+	 */
+	kernfs_get(kn_info);
+
+	ret = rdtgroup_kn_set_ugid(kn_info);
+	if (ret)
+		goto out_destroy;
+
+	kernfs_activate(kn_info);
+
+	return 0;
+
+out_destroy:
+	kernfs_remove(kn_info);
+	return ret;
+}
+
 static void l3_qos_cfg_update(void *arg)
 {
 	bool enable = *(bool *)arg;
@@ -121,6 +293,10 @@ static struct dentry *rdt_mount(struct file_system_type *fs_type,
 		goto out;
 	}
 
+	ret = rdtgroup_create_info_dir(rdtgroup_default.kn);
+	if (ret)
+		goto out;
+
 	dentry = kernfs_mount(fs_type, flags, rdt_root,
 			      RDTGROUP_SUPER_MAGIC, NULL);
 	if (IS_ERR(dentry))
@@ -177,6 +353,14 @@ static int reset_all_cbms(struct rdt_resource *r)
 	return 0;
 }
 
+/*
+ * Forcibly remove all of subdirectories under root.
+ */
+static void rmdir_all_sub(void)
+{
+	kernfs_remove(kn_info);
+}
+
 static void rdt_kill_sb(struct super_block *sb)
 {
 	struct rdt_resource *r;
@@ -194,6 +378,7 @@ static void rdt_kill_sb(struct super_block *sb)
 		set_l3_qos_cfg(r, false);
 	}
 
+	rmdir_all_sub();
 	static_branch_disable(&rdt_enable_key);
 	kernfs_kill_sb(sb);
 	mutex_unlock(&rdtgroup_mutex);
@@ -224,6 +409,7 @@ static int __init rdtgroup_setup_root(void)
 	rdtgroup_default.kn = rdt_root->kn;
 	kernfs_activate(rdtgroup_default.kn);
 
+out:
 	mutex_unlock(&rdtgroup_mutex);
 
 	return 0;
-- 
2.5.0

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#1509494 — Re: [PATCH v5 12/18] x86/intel_rdt: Add "info" files to resctrl file system

On Sat, 22 Oct 2016, Fenghua Yu wrote:
> +static int rdtgroup_add_files(struct kernfs_node *kn, struct rftype *rfts,
> +			      int len)
> +{
> +	struct rftype *rft;
> +	int ret;
> +
> +	lockdep_assert_held(&rdtgroup_mutex);
> +
> +	for (rft = rfts; rft < rfts + len; rft++) {
> +		ret = rdtgroup_add_file(kn, rft);
> +		if (ret)
> +			goto error;
> +	}
> +
> +	return 0;
> +error:
> +	pr_warn("%s: failed to add %s, err=%d\n", __func__, rft->name, ret);

Please stop this silly __func__ nonsense. You already have a prefix and if
you write out a proper sentence describing the problem then it's way more
helpful than __func__

	pr_warn("Failed to add file %s, err %d\n" ....

Tells exactly what happened and for a sysadmin this is information enough
as he does not care at all in which function that happens. For the
developer who is poked by that admin it's easy enough to find the function
via the string.

> +/* rdtgroup information files for one cache resource. */
> +static struct rftype res_info_files[] = {
> +	{
> +		.name		= "num_closid",

num_closids please

> +		.mode		= 0444,
> +		.kf_ops		= &rdtgroup_kf_single_ops,
> +		.seq_show	= rdt_num_closid_show,
> +	},
> +	{
> +		.name		= "cbm_val",

cbm_val? Is that a value? No, it's the valid bitmask which you can set. So
cmb_mask or something else which is unambiguous is what you want here.

This is a user space interface and we really must make it as intuitive as
possible.

> +/*
> + * Forcibly remove all of subdirectories under root.
> + */
> +static void rmdir_all_sub(void)
> +{
> +	kernfs_remove(kn_info);

What clears kn_info?

Thanks,

	tglx

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#1509540 — Re: [PATCH v5 12/18] x86/intel_rdt: Add "info" files to resctrl file system

> 
>> +        .mode        = 0444,
>> +        .kf_ops        = &rdtgroup_kf_single_ops,
>> +        .seq_show    = rdt_num_closid_show,
>> +    },
>> +    {
>> +        .name        = "cbm_val",
> 
> cbm_val? Is that a value? No, it's the valid bitmask which you can set. So
> cmb_mask or something else which is unambiguous is what you want here.
> 
> This is a user space interface and we really must make it as intuitive as
> possible.

It's a bit mask for cache resources. But this interface will also control resources that are not caches, so I'd like to avoid "cbm" in the name. Perhaps "max_val"?

-Tony

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#1509638 — Re: [PATCH v5 12/18] x86/intel_rdt: Add "info" files to resctrl file system

On Wed, 26 Oct 2016, Luck, Tony wrote:
> >> +        .mode        = 0444,
> >> +        .kf_ops        = &rdtgroup_kf_single_ops,
> >> +        .seq_show    = rdt_num_closid_show,
> >> +    },
> >> +    {
> >> +        .name        = "cbm_val",
> > 
> > cbm_val? Is that a value? No, it's the valid bitmask which you can set. So
> > cmb_mask or something else which is unambiguous is what you want here.
> > 
> > This is a user space interface and we really must make it as intuitive as
> > possible.
> 
> It's a bit mask for cache resources. But this interface will also control resources that are not caches, so I'd like to avoid "cbm" in the name. Perhaps "max_val"?
> 

max_val is misleading if it's always a bit mask. 'bitmask' might not be the
worst choice then.

Thanks,

	tglx

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#1510558 — Re: [PATCH v5 12/18] x86/intel_rdt: Add "info" files to resctrl file system

On Wed, Oct 26, 2016 at 04:45:50PM +0200, Thomas Gleixner wrote:
> On Sat, 22 Oct 2016, Fenghua Yu wrote:
> > +/*
> > + * Forcibly remove all of subdirectories under root.
> > + */
> > +static void rmdir_all_sub(void)
> > +{
> > +	kernfs_remove(kn_info);
> 
> What clears kn_info?

Is the question "Why clears kn_info?"

kn_info is created during mount time and has different contents
under "info" directory with CDP enabled or disabled by mount parameter "cdp".

umount needs to remove kn_info so that it's ready to be created next time
during mount time. So user can do CAT mount, check "info", umount, and then
CDP mount, check "info". The user will see different contents in two "info"
checks.

Thanks.

-Fenghua

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#1510565 — Re: [PATCH v5 12/18] x86/intel_rdt: Add "info" files to resctrl file system

On Thu, 27 Oct 2016, Fenghua Yu wrote:

> On Wed, Oct 26, 2016 at 04:45:50PM +0200, Thomas Gleixner wrote:
> > On Sat, 22 Oct 2016, Fenghua Yu wrote:
> > > +/*
> > > + * Forcibly remove all of subdirectories under root.
> > > + */
> > > +static void rmdir_all_sub(void)
> > > +{
> > > +	kernfs_remove(kn_info);
> > 
> > What clears kn_info?
> 
> Is the question "Why clears kn_info?"
> 
> kn_info is created during mount time and has different contents
> under "info" directory with CDP enabled or disabled by mount parameter "cdp".
> 
> umount needs to remove kn_info so that it's ready to be created next time
> during mount time. So user can do CAT mount, check "info", umount, and then
> CDP mount, check "info". The user will see different contents in two "info"
> checks.

Lemme rephrase. What does: kn_info = NULL; ?

We should clear static variables for correctness sake. The current code has
no problem with that, but 5 month down the road something is going to trip
over the stale reference.

Thanks,

	tglx

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#1510569 — Re: [PATCH v5 12/18] x86/intel_rdt: Add "info" files to resctrl file system

On Thu, Oct 27, 2016 at 08:25:57PM +0200, Thomas Gleixner wrote:
> 
> 
> On Thu, 27 Oct 2016, Fenghua Yu wrote:
> 
> > On Wed, Oct 26, 2016 at 04:45:50PM +0200, Thomas Gleixner wrote:
> > > On Sat, 22 Oct 2016, Fenghua Yu wrote:
> > > > +/*
> > > > + * Forcibly remove all of subdirectories under root.
> > > > + */
> > > > +static void rmdir_all_sub(void)
> > > > +{
> > > > +	kernfs_remove(kn_info);
> > > 
> > > What clears kn_info?
> > 
> > Is the question "Why clears kn_info?"
> > 
> > kn_info is created during mount time and has different contents
> > under "info" directory with CDP enabled or disabled by mount parameter "cdp".
> > 
> > umount needs to remove kn_info so that it's ready to be created next time
> > during mount time. So user can do CAT mount, check "info", umount, and then
> > CDP mount, check "info". The user will see different contents in two "info"
> > checks.
> 
> Lemme rephrase. What does: kn_info = NULL; ?
> 
> We should clear static variables for correctness sake. The current code has
> no problem with that, but 5 month down the road something is going to trip
> over the stale reference.
> 
> Thanks,
> 
> 	tglx

Ok. I see. I'll add kn_info = NULL after kernfs_remove().

Thanks.

-Fenghua

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