Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull vfs mount infrastructure updates from Al Viro:
 "The rest of core infrastructure; no new syscalls in that pile, but the
  old parts are switched to new infrastructure. At that point
  conversions of individual filesystems can happen independently; some
  are done here (afs, cgroup, procfs, etc.), there's also a large series
  outside of that pile dealing with NFS (quite a bit of option-parsing
  stuff is getting used there - it's one of the most convoluted
  filesystems in terms of mount-related logics), but NFS bits are the
  next cycle fodder.

  It got seriously simplified since the last cycle; documentation is
  probably the weakest bit at the moment - I considered dropping the
  commit introducing Documentation/filesystems/mount_api.txt (cutting
  the size increase by quarter ;-), but decided that it would be better
  to fix it up after -rc1 instead.

  That pile allows to do followup work in independent branches, which
  should make life much easier for the next cycle. fs/super.c size
  increase is unpleasant; there's a followup series that allows to
  shrink it considerably, but I decided to leave that until the next
  cycle"

* 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (41 commits)
  afs: Use fs_context to pass parameters over automount
  afs: Add fs_context support
  vfs: Add some logging to the core users of the fs_context log
  vfs: Implement logging through fs_context
  vfs: Provide documentation for new mount API
  vfs: Remove kern_mount_data()
  hugetlbfs: Convert to fs_context
  cpuset: Use fs_context
  kernfs, sysfs, cgroup, intel_rdt: Support fs_context
  cgroup: store a reference to cgroup_ns into cgroup_fs_context
  cgroup1_get_tree(): separate "get cgroup_root to use" into a separate helper
  cgroup_do_mount(): massage calling conventions
  cgroup: stash cgroup_root reference into cgroup_fs_context
  cgroup2: switch to option-by-option parsing
  cgroup1: switch to option-by-option parsing
  cgroup: take options parsing into ->parse_monolithic()
  cgroup: fold cgroup1_mount() into cgroup1_get_tree()
  cgroup: start switching to fs_context
  ipc: Convert mqueue fs to fs_context
  proc: Add fs_context support to procfs
  ...

2 files changed, 132 insertions, 69 deletions

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 822b7db634ee..e49b77283924 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -4,6 +4,7 @@
 
 #include <linux/sched.h>
 #include <linux/kernfs.h>
+#include <linux/fs_context.h>
 #include <linux/jump_label.h>
 
 #define MSR_IA32_L3_QOS_CFG		0xc81
@@ -40,6 +41,21 @@
 #define RMID_VAL_ERROR			BIT_ULL(63)
 #define RMID_VAL_UNAVAIL		BIT_ULL(62)
 
+
+struct rdt_fs_context {
+	struct kernfs_fs_context	kfc;
+	bool				enable_cdpl2;
+	bool				enable_cdpl3;
+	bool				enable_mba_mbps;
+};
+
+static inline struct rdt_fs_context *rdt_fc2context(struct fs_context *fc)
+{
+	struct kernfs_fs_context *kfc = fc->fs_private;
+
+	return container_of(kfc, struct rdt_fs_context, kfc);
+}
+
 DECLARE_STATIC_KEY_FALSE(rdt_enable_key);
 
 /**
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 8388adf241b2..399601eda8e4 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -24,6 +24,7 @@
 #include <linux/cpu.h>
 #include <linux/debugfs.h>
 #include <linux/fs.h>
+#include <linux/fs_parser.h>
 #include <linux/sysfs.h>
 #include <linux/kernfs.h>
 #include <linux/seq_buf.h>
@@ -32,6 +33,7 @@
 #include <linux/sched/task.h>
 #include <linux/slab.h>
 #include <linux/task_work.h>
+#include <linux/user_namespace.h>
 
 #include <uapi/linux/magic.h>
 
@@ -1858,46 +1860,6 @@ static void cdp_disable_all(void)
 		cdpl2_disable();
 }
 
-static int parse_rdtgroupfs_options(char *data)
-{
-	char *token, *o = data;
-	int ret = 0;
-
-	while ((token = strsep(&o, ",")) != NULL) {
-		if (!*token) {
-			ret = -EINVAL;
-			goto out;
-		}
-
-		if (!strcmp(token, "cdp")) {
-			ret = cdpl3_enable();
-			if (ret)
-				goto out;
-		} else if (!strcmp(token, "cdpl2")) {
-			ret = cdpl2_enable();
-			if (ret)
-				goto out;
-		} else if (!strcmp(token, "mba_MBps")) {
-			if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
-				ret = set_mba_sc(true);
-			else
-				ret = -EINVAL;
-			if (ret)
-				goto out;
-		} else {
-			ret = -EINVAL;
-			goto out;
-		}
-	}
-
-	return 0;
-
-out:
-	pr_err("Invalid mount option \"%s\"\n", token);
-
-	return ret;
-}
-
 /*
  * We don't allow rdtgroup directories to be created anywhere
  * except the root directory. Thus when looking for the rdtgroup
@@ -1969,13 +1931,27 @@ static int mkdir_mondata_all(struct kernfs_node *parent_kn,
 			     struct rdtgroup *prgrp,
 			     struct kernfs_node **mon_data_kn);
 
-static struct dentry *rdt_mount(struct file_system_type *fs_type,
-				int flags, const char *unused_dev_name,
-				void *data)
+static int rdt_enable_ctx(struct rdt_fs_context *ctx)
+{
+	int ret = 0;
+
+	if (ctx->enable_cdpl2)
+		ret = cdpl2_enable();
+
+	if (!ret && ctx->enable_cdpl3)
+		ret = cdpl3_enable();
+
+	if (!ret && ctx->enable_mba_mbps)
+		ret = set_mba_sc(true);
+
+	return ret;
+}
+
+static int rdt_get_tree(struct fs_context *fc)
 {
+	struct rdt_fs_context *ctx = rdt_fc2context(fc);
 	struct rdt_domain *dom;
 	struct rdt_resource *r;
-	struct dentry *dentry;
 	int ret;
 
 	cpus_read_lock();
@@ -1984,53 +1960,42 @@ static struct dentry *rdt_mount(struct file_system_type *fs_type,
 	 * resctrl file system can only be mounted once.
 	 */
 	if (static_branch_unlikely(&rdt_enable_key)) {
-		dentry = ERR_PTR(-EBUSY);
+		ret = -EBUSY;
 		goto out;
 	}
 
-	ret = parse_rdtgroupfs_options(data);
-	if (ret) {
-		dentry = ERR_PTR(ret);
+	ret = rdt_enable_ctx(ctx);
+	if (ret < 0)
 		goto out_cdp;
-	}
 
 	closid_init();
 
 	ret = rdtgroup_create_info_dir(rdtgroup_default.kn);
-	if (ret) {
-		dentry = ERR_PTR(ret);
-		goto out_cdp;
-	}
+	if (ret < 0)
+		goto out_mba;
 
 	if (rdt_mon_capable) {
 		ret = mongroup_create_dir(rdtgroup_default.kn,
 					  NULL, "mon_groups",
 					  &kn_mongrp);
-		if (ret) {
-			dentry = ERR_PTR(ret);
+		if (ret < 0)
 			goto out_info;
-		}
 		kernfs_get(kn_mongrp);
 
 		ret = mkdir_mondata_all(rdtgroup_default.kn,
 					&rdtgroup_default, &kn_mondata);
-		if (ret) {
-			dentry = ERR_PTR(ret);
+		if (ret < 0)
 			goto out_mongrp;
-		}
 		kernfs_get(kn_mondata);
 		rdtgroup_default.mon.mon_data_kn = kn_mondata;
 	}
 
 	ret = rdt_pseudo_lock_init();
-	if (ret) {
-		dentry = ERR_PTR(ret);
+	if (ret)
 		goto out_mondata;
-	}
 
-	dentry = kernfs_mount(fs_type, flags, rdt_root,
-			      RDTGROUP_SUPER_MAGIC, NULL);
-	if (IS_ERR(dentry))
+	ret = kernfs_get_tree(fc);
+	if (ret < 0)
 		goto out_psl;
 
 	if (rdt_alloc_capable)
@@ -2059,14 +2024,95 @@ out_mongrp:
 		kernfs_remove(kn_mongrp);
 out_info:
 	kernfs_remove(kn_info);
+out_mba:
+	if (ctx->enable_mba_mbps)
+		set_mba_sc(false);
 out_cdp:
 	cdp_disable_all();
 out:
 	rdt_last_cmd_clear();
 	mutex_unlock(&rdtgroup_mutex);
 	cpus_read_unlock();
+	return ret;
+}
+
+enum rdt_param {
+	Opt_cdp,
+	Opt_cdpl2,
+	Opt_mba_mpbs,
+	nr__rdt_params
+};
+
+static const struct fs_parameter_spec rdt_param_specs[] = {
+	fsparam_flag("cdp",		Opt_cdp),
+	fsparam_flag("cdpl2",		Opt_cdpl2),
+	fsparam_flag("mba_mpbs",	Opt_mba_mpbs),
+	{}
+};
+
+static const struct fs_parameter_description rdt_fs_parameters = {
+	.name		= "rdt",
+	.specs		= rdt_param_specs,
+};
+
+static int rdt_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+	struct rdt_fs_context *ctx = rdt_fc2context(fc);
+	struct fs_parse_result result;
+	int opt;
+
+	opt = fs_parse(fc, &rdt_fs_parameters, param, &result);
+	if (opt < 0)
+		return opt;
 
-	return dentry;
+	switch (opt) {
+	case Opt_cdp:
+		ctx->enable_cdpl3 = true;
+		return 0;
+	case Opt_cdpl2:
+		ctx->enable_cdpl2 = true;
+		return 0;
+	case Opt_mba_mpbs:
+		if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
+			return -EINVAL;
+		ctx->enable_mba_mbps = true;
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+static void rdt_fs_context_free(struct fs_context *fc)
+{
+	struct rdt_fs_context *ctx = rdt_fc2context(fc);
+
+	kernfs_free_fs_context(fc);
+	kfree(ctx);
+}
+
+static const struct fs_context_operations rdt_fs_context_ops = {
+	.free		= rdt_fs_context_free,
+	.parse_param	= rdt_parse_param,
+	.get_tree	= rdt_get_tree,
+};
+
+static int rdt_init_fs_context(struct fs_context *fc)
+{
+	struct rdt_fs_context *ctx;
+
+	ctx = kzalloc(sizeof(struct rdt_fs_context), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	ctx->kfc.root = rdt_root;
+	ctx->kfc.magic = RDTGROUP_SUPER_MAGIC;
+	fc->fs_private = &ctx->kfc;
+	fc->ops = &rdt_fs_context_ops;
+	if (fc->user_ns)
+		put_user_ns(fc->user_ns);
+	fc->user_ns = get_user_ns(&init_user_ns);
+	fc->global = true;
+	return 0;
 }
 
 static int reset_all_ctrls(struct rdt_resource *r)
@@ -2239,9 +2285,10 @@ static void rdt_kill_sb(struct super_block *sb)
 }
 
 static struct file_system_type rdt_fs_type = {
-	.name    = "resctrl",
-	.mount   = rdt_mount,
-	.kill_sb = rdt_kill_sb,
+	.name			= "resctrl",
+	.init_fs_context	= rdt_init_fs_context,
+	.parameters		= &rdt_fs_parameters,
+	.kill_sb		= rdt_kill_sb,
 };
 
 static int mon_addfile(struct kernfs_node *parent_kn, const char *name,