perf/x86/intel: Rename DMR offcore_rsp attribute to offmodule_rspgrafted

DMR introduces Offmodule Response events in place of the legacy
Offcore Response events, but it still exposes the inherited
offcore_rsp PMU attribute for programming the corresponding MSR data.

Rename the DMR PMU attribute to offmodule_rsp so the sysfs interface
matches the underlying event name and avoids user & tooling confusion.

Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://patch.msgid.link/20260917015234.981153-12-dapeng1.mi@linux.intel.com

1 files changed, 2454 insertions, 0 deletions

diff --git a/fs/super.c b/fs/super.c
new file mode 100644
index 000000000..9d4025213
--- /dev/null
+++ b/fs/super.c
@@ -0,0 +1,2454 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  linux/fs/super.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *
+ *  super.c contains code to handle: - mount structures
+ *                                   - super-block tables
+ *                                   - filesystem drivers list
+ *                                   - mount system call
+ *                                   - umount system call
+ *                                   - ustat system call
+ *
+ * GK 2/5/95  -  Changed to support mounting the root fs via NFS
+ *
+ *  Added kerneld support: Jacques Gelinas and Bjorn Ekwall
+ *  Added change_root: Werner Almesberger & Hans Lermen, Feb '96
+ *  Added options to /proc/mounts:
+ *    Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
+ *  Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998
+ *  Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000
+ */
+
+#include <linux/export.h>
+#include <linux/slab.h>
+#include <linux/blkdev.h>
+#include <linux/memcontrol.h>
+#include <linux/rhashtable.h>
+#include <linux/mount.h>
+#include <linux/security.h>
+#include <linux/writeback.h>		/* for the emergency remount stuff */
+#include <linux/idr.h>
+#include <linux/mutex.h>
+#include <linux/backing-dev.h>
+#include <linux/rculist_bl.h>
+#include <linux/fscrypt.h>
+#include <linux/fsnotify.h>
+#include <linux/lockdep.h>
+#include <linux/user_namespace.h>
+#include <linux/fs_context.h>
+#include <linux/fserror.h>
+#include <uapi/linux/mount.h>
+#include "internal.h"
+
+static int thaw_super_locked(struct super_block *sb, enum freeze_holder who,
+			     const void *freeze_owner);
+
+static LIST_HEAD(super_blocks);
+static DEFINE_SPINLOCK(sb_lock);
+
+static char *sb_writers_name[SB_FREEZE_LEVELS] = {
+	"sb_writers",
+	"sb_pagefaults",
+	"sb_internal",
+};
+
+static inline void __super_lock(struct super_block *sb, bool excl)
+{
+	if (excl)
+		down_write(&sb->s_umount);
+	else
+		down_read(&sb->s_umount);
+}
+
+static inline void super_unlock(struct super_block *sb, bool excl)
+{
+	if (excl)
+		up_write(&sb->s_umount);
+	else
+		up_read(&sb->s_umount);
+}
+
+static inline void __super_lock_excl(struct super_block *sb)
+{
+	__super_lock(sb, true);
+}
+
+static inline void super_unlock_excl(struct super_block *sb)
+{
+	super_unlock(sb, true);
+}
+
+static inline void super_unlock_shared(struct super_block *sb)
+{
+	super_unlock(sb, false);
+}
+
+static bool super_flags(const struct super_block *sb, unsigned int flags)
+{
+	/*
+	 * Pairs with smp_store_release() in super_wake() and ensures
+	 * that we see @flags after we're woken.
+	 */
+	return smp_load_acquire(&sb->s_flags) & flags;
+}
+
+/**
+ * super_lock - wait for superblock to become ready and lock it
+ * @sb: superblock to wait for
+ * @excl: whether exclusive access is required
+ *
+ * If the superblock has neither passed through vfs_get_tree() or
+ * generic_shutdown_super() yet wait for it to happen. Either superblock
+ * creation will succeed and SB_BORN is set by vfs_get_tree() or we're
+ * woken and we'll see SB_DYING.
+ *
+ * The caller must have acquired a temporary reference on @sb->s_passive.
+ *
+ * Return: The function returns true if SB_BORN was set and with
+ *         s_umount held. The function returns false if SB_DYING was
+ *         set and without s_umount held.
+ */
+static __must_check bool super_lock(struct super_block *sb, bool excl)
+{
+	lockdep_assert_not_held(&sb->s_umount);
+
+	/* wait until the superblock is ready or dying */
+	wait_var_event(&sb->s_flags, super_flags(sb, SB_BORN | SB_DYING));
+
+	/* Don't pointlessly acquire s_umount. */
+	if (super_flags(sb, SB_DYING))
+		return false;
+
+	__super_lock(sb, excl);
+
+	/*
+	 * Has gone through generic_shutdown_super() in the meantime.
+	 * @sb->s_root is NULL and @sb->s_active is 0. No one needs to
+	 * grab a reference to this. Tell them so.
+	 */
+	if (sb->s_flags & SB_DYING) {
+		super_unlock(sb, excl);
+		return false;
+	}
+
+	WARN_ON_ONCE(!(sb->s_flags & SB_BORN));
+	return true;
+}
+
+/* wait and try to acquire read-side of @sb->s_umount */
+static inline bool super_lock_shared(struct super_block *sb)
+{
+	return super_lock(sb, false);
+}
+
+/* wait and try to acquire write-side of @sb->s_umount */
+static inline bool super_lock_excl(struct super_block *sb)
+{
+	return super_lock(sb, true);
+}
+
+/* wake waiters */
+#define SUPER_WAKE_FLAGS (SB_BORN | SB_DYING | SB_DEAD)
+static void super_wake(struct super_block *sb, unsigned int flag)
+{
+	WARN_ON_ONCE((flag & ~SUPER_WAKE_FLAGS));
+	WARN_ON_ONCE(hweight32(flag & SUPER_WAKE_FLAGS) > 1);
+
+	/*
+	 * Pairs with smp_load_acquire() in super_lock() to make sure
+	 * all initializations in the superblock are seen by the user
+	 * seeing SB_BORN sent.
+	 */
+	smp_store_release(&sb->s_flags, sb->s_flags | flag);
+	/*
+	 * Pairs with the barrier in prepare_to_wait_event() to make sure
+	 * ___wait_var_event() either sees SB_BORN set or
+	 * waitqueue_active() check in wake_up_var() sees the waiter.
+	 */
+	smp_mb();
+	wake_up_var(&sb->s_flags);
+}
+
+/*
+ * One thing we have to be careful of with a per-sb shrinker is that we don't
+ * drop the last active reference to the superblock from within the shrinker.
+ * If that happens we could trigger unregistering the shrinker from within the
+ * shrinker path and that leads to deadlock on the shrinker_mutex. Hence we
+ * take a passive reference to the superblock to avoid this from occurring.
+ */
+static unsigned long super_cache_scan(struct shrinker *shrink,
+				      struct shrink_control *sc)
+{
+	struct super_block *sb;
+	long	fs_objects = 0;
+	long	total_objects;
+	long	freed = 0;
+	long	dentries;
+	long	inodes;
+
+	sb = shrink->private_data;
+
+	/*
+	 * Deadlock avoidance.  We may hold various FS locks, and we don't want
+	 * to recurse into the FS that called us in clear_inode() and friends..
+	 */
+	if (!(sc->gfp_mask & __GFP_FS))
+		return SHRINK_STOP;
+
+	if (!super_trylock_shared(sb))
+		return SHRINK_STOP;
+
+	if (sb->s_op->nr_cached_objects)
+		fs_objects = sb->s_op->nr_cached_objects(sb, sc);
+
+	inodes = list_lru_shrink_count(&sb->s_inode_lru, sc);
+	dentries = list_lru_shrink_count(&sb->s_dentry_lru, sc);
+	total_objects = dentries + inodes + fs_objects;
+	if (!total_objects)
+		total_objects = 1;
+
+	/* proportion the scan between the caches */
+	dentries = mult_frac(sc->nr_to_scan, dentries, total_objects);
+	inodes = mult_frac(sc->nr_to_scan, inodes, total_objects);
+	fs_objects = mult_frac(sc->nr_to_scan, fs_objects, total_objects);
+
+	/*
+	 * prune the dcache first as the icache is pinned by it, then
+	 * prune the icache, followed by the filesystem specific caches
+	 *
+	 * Ensure that we always scan at least one object - memcg kmem
+	 * accounting uses this to fully empty the caches.
+	 */
+	sc->nr_to_scan = dentries + 1;
+	freed = prune_dcache_sb(sb, sc);
+	sc->nr_to_scan = inodes + 1;
+	freed += prune_icache_sb(sb, sc);
+
+	if (fs_objects) {
+		sc->nr_to_scan = fs_objects + 1;
+		freed += sb->s_op->free_cached_objects(sb, sc);
+	}
+
+	super_unlock_shared(sb);
+	return freed;
+}
+
+static unsigned long super_cache_count(struct shrinker *shrink,
+				       struct shrink_control *sc)
+{
+	struct super_block *sb;
+	long	total_objects = 0;
+
+	sb = shrink->private_data;
+
+	/*
+	 * We don't call super_trylock_shared() here as it is a scalability
+	 * bottleneck, so we're exposed to partial setup state. The shrinker
+	 * rwsem does not protect filesystem operations backing
+	 * list_lru_shrink_count() or s_op->nr_cached_objects(). Counts can
+	 * change between super_cache_count and super_cache_scan, so we really
+	 * don't need locks here.
+	 *
+	 * However, if we are currently mounting the superblock, the underlying
+	 * filesystem might be in a state of partial construction and hence it
+	 * is dangerous to access it.  super_trylock_shared() uses a SB_BORN check
+	 * to avoid this situation, so do the same here. The memory barrier is
+	 * matched with the one in mount_fs() as we don't hold locks here.
+	 */
+	if (!(sb->s_flags & SB_BORN))
+		return 0;
+	smp_rmb();
+
+	if (sb->s_op && sb->s_op->nr_cached_objects)
+		total_objects = sb->s_op->nr_cached_objects(sb, sc);
+
+	total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc);
+	total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc);
+
+	if (!total_objects)
+		return SHRINK_EMPTY;
+
+	total_objects = vfs_pressure_ratio(total_objects);
+	return total_objects;
+}
+
+static struct super_dev *super_dev_alloc(dev_t dev, struct super_block *sb);
+
+static void destroy_super_work(struct work_struct *work)
+{
+	struct super_block *s = container_of(work, struct super_block,
+							destroy_work);
+	fsnotify_sb_free(s);
+	security_sb_free(s);
+	put_user_ns(s->s_user_ns);
+	/* Only an unregistered entry is still owned by the superblock. */
+	kfree(s->s_super_dev);
+	kfree(s->s_subtype);
+	for (int i = 0; i < SB_FREEZE_LEVELS; i++)
+		percpu_free_rwsem(&s->s_writers.rw_sem[i]);
+	kfree(s);
+}
+
+static void destroy_super_rcu(struct rcu_head *head)
+{
+	struct super_block *s = container_of(head, struct super_block, rcu);
+	INIT_WORK(&s->destroy_work, destroy_super_work);
+	schedule_work(&s->destroy_work);
+}
+
+/* Free a superblock that has never been seen by anyone */
+static void destroy_unused_super(struct super_block *s)
+{
+	if (!s)
+		return;
+	super_unlock_excl(s);
+	list_lru_destroy(&s->s_dentry_lru);
+	list_lru_destroy(&s->s_inode_lru);
+	shrinker_free(s->s_shrink);
+	/* no delays needed */
+	destroy_super_work(&s->destroy_work);
+}
+
+/**
+ *	alloc_super	-	create new superblock
+ *	@type:	filesystem type superblock should belong to
+ *	@flags: the mount flags
+ *	@user_ns: User namespace for the super_block
+ *
+ *	Allocates and initializes a new &struct super_block.  alloc_super()
+ *	returns a pointer new superblock or %NULL if allocation had failed.
+ */
+static struct super_block *alloc_super(struct file_system_type *type, int flags,
+				       struct user_namespace *user_ns)
+{
+	struct super_block *s = kzalloc_obj(struct super_block);
+	static const struct super_operations default_op;
+	int i;
+
+	if (!s)
+		return NULL;
+
+	s->s_user_ns = get_user_ns(user_ns);
+	init_rwsem(&s->s_umount);
+	lockdep_set_class(&s->s_umount, &type->s_umount_key);
+	/*
+	 * sget_fc() can have s_umount recursion.
+	 *
+	 * When it cannot find a suitable sb, it allocates a new
+	 * one (this one), and tries again to find a suitable old
+	 * one.
+	 *
+	 * In case that succeeds, it will acquire the s_umount
+	 * lock of the old one. Since these are clearly distrinct
+	 * locks, and this object isn't exposed yet, there's no
+	 * risk of deadlocks.
+	 *
+	 * Annotate this by putting this lock in a different
+	 * subclass.
+	 */
+	down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
+
+	if (security_sb_alloc(s))
+		goto fail;
+
+	for (i = 0; i < SB_FREEZE_LEVELS; i++) {
+		if (__percpu_init_rwsem(&s->s_writers.rw_sem[i],
+					sb_writers_name[i],
+					&type->s_writers_key[i]))
+			goto fail;
+	}
+	s->s_bdi = &noop_backing_dev_info;
+	s->s_flags = flags;
+	if (s->s_user_ns != &init_user_ns)
+		s->s_iflags |= SB_I_NODEV;
+	INIT_HLIST_NODE(&s->s_instances);
+	INIT_HLIST_BL_HEAD(&s->s_roots);
+	spin_lock_init(&s->s_roots_lock);
+	mutex_init(&s->s_sync_lock);
+	INIT_LIST_HEAD(&s->s_inodes);
+	spin_lock_init(&s->s_inode_list_lock);
+	INIT_LIST_HEAD(&s->s_inodes_wb);
+	spin_lock_init(&s->s_inode_wblist_lock);
+	fserror_mount(s);
+
+	refcount_set(&s->s_passive, 1);
+	atomic_set(&s->s_active, 1);
+	mutex_init(&s->s_vfs_rename_mutex);
+	lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
+	init_rwsem(&s->s_dquot.dqio_sem);
+	s->s_maxbytes = MAX_NON_LFS;
+	s->s_op = &default_op;
+	s->s_time_gran = 1000000000;
+	s->s_time_min = TIME64_MIN;
+	s->s_time_max = TIME64_MAX;
+
+	s->s_shrink = shrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE,
+				     "sb-%s", type->name);
+	if (!s->s_shrink)
+		goto fail;
+
+	s->s_shrink->scan_objects = super_cache_scan;
+	s->s_shrink->count_objects = super_cache_count;
+	s->s_shrink->batch = 1024;
+	s->s_shrink->private_data = s;
+
+	if (list_lru_init_memcg(&s->s_dentry_lru, s->s_shrink))
+		goto fail;
+	if (list_lru_init_memcg(&s->s_inode_lru, s->s_shrink))
+		goto fail;
+	s->s_super_dev = super_dev_alloc(0, s);
+	if (!s->s_super_dev)
+		goto fail;
+
+	s->s_min_writeback_pages = MIN_WRITEBACK_PAGES;
+	return s;
+
+fail:
+	destroy_unused_super(s);
+	return NULL;
+}
+
+/* Superblock refcounting  */
+
+/*
+ * Drop a superblock's passive reference.  Must be called WITHOUT sb_lock held;
+ * put_super() acquires sb_lock itself when the final reference is dropped.
+ */
+void put_super(struct super_block *s)
+{
+	if (refcount_dec_and_test(&s->s_passive)) {
+
+		spin_lock(&sb_lock);
+		list_del_init(&s->s_list);
+		spin_unlock(&sb_lock);
+
+		WARN_ON(s->s_dentry_lru.node);
+		WARN_ON(s->s_inode_lru.node);
+		WARN_ON(s->s_mounts);
+		call_rcu(&s->rcu, destroy_super_rcu);
+	}
+}
+
+struct super_dev {
+	dev_t			sd_dev;
+	struct super_block	*sd_sb;
+	refcount_t		sd_ref;
+	struct rhlist_head	sd_node;
+	struct rcu_head		sd_rcu;
+};
+
+static struct rhltable super_dev_table;
+static const struct rhashtable_params super_dev_params = {
+	.key_len	= sizeof(dev_t),
+	.key_offset	= offsetof(struct super_dev, sd_dev),
+	.head_offset	= offsetof(struct super_dev, sd_node),
+};
+
+static struct super_dev *super_dev_alloc(dev_t dev, struct super_block *sb)
+{
+	struct super_dev *fsd;
+
+	fsd = kzalloc_obj(*fsd);
+	if (!fsd)
+		return NULL;
+	fsd->sd_dev = dev;
+	fsd->sd_sb = sb;
+	refcount_set(&fsd->sd_ref, 1);
+	return fsd;
+}
+
+static void super_dev_put(struct super_dev *fsd)
+{
+	/* Unlink only once unpinned, so a cursor never resumes from a removed node. */
+	if (fsd && refcount_dec_and_test(&fsd->sd_ref)) {
+		rhltable_remove(&super_dev_table, &fsd->sd_node, super_dev_params);
+		put_super(fsd->sd_sb);
+		kfree_rcu(fsd, sd_rcu);
+	}
+}
+
+void __init super_dev_init(void)
+{
+	if (rhltable_init(&super_dev_table, &super_dev_params))
+		panic("VFS: Cannot initialise super_dev_table\n");
+}
+
+static int super_dev_insert(struct super_dev *fsd)
+{
+	int err;
+
+	err = rhltable_insert(&super_dev_table, &fsd->sd_node, super_dev_params);
+	if (!err)
+		refcount_inc(&fsd->sd_sb->s_passive);
+	return err;
+}
+
+/* Register @sb under @sb->s_dev as the final fallible act of a set callback. */
+static int super_dev_register(struct super_block *sb)
+{
+	struct super_dev *fsd = sb->s_super_dev;
+	int err;
+
+	lockdep_assert_held(&sb_lock);
+	VFS_WARN_ON_ONCE(!sb->s_dev);
+	VFS_WARN_ON_ONCE(!fsd || fsd->sd_dev);
+
+	fsd->sd_dev = sb->s_dev;
+	err = super_dev_insert(fsd);
+	if (err)
+		fsd->sd_dev = 0;
+	return err;
+}
+
+static struct super_dev *super_dev_get(struct rhlist_head *pos)
+{
+	struct super_dev *sb_dev;
+
+	for (; pos; pos = rcu_dereference_all(pos->next)) {
+		sb_dev = container_of(pos, struct super_dev, sd_node);
+		if (refcount_inc_not_zero(&sb_dev->sd_ref))
+			return sb_dev;
+	}
+	return NULL;
+}
+
+static struct super_dev *super_dev_first(dev_t dev)
+{
+	struct super_dev *sb_dev;
+
+	rcu_read_lock();
+	sb_dev = super_dev_get(rhltable_lookup(&super_dev_table, &dev, super_dev_params));
+	rcu_read_unlock();
+	return sb_dev;
+}
+
+static struct super_dev *super_dev_next(struct super_dev *prev)
+{
+	struct super_dev *sb_dev;
+
+	rcu_read_lock();
+	sb_dev = super_dev_get(rcu_dereference_all(prev->sd_node.next));
+	rcu_read_unlock();
+
+	super_dev_put(prev);
+	return sb_dev;
+}
+
+static void kill_super_notify(struct super_block *sb)
+{
+	lockdep_assert_not_held(&sb->s_umount);
+
+	/* already notified earlier */
+	if (sb->s_flags & SB_DEAD)
+		return;
+
+	/*
+	 * Remove it from @fs_supers so it isn't found by new
+	 * sget_fc() walkers anymore. Any concurrent mounter still
+	 * managing to grab a temporary reference is guaranteed to
+	 * already see SB_DYING and will wait until we notify them about
+	 * SB_DEAD.
+	 */
+	spin_lock(&sb_lock);
+	hlist_del_init(&sb->s_instances);
+	spin_unlock(&sb_lock);
+
+	/* Drop sget_fc()'s claim; a never-registered entry stays with the sb. */
+	if (sb->s_super_dev->sd_dev) {
+		super_dev_put(sb->s_super_dev);
+		sb->s_super_dev = NULL;
+	}
+
+	/*
+	 * Let concurrent mounts know that this thing is really dead.
+	 * We don't need @sb->s_umount here as every concurrent caller
+	 * will see SB_DYING and either discard the superblock or wait
+	 * for SB_DEAD.
+	 */
+	super_wake(sb, SB_DEAD);
+}
+
+/**
+ *	deactivate_locked_super	-	drop an active reference to superblock
+ *	@s: superblock to deactivate
+ *
+ *	Drops an active reference to superblock, converting it into a temporary
+ *	one if there is no other active references left.  In that case we
+ *	tell fs driver to shut it down and drop the temporary reference we
+ *	had just acquired.
+ *
+ *	Caller holds exclusive lock on superblock; that lock is released.
+ */
+void deactivate_locked_super(struct super_block *s)
+{
+	struct file_system_type *fs = s->s_type;
+	if (atomic_dec_and_test(&s->s_active)) {
+		shrinker_free(s->s_shrink);
+		fs->kill_sb(s);
+
+		kill_super_notify(s);
+
+		/* list_lru_destroy() may sleep; put_super() callers may not. */
+		list_lru_destroy(&s->s_dentry_lru);
+		list_lru_destroy(&s->s_inode_lru);
+
+		put_filesystem(fs);
+		put_super(s);
+	} else {
+		super_unlock_excl(s);
+	}
+}
+
+EXPORT_SYMBOL(deactivate_locked_super);
+
+/**
+ *	deactivate_super	-	drop an active reference to superblock
+ *	@s: superblock to deactivate
+ *
+ *	Variant of deactivate_locked_super(), except that superblock is *not*
+ *	locked by caller.  If we are going to drop the final active reference,
+ *	lock will be acquired prior to that.
+ */
+void deactivate_super(struct super_block *s)
+{
+	if (!atomic_add_unless(&s->s_active, -1, 1)) {
+		__super_lock_excl(s);
+		deactivate_locked_super(s);
+	}
+}
+
+EXPORT_SYMBOL(deactivate_super);
+
+/**
+ * grab_super - acquire an active reference to a superblock
+ * @sb: superblock to acquire
+ *
+ * Acquire a temporary reference on a superblock and try to trade it for
+ * an active reference. This is used in sget_fc() to wait for a
+ * superblock to either become SB_BORN or for it to pass through
+ * sb->kill() and be marked as SB_DEAD.
+ *
+ * Return: This returns true if an active reference could be acquired,
+ *         false if not.
+ */
+static bool grab_super(struct super_block *sb)
+{
+	bool locked;
+
+	refcount_inc(&sb->s_passive);
+	spin_unlock(&sb_lock);
+	locked = super_lock_excl(sb);
+	if (locked) {
+		if (atomic_inc_not_zero(&sb->s_active)) {
+			put_super(sb);
+			return true;
+		}
+		super_unlock_excl(sb);
+	}
+	wait_var_event(&sb->s_flags, super_flags(sb, SB_DEAD));
+	put_super(sb);
+	return false;
+}
+
+/*
+ *	super_trylock_shared - try to grab ->s_umount shared
+ *	@sb: reference we are trying to grab
+ *
+ *	Try to prevent fs shutdown.  This is used in places where we
+ *	cannot take an active reference but we need to ensure that the
+ *	filesystem is not shut down while we are working on it. It returns
+ *	false if we cannot acquire s_umount or if we lose the race and
+ *	filesystem already got into shutdown, and returns true with the s_umount
+ *	lock held in read mode in case of success. On successful return,
+ *	the caller must drop the s_umount lock when done.
+ *
+ *	Note that unlike get_super() et.al. this one does *not* bump ->s_passive.
+ *	The reason why it's safe is that we are OK with doing trylock instead
+ *	of down_read().  There's a couple of places that are OK with that, but
+ *	it's very much not a general-purpose interface.
+ */
+bool super_trylock_shared(struct super_block *sb)
+{
+	if (down_read_trylock(&sb->s_umount)) {
+		if (!(sb->s_flags & SB_DYING) && sb->s_root &&
+		    (sb->s_flags & SB_BORN))
+			return true;
+		super_unlock_shared(sb);
+	}
+
+	return false;
+}
+
+/**
+ *	retire_super	-	prevents superblock from being reused
+ *	@sb: superblock to retire
+ *
+ *	The function marks superblock to be ignored in superblock test, which
+ *	prevents it from being reused for any new mounts.  If the superblock has
+ *	a private bdi, it also unregisters it, but doesn't reduce the refcount
+ *	of the superblock to prevent potential races.  The refcount is reduced
+ *	by generic_shutdown_super().  The function can not be called
+ *	concurrently with generic_shutdown_super().  It is safe to call the
+ *	function multiple times, subsequent calls have no effect.
+ *
+ *	The marker will affect the re-use only for block-device-based
+ *	superblocks.  Other superblocks will still get marked if this function
+ *	is used, but that will not affect their reusability.
+ */
+void retire_super(struct super_block *sb)
+{
+	WARN_ON(!sb->s_bdev);
+	__super_lock_excl(sb);
+	if (sb->s_iflags & SB_I_PERSB_BDI) {
+		bdi_unregister(sb->s_bdi);
+		sb->s_iflags &= ~SB_I_PERSB_BDI;
+	}
+	sb->s_iflags |= SB_I_RETIRED;
+	super_unlock_excl(sb);
+}
+EXPORT_SYMBOL(retire_super);
+
+/**
+ *	generic_shutdown_super	-	common helper for ->kill_sb()
+ *	@sb: superblock to kill
+ *
+ *	generic_shutdown_super() does all fs-independent work on superblock
+ *	shutdown.  Typical ->kill_sb() should pick all fs-specific objects
+ *	that need destruction out of superblock, call generic_shutdown_super()
+ *	and release aforementioned objects.  Note: dentries and inodes _are_
+ *	taken care of and do not need specific handling.
+ *
+ *	Upon calling this function, the filesystem may no longer alter or
+ *	rearrange the set of dentries belonging to this super_block, nor may it
+ *	change the attachments of dentries to inodes.
+ */
+void generic_shutdown_super(struct super_block *sb)
+{
+	const struct super_operations *sop = sb->s_op;
+
+	if (sb->s_root) {
+		fsnotify_sb_delete(sb);
+		shrink_dcache_for_umount(sb);
+		sync_filesystem(sb);
+		sb->s_flags &= ~SB_ACTIVE;
+
+		fserror_unmount(sb);
+		cgroup_writeback_umount(sb);
+
+		/* Evict all inodes with zero refcount. */
+		evict_inodes(sb);
+
+		/*
+		 * Clean up and evict any inodes that still have references due
+		 * to the security policy.
+		 */
+		security_sb_delete(sb);
+
+		if (sb->s_dio_done_wq) {
+			destroy_workqueue(sb->s_dio_done_wq);
+			sb->s_dio_done_wq = NULL;
+		}
+
+		if (sop->put_super)
+			sop->put_super(sb);
+
+		/*
+		 * Now that all potentially-encrypted inodes have been evicted,
+		 * the fscrypt keyring can be destroyed.
+		 */
+		fscrypt_destroy_keyring(sb);
+
+		if (CHECK_DATA_CORRUPTION(!list_empty(&sb->s_inodes), NULL,
+				"VFS: Busy inodes after unmount of %s (%s)",
+				sb->s_id, sb->s_type->name)) {
+			/*
+			 * Adding a proper bailout path here would be hard, but
+			 * we can at least make it more likely that a later
+			 * iput_final() or such crashes cleanly.
+			 */
+			struct inode *inode;
+
+			spin_lock(&sb->s_inode_list_lock);
+			list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+				inode->i_op = VFS_PTR_POISON;
+				inode->i_sb = VFS_PTR_POISON;
+				inode->i_mapping = VFS_PTR_POISON;
+			}
+			spin_unlock(&sb->s_inode_list_lock);
+		}
+	}
+	/*
+	 * Broadcast to everyone that grabbed a temporary reference to this
+	 * superblock before we removed it from @fs_supers that the superblock
+	 * is dying. Every walker of @fs_supers outside of sget_fc() will now
+	 * discard this superblock and treat it as dead.
+	 *
+	 * We leave the superblock on @fs_supers so it can be found by
+	 * sget_fc() until we passed sb->kill_sb().
+	 */
+	super_wake(sb, SB_DYING);
+	super_unlock_excl(sb);
+	if (sb->s_bdi != &noop_backing_dev_info) {
+		if (sb->s_iflags & SB_I_PERSB_BDI)
+			bdi_unregister(sb->s_bdi);
+		bdi_put(sb->s_bdi);
+		sb->s_bdi = &noop_backing_dev_info;
+	}
+}
+
+EXPORT_SYMBOL(generic_shutdown_super);
+
+bool mount_capable(struct fs_context *fc)
+{
+	if (!(fc->fs_type->fs_flags & FS_USERNS_MOUNT))
+		return capable(CAP_SYS_ADMIN);
+	else
+		return ns_capable(fc->user_ns, CAP_SYS_ADMIN);
+}
+
+/**
+ * sget_fc - Find or create a superblock
+ * @fc:	Filesystem context.
+ * @test: Comparison callback
+ * @set: Setup callback
+ *
+ * Create a new superblock or find an existing one.
+ *
+ * The @test callback is used to find a matching existing superblock.
+ * Whether or not the requested parameters in @fc are taken into account
+ * is specific to the @test callback that is used. They may even be
+ * completely ignored.
+ *
+ * If an extant superblock is matched, it will be returned unless:
+ *
+ * (1) the namespace the filesystem context @fc and the extant
+ *     superblock's namespace differ
+ *
+ * (2) the filesystem context @fc has requested that reusing an extant
+ *     superblock is not allowed
+ *
+ * In both cases EBUSY will be returned.
+ *
+ * If no match is made, a new superblock will be allocated and basic
+ * initialisation will be performed (s_type, s_fs_info and s_id will be
+ * set and the @set callback will be invoked), the superblock will be
+ * published and it will be returned in a partially constructed state
+ * with SB_BORN and SB_ACTIVE as yet unset.
+ *
+ * Return: On success, an extant or newly created superblock is
+ *         returned. On failure an error pointer is returned.
+ */
+struct super_block *sget_fc(struct fs_context *fc,
+			    int (*test)(struct super_block *, struct fs_context *),
+			    int (*set)(struct super_block *, struct fs_context *))
+{
+	struct super_block *s = NULL;
+	struct super_block *old;
+	struct user_namespace *user_ns = fc->global ? &init_user_ns : fc->user_ns;
+	int err;
+
+	/*
+	 * Never allow s_user_ns != &init_user_ns when FS_USERNS_MOUNT or
+	 * FS_USERNS_DELEGATABLE is not set, as the filesystem is likely
+	 * unprepared to handle it. This can happen when fsconfig() is called
+	 * from init_user_ns with an fs_fd opened in another user namespace.
+	 */
+	if (user_ns != &init_user_ns &&
+	    !(fc->fs_type->fs_flags & (FS_USERNS_MOUNT | FS_USERNS_DELEGATABLE))) {
+		errorfc(fc, "VFS: Mounting from non-initial user namespace is not allowed");
+		return ERR_PTR(-EPERM);
+	}
+
+retry:
+	spin_lock(&sb_lock);
+	if (test) {
+		hlist_for_each_entry(old, &fc->fs_type->fs_supers, s_instances) {
+			if (test(old, fc))
+				goto share_extant_sb;
+		}
+	}
+	if (!s) {
+		spin_unlock(&sb_lock);
+
+		s = alloc_super(fc->fs_type, fc->sb_flags, user_ns);
+		if (!s)
+			return ERR_PTR(-ENOMEM);
+		goto retry;
+	}
+
+	s->s_fs_info = fc->s_fs_info;
+	err = set(s, fc);
+	if (err) {
+		VFS_WARN_ON_ONCE(s->s_super_dev->sd_dev);
+		s->s_fs_info = NULL;
+		spin_unlock(&sb_lock);
+		destroy_unused_super(s);
+		return ERR_PTR(err);
+	}
+	VFS_WARN_ON_ONCE(!s->s_super_dev->sd_dev);
+	fc->s_fs_info = NULL;
+	s->s_type = fc->fs_type;
+	s->s_iflags |= fc->s_iflags;
+	strscpy(s->s_id, s->s_type->name, sizeof(s->s_id));
+	/*
+	 * Make the superblock visible on @super_blocks and @fs_supers.
+	 * It's in a nascent state and users should wait on SB_BORN or
+	 * SB_DYING to be set.
+	 */
+	list_add_tail(&s->s_list, &super_blocks);
+	hlist_add_head(&s->s_instances, &s->s_type->fs_supers);
+	spin_unlock(&sb_lock);
+	get_filesystem(s->s_type);
+	shrinker_register(s->s_shrink);
+	return s;
+
+share_extant_sb:
+	if (user_ns != old->s_user_ns || fc->exclusive) {
+		spin_unlock(&sb_lock);
+		destroy_unused_super(s);
+		if (fc->exclusive)
+			warnfc(fc, "reusing existing filesystem not allowed");
+		else
+			warnfc(fc, "reusing existing filesystem in another namespace not allowed");
+		return ERR_PTR(-EBUSY);
+	}
+	if (!grab_super(old))
+		goto retry;
+	destroy_unused_super(s);
+	return old;
+}
+EXPORT_SYMBOL(sget_fc);
+
+void drop_super(struct super_block *sb)
+{
+	super_unlock_shared(sb);
+	put_super(sb);
+}
+
+EXPORT_SYMBOL(drop_super);
+
+void drop_super_exclusive(struct super_block *sb)
+{
+	super_unlock_excl(sb);
+	put_super(sb);
+}
+
+enum super_iter_flags_t {
+	SUPER_ITER_EXCL		= (1U << 0),
+	SUPER_ITER_UNLOCKED	= (1U << 1),
+	SUPER_ITER_REVERSE	= (1U << 2),
+};
+
+static inline struct super_block *first_super(enum super_iter_flags_t flags)
+{
+	if (flags & SUPER_ITER_REVERSE)
+		return list_last_entry(&super_blocks, struct super_block, s_list);
+	return list_first_entry(&super_blocks, struct super_block, s_list);
+}
+
+static inline struct super_block *next_super(struct super_block *sb,
+					     enum super_iter_flags_t flags)
+{
+	if (flags & SUPER_ITER_REVERSE)
+		return list_prev_entry(sb, s_list);
+	return list_next_entry(sb, s_list);
+}
+
+static void __iterate_supers(void (*f)(struct super_block *, void *), void *arg,
+			     enum super_iter_flags_t flags)
+{
+	struct super_block *sb, *p = NULL;
+	bool excl = flags & SUPER_ITER_EXCL;
+
+	spin_lock(&sb_lock);
+
+	for (sb = first_super(flags);
+	     !list_entry_is_head(sb, &super_blocks, s_list);
+	     sb = next_super(sb, flags)) {
+		if (super_flags(sb, SB_DYING))
+			continue;
+
+		if (!refcount_inc_not_zero(&sb->s_passive))
+			continue;
+
+		spin_unlock(&sb_lock);
+
+		if (flags & SUPER_ITER_UNLOCKED) {
+			f(sb, arg);
+		} else if (super_lock(sb, excl)) {
+			f(sb, arg);
+			super_unlock(sb, excl);
+		}
+
+		if (p)
+			put_super(p);
+		p = sb;
+		spin_lock(&sb_lock);
+	}
+	spin_unlock(&sb_lock);
+	if (p)
+		put_super(p);
+}
+
+void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
+{
+	__iterate_supers(f, arg, 0);
+}
+
+/**
+ *	iterate_supers_type - call function for superblocks of given type
+ *	@type: fs type
+ *	@f: function to call
+ *	@arg: argument to pass to it
+ *
+ *	Scans the superblock list and calls given function, passing it
+ *	locked superblock and given argument.
+ */
+void iterate_supers_type(struct file_system_type *type,
+	void (*f)(struct super_block *, void *), void *arg)
+{
+	struct super_block *sb, *p = NULL;
+
+	spin_lock(&sb_lock);
+	hlist_for_each_entry(sb, &type->fs_supers, s_instances) {
+		bool locked;
+
+		if (super_flags(sb, SB_DYING))
+			continue;
+
+		if (!refcount_inc_not_zero(&sb->s_passive))
+			continue;
+
+		spin_unlock(&sb_lock);
+
+		locked = super_lock_shared(sb);
+		if (locked) {
+			f(sb, arg);
+			super_unlock_shared(sb);
+		}
+
+		if (p)
+			put_super(p);
+		p = sb;
+		spin_lock(&sb_lock);
+	}
+	spin_unlock(&sb_lock);
+	if (p)
+		put_super(p);
+}
+
+EXPORT_SYMBOL(iterate_supers_type);
+
+struct super_block *user_get_super(dev_t dev, bool excl)
+{
+	struct super_dev *sb_dev;
+
+	for (sb_dev = super_dev_first(dev); sb_dev; sb_dev = super_dev_next(sb_dev)) {
+		struct super_block *sb = sb_dev->sd_sb;
+
+		if (!super_lock(sb, excl))
+			continue;
+
+		/* The pinned entry holds a passive reference, take our own. */
+		refcount_inc(&sb->s_passive);
+		super_dev_put(sb_dev);
+		return sb;
+	}
+	return NULL;
+}
+
+/**
+ * reconfigure_super - asks filesystem to change superblock parameters
+ * @fc: The superblock and configuration
+ *
+ * Alters the configuration parameters of a live superblock.
+ */
+int reconfigure_super(struct fs_context *fc)
+{
+	struct super_block *sb = fc->root->d_sb;
+	int retval;
+	bool remount_ro = false;
+	bool remount_rw = false;
+	bool force = fc->sb_flags & SB_FORCE;
+
+	if (fc->sb_flags_mask & ~MS_RMT_MASK)
+		return -EINVAL;
+	if (sb->s_writers.frozen != SB_UNFROZEN)
+		return -EBUSY;
+
+	retval = security_sb_remount(sb, fc->security);
+	if (retval)
+		return retval;
+
+	if (fc->sb_flags_mask & SB_RDONLY) {
+#ifdef CONFIG_BLOCK
+		if (!(fc->sb_flags & SB_RDONLY) && sb->s_bdev &&
+		    bdev_read_only(sb->s_bdev))
+			return -EACCES;
+#endif
+		remount_rw = !(fc->sb_flags & SB_RDONLY) && sb_rdonly(sb);
+		remount_ro = (fc->sb_flags & SB_RDONLY) && !sb_rdonly(sb);
+	}
+
+	if (remount_ro) {
+		if (!hlist_empty(&sb->s_pins)) {
+			super_unlock_excl(sb);
+			group_pin_kill(&sb->s_pins);
+			__super_lock_excl(sb);
+			if (!sb->s_root)
+				return 0;
+			if (sb->s_writers.frozen != SB_UNFROZEN)
+				return -EBUSY;
+			remount_ro = !sb_rdonly(sb);
+		}
+	}
+	shrink_dcache_sb(sb);
+
+	/* If we are reconfiguring to RDONLY and current sb is read/write,
+	 * make sure there are no files open for writing.
+	 */
+	if (remount_ro) {
+		if (force) {
+			sb_start_ro_state_change(sb);
+		} else {
+			retval = sb_prepare_remount_readonly(sb);
+			if (retval)
+				return retval;
+		}
+	} else if (remount_rw) {
+		/*
+		 * Protect filesystem's reconfigure code from writes from
+		 * userspace until reconfigure finishes.
+		 */
+		sb_start_ro_state_change(sb);
+	}
+
+	if (fc->ops->reconfigure) {
+		retval = fc->ops->reconfigure(fc);
+		if (retval) {
+			if (!force)
+				goto cancel_readonly;
+			/* If forced remount, go ahead despite any errors */
+			WARN(1, "forced remount of a %s fs returned %i\n",
+			     sb->s_type->name, retval);
+		}
+	}
+
+	WRITE_ONCE(sb->s_flags, ((sb->s_flags & ~fc->sb_flags_mask) |
+				 (fc->sb_flags & fc->sb_flags_mask)));
+	sb_end_ro_state_change(sb);
+
+	/*
+	 * Some filesystems modify their metadata via some other path than the
+	 * bdev buffer cache (eg. use a private mapping, or directories in
+	 * pagecache, etc). Also file data modifications go via their own
+	 * mappings. So If we try to mount readonly then copy the filesystem
+	 * from bdev, we could get stale data, so invalidate it to give a best
+	 * effort at coherency.
+	 */
+	if (remount_ro && sb->s_bdev)
+		invalidate_bdev(sb->s_bdev);
+	return 0;
+
+cancel_readonly:
+	sb_end_ro_state_change(sb);
+	return retval;
+}
+
+static void do_emergency_remount_callback(struct super_block *sb, void *unused)
+{
+	if (sb->s_bdev && !sb_rdonly(sb)) {
+		struct fs_context *fc;
+
+		fc = fs_context_for_reconfigure(sb->s_root,
+					SB_RDONLY | SB_FORCE, SB_RDONLY);
+		if (!IS_ERR(fc)) {
+			if (parse_monolithic_mount_data(fc, NULL) == 0)
+				(void)reconfigure_super(fc);
+			put_fs_context(fc);
+		}
+	}
+}
+
+static void do_emergency_remount(struct work_struct *work)
+{
+	__iterate_supers(do_emergency_remount_callback, NULL,
+			 SUPER_ITER_EXCL | SUPER_ITER_REVERSE);
+	kfree(work);
+	printk("Emergency Remount complete\n");
+}
+
+void emergency_remount(void)
+{
+	struct work_struct *work;
+
+	work = kmalloc_obj(*work, GFP_ATOMIC);
+	if (work) {
+		INIT_WORK(work, do_emergency_remount);
+		schedule_work(work);
+	}
+}
+
+static inline bool get_active_super(struct super_block *sb)
+{
+	bool active = false;
+
+	if (super_lock_excl(sb)) {
+		active = atomic_inc_not_zero(&sb->s_active);
+		super_unlock_excl(sb);
+	}
+	return active;
+}
+
+static void do_thaw_all_callback(struct super_block *sb, void *unused)
+{
+	if (!get_active_super(sb))
+		return;
+
+	/* fs_bdev_thaw() acquires s_umount so it must not be held here */
+	if (IS_ENABLED(CONFIG_BLOCK))
+		while (sb->s_bdev && !bdev_thaw(sb->s_bdev))
+			pr_warn("Emergency Thaw on %pg\n", sb->s_bdev);
+
+	if (super_lock_excl(sb))
+		thaw_super_locked(sb, FREEZE_HOLDER_USERSPACE, NULL);
+	deactivate_super(sb);
+}
+
+static void do_thaw_all(struct work_struct *work)
+{
+	__iterate_supers(do_thaw_all_callback, NULL, SUPER_ITER_UNLOCKED);
+	kfree(work);
+	printk(KERN_WARNING "Emergency Thaw complete\n");
+}
+
+/**
+ * emergency_thaw_all -- forcibly thaw every frozen filesystem
+ *
+ * Used for emergency unfreeze of all filesystems via SysRq
+ */
+void emergency_thaw_all(void)
+{
+	struct work_struct *work;
+
+	work = kmalloc_obj(*work, GFP_ATOMIC);
+	if (work) {
+		INIT_WORK(work, do_thaw_all);
+		schedule_work(work);
+	}
+}
+
+static const char *filesystems_freeze_ptr = "filesystems_freeze";
+
+static void filesystems_freeze_callback(struct super_block *sb, void *freeze_all_ptr)
+{
+	if (!sb->s_op->freeze_fs && !sb->s_op->freeze_super)
+		return;
+
+	if (!freeze_all_ptr && !(sb->s_type->fs_flags & FS_POWER_FREEZE))
+		return;
+
+	if (!get_active_super(sb))
+		return;
+
+	if (sb->s_op->freeze_super)
+		sb->s_op->freeze_super(sb, FREEZE_EXCL | FREEZE_HOLDER_KERNEL,
+				       filesystems_freeze_ptr);
+	else
+		freeze_super(sb, FREEZE_EXCL | FREEZE_HOLDER_KERNEL,
+			     filesystems_freeze_ptr);
+
+	deactivate_super(sb);
+}
+
+void filesystems_freeze(bool freeze_all)
+{
+	void *freeze_all_ptr = NULL;
+
+	if (freeze_all)
+		freeze_all_ptr = &freeze_all;
+	__iterate_supers(filesystems_freeze_callback, freeze_all_ptr,
+			 SUPER_ITER_UNLOCKED | SUPER_ITER_REVERSE);
+}
+
+static void filesystems_thaw_callback(struct super_block *sb, void *unused)
+{
+	if (!sb->s_op->freeze_fs && !sb->s_op->freeze_super)
+		return;
+
+	if (!get_active_super(sb))
+		return;
+
+	if (sb->s_op->thaw_super)
+		sb->s_op->thaw_super(sb, FREEZE_EXCL | FREEZE_HOLDER_KERNEL,
+				     filesystems_freeze_ptr);
+	else
+		thaw_super(sb, FREEZE_EXCL | FREEZE_HOLDER_KERNEL,
+			   filesystems_freeze_ptr);
+
+	deactivate_super(sb);
+}
+
+void filesystems_thaw(void)
+{
+	__iterate_supers(filesystems_thaw_callback, NULL, SUPER_ITER_UNLOCKED);
+}
+
+static DEFINE_IDA(unnamed_dev_ida);
+
+/**
+ * get_anon_bdev - Allocate a block device for filesystems which don't have one.
+ * @p: Pointer to a dev_t.
+ *
+ * Filesystems which don't use real block devices can call this function
+ * to allocate a virtual block device.
+ *
+ * Context: Any context.  Frequently called while holding sb_lock.
+ * Return: 0 on success, -EMFILE if there are no anonymous bdevs left
+ * or -ENOMEM if memory allocation failed.
+ */
+int get_anon_bdev(dev_t *p)
+{
+	int dev;
+
+	/*
+	 * Many userspace utilities consider an FSID of 0 invalid.
+	 * Always return at least 1 from get_anon_bdev.
+	 */
+	dev = ida_alloc_range(&unnamed_dev_ida, 1, (1 << MINORBITS) - 1,
+			GFP_ATOMIC);
+	if (dev == -ENOSPC)
+		dev = -EMFILE;
+	if (dev < 0)
+		return dev;
+
+	*p = MKDEV(0, dev);
+	return 0;
+}
+EXPORT_SYMBOL(get_anon_bdev);
+
+void free_anon_bdev(dev_t dev)
+{
+	ida_free(&unnamed_dev_ida, MINOR(dev));
+}
+EXPORT_SYMBOL(free_anon_bdev);
+
+int set_anon_super(struct super_block *s, void *data)
+{
+	int error;
+
+	error = get_anon_bdev(&s->s_dev);
+	if (error)
+		return error;
+
+	error = super_dev_register(s);
+	if (error)
+		free_anon_bdev(s->s_dev);
+	return error;
+}
+EXPORT_SYMBOL(set_anon_super);
+
+void kill_anon_super(struct super_block *sb)
+{
+	dev_t dev = sb->s_dev;
+	generic_shutdown_super(sb);
+	kill_super_notify(sb);
+	free_anon_bdev(dev);
+}
+EXPORT_SYMBOL(kill_anon_super);
+
+int set_anon_super_fc(struct super_block *sb, struct fs_context *fc)
+{
+	return set_anon_super(sb, NULL);
+}
+EXPORT_SYMBOL(set_anon_super_fc);
+
+static int test_keyed_super(struct super_block *sb, struct fs_context *fc)
+{
+	return sb->s_fs_info == fc->s_fs_info;
+}
+
+static int test_single_super(struct super_block *s, struct fs_context *fc)
+{
+	return 1;
+}
+
+static int vfs_get_super(struct fs_context *fc,
+		int (*test)(struct super_block *, struct fs_context *),
+		int (*fill_super)(struct super_block *sb,
+				  struct fs_context *fc))
+{
+	struct super_block *sb;
+	int err;
+
+	sb = sget_fc(fc, test, set_anon_super_fc);
+	if (IS_ERR(sb))
+		return PTR_ERR(sb);
+
+	if (!sb->s_root) {
+		err = fill_super(sb, fc);
+		if (err)
+			goto error;
+
+		sb->s_flags |= SB_ACTIVE;
+	}
+
+	fc->root = dget(sb->s_root);
+	return 0;
+
+error:
+	deactivate_locked_super(sb);
+	return err;
+}
+
+int get_tree_nodev(struct fs_context *fc,
+		  int (*fill_super)(struct super_block *sb,
+				    struct fs_context *fc))
+{
+	return vfs_get_super(fc, NULL, fill_super);
+}
+EXPORT_SYMBOL(get_tree_nodev);
+
+int get_tree_single(struct fs_context *fc,
+		  int (*fill_super)(struct super_block *sb,
+				    struct fs_context *fc))
+{
+	return vfs_get_super(fc, test_single_super, fill_super);
+}
+EXPORT_SYMBOL(get_tree_single);
+
+int get_tree_keyed(struct fs_context *fc,
+		  int (*fill_super)(struct super_block *sb,
+				    struct fs_context *fc),
+		void *key)
+{
+	fc->s_fs_info = key;
+	return vfs_get_super(fc, test_keyed_super, fill_super);
+}
+EXPORT_SYMBOL(get_tree_keyed);
+
+static int set_bdev_super(struct super_block *s, void *data)
+{
+	s->s_dev = *(dev_t *)data;
+	return super_dev_register(s);
+}
+
+static int super_s_dev_set(struct super_block *s, struct fs_context *fc)
+{
+	return set_bdev_super(s, fc->sget_key);
+}
+
+static int super_s_dev_test(struct super_block *s, struct fs_context *fc)
+{
+	return !(s->s_iflags & SB_I_RETIRED) &&
+		s->s_dev == *(dev_t *)fc->sget_key;
+}
+
+/**
+ * sget_dev - Find or create a superblock by device number
+ * @fc: Filesystem context.
+ * @dev: device number
+ *
+ * Find or create a superblock using the provided device number that
+ * will be stored in fc->sget_key.
+ *
+ * If an extant superblock is matched, then that will be returned with
+ * an elevated reference count that the caller must transfer or discard.
+ *
+ * If no match is made, a new superblock will be allocated and basic
+ * initialisation will be performed (s_type, s_fs_info, s_id, s_dev will
+ * be set). The superblock will be published and it will be returned in
+ * a partially constructed state with SB_BORN and SB_ACTIVE as yet
+ * unset.
+ *
+ * Return: an existing or newly created superblock on success, an error
+ *         pointer on failure.
+ */
+struct super_block *sget_dev(struct fs_context *fc, dev_t dev)
+{
+	fc->sget_key = &dev;
+	return sget_fc(fc, super_s_dev_test, super_s_dev_set);
+}
+EXPORT_SYMBOL(sget_dev);
+
+#ifdef CONFIG_BLOCK
+static int fs_super_freeze(struct super_block *sb)
+{
+	if (sb->s_op->freeze_super)
+		return sb->s_op->freeze_super(sb,
+				FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE, NULL);
+	return freeze_super(sb, FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE, NULL);
+}
+
+static int fs_super_thaw(struct super_block *sb)
+{
+	if (sb->s_op->thaw_super)
+		return sb->s_op->thaw_super(sb,
+				FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE, NULL);
+	return thaw_super(sb, FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE, NULL);
+}
+
+static void fs_bdev_mark_dead(struct block_device *bdev, bool surprise)
+{
+	struct super_dev *sb_dev;
+	dev_t dev = bdev->bd_dev;
+
+	mutex_unlock(&bdev->bd_holder_lock);
+
+	for (sb_dev = super_dev_first(dev); sb_dev; sb_dev = super_dev_next(sb_dev)) {
+		struct super_block *sb = sb_dev->sd_sb;
+
+		if (!super_lock_shared(sb))
+			continue;
+		if (sb->s_root && (sb->s_flags & SB_ACTIVE)) {
+			if (!sb->s_op->remove_bdev ||
+			    sb->s_op->remove_bdev(sb, bdev)) {
+				if (!surprise)
+					sync_filesystem(sb);
+				shrink_dcache_sb(sb);
+				evict_inodes(sb);
+				if (sb->s_op->shutdown)
+					sb->s_op->shutdown(sb);
+			}
+		}
+		super_unlock_shared(sb);
+	}
+}
+
+static void fs_bdev_sync(struct block_device *bdev)
+{
+	struct super_dev *sb_dev;
+	dev_t dev = bdev->bd_dev;
+
+	mutex_unlock(&bdev->bd_holder_lock);
+
+	for (sb_dev = super_dev_first(dev); sb_dev; sb_dev = super_dev_next(sb_dev)) {
+		struct super_block *sb = sb_dev->sd_sb;
+
+		if (!super_lock_shared(sb))
+			continue;
+		if (sb->s_root && (sb->s_flags & SB_ACTIVE))
+			sync_filesystem(sb);
+		super_unlock_shared(sb);
+	}
+}
+
+/**
+ * fs_bdev_freeze - freeze every superblock using a block device
+ * @bdev: block device
+ *
+ * Freeze each live superblock using @bdev.  A superblock owning several block
+ * devices is frozen once per device and stays frozen until all are thawed; the
+ * block layer nests these freezes so the count stays balanced.
+ *
+ * Return: 0, or the error from the one superblock on a single-fs device.  When
+ *         several superblocks share @bdev a per-superblock failure is swallowed
+ *         (see below), but a sync_blockdev() failure is always reported.
+ */
+static int fs_bdev_freeze(struct block_device *bdev)
+{
+	dev_t dev = bdev->bd_dev;
+	struct super_dev *sb_dev;
+	unsigned int count = 0;
+	int error = 0, err;
+
+	lockdep_assert_held(&bdev->bd_fsfreeze_mutex);
+
+	mutex_unlock(&bdev->bd_holder_lock);
+
+	for (sb_dev = super_dev_first(dev); sb_dev; sb_dev = super_dev_next(sb_dev)) {
+		if (!get_active_super(sb_dev->sd_sb))
+			continue;
+		err = fs_super_freeze(sb_dev->sd_sb);
+		if (err && !error)
+			error = err;
+		deactivate_super(sb_dev->sd_sb);
+		count++;
+	}
+
+	/*
+	 * When several superblocks share the device, keep it frozen even if some
+	 * of them failed to freeze and swallow the error: rolling the rest back
+	 * via thaw_super() can fail too, so neither is a clear win. A single
+	 * filesystem (count == 1) still reports its error.
+	 */
+	if (error && count > 1)
+		error = 0;
+	if (!error)
+		error = sync_blockdev(bdev);
+	return error;
+}
+
+/**
+ * fs_bdev_thaw - thaw every superblock using a block device
+ * @bdev: block device
+ *
+ * The counterpart to fs_bdev_freeze(): thaw each live superblock using @bdev.
+ * A zero return does not imply a superblock is fully unfrozen; it may have been
+ * frozen more than once (by the kernel or via another device).
+ *
+ * Return: 0, or the first error on a single-fs device; a shared device swallows
+ *         per-superblock errors, as fs_bdev_freeze() does.
+ */
+static int fs_bdev_thaw(struct block_device *bdev)
+{
+	dev_t dev = bdev->bd_dev;
+	struct super_dev *sb_dev;
+	unsigned int count = 0;
+	int error = 0, err;
+
+	lockdep_assert_held(&bdev->bd_fsfreeze_mutex);
+
+	mutex_unlock(&bdev->bd_holder_lock);
+
+	for (sb_dev = super_dev_first(dev); sb_dev; sb_dev = super_dev_next(sb_dev)) {
+		if (!get_active_super(sb_dev->sd_sb))
+			continue;
+		err = fs_super_thaw(sb_dev->sd_sb);
+		if (err && !error)
+			error = err;
+		deactivate_super(sb_dev->sd_sb);
+		count++;
+	}
+
+	/* Shared device: swallow per-superblock errors, like fs_bdev_freeze(). */
+	if (error && count > 1)
+		error = 0;
+	return error;
+}
+
+static const struct blk_holder_ops fs_holder_ops = {
+	.mark_dead		= fs_bdev_mark_dead,
+	.sync			= fs_bdev_sync,
+	.freeze			= fs_bdev_freeze,
+	.thaw			= fs_bdev_thaw,
+};
+
+static struct super_dev *super_dev_lookup(dev_t dev, struct super_block *sb)
+{
+	struct super_dev *it;
+	struct rhlist_head *list, *pos;
+
+	RCU_LOCKDEP_WARN(!rcu_read_lock_held(), "suspicious super_dev_lookup() usage");
+	VFS_WARN_ON_ONCE(!dev);
+	VFS_WARN_ON_ONCE(!sb);
+
+	list = rhltable_lookup(&super_dev_table, &dev, super_dev_params);
+	rhl_for_each_entry_rcu(it, pos, list, sd_node) {
+		if (it->sd_sb == sb)
+			return it;
+	}
+
+	return NULL;
+}
+
+static int fs_bdev_register(struct file *bdev_file, struct super_block *sb)
+{
+	struct super_dev *sb_dev __free(kfree) = NULL;
+	dev_t dev = file_bdev(bdev_file)->bd_dev;
+	int err;
+
+	scoped_guard(rcu) {
+		sb_dev = super_dev_lookup(dev, sb);
+		if (sb_dev && refcount_inc_not_zero(&sb_dev->sd_ref)) {
+			retain_and_null_ptr(sb_dev);
+			return 0;
+		}
+	}
+
+	sb_dev = super_dev_alloc(dev, sb);
+	if (!sb_dev)
+		return -ENOMEM;
+
+	err = super_dev_insert(sb_dev);
+	if (err)
+		return err;
+
+	/* Publish the entry before reading the count; pairs with bdev_freeze(). */
+	smp_mb();
+	if (atomic_read(&file_bdev(bdev_file)->bd_fsfreeze_count) > 0) {
+		err = -EBUSY;
+		super_dev_put(sb_dev);
+	}
+
+	retain_and_null_ptr(sb_dev);
+	return err;
+}
+
+/**
+ * fs_bdev_file_open_by_dev - claim a block device on behalf of a superblock
+ * @dev: block device number
+ * @mode: open mode
+ * @holder: block-layer exclusivity token (a superblock, or the file_system_type
+ *          when the device may be shared by several superblocks of that type)
+ * @sb: superblock to drive fs_holder_ops events for
+ *
+ * Open @dev with &fs_holder_ops and register that @sb uses it, so device
+ * removal/sync/freeze/thaw are propagated to @sb (and any other superblock
+ * sharing @dev).  Must be paired with fs_bdev_file_release().
+ *
+ * Return: an opened block-device file or an ERR_PTR().
+ */
+struct file *fs_bdev_file_open_by_dev(dev_t dev, blk_mode_t mode, void *holder,
+				      struct super_block *sb)
+{
+	struct file *bdev_file;
+	int err;
+
+	bdev_file = bdev_file_open_by_dev(dev, mode, holder, &fs_holder_ops);
+	if (IS_ERR(bdev_file))
+		return bdev_file;
+
+	err = fs_bdev_register(bdev_file, sb);
+	if (err) {
+		bdev_fput(bdev_file);
+		return ERR_PTR(err);
+	}
+	return bdev_file;
+}
+EXPORT_SYMBOL_GPL(fs_bdev_file_open_by_dev);
+
+/**
+ * fs_bdev_file_open_by_path - claim a block device on behalf of a superblock
+ * @path: path to the block device
+ * @mode: open mode
+ * @holder: block-layer exclusivity token (a superblock, or the file_system_type
+ *          when the device may be shared by several superblocks of that type)
+ * @sb: superblock to drive fs_holder_ops events for
+ *
+ * Open the block device at @path with &fs_holder_ops and register that @sb
+ * uses it, so device removal/sync/freeze/thaw are propagated to @sb (and any
+ * other superblock sharing the device).  Must be paired with
+ * fs_bdev_file_release().
+ *
+ * Return: an opened block-device file or an ERR_PTR().
+ */
+struct file *fs_bdev_file_open_by_path(const char *path, blk_mode_t mode,
+				       void *holder, struct super_block *sb)
+{
+	struct file *bdev_file;
+	int err;
+
+	bdev_file = bdev_file_open_by_path(path, mode, holder, &fs_holder_ops);
+	if (IS_ERR(bdev_file))
+		return bdev_file;
+
+	err = fs_bdev_register(bdev_file, sb);
+	if (err) {
+		bdev_fput(bdev_file);
+		return ERR_PTR(err);
+	}
+	return bdev_file;
+}
+EXPORT_SYMBOL_GPL(fs_bdev_file_open_by_path);
+
+/**
+ * fs_bdev_unregister - drop a superblock's claim on a block device
+ * @bdev_file: file returned by fs_bdev_file_open_by_{dev,path}()
+ * @sb: superblock the device was claimed for
+ *
+ * The inverse of fs_bdev_register(): drop one claim on the {dev, @sb} entry
+ * (the last claim unregisters it; a pinning cursor defers the actual unlink)
+ * without closing the device.  A caller that must act on the still-open device
+ * between unregistering and closing - e.g. re-allow freezing one denied for a
+ * membership change - pairs this with bdev_fput().  fs_bdev_file_release() is
+ * the common unregister-and-close.
+ */
+void fs_bdev_unregister(struct file *bdev_file, struct super_block *sb)
+{
+	dev_t dev = file_bdev(bdev_file)->bd_dev;
+	struct super_dev *sb_dev;
+
+	rcu_read_lock();
+	sb_dev = super_dev_lookup(dev, sb);
+	rcu_read_unlock();
+	super_dev_put(sb_dev);
+}
+EXPORT_SYMBOL_GPL(fs_bdev_unregister);
+
+/**
+ * fs_bdev_file_release - release a block device claimed for a superblock
+ * @bdev_file: file returned by fs_bdev_file_open_by_{dev,path}()
+ * @sb: superblock the device was claimed for
+ *
+ * Unregister the {dev, @sb} entry, then close the block device.
+ */
+void fs_bdev_file_release(struct file *bdev_file, struct super_block *sb)
+{
+	fs_bdev_unregister(bdev_file, sb);
+	bdev_fput(bdev_file);
+}
+EXPORT_SYMBOL_GPL(fs_bdev_file_release);
+
+int setup_bdev_super(struct super_block *sb, int sb_flags,
+		struct fs_context *fc)
+{
+	blk_mode_t mode = sb_open_mode(sb_flags);
+	struct file *bdev_file;
+	struct block_device *bdev;
+
+	bdev_file = fs_bdev_file_open_by_dev(sb->s_dev, mode, sb, sb);
+	if (IS_ERR(bdev_file)) {
+		if (fc)
+			errorf(fc, "%s: Can't open blockdev", fc->source);
+		return PTR_ERR(bdev_file);
+	}
+	bdev = file_bdev(bdev_file);
+
+	/*
+	 * This really should be in blkdev_get_by_dev, but right now can't due
+	 * to legacy issues that require us to allow opening a block device node
+	 * writable from userspace even for a read-only block device.
+	 */
+	if ((mode & BLK_OPEN_WRITE) && bdev_read_only(bdev)) {
+		fs_bdev_file_release(bdev_file, sb);
+		return -EACCES;
+	}
+
+	/* The sget_fc() entry is already published; pairs with bdev_freeze(). */
+	smp_mb();
+	if (atomic_read(&bdev->bd_fsfreeze_count) > 0) {
+		if (fc)
+			warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);
+		fs_bdev_file_release(bdev_file, sb);
+		return -EBUSY;
+	}
+
+	spin_lock(&sb_lock);
+	sb->s_bdev_file = bdev_file;
+	sb->s_bdev = bdev;
+	sb->s_bdi = bdi_get(bdev->bd_disk->bdi);
+	if (bdev_stable_writes(bdev))
+		sb->s_iflags |= SB_I_STABLE_WRITES;
+	spin_unlock(&sb_lock);
+
+	snprintf(sb->s_id, sizeof(sb->s_id), "%pg", bdev);
+	shrinker_debugfs_rename(sb->s_shrink, "sb-%s:%s", sb->s_type->name,
+				sb->s_id);
+	sb_set_blocksize(sb, block_size(bdev));
+	return 0;
+}
+EXPORT_SYMBOL_GPL(setup_bdev_super);
+
+/**
+ * get_tree_bdev_flags - Get a superblock based on a single block device
+ * @fc: The filesystem context holding the parameters
+ * @fill_super: Helper to initialise a new superblock
+ * @flags: GET_TREE_BDEV_* flags
+ */
+int get_tree_bdev_flags(struct fs_context *fc,
+		int (*fill_super)(struct super_block *sb,
+				  struct fs_context *fc), unsigned int flags)
+{
+	struct super_block *s;
+	int error = 0;
+	dev_t dev;
+
+	if (!fc->source)
+		return invalf(fc, "No source specified");
+
+	error = lookup_bdev(fc->source, &dev);
+	if (error) {
+		if (!(flags & GET_TREE_BDEV_QUIET_LOOKUP))
+			errorf(fc, "%s: Can't lookup blockdev", fc->source);
+		return error;
+	}
+	fc->sb_flags |= SB_NOSEC;
+	s = sget_dev(fc, dev);
+	if (IS_ERR(s))
+		return PTR_ERR(s);
+
+	if (s->s_root) {
+		/* Don't summarily change the RO/RW state. */
+		if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) {
+			warnf(fc, "%pg: Can't mount, would change RO state", s->s_bdev);
+			deactivate_locked_super(s);
+			return -EBUSY;
+		}
+	} else {
+		error = setup_bdev_super(s, fc->sb_flags, fc);
+		if (!error)
+			error = fill_super(s, fc);
+		if (error) {
+			deactivate_locked_super(s);
+			return error;
+		}
+		s->s_flags |= SB_ACTIVE;
+	}
+
+	BUG_ON(fc->root);
+	fc->root = dget(s->s_root);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(get_tree_bdev_flags);
+
+/**
+ * get_tree_bdev - Get a superblock based on a single block device
+ * @fc: The filesystem context holding the parameters
+ * @fill_super: Helper to initialise a new superblock
+ */
+int get_tree_bdev(struct fs_context *fc,
+		int (*fill_super)(struct super_block *,
+				  struct fs_context *))
+{
+	return get_tree_bdev_flags(fc, fill_super, 0);
+}
+EXPORT_SYMBOL(get_tree_bdev);
+
+void kill_block_super(struct super_block *sb)
+{
+	struct block_device *bdev = sb->s_bdev;
+
+	generic_shutdown_super(sb);
+	if (bdev) {
+		sync_blockdev(bdev);
+		fs_bdev_file_release(sb->s_bdev_file, sb);
+	}
+}
+
+EXPORT_SYMBOL(kill_block_super);
+#endif
+
+/**
+ * vfs_get_tree - Get the mountable root
+ * @fc: The superblock configuration context.
+ *
+ * The filesystem is invoked to get or create a superblock which can then later
+ * be used for mounting.  The filesystem places a pointer to the root to be
+ * used for mounting in @fc->root.
+ */
+int vfs_get_tree(struct fs_context *fc)
+{
+	struct super_block *sb;
+	int error;
+
+	if (fc->root)
+		return -EBUSY;
+
+	/* Get the mountable root in fc->root, with a ref on the root and a ref
+	 * on the superblock.
+	 */
+	error = fc->ops->get_tree(fc);
+	if (error < 0)
+		return error;
+
+	if (!fc->root) {
+		pr_err("Filesystem %s get_tree() didn't set fc->root, returned %i\n",
+		       fc->fs_type->name, error);
+		/* We don't know what the locking state of the superblock is -
+		 * if there is a superblock.
+		 */
+		BUG();
+	}
+
+	sb = fc->root->d_sb;
+	WARN_ON(!sb->s_bdi);
+
+	/*
+	 * super_wake() contains a memory barrier which also care of
+	 * ordering for super_cache_count(). We place it before setting
+	 * SB_BORN as the data dependency between the two functions is
+	 * the superblock structure contents that we just set up, not
+	 * the SB_BORN flag.
+	 */
+	super_wake(sb, SB_BORN);
+
+	error = security_sb_set_mnt_opts(sb, fc->security, 0, NULL);
+	if (unlikely(error)) {
+		fc_drop_locked(fc);
+		return error;
+	}
+
+	/*
+	 * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
+	 * but s_maxbytes was an unsigned long long for many releases. Throw
+	 * this warning for a little while to try and catch filesystems that
+	 * violate this rule.
+	 */
+	WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
+		"negative value (%lld)\n", fc->fs_type->name, sb->s_maxbytes);
+
+	return 0;
+}
+EXPORT_SYMBOL(vfs_get_tree);
+
+/*
+ * Setup private BDI for given superblock. It gets automatically cleaned up
+ * in generic_shutdown_super().
+ */
+int super_setup_bdi_name(struct super_block *sb, char *fmt, ...)
+{
+	struct backing_dev_info *bdi;
+	int err;
+	va_list args;
+
+	bdi = bdi_alloc(NUMA_NO_NODE);
+	if (!bdi)
+		return -ENOMEM;
+
+	va_start(args, fmt);
+	err = bdi_register_va(bdi, fmt, args);
+	va_end(args);
+	if (err) {
+		bdi_put(bdi);
+		return err;
+	}
+	WARN_ON(sb->s_bdi != &noop_backing_dev_info);
+	sb->s_bdi = bdi;
+	sb->s_iflags |= SB_I_PERSB_BDI;
+
+	return 0;
+}
+EXPORT_SYMBOL(super_setup_bdi_name);
+
+/*
+ * Setup private BDI for given superblock. I gets automatically cleaned up
+ * in generic_shutdown_super().
+ */
+int super_setup_bdi(struct super_block *sb)
+{
+	static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
+
+	return super_setup_bdi_name(sb, "%.28s-%ld", sb->s_type->name,
+				    atomic_long_inc_return(&bdi_seq));
+}
+EXPORT_SYMBOL(super_setup_bdi);
+
+/**
+ * sb_wait_write - wait until all writers to given file system finish
+ * @sb: the super for which we wait
+ * @level: type of writers we wait for (normal vs page fault)
+ *
+ * This function waits until there are no writers of given type to given file
+ * system.
+ */
+static void sb_wait_write(struct super_block *sb, int level)
+{
+	percpu_down_write(sb->s_writers.rw_sem + level-1);
+}
+
+/*
+ * We are going to return to userspace and forget about these locks, the
+ * ownership goes to the caller of thaw_super() which does unlock().
+ */
+static void lockdep_sb_freeze_release(struct super_block *sb)
+{
+	int level;
+
+	for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
+		percpu_rwsem_release(sb->s_writers.rw_sem + level, _THIS_IP_);
+}
+
+/*
+ * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb).
+ */
+static void lockdep_sb_freeze_acquire(struct super_block *sb)
+{
+	int level;
+
+	for (level = 0; level < SB_FREEZE_LEVELS; ++level)
+		percpu_rwsem_acquire(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
+}
+
+static void sb_freeze_unlock(struct super_block *sb, int level)
+{
+	for (level--; level >= 0; level--)
+		percpu_up_write(sb->s_writers.rw_sem + level);
+}
+
+static int wait_for_partially_frozen(struct super_block *sb)
+{
+	int ret = 0;
+
+	do {
+		unsigned short old = sb->s_writers.frozen;
+
+		up_write(&sb->s_umount);
+		ret = wait_var_event_killable(&sb->s_writers.frozen,
+					       sb->s_writers.frozen != old);
+		down_write(&sb->s_umount);
+	} while (ret == 0 &&
+		 sb->s_writers.frozen != SB_UNFROZEN &&
+		 sb->s_writers.frozen != SB_FREEZE_COMPLETE);
+
+	return ret;
+}
+
+#define FREEZE_HOLDERS (FREEZE_HOLDER_KERNEL | FREEZE_HOLDER_USERSPACE)
+#define FREEZE_FLAGS (FREEZE_HOLDERS | FREEZE_MAY_NEST | FREEZE_EXCL)
+
+static inline int freeze_inc(struct super_block *sb, enum freeze_holder who)
+{
+	WARN_ON_ONCE((who & ~FREEZE_FLAGS));
+	WARN_ON_ONCE(hweight32(who & FREEZE_HOLDERS) > 1);
+
+	if (who & FREEZE_HOLDER_KERNEL)
+		++sb->s_writers.freeze_kcount;
+	if (who & FREEZE_HOLDER_USERSPACE)
+		++sb->s_writers.freeze_ucount;
+	return sb->s_writers.freeze_kcount + sb->s_writers.freeze_ucount;
+}
+
+static inline int freeze_dec(struct super_block *sb, enum freeze_holder who)
+{
+	WARN_ON_ONCE((who & ~FREEZE_FLAGS));
+	WARN_ON_ONCE(hweight32(who & FREEZE_HOLDERS) > 1);
+
+	if ((who & FREEZE_HOLDER_KERNEL) && sb->s_writers.freeze_kcount)
+		--sb->s_writers.freeze_kcount;
+	if ((who & FREEZE_HOLDER_USERSPACE) && sb->s_writers.freeze_ucount)
+		--sb->s_writers.freeze_ucount;
+	return sb->s_writers.freeze_kcount + sb->s_writers.freeze_ucount;
+}
+
+static inline bool may_freeze(struct super_block *sb, enum freeze_holder who,
+			      const void *freeze_owner)
+{
+	lockdep_assert_held(&sb->s_umount);
+
+	WARN_ON_ONCE((who & ~FREEZE_FLAGS));
+	WARN_ON_ONCE(hweight32(who & FREEZE_HOLDERS) > 1);
+
+	if (who & FREEZE_EXCL) {
+		if (WARN_ON_ONCE(!(who & FREEZE_HOLDER_KERNEL)))
+			return false;
+		if (WARN_ON_ONCE(who & ~(FREEZE_EXCL | FREEZE_HOLDER_KERNEL)))
+			return false;
+		if (WARN_ON_ONCE(!freeze_owner))
+			return false;
+		/* This freeze already has a specific owner. */
+		if (sb->s_writers.freeze_owner)
+			return false;
+		/*
+		 * This is already frozen multiple times so we're just
+		 * going to take a reference count and mark the freeze as
+		 * being owned by the caller.
+		 */
+		if (sb->s_writers.freeze_kcount + sb->s_writers.freeze_ucount)
+			sb->s_writers.freeze_owner = freeze_owner;
+		return true;
+	}
+
+	if (who & FREEZE_HOLDER_KERNEL)
+		return (who & FREEZE_MAY_NEST) ||
+		       sb->s_writers.freeze_kcount == 0;
+	if (who & FREEZE_HOLDER_USERSPACE)
+		return (who & FREEZE_MAY_NEST) ||
+		       sb->s_writers.freeze_ucount == 0;
+	return false;
+}
+
+static inline bool may_unfreeze(struct super_block *sb, enum freeze_holder who,
+				const void *freeze_owner)
+{
+	lockdep_assert_held(&sb->s_umount);
+
+	WARN_ON_ONCE((who & ~FREEZE_FLAGS));
+	WARN_ON_ONCE(hweight32(who & FREEZE_HOLDERS) > 1);
+
+	if (who & FREEZE_EXCL) {
+		if (WARN_ON_ONCE(!(who & FREEZE_HOLDER_KERNEL)))
+			return false;
+		if (WARN_ON_ONCE(who & ~(FREEZE_EXCL | FREEZE_HOLDER_KERNEL)))
+			return false;
+		if (WARN_ON_ONCE(!freeze_owner))
+			return false;
+		if (WARN_ON_ONCE(sb->s_writers.freeze_kcount == 0))
+			return false;
+		/* This isn't exclusively frozen. */
+		if (!sb->s_writers.freeze_owner)
+			return false;
+		/* This isn't exclusively frozen by us. */
+		if (sb->s_writers.freeze_owner != freeze_owner)
+			return false;
+		/*
+		 * This is still frozen multiple times so we're just
+		 * going to drop our reference count and undo our
+		 * exclusive freeze.
+		 */
+		if ((sb->s_writers.freeze_kcount + sb->s_writers.freeze_ucount) > 1)
+			sb->s_writers.freeze_owner = NULL;
+		return true;
+	}
+
+	if (who & FREEZE_HOLDER_KERNEL) {
+		/*
+		 * Someone's trying to steal the reference belonging to
+		 * @sb->s_writers.freeze_owner.
+		 */
+		if (sb->s_writers.freeze_kcount == 1 &&
+		    sb->s_writers.freeze_owner)
+			return false;
+		return sb->s_writers.freeze_kcount > 0;
+	}
+
+	if (who & FREEZE_HOLDER_USERSPACE)
+		return sb->s_writers.freeze_ucount > 0;
+
+	return false;
+}
+
+/**
+ * freeze_super - lock the filesystem and force it into a consistent state
+ * @sb: the super to lock
+ * @who: context that wants to freeze
+ * @freeze_owner: owner of the freeze
+ *
+ * Syncs the super to make sure the filesystem is consistent and calls the fs's
+ * freeze_fs.  Subsequent calls to this without first thawing the fs may return
+ * -EBUSY.
+ *
+ * @who should be:
+ * * %FREEZE_HOLDER_USERSPACE if userspace wants to freeze the fs;
+ * * %FREEZE_HOLDER_KERNEL if the kernel wants to freeze the fs.
+ * * %FREEZE_MAY_NEST whether nesting freeze and thaw requests is allowed.
+ *
+ * The @who argument distinguishes between the kernel and userspace trying to
+ * freeze the filesystem.  Although there cannot be multiple kernel freezes or
+ * multiple userspace freezes in effect at any given time, the kernel and
+ * userspace can both hold a filesystem frozen.  The filesystem remains frozen
+ * until there are no kernel or userspace freezes in effect.
+ *
+ * A filesystem may hold multiple devices and thus a filesystems may be
+ * frozen through the block layer via multiple block devices. In this
+ * case the request is marked as being allowed to nest by passing
+ * FREEZE_MAY_NEST. The filesystem remains frozen until all block
+ * devices are unfrozen. If multiple freezes are attempted without
+ * FREEZE_MAY_NEST -EBUSY will be returned.
+ *
+ * During this function, sb->s_writers.frozen goes through these values:
+ *
+ * SB_UNFROZEN: File system is normal, all writes progress as usual.
+ *
+ * SB_FREEZE_WRITE: The file system is in the process of being frozen.  New
+ * writes should be blocked, though page faults are still allowed. We wait for
+ * all writes to complete and then proceed to the next stage.
+ *
+ * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
+ * but internal fs threads can still modify the filesystem (although they
+ * should not dirty new pages or inodes), writeback can run etc. After waiting
+ * for all running page faults we sync the filesystem which will clean all
+ * dirty pages and inodes (no new dirty pages or inodes can be created when
+ * sync is running).
+ *
+ * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
+ * modification are blocked (e.g. XFS preallocation truncation on inode
+ * reclaim). This is usually implemented by blocking new transactions for
+ * filesystems that have them and need this additional guard. After all
+ * internal writers are finished we call ->freeze_fs() to finish filesystem
+ * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
+ * mostly auxiliary for filesystems to verify they do not modify frozen fs.
+ *
+ * sb->s_writers.frozen is protected by sb->s_umount.
+ *
+ * Return: If the freeze was successful zero is returned. If the freeze
+ *         failed a negative error code is returned.
+ */
+int freeze_super(struct super_block *sb, enum freeze_holder who, const void *freeze_owner)
+{
+	int ret;
+
+	if (!super_lock_excl(sb)) {
+		WARN_ONCE(1, "Dying superblock while freezing!");
+		return -EINVAL;
+	}
+	atomic_inc(&sb->s_active);
+
+retry:
+	if (sb->s_writers.frozen == SB_FREEZE_COMPLETE) {
+		if (may_freeze(sb, who, freeze_owner))
+			ret = !!WARN_ON_ONCE(freeze_inc(sb, who) == 1);
+		else
+			ret = -EBUSY;
+		/* All freezers share a single active reference. */
+		deactivate_locked_super(sb);
+		return ret;
+	}
+
+	if (sb->s_writers.frozen != SB_UNFROZEN) {
+		ret = wait_for_partially_frozen(sb);
+		if (ret) {
+			deactivate_locked_super(sb);
+			return ret;
+		}
+
+		goto retry;
+	}
+
+	if (sb_rdonly(sb)) {
+		/* Nothing to do really... */
+		WARN_ON_ONCE(freeze_inc(sb, who) > 1);
+		sb->s_writers.freeze_owner = freeze_owner;
+		sb->s_writers.frozen = SB_FREEZE_COMPLETE;
+		wake_up_var(&sb->s_writers.frozen);
+		super_unlock_excl(sb);
+		return 0;
+	}
+
+	sb->s_writers.frozen = SB_FREEZE_WRITE;
+	/* Release s_umount to preserve sb_start_write -> s_umount ordering */
+	super_unlock_excl(sb);
+	sb_wait_write(sb, SB_FREEZE_WRITE);
+	__super_lock_excl(sb);
+
+	/* Now we go and block page faults... */
+	sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;
+	sb_wait_write(sb, SB_FREEZE_PAGEFAULT);
+
+	/* All writers are done so after syncing there won't be dirty data */
+	ret = sync_filesystem(sb);
+	if (ret) {
+		sb->s_writers.frozen = SB_UNFROZEN;
+		sb_freeze_unlock(sb, SB_FREEZE_PAGEFAULT);
+		wake_up_var(&sb->s_writers.frozen);
+		deactivate_locked_super(sb);
+		return ret;
+	}
+
+	/* Now wait for internal filesystem counter */
+	sb->s_writers.frozen = SB_FREEZE_FS;
+	sb_wait_write(sb, SB_FREEZE_FS);
+
+	if (sb->s_op->freeze_fs) {
+		ret = sb->s_op->freeze_fs(sb);
+		if (ret) {
+			printk(KERN_ERR
+				"VFS:Filesystem freeze failed\n");
+			sb->s_writers.frozen = SB_UNFROZEN;
+			sb_freeze_unlock(sb, SB_FREEZE_FS);
+			wake_up_var(&sb->s_writers.frozen);
+			deactivate_locked_super(sb);
+			return ret;
+		}
+	}
+	/*
+	 * For debugging purposes so that fs can warn if it sees write activity
+	 * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super().
+	 */
+	WARN_ON_ONCE(freeze_inc(sb, who) > 1);
+	sb->s_writers.freeze_owner = freeze_owner;
+	sb->s_writers.frozen = SB_FREEZE_COMPLETE;
+	wake_up_var(&sb->s_writers.frozen);
+	lockdep_sb_freeze_release(sb);
+	super_unlock_excl(sb);
+	return 0;
+}
+EXPORT_SYMBOL(freeze_super);
+
+/*
+ * Undoes the effect of a freeze_super_locked call.  If the filesystem is
+ * frozen both by userspace and the kernel, a thaw call from either source
+ * removes that state without releasing the other state or unlocking the
+ * filesystem.
+ */
+static int thaw_super_locked(struct super_block *sb, enum freeze_holder who,
+			     const void *freeze_owner)
+{
+	int error = -EINVAL;
+
+	if (sb->s_writers.frozen != SB_FREEZE_COMPLETE)
+		goto out_unlock;
+
+	if (!may_unfreeze(sb, who, freeze_owner))
+		goto out_unlock;
+
+	/*
+	 * All freezers share a single active reference. If other freezers
+	 * remain, drop our hold and report success; the superblock stays
+	 * frozen until the last holder thaws it.
+	 */
+	if (freeze_dec(sb, who)) {
+		error = 0;
+		goto out_unlock;
+	}
+
+	if (sb_rdonly(sb)) {
+		sb->s_writers.frozen = SB_UNFROZEN;
+		sb->s_writers.freeze_owner = NULL;
+		wake_up_var(&sb->s_writers.frozen);
+		goto out_deactivate;
+	}
+
+	lockdep_sb_freeze_acquire(sb);
+
+	if (sb->s_op->unfreeze_fs) {
+		error = sb->s_op->unfreeze_fs(sb);
+		if (error) {
+			pr_err("VFS: Filesystem thaw failed\n");
+			freeze_inc(sb, who);
+			lockdep_sb_freeze_release(sb);
+			goto out_unlock;
+		}
+	}
+
+	sb->s_writers.frozen = SB_UNFROZEN;
+	sb->s_writers.freeze_owner = NULL;
+	wake_up_var(&sb->s_writers.frozen);
+	sb_freeze_unlock(sb, SB_FREEZE_FS);
+out_deactivate:
+	deactivate_locked_super(sb);
+	return 0;
+
+out_unlock:
+	super_unlock_excl(sb);
+	return error;
+}
+
+/**
+ * thaw_super -- unlock filesystem
+ * @sb: the super to thaw
+ * @who: context that wants to freeze
+ * @freeze_owner: owner of the freeze
+ *
+ * Unlocks the filesystem and marks it writeable again after freeze_super()
+ * if there are no remaining freezes on the filesystem.
+ *
+ * @who should be:
+ * * %FREEZE_HOLDER_USERSPACE if userspace wants to thaw the fs;
+ * * %FREEZE_HOLDER_KERNEL if the kernel wants to thaw the fs.
+ * * %FREEZE_MAY_NEST whether nesting freeze and thaw requests is allowed
+ *
+ * A filesystem may hold multiple devices and thus a filesystems may
+ * have been frozen through the block layer via multiple block devices.
+ * The filesystem remains frozen until all block devices are unfrozen.
+ */
+int thaw_super(struct super_block *sb, enum freeze_holder who,
+	       const void *freeze_owner)
+{
+	if (!super_lock_excl(sb)) {
+		WARN_ONCE(1, "Dying superblock while thawing!");
+		return -EINVAL;
+	}
+	return thaw_super_locked(sb, who, freeze_owner);
+}
+EXPORT_SYMBOL(thaw_super);
+
+/*
+ * Create workqueue for deferred direct IO completions. We allocate the
+ * workqueue when it's first needed. This avoids creating workqueue for
+ * filesystems that don't need it and also allows us to create the workqueue
+ * late enough so the we can include s_id in the name of the workqueue.
+ */
+int sb_init_dio_done_wq(struct super_block *sb)
+{
+	struct workqueue_struct *old;
+	struct workqueue_struct *wq = alloc_workqueue("dio/%s",
+						      WQ_MEM_RECLAIM | WQ_PERCPU,
+						      0,
+						      sb->s_id);
+	if (!wq)
+		return -ENOMEM;
+
+	old = NULL;
+	/*
+	 * This has to be atomic as more DIOs can race to create the workqueue
+	 */
+	if (!try_cmpxchg(&sb->s_dio_done_wq, &old, wq)) {
+		/* Someone created workqueue before us? Free ours... */
+		destroy_workqueue(wq);
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(sb_init_dio_done_wq);