Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 667 insertions, 0 deletions

diff --git a/fs/file_table.c b/fs/file_table.c
new file mode 100644
index 000000000..c68b8c0a4
--- /dev/null
+++ b/fs/file_table.c
@@ -0,0 +1,667 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/fs/file_table.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *  Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
+ */
+
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/file.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/filelock.h>
+#include <linux/security.h>
+#include <linux/cred.h>
+#include <linux/eventpoll.h>
+#include <linux/rcupdate.h>
+#include <linux/mount.h>
+#include <linux/capability.h>
+#include <linux/cdev.h>
+#include <linux/fsnotify.h>
+#include <linux/sysctl.h>
+#include <linux/percpu_counter.h>
+#include <linux/percpu.h>
+#include <linux/task_work.h>
+#include <linux/swap.h>
+#include <linux/kmemleak.h>
+
+#include <linux/atomic.h>
+
+#include <asm/runtime-const.h>
+
+#include "internal.h"
+
+/* sysctl tunables... */
+static struct files_stat_struct files_stat = {
+	.max_files = NR_FILE
+};
+
+/* SLAB cache for file structures */
+static struct kmem_cache *__filp_cache __ro_after_init;
+#define filp_cache runtime_const_ptr(__filp_cache)
+static struct kmem_cache *__bfilp_cache __ro_after_init;
+#define bfilp_cache runtime_const_ptr(__bfilp_cache)
+
+static struct percpu_counter nr_files __cacheline_aligned_in_smp;
+
+/* Container for backing file with optional user path */
+struct backing_file {
+	struct file file;
+	union {
+		struct path user_path;
+		freeptr_t bf_freeptr;
+	};
+#ifdef CONFIG_SECURITY
+	void *security;
+#endif
+};
+
+#define backing_file(f) container_of(f, struct backing_file, file)
+
+const struct path *backing_file_user_path(const struct file *f)
+{
+	return &backing_file(f)->user_path;
+}
+EXPORT_SYMBOL_GPL(backing_file_user_path);
+
+void backing_file_set_user_path(struct file *f, const struct path *path)
+{
+	backing_file(f)->user_path = *path;
+}
+EXPORT_SYMBOL_GPL(backing_file_set_user_path);
+
+#ifdef CONFIG_SECURITY
+void *backing_file_security(const struct file *f)
+{
+	return backing_file(f)->security;
+}
+
+void backing_file_set_security(struct file *f, void *security)
+{
+	backing_file(f)->security = security;
+}
+#endif /* CONFIG_SECURITY */
+
+static inline void backing_file_free(struct backing_file *ff)
+{
+	security_backing_file_free(&ff->file);
+	path_put(&ff->user_path);
+	kmem_cache_free(bfilp_cache, ff);
+}
+
+static inline void file_free(struct file *f)
+{
+	security_file_free(f);
+	if (likely(!(f->f_mode & FMODE_NOACCOUNT)))
+		percpu_counter_dec(&nr_files);
+	put_cred(f->f_cred);
+	if (unlikely(f->f_mode & FMODE_BACKING)) {
+		backing_file_free(backing_file(f));
+	} else {
+		kmem_cache_free(filp_cache, f);
+	}
+}
+
+/*
+ * Return the total number of open files in the system
+ */
+static long get_nr_files(void)
+{
+	return percpu_counter_read_positive(&nr_files);
+}
+
+/*
+ * Return the maximum number of open files in the system
+ */
+unsigned long get_max_files(void)
+{
+	return files_stat.max_files;
+}
+EXPORT_SYMBOL_GPL(get_max_files);
+
+#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
+
+/*
+ * Handle nr_files sysctl
+ */
+static int proc_nr_files(const struct ctl_table *table, int write, void *buffer,
+			 size_t *lenp, loff_t *ppos)
+{
+	files_stat.nr_files = percpu_counter_sum_positive(&nr_files);
+	return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
+}
+
+static const struct ctl_table fs_stat_sysctls[] = {
+	{
+		.procname	= "file-nr",
+		.data		= &files_stat,
+		.maxlen		= sizeof(files_stat),
+		.mode		= 0444,
+		.proc_handler	= proc_nr_files,
+	},
+	{
+		.procname	= "file-max",
+		.data		= &files_stat.max_files,
+		.maxlen		= sizeof(files_stat.max_files),
+		.mode		= 0644,
+		.proc_handler	= proc_doulongvec_minmax,
+		.extra1		= SYSCTL_LONG_ZERO,
+		.extra2		= SYSCTL_LONG_MAX,
+	},
+	{
+		.procname	= "nr_open",
+		.data		= &sysctl_nr_open,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= proc_douintvec_minmax,
+		.extra1		= &sysctl_nr_open_min,
+		.extra2		= &sysctl_nr_open_max,
+	},
+};
+
+static int __init init_fs_stat_sysctls(void)
+{
+	register_sysctl_init("fs", fs_stat_sysctls);
+	if (IS_ENABLED(CONFIG_BINFMT_MISC)) {
+		struct ctl_table_header *hdr;
+
+		hdr = register_sysctl_mount_point("fs/binfmt_misc");
+		kmemleak_not_leak(hdr);
+	}
+	return 0;
+}
+fs_initcall(init_fs_stat_sysctls);
+#endif
+
+static int init_file(struct file *f, int flags, const struct cred *cred)
+{
+	int error;
+
+	f->f_cred = get_cred(cred);
+	error = security_file_alloc(f);
+	if (unlikely(error)) {
+		put_cred(f->f_cred);
+		return error;
+	}
+
+	spin_lock_init(&f->f_lock);
+	/*
+	 * Note that f_pos_lock is only used for files raising
+	 * FMODE_ATOMIC_POS and directories. Other files such as pipes
+	 * don't need it and since f_pos_lock is in a union may reuse
+	 * the space for other purposes. They are expected to initialize
+	 * the respective member when opening the file.
+	 */
+	mutex_init(&f->f_pos_lock);
+	memset(&f->__f_path, 0, sizeof(f->f_path));
+	memset(&f->f_ra, 0, sizeof(f->f_ra));
+
+	f->f_flags	= flags;
+	f->f_mode	= OPEN_FMODE(flags);
+	/*
+	 * Disable permission and pre-content events for all files by default.
+	 * They may be enabled later by fsnotify_open_perm_and_set_mode().
+	 */
+	file_set_fsnotify_mode(f, FMODE_NONOTIFY_PERM);
+
+	f->f_op		= NULL;
+	f->f_mapping	= NULL;
+	f->private_data = NULL;
+	f->f_inode	= NULL;
+	f->f_owner	= NULL;
+#ifdef CONFIG_EPOLL
+	f->f_ep		= NULL;
+#endif
+
+	f->f_iocb_flags = 0;
+	f->f_pos	= 0;
+	f->f_wb_err	= 0;
+	f->f_sb_err	= 0;
+
+	/*
+	 * We're SLAB_TYPESAFE_BY_RCU so initialize f_ref last. While
+	 * fget-rcu pattern users need to be able to handle spurious
+	 * refcount bumps we should reinitialize the reused file first.
+	 */
+	file_ref_init(&f->f_ref, 1);
+	return 0;
+}
+
+/* Find an unused file structure and return a pointer to it.
+ * Returns an error pointer if some error happened, e.g., we exceed the file
+ * structures limit, run out of memory or operation is not permitted.
+ *
+ * Be very careful using this.  You are responsible for
+ * getting write access to any mount that you might assign
+ * to this filp, if it is opened for write.  If this is not
+ * done, the mount's writer count will be wrong
+ * and a warning at __fput() time.
+ */
+struct file *alloc_empty_file(int flags, const struct cred *cred)
+{
+	static long old_max;
+	struct file *f;
+	int error;
+
+	/*
+	 * Privileged users can go above max_files
+	 */
+	if (unlikely(get_nr_files() >= files_stat.max_files) &&
+	    !capable(CAP_SYS_ADMIN)) {
+		/*
+		 * percpu_counters are inaccurate.  Do an expensive check before
+		 * we go and fail.
+		 */
+		if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
+			goto over;
+	}
+
+	f = kmem_cache_alloc(filp_cache, GFP_KERNEL);
+	if (unlikely(!f))
+		return ERR_PTR(-ENOMEM);
+
+	error = init_file(f, flags, cred);
+	if (unlikely(error)) {
+		kmem_cache_free(filp_cache, f);
+		return ERR_PTR(error);
+	}
+
+	percpu_counter_inc(&nr_files);
+
+	return f;
+
+over:
+	/* Ran out of filps - report that */
+	if (get_nr_files() > old_max) {
+		pr_info("VFS: file-max limit %lu reached\n", get_max_files());
+		old_max = get_nr_files();
+	}
+	return ERR_PTR(-ENFILE);
+}
+
+/*
+ * Variant of alloc_empty_file() that doesn't check and modify nr_files.
+ *
+ * This is only for kernel internal use, and the allocate file must not be
+ * installed into file tables or such.
+ */
+struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred)
+{
+	struct file *f;
+	int error;
+
+	f = kmem_cache_alloc(filp_cache, GFP_KERNEL);
+	if (unlikely(!f))
+		return ERR_PTR(-ENOMEM);
+
+	error = init_file(f, flags, cred);
+	if (unlikely(error)) {
+		kmem_cache_free(filp_cache, f);
+		return ERR_PTR(error);
+	}
+
+	f->f_mode |= FMODE_NOACCOUNT;
+
+	return f;
+}
+
+static int init_backing_file(struct backing_file *ff,
+			     const struct file *user_file)
+{
+	memset(&ff->user_path, 0, sizeof(ff->user_path));
+	backing_file_set_security(&ff->file, NULL);
+	return security_backing_file_alloc(&ff->file, user_file);
+}
+
+/*
+ * Variant of alloc_empty_file() that allocates a backing_file container
+ * and doesn't check and modify nr_files.
+ *
+ * This is only for kernel internal use, and the allocate file must not be
+ * installed into file tables or such.
+ */
+struct file *alloc_empty_backing_file(int flags, const struct cred *cred,
+				      const struct file *user_file)
+{
+	struct backing_file *ff;
+	int error;
+
+	ff = kmem_cache_alloc(bfilp_cache, GFP_KERNEL);
+	if (unlikely(!ff))
+		return ERR_PTR(-ENOMEM);
+
+	error = init_file(&ff->file, flags, cred);
+	if (unlikely(error)) {
+		kmem_cache_free(bfilp_cache, ff);
+		return ERR_PTR(error);
+	}
+
+	/* The f_mode flags must be set before fput(). */
+	ff->file.f_mode |= FMODE_BACKING | FMODE_NOACCOUNT;
+	error = init_backing_file(ff, user_file);
+	if (unlikely(error)) {
+		fput(&ff->file);
+		return ERR_PTR(error);
+	}
+
+	return &ff->file;
+}
+EXPORT_SYMBOL_GPL(alloc_empty_backing_file);
+
+/**
+ * file_init_path - initialize a 'struct file' based on path
+ *
+ * @file: the file to set up
+ * @path: the (dentry, vfsmount) pair for the new file
+ * @fop: the 'struct file_operations' for the new file
+ */
+static void file_init_path(struct file *file, const struct path *path,
+			   const struct file_operations *fop)
+{
+	file->__f_path = *path;
+	file->f_inode = path->dentry->d_inode;
+	file->f_mapping = path->dentry->d_inode->i_mapping;
+	file->f_wb_err = filemap_sample_wb_err(file->f_mapping);
+	file->f_sb_err = file_sample_sb_err(file);
+	if (fop->llseek)
+		file->f_mode |= FMODE_LSEEK;
+	if ((file->f_mode & FMODE_READ) &&
+	     likely(fop->read || fop->read_iter))
+		file->f_mode |= FMODE_CAN_READ;
+	if ((file->f_mode & FMODE_WRITE) &&
+	     likely(fop->write || fop->write_iter))
+		file->f_mode |= FMODE_CAN_WRITE;
+	file->f_iocb_flags = iocb_flags(file);
+	file->f_mode |= FMODE_OPENED;
+	file->f_op = fop;
+	if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
+		i_readcount_inc(path->dentry->d_inode);
+}
+
+/**
+ * alloc_file - allocate and initialize a 'struct file'
+ *
+ * @path: the (dentry, vfsmount) pair for the new file
+ * @flags: O_... flags with which the new file will be opened
+ * @fop: the 'struct file_operations' for the new file
+ */
+static struct file *alloc_file(const struct path *path, int flags,
+		const struct file_operations *fop)
+{
+	struct file *file;
+
+	file = alloc_empty_file(flags, current_cred());
+	if (!IS_ERR(file))
+		file_init_path(file, path, fop);
+	return file;
+}
+
+static inline int alloc_path_pseudo(const char *name, struct inode *inode,
+				    struct vfsmount *mnt, struct path *path)
+{
+	if (WARN_ON_ONCE(S_ISDIR(inode->i_mode)))
+		return -EINVAL;
+	path->dentry = d_alloc_pseudo(mnt->mnt_sb, &QSTR(name));
+	if (!path->dentry)
+		return -ENOMEM;
+	path->mnt = mntget(mnt);
+	d_instantiate(path->dentry, inode);
+	return 0;
+}
+
+struct file *alloc_file_pseudo(struct inode *inode, struct vfsmount *mnt,
+			       const char *name, int flags,
+			       const struct file_operations *fops)
+{
+	int ret;
+	struct path path;
+	struct file *file;
+
+	ret = alloc_path_pseudo(name, inode, mnt, &path);
+	if (ret)
+		return ERR_PTR(ret);
+
+	file = alloc_file(&path, flags, fops);
+	if (IS_ERR(file)) {
+		ihold(inode);
+		path_put(&path);
+		return file;
+	}
+	/*
+	 * Disable all fsnotify events for pseudo files by default.
+	 * They may be enabled by caller with file_set_fsnotify_mode().
+	 */
+	file_set_fsnotify_mode(file, FMODE_NONOTIFY);
+	return file;
+}
+EXPORT_SYMBOL(alloc_file_pseudo);
+
+struct file *alloc_file_pseudo_noaccount(struct inode *inode,
+					 struct vfsmount *mnt, const char *name,
+					 int flags,
+					 const struct file_operations *fops)
+{
+	int ret;
+	struct path path;
+	struct file *file;
+
+	ret = alloc_path_pseudo(name, inode, mnt, &path);
+	if (ret)
+		return ERR_PTR(ret);
+
+	file = alloc_empty_file_noaccount(flags, current_cred());
+	if (IS_ERR(file)) {
+		ihold(inode);
+		path_put(&path);
+		return file;
+	}
+	file_init_path(file, &path, fops);
+	/*
+	 * Disable all fsnotify events for pseudo files by default.
+	 * They may be enabled by caller with file_set_fsnotify_mode().
+	 */
+	file_set_fsnotify_mode(file, FMODE_NONOTIFY);
+	return file;
+}
+EXPORT_SYMBOL_GPL(alloc_file_pseudo_noaccount);
+
+struct file *alloc_file_clone(struct file *base, int flags,
+				const struct file_operations *fops)
+{
+	struct file *f;
+
+	f = alloc_file(&base->f_path, flags, fops);
+	if (!IS_ERR(f)) {
+		path_get(&f->f_path);
+		f->f_mapping = base->f_mapping;
+	}
+	return f;
+}
+
+/* the real guts of fput() - releasing the last reference to file
+ */
+static void __fput(struct file *file)
+{
+	struct dentry *dentry = file->f_path.dentry;
+	struct vfsmount *mnt = file->f_path.mnt;
+	struct inode *inode = file->f_inode;
+	fmode_t mode = file->f_mode;
+
+	if (unlikely(!(file->f_mode & FMODE_OPENED)))
+		goto out;
+
+	might_sleep();
+
+	fsnotify_close(file);
+	/*
+	 * The function eventpoll_release() should be the first called
+	 * in the file cleanup chain.
+	 */
+	eventpoll_release(file);
+	locks_remove_file(file);
+
+	security_file_release(file);
+	if (unlikely(file->f_flags & FASYNC)) {
+		if (file->f_op->fasync)
+			file->f_op->fasync(-1, file, 0);
+	}
+	if (file->f_op->release)
+		file->f_op->release(inode, file);
+	if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL &&
+		     !(mode & FMODE_PATH))) {
+		cdev_put(inode->i_cdev);
+	}
+	fops_put(file->f_op);
+	file_f_owner_release(file);
+	put_file_access(file);
+	dput(dentry);
+	if (unlikely(mode & FMODE_NEED_UNMOUNT))
+		dissolve_on_fput(mnt);
+	mntput(mnt);
+out:
+	file_free(file);
+}
+
+static LLIST_HEAD(delayed_fput_list);
+static void delayed_fput(struct work_struct *unused)
+{
+	struct llist_node *node = llist_del_all(&delayed_fput_list);
+	struct file *f, *t;
+
+	llist_for_each_entry_safe(f, t, node, f_llist)
+		__fput(f);
+}
+
+static void ____fput(struct callback_head *work)
+{
+	__fput(container_of(work, struct file, f_task_work));
+}
+
+static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput);
+
+/*
+ * If kernel thread really needs to have the final fput() it has done
+ * to complete, call this.  The only user right now is the boot - we
+ * *do* need to make sure our writes to binaries on initramfs has
+ * not left us with opened struct file waiting for __fput() - execve()
+ * won't work without that.  Please, don't add more callers without
+ * very good reasons; in particular, never call that with locks
+ * held and never call that from a thread that might need to do
+ * some work on any kind of umount.
+ */
+void flush_delayed_fput(void)
+{
+	delayed_fput(NULL);
+	flush_delayed_work(&delayed_fput_work);
+}
+EXPORT_SYMBOL_GPL(flush_delayed_fput);
+
+static void __fput_deferred(struct file *file)
+{
+	struct task_struct *task = current;
+
+	if (unlikely(!(file->f_mode & (FMODE_BACKING | FMODE_OPENED)))) {
+		file_free(file);
+		return;
+	}
+
+	if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
+		init_task_work(&file->f_task_work, ____fput);
+		if (!task_work_add(task, &file->f_task_work, TWA_RESUME))
+			return;
+		/*
+		 * After this task has run exit_task_work(),
+		 * task_work_add() will fail.  Fall through to delayed
+		 * fput to avoid leaking *file.
+		 */
+	}
+
+	if (llist_add(&file->f_llist, &delayed_fput_list))
+		schedule_delayed_work(&delayed_fput_work, 1);
+}
+
+void fput(struct file *file)
+{
+	if (unlikely(file_ref_put(&file->f_ref)))
+		__fput_deferred(file);
+}
+EXPORT_SYMBOL(fput);
+
+/*
+ * synchronous analog of fput(); for kernel threads that might be needed
+ * in some umount() (and thus can't use flush_delayed_fput() without
+ * risking deadlocks), need to wait for completion of __fput() and know
+ * for this specific struct file it won't involve anything that would
+ * need them.  Use only if you really need it - at the very least,
+ * don't blindly convert fput() by kernel thread to that.
+ */
+void __fput_sync(struct file *file)
+{
+	if (file_ref_put(&file->f_ref))
+		__fput(file);
+}
+EXPORT_SYMBOL(__fput_sync);
+
+/*
+ * Equivalent to __fput_sync(), but optimized for being called with the last
+ * reference.
+ *
+ * See file_ref_put_close() for details.
+ */
+void fput_close_sync(struct file *file)
+{
+	if (likely(file_ref_put_close(&file->f_ref)))
+		__fput(file);
+}
+
+/*
+ * Equivalent to fput(), but optimized for being called with the last
+ * reference.
+ *
+ * See file_ref_put_close() for details.
+ */
+void fput_close(struct file *file)
+{
+	if (file_ref_put_close(&file->f_ref))
+		__fput_deferred(file);
+}
+
+void __init files_init(void)
+{
+	struct kmem_cache_args args = {
+		.use_freeptr_offset = true,
+		.freeptr_offset = offsetof(struct file, f_freeptr),
+	};
+
+	__filp_cache = kmem_cache_create("filp", sizeof(struct file), &args,
+				SLAB_HWCACHE_ALIGN | SLAB_PANIC |
+				SLAB_ACCOUNT | SLAB_TYPESAFE_BY_RCU);
+	runtime_const_init(ptr, __filp_cache);
+
+	args.freeptr_offset = offsetof(struct backing_file, bf_freeptr);
+	__bfilp_cache = kmem_cache_create("bfilp", sizeof(struct backing_file),
+				&args, SLAB_HWCACHE_ALIGN | SLAB_PANIC |
+				SLAB_ACCOUNT | SLAB_TYPESAFE_BY_RCU);
+	runtime_const_init(ptr, __bfilp_cache);
+
+	percpu_counter_init(&nr_files, 0, GFP_KERNEL);
+}
+
+/*
+ * One file with associated inode and dcache is very roughly 1K. Per default
+ * do not use more than 10% of our memory for files.
+ */
+void __init files_maxfiles_init(void)
+{
+	unsigned long n;
+	unsigned long nr_pages = totalram_pages();
+	unsigned long memreserve = (nr_pages - nr_free_pages()) * 3/2;
+
+	memreserve = min(memreserve, nr_pages - 1);
+	n = ((nr_pages - memreserve) * (PAGE_SIZE / 1024)) / 10;
+
+	files_stat.max_files = max_t(unsigned long, n, NR_FILE);
+}