// SPDX-License-Identifier: GPL-2.0-only
/*
* fs/kernfs/file.c - kernfs file implementation
*
* Copyright (c) 2001-3 Patrick Mochel
* Copyright (c) 2007 SUSE Linux Products GmbH
* Copyright (c) 2007, 2013 Tejun Heo <[email protected]>
*/
#include <linux/fs.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/pagemap.h>
#include <linux/sched/mm.h>
#include <linux/fsnotify.h>
#include <linux/uio.h>
#include "kernfs-internal.h"
struct kernfs_open_node {
struct rcu_head rcu_head;
atomic_t event;
wait_queue_head_t poll;
struct list_head files; /* goes through kernfs_open_file.list */
unsigned int nr_mmapped;
unsigned int nr_to_release;
};
/*
* kernfs_notify() may be called from any context and bounces notifications
* through a work item. To minimize space overhead in kernfs_node, the
* pending queue is implemented as a singly linked list of kernfs_nodes.
* The list is terminated with the self pointer so that whether a
* kernfs_node is on the list or not can be determined by testing the next
* pointer for %NULL.
*/
#define KERNFS_NOTIFY_EOL ((void *)&kernfs_notify_list)
static DEFINE_SPINLOCK(kernfs_notify_lock);
static struct kernfs_node *kernfs_notify_list = KERNFS_NOTIFY_EOL;
static inline struct mutex *kernfs_open_file_mutex_ptr(struct kernfs_node *kn)
{
int idx = hash_ptr(kn, NR_KERNFS_LOCK_BITS);
return &kernfs_locks->open_file_mutex[idx];
}
static inline struct mutex *kernfs_open_file_mutex_lock(struct kernfs_node *kn)
{
struct mutex *lock;
lock = kernfs_open_file_mutex_ptr(kn);
mutex_lock(lock);
return lock;
}
/**
* of_on - Get the kernfs_open_node of the specified kernfs_open_file
* @of: target kernfs_open_file
*
* Return: the kernfs_open_node of the kernfs_open_file
*/
static struct kernfs_open_node *of_on(struct kernfs_open_file *of)
{
return rcu_dereference_protected(of->kn->attr.open,
!list_empty(&of->list));
}
/**
* kernfs_deref_open_node_locked - Get kernfs_open_node corresponding to @kn
*
* @kn: target kernfs_node.
*
* Fetch and return ->attr.open of @kn when caller holds the
* kernfs_open_file_mutex_ptr(kn).
*
* Update of ->attr.open happens under kernfs_open_file_mutex_ptr(kn). So when
* the caller guarantees that this mutex is being held, other updaters can't
* change ->attr.open and this means that we can safely deref ->attr.open
* outside RCU read-side critical section.
*
* The caller needs to make sure that kernfs_open_file_mutex is held.
*
* Return: @kn->attr.open when kernfs_open_file_mutex is held.
*/
static struct kernfs_open_node *
kernfs_deref_open_node_locked(struct kernfs_node *kn)
{
return rcu_dereference_protected(kn->attr.open,
lockdep_is_held(kernfs_open_file_mutex_ptr(kn)));
}
static struct kernfs_open_file *kernfs_of(struct file *file)
{
return ((struct seq_file *)file->private_data)->private;
}
/*
* Determine the kernfs_ops for the given kernfs_node. This function must
* be called while holding an active reference.
*/
static const struct kernfs_ops *kernfs_ops(struct kernfs_node *kn)
{
if (kn->flags & KERNFS_LOCKDEP)
lockdep_assert_held(kn);
return kn->attr.ops;
}
/*
* As kernfs_seq_stop() is also called after kernfs_seq_start() or
* kernfs_seq_next() failure, it needs to distinguish whether it's stopping
* a seq_file iteration which is fully initialized with an active reference
* or an aborted kernfs_seq_start() due to get_active failure. The
* position pointer is the only context for each seq_file iteration and
* thus the stop condition should be encoded in it. As the return value is
* directly visible to userland, ERR_PTR(-ENODEV) is the only acceptable
* choice to indicate get_active failure.
*
* Unfortunately, this is complicated due to the optional custom seq_file
* operations which may return ERR_PTR(-ENODEV) too. kernfs_seq_stop()
* can't distinguish whether ERR_PTR(-ENODEV) is from get_active failure or
* custom seq_file operations and thus can't decide whether put_active
* should be performed or not only on ERR_PTR(-ENODEV).
*
* This is worked around by factoring out the custom seq_stop() and
* put_active part into kernfs_seq_stop_active(), skipping it from
* kernfs_seq_stop() if ERR_PTR(-ENODEV) while invoking it directly after
* custom seq_file operations fail with ERR_PTR(-ENODEV) - this ensures
* that kernfs_seq_stop_active() is skipped only after get_active failure.
*/
static void kernfs_seq_stop_active(struct seq_file *sf, void *v)
{
struct kernfs_open_file *of = sf->private;
const struct kernfs_ops *ops = kernfs_ops(of->kn);
if (ops->seq_stop)
ops->seq_stop(sf, v);
kernfs_put_active(of->kn);
}
static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
{
struct kernfs_open_file *of = sf->private;
const struct kernfs_ops *ops;
/*
* @of->mutex nests outside active ref and is primarily to ensure that
* the ops aren't called concurrently for the same open file.
*/
mutex_lock(&of->mutex);
if (!kernfs_get_active(of->kn))
return ERR_PTR(-ENODEV);
ops = kernfs_ops(of->kn);
if (ops->seq_start) {
void *next = ops->seq_start(sf, ppos);
/* see the comment above kernfs_seq_stop_active() */
if (next == ERR_PTR(-ENODEV))
kernfs_seq_stop_active(sf, next);
return next;
}
return single_start(sf, ppos);
}
static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos)
{
struct kernfs_open_file *of = sf->private;
const struct kernfs_ops *ops = kernfs_ops(of->kn);
if (ops->seq_next) {
void *next = ops->seq_next(sf, v, ppos);
/* see the comment above kernfs_seq_stop_active() */
if (next == ERR_PTR(-ENODEV))
kernfs_seq_stop_active(sf, next);
return next;
} else {
/*
* The same behavior and code as single_open(), always
* terminate after the initial read.
*/
++*ppos;
return NULL;
}
}
static void kernfs_seq_stop(struct seq_file *sf, void *v)
{
struct kernfs_open_file *of = sf->private;
if (v != ERR_PTR(-ENODEV))
kernfs_seq_stop_active(sf, v);
mutex_unlock(&of->mutex);
}
static int kernfs_seq_show(struct seq_file *sf, void *v)
{
struct kernfs_open_file *of = sf->private;
of->event = atomic_read(&of_on(of)->event);
return of->kn->attr.ops->seq_show(sf, v);
}
static const struct seq_operations kernfs_seq_ops = {
.start = kernfs_seq_start,
.next = kernfs_seq_next,
.stop = kernfs_seq_stop,
.show = kernfs_seq_show,
};
/*
* As reading a bin file can have side-effects, the exact offset and bytes
* specified in read(2) call should be passed to the read callback making
* it difficult to use seq_file. Implement simplistic custom buffering for
* bin files.
*/
static ssize_t kernfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct kernfs_open_file *of = kernfs_of(iocb->ki_filp);
ssize_t len = min_t(size_t, iov_iter_count(iter), PAGE_SIZE);
const struct kernfs_ops *ops;
char *buf;
buf = of->prealloc_buf;
if (buf)
mutex_lock(&of->prealloc_mutex);
else
buf = kmalloc(len, GFP_KERNEL);
if (!buf)
return -ENOMEM;
/*
* @of->mutex nests outside active ref and is used both to ensure that
* the ops aren't called concurrently for the same open file.
*/
mutex_lock(&of->mutex);
if (!kernfs_get_active(of->kn)) {
len = -ENODEV;
mutex_unlock(&of->mutex);
goto out_free;
}
of->event = atomic_read(&of_on(of)->event);
ops = kernfs_ops(of->kn);
if (ops->read)
len = ops->read(of, buf, len, iocb->ki_pos);
else
len = -EINVAL;
kernfs_put_active(of->kn);
mutex_unlock(&of->mutex);
if (len < 0)
goto out_free;
if (copy_to_iter(buf, len, iter) != len) {
len = -EFAULT;
goto out_free;
}
iocb->ki_pos += len;
out_free:
if (buf == of->prealloc_buf)
mutex_unlock(&of->prealloc_mutex);
else
kfree(buf);
return len;
}
static ssize_t kernfs_fop_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
if (kernfs_of(iocb->ki_filp)->kn->flags & KERNFS_HAS_SEQ_SHOW)
return seq_read_iter(iocb, iter);
return kernfs_file_read_iter(iocb, iter);
}
/*
* Copy data in from userland and pass it to the matching kernfs write
* operation.
*
* There is no easy way for us to know if userspace is only doing a partial
* write, so we don't support them. We expect the entire buffer to come on
* the first write. Hint: if you're writing a value, first read the file,
* modify only the value you're changing, then write entire buffer
* back.
*/
static ssize_t kernfs_fop_write_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct kernfs_open_file *of = kernfs_of(iocb->ki_filp);
ssize_t len = iov_iter_count(iter);
const struct kernfs_ops *ops;
char *buf;
if (of->atomic_write_len) {
if (len > of->atomic_write_len)
return -E2BIG;
} else {
len = min_t(size_t, len, PAGE_SIZE);
}
buf = of->prealloc_buf;
if (buf)
mutex_lock(&of->prealloc_mutex);
else
buf = kmalloc(len + 1, GFP_KERNEL);
if (!buf)
return -ENOMEM;
if (copy_from_iter(buf, len, iter) != len) {
len = -EFAULT;
goto out_free;
}
buf[len] = '\0'; /* guarantee string termination */
/*
* @of->mutex nests outside active ref and is used both to ensure that
* the ops aren't called concurrently for the same open file.
*/
mutex_lock(&of->mutex);
if (!kernfs_get_active(of->kn)) {
mutex_unlock(&of->mutex);
len = -ENODEV;
goto out_free;
}
ops = kernfs_ops(of->kn);
if (ops->write)
len = ops->write(of, buf, len, iocb->ki_pos);
else
len = -EINVAL;
kernfs_put_active(of->kn);
mutex_unlock(&of->mutex);
if (len > 0)
iocb->ki_pos += len;
out_free:
if (buf == of->prealloc_buf)
mutex_unlock(&of->prealloc_mutex);
else
kfree(buf);
return len;
}
static void kernfs_vma_open(struct vm_area_struct *vma)
{
struct file *file = vma->vm_file;
struct kernfs_open_file *of = kernfs_of(file);
if (!of->vm_ops)
return;
if (!kernfs_get_active(of->kn))
return;
if (of->vm_ops->open)
of->vm_ops->open(vma);
kernfs_put_active(of->kn);
}
static vm_fault_t kernfs_vma_fault(struct vm_fault *vmf)
{
struct file *file = vmf->vma->vm_file;
struct kernfs_open_file *of = kernfs_of(file);
vm_fault_t ret;
if (!of->vm_ops)
return VM_FAULT_SIGBUS;
if (!kernfs_get_active(of->kn))
return VM_FAULT_SIGBUS;
ret = VM_FAULT_SIGBUS;
if (of->vm_ops->fault)
ret = of->vm_ops->fault(vmf);
kernfs_put_active(of->kn);
return ret;
}
static vm_fault_t kernfs_vma_page_mkwrite(struct vm_fault *vmf)
{
struct file *file = vmf->vma->vm_file;
struct kernfs_open_file *of = kernfs_of(file);
vm_fault_t ret;
if (!of->vm_ops)
return VM_FAULT_SIGBUS;
if (!kernfs_get_active(of->kn))
return VM_FAULT_SIGBUS;
ret = 0;
if (of->vm_ops->page_mkwrite)
ret = of->vm_ops->page_mkwrite(vmf);
else
file_update_time(file);
kernfs_put_active(of->kn);
return ret;
}
static int kernfs_vma_access(struct vm_area_struct *vma, unsigned long addr,
void *buf, int len, int write)
{
struct file *file = vma->vm_file;
struct kernfs_open_file *of = kernfs_of(file);
int ret;
if (!of->vm_ops)
return -EINVAL;
if (!kernfs_get_active(of->kn))
return -EINVAL;
ret = -EINVAL;
if (of->vm_ops->access)
ret = of->vm_ops->access(vma, addr, buf, len, write);
kernfs_put_active(of->kn);
return ret;
}
static const struct vm_operations_struct kernfs_vm_ops = {
.open = kernfs_vma_open,
.fault = kernfs_vma_fault,
.page_mkwrite = kernfs_vma_page_mkwrite,
.access = kernfs_vma_access,
};
static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
{
struct kernfs_open_file *of = kernfs_of(file);
const struct kernfs_ops *ops;
int rc;
/*
* mmap path and of->mutex are prone to triggering spurious lockdep
* warnings and we don't want to add spurious locking dependency
* between the two. Check whether mmap is actually implemented
* without grabbing @of->mutex by testing HAS_MMAP flag. See the
* comment in kernfs_fop_open() for more details.
*/
if (!(of->kn->flags & KERNFS_HAS_MMAP))
return -ENODEV;
mutex_lock(&of->mutex);
rc = -ENODEV;
if (!kernfs_get_active(of->kn))
goto out_unlock;
ops = kernfs_ops(of->kn);
rc = ops->mmap(of, vma);
if (rc)
goto out_put;
/*
* PowerPC's pci_mmap of legacy_mem uses shmem_zero_setup()
* to satisfy versions of X which crash if the mmap fails: that
* substitutes a new vm_file, and we don't then want bin_vm_ops.
*/
if (vma->vm_file != file)
goto out_put;
rc = -EINVAL;
if (of->mmapped && of->vm_ops != vma->vm_ops)
goto out_put;
/*
* It is not possible to successfully wrap close.
* So error if someone is trying to use close.
*/
if (vma->vm_ops && vma->vm_ops->close)
goto out_put;
rc = 0;
if (!of->mmapped) {
of->mmapped = true;
of_on(of)->nr_mmapped++;
of->vm_ops = vma->vm_ops;
}
vma->vm_ops = &kernfs_vm_ops;
out_put:
kernfs_put_active(of->kn);
out_unlock:
mutex_unlock(&of->mutex);
return rc;
}
/**
* kernfs_get_open_node - get or create kernfs_open_node
* @kn: target kernfs_node
* @of: kernfs_open_file for this instance of open
*
* If @kn->attr.open exists, increment its reference count; otherwise,
* create one. @of is chained to the files list.
*
* Locking:
* Kernel thread context (may sleep).
*
* Return:
* %0 on success, -errno on failure.
*/
static int kernfs_get_open_node(struct kernfs_node *kn,
struct kernfs_open_file *of)
{
struct kernfs_open_node *on;
struct mutex *mutex;
mutex = kernfs_open_file_mutex_lock(kn);
on = kernfs_deref_open_node_locked(kn);
if (!on) {
/* not there, initialize a new one */
on = kzalloc(sizeof(*on), GFP_KERNEL);
if (!on) {
mutex_unlock(mutex);
return -ENOMEM;
}
atomic_set(&on->event, 1);
init_waitqueue_head(&on->poll);
INIT_LIST_HEAD(&on->files);
rcu_assign_pointer(kn->attr.open, on);
}
list_add_tail(&of->list, &on->files);
if (kn->flags & KERNFS_HAS_RELEASE)
on->nr_to_release++;
mutex_unlock(mutex);
return 0;
}
/**
* kernfs_unlink_open_file - Unlink @of from @kn.
*
* @kn: target kernfs_node
* @of: associated kernfs_open_file
* @open_failed: ->open() failed, cancel ->release()
*
* Unlink @of from list of @kn's associated open files. If list of
* associated open files becomes empty, disassociate and free
* kernfs_open_node.
*
* LOCKING:
* None.
*/
static void kernfs_unlink_open_file(struct kernfs_node *kn,
struct kernfs_open_file *of,
bool open_failed)
{
struct kernfs_open_node *on;
struct mutex *mutex;
mutex = kernfs_open_file_mutex_lock(kn);
on = kernfs_deref_open_node_locked(kn);
if (!on) {
mutex_unlock(mutex);
return;
}
if (of) {
if (kn->flags & KERNFS_HAS_RELEASE) {
WARN_ON_ONCE(of->released == open_failed);
if (open_failed)
on->nr_to_release--;
}
if (of->mmapped)
on->nr_mmapped--;
list_del(&of->list);
}
if (list_empty(&on->files)) {
rcu_assign_pointer(kn->attr.open, NULL);
kfree_rcu(on, rcu_head);
}
mutex_unlock(mutex);
}
static int kernfs_fop_open(struct inode *inode, struct file *file)
{
struct kernfs_node *kn = inode->i_private;
struct kernfs_root *root = kernfs_root(kn);
const struct kernfs_ops *ops;
struct kernfs_open_file *of;
bool has_read, has_write, has_mmap;
int error = -EACCES;
if (!kernfs_get_active(kn))
return -ENODEV;
ops = kernfs_ops(kn);
has_read = ops->seq_show || ops->read || ops->mmap;
has_write = ops->write || ops->mmap;
has_mmap = ops->mmap;
/* see the flag definition for details */
if (root->flags & KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK) {
if ((file->f_mode & FMODE_WRITE) &&
(!(inode->i_mode & S_IWUGO) || !has_write))
goto err_out;
if ((file->f_mode & FMODE_READ) &&
(!(inode->i_mode & S_IRUGO) || !has_read))
goto err_out;
}
/* allocate a kernfs_open_file for the file */
error = -ENOMEM;
of = kzalloc(sizeof(struct kernfs_open_file), GFP_KERNEL);
if (!of)
goto err_out;
/*
* The following is done to give a different lockdep key to
* @of->mutex for files which implement mmap. This is a rather
* crude way to avoid false positive lockdep warning around
* mm->mmap_lock - mmap nests @of->mutex under mm->mmap_lock and
* reading /sys/block/sda/trace/act_mask grabs sr_mutex, under
* which mm->mmap_lock nests, while holding @of->mutex. As each
* open file has a separate mutex, it's okay as long as those don't
* happen on the same file. At this point, we can't easily give
* each file a separate locking class. Let's differentiate on
* whether the file has mmap or not for now.
*
* For similar reasons, writable and readonly files are given different
* lockdep key, because the writable file /sys/power/resume may call vfs
* lookup helpers for arbitrary paths and readonly files can be read by
* overlayfs from vfs helpers when sysfs is a lower layer of overalyfs.
*
* All three cases look the same. They're supposed to
* look that way and give @of->mutex different static lockdep keys.
*/
if (has_mmap)
mutex_init(&of->mutex);
else if (file->f_mode & FMODE_WRITE)
mutex_init(&of->mutex);
else
mutex_init(&of->mutex);
of->kn = kn;
of->file = file;
/*
* Write path needs to atomic_write_len outside active reference.
* Cache it in open_file. See kernfs_fop_write_iter() for details.
*/
of->atomic_write_len = ops->atomic_write_len;
error = -EINVAL;
/*
* ->seq_show is incompatible with ->prealloc,
* as seq_read does its own allocation.
* ->read must be used instead.
*/
if (ops->prealloc && ops->seq_show)
goto err_free;
if (ops->prealloc) {
int len = of->atomic_write_len ?: PAGE_SIZE;
of->prealloc_buf = kmalloc(len + 1, GFP_KERNEL);
error = -ENOMEM;
if (!of->prealloc_buf)
goto err_free;
mutex_init(&of->prealloc_mutex);
}
/*
* Always instantiate seq_file even if read access doesn't use
* seq_file or is not requested. This unifies private data access
* and readable regular files are the vast majority anyway.
*/
if (ops->seq_show)
error = seq_open(file, &kernfs_seq_ops);
else
error = seq_open(file, NULL);
if (error)
goto err_free;
of->seq_file = file->private_data;
of->seq_file->private = of;
/* seq_file clears PWRITE unconditionally, restore it if WRITE */
if (file->f_mode & FMODE_WRITE)
file->f_mode |= FMODE_PWRITE;
/* make sure we have open node struct */
error = kernfs_get_open_node(kn, of);
if (error)
goto err_seq_release;
if (ops->open) {
/* nobody has access to @of yet, skip @of->mutex */
error = ops->open(of);
if (error)
goto err_put_node;
}
/* open succeeded, put active references */
kernfs_put_active(kn);
return 0;
err_put_node:
kernfs_unlink_open_file(kn, of, true);
err_seq_release:
seq_release(inode, file);
err_free:
kfree(of->prealloc_buf);
kfree(of);
err_out:
kernfs_put_active(kn);
return error;
}
/* used from release/drain to ensure that ->release() is called exactly once */
static void kernfs_release_file(struct kernfs_node *kn,
struct kernfs_open_file *of)
{
/*
* @of is guaranteed to have no other file operations in flight and
* we just want to synchronize release and drain paths.
* @kernfs_open_file_mutex_ptr(kn) is enough. @of->mutex can't be used
* here because drain path may be called from places which can
* cause circular dependency.
*/
lockdep_assert_held(kernfs_open_file_mutex_ptr(kn));
if (!of->released) {
/*
* A file is never detached without being released and we
* need to be able to release files which are deactivated
* and being drained. Don't use kernfs_ops().
*/
kn->attr.ops->release(of);
of->released = true;
of_on(of)->nr_to_release--;
}
}
static int kernfs_fop_release(struct inode *inode, struct file *filp)
{
struct kernfs_node *kn = inode->i_private;
struct kernfs_open_file *of = kernfs_of(filp);
if (kn->flags & KERNFS_HAS_RELEASE) {
struct mutex *mutex;
mutex = kernfs_open_file_mutex_lock(kn);
kernfs_release_file(kn, of);
mutex_unlock(mutex);
}
kernfs_unlink_open_file(kn, of, false);
seq_release(inode, filp);
kfree(of->prealloc_buf);
kfree(of);
return 0;
}
bool kernfs_should_drain_open_files(struct kernfs_node *kn)
{
struct kernfs_open_node *on;
bool ret;
/*
* @kn being deactivated guarantees that @kn->attr.open can't change
* beneath us making the lockless test below safe.
*/
WARN_ON_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS);
rcu_read_lock();
on = rcu_dereference(kn->attr.open);
ret = on && (on->nr_mmapped || on->nr_to_release);
rcu_read_unlock();
return ret;
}
void kernfs_drain_open_files(struct kernfs_node *kn)
{
struct kernfs_open_node *on;
struct kernfs_open_file *of;
struct mutex *mutex;
mutex = kernfs_open_file_mutex_lock(kn);
on = kernfs_deref_open_node_locked(kn);
if (!on) {
mutex_unlock(mutex);
return;
}
list_for_each_entry(of, &on->files, list) {
struct inode *inode = file_inode(of->file);
if (of->mmapped) {
unmap_mapping_range(inode->i_mapping, 0, 0, 1);
of->mmapped = false;
on->nr_mmapped--;
}
if (kn->flags & KERNFS_HAS_RELEASE)
kernfs_release_file(kn, of);
}
WARN_ON_ONCE(on->nr_mmapped || on->nr_to_release);
mutex_unlock(mutex);
}
/*
* Kernfs attribute files are pollable. The idea is that you read
* the content and then you use 'poll' or 'select' to wait for
* the content to change. When the content changes (assuming the
* manager for the kobject supports notification), poll will
* return EPOLLERR|EPOLLPRI, and select will return the fd whether
* it is waiting for read, write, or exceptions.
* Once poll/select indicates that the value has changed, you
* need to close and re-open the file, or seek to 0 and read again.
* Reminder: this only works for attributes which actively support
* it, and it is not possible to test an attribute from userspace
* to see if it supports poll (Neither 'poll' nor 'select' return
* an appropriate error code). When in doubt, set a suitable timeout value.
*/
__poll_t kernfs_generic_poll(struct kernfs_open_file *of, poll_table *wait)
{
struct kernfs_open_node *on = of_on(of);
poll_wait(of->file, &on->poll, wait);
if (of->event != atomic_read(&on->event))
return DEFAULT_POLLMASK|EPOLLERR|EPOLLPRI;
return DEFAULT_POLLMASK;
}
static __poll_t kernfs_fop_poll(struct file *filp, poll_table *wait)
{
struct kernfs_open_file *of = kernfs_of(filp);
struct kernfs_node *kn = kernfs_dentry_node(filp->f_path.dentry);
__poll_t ret;
if (!kernfs_get_active(kn))
return DEFAULT_POLLMASK|EPOLLERR|EPOLLPRI;
if (kn->attr.ops->poll)
ret = kn->attr.ops->poll(of, wait);
else
ret = kernfs_generic_poll(of, wait);
kernfs_put_active(kn);
return ret;
}
static loff_t kernfs_fop_llseek(struct file *file, loff_t offset, int whence)
{
struct kernfs_open_file *of = kernfs_of(file);
const struct kernfs_ops *ops;
loff_t ret;
/*
* @of->mutex nests outside active ref and is primarily to ensure that
* the ops aren't called concurrently for the same open file.
*/
mutex_lock(&of->mutex);
if (!kernfs_get_active(of->kn)) {
mutex_unlock(&of->mutex);
return -ENODEV;
}
ops = kernfs_ops(of->kn);
if (ops->llseek)
ret = ops->llseek(of, offset, whence);
else
ret = generic_file_llseek(file, offset, whence);
kernfs_put_active(of->kn);
mutex_unlock(&of->mutex);
return ret;
}
static void kernfs_notify_workfn(struct work_struct *work)
{
struct kernfs_node *kn;
struct kernfs_super_info *info;
struct kernfs_root *root;
repeat:
/* pop one off the notify_list */
spin_lock_irq(&kernfs_notify_lock);
kn = kernfs_notify_list;
if (kn == KERNFS_NOTIFY_EOL) {
spin_unlock_irq(&kernfs_notify_lock);
return;
}
kernfs_notify_list = kn->attr.notify_next;
kn->attr.notify_next = NULL;
spin_unlock_irq(&kernfs_notify_lock);
root = kernfs_root(kn);
/* kick fsnotify */
down_read(&root->kernfs_supers_rwsem);
list_for_each_entry(info, &kernfs_root(kn)->supers, node) {
struct kernfs_node *parent;
struct inode *p_inode = NULL;
struct inode *inode;
struct qstr name;
/*
* We want fsnotify_modify() on @kn but as the
* modifications aren't originating from userland don't
* have the matching @file available. Look up the inodes
* and generate the events manually.
*/
inode = ilookup(info->sb, kernfs_ino(kn));
if (!inode)
continue;
name = (struct qstr)QSTR_INIT(kn->name, strlen(kn->name));
parent = kernfs_get_parent(kn);
if (parent) {
p_inode = ilookup(info->sb, kernfs_ino(parent));
if (p_inode) {
fsnotify(FS_MODIFY | FS_EVENT_ON_CHILD,
inode, FSNOTIFY_EVENT_INODE,
p_inode, &name, inode, 0);
iput(p_inode);
}
kernfs_put(parent);
}
if (!p_inode)
fsnotify_inode(inode, FS_MODIFY);
iput(inode);
}
up_read(&root->kernfs_supers_rwsem);
kernfs_put(kn);
goto repeat;
}
/**
* kernfs_notify - notify a kernfs file
* @kn: file to notify
*
* Notify @kn such that poll(2) on @kn wakes up. Maybe be called from any
* context.
*/
void kernfs_notify(struct kernfs_node *kn)
{
static DECLARE_WORK(kernfs_notify_work, kernfs_notify_workfn);
unsigned long flags;
struct kernfs_open_node *on;
if (WARN_ON(kernfs_type(kn) != KERNFS_FILE))
return;
/* kick poll immediately */
rcu_read_lock();
on = rcu_dereference(kn->attr.open);
if (on) {
atomic_inc(&on->event);
wake_up_interruptible(&on->poll);
}
rcu_read_unlock();
/* schedule work to kick fsnotify */
spin_lock_irqsave(&kernfs_notify_lock, flags);
if (!kn->attr.notify_next) {
kernfs_get(kn);
kn->attr.notify_next = kernfs_notify_list;
kernfs_notify_list = kn;
schedule_work(&kernfs_notify_work);
}
spin_unlock_irqrestore(&kernfs_notify_lock, flags);
}
EXPORT_SYMBOL_GPL(kernfs_notify);
const struct file_operations kernfs_file_fops = {
.read_iter = kernfs_fop_read_iter,
.write_iter = kernfs_fop_write_iter,
.llseek = kernfs_fop_llseek,
.mmap = kernfs_fop_mmap,
.open = kernfs_fop_open,
.release = kernfs_fop_release,
.poll = kernfs_fop_poll,
.fsync = noop_fsync,
.splice_read = copy_splice_read,
.splice_write = iter_file_splice_write,
};
/**
* __kernfs_create_file - kernfs internal function to create a file
* @parent: directory to create the file in
* @name: name of the file
* @mode: mode of the file
* @uid: uid of the file
* @gid: gid of the file
* @size: size of the file
* @ops: kernfs operations for the file
* @priv: private data for the file
* @ns: optional namespace tag of the file
* @key: lockdep key for the file's active_ref, %NULL to disable lockdep
*
* Return: the created node on success, ERR_PTR() value on error.
*/
struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
const char *name,
umode_t mode, kuid_t uid, kgid_t gid,
loff_t size,
const struct kernfs_ops *ops,
void *priv, const void *ns,
struct lock_class_key *key)
{
struct kernfs_node *kn;
unsigned flags;
int rc;
flags = KERNFS_FILE;
kn = kernfs_new_node(parent, name, (mode & S_IALLUGO) | S_IFREG,
uid, gid, flags);
if (!kn)
return ERR_PTR(-ENOMEM);
kn->attr.ops = ops;
kn->attr.size = size;
kn->ns = ns;
kn->priv = priv;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
if (key) {
lockdep_init_map(&kn->dep_map, "kn->active", key, 0);
kn->flags |= KERNFS_LOCKDEP;
}
#endif
/*
* kn->attr.ops is accessible only while holding active ref. We
* need to know whether some ops are implemented outside active
* ref. Cache their existence in flags.
*/
if (ops->seq_show)
kn->flags |= KERNFS_HAS_SEQ_SHOW;
if (ops->mmap)
kn->flags |= KERNFS_HAS_MMAP;
if (ops->release)
kn->flags |= KERNFS_HAS_RELEASE;
rc = kernfs_add_one(kn);
if (rc) {
kernfs_put(kn);
return ERR_PTR(rc);
}
return kn;
}
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