[karo-tx-linux.git] / fs / sysfs / file.c

/*
 * fs/sysfs/file.c - sysfs regular (text) file implementation
 *
 * Copyright (c) 2001-3 Patrick Mochel
 * Copyright (c) 2007 SUSE Linux Products GmbH
 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
 *
 * This file is released under the GPLv2.
 *
 * Please see Documentation/filesystems/sysfs.txt for more information.
 */

#include <linux/module.h>
#include <linux/kobject.h>
#include <linux/kallsyms.h>
#include <linux/slab.h>
#include <linux/fsnotify.h>
#include <linux/namei.h>
#include <linux/poll.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/limits.h>
#include <linux/uaccess.h>
#include <linux/seq_file.h>
#include <linux/mm.h>

#include "sysfs.h"

/*
 * There's one sysfs_open_file for each open file and one sysfs_open_dirent
 * for each sysfs_dirent with one or more open files.
 *
 * sysfs_dirent->s_attr.open points to sysfs_open_dirent.  s_attr.open is
 * protected by sysfs_open_dirent_lock.
 *
 * filp->private_data points to seq_file whose ->private points to
 * sysfs_open_file.  sysfs_open_files are chained at
 * sysfs_open_dirent->files, which is protected by sysfs_open_file_mutex.
 */
static DEFINE_SPINLOCK(sysfs_open_dirent_lock);
static DEFINE_MUTEX(sysfs_open_file_mutex);

struct sysfs_open_dirent {
        atomic_t                refcnt;
        atomic_t                event;
        wait_queue_head_t       poll;
        struct list_head        files; /* goes through sysfs_open_file.list */
};

static struct sysfs_open_file *sysfs_of(struct file *file)
{
        return ((struct seq_file *)file->private_data)->private;
}

/*
 * Determine the kernfs_ops for the given sysfs_dirent.  This function must
 * be called while holding an active reference.
 */
static const struct kernfs_ops *kernfs_ops(struct sysfs_dirent *sd)
{
        if (!sysfs_ignore_lockdep(sd))
                lockdep_assert_held(sd);
        return sd->s_attr.ops;
}

/*
 * Determine ktype->sysfs_ops for the given sysfs_dirent.  This function
 * must be called while holding an active reference.
 */
static const struct sysfs_ops *sysfs_file_ops(struct sysfs_dirent *sd)
{
        struct kobject *kobj = sd->s_parent->priv;

        if (!sysfs_ignore_lockdep(sd))
                lockdep_assert_held(sd);
        return kobj->ktype ? kobj->ktype->sysfs_ops : NULL;
}

/*
 * Reads on sysfs are handled through seq_file, which takes care of hairy
 * details like buffering and seeking.  The following function pipes
 * sysfs_ops->show() result through seq_file.
 */
static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
{
        struct sysfs_open_file *of = sf->private;
        struct kobject *kobj = of->sd->s_parent->priv;
        const struct sysfs_ops *ops = sysfs_file_ops(of->sd);
        ssize_t count;
        char *buf;

        /* acquire buffer and ensure that it's >= PAGE_SIZE */
        count = seq_get_buf(sf, &buf);
        if (count < PAGE_SIZE) {
                seq_commit(sf, -1);
                return 0;
        }

        /*
         * Invoke show().  Control may reach here via seq file lseek even
         * if @ops->show() isn't implemented.
         */
        if (ops->show) {
                count = ops->show(kobj, of->sd->priv, buf);
                if (count < 0)
                        return count;
        }

        /*
         * The code works fine with PAGE_SIZE return but it's likely to
         * indicate truncated result or overflow in normal use cases.
         */
        if (count >= (ssize_t)PAGE_SIZE) {
                print_symbol("fill_read_buffer: %s returned bad count\n",
                        (unsigned long)ops->show);
                /* Try to struggle along */
                count = PAGE_SIZE - 1;
        }
        seq_commit(sf, count);
        return 0;
}

static ssize_t sysfs_kf_bin_read(struct sysfs_open_file *of, char *buf,
                                 size_t count, loff_t pos)
{
        struct bin_attribute *battr = of->sd->priv;
        struct kobject *kobj = of->sd->s_parent->priv;
        loff_t size = file_inode(of->file)->i_size;

        if (!count)
                return 0;

        if (size) {
                if (pos > size)
                        return 0;
                if (pos + count > size)
                        count = size - pos;
        }

        if (!battr->read)
                return -EIO;

        return battr->read(of->file, kobj, battr, buf, pos, count);
}

static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
{
        struct sysfs_open_file *of = sf->private;
        const struct kernfs_ops *ops;

        /*
         * @of->mutex nests outside active ref and is just to ensure that
         * the ops aren't called concurrently for the same open file.
         */
        mutex_lock(&of->mutex);
        if (!sysfs_get_active(of->sd))
                return ERR_PTR(-ENODEV);

        ops = kernfs_ops(of->sd);
        if (ops->seq_start) {
                return ops->seq_start(sf, ppos);
        } else {
                /*
                 * The same behavior and code as single_open().  Returns
                 * !NULL if pos is at the beginning; otherwise, NULL.
                 */
                return NULL + !*ppos;
        }
}

static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos)
{
        struct sysfs_open_file *of = sf->private;
        const struct kernfs_ops *ops = kernfs_ops(of->sd);

        if (ops->seq_next) {
                return ops->seq_next(sf, v, ppos);
        } 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 sysfs_open_file *of = sf->private;
        const struct kernfs_ops *ops = kernfs_ops(of->sd);

        if (ops->seq_stop)
                ops->seq_stop(sf, v);

        sysfs_put_active(of->sd);
        mutex_unlock(&of->mutex);
}

static int kernfs_seq_show(struct seq_file *sf, void *v)
{
        struct sysfs_open_file *of = sf->private;

        of->event = atomic_read(&of->sd->s_attr.open->event);

        return of->sd->s_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_direct_read(struct sysfs_open_file *of,
                                       char __user *user_buf, size_t count,
                                       loff_t *ppos)
{
        ssize_t len = min_t(size_t, count, PAGE_SIZE);
        const struct kernfs_ops *ops;
        char *buf;

        buf = kmalloc(len, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        /*
         * @of->mutex nests outside active ref and is just to ensure that
         * the ops aren't called concurrently for the same open file.
         */
        mutex_lock(&of->mutex);
        if (!sysfs_get_active(of->sd)) {
                len = -ENODEV;
                mutex_unlock(&of->mutex);
                goto out_free;
        }

        ops = kernfs_ops(of->sd);
        if (ops->read)
                len = ops->read(of, buf, len, *ppos);
        else
                len = -EINVAL;

        sysfs_put_active(of->sd);
        mutex_unlock(&of->mutex);

        if (len < 0)
                goto out_free;

        if (copy_to_user(user_buf, buf, len)) {
                len = -EFAULT;
                goto out_free;
        }

        *ppos += len;

 out_free:
        kfree(buf);
        return len;
}

/**
 * kernfs_file_read - kernfs vfs read callback
 * @file: file pointer
 * @user_buf: data to write
 * @count: number of bytes
 * @ppos: starting offset
 */
static ssize_t kernfs_file_read(struct file *file, char __user *user_buf,
                                size_t count, loff_t *ppos)
{
        struct sysfs_open_file *of = sysfs_of(file);

        if (of->sd->s_flags & SYSFS_FLAG_HAS_SEQ_SHOW)
                return seq_read(file, user_buf, count, ppos);
        else
                return kernfs_file_direct_read(of, user_buf, count, ppos);
}

/* kernfs write callback for regular sysfs files */
static ssize_t sysfs_kf_write(struct sysfs_open_file *of, char *buf,
                              size_t count, loff_t pos)
{
        const struct sysfs_ops *ops = sysfs_file_ops(of->sd);
        struct kobject *kobj = of->sd->s_parent->priv;

        if (!count)
                return 0;

        return ops->store(kobj, of->sd->priv, buf, count);
}

/* kernfs write callback for bin sysfs files */
static ssize_t sysfs_kf_bin_write(struct sysfs_open_file *of, char *buf,
                                  size_t count, loff_t pos)
{
        struct bin_attribute *battr = of->sd->priv;
        struct kobject *kobj = of->sd->s_parent->priv;
        loff_t size = file_inode(of->file)->i_size;

        if (size) {
                if (size <= pos)
                        return 0;
                count = min_t(ssize_t, count, size - pos);
        }
        if (!count)
                return 0;

        if (!battr->write)
                return -EIO;

        return battr->write(of->file, kobj, battr, buf, pos, count);
}

/**
 * kernfs_file_write - kernfs vfs write callback
 * @file: file pointer
 * @user_buf: data to write
 * @count: number of bytes
 * @ppos: starting offset
 *
 * 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 the value you're changing, then write entire buffer
 * back.
 */
static ssize_t kernfs_file_write(struct file *file, const char __user *user_buf,
                                 size_t count, loff_t *ppos)
{
        struct sysfs_open_file *of = sysfs_of(file);
        ssize_t len = min_t(size_t, count, PAGE_SIZE);
        const struct kernfs_ops *ops;
        char *buf;

        buf = kmalloc(len + 1, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        if (copy_from_user(buf, user_buf, len)) {
                len = -EFAULT;
                goto out_free;
        }
        buf[len] = '\0';        /* guarantee string termination */

        /*
         * @of->mutex nests outside active ref and is just to ensure that
         * the ops aren't called concurrently for the same open file.
         */
        mutex_lock(&of->mutex);
        if (!sysfs_get_active(of->sd)) {
                mutex_unlock(&of->mutex);
                len = -ENODEV;
                goto out_free;
        }

        ops = kernfs_ops(of->sd);
        if (ops->write)
                len = ops->write(of, buf, len, *ppos);
        else
                len = -EINVAL;

        sysfs_put_active(of->sd);
        mutex_unlock(&of->mutex);

        if (len > 0)
                *ppos += len;
out_free:
        kfree(buf);
        return len;
}

static int sysfs_kf_bin_mmap(struct sysfs_open_file *of,
                             struct vm_area_struct *vma)
{
        struct bin_attribute *battr = of->sd->priv;
        struct kobject *kobj = of->sd->s_parent->priv;

        if (!battr->mmap)
                return -ENODEV;

        return battr->mmap(of->file, kobj, battr, vma);
}

static void kernfs_vma_open(struct vm_area_struct *vma)
{
        struct file *file = vma->vm_file;
        struct sysfs_open_file *of = sysfs_of(file);

        if (!of->vm_ops)
                return;

        if (!sysfs_get_active(of->sd))
                return;

        if (of->vm_ops->open)
                of->vm_ops->open(vma);

        sysfs_put_active(of->sd);
}

static int kernfs_vma_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
        struct file *file = vma->vm_file;
        struct sysfs_open_file *of = sysfs_of(file);
        int ret;

        if (!of->vm_ops)
                return VM_FAULT_SIGBUS;

        if (!sysfs_get_active(of->sd))
                return VM_FAULT_SIGBUS;

        ret = VM_FAULT_SIGBUS;
        if (of->vm_ops->fault)
                ret = of->vm_ops->fault(vma, vmf);

        sysfs_put_active(of->sd);
        return ret;
}

static int kernfs_vma_page_mkwrite(struct vm_area_struct *vma,
                                   struct vm_fault *vmf)
{
        struct file *file = vma->vm_file;
        struct sysfs_open_file *of = sysfs_of(file);
        int ret;

        if (!of->vm_ops)
                return VM_FAULT_SIGBUS;

        if (!sysfs_get_active(of->sd))
                return VM_FAULT_SIGBUS;

        ret = 0;
        if (of->vm_ops->page_mkwrite)
                ret = of->vm_ops->page_mkwrite(vma, vmf);
        else
                file_update_time(file);

        sysfs_put_active(of->sd);
        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 sysfs_open_file *of = sysfs_of(file);
        int ret;

        if (!of->vm_ops)
                return -EINVAL;

        if (!sysfs_get_active(of->sd))
                return -EINVAL;

        ret = -EINVAL;
        if (of->vm_ops->access)
                ret = of->vm_ops->access(vma, addr, buf, len, write);

        sysfs_put_active(of->sd);
        return ret;
}

#ifdef CONFIG_NUMA
static int kernfs_vma_set_policy(struct vm_area_struct *vma,
                                 struct mempolicy *new)
{
        struct file *file = vma->vm_file;
        struct sysfs_open_file *of = sysfs_of(file);
        int ret;

        if (!of->vm_ops)
                return 0;

        if (!sysfs_get_active(of->sd))
                return -EINVAL;

        ret = 0;
        if (of->vm_ops->set_policy)
                ret = of->vm_ops->set_policy(vma, new);

        sysfs_put_active(of->sd);
        return ret;
}

static struct mempolicy *kernfs_vma_get_policy(struct vm_area_struct *vma,
                                               unsigned long addr)
{
        struct file *file = vma->vm_file;
        struct sysfs_open_file *of = sysfs_of(file);
        struct mempolicy *pol;

        if (!of->vm_ops)
                return vma->vm_policy;

        if (!sysfs_get_active(of->sd))
                return vma->vm_policy;

        pol = vma->vm_policy;
        if (of->vm_ops->get_policy)
                pol = of->vm_ops->get_policy(vma, addr);

        sysfs_put_active(of->sd);
        return pol;
}

static int kernfs_vma_migrate(struct vm_area_struct *vma,
                              const nodemask_t *from, const nodemask_t *to,
                              unsigned long flags)
{
        struct file *file = vma->vm_file;
        struct sysfs_open_file *of = sysfs_of(file);
        int ret;

        if (!of->vm_ops)
                return 0;

        if (!sysfs_get_active(of->sd))
                return 0;

        ret = 0;
        if (of->vm_ops->migrate)
                ret = of->vm_ops->migrate(vma, from, to, flags);

        sysfs_put_active(of->sd);
        return ret;
}
#endif

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,
#ifdef CONFIG_NUMA
        .set_policy     = kernfs_vma_set_policy,
        .get_policy     = kernfs_vma_get_policy,
        .migrate        = kernfs_vma_migrate,
#endif
};

static int kernfs_file_mmap(struct file *file, struct vm_area_struct *vma)
{
        struct sysfs_open_file *of = sysfs_of(file);
        const struct kernfs_ops *ops;
        int rc;

        mutex_lock(&of->mutex);

        rc = -ENODEV;
        if (!sysfs_get_active(of->sd))
                goto out_unlock;

        ops = kernfs_ops(of->sd);
        if (ops->mmap)
                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.
         */
        rc = -EINVAL;
        if (vma->vm_ops && vma->vm_ops->close)
                goto out_put;

        rc = 0;
        of->mmapped = 1;
        of->vm_ops = vma->vm_ops;
        vma->vm_ops = &kernfs_vm_ops;
out_put:
        sysfs_put_active(of->sd);
out_unlock:
        mutex_unlock(&of->mutex);

        return rc;
}

/**
 *      sysfs_get_open_dirent - get or create sysfs_open_dirent
 *      @sd: target sysfs_dirent
 *      @of: sysfs_open_file for this instance of open
 *
 *      If @sd->s_attr.open exists, increment its reference count;
 *      otherwise, create one.  @of is chained to the files list.
 *
 *      LOCKING:
 *      Kernel thread context (may sleep).
 *
 *      RETURNS:
 *      0 on success, -errno on failure.
 */
static int sysfs_get_open_dirent(struct sysfs_dirent *sd,
                                 struct sysfs_open_file *of)
{
        struct sysfs_open_dirent *od, *new_od = NULL;

 retry:
        mutex_lock(&sysfs_open_file_mutex);
        spin_lock_irq(&sysfs_open_dirent_lock);

        if (!sd->s_attr.open && new_od) {
                sd->s_attr.open = new_od;
                new_od = NULL;
        }

        od = sd->s_attr.open;
        if (od) {
                atomic_inc(&od->refcnt);
                list_add_tail(&of->list, &od->files);
        }

        spin_unlock_irq(&sysfs_open_dirent_lock);
        mutex_unlock(&sysfs_open_file_mutex);

        if (od) {
                kfree(new_od);
                return 0;
        }

        /* not there, initialize a new one and retry */
        new_od = kmalloc(sizeof(*new_od), GFP_KERNEL);
        if (!new_od)
                return -ENOMEM;

        atomic_set(&new_od->refcnt, 0);
        atomic_set(&new_od->event, 1);
        init_waitqueue_head(&new_od->poll);
        INIT_LIST_HEAD(&new_od->files);
        goto retry;
}

/**
 *      sysfs_put_open_dirent - put sysfs_open_dirent
 *      @sd: target sysfs_dirent
 *      @of: associated sysfs_open_file
 *
 *      Put @sd->s_attr.open and unlink @of from the files list.  If
 *      reference count reaches zero, disassociate and free it.
 *
 *      LOCKING:
 *      None.
 */
static void sysfs_put_open_dirent(struct sysfs_dirent *sd,
                                  struct sysfs_open_file *of)
{
        struct sysfs_open_dirent *od = sd->s_attr.open;
        unsigned long flags;

        mutex_lock(&sysfs_open_file_mutex);
        spin_lock_irqsave(&sysfs_open_dirent_lock, flags);

        if (of)
                list_del(&of->list);

        if (atomic_dec_and_test(&od->refcnt))
                sd->s_attr.open = NULL;
        else
                od = NULL;

        spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags);
        mutex_unlock(&sysfs_open_file_mutex);

        kfree(od);
}

static int kernfs_file_open(struct inode *inode, struct file *file)
{
        struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
        const struct kernfs_ops *ops;
        struct sysfs_open_file *of;
        bool has_read, has_write, has_mmap;
        int error = -EACCES;

        if (!sysfs_get_active(attr_sd))
                return -ENODEV;

        ops = kernfs_ops(attr_sd);

        has_read = ops->seq_show || ops->read || ops->mmap;
        has_write = ops->write || ops->mmap;
        has_mmap = ops->mmap;

        /* check perms and supported operations */
        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 sysfs_open_file for the file */
        error = -ENOMEM;
        of = kzalloc(sizeof(struct sysfs_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_sem - mmap nests @of->mutex under mm->mmap_sem and
         * reading /sys/block/sda/trace/act_mask grabs sr_mutex, under
         * which mm->mmap_sem 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.
         */
        if (has_mmap)
                mutex_init(&of->mutex);
        else
                mutex_init(&of->mutex);

        of->sd = attr_sd;
        of->file = file;

        /*
         * 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;

        ((struct seq_file *)file->private_data)->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 dirent struct */
        error = sysfs_get_open_dirent(attr_sd, of);
        if (error)
                goto err_close;

        /* open succeeded, put active references */
        sysfs_put_active(attr_sd);
        return 0;

err_close:
        seq_release(inode, file);
err_free:
        kfree(of);
err_out:
        sysfs_put_active(attr_sd);
        return error;
}

static int kernfs_file_release(struct inode *inode, struct file *filp)
{
        struct sysfs_dirent *sd = filp->f_path.dentry->d_fsdata;
        struct sysfs_open_file *of = sysfs_of(filp);

        sysfs_put_open_dirent(sd, of);
        seq_release(inode, filp);
        kfree(of);

        return 0;
}

void sysfs_unmap_bin_file(struct sysfs_dirent *sd)
{
        struct sysfs_open_dirent *od;
        struct sysfs_open_file *of;

        if (!(sd->s_flags & SYSFS_FLAG_HAS_MMAP))
                return;

        spin_lock_irq(&sysfs_open_dirent_lock);
        od = sd->s_attr.open;
        if (od)
                atomic_inc(&od->refcnt);
        spin_unlock_irq(&sysfs_open_dirent_lock);
        if (!od)
                return;

        mutex_lock(&sysfs_open_file_mutex);
        list_for_each_entry(of, &od->files, list) {
                struct inode *inode = file_inode(of->file);
                unmap_mapping_range(inode->i_mapping, 0, 0, 1);
        }
        mutex_unlock(&sysfs_open_file_mutex);

        sysfs_put_open_dirent(sd, NULL);
}

/* Sysfs 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 POLLERR|POLLPRI, 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.
 */
static unsigned int kernfs_file_poll(struct file *filp, poll_table *wait)
{
        struct sysfs_open_file *of = sysfs_of(filp);
        struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata;
        struct sysfs_open_dirent *od = attr_sd->s_attr.open;

        /* need parent for the kobj, grab both */
        if (!sysfs_get_active(attr_sd))
                goto trigger;

        poll_wait(filp, &od->poll, wait);

        sysfs_put_active(attr_sd);

        if (of->event != atomic_read(&od->event))
                goto trigger;

        return DEFAULT_POLLMASK;

 trigger:
        return DEFAULT_POLLMASK|POLLERR|POLLPRI;
}

/**
 * kernfs_notify - notify a kernfs file
 * @sd: file to notify
 *
 * Notify @sd such that poll(2) on @sd wakes up.
 */
void kernfs_notify(struct sysfs_dirent *sd)
{
        struct sysfs_open_dirent *od;
        unsigned long flags;

        spin_lock_irqsave(&sysfs_open_dirent_lock, flags);

        if (!WARN_ON(sysfs_type(sd) != SYSFS_KOBJ_ATTR)) {
                od = sd->s_attr.open;
                if (od) {
                        atomic_inc(&od->event);
                        wake_up_interruptible(&od->poll);
                }
        }

        spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags);
}
EXPORT_SYMBOL_GPL(kernfs_notify);

void sysfs_notify(struct kobject *k, const char *dir, const char *attr)
{
        struct sysfs_dirent *sd = k->sd, *tmp;

        if (sd && dir)
                sd = sysfs_get_dirent(sd, dir);
        else
                sysfs_get(sd);

        if (sd && attr) {
                tmp = sysfs_get_dirent(sd, attr);
                sysfs_put(sd);
                sd = tmp;
        }

        if (sd) {
                kernfs_notify(sd);
                sysfs_put(sd);
        }
}
EXPORT_SYMBOL_GPL(sysfs_notify);

const struct file_operations kernfs_file_operations = {
        .read           = kernfs_file_read,
        .write          = kernfs_file_write,
        .llseek         = generic_file_llseek,
        .mmap           = kernfs_file_mmap,
        .open           = kernfs_file_open,
        .release        = kernfs_file_release,
        .poll           = kernfs_file_poll,
};

static const struct kernfs_ops sysfs_file_kfops_empty = {
};

static const struct kernfs_ops sysfs_file_kfops_ro = {
        .seq_show       = sysfs_kf_seq_show,
};

static const struct kernfs_ops sysfs_file_kfops_wo = {
        .write          = sysfs_kf_write,
};

static const struct kernfs_ops sysfs_file_kfops_rw = {
        .seq_show       = sysfs_kf_seq_show,
        .write          = sysfs_kf_write,
};

static const struct kernfs_ops sysfs_bin_kfops_ro = {
        .read           = sysfs_kf_bin_read,
};

static const struct kernfs_ops sysfs_bin_kfops_wo = {
        .write          = sysfs_kf_bin_write,
};

static const struct kernfs_ops sysfs_bin_kfops_rw = {
        .read           = sysfs_kf_bin_read,
        .write          = sysfs_kf_bin_write,
        .mmap           = sysfs_kf_bin_mmap,
};

int sysfs_add_file_mode_ns(struct sysfs_dirent *dir_sd,
                           const struct attribute *attr, bool is_bin,
                           umode_t mode, const void *ns)
{
        const struct kernfs_ops *ops;
        struct sysfs_dirent *sd;
        loff_t size;

        if (!is_bin) {
                struct kobject *kobj = dir_sd->priv;
                const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;

                /* every kobject with an attribute needs a ktype assigned */
                if (WARN(!sysfs_ops, KERN_ERR
                         "missing sysfs attribute operations for kobject: %s\n",
                         kobject_name(kobj)))
                        return -EINVAL;

                if (sysfs_ops->show && sysfs_ops->store)
                        ops = &sysfs_file_kfops_rw;
                else if (sysfs_ops->show)
                        ops = &sysfs_file_kfops_ro;
                else if (sysfs_ops->store)
                        ops = &sysfs_file_kfops_wo;
                else
                        ops = &sysfs_file_kfops_empty;

                size = PAGE_SIZE;
        } else {
                struct bin_attribute *battr = (void *)attr;

                if ((battr->read && battr->write) || battr->mmap)
                        ops = &sysfs_bin_kfops_rw;
                else if (battr->read)
                        ops = &sysfs_bin_kfops_ro;
                else if (battr->write)
                        ops = &sysfs_bin_kfops_wo;
                else
                        ops = &sysfs_file_kfops_empty;

                size = battr->size;
        }

        sd = kernfs_create_file_ns(dir_sd, attr->name, mode, size,
                                   ops, (void *)attr, ns);
        if (IS_ERR(sd)) {
                if (PTR_ERR(sd) == -EEXIST)
                        sysfs_warn_dup(dir_sd, attr->name);
                return PTR_ERR(sd);
        }
        return 0;
}

/**
 * kernfs_create_file_ns - create a file
 * @parent: directory to create the file in
 * @name: name of the file
 * @mode: mode 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
 *
 * Returns the created node on success, ERR_PTR() value on error.
 */
struct sysfs_dirent *kernfs_create_file_ns(struct sysfs_dirent *parent,
                                           const char *name,
                                           umode_t mode, loff_t size,
                                           const struct kernfs_ops *ops,
                                           void *priv, const void *ns)
{
        struct sysfs_addrm_cxt acxt;
        struct sysfs_dirent *sd;
        int rc;

        sd = sysfs_new_dirent(name, (mode & S_IALLUGO) | S_IFREG,
                              SYSFS_KOBJ_ATTR);
        if (!sd)
                return ERR_PTR(-ENOMEM);

        sd->s_attr.ops = ops;
        sd->s_attr.size = size;
        sd->s_ns = ns;
        sd->priv = priv;
        sysfs_dirent_init_lockdep(sd);

        /*
         * sd->s_attr.ops is accesible 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)
                sd->s_flags |= SYSFS_FLAG_HAS_SEQ_SHOW;
        if (ops->mmap)
                sd->s_flags |= SYSFS_FLAG_HAS_MMAP;

        sysfs_addrm_start(&acxt);
        rc = sysfs_add_one(&acxt, sd, parent);
        sysfs_addrm_finish(&acxt);

        if (rc) {
                sysfs_put(sd);
                return ERR_PTR(rc);
        }
        return sd;
}

int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,
                   bool is_bin)
{
        return sysfs_add_file_mode_ns(dir_sd, attr, is_bin, attr->mode, NULL);
}

/**
 * sysfs_create_file_ns - create an attribute file for an object with custom ns
 * @kobj: object we're creating for
 * @attr: attribute descriptor
 * @ns: namespace the new file should belong to
 */
int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
                         const void *ns)
{
        BUG_ON(!kobj || !kobj->sd || !attr);

        return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode, ns);

}
EXPORT_SYMBOL_GPL(sysfs_create_file_ns);

int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
{
        int err = 0;
        int i;

        for (i = 0; ptr[i] && !err; i++)
                err = sysfs_create_file(kobj, ptr[i]);
        if (err)
                while (--i >= 0)
                        sysfs_remove_file(kobj, ptr[i]);
        return err;
}
EXPORT_SYMBOL_GPL(sysfs_create_files);

/**
 * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
 * @kobj: object we're acting for.
 * @attr: attribute descriptor.
 * @group: group name.
 */
int sysfs_add_file_to_group(struct kobject *kobj,
                const struct attribute *attr, const char *group)
{
        struct sysfs_dirent *dir_sd;
        int error;

        if (group)
                dir_sd = sysfs_get_dirent(kobj->sd, group);
        else
                dir_sd = sysfs_get(kobj->sd);

        if (!dir_sd)
                return -ENOENT;

        error = sysfs_add_file(dir_sd, attr, false);
        sysfs_put(dir_sd);

        return error;
}
EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);

/**
 * sysfs_chmod_file - update the modified mode value on an object attribute.
 * @kobj: object we're acting for.
 * @attr: attribute descriptor.
 * @mode: file permissions.
 *
 */
int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
                     umode_t mode)
{
        struct sysfs_dirent *sd;
        struct iattr newattrs;
        int rc;

        sd = sysfs_get_dirent(kobj->sd, attr->name);
        if (!sd)
                return -ENOENT;

        newattrs.ia_mode = (mode & S_IALLUGO) | (sd->s_mode & ~S_IALLUGO);
        newattrs.ia_valid = ATTR_MODE;

        rc = kernfs_setattr(sd, &newattrs);

        sysfs_put(sd);
        return rc;
}
EXPORT_SYMBOL_GPL(sysfs_chmod_file);

/**
 * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
 * @kobj: object we're acting for
 * @attr: attribute descriptor
 * @ns: namespace tag of the file to remove
 *
 * Hash the attribute name and namespace tag and kill the victim.
 */
void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
                          const void *ns)
{
        struct sysfs_dirent *dir_sd = kobj->sd;

        kernfs_remove_by_name_ns(dir_sd, attr->name, ns);
}
EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);

void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
{
        int i;
        for (i = 0; ptr[i]; i++)
                sysfs_remove_file(kobj, ptr[i]);
}
EXPORT_SYMBOL_GPL(sysfs_remove_files);

/**
 * sysfs_remove_file_from_group - remove an attribute file from a group.
 * @kobj: object we're acting for.
 * @attr: attribute descriptor.
 * @group: group name.
 */
void sysfs_remove_file_from_group(struct kobject *kobj,
                const struct attribute *attr, const char *group)
{
        struct sysfs_dirent *dir_sd;

        if (group)
                dir_sd = sysfs_get_dirent(kobj->sd, group);
        else
                dir_sd = sysfs_get(kobj->sd);
        if (dir_sd) {
                kernfs_remove_by_name(dir_sd, attr->name);
                sysfs_put(dir_sd);
        }
}
EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);

/**
 *      sysfs_create_bin_file - create binary file for object.
 *      @kobj:  object.
 *      @attr:  attribute descriptor.
 */
int sysfs_create_bin_file(struct kobject *kobj,
                          const struct bin_attribute *attr)
{
        BUG_ON(!kobj || !kobj->sd || !attr);

        return sysfs_add_file(kobj->sd, &attr->attr, true);
}
EXPORT_SYMBOL_GPL(sysfs_create_bin_file);

/**
 *      sysfs_remove_bin_file - remove binary file for object.
 *      @kobj:  object.
 *      @attr:  attribute descriptor.
 */
void sysfs_remove_bin_file(struct kobject *kobj,
                           const struct bin_attribute *attr)
{
        kernfs_remove_by_name(kobj->sd, attr->attr.name);
}
EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);

struct sysfs_schedule_callback_struct {
        struct list_head        workq_list;
        struct kobject          *kobj;
        void                    (*func)(void *);
        void                    *data;
        struct module           *owner;
        struct work_struct      work;
};

static struct workqueue_struct *sysfs_workqueue;
static DEFINE_MUTEX(sysfs_workq_mutex);
static LIST_HEAD(sysfs_workq);
static void sysfs_schedule_callback_work(struct work_struct *work)
{
        struct sysfs_schedule_callback_struct *ss = container_of(work,
                        struct sysfs_schedule_callback_struct, work);

        (ss->func)(ss->data);
        kobject_put(ss->kobj);
        module_put(ss->owner);
        mutex_lock(&sysfs_workq_mutex);
        list_del(&ss->workq_list);
        mutex_unlock(&sysfs_workq_mutex);
        kfree(ss);
}

/**
 * sysfs_schedule_callback - helper to schedule a callback for a kobject
 * @kobj: object we're acting for.
 * @func: callback function to invoke later.
 * @data: argument to pass to @func.
 * @owner: module owning the callback code
 *
 * sysfs attribute methods must not unregister themselves or their parent
 * kobject (which would amount to the same thing).  Attempts to do so will
 * deadlock, since unregistration is mutually exclusive with driver
 * callbacks.
 *
 * Instead methods can call this routine, which will attempt to allocate
 * and schedule a workqueue request to call back @func with @data as its
 * argument in the workqueue's process context.  @kobj will be pinned
 * until @func returns.
 *
 * Returns 0 if the request was submitted, -ENOMEM if storage could not
 * be allocated, -ENODEV if a reference to @owner isn't available,
 * -EAGAIN if a callback has already been scheduled for @kobj.
 */
int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
                void *data, struct module *owner)
{
        struct sysfs_schedule_callback_struct *ss, *tmp;

        if (!try_module_get(owner))
                return -ENODEV;

        mutex_lock(&sysfs_workq_mutex);
        list_for_each_entry_safe(ss, tmp, &sysfs_workq, workq_list)
                if (ss->kobj == kobj) {
                        module_put(owner);
                        mutex_unlock(&sysfs_workq_mutex);
                        return -EAGAIN;
                }
        mutex_unlock(&sysfs_workq_mutex);

        if (sysfs_workqueue == NULL) {
                sysfs_workqueue = create_singlethread_workqueue("sysfsd");
                if (sysfs_workqueue == NULL) {
                        module_put(owner);
                        return -ENOMEM;
                }
        }

        ss = kmalloc(sizeof(*ss), GFP_KERNEL);
        if (!ss) {
                module_put(owner);
                return -ENOMEM;
        }
        kobject_get(kobj);
        ss->kobj = kobj;
        ss->func = func;
        ss->data = data;
        ss->owner = owner;
        INIT_WORK(&ss->work, sysfs_schedule_callback_work);
        INIT_LIST_HEAD(&ss->workq_list);
        mutex_lock(&sysfs_workq_mutex);
        list_add_tail(&ss->workq_list, &sysfs_workq);
        mutex_unlock(&sysfs_workq_mutex);
        queue_work(sysfs_workqueue, &ss->work);
        return 0;
}
EXPORT_SYMBOL_GPL(sysfs_schedule_callback);