linux/fs/sysfs/file.c
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   1/*
   2 * fs/sysfs/file.c - sysfs regular (text) file implementation
   3 *
   4 * Copyright (c) 2001-3 Patrick Mochel
   5 * Copyright (c) 2007 SUSE Linux Products GmbH
   6 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
   7 *
   8 * This file is released under the GPLv2.
   9 *
  10 * Please see Documentation/filesystems/sysfs.txt for more information.
  11 */
  12
  13#include <linux/module.h>
  14#include <linux/kobject.h>
  15#include <linux/kallsyms.h>
  16#include <linux/slab.h>
  17#include <linux/fsnotify.h>
  18#include <linux/namei.h>
  19#include <linux/poll.h>
  20#include <linux/list.h>
  21#include <linux/mutex.h>
  22#include <linux/limits.h>
  23#include <asm/uaccess.h>
  24
  25#include "sysfs.h"
  26
  27/*
  28 * There's one sysfs_buffer for each open file and one
  29 * sysfs_open_dirent for each sysfs_dirent with one or more open
  30 * files.
  31 *
  32 * filp->private_data points to sysfs_buffer and
  33 * sysfs_dirent->s_attr.open points to sysfs_open_dirent.  s_attr.open
  34 * is protected by sysfs_open_dirent_lock.
  35 */
  36static DEFINE_SPINLOCK(sysfs_open_dirent_lock);
  37
  38struct sysfs_open_dirent {
  39        atomic_t                refcnt;
  40        atomic_t                event;
  41        wait_queue_head_t       poll;
  42        struct list_head        buffers; /* goes through sysfs_buffer.list */
  43};
  44
  45struct sysfs_buffer {
  46        size_t                  count;
  47        loff_t                  pos;
  48        char                    * page;
  49        const struct sysfs_ops  * ops;
  50        struct mutex            mutex;
  51        int                     needs_read_fill;
  52        int                     event;
  53        struct list_head        list;
  54};
  55
  56/**
  57 *      fill_read_buffer - allocate and fill buffer from object.
  58 *      @dentry:        dentry pointer.
  59 *      @buffer:        data buffer for file.
  60 *
  61 *      Allocate @buffer->page, if it hasn't been already, then call the
  62 *      kobject's show() method to fill the buffer with this attribute's 
  63 *      data. 
  64 *      This is called only once, on the file's first read unless an error
  65 *      is returned.
  66 */
  67static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer)
  68{
  69        struct sysfs_dirent *attr_sd = dentry->d_fsdata;
  70        struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
  71        const struct sysfs_ops * ops = buffer->ops;
  72        int ret = 0;
  73        ssize_t count;
  74
  75        if (!buffer->page)
  76                buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
  77        if (!buffer->page)
  78                return -ENOMEM;
  79
  80        /* need attr_sd for attr and ops, its parent for kobj */
  81        if (!sysfs_get_active(attr_sd))
  82                return -ENODEV;
  83
  84        buffer->event = atomic_read(&attr_sd->s_attr.open->event);
  85        count = ops->show(kobj, attr_sd->s_attr.attr, buffer->page);
  86
  87        sysfs_put_active(attr_sd);
  88
  89        /*
  90         * The code works fine with PAGE_SIZE return but it's likely to
  91         * indicate truncated result or overflow in normal use cases.
  92         */
  93        if (count >= (ssize_t)PAGE_SIZE) {
  94                print_symbol("fill_read_buffer: %s returned bad count\n",
  95                        (unsigned long)ops->show);
  96                /* Try to struggle along */
  97                count = PAGE_SIZE - 1;
  98        }
  99        if (count >= 0) {
 100                buffer->needs_read_fill = 0;
 101                buffer->count = count;
 102        } else {
 103                ret = count;
 104        }
 105        return ret;
 106}
 107
 108/**
 109 *      sysfs_read_file - read an attribute. 
 110 *      @file:  file pointer.
 111 *      @buf:   buffer to fill.
 112 *      @count: number of bytes to read.
 113 *      @ppos:  starting offset in file.
 114 *
 115 *      Userspace wants to read an attribute file. The attribute descriptor
 116 *      is in the file's ->d_fsdata. The target object is in the directory's
 117 *      ->d_fsdata.
 118 *
 119 *      We call fill_read_buffer() to allocate and fill the buffer from the
 120 *      object's show() method exactly once (if the read is happening from
 121 *      the beginning of the file). That should fill the entire buffer with
 122 *      all the data the object has to offer for that attribute.
 123 *      We then call flush_read_buffer() to copy the buffer to userspace
 124 *      in the increments specified.
 125 */
 126
 127static ssize_t
 128sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 129{
 130        struct sysfs_buffer * buffer = file->private_data;
 131        ssize_t retval = 0;
 132
 133        mutex_lock(&buffer->mutex);
 134        if (buffer->needs_read_fill || *ppos == 0) {
 135                retval = fill_read_buffer(file->f_path.dentry,buffer);
 136                if (retval)
 137                        goto out;
 138        }
 139        pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
 140                 __func__, count, *ppos, buffer->page);
 141        retval = simple_read_from_buffer(buf, count, ppos, buffer->page,
 142                                         buffer->count);
 143out:
 144        mutex_unlock(&buffer->mutex);
 145        return retval;
 146}
 147
 148/**
 149 *      fill_write_buffer - copy buffer from userspace.
 150 *      @buffer:        data buffer for file.
 151 *      @buf:           data from user.
 152 *      @count:         number of bytes in @userbuf.
 153 *
 154 *      Allocate @buffer->page if it hasn't been already, then
 155 *      copy the user-supplied buffer into it.
 156 */
 157
 158static int 
 159fill_write_buffer(struct sysfs_buffer * buffer, const char __user * buf, size_t count)
 160{
 161        int error;
 162
 163        if (!buffer->page)
 164                buffer->page = (char *)get_zeroed_page(GFP_KERNEL);
 165        if (!buffer->page)
 166                return -ENOMEM;
 167
 168        if (count >= PAGE_SIZE)
 169                count = PAGE_SIZE - 1;
 170        error = copy_from_user(buffer->page,buf,count);
 171        buffer->needs_read_fill = 1;
 172        /* if buf is assumed to contain a string, terminate it by \0,
 173           so e.g. sscanf() can scan the string easily */
 174        buffer->page[count] = 0;
 175        return error ? -EFAULT : count;
 176}
 177
 178
 179/**
 180 *      flush_write_buffer - push buffer to kobject.
 181 *      @dentry:        dentry to the attribute
 182 *      @buffer:        data buffer for file.
 183 *      @count:         number of bytes
 184 *
 185 *      Get the correct pointers for the kobject and the attribute we're
 186 *      dealing with, then call the store() method for the attribute, 
 187 *      passing the buffer that we acquired in fill_write_buffer().
 188 */
 189
 190static int
 191flush_write_buffer(struct dentry * dentry, struct sysfs_buffer * buffer, size_t count)
 192{
 193        struct sysfs_dirent *attr_sd = dentry->d_fsdata;
 194        struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
 195        const struct sysfs_ops * ops = buffer->ops;
 196        int rc;
 197
 198        /* need attr_sd for attr and ops, its parent for kobj */
 199        if (!sysfs_get_active(attr_sd))
 200                return -ENODEV;
 201
 202        rc = ops->store(kobj, attr_sd->s_attr.attr, buffer->page, count);
 203
 204        sysfs_put_active(attr_sd);
 205
 206        return rc;
 207}
 208
 209
 210/**
 211 *      sysfs_write_file - write an attribute.
 212 *      @file:  file pointer
 213 *      @buf:   data to write
 214 *      @count: number of bytes
 215 *      @ppos:  starting offset
 216 *
 217 *      Similar to sysfs_read_file(), though working in the opposite direction.
 218 *      We allocate and fill the data from the user in fill_write_buffer(),
 219 *      then push it to the kobject in flush_write_buffer().
 220 *      There is no easy way for us to know if userspace is only doing a partial
 221 *      write, so we don't support them. We expect the entire buffer to come
 222 *      on the first write. 
 223 *      Hint: if you're writing a value, first read the file, modify only the
 224 *      the value you're changing, then write entire buffer back. 
 225 */
 226
 227static ssize_t
 228sysfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 229{
 230        struct sysfs_buffer * buffer = file->private_data;
 231        ssize_t len;
 232
 233        mutex_lock(&buffer->mutex);
 234        len = fill_write_buffer(buffer, buf, count);
 235        if (len > 0)
 236                len = flush_write_buffer(file->f_path.dentry, buffer, len);
 237        if (len > 0)
 238                *ppos += len;
 239        mutex_unlock(&buffer->mutex);
 240        return len;
 241}
 242
 243/**
 244 *      sysfs_get_open_dirent - get or create sysfs_open_dirent
 245 *      @sd: target sysfs_dirent
 246 *      @buffer: sysfs_buffer for this instance of open
 247 *
 248 *      If @sd->s_attr.open exists, increment its reference count;
 249 *      otherwise, create one.  @buffer is chained to the buffers
 250 *      list.
 251 *
 252 *      LOCKING:
 253 *      Kernel thread context (may sleep).
 254 *
 255 *      RETURNS:
 256 *      0 on success, -errno on failure.
 257 */
 258static int sysfs_get_open_dirent(struct sysfs_dirent *sd,
 259                                 struct sysfs_buffer *buffer)
 260{
 261        struct sysfs_open_dirent *od, *new_od = NULL;
 262
 263 retry:
 264        spin_lock_irq(&sysfs_open_dirent_lock);
 265
 266        if (!sd->s_attr.open && new_od) {
 267                sd->s_attr.open = new_od;
 268                new_od = NULL;
 269        }
 270
 271        od = sd->s_attr.open;
 272        if (od) {
 273                atomic_inc(&od->refcnt);
 274                list_add_tail(&buffer->list, &od->buffers);
 275        }
 276
 277        spin_unlock_irq(&sysfs_open_dirent_lock);
 278
 279        if (od) {
 280                kfree(new_od);
 281                return 0;
 282        }
 283
 284        /* not there, initialize a new one and retry */
 285        new_od = kmalloc(sizeof(*new_od), GFP_KERNEL);
 286        if (!new_od)
 287                return -ENOMEM;
 288
 289        atomic_set(&new_od->refcnt, 0);
 290        atomic_set(&new_od->event, 1);
 291        init_waitqueue_head(&new_od->poll);
 292        INIT_LIST_HEAD(&new_od->buffers);
 293        goto retry;
 294}
 295
 296/**
 297 *      sysfs_put_open_dirent - put sysfs_open_dirent
 298 *      @sd: target sysfs_dirent
 299 *      @buffer: associated sysfs_buffer
 300 *
 301 *      Put @sd->s_attr.open and unlink @buffer from the buffers list.
 302 *      If reference count reaches zero, disassociate and free it.
 303 *
 304 *      LOCKING:
 305 *      None.
 306 */
 307static void sysfs_put_open_dirent(struct sysfs_dirent *sd,
 308                                  struct sysfs_buffer *buffer)
 309{
 310        struct sysfs_open_dirent *od = sd->s_attr.open;
 311        unsigned long flags;
 312
 313        spin_lock_irqsave(&sysfs_open_dirent_lock, flags);
 314
 315        list_del(&buffer->list);
 316        if (atomic_dec_and_test(&od->refcnt))
 317                sd->s_attr.open = NULL;
 318        else
 319                od = NULL;
 320
 321        spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags);
 322
 323        kfree(od);
 324}
 325
 326static int sysfs_open_file(struct inode *inode, struct file *file)
 327{
 328        struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
 329        struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
 330        struct sysfs_buffer *buffer;
 331        const struct sysfs_ops *ops;
 332        int error = -EACCES;
 333
 334        /* need attr_sd for attr and ops, its parent for kobj */
 335        if (!sysfs_get_active(attr_sd))
 336                return -ENODEV;
 337
 338        /* every kobject with an attribute needs a ktype assigned */
 339        if (kobj->ktype && kobj->ktype->sysfs_ops)
 340                ops = kobj->ktype->sysfs_ops;
 341        else {
 342                WARN(1, KERN_ERR "missing sysfs attribute operations for "
 343                       "kobject: %s\n", kobject_name(kobj));
 344                goto err_out;
 345        }
 346
 347        /* File needs write support.
 348         * The inode's perms must say it's ok, 
 349         * and we must have a store method.
 350         */
 351        if (file->f_mode & FMODE_WRITE) {
 352                if (!(inode->i_mode & S_IWUGO) || !ops->store)
 353                        goto err_out;
 354        }
 355
 356        /* File needs read support.
 357         * The inode's perms must say it's ok, and we there
 358         * must be a show method for it.
 359         */
 360        if (file->f_mode & FMODE_READ) {
 361                if (!(inode->i_mode & S_IRUGO) || !ops->show)
 362                        goto err_out;
 363        }
 364
 365        /* No error? Great, allocate a buffer for the file, and store it
 366         * it in file->private_data for easy access.
 367         */
 368        error = -ENOMEM;
 369        buffer = kzalloc(sizeof(struct sysfs_buffer), GFP_KERNEL);
 370        if (!buffer)
 371                goto err_out;
 372
 373        mutex_init(&buffer->mutex);
 374        buffer->needs_read_fill = 1;
 375        buffer->ops = ops;
 376        file->private_data = buffer;
 377
 378        /* make sure we have open dirent struct */
 379        error = sysfs_get_open_dirent(attr_sd, buffer);
 380        if (error)
 381                goto err_free;
 382
 383        /* open succeeded, put active references */
 384        sysfs_put_active(attr_sd);
 385        return 0;
 386
 387 err_free:
 388        kfree(buffer);
 389 err_out:
 390        sysfs_put_active(attr_sd);
 391        return error;
 392}
 393
 394static int sysfs_release(struct inode *inode, struct file *filp)
 395{
 396        struct sysfs_dirent *sd = filp->f_path.dentry->d_fsdata;
 397        struct sysfs_buffer *buffer = filp->private_data;
 398
 399        sysfs_put_open_dirent(sd, buffer);
 400
 401        if (buffer->page)
 402                free_page((unsigned long)buffer->page);
 403        kfree(buffer);
 404
 405        return 0;
 406}
 407
 408/* Sysfs attribute files are pollable.  The idea is that you read
 409 * the content and then you use 'poll' or 'select' to wait for
 410 * the content to change.  When the content changes (assuming the
 411 * manager for the kobject supports notification), poll will
 412 * return POLLERR|POLLPRI, and select will return the fd whether
 413 * it is waiting for read, write, or exceptions.
 414 * Once poll/select indicates that the value has changed, you
 415 * need to close and re-open the file, or seek to 0 and read again.
 416 * Reminder: this only works for attributes which actively support
 417 * it, and it is not possible to test an attribute from userspace
 418 * to see if it supports poll (Neither 'poll' nor 'select' return
 419 * an appropriate error code).  When in doubt, set a suitable timeout value.
 420 */
 421static unsigned int sysfs_poll(struct file *filp, poll_table *wait)
 422{
 423        struct sysfs_buffer * buffer = filp->private_data;
 424        struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata;
 425        struct sysfs_open_dirent *od = attr_sd->s_attr.open;
 426
 427        /* need parent for the kobj, grab both */
 428        if (!sysfs_get_active(attr_sd))
 429                goto trigger;
 430
 431        poll_wait(filp, &od->poll, wait);
 432
 433        sysfs_put_active(attr_sd);
 434
 435        if (buffer->event != atomic_read(&od->event))
 436                goto trigger;
 437
 438        return DEFAULT_POLLMASK;
 439
 440 trigger:
 441        buffer->needs_read_fill = 1;
 442        return DEFAULT_POLLMASK|POLLERR|POLLPRI;
 443}
 444
 445void sysfs_notify_dirent(struct sysfs_dirent *sd)
 446{
 447        struct sysfs_open_dirent *od;
 448        unsigned long flags;
 449
 450        spin_lock_irqsave(&sysfs_open_dirent_lock, flags);
 451
 452        od = sd->s_attr.open;
 453        if (od) {
 454                atomic_inc(&od->event);
 455                wake_up_interruptible(&od->poll);
 456        }
 457
 458        spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags);
 459}
 460EXPORT_SYMBOL_GPL(sysfs_notify_dirent);
 461
 462void sysfs_notify(struct kobject *k, const char *dir, const char *attr)
 463{
 464        struct sysfs_dirent *sd = k->sd;
 465
 466        mutex_lock(&sysfs_mutex);
 467
 468        if (sd && dir)
 469                sd = sysfs_find_dirent(sd, NULL, dir);
 470        if (sd && attr)
 471                sd = sysfs_find_dirent(sd, NULL, attr);
 472        if (sd)
 473                sysfs_notify_dirent(sd);
 474
 475        mutex_unlock(&sysfs_mutex);
 476}
 477EXPORT_SYMBOL_GPL(sysfs_notify);
 478
 479const struct file_operations sysfs_file_operations = {
 480        .read           = sysfs_read_file,
 481        .write          = sysfs_write_file,
 482        .llseek         = generic_file_llseek,
 483        .open           = sysfs_open_file,
 484        .release        = sysfs_release,
 485        .poll           = sysfs_poll,
 486};
 487
 488int sysfs_attr_ns(struct kobject *kobj, const struct attribute *attr,
 489                  const void **pns)
 490{
 491        struct sysfs_dirent *dir_sd = kobj->sd;
 492        const struct sysfs_ops *ops;
 493        const void *ns = NULL;
 494        int err;
 495
 496        if (!dir_sd) {
 497                WARN(1, KERN_ERR "sysfs: kobject %s without dirent\n",
 498                        kobject_name(kobj));
 499                return -ENOENT;
 500        }
 501
 502        err = 0;
 503        if (!sysfs_ns_type(dir_sd))
 504                goto out;
 505
 506        err = -EINVAL;
 507        if (!kobj->ktype)
 508                goto out;
 509        ops = kobj->ktype->sysfs_ops;
 510        if (!ops)
 511                goto out;
 512        if (!ops->namespace)
 513                goto out;
 514
 515        err = 0;
 516        ns = ops->namespace(kobj, attr);
 517out:
 518        if (err) {
 519                WARN(1, KERN_ERR "missing sysfs namespace attribute operation for "
 520                     "kobject: %s\n", kobject_name(kobj));
 521        }
 522        *pns = ns;
 523        return err;
 524}
 525
 526int sysfs_add_file_mode(struct sysfs_dirent *dir_sd,
 527                        const struct attribute *attr, int type, umode_t amode)
 528{
 529        umode_t mode = (amode & S_IALLUGO) | S_IFREG;
 530        struct sysfs_addrm_cxt acxt;
 531        struct sysfs_dirent *sd;
 532        const void *ns;
 533        int rc;
 534
 535        rc = sysfs_attr_ns(dir_sd->s_dir.kobj, attr, &ns);
 536        if (rc)
 537                return rc;
 538
 539        sd = sysfs_new_dirent(attr->name, mode, type);
 540        if (!sd)
 541                return -ENOMEM;
 542
 543        sd->s_ns = ns;
 544        sd->s_attr.attr = (void *)attr;
 545        sysfs_dirent_init_lockdep(sd);
 546
 547        sysfs_addrm_start(&acxt, dir_sd);
 548        rc = sysfs_add_one(&acxt, sd);
 549        sysfs_addrm_finish(&acxt);
 550
 551        if (rc)
 552                sysfs_put(sd);
 553
 554        return rc;
 555}
 556
 557
 558int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,
 559                   int type)
 560{
 561        return sysfs_add_file_mode(dir_sd, attr, type, attr->mode);
 562}
 563
 564
 565/**
 566 *      sysfs_create_file - create an attribute file for an object.
 567 *      @kobj:  object we're creating for. 
 568 *      @attr:  attribute descriptor.
 569 */
 570
 571int sysfs_create_file(struct kobject * kobj, const struct attribute * attr)
 572{
 573        BUG_ON(!kobj || !kobj->sd || !attr);
 574
 575        return sysfs_add_file(kobj->sd, attr, SYSFS_KOBJ_ATTR);
 576
 577}
 578
 579int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
 580{
 581        int err = 0;
 582        int i;
 583
 584        for (i = 0; ptr[i] && !err; i++)
 585                err = sysfs_create_file(kobj, ptr[i]);
 586        if (err)
 587                while (--i >= 0)
 588                        sysfs_remove_file(kobj, ptr[i]);
 589        return err;
 590}
 591
 592/**
 593 * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
 594 * @kobj: object we're acting for.
 595 * @attr: attribute descriptor.
 596 * @group: group name.
 597 */
 598int sysfs_add_file_to_group(struct kobject *kobj,
 599                const struct attribute *attr, const char *group)
 600{
 601        struct sysfs_dirent *dir_sd;
 602        int error;
 603
 604        if (group)
 605                dir_sd = sysfs_get_dirent(kobj->sd, NULL, group);
 606        else
 607                dir_sd = sysfs_get(kobj->sd);
 608
 609        if (!dir_sd)
 610                return -ENOENT;
 611
 612        error = sysfs_add_file(dir_sd, attr, SYSFS_KOBJ_ATTR);
 613        sysfs_put(dir_sd);
 614
 615        return error;
 616}
 617EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
 618
 619/**
 620 * sysfs_chmod_file - update the modified mode value on an object attribute.
 621 * @kobj: object we're acting for.
 622 * @attr: attribute descriptor.
 623 * @mode: file permissions.
 624 *
 625 */
 626int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
 627                     umode_t mode)
 628{
 629        struct sysfs_dirent *sd;
 630        struct iattr newattrs;
 631        const void *ns;
 632        int rc;
 633
 634        rc = sysfs_attr_ns(kobj, attr, &ns);
 635        if (rc)
 636                return rc;
 637
 638        mutex_lock(&sysfs_mutex);
 639
 640        rc = -ENOENT;
 641        sd = sysfs_find_dirent(kobj->sd, ns, attr->name);
 642        if (!sd)
 643                goto out;
 644
 645        newattrs.ia_mode = (mode & S_IALLUGO) | (sd->s_mode & ~S_IALLUGO);
 646        newattrs.ia_valid = ATTR_MODE;
 647        rc = sysfs_sd_setattr(sd, &newattrs);
 648
 649 out:
 650        mutex_unlock(&sysfs_mutex);
 651        return rc;
 652}
 653EXPORT_SYMBOL_GPL(sysfs_chmod_file);
 654
 655
 656/**
 657 *      sysfs_remove_file - remove an object attribute.
 658 *      @kobj:  object we're acting for.
 659 *      @attr:  attribute descriptor.
 660 *
 661 *      Hash the attribute name and kill the victim.
 662 */
 663
 664void sysfs_remove_file(struct kobject * kobj, const struct attribute * attr)
 665{
 666        const void *ns;
 667
 668        if (sysfs_attr_ns(kobj, attr, &ns))
 669                return;
 670
 671        sysfs_hash_and_remove(kobj->sd, ns, attr->name);
 672}
 673
 674void sysfs_remove_files(struct kobject * kobj, const struct attribute **ptr)
 675{
 676        int i;
 677        for (i = 0; ptr[i]; i++)
 678                sysfs_remove_file(kobj, ptr[i]);
 679}
 680
 681/**
 682 * sysfs_remove_file_from_group - remove an attribute file from a group.
 683 * @kobj: object we're acting for.
 684 * @attr: attribute descriptor.
 685 * @group: group name.
 686 */
 687void sysfs_remove_file_from_group(struct kobject *kobj,
 688                const struct attribute *attr, const char *group)
 689{
 690        struct sysfs_dirent *dir_sd;
 691
 692        if (group)
 693                dir_sd = sysfs_get_dirent(kobj->sd, NULL, group);
 694        else
 695                dir_sd = sysfs_get(kobj->sd);
 696        if (dir_sd) {
 697                sysfs_hash_and_remove(dir_sd, NULL, attr->name);
 698                sysfs_put(dir_sd);
 699        }
 700}
 701EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
 702
 703struct sysfs_schedule_callback_struct {
 704        struct list_head        workq_list;
 705        struct kobject          *kobj;
 706        void                    (*func)(void *);
 707        void                    *data;
 708        struct module           *owner;
 709        struct work_struct      work;
 710};
 711
 712static struct workqueue_struct *sysfs_workqueue;
 713static DEFINE_MUTEX(sysfs_workq_mutex);
 714static LIST_HEAD(sysfs_workq);
 715static void sysfs_schedule_callback_work(struct work_struct *work)
 716{
 717        struct sysfs_schedule_callback_struct *ss = container_of(work,
 718                        struct sysfs_schedule_callback_struct, work);
 719
 720        (ss->func)(ss->data);
 721        kobject_put(ss->kobj);
 722        module_put(ss->owner);
 723        mutex_lock(&sysfs_workq_mutex);
 724        list_del(&ss->workq_list);
 725        mutex_unlock(&sysfs_workq_mutex);
 726        kfree(ss);
 727}
 728
 729/**
 730 * sysfs_schedule_callback - helper to schedule a callback for a kobject
 731 * @kobj: object we're acting for.
 732 * @func: callback function to invoke later.
 733 * @data: argument to pass to @func.
 734 * @owner: module owning the callback code
 735 *
 736 * sysfs attribute methods must not unregister themselves or their parent
 737 * kobject (which would amount to the same thing).  Attempts to do so will
 738 * deadlock, since unregistration is mutually exclusive with driver
 739 * callbacks.
 740 *
 741 * Instead methods can call this routine, which will attempt to allocate
 742 * and schedule a workqueue request to call back @func with @data as its
 743 * argument in the workqueue's process context.  @kobj will be pinned
 744 * until @func returns.
 745 *
 746 * Returns 0 if the request was submitted, -ENOMEM if storage could not
 747 * be allocated, -ENODEV if a reference to @owner isn't available,
 748 * -EAGAIN if a callback has already been scheduled for @kobj.
 749 */
 750int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
 751                void *data, struct module *owner)
 752{
 753        struct sysfs_schedule_callback_struct *ss, *tmp;
 754
 755        if (!try_module_get(owner))
 756                return -ENODEV;
 757
 758        mutex_lock(&sysfs_workq_mutex);
 759        list_for_each_entry_safe(ss, tmp, &sysfs_workq, workq_list)
 760                if (ss->kobj == kobj) {
 761                        module_put(owner);
 762                        mutex_unlock(&sysfs_workq_mutex);
 763                        return -EAGAIN;
 764                }
 765        mutex_unlock(&sysfs_workq_mutex);
 766
 767        if (sysfs_workqueue == NULL) {
 768                sysfs_workqueue = create_singlethread_workqueue("sysfsd");
 769                if (sysfs_workqueue == NULL) {
 770                        module_put(owner);
 771                        return -ENOMEM;
 772                }
 773        }
 774
 775        ss = kmalloc(sizeof(*ss), GFP_KERNEL);
 776        if (!ss) {
 777                module_put(owner);
 778                return -ENOMEM;
 779        }
 780        kobject_get(kobj);
 781        ss->kobj = kobj;
 782        ss->func = func;
 783        ss->data = data;
 784        ss->owner = owner;
 785        INIT_WORK(&ss->work, sysfs_schedule_callback_work);
 786        INIT_LIST_HEAD(&ss->workq_list);
 787        mutex_lock(&sysfs_workq_mutex);
 788        list_add_tail(&ss->workq_list, &sysfs_workq);
 789        mutex_unlock(&sysfs_workq_mutex);
 790        queue_work(sysfs_workqueue, &ss->work);
 791        return 0;
 792}
 793EXPORT_SYMBOL_GPL(sysfs_schedule_callback);
 794
 795
 796EXPORT_SYMBOL_GPL(sysfs_create_file);
 797EXPORT_SYMBOL_GPL(sysfs_remove_file);
 798EXPORT_SYMBOL_GPL(sysfs_remove_files);
 799EXPORT_SYMBOL_GPL(sysfs_create_files);
 800
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