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![Linus Torvalds](/assets/img/avatar_default.png)
Pull printk updates from Petr Mladek: - Add a console_msg_format command line option: The value "default" keeps the old "[time stamp] text\n" format. The value "syslog" allows to see the syslog-like "<log level>[timestamp] text" format. This feature was requested by people doing regression tests, for example, 0day robot. They want to have both filtered and full logs at hands. - Reduce the risk of softlockup: Pass the console owner in a busy loop. This is a new approach to the old problem. It was first proposed by Steven Rostedt on Kernel Summit 2017. It marks a context in which the console_lock owner calls console drivers and could not sleep. On the other side, printk() callers could detect this state and use a busy wait instead of a simple console_trylock(). Finally, the console_lock owner checks if there is a busy waiter at the end of the special context and eventually passes the console_lock to the waiter. The hand-off works surprisingly well and helps in many situations. Well, there is still a possibility of the softlockup, for example, when the flood of messages stops and the last owner still has too much to flush. There is increasing number of people having problems with printk-related softlockups. We might eventually need to get better solution. Anyway, this looks like a good start and promising direction. - Do not allow to schedule in console_unlock() called from printk(): This reverts an older controversial commit. The reschedule helped to avoid softlockups. But it also slowed down the console output. This patch is obsoleted by the new console waiter logic described above. In fact, the reschedule made the hand-off less effective. - Deprecate "%pf" and "%pF" format specifier: It was needed on ia64, ppc64 and parisc64 to dereference function descriptors and show the real function address. It is done transparently by "%ps" and "pS" format specifier now. Sergey Senozhatsky found that all the function descriptors were in a special elf section and could be easily detected. - Remove printk_symbol() API: It has been obsoleted by "%pS" format specifier, and this change helped to remove few continuous lines and a less intuitive old API. - Remove redundant memsets: Sergey removed unnecessary memset when processing printk.devkmsg command line option. * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk: (27 commits) printk: drop redundant devkmsg_log_str memsets printk: Never set console_may_schedule in console_trylock() printk: Hide console waiter logic into helpers printk: Add console owner and waiter logic to load balance console writes kallsyms: remove print_symbol() function checkpatch: add pF/pf deprecation warning symbol lookup: introduce dereference_symbol_descriptor() parisc64: Add .opd based function descriptor dereference powerpc64: Add .opd based function descriptor dereference ia64: Add .opd based function descriptor dereference sections: split dereference_function_descriptor() openrisc: Fix conflicting types for _exext and _stext lib: do not use print_symbol() irq debug: do not use print_symbol() sysfs: do not use print_symbol() drivers: do not use print_symbol() x86: do not use print_symbol() unicore32: do not use print_symbol() sh: do not use print_symbol() mn10300: do not use print_symbol() ...
505 lines
12 KiB
C
505 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* fs/sysfs/file.c - sysfs regular (text) file implementation
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*
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* Copyright (c) 2001-3 Patrick Mochel
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* Copyright (c) 2007 SUSE Linux Products GmbH
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* Copyright (c) 2007 Tejun Heo <teheo@suse.de>
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*
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* Please see Documentation/filesystems/sysfs.txt for more information.
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*/
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#include <linux/module.h>
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#include <linux/kobject.h>
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#include <linux/slab.h>
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#include <linux/list.h>
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#include <linux/mutex.h>
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#include <linux/seq_file.h>
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#include "sysfs.h"
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#include "../kernfs/kernfs-internal.h"
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/*
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* Determine ktype->sysfs_ops for the given kernfs_node. This function
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* must be called while holding an active reference.
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*/
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static const struct sysfs_ops *sysfs_file_ops(struct kernfs_node *kn)
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{
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struct kobject *kobj = kn->parent->priv;
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if (kn->flags & KERNFS_LOCKDEP)
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lockdep_assert_held(kn);
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return kobj->ktype ? kobj->ktype->sysfs_ops : NULL;
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}
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/*
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* Reads on sysfs are handled through seq_file, which takes care of hairy
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* details like buffering and seeking. The following function pipes
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* sysfs_ops->show() result through seq_file.
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*/
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static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
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{
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struct kernfs_open_file *of = sf->private;
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struct kobject *kobj = of->kn->parent->priv;
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const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
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ssize_t count;
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char *buf;
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/* acquire buffer and ensure that it's >= PAGE_SIZE and clear */
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count = seq_get_buf(sf, &buf);
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if (count < PAGE_SIZE) {
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seq_commit(sf, -1);
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return 0;
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}
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memset(buf, 0, PAGE_SIZE);
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/*
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* Invoke show(). Control may reach here via seq file lseek even
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* if @ops->show() isn't implemented.
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*/
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if (ops->show) {
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count = ops->show(kobj, of->kn->priv, buf);
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if (count < 0)
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return count;
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}
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/*
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* The code works fine with PAGE_SIZE return but it's likely to
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* indicate truncated result or overflow in normal use cases.
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*/
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if (count >= (ssize_t)PAGE_SIZE) {
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printk("fill_read_buffer: %pS returned bad count\n",
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ops->show);
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/* Try to struggle along */
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count = PAGE_SIZE - 1;
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}
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seq_commit(sf, count);
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return 0;
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}
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static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
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size_t count, loff_t pos)
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{
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struct bin_attribute *battr = of->kn->priv;
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struct kobject *kobj = of->kn->parent->priv;
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loff_t size = file_inode(of->file)->i_size;
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if (!count)
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return 0;
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if (size) {
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if (pos >= size)
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return 0;
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if (pos + count > size)
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count = size - pos;
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}
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if (!battr->read)
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return -EIO;
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return battr->read(of->file, kobj, battr, buf, pos, count);
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}
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/* kernfs read callback for regular sysfs files with pre-alloc */
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static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf,
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size_t count, loff_t pos)
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{
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const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
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struct kobject *kobj = of->kn->parent->priv;
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ssize_t len;
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/*
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* If buf != of->prealloc_buf, we don't know how
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* large it is, so cannot safely pass it to ->show
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*/
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if (WARN_ON_ONCE(buf != of->prealloc_buf))
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return 0;
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len = ops->show(kobj, of->kn->priv, buf);
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if (len < 0)
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return len;
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if (pos) {
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if (len <= pos)
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return 0;
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len -= pos;
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memmove(buf, buf + pos, len);
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}
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return min_t(ssize_t, count, len);
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}
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/* kernfs write callback for regular sysfs files */
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static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
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size_t count, loff_t pos)
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{
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const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
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struct kobject *kobj = of->kn->parent->priv;
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if (!count)
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return 0;
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return ops->store(kobj, of->kn->priv, buf, count);
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}
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/* kernfs write callback for bin sysfs files */
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static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
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size_t count, loff_t pos)
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{
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struct bin_attribute *battr = of->kn->priv;
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struct kobject *kobj = of->kn->parent->priv;
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loff_t size = file_inode(of->file)->i_size;
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if (size) {
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if (size <= pos)
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return -EFBIG;
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count = min_t(ssize_t, count, size - pos);
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}
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if (!count)
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return 0;
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if (!battr->write)
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return -EIO;
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return battr->write(of->file, kobj, battr, buf, pos, count);
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}
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static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
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struct vm_area_struct *vma)
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{
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struct bin_attribute *battr = of->kn->priv;
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struct kobject *kobj = of->kn->parent->priv;
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return battr->mmap(of->file, kobj, battr, vma);
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}
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void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
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{
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struct kernfs_node *kn = kobj->sd, *tmp;
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if (kn && dir)
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kn = kernfs_find_and_get(kn, dir);
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else
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kernfs_get(kn);
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if (kn && attr) {
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tmp = kernfs_find_and_get(kn, attr);
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kernfs_put(kn);
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kn = tmp;
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}
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if (kn) {
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kernfs_notify(kn);
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kernfs_put(kn);
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}
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}
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EXPORT_SYMBOL_GPL(sysfs_notify);
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static const struct kernfs_ops sysfs_file_kfops_empty = {
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};
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static const struct kernfs_ops sysfs_file_kfops_ro = {
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.seq_show = sysfs_kf_seq_show,
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};
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static const struct kernfs_ops sysfs_file_kfops_wo = {
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.write = sysfs_kf_write,
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};
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static const struct kernfs_ops sysfs_file_kfops_rw = {
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.seq_show = sysfs_kf_seq_show,
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.write = sysfs_kf_write,
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};
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static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
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.read = sysfs_kf_read,
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.prealloc = true,
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};
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static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
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.write = sysfs_kf_write,
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.prealloc = true,
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};
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static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
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.read = sysfs_kf_read,
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.write = sysfs_kf_write,
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.prealloc = true,
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};
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static const struct kernfs_ops sysfs_bin_kfops_ro = {
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.read = sysfs_kf_bin_read,
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};
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static const struct kernfs_ops sysfs_bin_kfops_wo = {
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.write = sysfs_kf_bin_write,
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};
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static const struct kernfs_ops sysfs_bin_kfops_rw = {
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.read = sysfs_kf_bin_read,
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.write = sysfs_kf_bin_write,
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};
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static const struct kernfs_ops sysfs_bin_kfops_mmap = {
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.read = sysfs_kf_bin_read,
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.write = sysfs_kf_bin_write,
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.mmap = sysfs_kf_bin_mmap,
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};
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int sysfs_add_file_mode_ns(struct kernfs_node *parent,
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const struct attribute *attr, bool is_bin,
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umode_t mode, const void *ns)
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{
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struct lock_class_key *key = NULL;
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const struct kernfs_ops *ops;
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struct kernfs_node *kn;
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loff_t size;
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if (!is_bin) {
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struct kobject *kobj = parent->priv;
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const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
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/* every kobject with an attribute needs a ktype assigned */
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if (WARN(!sysfs_ops, KERN_ERR
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"missing sysfs attribute operations for kobject: %s\n",
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kobject_name(kobj)))
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return -EINVAL;
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if (sysfs_ops->show && sysfs_ops->store) {
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if (mode & SYSFS_PREALLOC)
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ops = &sysfs_prealloc_kfops_rw;
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else
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ops = &sysfs_file_kfops_rw;
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} else if (sysfs_ops->show) {
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if (mode & SYSFS_PREALLOC)
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ops = &sysfs_prealloc_kfops_ro;
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else
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ops = &sysfs_file_kfops_ro;
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} else if (sysfs_ops->store) {
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if (mode & SYSFS_PREALLOC)
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ops = &sysfs_prealloc_kfops_wo;
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else
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ops = &sysfs_file_kfops_wo;
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} else
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ops = &sysfs_file_kfops_empty;
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size = PAGE_SIZE;
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} else {
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struct bin_attribute *battr = (void *)attr;
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if (battr->mmap)
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ops = &sysfs_bin_kfops_mmap;
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else if (battr->read && battr->write)
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ops = &sysfs_bin_kfops_rw;
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else if (battr->read)
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ops = &sysfs_bin_kfops_ro;
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else if (battr->write)
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ops = &sysfs_bin_kfops_wo;
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else
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ops = &sysfs_file_kfops_empty;
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size = battr->size;
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}
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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if (!attr->ignore_lockdep)
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key = attr->key ?: (struct lock_class_key *)&attr->skey;
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#endif
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kn = __kernfs_create_file(parent, attr->name, mode & 0777, size, ops,
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(void *)attr, ns, key);
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if (IS_ERR(kn)) {
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if (PTR_ERR(kn) == -EEXIST)
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sysfs_warn_dup(parent, attr->name);
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return PTR_ERR(kn);
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}
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return 0;
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}
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int sysfs_add_file(struct kernfs_node *parent, const struct attribute *attr,
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bool is_bin)
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{
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return sysfs_add_file_mode_ns(parent, attr, is_bin, attr->mode, NULL);
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}
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/**
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* sysfs_create_file_ns - create an attribute file for an object with custom ns
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* @kobj: object we're creating for
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* @attr: attribute descriptor
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* @ns: namespace the new file should belong to
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*/
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int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
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const void *ns)
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{
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BUG_ON(!kobj || !kobj->sd || !attr);
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return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode, ns);
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}
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EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
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int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
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{
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int err = 0;
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int i;
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for (i = 0; ptr[i] && !err; i++)
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err = sysfs_create_file(kobj, ptr[i]);
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if (err)
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while (--i >= 0)
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sysfs_remove_file(kobj, ptr[i]);
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return err;
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}
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EXPORT_SYMBOL_GPL(sysfs_create_files);
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/**
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* sysfs_add_file_to_group - add an attribute file to a pre-existing group.
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* @kobj: object we're acting for.
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* @attr: attribute descriptor.
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* @group: group name.
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*/
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int sysfs_add_file_to_group(struct kobject *kobj,
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const struct attribute *attr, const char *group)
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{
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struct kernfs_node *parent;
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int error;
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if (group) {
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parent = kernfs_find_and_get(kobj->sd, group);
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} else {
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parent = kobj->sd;
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kernfs_get(parent);
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}
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if (!parent)
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return -ENOENT;
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error = sysfs_add_file(parent, attr, false);
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kernfs_put(parent);
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return error;
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}
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EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
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/**
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* sysfs_chmod_file - update the modified mode value on an object attribute.
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* @kobj: object we're acting for.
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* @attr: attribute descriptor.
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* @mode: file permissions.
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*
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*/
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int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
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umode_t mode)
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{
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struct kernfs_node *kn;
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struct iattr newattrs;
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int rc;
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kn = kernfs_find_and_get(kobj->sd, attr->name);
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if (!kn)
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return -ENOENT;
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newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
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newattrs.ia_valid = ATTR_MODE;
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rc = kernfs_setattr(kn, &newattrs);
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kernfs_put(kn);
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return rc;
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}
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EXPORT_SYMBOL_GPL(sysfs_chmod_file);
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/**
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* sysfs_remove_file_ns - remove an object attribute with a custom ns tag
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* @kobj: object we're acting for
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* @attr: attribute descriptor
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* @ns: namespace tag of the file to remove
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*
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* Hash the attribute name and namespace tag and kill the victim.
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*/
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void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
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const void *ns)
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{
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struct kernfs_node *parent = kobj->sd;
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kernfs_remove_by_name_ns(parent, attr->name, ns);
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}
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EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
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/**
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* sysfs_remove_file_self - remove an object attribute from its own method
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* @kobj: object we're acting for
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* @attr: attribute descriptor
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*
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* See kernfs_remove_self() for details.
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*/
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bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
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{
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struct kernfs_node *parent = kobj->sd;
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struct kernfs_node *kn;
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bool ret;
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kn = kernfs_find_and_get(parent, attr->name);
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if (WARN_ON_ONCE(!kn))
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return false;
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ret = kernfs_remove_self(kn);
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kernfs_put(kn);
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return ret;
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}
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void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
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{
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int i;
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for (i = 0; ptr[i]; i++)
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sysfs_remove_file(kobj, ptr[i]);
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}
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EXPORT_SYMBOL_GPL(sysfs_remove_files);
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/**
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* sysfs_remove_file_from_group - remove an attribute file from a group.
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* @kobj: object we're acting for.
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* @attr: attribute descriptor.
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* @group: group name.
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*/
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void sysfs_remove_file_from_group(struct kobject *kobj,
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const struct attribute *attr, const char *group)
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{
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struct kernfs_node *parent;
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if (group) {
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parent = kernfs_find_and_get(kobj->sd, group);
|
|
} else {
|
|
parent = kobj->sd;
|
|
kernfs_get(parent);
|
|
}
|
|
|
|
if (parent) {
|
|
kernfs_remove_by_name(parent, attr->name);
|
|
kernfs_put(parent);
|
|
}
|
|
}
|
|
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);
|