original development tree for Linux kernel GTP module; now long in mainline.
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/*
* fs/sysfs/inode.c - basic sysfs inode and dentry operations
*
* 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.
*/
#undef DEBUG
#include <linux/pagemap.h>
#include <linux/namei.h>
#include <linux/backing-dev.h>
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include "sysfs.h"
extern struct super_block * sysfs_sb;
static const struct address_space_operations sysfs_aops = {
.readpage = simple_readpage,
.write_begin = simple_write_begin,
.write_end = simple_write_end,
};
static struct backing_dev_info sysfs_backing_dev_info = {
.ra_pages = 0, /* No readahead */
.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
};
static const struct inode_operations sysfs_inode_operations ={
.setattr = sysfs_setattr,
};
int __init sysfs_inode_init(void)
{
return bdi_init(&sysfs_backing_dev_info);
}
int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
{
struct inode * inode = dentry->d_inode;
struct sysfs_dirent * sd = dentry->d_fsdata;
struct iattr * sd_iattr;
unsigned int ia_valid = iattr->ia_valid;
int error;
if (!sd)
return -EINVAL;
sd_iattr = sd->s_iattr;
error = inode_change_ok(inode, iattr);
if (error)
return error;
error = inode_setattr(inode, iattr);
if (error)
return error;
if (!sd_iattr) {
/* setting attributes for the first time, allocate now */
sd_iattr = kzalloc(sizeof(struct iattr), GFP_KERNEL);
if (!sd_iattr)
return -ENOMEM;
/* assign default attributes */
sd_iattr->ia_mode = sd->s_mode;
sd_iattr->ia_uid = 0;
sd_iattr->ia_gid = 0;
sd_iattr->ia_atime = sd_iattr->ia_mtime = sd_iattr->ia_ctime = CURRENT_TIME;
sd->s_iattr = sd_iattr;
}
/* attributes were changed atleast once in past */
if (ia_valid & ATTR_UID)
sd_iattr->ia_uid = iattr->ia_uid;
if (ia_valid & ATTR_GID)
sd_iattr->ia_gid = iattr->ia_gid;
if (ia_valid & ATTR_ATIME)
sd_iattr->ia_atime = timespec_trunc(iattr->ia_atime,
inode->i_sb->s_time_gran);
if (ia_valid & ATTR_MTIME)
sd_iattr->ia_mtime = timespec_trunc(iattr->ia_mtime,
inode->i_sb->s_time_gran);
if (ia_valid & ATTR_CTIME)
sd_iattr->ia_ctime = timespec_trunc(iattr->ia_ctime,
inode->i_sb->s_time_gran);
if (ia_valid & ATTR_MODE) {
umode_t mode = iattr->ia_mode;
if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
mode &= ~S_ISGID;
sd_iattr->ia_mode = sd->s_mode = mode;
}
return error;
}
static inline void set_default_inode_attr(struct inode * inode, mode_t mode)
{
inode->i_mode = mode;
inode->i_uid = 0;
inode->i_gid = 0;
inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
}
static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
{
inode->i_mode = iattr->ia_mode;
inode->i_uid = iattr->ia_uid;
inode->i_gid = iattr->ia_gid;
inode->i_atime = iattr->ia_atime;
inode->i_mtime = iattr->ia_mtime;
inode->i_ctime = iattr->ia_ctime;
}
/*
* sysfs has a different i_mutex lock order behavior for i_mutex than other
* filesystems; sysfs i_mutex is called in many places with subsystem locks
* held. At the same time, many of the VFS locking rules do not apply to
* sysfs at all (cross directory rename for example). To untangle this mess
* (which gives false positives in lockdep), we're giving sysfs inodes their
* own class for i_mutex.
*/
static struct lock_class_key sysfs_inode_imutex_key;
static int sysfs_count_nlink(struct sysfs_dirent *sd)
{
struct sysfs_dirent *child;
int nr = 0;
for (child = sd->s_dir.children; child; child = child->s_sibling)
if (sysfs_type(child) == SYSFS_DIR)
nr++;
return nr + 2;
}
static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
{
struct bin_attribute *bin_attr;
inode->i_blocks = 0;
inode->i_mapping->a_ops = &sysfs_aops;
inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
inode->i_op = &sysfs_inode_operations;
inode->i_ino = sd->s_ino;
lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key);
if (sd->s_iattr) {
/* sysfs_dirent has non-default attributes
* get them for the new inode from persistent copy
* in sysfs_dirent
*/
set_inode_attr(inode, sd->s_iattr);
} else
set_default_inode_attr(inode, sd->s_mode);
/* initialize inode according to type */
switch (sysfs_type(sd)) {
case SYSFS_DIR:
inode->i_op = &sysfs_dir_inode_operations;
inode->i_fop = &sysfs_dir_operations;
inode->i_nlink = sysfs_count_nlink(sd);
break;
case SYSFS_KOBJ_ATTR:
inode->i_size = PAGE_SIZE;
inode->i_fop = &sysfs_file_operations;
break;
case SYSFS_KOBJ_BIN_ATTR:
bin_attr = sd->s_bin_attr.bin_attr;
inode->i_size = bin_attr->size;
inode->i_fop = &bin_fops;
break;
case SYSFS_KOBJ_LINK:
inode->i_op = &sysfs_symlink_inode_operations;
break;
default:
BUG();
}
unlock_new_inode(inode);
}
/**
* sysfs_get_inode - get inode for sysfs_dirent
* @sd: sysfs_dirent to allocate inode for
*
* Get inode for @sd. If such inode doesn't exist, a new inode
* is allocated and basics are initialized. New inode is
* returned locked.
*
* LOCKING:
* Kernel thread context (may sleep).
*
* RETURNS:
* Pointer to allocated inode on success, NULL on failure.
*/
struct inode * sysfs_get_inode(struct sysfs_dirent *sd)
{
struct inode *inode;
inode = iget_locked(sysfs_sb, sd->s_ino);
if (inode && (inode->i_state & I_NEW))
sysfs_init_inode(sd, inode);
return inode;
}
int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name)
{
struct sysfs_addrm_cxt acxt;
struct sysfs_dirent *sd;
if (!dir_sd)
return -ENOENT;
sysfs_addrm_start(&acxt, dir_sd);
sd = sysfs_find_dirent(dir_sd, name);
if (sd)
sysfs_remove_one(&acxt, sd);
sysfs_addrm_finish(&acxt);
if (sd)
return 0;
else
return -ENOENT;
}