inode.c

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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 <[email protected]>
 *
 * 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 <linux/slab.h>
#include <linux/sysfs.h>
#include <linux/xattr.h>
#include <linux/security.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 = {
    .name       = "sysfs",
    .ra_pages   = 0,    /* No readahead */
    .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
};

static const struct inode_operations sysfs_inode_operations ={
    .permission = sysfs_permission,
    .setattr    = sysfs_setattr,
    .getattr    = sysfs_getattr,
    .setxattr   = sysfs_setxattr,
};

int __init sysfs_inode_init(void)
{
    return bdi_init(&sysfs_backing_dev_info);
}

static struct sysfs_inode_attrs *sysfs_init_inode_attrs(struct sysfs_dirent *sd)
{
    struct sysfs_inode_attrs *attrs;
    struct iattr *iattrs;

    attrs = kzalloc(sizeof(struct sysfs_inode_attrs), GFP_KERNEL);
    if (!attrs)
        return NULL;
    iattrs = &attrs->ia_iattr;

    /* assign default attributes */
    iattrs->ia_mode = sd->s_mode;
    iattrs->ia_uid = GLOBAL_ROOT_UID;
    iattrs->ia_gid = GLOBAL_ROOT_GID;
    iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;

    return attrs;
}

int sysfs_sd_setattr(struct sysfs_dirent *sd, struct iattr * iattr)
{
    struct sysfs_inode_attrs *sd_attrs;
    struct iattr *iattrs;
    unsigned int ia_valid = iattr->ia_valid;

    sd_attrs = sd->s_iattr;

    if (!sd_attrs) {
        /* setting attributes for the first time, allocate now */
        sd_attrs = sysfs_init_inode_attrs(sd);
        if (!sd_attrs)
            return -ENOMEM;
        sd->s_iattr = sd_attrs;
    }
    /* attributes were changed at least once in past */
    iattrs = &sd_attrs->ia_iattr;

    if (ia_valid & ATTR_UID)
        iattrs->ia_uid = iattr->ia_uid;
    if (ia_valid & ATTR_GID)
        iattrs->ia_gid = iattr->ia_gid;
    if (ia_valid & ATTR_ATIME)
        iattrs->ia_atime = iattr->ia_atime;
    if (ia_valid & ATTR_MTIME)
        iattrs->ia_mtime = iattr->ia_mtime;
    if (ia_valid & ATTR_CTIME)
        iattrs->ia_ctime = iattr->ia_ctime;
    if (ia_valid & ATTR_MODE) {
        umode_t mode = iattr->ia_mode;
        iattrs->ia_mode = sd->s_mode = mode;
    }
    return 0;
}

int sysfs_setattr(struct dentry *dentry, struct iattr *iattr)
{
    struct inode *inode = dentry->d_inode;
    struct sysfs_dirent *sd = dentry->d_fsdata;
    int error;

    if (!sd)
        return -EINVAL;

    mutex_lock(&sysfs_mutex);
    error = inode_change_ok(inode, iattr);
    if (error)
        goto out;

    error = sysfs_sd_setattr(sd, iattr);
    if (error)
        goto out;

    /* this ignores size changes */
    setattr_copy(inode, iattr);

out:
    mutex_unlock(&sysfs_mutex);
    return error;
}

static int sysfs_sd_setsecdata(struct sysfs_dirent *sd, void **secdata, u32 *secdata_len)
{
    struct sysfs_inode_attrs *iattrs;
    void *old_secdata;
    size_t old_secdata_len;

    if (!sd->s_iattr) {
        sd->s_iattr = sysfs_init_inode_attrs(sd);
        if (!sd->s_iattr)
            return -ENOMEM;
    }

    iattrs = sd->s_iattr;
    old_secdata = iattrs->ia_secdata;
    old_secdata_len = iattrs->ia_secdata_len;

    iattrs->ia_secdata = *secdata;
    iattrs->ia_secdata_len = *secdata_len;

    *secdata = old_secdata;
    *secdata_len = old_secdata_len;
    return 0;
}

int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
        size_t size, int flags)
{
    struct sysfs_dirent *sd = dentry->d_fsdata;
    void *secdata;
    int error;
    u32 secdata_len = 0;

    if (!sd)
        return -EINVAL;

    if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
        const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
        error = security_inode_setsecurity(dentry->d_inode, suffix,
                        value, size, flags);
        if (error)
            goto out;
        error = security_inode_getsecctx(dentry->d_inode,
                        &secdata, &secdata_len);
        if (error)
            goto out;

        mutex_lock(&sysfs_mutex);
        error = sysfs_sd_setsecdata(sd, &secdata, &secdata_len);
        mutex_unlock(&sysfs_mutex);

        if (secdata)
            security_release_secctx(secdata, secdata_len);
    } else
        return -EINVAL;
out:
    return error;
}

static inline void set_default_inode_attr(struct inode * inode, umode_t mode)
{
    inode->i_mode = mode;
    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_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;
}

static void sysfs_refresh_inode(struct sysfs_dirent *sd, struct inode *inode)
{
    struct sysfs_inode_attrs *iattrs = sd->s_iattr;

    inode->i_mode = sd->s_mode;
    if (iattrs) {
        /* sysfs_dirent has non-default attributes
         * get them from persistent copy in sysfs_dirent
         */
        set_inode_attr(inode, &iattrs->ia_iattr);
        security_inode_notifysecctx(inode,
                        iattrs->ia_secdata,
                        iattrs->ia_secdata_len);
    }

    if (sysfs_type(sd) == SYSFS_DIR)
        set_nlink(inode, sd->s_dir.subdirs + 2);
}

int sysfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
{
    struct sysfs_dirent *sd = dentry->d_fsdata;
    struct inode *inode = dentry->d_inode;

    mutex_lock(&sysfs_mutex);
    sysfs_refresh_inode(sd, inode);
    mutex_unlock(&sysfs_mutex);

    generic_fillattr(inode, stat);
    return 0;
}

static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
{
    struct bin_attribute *bin_attr;

    inode->i_private = sysfs_get(sd);
    inode->i_mapping->a_ops = &sysfs_aops;
    inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
    inode->i_op = &sysfs_inode_operations;

    set_default_inode_attr(inode, sd->s_mode);
    sysfs_refresh_inode(sd, inode);

    /* 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;
        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);
}

struct inode * sysfs_get_inode(struct super_block *sb, struct sysfs_dirent *sd)
{
    struct inode *inode;

    inode = iget_locked(sb, sd->s_ino);
    if (inode && (inode->i_state & I_NEW))
        sysfs_init_inode(sd, inode);

    return inode;
}

/*
 * The sysfs_dirent serves as both an inode and a directory entry for sysfs.
 * To prevent the sysfs inode numbers from being freed prematurely we take a
 * reference to sysfs_dirent from the sysfs inode.  A
 * super_operations.evict_inode() implementation is needed to drop that
 * reference upon inode destruction.
 */
void sysfs_evict_inode(struct inode *inode)
{
    struct sysfs_dirent *sd  = inode->i_private;

    truncate_inode_pages(&inode->i_data, 0);
    clear_inode(inode);
    sysfs_put(sd);
}

int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const void *ns, const char *name)
{
    struct sysfs_addrm_cxt acxt;
    struct sysfs_dirent *sd;

    if (!dir_sd) {
        WARN(1, KERN_WARNING "sysfs: can not remove '%s', no directory\n",
            name);
        return -ENOENT;
    }

    sysfs_addrm_start(&acxt, dir_sd);

    sd = sysfs_find_dirent(dir_sd, ns, name);
    if (sd)
        sysfs_remove_one(&acxt, sd);

    sysfs_addrm_finish(&acxt);

    if (sd)
        return 0;
    else
        return -ENOENT;
}

int sysfs_permission(struct inode *inode, int mask)
{
    struct sysfs_dirent *sd;

    if (mask & MAY_NOT_BLOCK)
        return -ECHILD;

    sd = inode->i_private;

    mutex_lock(&sysfs_mutex);
    sysfs_refresh_inode(sd, inode);
    mutex_unlock(&sysfs_mutex);

    return generic_permission(inode, mask);
}