root/fs/sysfs/inode.c

DEFINITIONS

1. sysfs_inode_init
2. sysfs_setattr
3. set_default_inode_attr
4. set_inode_attr
5. sysfs_count_nlink
6. sysfs_init_inode
7. sysfs_get_inode
8. sysfs_hash_and_remove

/*
 * 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;

        iattr->ia_valid &= ~ATTR_SIZE; /* ignore size changes */

        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;
}