b592fcfe7f
The problem. When implementing a network namespace I need to be able to have multiple network devices with the same name. Currently this is a problem for /sys/class/net/*. What I want is a separate /sys/class/net directory in sysfs for each network namespace, and I want to name each of them /sys/class/net. I looked and the VFS actually allows that. All that is needed is for /sys/class/net to implement a follow link method to redirect lookups to the real directory you want. Implementing a follow link method that is sensitive to the current network namespace turns out to be 3 lines of code so it looks like a clean approach. Modifying sysfs so it doesn't get in my was is a bit trickier. I am calling the concept of multiple directories all at the same path in the filesystem shadow directories. With the directory entry really at that location the shadow master. The following patch modifies sysfs so it can handle a directory structure slightly different from the kobject tree so I can implement the shadow directories for handling /sys/class/net/. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Cc: Maneesh Soni <maneesh@in.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
119 lines
2.6 KiB
C
119 lines
2.6 KiB
C
/*
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* mount.c - operations for initializing and mounting sysfs.
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*/
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#define DEBUG
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#include <linux/fs.h>
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#include <linux/mount.h>
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#include <linux/pagemap.h>
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#include <linux/init.h>
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#include <asm/semaphore.h>
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#include "sysfs.h"
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/* Random magic number */
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#define SYSFS_MAGIC 0x62656572
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struct vfsmount *sysfs_mount;
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struct super_block * sysfs_sb = NULL;
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struct kmem_cache *sysfs_dir_cachep;
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static void sysfs_clear_inode(struct inode *inode);
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static struct super_operations sysfs_ops = {
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.statfs = simple_statfs,
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.drop_inode = sysfs_delete_inode,
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.clear_inode = sysfs_clear_inode,
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};
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static struct sysfs_dirent sysfs_root = {
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.s_sibling = LIST_HEAD_INIT(sysfs_root.s_sibling),
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.s_children = LIST_HEAD_INIT(sysfs_root.s_children),
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.s_element = NULL,
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.s_type = SYSFS_ROOT,
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.s_iattr = NULL,
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};
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static void sysfs_clear_inode(struct inode *inode)
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{
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kfree(inode->i_private);
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}
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static int sysfs_fill_super(struct super_block *sb, void *data, int silent)
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{
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struct inode *inode;
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struct dentry *root;
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sb->s_blocksize = PAGE_CACHE_SIZE;
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sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
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sb->s_magic = SYSFS_MAGIC;
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sb->s_op = &sysfs_ops;
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sb->s_time_gran = 1;
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sysfs_sb = sb;
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inode = sysfs_new_inode(S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
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&sysfs_root);
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if (inode) {
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inode->i_op = &sysfs_dir_inode_operations;
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inode->i_fop = &sysfs_dir_operations;
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/* directory inodes start off with i_nlink == 2 (for "." entry) */
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inc_nlink(inode);
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} else {
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pr_debug("sysfs: could not get root inode\n");
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return -ENOMEM;
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}
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root = d_alloc_root(inode);
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if (!root) {
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pr_debug("%s: could not get root dentry!\n",__FUNCTION__);
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iput(inode);
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return -ENOMEM;
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}
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root->d_fsdata = &sysfs_root;
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sb->s_root = root;
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return 0;
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}
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static int sysfs_get_sb(struct file_system_type *fs_type,
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int flags, const char *dev_name, void *data, struct vfsmount *mnt)
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{
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return get_sb_single(fs_type, flags, data, sysfs_fill_super, mnt);
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}
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static struct file_system_type sysfs_fs_type = {
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.name = "sysfs",
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.get_sb = sysfs_get_sb,
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.kill_sb = kill_litter_super,
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};
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int __init sysfs_init(void)
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{
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int err = -ENOMEM;
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sysfs_dir_cachep = kmem_cache_create("sysfs_dir_cache",
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sizeof(struct sysfs_dirent),
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0, 0, NULL, NULL);
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if (!sysfs_dir_cachep)
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goto out;
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err = register_filesystem(&sysfs_fs_type);
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if (!err) {
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sysfs_mount = kern_mount(&sysfs_fs_type);
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if (IS_ERR(sysfs_mount)) {
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printk(KERN_ERR "sysfs: could not mount!\n");
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err = PTR_ERR(sysfs_mount);
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sysfs_mount = NULL;
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unregister_filesystem(&sysfs_fs_type);
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goto out_err;
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}
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} else
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goto out_err;
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out:
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return err;
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out_err:
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kmem_cache_destroy(sysfs_dir_cachep);
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sysfs_dir_cachep = NULL;
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goto out;
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}
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