forked from luck/tmp_suning_uos_patched
94bebf4d1b
This patch prevents a race between IO and removing a file from sysfs. It introduces a list of sysfs_buffers associated with a file at the inode. Upon removal of a file the list is walked and the buffers marked orphaned. IO to orphaned buffers fails with -ENODEV. The driver can safely free associated data structures or be unloaded. Signed-off-by: Oliver Neukum <oliver@neukum.name> Acked-by: Maneesh Soni <maneesh@in.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
193 lines
4.1 KiB
C
193 lines
4.1 KiB
C
/*
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* symlink.c - operations for sysfs symlinks.
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*/
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#include <linux/fs.h>
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#include <linux/mount.h>
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#include <linux/module.h>
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#include <linux/kobject.h>
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#include <linux/namei.h>
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#include <asm/semaphore.h>
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#include "sysfs.h"
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static int object_depth(struct kobject * kobj)
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{
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struct kobject * p = kobj;
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int depth = 0;
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do { depth++; } while ((p = p->parent));
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return depth;
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}
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static int object_path_length(struct kobject * kobj)
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{
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struct kobject * p = kobj;
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int length = 1;
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do {
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length += strlen(kobject_name(p)) + 1;
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p = p->parent;
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} while (p);
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return length;
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}
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static void fill_object_path(struct kobject * kobj, char * buffer, int length)
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{
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struct kobject * p;
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--length;
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for (p = kobj; p; p = p->parent) {
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int cur = strlen(kobject_name(p));
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/* back up enough to print this bus id with '/' */
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length -= cur;
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strncpy(buffer + length,kobject_name(p),cur);
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*(buffer + --length) = '/';
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}
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}
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static int sysfs_add_link(struct dentry * parent, const char * name, struct kobject * target)
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{
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struct sysfs_dirent * parent_sd = parent->d_fsdata;
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struct sysfs_symlink * sl;
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int error = 0;
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error = -ENOMEM;
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sl = kmalloc(sizeof(*sl), GFP_KERNEL);
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if (!sl)
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goto exit1;
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sl->link_name = kmalloc(strlen(name) + 1, GFP_KERNEL);
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if (!sl->link_name)
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goto exit2;
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strcpy(sl->link_name, name);
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sl->target_kobj = kobject_get(target);
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error = sysfs_make_dirent(parent_sd, NULL, sl, S_IFLNK|S_IRWXUGO,
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SYSFS_KOBJ_LINK);
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if (!error)
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return 0;
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kobject_put(target);
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kfree(sl->link_name);
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exit2:
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kfree(sl);
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exit1:
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return error;
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}
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/**
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* sysfs_create_link - create symlink between two objects.
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* @kobj: object whose directory we're creating the link in.
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* @target: object we're pointing to.
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* @name: name of the symlink.
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*/
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int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char * name)
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{
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struct dentry *dentry = NULL;
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int error = -EEXIST;
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BUG_ON(!name);
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if (!kobj) {
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if (sysfs_mount && sysfs_mount->mnt_sb)
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dentry = sysfs_mount->mnt_sb->s_root;
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} else
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dentry = kobj->dentry;
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if (!dentry)
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return -EFAULT;
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mutex_lock(&dentry->d_inode->i_mutex);
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if (!sysfs_dirent_exist(dentry->d_fsdata, name))
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error = sysfs_add_link(dentry, name, target);
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mutex_unlock(&dentry->d_inode->i_mutex);
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return error;
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}
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/**
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* sysfs_remove_link - remove symlink in object's directory.
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* @kobj: object we're acting for.
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* @name: name of the symlink to remove.
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*/
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void sysfs_remove_link(struct kobject * kobj, const char * name)
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{
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sysfs_hash_and_remove(kobj->dentry,name);
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}
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static int sysfs_get_target_path(struct kobject * kobj, struct kobject * target,
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char *path)
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{
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char * s;
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int depth, size;
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depth = object_depth(kobj);
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size = object_path_length(target) + depth * 3 - 1;
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if (size > PATH_MAX)
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return -ENAMETOOLONG;
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pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size);
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for (s = path; depth--; s += 3)
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strcpy(s,"../");
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fill_object_path(target, path, size);
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pr_debug("%s: path = '%s'\n", __FUNCTION__, path);
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return 0;
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}
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static int sysfs_getlink(struct dentry *dentry, char * path)
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{
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struct kobject *kobj, *target_kobj;
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int error = 0;
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kobj = sysfs_get_kobject(dentry->d_parent);
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if (!kobj)
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return -EINVAL;
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target_kobj = sysfs_get_kobject(dentry);
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if (!target_kobj) {
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kobject_put(kobj);
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return -EINVAL;
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}
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down_read(&sysfs_rename_sem);
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error = sysfs_get_target_path(kobj, target_kobj, path);
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up_read(&sysfs_rename_sem);
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kobject_put(kobj);
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kobject_put(target_kobj);
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return error;
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}
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static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
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{
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int error = -ENOMEM;
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unsigned long page = get_zeroed_page(GFP_KERNEL);
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if (page)
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error = sysfs_getlink(dentry, (char *) page);
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nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
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return NULL;
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}
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static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
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{
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char *page = nd_get_link(nd);
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if (!IS_ERR(page))
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free_page((unsigned long)page);
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}
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struct inode_operations sysfs_symlink_inode_operations = {
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.readlink = generic_readlink,
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.follow_link = sysfs_follow_link,
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.put_link = sysfs_put_link,
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};
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EXPORT_SYMBOL_GPL(sysfs_create_link);
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EXPORT_SYMBOL_GPL(sysfs_remove_link);
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