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732dbef606
Dcookies shouldn't play with the internals of dentry and vfsmnt refcounting. It defeats grepping, and is prone to break if implementation details change. In addition the function doesn't even seem to be performance critical: it calls kmem_cache_alloc(). Signed-off-by: Miklos Szeredi <miklos@szeredi.hu> Acked-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
329 lines
6.2 KiB
C
329 lines
6.2 KiB
C
/*
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* dcookies.c
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*
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* Copyright 2002 John Levon <levon@movementarian.org>
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*
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* Persistent cookie-path mappings. These are used by
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* profilers to convert a per-task EIP value into something
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* non-transitory that can be processed at a later date.
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* This is done by locking the dentry/vfsmnt pair in the
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* kernel until released by the tasks needing the persistent
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* objects. The tag is simply an unsigned long that refers
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* to the pair and can be looked up from userspace.
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*/
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#include <linux/config.h>
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#include <linux/syscalls.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/list.h>
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#include <linux/mount.h>
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#include <linux/dcache.h>
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#include <linux/mm.h>
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#include <linux/errno.h>
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#include <linux/dcookies.h>
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#include <asm/uaccess.h>
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/* The dcookies are allocated from a kmem_cache and
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* hashed onto a small number of lists. None of the
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* code here is particularly performance critical
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*/
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struct dcookie_struct {
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struct dentry * dentry;
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struct vfsmount * vfsmnt;
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struct list_head hash_list;
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};
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static LIST_HEAD(dcookie_users);
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static DECLARE_MUTEX(dcookie_sem);
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static kmem_cache_t * dcookie_cache;
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static struct list_head * dcookie_hashtable;
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static size_t hash_size;
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static inline int is_live(void)
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{
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return !(list_empty(&dcookie_users));
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}
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/* The dentry is locked, its address will do for the cookie */
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static inline unsigned long dcookie_value(struct dcookie_struct * dcs)
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{
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return (unsigned long)dcs->dentry;
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}
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static size_t dcookie_hash(unsigned long dcookie)
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{
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return (dcookie >> L1_CACHE_SHIFT) & (hash_size - 1);
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}
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static struct dcookie_struct * find_dcookie(unsigned long dcookie)
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{
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struct dcookie_struct *found = NULL;
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struct dcookie_struct * dcs;
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struct list_head * pos;
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struct list_head * list;
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list = dcookie_hashtable + dcookie_hash(dcookie);
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list_for_each(pos, list) {
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dcs = list_entry(pos, struct dcookie_struct, hash_list);
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if (dcookie_value(dcs) == dcookie) {
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found = dcs;
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break;
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}
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}
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return found;
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}
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static void hash_dcookie(struct dcookie_struct * dcs)
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{
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struct list_head * list = dcookie_hashtable + dcookie_hash(dcookie_value(dcs));
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list_add(&dcs->hash_list, list);
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}
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static struct dcookie_struct * alloc_dcookie(struct dentry * dentry,
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struct vfsmount * vfsmnt)
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{
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struct dcookie_struct * dcs = kmem_cache_alloc(dcookie_cache, GFP_KERNEL);
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if (!dcs)
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return NULL;
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dentry->d_cookie = dcs;
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dcs->dentry = dget(dentry);
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dcs->vfsmnt = mntget(vfsmnt);
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hash_dcookie(dcs);
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return dcs;
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}
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/* This is the main kernel-side routine that retrieves the cookie
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* value for a dentry/vfsmnt pair.
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*/
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int get_dcookie(struct dentry * dentry, struct vfsmount * vfsmnt,
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unsigned long * cookie)
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{
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int err = 0;
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struct dcookie_struct * dcs;
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down(&dcookie_sem);
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if (!is_live()) {
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err = -EINVAL;
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goto out;
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}
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dcs = dentry->d_cookie;
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if (!dcs)
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dcs = alloc_dcookie(dentry, vfsmnt);
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if (!dcs) {
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err = -ENOMEM;
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goto out;
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}
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*cookie = dcookie_value(dcs);
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out:
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up(&dcookie_sem);
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return err;
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}
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/* And here is where the userspace process can look up the cookie value
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* to retrieve the path.
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*/
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asmlinkage long sys_lookup_dcookie(u64 cookie64, char __user * buf, size_t len)
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{
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unsigned long cookie = (unsigned long)cookie64;
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int err = -EINVAL;
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char * kbuf;
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char * path;
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size_t pathlen;
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struct dcookie_struct * dcs;
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/* we could leak path information to users
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* without dir read permission without this
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*/
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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down(&dcookie_sem);
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if (!is_live()) {
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err = -EINVAL;
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goto out;
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}
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if (!(dcs = find_dcookie(cookie)))
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goto out;
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err = -ENOMEM;
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kbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
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if (!kbuf)
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goto out;
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/* FIXME: (deleted) ? */
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path = d_path(dcs->dentry, dcs->vfsmnt, kbuf, PAGE_SIZE);
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if (IS_ERR(path)) {
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err = PTR_ERR(path);
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goto out_free;
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}
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err = -ERANGE;
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pathlen = kbuf + PAGE_SIZE - path;
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if (pathlen <= len) {
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err = pathlen;
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if (copy_to_user(buf, path, pathlen))
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err = -EFAULT;
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}
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out_free:
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kfree(kbuf);
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out:
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up(&dcookie_sem);
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return err;
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}
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static int dcookie_init(void)
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{
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struct list_head * d;
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unsigned int i, hash_bits;
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int err = -ENOMEM;
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dcookie_cache = kmem_cache_create("dcookie_cache",
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sizeof(struct dcookie_struct),
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0, 0, NULL, NULL);
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if (!dcookie_cache)
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goto out;
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dcookie_hashtable = kmalloc(PAGE_SIZE, GFP_KERNEL);
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if (!dcookie_hashtable)
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goto out_kmem;
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err = 0;
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/*
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* Find the power-of-two list-heads that can fit into the allocation..
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* We don't guarantee that "sizeof(struct list_head)" is necessarily
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* a power-of-two.
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*/
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hash_size = PAGE_SIZE / sizeof(struct list_head);
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hash_bits = 0;
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do {
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hash_bits++;
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} while ((hash_size >> hash_bits) != 0);
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hash_bits--;
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/*
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* Re-calculate the actual number of entries and the mask
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* from the number of bits we can fit.
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*/
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hash_size = 1UL << hash_bits;
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/* And initialize the newly allocated array */
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d = dcookie_hashtable;
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i = hash_size;
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do {
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INIT_LIST_HEAD(d);
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d++;
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i--;
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} while (i);
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out:
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return err;
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out_kmem:
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kmem_cache_destroy(dcookie_cache);
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goto out;
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}
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static void free_dcookie(struct dcookie_struct * dcs)
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{
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dcs->dentry->d_cookie = NULL;
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dput(dcs->dentry);
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mntput(dcs->vfsmnt);
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kmem_cache_free(dcookie_cache, dcs);
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}
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static void dcookie_exit(void)
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{
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struct list_head * list;
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struct list_head * pos;
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struct list_head * pos2;
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struct dcookie_struct * dcs;
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size_t i;
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for (i = 0; i < hash_size; ++i) {
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list = dcookie_hashtable + i;
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list_for_each_safe(pos, pos2, list) {
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dcs = list_entry(pos, struct dcookie_struct, hash_list);
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list_del(&dcs->hash_list);
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free_dcookie(dcs);
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}
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}
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kfree(dcookie_hashtable);
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kmem_cache_destroy(dcookie_cache);
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}
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struct dcookie_user {
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struct list_head next;
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};
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struct dcookie_user * dcookie_register(void)
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{
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struct dcookie_user * user;
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down(&dcookie_sem);
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user = kmalloc(sizeof(struct dcookie_user), GFP_KERNEL);
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if (!user)
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goto out;
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if (!is_live() && dcookie_init())
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goto out_free;
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list_add(&user->next, &dcookie_users);
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out:
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up(&dcookie_sem);
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return user;
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out_free:
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kfree(user);
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user = NULL;
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goto out;
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}
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void dcookie_unregister(struct dcookie_user * user)
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{
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down(&dcookie_sem);
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list_del(&user->next);
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kfree(user);
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if (!is_live())
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dcookie_exit();
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up(&dcookie_sem);
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}
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EXPORT_SYMBOL_GPL(dcookie_register);
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EXPORT_SYMBOL_GPL(dcookie_unregister);
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EXPORT_SYMBOL_GPL(get_dcookie);
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