forked from luck/tmp_suning_uos_patched
pull handling of one pathname component into a helper
new helper: walk_component(). Handles everything except symlinks; returns negative on error, 0 on success and 1 on symlinks we decided to follow. Drops out of RCU mode on such symlinks. link_path_walk() and do_last() switched to using that. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
parent
11a7b371b6
commit
ce57dfc179
123
fs/namei.c
123
fs/namei.c
@ -785,16 +785,11 @@ __do_follow_link(const struct path *link, struct nameidata *nd, void **p)
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* Without that kind of total limit, nasty chains of consecutive
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* symlinks can cause almost arbitrarily long lookups.
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*/
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static inline int do_follow_link(struct inode *inode, struct path *path, struct nameidata *nd)
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static inline int do_follow_link(struct path *path, struct nameidata *nd)
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{
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void *cookie;
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int err = -ELOOP;
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/* We drop rcu-walk here */
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if (nameidata_dentry_drop_rcu_maybe(nd, path->dentry))
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return -ECHILD;
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BUG_ON(inode != path->dentry->d_inode);
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if (current->link_count >= MAX_NESTED_LINKS)
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goto loop;
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if (current->total_link_count >= 40)
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@ -1337,6 +1332,39 @@ static void terminate_walk(struct nameidata *nd)
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}
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}
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static inline int walk_component(struct nameidata *nd, struct path *path,
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struct qstr *name, int type, int follow)
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{
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struct inode *inode;
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int err;
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/*
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* "." and ".." are special - ".." especially so because it has
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* to be able to know about the current root directory and
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* parent relationships.
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*/
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if (unlikely(type != LAST_NORM))
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return handle_dots(nd, type);
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err = do_lookup(nd, name, path, &inode);
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if (unlikely(err)) {
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terminate_walk(nd);
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return err;
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}
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if (!inode) {
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path_to_nameidata(path, nd);
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terminate_walk(nd);
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return -ENOENT;
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}
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if (unlikely(inode->i_op->follow_link) && follow) {
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if (nameidata_dentry_drop_rcu_maybe(nd, path->dentry))
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return -ECHILD;
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BUG_ON(inode != path->dentry->d_inode);
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return 1;
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}
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path_to_nameidata(path, nd);
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nd->inode = inode;
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return 0;
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}
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/*
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* Name resolution.
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* This is the basic name resolution function, turning a pathname into
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@ -1361,7 +1389,6 @@ static int link_path_walk(const char *name, struct nameidata *nd)
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/* At this point we know we have a real path component. */
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for(;;) {
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struct inode *inode;
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unsigned long hash;
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struct qstr this;
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unsigned int c;
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@ -1414,34 +1441,16 @@ static int link_path_walk(const char *name, struct nameidata *nd)
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if (!*name)
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goto last_with_slashes;
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/*
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* "." and ".." are special - ".." especially so because it has
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* to be able to know about the current root directory and
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* parent relationships.
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*/
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if (unlikely(type != LAST_NORM)) {
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if (handle_dots(nd, type))
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return -ECHILD;
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continue;
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}
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err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW);
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if (err < 0)
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return err;
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/* This does the actual lookups.. */
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err = do_lookup(nd, &this, &next, &inode);
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if (err)
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break;
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if (inode && inode->i_op->follow_link) {
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err = do_follow_link(inode, &next, nd);
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if (err) {
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err = do_follow_link(&next, nd);
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if (err)
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return err;
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nd->inode = nd->path.dentry->d_inode;
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} else {
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path_to_nameidata(&next, nd);
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nd->inode = inode;
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}
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err = -ENOENT;
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if (!nd->inode)
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break;
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err = -ENOTDIR;
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if (!nd->inode->i_op->lookup)
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break;
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@ -1453,36 +1462,27 @@ static int link_path_walk(const char *name, struct nameidata *nd)
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last_component:
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/* Clear LOOKUP_CONTINUE iff it was previously unset */
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nd->flags &= lookup_flags | ~LOOKUP_CONTINUE;
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if (lookup_flags & LOOKUP_PARENT)
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goto lookup_parent;
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if (unlikely(type != LAST_NORM))
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return handle_dots(nd, type);
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err = do_lookup(nd, &this, &next, &inode);
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if (err)
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break;
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if (inode && unlikely(inode->i_op->follow_link) &&
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(lookup_flags & LOOKUP_FOLLOW)) {
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err = do_follow_link(inode, &next, nd);
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if (lookup_flags & LOOKUP_PARENT) {
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nd->last = this;
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nd->last_type = type;
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return 0;
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}
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err = walk_component(nd, &next, &this, type,
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lookup_flags & LOOKUP_FOLLOW);
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if (err < 0)
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return err;
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if (err) {
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err = do_follow_link(&next, nd);
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if (err)
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return err;
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nd->inode = nd->path.dentry->d_inode;
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} else {
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path_to_nameidata(&next, nd);
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nd->inode = inode;
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}
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err = -ENOENT;
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if (!nd->inode)
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break;
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if (lookup_flags & LOOKUP_DIRECTORY) {
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err = -ENOTDIR;
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if (!nd->inode->i_op->lookup)
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break;
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}
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return 0;
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lookup_parent:
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nd->last = this;
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nd->last_type = type;
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return 0;
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}
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terminate_walk(nd);
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return err;
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@ -2068,7 +2068,6 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
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int want_write = 0;
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int acc_mode = op->acc_mode;
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struct file *filp;
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struct inode *inode;
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int error;
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nd->flags &= ~LOOKUP_PARENT;
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@ -2111,24 +2110,12 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
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if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
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symlink_ok = 1;
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/* we _can_ be in RCU mode here */
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error = do_lookup(nd, &nd->last, path, &inode);
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if (error) {
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terminate_walk(nd);
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error = walk_component(nd, path, &nd->last, LAST_NORM,
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!symlink_ok);
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if (error < 0)
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return ERR_PTR(error);
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}
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if (!inode) {
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path_to_nameidata(path, nd);
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terminate_walk(nd);
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return ERR_PTR(-ENOENT);
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}
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if (unlikely(inode->i_op->follow_link && !symlink_ok)) {
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/* We drop rcu-walk here */
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if (nameidata_dentry_drop_rcu_maybe(nd, path->dentry))
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return ERR_PTR(-ECHILD);
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if (error) /* symlink */
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return NULL;
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}
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path_to_nameidata(path, nd);
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nd->inode = inode;
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/* sayonara */
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if (nd->flags & LOOKUP_RCU) {
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if (nameidata_drop_rcu_last(nd))
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@ -2137,7 +2124,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
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error = -ENOTDIR;
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if (nd->flags & LOOKUP_DIRECTORY) {
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if (!inode->i_op->lookup)
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if (!nd->inode->i_op->lookup)
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goto exit;
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}
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audit_inode(pathname, nd->path.dentry);
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