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![Tejun Heo](/assets/img/avatar_default.png)
kernfs_dir_ops are currently being invoked without any active reference, which makes it tricky for the invoked operations to determine whether the objects associated those nodes are safe to access and will remain that way for the duration of such operations. kernfs already has active_ref mechanism to deal with this which makes the removal of a given node the synchronization point for gating the file operations. There's no reason for dir_ops to be any different. Update the dir_ops handling so that active_ref is held while the dir_ops are executing. This guarantees that while a dir_ops is executing the target nodes stay alive. As kernfs_dir_ops doesn't have any in-kernel user at this point, this doesn't affect anybody. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
379 lines
11 KiB
C
379 lines
11 KiB
C
/*
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* kernfs.h - pseudo filesystem decoupled from vfs locking
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*
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* This file is released under the GPLv2.
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*/
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#ifndef __LINUX_KERNFS_H
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#define __LINUX_KERNFS_H
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#include <linux/kernel.h>
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#include <linux/err.h>
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#include <linux/list.h>
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#include <linux/mutex.h>
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#include <linux/idr.h>
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#include <linux/lockdep.h>
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#include <linux/rbtree.h>
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#include <linux/atomic.h>
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#include <linux/wait.h>
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struct file;
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struct dentry;
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struct iattr;
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struct seq_file;
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struct vm_area_struct;
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struct super_block;
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struct file_system_type;
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struct kernfs_open_node;
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struct kernfs_iattrs;
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enum kernfs_node_type {
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KERNFS_DIR = 0x0001,
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KERNFS_FILE = 0x0002,
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KERNFS_LINK = 0x0004,
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};
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#define KERNFS_TYPE_MASK 0x000f
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#define KERNFS_FLAG_MASK ~KERNFS_TYPE_MASK
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enum kernfs_node_flag {
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KERNFS_NS = 0x0020,
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KERNFS_HAS_SEQ_SHOW = 0x0040,
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KERNFS_HAS_MMAP = 0x0080,
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KERNFS_LOCKDEP = 0x0100,
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KERNFS_STATIC_NAME = 0x0200,
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KERNFS_SUICIDAL = 0x0400,
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KERNFS_SUICIDED = 0x0800,
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};
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/* type-specific structures for kernfs_node union members */
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struct kernfs_elem_dir {
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unsigned long subdirs;
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/* children rbtree starts here and goes through kn->rb */
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struct rb_root children;
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/*
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* The kernfs hierarchy this directory belongs to. This fits
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* better directly in kernfs_node but is here to save space.
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*/
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struct kernfs_root *root;
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};
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struct kernfs_elem_symlink {
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struct kernfs_node *target_kn;
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};
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struct kernfs_elem_attr {
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const struct kernfs_ops *ops;
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struct kernfs_open_node *open;
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loff_t size;
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};
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/*
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* kernfs_node - the building block of kernfs hierarchy. Each and every
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* kernfs node is represented by single kernfs_node. Most fields are
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* private to kernfs and shouldn't be accessed directly by kernfs users.
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*
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* As long as s_count reference is held, the kernfs_node itself is
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* accessible. Dereferencing elem or any other outer entity requires
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* active reference.
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*/
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struct kernfs_node {
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atomic_t count;
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atomic_t active;
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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struct lockdep_map dep_map;
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#endif
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/* the following two fields are published */
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struct kernfs_node *parent;
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const char *name;
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struct rb_node rb;
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const void *ns; /* namespace tag */
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unsigned int hash; /* ns + name hash */
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union {
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struct kernfs_elem_dir dir;
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struct kernfs_elem_symlink symlink;
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struct kernfs_elem_attr attr;
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};
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void *priv;
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unsigned short flags;
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umode_t mode;
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unsigned int ino;
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struct kernfs_iattrs *iattr;
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};
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/*
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* kernfs_dir_ops may be specified on kernfs_create_root() to support
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* directory manipulation syscalls. These optional callbacks are invoked
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* on the matching syscalls and can perform any kernfs operations which
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* don't necessarily have to be the exact operation requested. An active
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* reference is held for each kernfs_node parameter.
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*/
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struct kernfs_dir_ops {
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int (*mkdir)(struct kernfs_node *parent, const char *name,
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umode_t mode);
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int (*rmdir)(struct kernfs_node *kn);
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int (*rename)(struct kernfs_node *kn, struct kernfs_node *new_parent,
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const char *new_name);
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};
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struct kernfs_root {
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/* published fields */
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struct kernfs_node *kn;
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/* private fields, do not use outside kernfs proper */
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struct ida ino_ida;
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struct kernfs_dir_ops *dir_ops;
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wait_queue_head_t deactivate_waitq;
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};
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struct kernfs_open_file {
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/* published fields */
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struct kernfs_node *kn;
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struct file *file;
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/* private fields, do not use outside kernfs proper */
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struct mutex mutex;
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int event;
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struct list_head list;
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bool mmapped;
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const struct vm_operations_struct *vm_ops;
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};
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struct kernfs_ops {
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/*
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* Read is handled by either seq_file or raw_read().
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*
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* If seq_show() is present, seq_file path is active. Other seq
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* operations are optional and if not implemented, the behavior is
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* equivalent to single_open(). @sf->private points to the
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* associated kernfs_open_file.
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*
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* read() is bounced through kernel buffer and a read larger than
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* PAGE_SIZE results in partial operation of PAGE_SIZE.
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*/
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int (*seq_show)(struct seq_file *sf, void *v);
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void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
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void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
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void (*seq_stop)(struct seq_file *sf, void *v);
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ssize_t (*read)(struct kernfs_open_file *of, char *buf, size_t bytes,
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loff_t off);
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/*
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* write() is bounced through kernel buffer and a write larger than
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* PAGE_SIZE results in partial operation of PAGE_SIZE.
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*/
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ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
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loff_t off);
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int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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struct lock_class_key lockdep_key;
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#endif
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};
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#ifdef CONFIG_SYSFS
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static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
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{
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return kn->flags & KERNFS_TYPE_MASK;
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}
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/**
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* kernfs_enable_ns - enable namespace under a directory
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* @kn: directory of interest, should be empty
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*
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* This is to be called right after @kn is created to enable namespace
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* under it. All children of @kn must have non-NULL namespace tags and
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* only the ones which match the super_block's tag will be visible.
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*/
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static inline void kernfs_enable_ns(struct kernfs_node *kn)
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{
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WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
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WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn->dir.children));
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kn->flags |= KERNFS_NS;
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}
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/**
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* kernfs_ns_enabled - test whether namespace is enabled
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* @kn: the node to test
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*
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* Test whether namespace filtering is enabled for the children of @ns.
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*/
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static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
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{
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return kn->flags & KERNFS_NS;
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}
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struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
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const char *name, const void *ns);
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void kernfs_get(struct kernfs_node *kn);
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void kernfs_put(struct kernfs_node *kn);
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struct kernfs_root *kernfs_create_root(struct kernfs_dir_ops *kdops,
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void *priv);
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void kernfs_destroy_root(struct kernfs_root *root);
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struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
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const char *name, umode_t mode,
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void *priv, const void *ns);
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struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
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const char *name,
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umode_t mode, loff_t size,
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const struct kernfs_ops *ops,
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void *priv, const void *ns,
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bool name_is_static,
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struct lock_class_key *key);
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struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
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const char *name,
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struct kernfs_node *target);
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void kernfs_remove(struct kernfs_node *kn);
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void kernfs_break_active_protection(struct kernfs_node *kn);
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void kernfs_unbreak_active_protection(struct kernfs_node *kn);
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bool kernfs_remove_self(struct kernfs_node *kn);
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int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
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const void *ns);
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int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
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const char *new_name, const void *new_ns);
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int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
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void kernfs_notify(struct kernfs_node *kn);
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const void *kernfs_super_ns(struct super_block *sb);
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struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
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struct kernfs_root *root, const void *ns);
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void kernfs_kill_sb(struct super_block *sb);
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void kernfs_init(void);
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#else /* CONFIG_SYSFS */
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static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
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{ return 0; } /* whatever */
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static inline void kernfs_enable_ns(struct kernfs_node *kn) { }
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static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
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{ return false; }
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static inline struct kernfs_node *
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kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
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const void *ns)
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{ return NULL; }
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static inline void kernfs_get(struct kernfs_node *kn) { }
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static inline void kernfs_put(struct kernfs_node *kn) { }
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static inline struct kernfs_root *
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kernfs_create_root(struct kernfs_dir_ops *kdops, void *priv)
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{ return ERR_PTR(-ENOSYS); }
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static inline void kernfs_destroy_root(struct kernfs_root *root) { }
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static inline struct kernfs_node *
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kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
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umode_t mode, void *priv, const void *ns)
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{ return ERR_PTR(-ENOSYS); }
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static inline struct kernfs_node *
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__kernfs_create_file(struct kernfs_node *parent, const char *name,
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umode_t mode, loff_t size, const struct kernfs_ops *ops,
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void *priv, const void *ns, bool name_is_static,
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struct lock_class_key *key)
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{ return ERR_PTR(-ENOSYS); }
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static inline struct kernfs_node *
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kernfs_create_link(struct kernfs_node *parent, const char *name,
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struct kernfs_node *target)
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{ return ERR_PTR(-ENOSYS); }
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static inline void kernfs_remove(struct kernfs_node *kn) { }
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static inline bool kernfs_remove_self(struct kernfs_node *kn)
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{ return false; }
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static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
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const char *name, const void *ns)
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{ return -ENOSYS; }
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static inline int kernfs_rename_ns(struct kernfs_node *kn,
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struct kernfs_node *new_parent,
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const char *new_name, const void *new_ns)
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{ return -ENOSYS; }
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static inline int kernfs_setattr(struct kernfs_node *kn,
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const struct iattr *iattr)
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{ return -ENOSYS; }
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static inline void kernfs_notify(struct kernfs_node *kn) { }
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static inline const void *kernfs_super_ns(struct super_block *sb)
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{ return NULL; }
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static inline struct dentry *
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kernfs_mount_ns(struct file_system_type *fs_type, int flags,
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struct kernfs_root *root, const void *ns)
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{ return ERR_PTR(-ENOSYS); }
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static inline void kernfs_kill_sb(struct super_block *sb) { }
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static inline void kernfs_init(void) { }
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#endif /* CONFIG_SYSFS */
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static inline struct kernfs_node *
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kernfs_find_and_get(struct kernfs_node *kn, const char *name)
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{
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return kernfs_find_and_get_ns(kn, name, NULL);
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}
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static inline struct kernfs_node *
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kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode,
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void *priv)
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{
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return kernfs_create_dir_ns(parent, name, mode, priv, NULL);
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}
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static inline struct kernfs_node *
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kernfs_create_file_ns(struct kernfs_node *parent, const char *name,
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umode_t mode, loff_t size, const struct kernfs_ops *ops,
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void *priv, const void *ns)
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{
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struct lock_class_key *key = NULL;
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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key = (struct lock_class_key *)&ops->lockdep_key;
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#endif
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return __kernfs_create_file(parent, name, mode, size, ops, priv, ns,
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false, key);
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}
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static inline struct kernfs_node *
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kernfs_create_file(struct kernfs_node *parent, const char *name, umode_t mode,
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loff_t size, const struct kernfs_ops *ops, void *priv)
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{
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return kernfs_create_file_ns(parent, name, mode, size, ops, priv, NULL);
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}
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static inline int kernfs_remove_by_name(struct kernfs_node *parent,
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const char *name)
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{
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return kernfs_remove_by_name_ns(parent, name, NULL);
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}
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static inline struct dentry *
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kernfs_mount(struct file_system_type *fs_type, int flags,
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struct kernfs_root *root)
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{
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return kernfs_mount_ns(fs_type, flags, root, NULL);
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}
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#endif /* __LINUX_KERNFS_H */
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