linux-imx

/*

 *  linux/fs/namespace.c

 *

 * (C) Copyright Al Viro 2000, 2001

 *  Released under GPL v2.

 *

 * Based on code from fs/super.c, copyright Linus Torvalds and others.

 * Heavily rewritten.

 */

​

#include <linux/syscalls.h>

#include <linux/export.h>

#include <linux/capability.h>

#include <linux/mnt_namespace.h>

#include <linux/user_namespace.h>

#include <linux/namei.h>

#include <linux/security.h>

#include <linux/cred.h>

#include <linux/idr.h>

#include <linux/init.h>     /* init_rootfs */

#include <linux/fs_struct.h>    /* get_fs_root et.al. */

#include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */

#include <linux/uaccess.h>

#include <linux/proc_ns.h>

#include <linux/magic.h>

#include <linux/memblock.h>

#include <linux/task_work.h>

#include <linux/sched/task.h>

#include <uapi/linux/mount.h>

#include <linux/fs_context.h>

​

#include "pnode.h"

#include "internal.h"

​

/* Maximum number of mounts in a mount namespace */

unsigned int sysctl_mount_max __read_mostly = 100000;

​

static unsigned int m_hash_mask __read_mostly;

static unsigned int m_hash_shift __read_mostly;

static unsigned int mp_hash_mask __read_mostly;

static unsigned int mp_hash_shift __read_mostly;

​

static __initdata unsigned long mhash_entries;

static int __init set_mhash_entries(char *str)

{

    if (!str)

        return 0;

    mhash_entries = simple_strtoul(str, &str, 0);

    return 1;

}

__setup("mhash_entries=", set_mhash_entries);

​

static __initdata unsigned long mphash_entries;

static int __init set_mphash_entries(char *str)

{

    if (!str)

        return 0;

    mphash_entries = simple_strtoul(str, &str, 0);

    return 1;

}

__setup("mphash_entries=", set_mphash_entries);

​

static u64 event;

static DEFINE_IDA(mnt_id_ida);

static DEFINE_IDA(mnt_group_ida);

​

static struct hlist_head *mount_hashtable __read_mostly;

static struct hlist_head *mountpoint_hashtable __read_mostly;

static struct kmem_cache *mnt_cache __read_mostly;

static DECLARE_RWSEM(namespace_sem);

​

/* /sys/fs */

struct kobject *fs_kobj;

EXPORT_SYMBOL_GPL(fs_kobj);

​

/*

 * vfsmount lock may be taken for read to prevent changes to the

 * vfsmount hash, ie. during mountpoint lookups or walking back

 * up the tree.

 *

 * It should be taken for write in all cases where the vfsmount

 * tree or hash is modified or when a vfsmount structure is modified.

 */

__cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock);

​

static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry)

{

    unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);

    tmp += ((unsigned long)dentry / L1_CACHE_BYTES);

    tmp = tmp + (tmp >> m_hash_shift);

    return &mount_hashtable[tmp & m_hash_mask];

}