/*
* linux/fs/super.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* super.c contains code to handle: - mount structures
* - super-block tables
* - filesystem drivers list
* - mount system call
* - umount system call
* - ustat system call
*
* GK 2/5/95 - Changed to support mounting the root fs via NFS
*
* Added kerneld support: Jacques Gelinas and Bjorn Ekwall
* Added change_root: Werner Almesberger & Hans Lermen, Feb '96
* Added options to /proc/mounts:
* Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
* Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998
* Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000
*/
#include <linux/config.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/smp_lock.h>
#include <linux/acct.h>
#include <linux/blkdev.h>
#include <linux/quotaops.h>
#include <linux/namei.h>
#include <linux/buffer_head.h> /* for fsync_super() */
#include <linux/mount.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/vfs.h>
#include <linux/writeback.h> /* for the emergency remount stuff */
#include <linux/idr.h>
#include <linux/kobject.h>
#include <asm/uaccess.h>
void get_filesystem(struct file_system_type *fs);
void put_filesystem(struct file_system_type *fs);
struct file_system_type *get_fs_type(const char *name);
LIST_HEAD(super_blocks);
DEFINE_SPINLOCK(sb_lock);
/**
* alloc_super - create new superblock
*
* Allocates and initializes a new &struct super_block. alloc_super()
* returns a pointer new superblock or %NULL if allocation had failed.
*/
static struct super_block *alloc_super(void)
{
struct super_block *s = kmalloc(sizeof(struct super_block), GFP_USER);
static struct super_operations default_op;
if (s) {
memset(s, 0, sizeof(struct super_block));
if (security_sb_alloc(s)) {
kfree(s);
s = NULL;
goto out;
}
INIT_LIST_HEAD(&s->s_dirty);
INIT_LIST_HEAD(&s->s_io);
INIT_LIST_HEAD(&s->s_files);
INIT_LIST_HEAD(&s->s_instances);
INIT_HLIST_HEAD(&s->s_anon);
INIT_LIST_HEAD(&s->s_inodes);
init_rwsem(&s->s_umount);
mutex_init(&s->s_lock);
down_write(&s->s_umount);
s->s_count = S_BIAS;
atomic_set(&s->s_active, 1);
mutex_init(&s->s_vfs_rename_mutex);
mutex_init(&s->s_dquot.dqio_mutex);
mutex_init(&s->s_dquot.dqonoff_mutex);
init_rwsem(&s->s_dquot.dqptr_sem);
init_waitqueue_head(&s->s_wait_unfrozen);
s->s_maxbytes = MAX_NON_LFS;
s->dq_op = sb_dquot_ops;
s->s_qcop = sb_quotactl_ops;
s->s_op = &default_op;
s->s_time_gran = 1000000000;
}
out:
return s;
}
/**
* destroy_super - frees a superblock
* @s: superblock to free
*
* Frees a superblock.
*/
static inline void destroy_super(struct super_block *s)
{
security_sb_free(s);
kfree(s);
}
/* Superblock refcounting */
/*
* Drop a superblock's refcount. Returns non-zero if the superblock was
* destroyed. The caller must hold sb_lock.
*/
int __put_super(struct super_block *sb)
{
int ret = 0;
if (!--sb->s_count) {
destroy_super(sb);
ret = 1;
}
return ret;
}
/*
* Drop a superblock's refcount.
* Returns non-zero if the superblock is about to be destroyed and
* at least is already removed from super_blocks list, so if we are
* making a loop through super blocks then we need to restart.
* The caller must hold sb_lock.
*/
int __put_super_and_need_restart(struct super_block *sb)
{
/* check for race with generic_shutdown_super() */
if (list_empty(&sb->s_list)) {
/* super block is removed, need to restart... */
__put_super(sb);
return 1;
}
/* can't be the last, since s_list is still in use */
sb->s_count--;
BUG_ON(sb->s_count == 0);
return 0;
}
/**
* put_super - drop a temporary reference to superblock
* @sb: superblock in question
*
* Drops a temporary reference, frees superblock if there's no
* references left.
*/
static void put_super(struct super_block *sb)
{
spin_lock(&sb_lock);
__put_super(sb);
spin_unlock(&sb_lock);
}
/**
* deactivate_super - drop an active reference to superblock
* @s: superblock to deactivate
*
* Drops an active reference to superblock, acquiring a temprory one if
* there is no active references left. In that case we lock superblock,
* tell fs driver to shut it down and drop the temporary reference we
* had just acquired.
*/
void deactivate_super(struct super_block *s)
{
struct file_system_type *fs = s->s_type;
if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
s->s_count -= S_BIAS-1;
spin_unlock(&sb_lock);
DQUOT_OFF(s);
down_write(&s->s_umount);
fs->kill_sb(s);
put_filesystem(fs);
put_super(s);
}
}
EXPORT_SYMBOL(deactivate_super);
/**
* grab_super - acquire an active reference
* @s: reference we are trying to make active
*
* Tries to acquire an active reference. grab_super() is used when we
* had just found a superblock in super_blocks or fs_type->fs_supers
* and want to turn it into a full-blown active reference. grab_super()
* is called with sb_lock held and drops it. Returns 1 in case of
* success, 0 if we had failed (superblock contents was already dead or
* dying when grab_super() had been called).
*/
static int grab_super(struct super_block *s)
{
s->s_count++;
spin_unlock(&sb_lock);
down_write(&s->s_umount);
if (s->s_root) {
spin_lock(&sb_lock);
if (s->s_count > S_BIAS) {
atomic_inc(&s->s_active);
s->s_count--;
spin_unlock(&sb_lock);
return 1;
}
spin_unlock(&sb_lock);
}
up_write(&s->s_umount);
put_super(s);
yield();
return 0;
}
/**
* generic_shutdown_super - common helper for ->kill_sb()
* @sb: superblock to kill
*
* generic_shutdown_super() does all fs-independent work on superblock
* shutdown. Typical ->kill_sb() should pick all fs-specific objects
* that need destruction out of superblock, call generic_shutdown_super()
* and release aforementioned objects. Note: dentries and inodes _are_
* taken care of and do not need specific handling.
*/
void generic_shutdown_super(struct super_block *sb)
{
struct dentry *root = sb->s_root;
struct super_operations *sop = sb->s_op;
if (root) {
sb->s_root = NULL;
shrink_dcache_parent(root);
shrink_dcache_anon(&sb->s_anon);
dput(root);
fsync_super(sb);
lock_super(sb);
sb->s_flags &= ~MS_ACTIVE;
/* bad name - it should be evict_inodes() */
invalidate_inodes(sb);
lock_kernel();
if (sop->write_super && sb->s_dirt)
sop->write_super(sb);
if (sop->put_super)
sop->put_super(sb);
/* Forget any remaining inodes */
if (invalidate_inodes(sb)) {
printk("VFS: Busy inodes after unmount of %s. "
"Self-destruct in 5 seconds. Have a nice day...\n",
sb->s_id);
}
unlock_kernel();
unlock_super(sb);
}
spin_lock(&sb_lock);
/* should be initialized for __put_super_and_need_restart() */
list_del_init(&sb->s_list);
list_del(&sb->s_instances);
spin_unlock(&sb_lock);
up_write(&sb->s_umount);
}
EXPORT_SYMBOL(generic_shutdown_super);
/**
* sget - find or create a superblock
* @type: filesystem type superblock should belong to
* @test: comparison callback
* @set: setup callback
* @data: argument to each of them
*/
struct super_block *sget(struct file_system_type *type,
int (*test)(struct super_block *,void *),
int (*set)(struct super_block *,void *),
void *data)
{
struct super_block *s = NULL;
struct list_head *p;
int err;
retry:
spin_lock(&sb_lock);
if (test) list_for_each(p, &type->fs_supers) {
struct super_block *old;
old = list_entry(p, struct super_block, s_instances);
if (!test(old, data))
continue;
if (!grab_super(old))
goto retry;
if (s)
destroy_super(s);
return old;
}
if (!s) {
spin_unlock(&sb_lock);
s = alloc_super();
if (!s)
return ERR_PTR(-ENOMEM);
goto retry;
}
err = set(s, data);
if (err) {
spin_unlock(&sb_lock);
destroy_super(s);
return ERR_PTR(err);
}
s->s_type = type;
strlcpy(s->s_id, type->name, sizeof(s->s_id));
list_add_tail(&s->s_list, &super_blocks);
list_add(&s->s_instances, &type->fs_supers);
spin_unlock(&sb_lock);
get_filesystem(type);
return s;
}
EXPORT_SYMBOL(sget);
void drop_super(struct super_block *sb)
{
up_read(&sb->s_umount);
put_super(sb);
}
EXPORT_SYMBOL(drop_super);
static inline void write_super(struct super_block *sb)
{
lock_super(sb);
if (sb->s_root && sb->s_dirt)
if (sb->s_op->write_super)
sb->s_op->write_super(sb);
unlock_super(sb);
}
/*
* Note: check the dirty flag before waiting, so we don't
* hold up the sync while mounting a device. (The newly
* mounted device won't need syncing.)
*/
void sync_supers(void)
{
struct super_block *sb;
spin_lock(&sb_lock);
restart:
list_for_each_entry(sb, &super_blocks, s_list) {
if (sb->s_dirt) {
sb->s_count++;
spin_unlock(&sb_lock);
down_read(&sb->s_umount);
write_super(sb);
up_read(&sb->s_umount);
spin_lock(&sb_lock);
if (__put_super_and_need_restart(sb))
goto restart;
}
}
spin_unlock(&sb_lock);
}
/*
* Call the ->sync_fs super_op against all filesytems which are r/w and
* which implement it.
*
* This operation is careful to avoid the livelock which could easily happen
* if two or more filesystems are being continuously dirtied. s_need_sync_fs
* is used only here. We set it against all filesystems and then clear it as
* we sync them. So redirtied filesystems are skipped.
*
* But if process A is currently running sync_filesytems and then process B
* calls sync_filesystems as well, process B will set all the s_need_sync_fs
* flags again, which will cause process A to resync everything. Fix that with
* a local mutex.
*
* (Fabian) Avoid sync_fs with clean fs & wait mode 0
*/
void sync_filesystems(int wait)
{
struct super_block *sb;
static DECLARE_MUTEX(mutex);
down(&mutex); /* Could be down_interruptible */
spin_lock(&sb_lock);
list_for_each_entry(sb, &super_blocks, s_list) {
if (!sb->s_op->sync_fs)
continue;
if (sb->s_flags & MS_RDONLY)
continue;
sb->s_need_sync_fs = 1;
}
restart:
list_for_each_entry(sb, &super_blocks, s_list) {
if (!sb->s_need_sync_fs)
continue;
sb->s_need_sync_fs = 0;
if (sb->s_flags & MS_RDONLY)
continue; /* hm. Was remounted r/o meanwhile */
sb->s_count++;
spin_unlock(&sb_lock);
down_read(&sb->s_umount);
if (sb->s_root && (wait || sb->s_dirt))
sb->s_op->sync_fs(sb, wait);
up_read(&sb->s_umount);
/* restart only when sb is no longer on the list */
spin_lock(&sb_lock);
if (__put_super_and_need_restart(sb))
goto restart;
}
spin_unlock(&sb_lock);
up(&mutex);
}
/**
* get_super - get the superblock of a device
* @bdev: device to get the superblock for
*
* Scans the superblock list and finds the superblock of the file system
* mounted on the device given. %NULL is returned if no match is found.
*/
struct super_block * get_super(struct block_device *bdev)
{
struct super_block *sb;
if (!bdev)
return NULL;
spin_lock(&sb_lock);
rescan:
list_for_each_entry(sb, &super_blocks, s_list) {
if (sb->s_bdev == bdev) {
sb->s_count++;
spin_unlock(&sb_lock);
down_read(&sb->s_umount);
if (sb->s_root)
return sb;
up_read(&sb->s_umount);
/* restart only when sb is no longer on the list */
spin_lock(&sb_lock);
if (__put_super_and_need_restart(sb))
goto rescan;
}
}
spin_unlock(&sb_lock);
return NULL;
}
EXPORT_SYMBOL(get_super);
struct super_block * user_get_super(dev_t dev)
{
struct super_block *sb;
spin_lock(&sb_lock);
rescan:
list_for_each_entry(sb, &super_blocks, s_list) {
if (sb->s_dev == dev) {
sb->s_count++;
spin_unlock(&sb_lock);
down_read(&sb->s_umount);
if (sb->s_root)
return sb;
up_read(&sb->s_umount);
/* restart only when sb is no longer on the list */
spin_lock(&sb_lock);
if (__put_super_and_need_restart(sb))
goto rescan;
}
}
spin_unlock(&sb_lock);
return NULL;
}
asmlinkage long sys_ustat(unsigned dev, struct ustat __user * ubuf)
{
struct super_block *s;
struct ustat tmp;
struct kstatfs sbuf;
int err = -EINVAL;
s = user_get_super(new_decode_dev(dev));
if (s == NULL)
goto out;
err = vfs_statfs(s, &sbuf);
drop_super(s);
if (err)
goto out;
memset(&tmp,0,sizeof(struct ustat));
tmp.f_tfree = sbuf.f_bfree;
tmp.f_tinode = sbuf.f_ffree;
err = copy_to_user(ubuf,&tmp,sizeof(struct ustat)) ? -EFAULT : 0;
out:
return err;
}
/**
* mark_files_ro
* @sb: superblock in question
*
* All files are marked read/only. We don't care about pending
* delete files so this should be used in 'force' mode only
*/
static void mark_files_ro(struct super_block *sb)
{
struct file *f;
file_list_lock();
list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
if (S_ISREG(f->f_dentry->d_inode->i_mode) && file_count(f))
f->f_mode &= ~FMODE_WRITE;
}
file_list_unlock();
}
/**
* do_remount_sb - asks filesystem to change mount options.
* @sb: superblock in question
* @flags: numeric part of options
* @data: the rest of options
* @force: whether or not to force the change
*
* Alters the mount options of a mounted file system.
*/
int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
{
int retval;
if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
return -EACCES;
if (flags & MS_RDONLY)
acct_auto_close(sb);
shrink_dcache_sb(sb);
fsync_super(sb);
/* If we are remounting RDONLY and current sb is read/write,
make sure there are no rw files opened */
if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) {
if (force)
mark_files_ro(sb);
else if (!fs_may_remount_ro(sb))
return -EBUSY;
}
if (sb->s_op->remount_fs) {
lock_super(sb);
retval = sb->s_op->remount_fs(sb, &flags, data);
unlock_super(sb);
if (retval)
return retval;
}
sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
return 0;
}
static void do_emergency_remount(unsigned long foo)
{
struct super_block *sb;
spin_lock(&sb_lock);
list_for_each_entry(sb, &super_blocks, s_list) {
sb->s_count++;
spin_unlock(&sb_lock);
down_read(&sb->s_umount);
if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
/*
* ->remount_fs needs lock_kernel().
*
* What lock protects sb->s_flags??
*/
lock_kernel();
do_remount_sb(sb, MS_RDONLY, NULL, 1);
unlock_kernel();
}
drop_super(sb);
spin_lock(&sb_lock);
}
spin_unlock(&sb_lock);
printk("Emergency Remount complete\n");
}
void emergency_remount(void)
{
pdflush_operation(do_emergency_remount, 0);
}
/*
* Unnamed block devices are dummy devices used by virtual
* filesystems which don't use real block-devices. -- jrs
*/
static struct idr unnamed_dev_idr;
static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
int set_anon_super(struct super_block *s, void *data)
{
int dev;
int error;
retry:
if (idr_pre_get(&unnamed_dev_idr, GFP_ATOMIC) == 0)
return -ENOMEM;
spin_lock(&unnamed_dev_lock);
error = idr_get_new(&unnamed_dev_idr, NULL, &dev);
spin_unlock(&unnamed_dev_lock);
if (error == -EAGAIN)
/* We raced and lost with another CPU. */
goto retry;
else if (error)
return -EAGAIN;
if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
spin_lock(&unnamed_dev_lock);
idr_remove(&unnamed_dev_idr, dev);
spin_unlock(&unnamed_dev_lock);
return -EMFILE;
}
s->s_dev = MKDEV(0, dev & MINORMASK);
return 0;
}
EXPORT_SYMBOL(set_anon_super);
void kill_anon_super(struct super_block *sb)
{
int slot = MINOR(sb->s_dev);
generic_shutdown_super(sb);
spin_lock(&unnamed_dev_lock);
idr_remove(&unnamed_dev_idr, slot);
spin_unlock(&unnamed_dev_lock);
}
EXPORT_SYMBOL(kill_anon_super);
void __init unnamed_dev_init(void)
{
idr_init(&unnamed_dev_idr);
}
void kill_litter_super(struct super_block *sb)
{
if (sb->s_root)
d_genocide(sb->s_root);
kill_anon_super(sb);
}
EXPORT_SYMBOL(kill_litter_super);
static int set_bdev_super(struct super_block *s, void *data)
{
s->s_bdev = data;
s->s_dev = s->s_bdev->bd_dev;
return 0;
}
static int test_bdev_super(struct super_block *s, void *data)
{
return (void *)s->s_bdev == data;
}
static void bdev_uevent(struct block_device *bdev, enum kobject_action action)
{
if (bdev->bd_disk) {
if (bdev->bd_part)
kobject_uevent(&bdev->bd_part->kobj, action);
else
kobject_uevent(&bdev->bd_disk->kobj, action);
}
}
struct super_block *get_sb_bdev(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data,
int (*fill_super)(struct super_block *, void *, int))
{
struct block_device *bdev;
struct super_block *s;
int error = 0;
bdev = open_bdev_excl(dev_name, flags, fs_type);
if (IS_ERR(bdev))
return (struct super_block *)bdev;
/*
* once the super is inserted into the list by sget, s_umount
* will protect the lockfs code from trying to start a snapshot
* while we are mounting
*/
mutex_lock(&bdev->bd_mount_mutex);
s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
mutex_unlock(&bdev->bd_mount_mutex);
if (IS_ERR(s))
goto out;
if (s->s_root) {
if ((flags ^ s->s_flags) & MS_RDONLY) {
up_write(&s->s_umount);
deactivate_super(s);
s = ERR_PTR(-EBUSY);
}
goto out;
} else {
char b[BDEVNAME_SIZE];
s->s_flags = flags;
strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
sb_set_blocksize(s, block_size(bdev));
error = fill_super(s, data, flags & MS_VERBOSE ? 1 : 0);
if (error) {
up_write(&s->s_umount);
deactivate_super(s);
s = ERR_PTR(error);
} else {
s->s_flags |= MS_ACTIVE;
bdev_uevent(bdev, KOBJ_MOUNT);
}
}
return s;
out:
close_bdev_excl(bdev);
return s;
}
EXPORT_SYMBOL(get_sb_bdev);
void kill_block_super(struct super_block *sb)
{
struct block_device *bdev = sb->s_bdev;
bdev_uevent(bdev, KOBJ_UMOUNT);
generic_shutdown_super(sb);
sync_blockdev(bdev);
close_bdev_excl(bdev);
}
EXPORT_SYMBOL(kill_block_super);
struct super_block *get_sb_nodev(struct file_system_type *fs_type,
int flags, void *data,
int (*fill_super)(struct super_block *, void *, int))
{
int error;
struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
if (IS_ERR(s))
return s;
s->s_flags = flags;
error = fill_super(s, data, flags & MS_VERBOSE ? 1 : 0);
if (error) {
up_write(&s->s_umount);
deactivate_super(s);
return ERR_PTR(error);
}
s->s_flags |= MS_ACTIVE;
return s;
}
EXPORT_SYMBOL(get_sb_nodev);
static int compare_single(struct super_block *s, void *p)
{
return 1;
}
struct super_block *get_sb_single(struct file_system_type *fs_type,
int flags, void *data,
int (*fill_super)(struct super_block *, void *, int))
{
struct super_block *s;
int error;
s = sget(fs_type, compare_single, set_anon_super, NULL);
if (IS_ERR(s))
return s;
if (!s->s_root) {
s->s_flags = flags;
error = fill_super(s, data, flags & MS_VERBOSE ? 1 : 0);
if (error) {
up_write(&s->s_umount);
deactivate_super(s);
return ERR_PTR(error);
}
s->s_flags |= MS_ACTIVE;
}
do_remount_sb(s, flags, data, 0);
return s;
}
EXPORT_SYMBOL(get_sb_single);
struct vfsmount *
do_kern_mount(const char *fstype, int flags, const char *name, void *data)
{
struct file_system_type *type = get_fs_type(fstype);
struct super_block *sb = ERR_PTR(-ENOMEM);
struct vfsmount *mnt;
int error;
char *secdata = NULL;
if (!type)
return ERR_PTR(-ENODEV);
mnt = alloc_vfsmnt(name);
if (!mnt)
goto out;
if (data) {
secdata = alloc_secdata();
if (!secdata) {
sb = ERR_PTR(-ENOMEM);
goto out_mnt;
}
error = security_sb_copy_data(type, data, secdata);
if (error) {
sb = ERR_PTR(error);
goto out_free_secdata;
}
}
sb = type->get_sb(type, flags, name, data);
if (IS_ERR(sb))
goto out_free_secdata;
error = security_sb_kern_mount(sb, secdata);
if (error)
goto out_sb;
mnt->mnt_sb = sb;
mnt->mnt_root = dget(sb->s_root);
mnt->mnt_mountpoint = sb->s_root;
mnt->mnt_parent = mnt;
up_write(&sb->s_umount);
free_secdata(secdata);
put_filesystem(type);
return mnt;
out_sb:
up_write(&sb->s_umount);
deactivate_super(sb);
sb = ERR_PTR(error);
out_free_secdata:
free_secdata(secdata);
out_mnt:
free_vfsmnt(mnt);
out:
put_filesystem(type);
return (struct vfsmount *)sb;
}
EXPORT_SYMBOL_GPL(do_kern_mount);
struct vfsmount *kern_mount(struct file_system_type *type)
{
return do_kern_mount(type->name, 0, type->name, NULL);
}
EXPORT_SYMBOL(kern_mount);
