/*

* 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/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/vfs.h>

#include <linux/writeback.h> /* for the emergency remount stuff */

#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);

spinlock_t sb_lock = SPIN_LOCK_UNLOCKED;

/**

* 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_rwsem(&s->s_umount);

sema_init(&s->s_lock, 1);

down_write(&s->s_umount);

s->s_count = S_BIAS;

atomic_set(&s->s_active, 1);

sema_init(&s->s_vfs_rename_sem,1);

sema_init(&s->s_dquot.dqio_sem, 1);

sema_init(&s->s_dquot.dqonoff_sem, 1);

init_rwsem(&s->s_dquot.dqptr_sem);

s->s_maxbytes = MAX_NON_LFS;

s->dq_op = sb_dquot_ops;

s->s_qcop = sb_quotactl_ops;

s->s_op = &default_op;

}

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 */

/**

* put_super - drop a temporary reference to superblock

* @s: superblock in question

*

* Drops a temporary reference, frees superblock if there's no

* references left.

*/

static inline void put_super(struct super_block *s)

{

spin_lock(&sb_lock);

if (!--s->s_count)

destroy_super(s);

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);

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);

lock_kernel();

sb->s_flags &= ~MS_ACTIVE;

/* bad name - it should be evict_inodes() */

invalidate_inodes(sb);

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. "

"Self-destruct in 5 seconds. Have a nice day...\n");

}

unlock_kernel();

unlock_super(sb);

}

spin_lock(&sb_lock);

list_del(&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;

list_add(&s->s_list, super_blocks.prev);

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;

restart:

spin_lock(&sb_lock);

sb = sb_entry(super_blocks.next);

while (sb != sb_entry(&super_blocks))

if (sb->s_dirt) {

sb->s_count++;

spin_unlock(&sb_lock);

down_read(&sb->s_umount);

write_super(sb);

drop_super(sb);

goto restart;

} else

sb = sb_entry(sb->s_list.next);

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.

*

* FIXME: If wait==0, we only really need to call ->sync_fs if s_dirt is true.

*/

void sync_filesystems(int wait)

{

struct super_block *sb;

static DECLARE_MUTEX(mutex);

down(&mutex); /* Could be down_interruptible */

spin_lock(&sb_lock);

for (sb = sb_entry(super_blocks.next); sb != sb_entry(&super_blocks);

sb = sb_entry(sb->s_list.next)) {

if (!sb->s_op->sync_fs)

continue;

if (sb->s_flags & MS_RDONLY)

continue;

sb->s_need_sync_fs = 1;

}

spin_unlock(&sb_lock);

restart:

spin_lock(&sb_lock);

for (sb = sb_entry(super_blocks.next); sb != sb_entry(&super_blocks);

sb = sb_entry(sb->s_list.next)) {

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)

sb->s_op->sync_fs(sb, wait);

drop_super(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 list_head *p;

if (!bdev)

return NULL;

rescan:

spin_lock(&sb_lock);

list_for_each(p, &super_blocks) {

struct super_block *s = sb_entry(p);

if (s->s_bdev == bdev) {

s->s_count++;

spin_unlock(&sb_lock);

down_read(&s->s_umount);

if (s->s_root)

return s;

drop_super(s);

goto rescan;

}

}

spin_unlock(&sb_lock);

return NULL;

}

EXPORT_SYMBOL(get_super);

struct super_block * user_get_super(dev_t dev)

{

struct list_head *p;

rescan:

spin_lock(&sb_lock);

list_for_each(p, &super_blocks) {

struct super_block *s = sb_entry(p);

if (s->s_dev == dev) {

s->s_count++;

spin_unlock(&sb_lock);

down_read(&s->s_umount);

if (s->s_root)

return s;

drop_super(s);

goto rescan;

}

}

spin_unlock(&sb_lock);

return NULL;

}

EXPORT_SYMBOL(user_get_super);

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;

}

static void mark_files_ro(struct super_block *sb)

{

struct file *f;

file_list_lock();

list_for_each_entry(f, &sb->s_files, f_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, make sure there are no rw files open */

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

*/

enum {Max_anon = 256};

static unsigned long unnamed_dev_in_use[Max_anon/(8*sizeof(unsigned long))];

static spinlock_t unnamed_dev_lock = SPIN_LOCK_UNLOCKED;/* protects the above */

int set_anon_super(struct super_block *s, void *data)

{

int dev;

spin_lock(&unnamed_dev_lock);

dev = find_first_zero_bit(unnamed_dev_in_use, Max_anon);

if (dev == Max_anon) {

spin_unlock(&unnamed_dev_lock);

return -EMFILE;

}

set_bit(dev, unnamed_dev_in_use);

spin_unlock(&unnamed_dev_lock);

s->s_dev = MKDEV(0, dev);

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);

clear_bit(slot, unnamed_dev_in_use);

spin_unlock(&unnamed_dev_lock);

}

EXPORT_SYMBOL(kill_anon_super);

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;

}

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, BDEV_FS, fs_type);

if (IS_ERR(bdev))

return (struct super_block *)bdev;

s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);

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;

strncpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));

s->s_old_blocksize = block_size(bdev);

sb_set_blocksize(s, s->s_old_blocksize);

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;

}

return s;

out:

close_bdev_excl(bdev, BDEV_FS);

return s;

}

EXPORT_SYMBOL(get_sb_bdev);

void kill_block_super(struct super_block *sb)

{

struct block_device *bdev = sb->s_bdev;

generic_shutdown_super(sb);

set_blocksize(bdev, sb->s_old_blocksize);

close_bdev_excl(bdev, BDEV_FS);

}

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;

if (!type)

return ERR_PTR(-ENODEV);

mnt = alloc_vfsmnt(name);

if (!mnt)

goto out;

sb = type->get_sb(type, flags, name, data);

if (IS_ERR(sb))

goto out_mnt;

error = security_sb_kern_mount(sb);

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);

put_filesystem(type);

return mnt;

out_sb:

up_write(&sb->s_umount);

deactivate_super(sb);

sb = ERR_PTR(error);

out_mnt:

free_vfsmnt(mnt);

out:

put_filesystem(type);

return (struct vfsmount *)sb;

}

struct vfsmount *kern_mount(struct file_system_type *type)

{

return do_kern_mount(type->name, 0, type->name, NULL);

}

EXPORT_SYMBOL(kern_mount);