diff options
Diffstat (limited to 'fs/super.c')
| -rw-r--r-- | fs/super.c | 860 |
1 files changed, 860 insertions, 0 deletions
diff --git a/fs/super.c b/fs/super.c new file mode 100644 index 000000000000..3a1b8ca04ba6 --- /dev/null +++ b/fs/super.c @@ -0,0 +1,860 @@ +/* + * 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); + 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); + 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); + 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. " + "Self-destruct in 5 seconds. Have a nice day...\n"); + } + + 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; +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. + * + * (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); + 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 && (wait || sb->s_dirt)) + 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; +} + +/** + * 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_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, NULL); + else + kobject_uevent(&bdev->bd_disk->kobj, action, NULL); + } +} + +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 + */ + down(&bdev->bd_mount_sem); + s = sget(fs_type, test_bdev_super, set_bdev_super, bdev); + up(&bdev->bd_mount_sem); + 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)); + 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; + 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; + mnt->mnt_namespace = current->namespace; + 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_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); |