/* * 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/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/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 <linux/mutex.h> #include <linux/file.h> #include <asm/uaccess.h> #include "internal.h" LIST_HEAD(super_blocks); DEFINE_SPINLOCK(sb_lock); /** * alloc_super - create new superblock * @type: filesystem type superblock should belong to * * 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(struct file_system_type *type) { struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER); static const struct super_operations default_op; if (s) { if (security_sb_alloc(s)) { kfree(s); s = NULL; goto out; } 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_LIST_HEAD(&s->s_dentry_lru); init_rwsem(&s->s_umount); mutex_init(&s->s_lock); lockdep_set_class(&s->s_umount, &type->s_umount_key); /* * The locking rules for s_lock are up to the * filesystem. For example ext3fs has different * lock ordering than usbfs: */ lockdep_set_class(&s->s_lock, &type->s_lock_key); /* * sget() can have s_umount recursion. * * When it cannot find a suitable sb, it allocates a new * one (this one), and tries again to find a suitable old * one. * * In case that succeeds, it will acquire the s_umount * lock of the old one. Since these are clearly distrinct * locks, and this object isn't exposed yet, there's no * risk of deadlocks. * * Annotate this by putting this lock in a different * subclass. */ down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING); 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->s_subtype); kfree(s->s_options); kfree(s); } /* Superblock refcounting */ /* * Drop a superblock's refcount. Returns non-zero if the superblock was * destroyed. The caller must hold sb_lock. */ static 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. */ 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); vfs_dq_off(s, 0); down_write(&s->s_umount); fs->kill_sb(s); put_filesystem(fs); put_super(s); } } EXPORT_SYMBOL(deactivate_super); /** * deactivate_locked_super - drop an active reference to superblock * @s: superblock to deactivate * * Equivalent of up_write(&s->s_umount); deactivate_super(s);, except that * it does not unlock it until it's all over. As the result, it's safe to * use to dispose of new superblock on ->get_sb() failure exits - nobody * will see the sucker until it's all over. Equivalent using up_write + * deactivate_super is safe for that purpose only if superblock is either * safe to use or has NULL ->s_root when we unlock. */ void deactivate_locked_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); vfs_dq_off(s, 0); fs->kill_sb(s); put_filesystem(fs); put_super(s); } else { up_write(&s->s_umount); } } EXPORT_SYMBOL(deactivate_locked_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) __releases(sb_lock) { 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; } /* * Superblock locking. We really ought to get rid of these two. */ void lock_super(struct super_block * sb) { get_fs_excl(); mutex_lock(&sb->s_lock); } void unlock_super(struct super_block * sb) { put_fs_excl(); mutex_unlock(&sb->s_lock); } EXPORT_SYMBOL(lock_super); EXPORT_SYMBOL(unlock_super); /** * 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. * * Upon calling this function, the filesystem may no longer alter or * rearrange the set of dentries belonging to this super_block, nor may it * change the attachments of dentries to inodes. */ void generic_shutdown_super(struct super_block *sb) { const struct super_operations *sop = sb->s_op; if (sb->s_root) { shrink_dcache_for_umount(sb); sync_filesystem(sb); get_fs_excl(); sb->s_flags &= ~MS_ACTIVE; /* bad name - it should be evict_inodes() */ invalidate_inodes(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); } put_fs_excl(); } 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 super_block *old; int err; retry: spin_lock(&sb_lock); if (test) { list_for_each_entry(old, &type->fs_supers, s_instances) { if (!test(old, data)) continue; if (!grab_super(old)) goto retry; if (s) { up_write(&s->s_umount); destroy_super(s); } return old; } } if (!s) { spin_unlock(&sb_lock); s = alloc_super(type); if (!s) return ERR_PTR(-ENOMEM); goto retry; } err = set(s, data); if (err) { spin_unlock(&sb_lock); up_write(&s->s_umount); 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); /** * sync_supers - helper for periodic superblock writeback * * Call the write_super method if present on all dirty superblocks in * the system. This is for the periodic writeback used by most older * filesystems. For data integrity superblock writeback use * sync_filesystems() instead. * * 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_op->write_super && sb->s_dirt) { sb->s_count++; spin_unlock(&sb_lock); down_read(&sb->s_umount); if (sb->s_root && sb->s_dirt) sb->s_op->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); } /** * 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; } SYSCALL_DEFINE2(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->s_root, &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; } /** * 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; int remount_rw; #ifdef CONFIG_BLOCK if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev)) return -EACCES; #endif if (flags & MS_RDONLY) acct_auto_close(sb); shrink_dcache_sb(sb); sync_filesystem(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; retval = vfs_dq_off(sb, 1); if (retval < 0 && retval != -ENOSYS) return -EBUSY; } remount_rw = !(flags & MS_RDONLY) && (sb->s_flags & MS_RDONLY); if (sb->s_op->remount_fs) { retval = sb->s_op->remount_fs(sb, &flags, data); if (retval) return retval; } sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK); if (remount_rw) vfs_dq_quota_on_remount(sb); return 0; } static void do_emergency_remount(struct work_struct *work) { 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_write(&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?? */ do_remount_sb(sb, MS_RDONLY, NULL, 1); } up_write(&sb->s_umount); put_super(sb); spin_lock(&sb_lock); } spin_unlock(&sb_lock); kfree(work); printk("Emergency Remount complete\n"); } void emergency_remount(void) { struct work_struct *work; work = kmalloc(sizeof(*work), GFP_ATOMIC); if (work) { INIT_WORK(work, do_emergency_remount); schedule_work(work); } } /* * Unnamed block devices are dummy devices used by virtual * filesystems which don't use real block-devices. -- jrs */ static DEFINE_IDA(unnamed_dev_ida); static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */ static int unnamed_dev_start = 0; /* don't bother trying below it */ int set_anon_super(struct super_block *s, void *data) { int dev; int error; retry: if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0) return -ENOMEM; spin_lock(&unnamed_dev_lock); error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev); if (!error) unnamed_dev_start = dev + 1; 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); ida_remove(&unnamed_dev_ida, dev); if (unnamed_dev_start > dev) unnamed_dev_start = 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); ida_remove(&unnamed_dev_ida, slot); if (slot < unnamed_dev_start) unnamed_dev_start = slot; 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 ns_test_super(struct super_block *sb, void *data) { return sb->s_fs_info == data; } static int ns_set_super(struct super_block *sb, void *data) { sb->s_fs_info = data; return set_anon_super(sb, NULL); } int get_sb_ns(struct file_system_type *fs_type, int flags, void *data, int (*fill_super)(struct super_block *, void *, int), struct vfsmount *mnt) { struct super_block *sb; sb = sget(fs_type, ns_test_super, ns_set_super, data); if (IS_ERR(sb)) return PTR_ERR(sb); if (!sb->s_root) { int err; sb->s_flags = flags; err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0); if (err) { deactivate_locked_super(sb); return err; } sb->s_flags |= MS_ACTIVE; } simple_set_mnt(mnt, sb); return 0; } EXPORT_SYMBOL(get_sb_ns); #ifdef CONFIG_BLOCK static int set_bdev_super(struct super_block *s, void *data) { s->s_bdev = data; s->s_dev = s->s_bdev->bd_dev; /* * We set the bdi here to the queue backing, file systems can * overwrite this in ->fill_super() */ s->s_bdi = &bdev_get_queue(s->s_bdev)->backing_dev_info; return 0; } static int test_bdev_super(struct super_block *s, void *data) { return (void *)s->s_bdev == data; } int 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 vfsmount *mnt) { struct block_device *bdev; struct super_block *s; fmode_t mode = FMODE_READ; int error = 0; if (!(flags & MS_RDONLY)) mode |= FMODE_WRITE; bdev = open_bdev_exclusive(dev_name, mode, fs_type); if (IS_ERR(bdev)) return PTR_ERR(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 error_s; if (s->s_root) { if ((flags ^ s->s_flags) & MS_RDONLY) { deactivate_locked_super(s); error = -EBUSY; goto error_bdev; } close_bdev_exclusive(bdev, mode); } else { char b[BDEVNAME_SIZE]; s->s_flags = flags; s->s_mode = mode; 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_SILENT ? 1 : 0); if (error) { deactivate_locked_super(s); goto error; } s->s_flags |= MS_ACTIVE; bdev->bd_super = s; } simple_set_mnt(mnt, s); return 0; error_s: error = PTR_ERR(s); error_bdev: close_bdev_exclusive(bdev, mode); error: return error; } EXPORT_SYMBOL(get_sb_bdev); void kill_block_super(struct super_block *sb) { struct block_device *bdev = sb->s_bdev; fmode_t mode = sb->s_mode; bdev->bd_super = NULL; generic_shutdown_super(sb); sync_blockdev(bdev); close_bdev_exclusive(bdev, mode); } EXPORT_SYMBOL(kill_block_super); #endif int get_sb_nodev(struct file_system_type *fs_type, int flags, void *data, int (*fill_super)(struct super_block *, void *, int), struct vfsmount *mnt) { int error; struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL); if (IS_ERR(s)) return PTR_ERR(s); s->s_flags = flags; error = fill_super(s, data, flags & MS_SILENT ? 1 : 0); if (error) { deactivate_locked_super(s); return error; } s->s_flags |= MS_ACTIVE; simple_set_mnt(mnt, s); return 0; } EXPORT_SYMBOL(get_sb_nodev); static int compare_single(struct super_block *s, void *p) { return 1; } int get_sb_single(struct file_system_type *fs_type, int flags, void *data, int (*fill_super)(struct super_block *, void *, int), struct vfsmount *mnt) { struct super_block *s; int error; s = sget(fs_type, compare_single, set_anon_super, NULL); if (IS_ERR(s)) return PTR_ERR(s); if (!s->s_root) { s->s_flags = flags; error = fill_super(s, data, flags & MS_SILENT ? 1 : 0); if (error) { deactivate_locked_super(s); return error; } s->s_flags |= MS_ACTIVE; } do_remount_sb(s, flags, data, 0); simple_set_mnt(mnt, s); return 0; } EXPORT_SYMBOL(get_sb_single); struct vfsmount * vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data) { struct vfsmount *mnt; char *secdata = NULL; int error; if (!type) return ERR_PTR(-ENODEV); error = -ENOMEM; mnt = alloc_vfsmnt(name); if (!mnt) goto out; if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) { secdata = alloc_secdata(); if (!secdata) goto out_mnt; error = security_sb_copy_data(data, secdata); if (error) goto out_free_secdata; } error = type->get_sb(type, flags, name, data, mnt); if (error < 0) goto out_free_secdata; BUG_ON(!mnt->mnt_sb); error = security_sb_kern_mount(mnt->mnt_sb, flags, secdata); if (error) goto out_sb; mnt->mnt_mountpoint = mnt->mnt_root; mnt->mnt_parent = mnt; up_write(&mnt->mnt_sb->s_umount); free_secdata(secdata); return mnt; out_sb: dput(mnt->mnt_root); deactivate_locked_super(mnt->mnt_sb); out_free_secdata: free_secdata(secdata); out_mnt: free_vfsmnt(mnt); out: return ERR_PTR(error); } EXPORT_SYMBOL_GPL(vfs_kern_mount); static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype) { int err; const char *subtype = strchr(fstype, '.'); if (subtype) { subtype++; err = -EINVAL; if (!subtype[0]) goto err; } else subtype = ""; mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL); err = -ENOMEM; if (!mnt->mnt_sb->s_subtype) goto err; return mnt; err: mntput(mnt); return ERR_PTR(err); } 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 vfsmount *mnt; if (!type) return ERR_PTR(-ENODEV); mnt = vfs_kern_mount(type, flags, name, data); if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && !mnt->mnt_sb->s_subtype) mnt = fs_set_subtype(mnt, fstype); put_filesystem(type); return mnt; } EXPORT_SYMBOL_GPL(do_kern_mount); struct vfsmount *kern_mount_data(struct file_system_type *type, void *data) { return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data); } EXPORT_SYMBOL_GPL(kern_mount_data);