/* * 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: * Torbj�rn 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 <linux/mutex.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 = kzalloc(sizeof(struct super_block), GFP_USER); static struct super_operations default_op; if (s) { 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_sb(sb); 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 DEFINE_MUTEX(mutex); mutex_lock(&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); mutex_unlock(&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->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; } /** * 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); } } 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; int error = 0; bdev = open_bdev_excl(dev_name, flags, 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 */ 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 error_s; if (s->s_root) { if ((flags ^ s->s_flags) & MS_RDONLY) { up_write(&s->s_umount); deactivate_super(s); error = -EBUSY; goto error_bdev; } close_bdev_excl(bdev); } 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_SILENT ? 1 : 0); if (error) { up_write(&s->s_umount); deactivate_super(s); goto error; } s->s_flags |= MS_ACTIVE; bdev_uevent(bdev, KOBJ_MOUNT); } return simple_set_mnt(mnt, s); error_s: error = PTR_ERR(s); error_bdev: close_bdev_excl(bdev); error: return error; } 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); 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) { up_write(&s->s_umount); deactivate_super(s); return error; } s->s_flags |= MS_ACTIVE; return simple_set_mnt(mnt, s); } 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) { up_write(&s->s_umount); deactivate_super(s); return error; } s->s_flags |= MS_ACTIVE; } do_remount_sb(s, flags, data, 0); return simple_set_mnt(mnt, s); } 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) { secdata = alloc_secdata(); if (!secdata) goto out_mnt; error = security_sb_copy_data(type, data, secdata); if (error) goto out_free_secdata; } error = type->get_sb(type, flags, name, data, mnt); if (error < 0) goto out_free_secdata; error = security_sb_kern_mount(mnt->mnt_sb, 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); up_write(&mnt->mnt_sb->s_umount); deactivate_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); 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); put_filesystem(type); return mnt; } EXPORT_SYMBOL_GPL(do_kern_mount); struct vfsmount *kern_mount(struct file_system_type *type) { return vfs_kern_mount(type, 0, type->name, NULL); } EXPORT_SYMBOL(kern_mount);