Root/fs/super.c

1/*
2 * linux/fs/super.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 *
6 * super.c contains code to handle: - mount structures
7 * - super-block tables
8 * - filesystem drivers list
9 * - mount system call
10 * - umount system call
11 * - ustat system call
12 *
13 * GK 2/5/95 - Changed to support mounting the root fs via NFS
14 *
15 * Added kerneld support: Jacques Gelinas and Bjorn Ekwall
16 * Added change_root: Werner Almesberger & Hans Lermen, Feb '96
17 * Added options to /proc/mounts:
18 * Torbj√∂rn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
19 * Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998
20 * Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000
21 */
22
23#include <linux/module.h>
24#include <linux/slab.h>
25#include <linux/init.h>
26#include <linux/smp_lock.h>
27#include <linux/acct.h>
28#include <linux/blkdev.h>
29#include <linux/quotaops.h>
30#include <linux/namei.h>
31#include <linux/mount.h>
32#include <linux/security.h>
33#include <linux/syscalls.h>
34#include <linux/vfs.h>
35#include <linux/writeback.h> /* for the emergency remount stuff */
36#include <linux/idr.h>
37#include <linux/kobject.h>
38#include <linux/mutex.h>
39#include <linux/file.h>
40#include <asm/uaccess.h>
41#include "internal.h"
42
43
44LIST_HEAD(super_blocks);
45DEFINE_SPINLOCK(sb_lock);
46
47/**
48 * alloc_super - create new superblock
49 * @type: filesystem type superblock should belong to
50 *
51 * Allocates and initializes a new &struct super_block. alloc_super()
52 * returns a pointer new superblock or %NULL if allocation had failed.
53 */
54static struct super_block *alloc_super(struct file_system_type *type)
55{
56    struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER);
57    static struct super_operations default_op;
58
59    if (s) {
60        if (security_sb_alloc(s)) {
61            kfree(s);
62            s = NULL;
63            goto out;
64        }
65        INIT_LIST_HEAD(&s->s_dirty);
66        INIT_LIST_HEAD(&s->s_io);
67        INIT_LIST_HEAD(&s->s_more_io);
68        INIT_LIST_HEAD(&s->s_files);
69        INIT_LIST_HEAD(&s->s_instances);
70        INIT_HLIST_HEAD(&s->s_anon);
71        INIT_LIST_HEAD(&s->s_inodes);
72        INIT_LIST_HEAD(&s->s_dentry_lru);
73        init_rwsem(&s->s_umount);
74        mutex_init(&s->s_lock);
75        lockdep_set_class(&s->s_umount, &type->s_umount_key);
76        /*
77         * The locking rules for s_lock are up to the
78         * filesystem. For example ext3fs has different
79         * lock ordering than usbfs:
80         */
81        lockdep_set_class(&s->s_lock, &type->s_lock_key);
82        /*
83         * sget() can have s_umount recursion.
84         *
85         * When it cannot find a suitable sb, it allocates a new
86         * one (this one), and tries again to find a suitable old
87         * one.
88         *
89         * In case that succeeds, it will acquire the s_umount
90         * lock of the old one. Since these are clearly distrinct
91         * locks, and this object isn't exposed yet, there's no
92         * risk of deadlocks.
93         *
94         * Annotate this by putting this lock in a different
95         * subclass.
96         */
97        down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
98        s->s_count = S_BIAS;
99        atomic_set(&s->s_active, 1);
100        mutex_init(&s->s_vfs_rename_mutex);
101        mutex_init(&s->s_dquot.dqio_mutex);
102        mutex_init(&s->s_dquot.dqonoff_mutex);
103        init_rwsem(&s->s_dquot.dqptr_sem);
104        init_waitqueue_head(&s->s_wait_unfrozen);
105        s->s_maxbytes = MAX_NON_LFS;
106        s->dq_op = sb_dquot_ops;
107        s->s_qcop = sb_quotactl_ops;
108        s->s_op = &default_op;
109        s->s_time_gran = 1000000000;
110    }
111out:
112    return s;
113}
114
115/**
116 * destroy_super - frees a superblock
117 * @s: superblock to free
118 *
119 * Frees a superblock.
120 */
121static inline void destroy_super(struct super_block *s)
122{
123    security_sb_free(s);
124    kfree(s->s_subtype);
125    kfree(s->s_options);
126    kfree(s);
127}
128
129/* Superblock refcounting */
130
131/*
132 * Drop a superblock's refcount. Returns non-zero if the superblock was
133 * destroyed. The caller must hold sb_lock.
134 */
135static int __put_super(struct super_block *sb)
136{
137    int ret = 0;
138
139    if (!--sb->s_count) {
140        destroy_super(sb);
141        ret = 1;
142    }
143    return ret;
144}
145
146/*
147 * Drop a superblock's refcount.
148 * Returns non-zero if the superblock is about to be destroyed and
149 * at least is already removed from super_blocks list, so if we are
150 * making a loop through super blocks then we need to restart.
151 * The caller must hold sb_lock.
152 */
153int __put_super_and_need_restart(struct super_block *sb)
154{
155    /* check for race with generic_shutdown_super() */
156    if (list_empty(&sb->s_list)) {
157        /* super block is removed, need to restart... */
158        __put_super(sb);
159        return 1;
160    }
161    /* can't be the last, since s_list is still in use */
162    sb->s_count--;
163    BUG_ON(sb->s_count == 0);
164    return 0;
165}
166
167/**
168 * put_super - drop a temporary reference to superblock
169 * @sb: superblock in question
170 *
171 * Drops a temporary reference, frees superblock if there's no
172 * references left.
173 */
174static void put_super(struct super_block *sb)
175{
176    spin_lock(&sb_lock);
177    __put_super(sb);
178    spin_unlock(&sb_lock);
179}
180
181
182/**
183 * deactivate_super - drop an active reference to superblock
184 * @s: superblock to deactivate
185 *
186 * Drops an active reference to superblock, acquiring a temprory one if
187 * there is no active references left. In that case we lock superblock,
188 * tell fs driver to shut it down and drop the temporary reference we
189 * had just acquired.
190 */
191void deactivate_super(struct super_block *s)
192{
193    struct file_system_type *fs = s->s_type;
194    if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
195        s->s_count -= S_BIAS-1;
196        spin_unlock(&sb_lock);
197        vfs_dq_off(s, 0);
198        down_write(&s->s_umount);
199        fs->kill_sb(s);
200        put_filesystem(fs);
201        put_super(s);
202    }
203}
204
205EXPORT_SYMBOL(deactivate_super);
206
207/**
208 * deactivate_locked_super - drop an active reference to superblock
209 * @s: superblock to deactivate
210 *
211 * Equivalent of up_write(&s->s_umount); deactivate_super(s);, except that
212 * it does not unlock it until it's all over. As the result, it's safe to
213 * use to dispose of new superblock on ->get_sb() failure exits - nobody
214 * will see the sucker until it's all over. Equivalent using up_write +
215 * deactivate_super is safe for that purpose only if superblock is either
216 * safe to use or has NULL ->s_root when we unlock.
217 */
218void deactivate_locked_super(struct super_block *s)
219{
220    struct file_system_type *fs = s->s_type;
221    if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
222        s->s_count -= S_BIAS-1;
223        spin_unlock(&sb_lock);
224        vfs_dq_off(s, 0);
225        fs->kill_sb(s);
226        put_filesystem(fs);
227        put_super(s);
228    } else {
229        up_write(&s->s_umount);
230    }
231}
232
233EXPORT_SYMBOL(deactivate_locked_super);
234
235/**
236 * grab_super - acquire an active reference
237 * @s: reference we are trying to make active
238 *
239 * Tries to acquire an active reference. grab_super() is used when we
240 * had just found a superblock in super_blocks or fs_type->fs_supers
241 * and want to turn it into a full-blown active reference. grab_super()
242 * is called with sb_lock held and drops it. Returns 1 in case of
243 * success, 0 if we had failed (superblock contents was already dead or
244 * dying when grab_super() had been called).
245 */
246static int grab_super(struct super_block *s) __releases(sb_lock)
247{
248    s->s_count++;
249    spin_unlock(&sb_lock);
250    down_write(&s->s_umount);
251    if (s->s_root) {
252        spin_lock(&sb_lock);
253        if (s->s_count > S_BIAS) {
254            atomic_inc(&s->s_active);
255            s->s_count--;
256            spin_unlock(&sb_lock);
257            return 1;
258        }
259        spin_unlock(&sb_lock);
260    }
261    up_write(&s->s_umount);
262    put_super(s);
263    yield();
264    return 0;
265}
266
267/*
268 * Superblock locking. We really ought to get rid of these two.
269 */
270void lock_super(struct super_block * sb)
271{
272    get_fs_excl();
273    mutex_lock(&sb->s_lock);
274}
275
276void unlock_super(struct super_block * sb)
277{
278    put_fs_excl();
279    mutex_unlock(&sb->s_lock);
280}
281
282EXPORT_SYMBOL(lock_super);
283EXPORT_SYMBOL(unlock_super);
284
285/**
286 * generic_shutdown_super - common helper for ->kill_sb()
287 * @sb: superblock to kill
288 *
289 * generic_shutdown_super() does all fs-independent work on superblock
290 * shutdown. Typical ->kill_sb() should pick all fs-specific objects
291 * that need destruction out of superblock, call generic_shutdown_super()
292 * and release aforementioned objects. Note: dentries and inodes _are_
293 * taken care of and do not need specific handling.
294 *
295 * Upon calling this function, the filesystem may no longer alter or
296 * rearrange the set of dentries belonging to this super_block, nor may it
297 * change the attachments of dentries to inodes.
298 */
299void generic_shutdown_super(struct super_block *sb)
300{
301    const struct super_operations *sop = sb->s_op;
302
303
304    if (sb->s_root) {
305        shrink_dcache_for_umount(sb);
306        sync_filesystem(sb);
307        get_fs_excl();
308        sb->s_flags &= ~MS_ACTIVE;
309
310        /* bad name - it should be evict_inodes() */
311        invalidate_inodes(sb);
312
313        if (sop->put_super)
314            sop->put_super(sb);
315
316        /* Forget any remaining inodes */
317        if (invalidate_inodes(sb)) {
318            printk("VFS: Busy inodes after unmount of %s. "
319               "Self-destruct in 5 seconds. Have a nice day...\n",
320               sb->s_id);
321        }
322        put_fs_excl();
323    }
324    spin_lock(&sb_lock);
325    /* should be initialized for __put_super_and_need_restart() */
326    list_del_init(&sb->s_list);
327    list_del(&sb->s_instances);
328    spin_unlock(&sb_lock);
329    up_write(&sb->s_umount);
330}
331
332EXPORT_SYMBOL(generic_shutdown_super);
333
334/**
335 * sget - find or create a superblock
336 * @type: filesystem type superblock should belong to
337 * @test: comparison callback
338 * @set: setup callback
339 * @data: argument to each of them
340 */
341struct super_block *sget(struct file_system_type *type,
342            int (*test)(struct super_block *,void *),
343            int (*set)(struct super_block *,void *),
344            void *data)
345{
346    struct super_block *s = NULL;
347    struct super_block *old;
348    int err;
349
350retry:
351    spin_lock(&sb_lock);
352    if (test) {
353        list_for_each_entry(old, &type->fs_supers, s_instances) {
354            if (!test(old, data))
355                continue;
356            if (!grab_super(old))
357                goto retry;
358            if (s) {
359                up_write(&s->s_umount);
360                destroy_super(s);
361            }
362            return old;
363        }
364    }
365    if (!s) {
366        spin_unlock(&sb_lock);
367        s = alloc_super(type);
368        if (!s)
369            return ERR_PTR(-ENOMEM);
370        goto retry;
371    }
372        
373    err = set(s, data);
374    if (err) {
375        spin_unlock(&sb_lock);
376        up_write(&s->s_umount);
377        destroy_super(s);
378        return ERR_PTR(err);
379    }
380    s->s_type = type;
381    strlcpy(s->s_id, type->name, sizeof(s->s_id));
382    list_add_tail(&s->s_list, &super_blocks);
383    list_add(&s->s_instances, &type->fs_supers);
384    spin_unlock(&sb_lock);
385    get_filesystem(type);
386    return s;
387}
388
389EXPORT_SYMBOL(sget);
390
391void drop_super(struct super_block *sb)
392{
393    up_read(&sb->s_umount);
394    put_super(sb);
395}
396
397EXPORT_SYMBOL(drop_super);
398
399/**
400 * sync_supers - helper for periodic superblock writeback
401 *
402 * Call the write_super method if present on all dirty superblocks in
403 * the system. This is for the periodic writeback used by most older
404 * filesystems. For data integrity superblock writeback use
405 * sync_filesystems() instead.
406 *
407 * Note: check the dirty flag before waiting, so we don't
408 * hold up the sync while mounting a device. (The newly
409 * mounted device won't need syncing.)
410 */
411void sync_supers(void)
412{
413    struct super_block *sb;
414
415    spin_lock(&sb_lock);
416restart:
417    list_for_each_entry(sb, &super_blocks, s_list) {
418        if (sb->s_op->write_super && sb->s_dirt) {
419            sb->s_count++;
420            spin_unlock(&sb_lock);
421
422            down_read(&sb->s_umount);
423            if (sb->s_root && sb->s_dirt)
424                sb->s_op->write_super(sb);
425            up_read(&sb->s_umount);
426
427            spin_lock(&sb_lock);
428            if (__put_super_and_need_restart(sb))
429                goto restart;
430        }
431    }
432    spin_unlock(&sb_lock);
433}
434
435/**
436 * get_super - get the superblock of a device
437 * @bdev: device to get the superblock for
438 *
439 * Scans the superblock list and finds the superblock of the file system
440 * mounted on the device given. %NULL is returned if no match is found.
441 */
442
443struct super_block * get_super(struct block_device *bdev)
444{
445    struct super_block *sb;
446
447    if (!bdev)
448        return NULL;
449
450    spin_lock(&sb_lock);
451rescan:
452    list_for_each_entry(sb, &super_blocks, s_list) {
453        if (sb->s_bdev == bdev) {
454            sb->s_count++;
455            spin_unlock(&sb_lock);
456            down_read(&sb->s_umount);
457            if (sb->s_root)
458                return sb;
459            up_read(&sb->s_umount);
460            /* restart only when sb is no longer on the list */
461            spin_lock(&sb_lock);
462            if (__put_super_and_need_restart(sb))
463                goto rescan;
464        }
465    }
466    spin_unlock(&sb_lock);
467    return NULL;
468}
469
470EXPORT_SYMBOL(get_super);
471 
472struct super_block * user_get_super(dev_t dev)
473{
474    struct super_block *sb;
475
476    spin_lock(&sb_lock);
477rescan:
478    list_for_each_entry(sb, &super_blocks, s_list) {
479        if (sb->s_dev == dev) {
480            sb->s_count++;
481            spin_unlock(&sb_lock);
482            down_read(&sb->s_umount);
483            if (sb->s_root)
484                return sb;
485            up_read(&sb->s_umount);
486            /* restart only when sb is no longer on the list */
487            spin_lock(&sb_lock);
488            if (__put_super_and_need_restart(sb))
489                goto rescan;
490        }
491    }
492    spin_unlock(&sb_lock);
493    return NULL;
494}
495
496SYSCALL_DEFINE2(ustat, unsigned, dev, struct ustat __user *, ubuf)
497{
498        struct super_block *s;
499        struct ustat tmp;
500        struct kstatfs sbuf;
501    int err = -EINVAL;
502
503        s = user_get_super(new_decode_dev(dev));
504        if (s == NULL)
505                goto out;
506    err = vfs_statfs(s->s_root, &sbuf);
507    drop_super(s);
508    if (err)
509        goto out;
510
511        memset(&tmp,0,sizeof(struct ustat));
512        tmp.f_tfree = sbuf.f_bfree;
513        tmp.f_tinode = sbuf.f_ffree;
514
515        err = copy_to_user(ubuf,&tmp,sizeof(struct ustat)) ? -EFAULT : 0;
516out:
517    return err;
518}
519
520/**
521 * do_remount_sb - asks filesystem to change mount options.
522 * @sb: superblock in question
523 * @flags: numeric part of options
524 * @data: the rest of options
525 * @force: whether or not to force the change
526 *
527 * Alters the mount options of a mounted file system.
528 */
529int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
530{
531    int retval;
532    int remount_rw;
533    
534#ifdef CONFIG_BLOCK
535    if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
536        return -EACCES;
537#endif
538    if (flags & MS_RDONLY)
539        acct_auto_close(sb);
540    shrink_dcache_sb(sb);
541    sync_filesystem(sb);
542
543    /* If we are remounting RDONLY and current sb is read/write,
544       make sure there are no rw files opened */
545    if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) {
546        if (force)
547            mark_files_ro(sb);
548        else if (!fs_may_remount_ro(sb))
549            return -EBUSY;
550        retval = vfs_dq_off(sb, 1);
551        if (retval < 0 && retval != -ENOSYS)
552            return -EBUSY;
553    }
554    remount_rw = !(flags & MS_RDONLY) && (sb->s_flags & MS_RDONLY);
555
556    if (sb->s_op->remount_fs) {
557        retval = sb->s_op->remount_fs(sb, &flags, data);
558        if (retval)
559            return retval;
560    }
561    sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
562    if (remount_rw)
563        vfs_dq_quota_on_remount(sb);
564    return 0;
565}
566
567static void do_emergency_remount(struct work_struct *work)
568{
569    struct super_block *sb;
570
571    spin_lock(&sb_lock);
572    list_for_each_entry(sb, &super_blocks, s_list) {
573        sb->s_count++;
574        spin_unlock(&sb_lock);
575        down_write(&sb->s_umount);
576        if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
577            /*
578             * ->remount_fs needs lock_kernel().
579             *
580             * What lock protects sb->s_flags??
581             */
582            do_remount_sb(sb, MS_RDONLY, NULL, 1);
583        }
584        up_write(&sb->s_umount);
585        put_super(sb);
586        spin_lock(&sb_lock);
587    }
588    spin_unlock(&sb_lock);
589    kfree(work);
590    printk("Emergency Remount complete\n");
591}
592
593void emergency_remount(void)
594{
595    struct work_struct *work;
596
597    work = kmalloc(sizeof(*work), GFP_ATOMIC);
598    if (work) {
599        INIT_WORK(work, do_emergency_remount);
600        schedule_work(work);
601    }
602}
603
604/*
605 * Unnamed block devices are dummy devices used by virtual
606 * filesystems which don't use real block-devices. -- jrs
607 */
608
609static DEFINE_IDA(unnamed_dev_ida);
610static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
611static int unnamed_dev_start = 0; /* don't bother trying below it */
612
613int set_anon_super(struct super_block *s, void *data)
614{
615    int dev;
616    int error;
617
618 retry:
619    if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0)
620        return -ENOMEM;
621    spin_lock(&unnamed_dev_lock);
622    error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev);
623    if (!error)
624        unnamed_dev_start = dev + 1;
625    spin_unlock(&unnamed_dev_lock);
626    if (error == -EAGAIN)
627        /* We raced and lost with another CPU. */
628        goto retry;
629    else if (error)
630        return -EAGAIN;
631
632    if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
633        spin_lock(&unnamed_dev_lock);
634        ida_remove(&unnamed_dev_ida, dev);
635        if (unnamed_dev_start > dev)
636            unnamed_dev_start = dev;
637        spin_unlock(&unnamed_dev_lock);
638        return -EMFILE;
639    }
640    s->s_dev = MKDEV(0, dev & MINORMASK);
641    return 0;
642}
643
644EXPORT_SYMBOL(set_anon_super);
645
646void kill_anon_super(struct super_block *sb)
647{
648    int slot = MINOR(sb->s_dev);
649
650    generic_shutdown_super(sb);
651    spin_lock(&unnamed_dev_lock);
652    ida_remove(&unnamed_dev_ida, slot);
653    if (slot < unnamed_dev_start)
654        unnamed_dev_start = slot;
655    spin_unlock(&unnamed_dev_lock);
656}
657
658EXPORT_SYMBOL(kill_anon_super);
659
660void kill_litter_super(struct super_block *sb)
661{
662    if (sb->s_root)
663        d_genocide(sb->s_root);
664    kill_anon_super(sb);
665}
666
667EXPORT_SYMBOL(kill_litter_super);
668
669static int ns_test_super(struct super_block *sb, void *data)
670{
671    return sb->s_fs_info == data;
672}
673
674static int ns_set_super(struct super_block *sb, void *data)
675{
676    sb->s_fs_info = data;
677    return set_anon_super(sb, NULL);
678}
679
680int get_sb_ns(struct file_system_type *fs_type, int flags, void *data,
681    int (*fill_super)(struct super_block *, void *, int),
682    struct vfsmount *mnt)
683{
684    struct super_block *sb;
685
686    sb = sget(fs_type, ns_test_super, ns_set_super, data);
687    if (IS_ERR(sb))
688        return PTR_ERR(sb);
689
690    if (!sb->s_root) {
691        int err;
692        sb->s_flags = flags;
693        err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
694        if (err) {
695            deactivate_locked_super(sb);
696            return err;
697        }
698
699        sb->s_flags |= MS_ACTIVE;
700    }
701
702    simple_set_mnt(mnt, sb);
703    return 0;
704}
705
706EXPORT_SYMBOL(get_sb_ns);
707
708#ifdef CONFIG_BLOCK
709static int set_bdev_super(struct super_block *s, void *data)
710{
711    s->s_bdev = data;
712    s->s_dev = s->s_bdev->bd_dev;
713    return 0;
714}
715
716static int test_bdev_super(struct super_block *s, void *data)
717{
718    return (void *)s->s_bdev == data;
719}
720
721int get_sb_bdev(struct file_system_type *fs_type,
722    int flags, const char *dev_name, void *data,
723    int (*fill_super)(struct super_block *, void *, int),
724    struct vfsmount *mnt)
725{
726    struct block_device *bdev;
727    struct super_block *s;
728    fmode_t mode = FMODE_READ;
729    int error = 0;
730
731    if (!(flags & MS_RDONLY))
732        mode |= FMODE_WRITE;
733
734    bdev = open_bdev_exclusive(dev_name, mode, fs_type);
735    if (IS_ERR(bdev))
736        return PTR_ERR(bdev);
737
738    /*
739     * once the super is inserted into the list by sget, s_umount
740     * will protect the lockfs code from trying to start a snapshot
741     * while we are mounting
742     */
743    down(&bdev->bd_mount_sem);
744    s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
745    up(&bdev->bd_mount_sem);
746    if (IS_ERR(s))
747        goto error_s;
748
749    if (s->s_root) {
750        if ((flags ^ s->s_flags) & MS_RDONLY) {
751            deactivate_locked_super(s);
752            error = -EBUSY;
753            goto error_bdev;
754        }
755
756        close_bdev_exclusive(bdev, mode);
757    } else {
758        char b[BDEVNAME_SIZE];
759
760        s->s_flags = flags;
761        s->s_mode = mode;
762        strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
763        sb_set_blocksize(s, block_size(bdev));
764        error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
765        if (error) {
766            deactivate_locked_super(s);
767            goto error;
768        }
769
770        s->s_flags |= MS_ACTIVE;
771        bdev->bd_super = s;
772    }
773
774    simple_set_mnt(mnt, s);
775    return 0;
776
777error_s:
778    error = PTR_ERR(s);
779error_bdev:
780    close_bdev_exclusive(bdev, mode);
781error:
782    return error;
783}
784
785EXPORT_SYMBOL(get_sb_bdev);
786
787void kill_block_super(struct super_block *sb)
788{
789    struct block_device *bdev = sb->s_bdev;
790    fmode_t mode = sb->s_mode;
791
792    bdev->bd_super = NULL;
793    generic_shutdown_super(sb);
794    sync_blockdev(bdev);
795    close_bdev_exclusive(bdev, mode);
796}
797
798EXPORT_SYMBOL(kill_block_super);
799#endif
800
801int get_sb_nodev(struct file_system_type *fs_type,
802    int flags, void *data,
803    int (*fill_super)(struct super_block *, void *, int),
804    struct vfsmount *mnt)
805{
806    int error;
807    struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
808
809    if (IS_ERR(s))
810        return PTR_ERR(s);
811
812    s->s_flags = flags;
813
814    error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
815    if (error) {
816        deactivate_locked_super(s);
817        return error;
818    }
819    s->s_flags |= MS_ACTIVE;
820    simple_set_mnt(mnt, s);
821    return 0;
822}
823
824EXPORT_SYMBOL(get_sb_nodev);
825
826static int compare_single(struct super_block *s, void *p)
827{
828    return 1;
829}
830
831int get_sb_single(struct file_system_type *fs_type,
832    int flags, void *data,
833    int (*fill_super)(struct super_block *, void *, int),
834    struct vfsmount *mnt)
835{
836    struct super_block *s;
837    int error;
838
839    s = sget(fs_type, compare_single, set_anon_super, NULL);
840    if (IS_ERR(s))
841        return PTR_ERR(s);
842    if (!s->s_root) {
843        s->s_flags = flags;
844        error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
845        if (error) {
846            deactivate_locked_super(s);
847            return error;
848        }
849        s->s_flags |= MS_ACTIVE;
850    }
851    do_remount_sb(s, flags, data, 0);
852    simple_set_mnt(mnt, s);
853    return 0;
854}
855
856EXPORT_SYMBOL(get_sb_single);
857
858struct vfsmount *
859vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
860{
861    struct vfsmount *mnt;
862    char *secdata = NULL;
863    int error;
864
865    if (!type)
866        return ERR_PTR(-ENODEV);
867
868    error = -ENOMEM;
869    mnt = alloc_vfsmnt(name);
870    if (!mnt)
871        goto out;
872
873    if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) {
874        secdata = alloc_secdata();
875        if (!secdata)
876            goto out_mnt;
877
878        error = security_sb_copy_data(data, secdata);
879        if (error)
880            goto out_free_secdata;
881    }
882
883    error = type->get_sb(type, flags, name, data, mnt);
884    if (error < 0)
885        goto out_free_secdata;
886    BUG_ON(!mnt->mnt_sb);
887
888     error = security_sb_kern_mount(mnt->mnt_sb, flags, secdata);
889     if (error)
890         goto out_sb;
891
892    mnt->mnt_mountpoint = mnt->mnt_root;
893    mnt->mnt_parent = mnt;
894    up_write(&mnt->mnt_sb->s_umount);
895    free_secdata(secdata);
896    return mnt;
897out_sb:
898    dput(mnt->mnt_root);
899    deactivate_locked_super(mnt->mnt_sb);
900out_free_secdata:
901    free_secdata(secdata);
902out_mnt:
903    free_vfsmnt(mnt);
904out:
905    return ERR_PTR(error);
906}
907
908EXPORT_SYMBOL_GPL(vfs_kern_mount);
909
910static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
911{
912    int err;
913    const char *subtype = strchr(fstype, '.');
914    if (subtype) {
915        subtype++;
916        err = -EINVAL;
917        if (!subtype[0])
918            goto err;
919    } else
920        subtype = "";
921
922    mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
923    err = -ENOMEM;
924    if (!mnt->mnt_sb->s_subtype)
925        goto err;
926    return mnt;
927
928 err:
929    mntput(mnt);
930    return ERR_PTR(err);
931}
932
933struct vfsmount *
934do_kern_mount(const char *fstype, int flags, const char *name, void *data)
935{
936    struct file_system_type *type = get_fs_type(fstype);
937    struct vfsmount *mnt;
938    if (!type)
939        return ERR_PTR(-ENODEV);
940    mnt = vfs_kern_mount(type, flags, name, data);
941    if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
942        !mnt->mnt_sb->s_subtype)
943        mnt = fs_set_subtype(mnt, fstype);
944    put_filesystem(type);
945    return mnt;
946}
947EXPORT_SYMBOL_GPL(do_kern_mount);
948
949struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
950{
951    return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
952}
953
954EXPORT_SYMBOL_GPL(kern_mount_data);
955

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