Root/fs/libfs.c

1/*
2 * fs/libfs.c
3 * Library for filesystems writers.
4 */
5
6#include <linux/module.h>
7#include <linux/pagemap.h>
8#include <linux/mount.h>
9#include <linux/vfs.h>
10#include <linux/mutex.h>
11#include <linux/exportfs.h>
12#include <linux/writeback.h>
13#include <linux/buffer_head.h>
14
15#include <asm/uaccess.h>
16
17int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
18           struct kstat *stat)
19{
20    struct inode *inode = dentry->d_inode;
21    generic_fillattr(inode, stat);
22    stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9);
23    return 0;
24}
25
26int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
27{
28    buf->f_type = dentry->d_sb->s_magic;
29    buf->f_bsize = PAGE_CACHE_SIZE;
30    buf->f_namelen = NAME_MAX;
31    return 0;
32}
33
34/*
35 * Retaining negative dentries for an in-memory filesystem just wastes
36 * memory and lookup time: arrange for them to be deleted immediately.
37 */
38static int simple_delete_dentry(struct dentry *dentry)
39{
40    return 1;
41}
42
43/*
44 * Lookup the data. This is trivial - if the dentry didn't already
45 * exist, we know it is negative. Set d_op to delete negative dentries.
46 */
47struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
48{
49    static const struct dentry_operations simple_dentry_operations = {
50        .d_delete = simple_delete_dentry,
51    };
52
53    if (dentry->d_name.len > NAME_MAX)
54        return ERR_PTR(-ENAMETOOLONG);
55    dentry->d_op = &simple_dentry_operations;
56    d_add(dentry, NULL);
57    return NULL;
58}
59
60int simple_sync_file(struct file * file, struct dentry *dentry, int datasync)
61{
62    return 0;
63}
64 
65int dcache_dir_open(struct inode *inode, struct file *file)
66{
67    static struct qstr cursor_name = {.len = 1, .name = "."};
68
69    file->private_data = d_alloc(file->f_path.dentry, &cursor_name);
70
71    return file->private_data ? 0 : -ENOMEM;
72}
73
74int dcache_dir_close(struct inode *inode, struct file *file)
75{
76    dput(file->private_data);
77    return 0;
78}
79
80loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
81{
82    mutex_lock(&file->f_path.dentry->d_inode->i_mutex);
83    switch (origin) {
84        case 1:
85            offset += file->f_pos;
86        case 0:
87            if (offset >= 0)
88                break;
89        default:
90            mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
91            return -EINVAL;
92    }
93    if (offset != file->f_pos) {
94        file->f_pos = offset;
95        if (file->f_pos >= 2) {
96            struct list_head *p;
97            struct dentry *cursor = file->private_data;
98            loff_t n = file->f_pos - 2;
99
100            spin_lock(&dcache_lock);
101            list_del(&cursor->d_u.d_child);
102            p = file->f_path.dentry->d_subdirs.next;
103            while (n && p != &file->f_path.dentry->d_subdirs) {
104                struct dentry *next;
105                next = list_entry(p, struct dentry, d_u.d_child);
106                if (!d_unhashed(next) && next->d_inode)
107                    n--;
108                p = p->next;
109            }
110            list_add_tail(&cursor->d_u.d_child, p);
111            spin_unlock(&dcache_lock);
112        }
113    }
114    mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
115    return offset;
116}
117
118/* Relationship between i_mode and the DT_xxx types */
119static inline unsigned char dt_type(struct inode *inode)
120{
121    return (inode->i_mode >> 12) & 15;
122}
123
124/*
125 * Directory is locked and all positive dentries in it are safe, since
126 * for ramfs-type trees they can't go away without unlink() or rmdir(),
127 * both impossible due to the lock on directory.
128 */
129
130int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
131{
132    struct dentry *dentry = filp->f_path.dentry;
133    struct dentry *cursor = filp->private_data;
134    struct list_head *p, *q = &cursor->d_u.d_child;
135    ino_t ino;
136    int i = filp->f_pos;
137
138    switch (i) {
139        case 0:
140            ino = dentry->d_inode->i_ino;
141            if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
142                break;
143            filp->f_pos++;
144            i++;
145            /* fallthrough */
146        case 1:
147            ino = parent_ino(dentry);
148            if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
149                break;
150            filp->f_pos++;
151            i++;
152            /* fallthrough */
153        default:
154            spin_lock(&dcache_lock);
155            if (filp->f_pos == 2)
156                list_move(q, &dentry->d_subdirs);
157
158            for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
159                struct dentry *next;
160                next = list_entry(p, struct dentry, d_u.d_child);
161                if (d_unhashed(next) || !next->d_inode)
162                    continue;
163
164                spin_unlock(&dcache_lock);
165                if (filldir(dirent, next->d_name.name,
166                        next->d_name.len, filp->f_pos,
167                        next->d_inode->i_ino,
168                        dt_type(next->d_inode)) < 0)
169                    return 0;
170                spin_lock(&dcache_lock);
171                /* next is still alive */
172                list_move(q, p);
173                p = q;
174                filp->f_pos++;
175            }
176            spin_unlock(&dcache_lock);
177    }
178    return 0;
179}
180
181ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
182{
183    return -EISDIR;
184}
185
186const struct file_operations simple_dir_operations = {
187    .open = dcache_dir_open,
188    .release = dcache_dir_close,
189    .llseek = dcache_dir_lseek,
190    .read = generic_read_dir,
191    .readdir = dcache_readdir,
192    .fsync = simple_sync_file,
193};
194
195const struct inode_operations simple_dir_inode_operations = {
196    .lookup = simple_lookup,
197};
198
199static const struct super_operations simple_super_operations = {
200    .statfs = simple_statfs,
201};
202
203/*
204 * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
205 * will never be mountable)
206 */
207int get_sb_pseudo(struct file_system_type *fs_type, char *name,
208    const struct super_operations *ops, unsigned long magic,
209    struct vfsmount *mnt)
210{
211    struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
212    struct dentry *dentry;
213    struct inode *root;
214    struct qstr d_name = {.name = name, .len = strlen(name)};
215
216    if (IS_ERR(s))
217        return PTR_ERR(s);
218
219    s->s_flags = MS_NOUSER;
220    s->s_maxbytes = MAX_LFS_FILESIZE;
221    s->s_blocksize = PAGE_SIZE;
222    s->s_blocksize_bits = PAGE_SHIFT;
223    s->s_magic = magic;
224    s->s_op = ops ? ops : &simple_super_operations;
225    s->s_time_gran = 1;
226    root = new_inode(s);
227    if (!root)
228        goto Enomem;
229    /*
230     * since this is the first inode, make it number 1. New inodes created
231     * after this must take care not to collide with it (by passing
232     * max_reserved of 1 to iunique).
233     */
234    root->i_ino = 1;
235    root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
236    root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
237    dentry = d_alloc(NULL, &d_name);
238    if (!dentry) {
239        iput(root);
240        goto Enomem;
241    }
242    dentry->d_sb = s;
243    dentry->d_parent = dentry;
244    d_instantiate(dentry, root);
245    s->s_root = dentry;
246    s->s_flags |= MS_ACTIVE;
247    simple_set_mnt(mnt, s);
248    return 0;
249
250Enomem:
251    deactivate_locked_super(s);
252    return -ENOMEM;
253}
254
255int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
256{
257    struct inode *inode = old_dentry->d_inode;
258
259    inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
260    inc_nlink(inode);
261    atomic_inc(&inode->i_count);
262    dget(dentry);
263    d_instantiate(dentry, inode);
264    return 0;
265}
266
267static inline int simple_positive(struct dentry *dentry)
268{
269    return dentry->d_inode && !d_unhashed(dentry);
270}
271
272int simple_empty(struct dentry *dentry)
273{
274    struct dentry *child;
275    int ret = 0;
276
277    spin_lock(&dcache_lock);
278    list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child)
279        if (simple_positive(child))
280            goto out;
281    ret = 1;
282out:
283    spin_unlock(&dcache_lock);
284    return ret;
285}
286
287int simple_unlink(struct inode *dir, struct dentry *dentry)
288{
289    struct inode *inode = dentry->d_inode;
290
291    inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
292    drop_nlink(inode);
293    dput(dentry);
294    return 0;
295}
296
297int simple_rmdir(struct inode *dir, struct dentry *dentry)
298{
299    if (!simple_empty(dentry))
300        return -ENOTEMPTY;
301
302    drop_nlink(dentry->d_inode);
303    simple_unlink(dir, dentry);
304    drop_nlink(dir);
305    return 0;
306}
307
308int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
309        struct inode *new_dir, struct dentry *new_dentry)
310{
311    struct inode *inode = old_dentry->d_inode;
312    int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);
313
314    if (!simple_empty(new_dentry))
315        return -ENOTEMPTY;
316
317    if (new_dentry->d_inode) {
318        simple_unlink(new_dir, new_dentry);
319        if (they_are_dirs)
320            drop_nlink(old_dir);
321    } else if (they_are_dirs) {
322        drop_nlink(old_dir);
323        inc_nlink(new_dir);
324    }
325
326    old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
327        new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;
328
329    return 0;
330}
331
332int simple_readpage(struct file *file, struct page *page)
333{
334    clear_highpage(page);
335    flush_dcache_page(page);
336    SetPageUptodate(page);
337    unlock_page(page);
338    return 0;
339}
340
341int simple_prepare_write(struct file *file, struct page *page,
342            unsigned from, unsigned to)
343{
344    if (!PageUptodate(page)) {
345        if (to - from != PAGE_CACHE_SIZE)
346            zero_user_segments(page,
347                0, from,
348                to, PAGE_CACHE_SIZE);
349    }
350    return 0;
351}
352
353int simple_write_begin(struct file *file, struct address_space *mapping,
354            loff_t pos, unsigned len, unsigned flags,
355            struct page **pagep, void **fsdata)
356{
357    struct page *page;
358    pgoff_t index;
359    unsigned from;
360
361    index = pos >> PAGE_CACHE_SHIFT;
362    from = pos & (PAGE_CACHE_SIZE - 1);
363
364    page = grab_cache_page_write_begin(mapping, index, flags);
365    if (!page)
366        return -ENOMEM;
367
368    *pagep = page;
369
370    return simple_prepare_write(file, page, from, from+len);
371}
372
373static int simple_commit_write(struct file *file, struct page *page,
374                   unsigned from, unsigned to)
375{
376    struct inode *inode = page->mapping->host;
377    loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
378
379    if (!PageUptodate(page))
380        SetPageUptodate(page);
381    /*
382     * No need to use i_size_read() here, the i_size
383     * cannot change under us because we hold the i_mutex.
384     */
385    if (pos > inode->i_size)
386        i_size_write(inode, pos);
387    set_page_dirty(page);
388    return 0;
389}
390
391int simple_write_end(struct file *file, struct address_space *mapping,
392            loff_t pos, unsigned len, unsigned copied,
393            struct page *page, void *fsdata)
394{
395    unsigned from = pos & (PAGE_CACHE_SIZE - 1);
396
397    /* zero the stale part of the page if we did a short copy */
398    if (copied < len) {
399        void *kaddr = kmap_atomic(page, KM_USER0);
400        memset(kaddr + from + copied, 0, len - copied);
401        flush_dcache_page(page);
402        kunmap_atomic(kaddr, KM_USER0);
403    }
404
405    simple_commit_write(file, page, from, from+copied);
406
407    unlock_page(page);
408    page_cache_release(page);
409
410    return copied;
411}
412
413/*
414 * the inodes created here are not hashed. If you use iunique to generate
415 * unique inode values later for this filesystem, then you must take care
416 * to pass it an appropriate max_reserved value to avoid collisions.
417 */
418int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files)
419{
420    struct inode *inode;
421    struct dentry *root;
422    struct dentry *dentry;
423    int i;
424
425    s->s_blocksize = PAGE_CACHE_SIZE;
426    s->s_blocksize_bits = PAGE_CACHE_SHIFT;
427    s->s_magic = magic;
428    s->s_op = &simple_super_operations;
429    s->s_time_gran = 1;
430
431    inode = new_inode(s);
432    if (!inode)
433        return -ENOMEM;
434    /*
435     * because the root inode is 1, the files array must not contain an
436     * entry at index 1
437     */
438    inode->i_ino = 1;
439    inode->i_mode = S_IFDIR | 0755;
440    inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
441    inode->i_op = &simple_dir_inode_operations;
442    inode->i_fop = &simple_dir_operations;
443    inode->i_nlink = 2;
444    root = d_alloc_root(inode);
445    if (!root) {
446        iput(inode);
447        return -ENOMEM;
448    }
449    for (i = 0; !files->name || files->name[0]; i++, files++) {
450        if (!files->name)
451            continue;
452
453        /* warn if it tries to conflict with the root inode */
454        if (unlikely(i == 1))
455            printk(KERN_WARNING "%s: %s passed in a files array"
456                "with an index of 1!\n", __func__,
457                s->s_type->name);
458
459        dentry = d_alloc_name(root, files->name);
460        if (!dentry)
461            goto out;
462        inode = new_inode(s);
463        if (!inode)
464            goto out;
465        inode->i_mode = S_IFREG | files->mode;
466        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
467        inode->i_fop = files->ops;
468        inode->i_ino = i;
469        d_add(dentry, inode);
470    }
471    s->s_root = root;
472    return 0;
473out:
474    d_genocide(root);
475    dput(root);
476    return -ENOMEM;
477}
478
479static DEFINE_SPINLOCK(pin_fs_lock);
480
481int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
482{
483    struct vfsmount *mnt = NULL;
484    spin_lock(&pin_fs_lock);
485    if (unlikely(!*mount)) {
486        spin_unlock(&pin_fs_lock);
487        mnt = vfs_kern_mount(type, 0, type->name, NULL);
488        if (IS_ERR(mnt))
489            return PTR_ERR(mnt);
490        spin_lock(&pin_fs_lock);
491        if (!*mount)
492            *mount = mnt;
493    }
494    mntget(*mount);
495    ++*count;
496    spin_unlock(&pin_fs_lock);
497    mntput(mnt);
498    return 0;
499}
500
501void simple_release_fs(struct vfsmount **mount, int *count)
502{
503    struct vfsmount *mnt;
504    spin_lock(&pin_fs_lock);
505    mnt = *mount;
506    if (!--*count)
507        *mount = NULL;
508    spin_unlock(&pin_fs_lock);
509    mntput(mnt);
510}
511
512/**
513 * simple_read_from_buffer - copy data from the buffer to user space
514 * @to: the user space buffer to read to
515 * @count: the maximum number of bytes to read
516 * @ppos: the current position in the buffer
517 * @from: the buffer to read from
518 * @available: the size of the buffer
519 *
520 * The simple_read_from_buffer() function reads up to @count bytes from the
521 * buffer @from at offset @ppos into the user space address starting at @to.
522 *
523 * On success, the number of bytes read is returned and the offset @ppos is
524 * advanced by this number, or negative value is returned on error.
525 **/
526ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
527                const void *from, size_t available)
528{
529    loff_t pos = *ppos;
530    if (pos < 0)
531        return -EINVAL;
532    if (pos >= available)
533        return 0;
534    if (count > available - pos)
535        count = available - pos;
536    if (copy_to_user(to, from + pos, count))
537        return -EFAULT;
538    *ppos = pos + count;
539    return count;
540}
541
542/**
543 * memory_read_from_buffer - copy data from the buffer
544 * @to: the kernel space buffer to read to
545 * @count: the maximum number of bytes to read
546 * @ppos: the current position in the buffer
547 * @from: the buffer to read from
548 * @available: the size of the buffer
549 *
550 * The memory_read_from_buffer() function reads up to @count bytes from the
551 * buffer @from at offset @ppos into the kernel space address starting at @to.
552 *
553 * On success, the number of bytes read is returned and the offset @ppos is
554 * advanced by this number, or negative value is returned on error.
555 **/
556ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
557                const void *from, size_t available)
558{
559    loff_t pos = *ppos;
560
561    if (pos < 0)
562        return -EINVAL;
563    if (pos >= available)
564        return 0;
565    if (count > available - pos)
566        count = available - pos;
567    memcpy(to, from + pos, count);
568    *ppos = pos + count;
569
570    return count;
571}
572
573/*
574 * Transaction based IO.
575 * The file expects a single write which triggers the transaction, and then
576 * possibly a read which collects the result - which is stored in a
577 * file-local buffer.
578 */
579
580void simple_transaction_set(struct file *file, size_t n)
581{
582    struct simple_transaction_argresp *ar = file->private_data;
583
584    BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
585
586    /*
587     * The barrier ensures that ar->size will really remain zero until
588     * ar->data is ready for reading.
589     */
590    smp_mb();
591    ar->size = n;
592}
593
594char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
595{
596    struct simple_transaction_argresp *ar;
597    static DEFINE_SPINLOCK(simple_transaction_lock);
598
599    if (size > SIMPLE_TRANSACTION_LIMIT - 1)
600        return ERR_PTR(-EFBIG);
601
602    ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
603    if (!ar)
604        return ERR_PTR(-ENOMEM);
605
606    spin_lock(&simple_transaction_lock);
607
608    /* only one write allowed per open */
609    if (file->private_data) {
610        spin_unlock(&simple_transaction_lock);
611        free_page((unsigned long)ar);
612        return ERR_PTR(-EBUSY);
613    }
614
615    file->private_data = ar;
616
617    spin_unlock(&simple_transaction_lock);
618
619    if (copy_from_user(ar->data, buf, size))
620        return ERR_PTR(-EFAULT);
621
622    return ar->data;
623}
624
625ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
626{
627    struct simple_transaction_argresp *ar = file->private_data;
628
629    if (!ar)
630        return 0;
631    return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
632}
633
634int simple_transaction_release(struct inode *inode, struct file *file)
635{
636    free_page((unsigned long)file->private_data);
637    return 0;
638}
639
640/* Simple attribute files */
641
642struct simple_attr {
643    int (*get)(void *, u64 *);
644    int (*set)(void *, u64);
645    char get_buf[24]; /* enough to store a u64 and "\n\0" */
646    char set_buf[24];
647    void *data;
648    const char *fmt; /* format for read operation */
649    struct mutex mutex; /* protects access to these buffers */
650};
651
652/* simple_attr_open is called by an actual attribute open file operation
653 * to set the attribute specific access operations. */
654int simple_attr_open(struct inode *inode, struct file *file,
655             int (*get)(void *, u64 *), int (*set)(void *, u64),
656             const char *fmt)
657{
658    struct simple_attr *attr;
659
660    attr = kmalloc(sizeof(*attr), GFP_KERNEL);
661    if (!attr)
662        return -ENOMEM;
663
664    attr->get = get;
665    attr->set = set;
666    attr->data = inode->i_private;
667    attr->fmt = fmt;
668    mutex_init(&attr->mutex);
669
670    file->private_data = attr;
671
672    return nonseekable_open(inode, file);
673}
674
675int simple_attr_release(struct inode *inode, struct file *file)
676{
677    kfree(file->private_data);
678    return 0;
679}
680
681/* read from the buffer that is filled with the get function */
682ssize_t simple_attr_read(struct file *file, char __user *buf,
683             size_t len, loff_t *ppos)
684{
685    struct simple_attr *attr;
686    size_t size;
687    ssize_t ret;
688
689    attr = file->private_data;
690
691    if (!attr->get)
692        return -EACCES;
693
694    ret = mutex_lock_interruptible(&attr->mutex);
695    if (ret)
696        return ret;
697
698    if (*ppos) { /* continued read */
699        size = strlen(attr->get_buf);
700    } else { /* first read */
701        u64 val;
702        ret = attr->get(attr->data, &val);
703        if (ret)
704            goto out;
705
706        size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
707                 attr->fmt, (unsigned long long)val);
708    }
709
710    ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
711out:
712    mutex_unlock(&attr->mutex);
713    return ret;
714}
715
716/* interpret the buffer as a number to call the set function with */
717ssize_t simple_attr_write(struct file *file, const char __user *buf,
718              size_t len, loff_t *ppos)
719{
720    struct simple_attr *attr;
721    u64 val;
722    size_t size;
723    ssize_t ret;
724
725    attr = file->private_data;
726    if (!attr->set)
727        return -EACCES;
728
729    ret = mutex_lock_interruptible(&attr->mutex);
730    if (ret)
731        return ret;
732
733    ret = -EFAULT;
734    size = min(sizeof(attr->set_buf) - 1, len);
735    if (copy_from_user(attr->set_buf, buf, size))
736        goto out;
737
738    ret = len; /* claim we got the whole input */
739    attr->set_buf[size] = '\0';
740    val = simple_strtol(attr->set_buf, NULL, 0);
741    attr->set(attr->data, val);
742out:
743    mutex_unlock(&attr->mutex);
744    return ret;
745}
746
747/**
748 * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
749 * @sb: filesystem to do the file handle conversion on
750 * @fid: file handle to convert
751 * @fh_len: length of the file handle in bytes
752 * @fh_type: type of file handle
753 * @get_inode: filesystem callback to retrieve inode
754 *
755 * This function decodes @fid as long as it has one of the well-known
756 * Linux filehandle types and calls @get_inode on it to retrieve the
757 * inode for the object specified in the file handle.
758 */
759struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
760        int fh_len, int fh_type, struct inode *(*get_inode)
761            (struct super_block *sb, u64 ino, u32 gen))
762{
763    struct inode *inode = NULL;
764
765    if (fh_len < 2)
766        return NULL;
767
768    switch (fh_type) {
769    case FILEID_INO32_GEN:
770    case FILEID_INO32_GEN_PARENT:
771        inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
772        break;
773    }
774
775    return d_obtain_alias(inode);
776}
777EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
778
779/**
780 * generic_fh_to_dentry - generic helper for the fh_to_parent export operation
781 * @sb: filesystem to do the file handle conversion on
782 * @fid: file handle to convert
783 * @fh_len: length of the file handle in bytes
784 * @fh_type: type of file handle
785 * @get_inode: filesystem callback to retrieve inode
786 *
787 * This function decodes @fid as long as it has one of the well-known
788 * Linux filehandle types and calls @get_inode on it to retrieve the
789 * inode for the _parent_ object specified in the file handle if it
790 * is specified in the file handle, or NULL otherwise.
791 */
792struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
793        int fh_len, int fh_type, struct inode *(*get_inode)
794            (struct super_block *sb, u64 ino, u32 gen))
795{
796    struct inode *inode = NULL;
797
798    if (fh_len <= 2)
799        return NULL;
800
801    switch (fh_type) {
802    case FILEID_INO32_GEN_PARENT:
803        inode = get_inode(sb, fid->i32.parent_ino,
804                  (fh_len > 3 ? fid->i32.parent_gen : 0));
805        break;
806    }
807
808    return d_obtain_alias(inode);
809}
810EXPORT_SYMBOL_GPL(generic_fh_to_parent);
811
812int simple_fsync(struct file *file, struct dentry *dentry, int datasync)
813{
814    struct writeback_control wbc = {
815        .sync_mode = WB_SYNC_ALL,
816        .nr_to_write = 0, /* metadata-only; caller takes care of data */
817    };
818    struct inode *inode = dentry->d_inode;
819    int err;
820    int ret;
821
822    ret = sync_mapping_buffers(inode->i_mapping);
823    if (!(inode->i_state & I_DIRTY))
824        return ret;
825    if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
826        return ret;
827
828    err = sync_inode(inode, &wbc);
829    if (ret == 0)
830        ret = err;
831    return ret;
832}
833EXPORT_SYMBOL(simple_fsync);
834
835EXPORT_SYMBOL(dcache_dir_close);
836EXPORT_SYMBOL(dcache_dir_lseek);
837EXPORT_SYMBOL(dcache_dir_open);
838EXPORT_SYMBOL(dcache_readdir);
839EXPORT_SYMBOL(generic_read_dir);
840EXPORT_SYMBOL(get_sb_pseudo);
841EXPORT_SYMBOL(simple_write_begin);
842EXPORT_SYMBOL(simple_write_end);
843EXPORT_SYMBOL(simple_dir_inode_operations);
844EXPORT_SYMBOL(simple_dir_operations);
845EXPORT_SYMBOL(simple_empty);
846EXPORT_SYMBOL(d_alloc_name);
847EXPORT_SYMBOL(simple_fill_super);
848EXPORT_SYMBOL(simple_getattr);
849EXPORT_SYMBOL(simple_link);
850EXPORT_SYMBOL(simple_lookup);
851EXPORT_SYMBOL(simple_pin_fs);
852EXPORT_UNUSED_SYMBOL(simple_prepare_write);
853EXPORT_SYMBOL(simple_readpage);
854EXPORT_SYMBOL(simple_release_fs);
855EXPORT_SYMBOL(simple_rename);
856EXPORT_SYMBOL(simple_rmdir);
857EXPORT_SYMBOL(simple_statfs);
858EXPORT_SYMBOL(simple_sync_file);
859EXPORT_SYMBOL(simple_unlink);
860EXPORT_SYMBOL(simple_read_from_buffer);
861EXPORT_SYMBOL(memory_read_from_buffer);
862EXPORT_SYMBOL(simple_transaction_set);
863EXPORT_SYMBOL(simple_transaction_get);
864EXPORT_SYMBOL(simple_transaction_read);
865EXPORT_SYMBOL(simple_transaction_release);
866EXPORT_SYMBOL_GPL(simple_attr_open);
867EXPORT_SYMBOL_GPL(simple_attr_release);
868EXPORT_SYMBOL_GPL(simple_attr_read);
869EXPORT_SYMBOL_GPL(simple_attr_write);
870

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