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/slab.h>
9#include <linux/mount.h>
10#include <linux/vfs.h>
11#include <linux/quotaops.h>
12#include <linux/mutex.h>
13#include <linux/exportfs.h>
14#include <linux/writeback.h>
15#include <linux/buffer_head.h>
16
17#include <asm/uaccess.h>
18
19static inline int simple_positive(struct dentry *dentry)
20{
21    return dentry->d_inode && !d_unhashed(dentry);
22}
23
24int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
25           struct kstat *stat)
26{
27    struct inode *inode = dentry->d_inode;
28    generic_fillattr(inode, stat);
29    stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9);
30    return 0;
31}
32
33int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
34{
35    buf->f_type = dentry->d_sb->s_magic;
36    buf->f_bsize = PAGE_CACHE_SIZE;
37    buf->f_namelen = NAME_MAX;
38    return 0;
39}
40
41/*
42 * Retaining negative dentries for an in-memory filesystem just wastes
43 * memory and lookup time: arrange for them to be deleted immediately.
44 */
45static int simple_delete_dentry(const struct dentry *dentry)
46{
47    return 1;
48}
49
50/*
51 * Lookup the data. This is trivial - if the dentry didn't already
52 * exist, we know it is negative. Set d_op to delete negative dentries.
53 */
54struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
55{
56    static const struct dentry_operations simple_dentry_operations = {
57        .d_delete = simple_delete_dentry,
58    };
59
60    if (dentry->d_name.len > NAME_MAX)
61        return ERR_PTR(-ENAMETOOLONG);
62    d_set_d_op(dentry, &simple_dentry_operations);
63    d_add(dentry, NULL);
64    return NULL;
65}
66
67int dcache_dir_open(struct inode *inode, struct file *file)
68{
69    static struct qstr cursor_name = {.len = 1, .name = "."};
70
71    file->private_data = d_alloc(file->f_path.dentry, &cursor_name);
72
73    return file->private_data ? 0 : -ENOMEM;
74}
75
76int dcache_dir_close(struct inode *inode, struct file *file)
77{
78    dput(file->private_data);
79    return 0;
80}
81
82loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
83{
84    struct dentry *dentry = file->f_path.dentry;
85    mutex_lock(&dentry->d_inode->i_mutex);
86    switch (origin) {
87        case 1:
88            offset += file->f_pos;
89        case 0:
90            if (offset >= 0)
91                break;
92        default:
93            mutex_unlock(&dentry->d_inode->i_mutex);
94            return -EINVAL;
95    }
96    if (offset != file->f_pos) {
97        file->f_pos = offset;
98        if (file->f_pos >= 2) {
99            struct list_head *p;
100            struct dentry *cursor = file->private_data;
101            loff_t n = file->f_pos - 2;
102
103            spin_lock(&dentry->d_lock);
104            /* d_lock not required for cursor */
105            list_del(&cursor->d_u.d_child);
106            p = dentry->d_subdirs.next;
107            while (n && p != &dentry->d_subdirs) {
108                struct dentry *next;
109                next = list_entry(p, struct dentry, d_u.d_child);
110                spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
111                if (simple_positive(next))
112                    n--;
113                spin_unlock(&next->d_lock);
114                p = p->next;
115            }
116            list_add_tail(&cursor->d_u.d_child, p);
117            spin_unlock(&dentry->d_lock);
118        }
119    }
120    mutex_unlock(&dentry->d_inode->i_mutex);
121    return offset;
122}
123
124/* Relationship between i_mode and the DT_xxx types */
125static inline unsigned char dt_type(struct inode *inode)
126{
127    return (inode->i_mode >> 12) & 15;
128}
129
130/*
131 * Directory is locked and all positive dentries in it are safe, since
132 * for ramfs-type trees they can't go away without unlink() or rmdir(),
133 * both impossible due to the lock on directory.
134 */
135
136int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
137{
138    struct dentry *dentry = filp->f_path.dentry;
139    struct dentry *cursor = filp->private_data;
140    struct list_head *p, *q = &cursor->d_u.d_child;
141    ino_t ino;
142    int i = filp->f_pos;
143
144    switch (i) {
145        case 0:
146            ino = dentry->d_inode->i_ino;
147            if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
148                break;
149            filp->f_pos++;
150            i++;
151            /* fallthrough */
152        case 1:
153            ino = parent_ino(dentry);
154            if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
155                break;
156            filp->f_pos++;
157            i++;
158            /* fallthrough */
159        default:
160            spin_lock(&dentry->d_lock);
161            if (filp->f_pos == 2)
162                list_move(q, &dentry->d_subdirs);
163
164            for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
165                struct dentry *next;
166                next = list_entry(p, struct dentry, d_u.d_child);
167                spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
168                if (!simple_positive(next)) {
169                    spin_unlock(&next->d_lock);
170                    continue;
171                }
172
173                spin_unlock(&next->d_lock);
174                spin_unlock(&dentry->d_lock);
175                if (filldir(dirent, next->d_name.name,
176                        next->d_name.len, filp->f_pos,
177                        next->d_inode->i_ino,
178                        dt_type(next->d_inode)) < 0)
179                    return 0;
180                spin_lock(&dentry->d_lock);
181                spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
182                /* next is still alive */
183                list_move(q, p);
184                spin_unlock(&next->d_lock);
185                p = q;
186                filp->f_pos++;
187            }
188            spin_unlock(&dentry->d_lock);
189    }
190    return 0;
191}
192
193ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
194{
195    return -EISDIR;
196}
197
198const struct file_operations simple_dir_operations = {
199    .open = dcache_dir_open,
200    .release = dcache_dir_close,
201    .llseek = dcache_dir_lseek,
202    .read = generic_read_dir,
203    .readdir = dcache_readdir,
204    .fsync = noop_fsync,
205};
206
207const struct inode_operations simple_dir_inode_operations = {
208    .lookup = simple_lookup,
209};
210
211static const struct super_operations simple_super_operations = {
212    .statfs = simple_statfs,
213};
214
215/*
216 * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
217 * will never be mountable)
218 */
219struct dentry *mount_pseudo(struct file_system_type *fs_type, char *name,
220    const struct super_operations *ops,
221    const struct dentry_operations *dops, unsigned long magic)
222{
223    struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
224    struct dentry *dentry;
225    struct inode *root;
226    struct qstr d_name = {.name = name, .len = strlen(name)};
227
228    if (IS_ERR(s))
229        return ERR_CAST(s);
230
231    s->s_flags = MS_NOUSER;
232    s->s_maxbytes = MAX_LFS_FILESIZE;
233    s->s_blocksize = PAGE_SIZE;
234    s->s_blocksize_bits = PAGE_SHIFT;
235    s->s_magic = magic;
236    s->s_op = ops ? ops : &simple_super_operations;
237    s->s_time_gran = 1;
238    root = new_inode(s);
239    if (!root)
240        goto Enomem;
241    /*
242     * since this is the first inode, make it number 1. New inodes created
243     * after this must take care not to collide with it (by passing
244     * max_reserved of 1 to iunique).
245     */
246    root->i_ino = 1;
247    root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
248    root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
249    dentry = d_alloc(NULL, &d_name);
250    if (!dentry) {
251        iput(root);
252        goto Enomem;
253    }
254    dentry->d_sb = s;
255    dentry->d_parent = dentry;
256    d_instantiate(dentry, root);
257    s->s_root = dentry;
258    s->s_d_op = dops;
259    s->s_flags |= MS_ACTIVE;
260    return dget(s->s_root);
261
262Enomem:
263    deactivate_locked_super(s);
264    return ERR_PTR(-ENOMEM);
265}
266
267int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
268{
269    struct inode *inode = old_dentry->d_inode;
270
271    inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
272    inc_nlink(inode);
273    ihold(inode);
274    dget(dentry);
275    d_instantiate(dentry, inode);
276    return 0;
277}
278
279int simple_empty(struct dentry *dentry)
280{
281    struct dentry *child;
282    int ret = 0;
283
284    spin_lock(&dentry->d_lock);
285    list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child) {
286        spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
287        if (simple_positive(child)) {
288            spin_unlock(&child->d_lock);
289            goto out;
290        }
291        spin_unlock(&child->d_lock);
292    }
293    ret = 1;
294out:
295    spin_unlock(&dentry->d_lock);
296    return ret;
297}
298
299int simple_unlink(struct inode *dir, struct dentry *dentry)
300{
301    struct inode *inode = dentry->d_inode;
302
303    inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
304    drop_nlink(inode);
305    dput(dentry);
306    return 0;
307}
308
309int simple_rmdir(struct inode *dir, struct dentry *dentry)
310{
311    if (!simple_empty(dentry))
312        return -ENOTEMPTY;
313
314    drop_nlink(dentry->d_inode);
315    simple_unlink(dir, dentry);
316    drop_nlink(dir);
317    return 0;
318}
319
320int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
321        struct inode *new_dir, struct dentry *new_dentry)
322{
323    struct inode *inode = old_dentry->d_inode;
324    int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);
325
326    if (!simple_empty(new_dentry))
327        return -ENOTEMPTY;
328
329    if (new_dentry->d_inode) {
330        simple_unlink(new_dir, new_dentry);
331        if (they_are_dirs)
332            drop_nlink(old_dir);
333    } else if (they_are_dirs) {
334        drop_nlink(old_dir);
335        inc_nlink(new_dir);
336    }
337
338    old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
339        new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;
340
341    return 0;
342}
343
344/**
345 * simple_setattr - setattr for simple filesystem
346 * @dentry: dentry
347 * @iattr: iattr structure
348 *
349 * Returns 0 on success, -error on failure.
350 *
351 * simple_setattr is a simple ->setattr implementation without a proper
352 * implementation of size changes.
353 *
354 * It can either be used for in-memory filesystems or special files
355 * on simple regular filesystems. Anything that needs to change on-disk
356 * or wire state on size changes needs its own setattr method.
357 */
358int simple_setattr(struct dentry *dentry, struct iattr *iattr)
359{
360    struct inode *inode = dentry->d_inode;
361    int error;
362
363    WARN_ON_ONCE(inode->i_op->truncate);
364
365    error = inode_change_ok(inode, iattr);
366    if (error)
367        return error;
368
369    if (iattr->ia_valid & ATTR_SIZE)
370        truncate_setsize(inode, iattr->ia_size);
371    setattr_copy(inode, iattr);
372    mark_inode_dirty(inode);
373    return 0;
374}
375EXPORT_SYMBOL(simple_setattr);
376
377int simple_readpage(struct file *file, struct page *page)
378{
379    clear_highpage(page);
380    flush_dcache_page(page);
381    SetPageUptodate(page);
382    unlock_page(page);
383    return 0;
384}
385
386int simple_write_begin(struct file *file, struct address_space *mapping,
387            loff_t pos, unsigned len, unsigned flags,
388            struct page **pagep, void **fsdata)
389{
390    struct page *page;
391    pgoff_t index;
392
393    index = pos >> PAGE_CACHE_SHIFT;
394
395    page = grab_cache_page_write_begin(mapping, index, flags);
396    if (!page)
397        return -ENOMEM;
398
399    *pagep = page;
400
401    if (!PageUptodate(page) && (len != PAGE_CACHE_SIZE)) {
402        unsigned from = pos & (PAGE_CACHE_SIZE - 1);
403
404        zero_user_segments(page, 0, from, from + len, PAGE_CACHE_SIZE);
405    }
406    return 0;
407}
408
409/**
410 * simple_write_end - .write_end helper for non-block-device FSes
411 * @available: See .write_end of address_space_operations
412 * @file: "
413 * @mapping: "
414 * @pos: "
415 * @len: "
416 * @copied: "
417 * @page: "
418 * @fsdata: "
419 *
420 * simple_write_end does the minimum needed for updating a page after writing is
421 * done. It has the same API signature as the .write_end of
422 * address_space_operations vector. So it can just be set onto .write_end for
423 * FSes that don't need any other processing. i_mutex is assumed to be held.
424 * Block based filesystems should use generic_write_end().
425 * NOTE: Even though i_size might get updated by this function, mark_inode_dirty
426 * is not called, so a filesystem that actually does store data in .write_inode
427 * should extend on what's done here with a call to mark_inode_dirty() in the
428 * case that i_size has changed.
429 */
430int simple_write_end(struct file *file, struct address_space *mapping,
431            loff_t pos, unsigned len, unsigned copied,
432            struct page *page, void *fsdata)
433{
434    struct inode *inode = page->mapping->host;
435    loff_t last_pos = pos + copied;
436
437    /* zero the stale part of the page if we did a short copy */
438    if (copied < len) {
439        unsigned from = pos & (PAGE_CACHE_SIZE - 1);
440
441        zero_user(page, from + copied, len - copied);
442    }
443
444    if (!PageUptodate(page))
445        SetPageUptodate(page);
446    /*
447     * No need to use i_size_read() here, the i_size
448     * cannot change under us because we hold the i_mutex.
449     */
450    if (last_pos > inode->i_size)
451        i_size_write(inode, last_pos);
452
453    set_page_dirty(page);
454    unlock_page(page);
455    page_cache_release(page);
456
457    return copied;
458}
459
460/*
461 * the inodes created here are not hashed. If you use iunique to generate
462 * unique inode values later for this filesystem, then you must take care
463 * to pass it an appropriate max_reserved value to avoid collisions.
464 */
465int simple_fill_super(struct super_block *s, unsigned long magic,
466              struct tree_descr *files)
467{
468    struct inode *inode;
469    struct dentry *root;
470    struct dentry *dentry;
471    int i;
472
473    s->s_blocksize = PAGE_CACHE_SIZE;
474    s->s_blocksize_bits = PAGE_CACHE_SHIFT;
475    s->s_magic = magic;
476    s->s_op = &simple_super_operations;
477    s->s_time_gran = 1;
478
479    inode = new_inode(s);
480    if (!inode)
481        return -ENOMEM;
482    /*
483     * because the root inode is 1, the files array must not contain an
484     * entry at index 1
485     */
486    inode->i_ino = 1;
487    inode->i_mode = S_IFDIR | 0755;
488    inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
489    inode->i_op = &simple_dir_inode_operations;
490    inode->i_fop = &simple_dir_operations;
491    inode->i_nlink = 2;
492    root = d_alloc_root(inode);
493    if (!root) {
494        iput(inode);
495        return -ENOMEM;
496    }
497    for (i = 0; !files->name || files->name[0]; i++, files++) {
498        if (!files->name)
499            continue;
500
501        /* warn if it tries to conflict with the root inode */
502        if (unlikely(i == 1))
503            printk(KERN_WARNING "%s: %s passed in a files array"
504                "with an index of 1!\n", __func__,
505                s->s_type->name);
506
507        dentry = d_alloc_name(root, files->name);
508        if (!dentry)
509            goto out;
510        inode = new_inode(s);
511        if (!inode)
512            goto out;
513        inode->i_mode = S_IFREG | files->mode;
514        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
515        inode->i_fop = files->ops;
516        inode->i_ino = i;
517        d_add(dentry, inode);
518    }
519    s->s_root = root;
520    return 0;
521out:
522    d_genocide(root);
523    dput(root);
524    return -ENOMEM;
525}
526
527static DEFINE_SPINLOCK(pin_fs_lock);
528
529int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
530{
531    struct vfsmount *mnt = NULL;
532    spin_lock(&pin_fs_lock);
533    if (unlikely(!*mount)) {
534        spin_unlock(&pin_fs_lock);
535        mnt = vfs_kern_mount(type, 0, type->name, NULL);
536        if (IS_ERR(mnt))
537            return PTR_ERR(mnt);
538        spin_lock(&pin_fs_lock);
539        if (!*mount)
540            *mount = mnt;
541    }
542    mntget(*mount);
543    ++*count;
544    spin_unlock(&pin_fs_lock);
545    mntput(mnt);
546    return 0;
547}
548
549void simple_release_fs(struct vfsmount **mount, int *count)
550{
551    struct vfsmount *mnt;
552    spin_lock(&pin_fs_lock);
553    mnt = *mount;
554    if (!--*count)
555        *mount = NULL;
556    spin_unlock(&pin_fs_lock);
557    mntput(mnt);
558}
559
560/**
561 * simple_read_from_buffer - copy data from the buffer to user space
562 * @to: the user space buffer to read to
563 * @count: the maximum number of bytes to read
564 * @ppos: the current position in the buffer
565 * @from: the buffer to read from
566 * @available: the size of the buffer
567 *
568 * The simple_read_from_buffer() function reads up to @count bytes from the
569 * buffer @from at offset @ppos into the user space address starting at @to.
570 *
571 * On success, the number of bytes read is returned and the offset @ppos is
572 * advanced by this number, or negative value is returned on error.
573 **/
574ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
575                const void *from, size_t available)
576{
577    loff_t pos = *ppos;
578    size_t ret;
579
580    if (pos < 0)
581        return -EINVAL;
582    if (pos >= available || !count)
583        return 0;
584    if (count > available - pos)
585        count = available - pos;
586    ret = copy_to_user(to, from + pos, count);
587    if (ret == count)
588        return -EFAULT;
589    count -= ret;
590    *ppos = pos + count;
591    return count;
592}
593
594/**
595 * simple_write_to_buffer - copy data from user space to the buffer
596 * @to: the buffer to write to
597 * @available: the size of the buffer
598 * @ppos: the current position in the buffer
599 * @from: the user space buffer to read from
600 * @count: the maximum number of bytes to read
601 *
602 * The simple_write_to_buffer() function reads up to @count bytes from the user
603 * space address starting at @from into the buffer @to at offset @ppos.
604 *
605 * On success, the number of bytes written is returned and the offset @ppos is
606 * advanced by this number, or negative value is returned on error.
607 **/
608ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
609        const void __user *from, size_t count)
610{
611    loff_t pos = *ppos;
612    size_t res;
613
614    if (pos < 0)
615        return -EINVAL;
616    if (pos >= available || !count)
617        return 0;
618    if (count > available - pos)
619        count = available - pos;
620    res = copy_from_user(to + pos, from, count);
621    if (res == count)
622        return -EFAULT;
623    count -= res;
624    *ppos = pos + count;
625    return count;
626}
627
628/**
629 * memory_read_from_buffer - copy data from the buffer
630 * @to: the kernel space buffer to read to
631 * @count: the maximum number of bytes to read
632 * @ppos: the current position in the buffer
633 * @from: the buffer to read from
634 * @available: the size of the buffer
635 *
636 * The memory_read_from_buffer() function reads up to @count bytes from the
637 * buffer @from at offset @ppos into the kernel space address starting at @to.
638 *
639 * On success, the number of bytes read is returned and the offset @ppos is
640 * advanced by this number, or negative value is returned on error.
641 **/
642ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
643                const void *from, size_t available)
644{
645    loff_t pos = *ppos;
646
647    if (pos < 0)
648        return -EINVAL;
649    if (pos >= available)
650        return 0;
651    if (count > available - pos)
652        count = available - pos;
653    memcpy(to, from + pos, count);
654    *ppos = pos + count;
655
656    return count;
657}
658
659/*
660 * Transaction based IO.
661 * The file expects a single write which triggers the transaction, and then
662 * possibly a read which collects the result - which is stored in a
663 * file-local buffer.
664 */
665
666void simple_transaction_set(struct file *file, size_t n)
667{
668    struct simple_transaction_argresp *ar = file->private_data;
669
670    BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
671
672    /*
673     * The barrier ensures that ar->size will really remain zero until
674     * ar->data is ready for reading.
675     */
676    smp_mb();
677    ar->size = n;
678}
679
680char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
681{
682    struct simple_transaction_argresp *ar;
683    static DEFINE_SPINLOCK(simple_transaction_lock);
684
685    if (size > SIMPLE_TRANSACTION_LIMIT - 1)
686        return ERR_PTR(-EFBIG);
687
688    ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
689    if (!ar)
690        return ERR_PTR(-ENOMEM);
691
692    spin_lock(&simple_transaction_lock);
693
694    /* only one write allowed per open */
695    if (file->private_data) {
696        spin_unlock(&simple_transaction_lock);
697        free_page((unsigned long)ar);
698        return ERR_PTR(-EBUSY);
699    }
700
701    file->private_data = ar;
702
703    spin_unlock(&simple_transaction_lock);
704
705    if (copy_from_user(ar->data, buf, size))
706        return ERR_PTR(-EFAULT);
707
708    return ar->data;
709}
710
711ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
712{
713    struct simple_transaction_argresp *ar = file->private_data;
714
715    if (!ar)
716        return 0;
717    return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
718}
719
720int simple_transaction_release(struct inode *inode, struct file *file)
721{
722    free_page((unsigned long)file->private_data);
723    return 0;
724}
725
726/* Simple attribute files */
727
728struct simple_attr {
729    int (*get)(void *, u64 *);
730    int (*set)(void *, u64);
731    char get_buf[24]; /* enough to store a u64 and "\n\0" */
732    char set_buf[24];
733    void *data;
734    const char *fmt; /* format for read operation */
735    struct mutex mutex; /* protects access to these buffers */
736};
737
738/* simple_attr_open is called by an actual attribute open file operation
739 * to set the attribute specific access operations. */
740int simple_attr_open(struct inode *inode, struct file *file,
741             int (*get)(void *, u64 *), int (*set)(void *, u64),
742             const char *fmt)
743{
744    struct simple_attr *attr;
745
746    attr = kmalloc(sizeof(*attr), GFP_KERNEL);
747    if (!attr)
748        return -ENOMEM;
749
750    attr->get = get;
751    attr->set = set;
752    attr->data = inode->i_private;
753    attr->fmt = fmt;
754    mutex_init(&attr->mutex);
755
756    file->private_data = attr;
757
758    return nonseekable_open(inode, file);
759}
760
761int simple_attr_release(struct inode *inode, struct file *file)
762{
763    kfree(file->private_data);
764    return 0;
765}
766
767/* read from the buffer that is filled with the get function */
768ssize_t simple_attr_read(struct file *file, char __user *buf,
769             size_t len, loff_t *ppos)
770{
771    struct simple_attr *attr;
772    size_t size;
773    ssize_t ret;
774
775    attr = file->private_data;
776
777    if (!attr->get)
778        return -EACCES;
779
780    ret = mutex_lock_interruptible(&attr->mutex);
781    if (ret)
782        return ret;
783
784    if (*ppos) { /* continued read */
785        size = strlen(attr->get_buf);
786    } else { /* first read */
787        u64 val;
788        ret = attr->get(attr->data, &val);
789        if (ret)
790            goto out;
791
792        size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
793                 attr->fmt, (unsigned long long)val);
794    }
795
796    ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
797out:
798    mutex_unlock(&attr->mutex);
799    return ret;
800}
801
802/* interpret the buffer as a number to call the set function with */
803ssize_t simple_attr_write(struct file *file, const char __user *buf,
804              size_t len, loff_t *ppos)
805{
806    struct simple_attr *attr;
807    u64 val;
808    size_t size;
809    ssize_t ret;
810
811    attr = file->private_data;
812    if (!attr->set)
813        return -EACCES;
814
815    ret = mutex_lock_interruptible(&attr->mutex);
816    if (ret)
817        return ret;
818
819    ret = -EFAULT;
820    size = min(sizeof(attr->set_buf) - 1, len);
821    if (copy_from_user(attr->set_buf, buf, size))
822        goto out;
823
824    attr->set_buf[size] = '\0';
825    val = simple_strtoll(attr->set_buf, NULL, 0);
826    ret = attr->set(attr->data, val);
827    if (ret == 0)
828        ret = len; /* on success, claim we got the whole input */
829out:
830    mutex_unlock(&attr->mutex);
831    return ret;
832}
833
834/**
835 * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
836 * @sb: filesystem to do the file handle conversion on
837 * @fid: file handle to convert
838 * @fh_len: length of the file handle in bytes
839 * @fh_type: type of file handle
840 * @get_inode: filesystem callback to retrieve inode
841 *
842 * This function decodes @fid as long as it has one of the well-known
843 * Linux filehandle types and calls @get_inode on it to retrieve the
844 * inode for the object specified in the file handle.
845 */
846struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
847        int fh_len, int fh_type, struct inode *(*get_inode)
848            (struct super_block *sb, u64 ino, u32 gen))
849{
850    struct inode *inode = NULL;
851
852    if (fh_len < 2)
853        return NULL;
854
855    switch (fh_type) {
856    case FILEID_INO32_GEN:
857    case FILEID_INO32_GEN_PARENT:
858        inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
859        break;
860    }
861
862    return d_obtain_alias(inode);
863}
864EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
865
866/**
867 * generic_fh_to_dentry - generic helper for the fh_to_parent export operation
868 * @sb: filesystem to do the file handle conversion on
869 * @fid: file handle to convert
870 * @fh_len: length of the file handle in bytes
871 * @fh_type: type of file handle
872 * @get_inode: filesystem callback to retrieve inode
873 *
874 * This function decodes @fid as long as it has one of the well-known
875 * Linux filehandle types and calls @get_inode on it to retrieve the
876 * inode for the _parent_ object specified in the file handle if it
877 * is specified in the file handle, or NULL otherwise.
878 */
879struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
880        int fh_len, int fh_type, struct inode *(*get_inode)
881            (struct super_block *sb, u64 ino, u32 gen))
882{
883    struct inode *inode = NULL;
884
885    if (fh_len <= 2)
886        return NULL;
887
888    switch (fh_type) {
889    case FILEID_INO32_GEN_PARENT:
890        inode = get_inode(sb, fid->i32.parent_ino,
891                  (fh_len > 3 ? fid->i32.parent_gen : 0));
892        break;
893    }
894
895    return d_obtain_alias(inode);
896}
897EXPORT_SYMBOL_GPL(generic_fh_to_parent);
898
899/**
900 * generic_file_fsync - generic fsync implementation for simple filesystems
901 * @file: file to synchronize
902 * @datasync: only synchronize essential metadata if true
903 *
904 * This is a generic implementation of the fsync method for simple
905 * filesystems which track all non-inode metadata in the buffers list
906 * hanging off the address_space structure.
907 */
908int generic_file_fsync(struct file *file, int datasync)
909{
910    struct inode *inode = file->f_mapping->host;
911    int err;
912    int ret;
913
914    ret = sync_mapping_buffers(inode->i_mapping);
915    if (!(inode->i_state & I_DIRTY))
916        return ret;
917    if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
918        return ret;
919
920    err = sync_inode_metadata(inode, 1);
921    if (ret == 0)
922        ret = err;
923    return ret;
924}
925EXPORT_SYMBOL(generic_file_fsync);
926
927/**
928 * generic_check_addressable - Check addressability of file system
929 * @blocksize_bits: log of file system block size
930 * @num_blocks: number of blocks in file system
931 *
932 * Determine whether a file system with @num_blocks blocks (and a
933 * block size of 2**@blocksize_bits) is addressable by the sector_t
934 * and page cache of the system. Return 0 if so and -EFBIG otherwise.
935 */
936int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
937{
938    u64 last_fs_block = num_blocks - 1;
939    u64 last_fs_page =
940        last_fs_block >> (PAGE_CACHE_SHIFT - blocksize_bits);
941
942    if (unlikely(num_blocks == 0))
943        return 0;
944
945    if ((blocksize_bits < 9) || (blocksize_bits > PAGE_CACHE_SHIFT))
946        return -EINVAL;
947
948    if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
949        (last_fs_page > (pgoff_t)(~0ULL))) {
950        return -EFBIG;
951    }
952    return 0;
953}
954EXPORT_SYMBOL(generic_check_addressable);
955
956/*
957 * No-op implementation of ->fsync for in-memory filesystems.
958 */
959int noop_fsync(struct file *file, int datasync)
960{
961    return 0;
962}
963
964EXPORT_SYMBOL(dcache_dir_close);
965EXPORT_SYMBOL(dcache_dir_lseek);
966EXPORT_SYMBOL(dcache_dir_open);
967EXPORT_SYMBOL(dcache_readdir);
968EXPORT_SYMBOL(generic_read_dir);
969EXPORT_SYMBOL(mount_pseudo);
970EXPORT_SYMBOL(simple_write_begin);
971EXPORT_SYMBOL(simple_write_end);
972EXPORT_SYMBOL(simple_dir_inode_operations);
973EXPORT_SYMBOL(simple_dir_operations);
974EXPORT_SYMBOL(simple_empty);
975EXPORT_SYMBOL(simple_fill_super);
976EXPORT_SYMBOL(simple_getattr);
977EXPORT_SYMBOL(simple_link);
978EXPORT_SYMBOL(simple_lookup);
979EXPORT_SYMBOL(simple_pin_fs);
980EXPORT_SYMBOL(simple_readpage);
981EXPORT_SYMBOL(simple_release_fs);
982EXPORT_SYMBOL(simple_rename);
983EXPORT_SYMBOL(simple_rmdir);
984EXPORT_SYMBOL(simple_statfs);
985EXPORT_SYMBOL(noop_fsync);
986EXPORT_SYMBOL(simple_unlink);
987EXPORT_SYMBOL(simple_read_from_buffer);
988EXPORT_SYMBOL(simple_write_to_buffer);
989EXPORT_SYMBOL(memory_read_from_buffer);
990EXPORT_SYMBOL(simple_transaction_set);
991EXPORT_SYMBOL(simple_transaction_get);
992EXPORT_SYMBOL(simple_transaction_read);
993EXPORT_SYMBOL(simple_transaction_release);
994EXPORT_SYMBOL_GPL(simple_attr_open);
995EXPORT_SYMBOL_GPL(simple_attr_release);
996EXPORT_SYMBOL_GPL(simple_attr_read);
997EXPORT_SYMBOL_GPL(simple_attr_write);
998

Archive Download this file



interactive