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TOMOYO Linux Cross Reference
Linux/fs/seq_file.c

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  1 /*
  2  * linux/fs/seq_file.c
  3  *
  4  * helper functions for making synthetic files from sequences of records.
  5  * initial implementation -- AV, Oct 2001.
  6  */
  7 
  8 #include <linux/fs.h>
  9 #include <linux/export.h>
 10 #include <linux/seq_file.h>
 11 #include <linux/vmalloc.h>
 12 #include <linux/slab.h>
 13 #include <linux/cred.h>
 14 #include <linux/mm.h>
 15 
 16 #include <asm/uaccess.h>
 17 #include <asm/page.h>
 18 
 19 static void seq_set_overflow(struct seq_file *m)
 20 {
 21         m->count = m->size;
 22 }
 23 
 24 static void *seq_buf_alloc(unsigned long size)
 25 {
 26         void *buf;
 27 
 28         /*
 29          * __GFP_NORETRY to avoid oom-killings with high-order allocations -
 30          * it's better to fall back to vmalloc() than to kill things.
 31          */
 32         buf = kmalloc(size, GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
 33         if (!buf && size > PAGE_SIZE)
 34                 buf = vmalloc(size);
 35         return buf;
 36 }
 37 
 38 /**
 39  *      seq_open -      initialize sequential file
 40  *      @file: file we initialize
 41  *      @op: method table describing the sequence
 42  *
 43  *      seq_open() sets @file, associating it with a sequence described
 44  *      by @op.  @op->start() sets the iterator up and returns the first
 45  *      element of sequence. @op->stop() shuts it down.  @op->next()
 46  *      returns the next element of sequence.  @op->show() prints element
 47  *      into the buffer.  In case of error ->start() and ->next() return
 48  *      ERR_PTR(error).  In the end of sequence they return %NULL. ->show()
 49  *      returns 0 in case of success and negative number in case of error.
 50  *      Returning SEQ_SKIP means "discard this element and move on".
 51  *      Note: seq_open() will allocate a struct seq_file and store its
 52  *      pointer in @file->private_data. This pointer should not be modified.
 53  */
 54 int seq_open(struct file *file, const struct seq_operations *op)
 55 {
 56         struct seq_file *p;
 57 
 58         WARN_ON(file->private_data);
 59 
 60         p = kzalloc(sizeof(*p), GFP_KERNEL);
 61         if (!p)
 62                 return -ENOMEM;
 63 
 64         file->private_data = p;
 65 
 66         mutex_init(&p->lock);
 67         p->op = op;
 68 #ifdef CONFIG_USER_NS
 69         p->user_ns = file->f_cred->user_ns;
 70 #endif
 71 
 72         /*
 73          * Wrappers around seq_open(e.g. swaps_open) need to be
 74          * aware of this. If they set f_version themselves, they
 75          * should call seq_open first and then set f_version.
 76          */
 77         file->f_version = 0;
 78 
 79         /*
 80          * seq_files support lseek() and pread().  They do not implement
 81          * write() at all, but we clear FMODE_PWRITE here for historical
 82          * reasons.
 83          *
 84          * If a client of seq_files a) implements file.write() and b) wishes to
 85          * support pwrite() then that client will need to implement its own
 86          * file.open() which calls seq_open() and then sets FMODE_PWRITE.
 87          */
 88         file->f_mode &= ~FMODE_PWRITE;
 89         return 0;
 90 }
 91 EXPORT_SYMBOL(seq_open);
 92 
 93 static int traverse(struct seq_file *m, loff_t offset)
 94 {
 95         loff_t pos = 0, index;
 96         int error = 0;
 97         void *p;
 98 
 99         m->version = 0;
100         index = 0;
101         m->count = m->from = 0;
102         if (!offset) {
103                 m->index = index;
104                 return 0;
105         }
106         if (!m->buf) {
107                 m->buf = seq_buf_alloc(m->size = PAGE_SIZE);
108                 if (!m->buf)
109                         return -ENOMEM;
110         }
111         p = m->op->start(m, &index);
112         while (p) {
113                 error = PTR_ERR(p);
114                 if (IS_ERR(p))
115                         break;
116                 error = m->op->show(m, p);
117                 if (error < 0)
118                         break;
119                 if (unlikely(error)) {
120                         error = 0;
121                         m->count = 0;
122                 }
123                 if (seq_has_overflowed(m))
124                         goto Eoverflow;
125                 if (pos + m->count > offset) {
126                         m->from = offset - pos;
127                         m->count -= m->from;
128                         m->index = index;
129                         break;
130                 }
131                 pos += m->count;
132                 m->count = 0;
133                 if (pos == offset) {
134                         index++;
135                         m->index = index;
136                         break;
137                 }
138                 p = m->op->next(m, p, &index);
139         }
140         m->op->stop(m, p);
141         m->index = index;
142         return error;
143 
144 Eoverflow:
145         m->op->stop(m, p);
146         kvfree(m->buf);
147         m->count = 0;
148         m->buf = seq_buf_alloc(m->size <<= 1);
149         return !m->buf ? -ENOMEM : -EAGAIN;
150 }
151 
152 /**
153  *      seq_read -      ->read() method for sequential files.
154  *      @file: the file to read from
155  *      @buf: the buffer to read to
156  *      @size: the maximum number of bytes to read
157  *      @ppos: the current position in the file
158  *
159  *      Ready-made ->f_op->read()
160  */
161 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
162 {
163         struct seq_file *m = file->private_data;
164         size_t copied = 0;
165         loff_t pos;
166         size_t n;
167         void *p;
168         int err = 0;
169 
170         mutex_lock(&m->lock);
171 
172         /*
173          * seq_file->op->..m_start/m_stop/m_next may do special actions
174          * or optimisations based on the file->f_version, so we want to
175          * pass the file->f_version to those methods.
176          *
177          * seq_file->version is just copy of f_version, and seq_file
178          * methods can treat it simply as file version.
179          * It is copied in first and copied out after all operations.
180          * It is convenient to have it as  part of structure to avoid the
181          * need of passing another argument to all the seq_file methods.
182          */
183         m->version = file->f_version;
184 
185         /* Don't assume *ppos is where we left it */
186         if (unlikely(*ppos != m->read_pos)) {
187                 while ((err = traverse(m, *ppos)) == -EAGAIN)
188                         ;
189                 if (err) {
190                         /* With prejudice... */
191                         m->read_pos = 0;
192                         m->version = 0;
193                         m->index = 0;
194                         m->count = 0;
195                         goto Done;
196                 } else {
197                         m->read_pos = *ppos;
198                 }
199         }
200 
201         /* grab buffer if we didn't have one */
202         if (!m->buf) {
203                 m->buf = seq_buf_alloc(m->size = PAGE_SIZE);
204                 if (!m->buf)
205                         goto Enomem;
206         }
207         /* if not empty - flush it first */
208         if (m->count) {
209                 n = min(m->count, size);
210                 err = copy_to_user(buf, m->buf + m->from, n);
211                 if (err)
212                         goto Efault;
213                 m->count -= n;
214                 m->from += n;
215                 size -= n;
216                 buf += n;
217                 copied += n;
218                 if (!m->count)
219                         m->index++;
220                 if (!size)
221                         goto Done;
222         }
223         /* we need at least one record in buffer */
224         pos = m->index;
225         p = m->op->start(m, &pos);
226         while (1) {
227                 err = PTR_ERR(p);
228                 if (!p || IS_ERR(p))
229                         break;
230                 err = m->op->show(m, p);
231                 if (err < 0)
232                         break;
233                 if (unlikely(err))
234                         m->count = 0;
235                 if (unlikely(!m->count)) {
236                         p = m->op->next(m, p, &pos);
237                         m->index = pos;
238                         continue;
239                 }
240                 if (m->count < m->size)
241                         goto Fill;
242                 m->op->stop(m, p);
243                 kvfree(m->buf);
244                 m->count = 0;
245                 m->buf = seq_buf_alloc(m->size <<= 1);
246                 if (!m->buf)
247                         goto Enomem;
248                 m->version = 0;
249                 pos = m->index;
250                 p = m->op->start(m, &pos);
251         }
252         m->op->stop(m, p);
253         m->count = 0;
254         goto Done;
255 Fill:
256         /* they want more? let's try to get some more */
257         while (m->count < size) {
258                 size_t offs = m->count;
259                 loff_t next = pos;
260                 p = m->op->next(m, p, &next);
261                 if (!p || IS_ERR(p)) {
262                         err = PTR_ERR(p);
263                         break;
264                 }
265                 err = m->op->show(m, p);
266                 if (seq_has_overflowed(m) || err) {
267                         m->count = offs;
268                         if (likely(err <= 0))
269                                 break;
270                 }
271                 pos = next;
272         }
273         m->op->stop(m, p);
274         n = min(m->count, size);
275         err = copy_to_user(buf, m->buf, n);
276         if (err)
277                 goto Efault;
278         copied += n;
279         m->count -= n;
280         if (m->count)
281                 m->from = n;
282         else
283                 pos++;
284         m->index = pos;
285 Done:
286         if (!copied)
287                 copied = err;
288         else {
289                 *ppos += copied;
290                 m->read_pos += copied;
291         }
292         file->f_version = m->version;
293         mutex_unlock(&m->lock);
294         return copied;
295 Enomem:
296         err = -ENOMEM;
297         goto Done;
298 Efault:
299         err = -EFAULT;
300         goto Done;
301 }
302 EXPORT_SYMBOL(seq_read);
303 
304 /**
305  *      seq_lseek -     ->llseek() method for sequential files.
306  *      @file: the file in question
307  *      @offset: new position
308  *      @whence: 0 for absolute, 1 for relative position
309  *
310  *      Ready-made ->f_op->llseek()
311  */
312 loff_t seq_lseek(struct file *file, loff_t offset, int whence)
313 {
314         struct seq_file *m = file->private_data;
315         loff_t retval = -EINVAL;
316 
317         mutex_lock(&m->lock);
318         m->version = file->f_version;
319         switch (whence) {
320         case SEEK_CUR:
321                 offset += file->f_pos;
322         case SEEK_SET:
323                 if (offset < 0)
324                         break;
325                 retval = offset;
326                 if (offset != m->read_pos) {
327                         while ((retval = traverse(m, offset)) == -EAGAIN)
328                                 ;
329                         if (retval) {
330                                 /* with extreme prejudice... */
331                                 file->f_pos = 0;
332                                 m->read_pos = 0;
333                                 m->version = 0;
334                                 m->index = 0;
335                                 m->count = 0;
336                         } else {
337                                 m->read_pos = offset;
338                                 retval = file->f_pos = offset;
339                         }
340                 } else {
341                         file->f_pos = offset;
342                 }
343         }
344         file->f_version = m->version;
345         mutex_unlock(&m->lock);
346         return retval;
347 }
348 EXPORT_SYMBOL(seq_lseek);
349 
350 /**
351  *      seq_release -   free the structures associated with sequential file.
352  *      @file: file in question
353  *      @inode: its inode
354  *
355  *      Frees the structures associated with sequential file; can be used
356  *      as ->f_op->release() if you don't have private data to destroy.
357  */
358 int seq_release(struct inode *inode, struct file *file)
359 {
360         struct seq_file *m = file->private_data;
361         kvfree(m->buf);
362         kfree(m);
363         return 0;
364 }
365 EXPORT_SYMBOL(seq_release);
366 
367 /**
368  *      seq_escape -    print string into buffer, escaping some characters
369  *      @m:     target buffer
370  *      @s:     string
371  *      @esc:   set of characters that need escaping
372  *
373  *      Puts string into buffer, replacing each occurrence of character from
374  *      @esc with usual octal escape.  Returns 0 in case of success, -1 - in
375  *      case of overflow.
376  */
377 int seq_escape(struct seq_file *m, const char *s, const char *esc)
378 {
379         char *end = m->buf + m->size;
380         char *p;
381         char c;
382 
383         for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
384                 if (!strchr(esc, c)) {
385                         *p++ = c;
386                         continue;
387                 }
388                 if (p + 3 < end) {
389                         *p++ = '\\';
390                         *p++ = '' + ((c & 0300) >> 6);
391                         *p++ = '' + ((c & 070) >> 3);
392                         *p++ = '' + (c & 07);
393                         continue;
394                 }
395                 seq_set_overflow(m);
396                 return -1;
397         }
398         m->count = p - m->buf;
399         return 0;
400 }
401 EXPORT_SYMBOL(seq_escape);
402 
403 int seq_vprintf(struct seq_file *m, const char *f, va_list args)
404 {
405         int len;
406 
407         if (m->count < m->size) {
408                 len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
409                 if (m->count + len < m->size) {
410                         m->count += len;
411                         return 0;
412                 }
413         }
414         seq_set_overflow(m);
415         return -1;
416 }
417 EXPORT_SYMBOL(seq_vprintf);
418 
419 int seq_printf(struct seq_file *m, const char *f, ...)
420 {
421         int ret;
422         va_list args;
423 
424         va_start(args, f);
425         ret = seq_vprintf(m, f, args);
426         va_end(args);
427 
428         return ret;
429 }
430 EXPORT_SYMBOL(seq_printf);
431 
432 /**
433  *      mangle_path -   mangle and copy path to buffer beginning
434  *      @s: buffer start
435  *      @p: beginning of path in above buffer
436  *      @esc: set of characters that need escaping
437  *
438  *      Copy the path from @p to @s, replacing each occurrence of character from
439  *      @esc with usual octal escape.
440  *      Returns pointer past last written character in @s, or NULL in case of
441  *      failure.
442  */
443 char *mangle_path(char *s, const char *p, const char *esc)
444 {
445         while (s <= p) {
446                 char c = *p++;
447                 if (!c) {
448                         return s;
449                 } else if (!strchr(esc, c)) {
450                         *s++ = c;
451                 } else if (s + 4 > p) {
452                         break;
453                 } else {
454                         *s++ = '\\';
455                         *s++ = '' + ((c & 0300) >> 6);
456                         *s++ = '' + ((c & 070) >> 3);
457                         *s++ = '' + (c & 07);
458                 }
459         }
460         return NULL;
461 }
462 EXPORT_SYMBOL(mangle_path);
463 
464 /**
465  * seq_path - seq_file interface to print a pathname
466  * @m: the seq_file handle
467  * @path: the struct path to print
468  * @esc: set of characters to escape in the output
469  *
470  * return the absolute path of 'path', as represented by the
471  * dentry / mnt pair in the path parameter.
472  */
473 int seq_path(struct seq_file *m, const struct path *path, const char *esc)
474 {
475         char *buf;
476         size_t size = seq_get_buf(m, &buf);
477         int res = -1;
478 
479         if (size) {
480                 char *p = d_path(path, buf, size);
481                 if (!IS_ERR(p)) {
482                         char *end = mangle_path(buf, p, esc);
483                         if (end)
484                                 res = end - buf;
485                 }
486         }
487         seq_commit(m, res);
488 
489         return res;
490 }
491 EXPORT_SYMBOL(seq_path);
492 
493 /**
494  * seq_file_path - seq_file interface to print a pathname of a file
495  * @m: the seq_file handle
496  * @file: the struct file to print
497  * @esc: set of characters to escape in the output
498  *
499  * return the absolute path to the file.
500  */
501 int seq_file_path(struct seq_file *m, struct file *file, const char *esc)
502 {
503         return seq_path(m, &file->f_path, esc);
504 }
505 EXPORT_SYMBOL(seq_file_path);
506 
507 /*
508  * Same as seq_path, but relative to supplied root.
509  */
510 int seq_path_root(struct seq_file *m, const struct path *path,
511                   const struct path *root, const char *esc)
512 {
513         char *buf;
514         size_t size = seq_get_buf(m, &buf);
515         int res = -ENAMETOOLONG;
516 
517         if (size) {
518                 char *p;
519 
520                 p = __d_path(path, root, buf, size);
521                 if (!p)
522                         return SEQ_SKIP;
523                 res = PTR_ERR(p);
524                 if (!IS_ERR(p)) {
525                         char *end = mangle_path(buf, p, esc);
526                         if (end)
527                                 res = end - buf;
528                         else
529                                 res = -ENAMETOOLONG;
530                 }
531         }
532         seq_commit(m, res);
533 
534         return res < 0 && res != -ENAMETOOLONG ? res : 0;
535 }
536 
537 /*
538  * returns the path of the 'dentry' from the root of its filesystem.
539  */
540 int seq_dentry(struct seq_file *m, struct dentry *dentry, const char *esc)
541 {
542         char *buf;
543         size_t size = seq_get_buf(m, &buf);
544         int res = -1;
545 
546         if (size) {
547                 char *p = dentry_path(dentry, buf, size);
548                 if (!IS_ERR(p)) {
549                         char *end = mangle_path(buf, p, esc);
550                         if (end)
551                                 res = end - buf;
552                 }
553         }
554         seq_commit(m, res);
555 
556         return res;
557 }
558 EXPORT_SYMBOL(seq_dentry);
559 
560 static void *single_start(struct seq_file *p, loff_t *pos)
561 {
562         return NULL + (*pos == 0);
563 }
564 
565 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
566 {
567         ++*pos;
568         return NULL;
569 }
570 
571 static void single_stop(struct seq_file *p, void *v)
572 {
573 }
574 
575 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
576                 void *data)
577 {
578         struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
579         int res = -ENOMEM;
580 
581         if (op) {
582                 op->start = single_start;
583                 op->next = single_next;
584                 op->stop = single_stop;
585                 op->show = show;
586                 res = seq_open(file, op);
587                 if (!res)
588                         ((struct seq_file *)file->private_data)->private = data;
589                 else
590                         kfree(op);
591         }
592         return res;
593 }
594 EXPORT_SYMBOL(single_open);
595 
596 int single_open_size(struct file *file, int (*show)(struct seq_file *, void *),
597                 void *data, size_t size)
598 {
599         char *buf = seq_buf_alloc(size);
600         int ret;
601         if (!buf)
602                 return -ENOMEM;
603         ret = single_open(file, show, data);
604         if (ret) {
605                 kvfree(buf);
606                 return ret;
607         }
608         ((struct seq_file *)file->private_data)->buf = buf;
609         ((struct seq_file *)file->private_data)->size = size;
610         return 0;
611 }
612 EXPORT_SYMBOL(single_open_size);
613 
614 int single_release(struct inode *inode, struct file *file)
615 {
616         const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
617         int res = seq_release(inode, file);
618         kfree(op);
619         return res;
620 }
621 EXPORT_SYMBOL(single_release);
622 
623 int seq_release_private(struct inode *inode, struct file *file)
624 {
625         struct seq_file *seq = file->private_data;
626 
627         kfree(seq->private);
628         seq->private = NULL;
629         return seq_release(inode, file);
630 }
631 EXPORT_SYMBOL(seq_release_private);
632 
633 void *__seq_open_private(struct file *f, const struct seq_operations *ops,
634                 int psize)
635 {
636         int rc;
637         void *private;
638         struct seq_file *seq;
639 
640         private = kzalloc(psize, GFP_KERNEL);
641         if (private == NULL)
642                 goto out;
643 
644         rc = seq_open(f, ops);
645         if (rc < 0)
646                 goto out_free;
647 
648         seq = f->private_data;
649         seq->private = private;
650         return private;
651 
652 out_free:
653         kfree(private);
654 out:
655         return NULL;
656 }
657 EXPORT_SYMBOL(__seq_open_private);
658 
659 int seq_open_private(struct file *filp, const struct seq_operations *ops,
660                 int psize)
661 {
662         return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM;
663 }
664 EXPORT_SYMBOL(seq_open_private);
665 
666 int seq_putc(struct seq_file *m, char c)
667 {
668         if (m->count < m->size) {
669                 m->buf[m->count++] = c;
670                 return 0;
671         }
672         return -1;
673 }
674 EXPORT_SYMBOL(seq_putc);
675 
676 int seq_puts(struct seq_file *m, const char *s)
677 {
678         int len = strlen(s);
679         if (m->count + len < m->size) {
680                 memcpy(m->buf + m->count, s, len);
681                 m->count += len;
682                 return 0;
683         }
684         seq_set_overflow(m);
685         return -1;
686 }
687 EXPORT_SYMBOL(seq_puts);
688 
689 /*
690  * A helper routine for putting decimal numbers without rich format of printf().
691  * only 'unsigned long long' is supported.
692  * This routine will put one byte delimiter + number into seq_file.
693  * This routine is very quick when you show lots of numbers.
694  * In usual cases, it will be better to use seq_printf(). It's easier to read.
695  */
696 int seq_put_decimal_ull(struct seq_file *m, char delimiter,
697                         unsigned long long num)
698 {
699         int len;
700 
701         if (m->count + 2 >= m->size) /* we'll write 2 bytes at least */
702                 goto overflow;
703 
704         if (delimiter)
705                 m->buf[m->count++] = delimiter;
706 
707         if (num < 10) {
708                 m->buf[m->count++] = num + '';
709                 return 0;
710         }
711 
712         len = num_to_str(m->buf + m->count, m->size - m->count, num);
713         if (!len)
714                 goto overflow;
715         m->count += len;
716         return 0;
717 overflow:
718         seq_set_overflow(m);
719         return -1;
720 }
721 EXPORT_SYMBOL(seq_put_decimal_ull);
722 
723 int seq_put_decimal_ll(struct seq_file *m, char delimiter,
724                         long long num)
725 {
726         if (num < 0) {
727                 if (m->count + 3 >= m->size) {
728                         seq_set_overflow(m);
729                         return -1;
730                 }
731                 if (delimiter)
732                         m->buf[m->count++] = delimiter;
733                 num = -num;
734                 delimiter = '-';
735         }
736         return seq_put_decimal_ull(m, delimiter, num);
737 
738 }
739 EXPORT_SYMBOL(seq_put_decimal_ll);
740 
741 /**
742  * seq_write - write arbitrary data to buffer
743  * @seq: seq_file identifying the buffer to which data should be written
744  * @data: data address
745  * @len: number of bytes
746  *
747  * Return 0 on success, non-zero otherwise.
748  */
749 int seq_write(struct seq_file *seq, const void *data, size_t len)
750 {
751         if (seq->count + len < seq->size) {
752                 memcpy(seq->buf + seq->count, data, len);
753                 seq->count += len;
754                 return 0;
755         }
756         seq_set_overflow(seq);
757         return -1;
758 }
759 EXPORT_SYMBOL(seq_write);
760 
761 /**
762  * seq_pad - write padding spaces to buffer
763  * @m: seq_file identifying the buffer to which data should be written
764  * @c: the byte to append after padding if non-zero
765  */
766 void seq_pad(struct seq_file *m, char c)
767 {
768         int size = m->pad_until - m->count;
769         if (size > 0)
770                 seq_printf(m, "%*s", size, "");
771         if (c)
772                 seq_putc(m, c);
773 }
774 EXPORT_SYMBOL(seq_pad);
775 
776 struct list_head *seq_list_start(struct list_head *head, loff_t pos)
777 {
778         struct list_head *lh;
779 
780         list_for_each(lh, head)
781                 if (pos-- == 0)
782                         return lh;
783 
784         return NULL;
785 }
786 EXPORT_SYMBOL(seq_list_start);
787 
788 struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
789 {
790         if (!pos)
791                 return head;
792 
793         return seq_list_start(head, pos - 1);
794 }
795 EXPORT_SYMBOL(seq_list_start_head);
796 
797 struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
798 {
799         struct list_head *lh;
800 
801         lh = ((struct list_head *)v)->next;
802         ++*ppos;
803         return lh == head ? NULL : lh;
804 }
805 EXPORT_SYMBOL(seq_list_next);
806 
807 /**
808  * seq_hlist_start - start an iteration of a hlist
809  * @head: the head of the hlist
810  * @pos:  the start position of the sequence
811  *
812  * Called at seq_file->op->start().
813  */
814 struct hlist_node *seq_hlist_start(struct hlist_head *head, loff_t pos)
815 {
816         struct hlist_node *node;
817 
818         hlist_for_each(node, head)
819                 if (pos-- == 0)
820                         return node;
821         return NULL;
822 }
823 EXPORT_SYMBOL(seq_hlist_start);
824 
825 /**
826  * seq_hlist_start_head - start an iteration of a hlist
827  * @head: the head of the hlist
828  * @pos:  the start position of the sequence
829  *
830  * Called at seq_file->op->start(). Call this function if you want to
831  * print a header at the top of the output.
832  */
833 struct hlist_node *seq_hlist_start_head(struct hlist_head *head, loff_t pos)
834 {
835         if (!pos)
836                 return SEQ_START_TOKEN;
837 
838         return seq_hlist_start(head, pos - 1);
839 }
840 EXPORT_SYMBOL(seq_hlist_start_head);
841 
842 /**
843  * seq_hlist_next - move to the next position of the hlist
844  * @v:    the current iterator
845  * @head: the head of the hlist
846  * @ppos: the current position
847  *
848  * Called at seq_file->op->next().
849  */
850 struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head,
851                                   loff_t *ppos)
852 {
853         struct hlist_node *node = v;
854 
855         ++*ppos;
856         if (v == SEQ_START_TOKEN)
857                 return head->first;
858         else
859                 return node->next;
860 }
861 EXPORT_SYMBOL(seq_hlist_next);
862 
863 /**
864  * seq_hlist_start_rcu - start an iteration of a hlist protected by RCU
865  * @head: the head of the hlist
866  * @pos:  the start position of the sequence
867  *
868  * Called at seq_file->op->start().
869  *
870  * This list-traversal primitive may safely run concurrently with
871  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
872  * as long as the traversal is guarded by rcu_read_lock().
873  */
874 struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head,
875                                        loff_t pos)
876 {
877         struct hlist_node *node;
878 
879         __hlist_for_each_rcu(node, head)
880                 if (pos-- == 0)
881                         return node;
882         return NULL;
883 }
884 EXPORT_SYMBOL(seq_hlist_start_rcu);
885 
886 /**
887  * seq_hlist_start_head_rcu - start an iteration of a hlist protected by RCU
888  * @head: the head of the hlist
889  * @pos:  the start position of the sequence
890  *
891  * Called at seq_file->op->start(). Call this function if you want to
892  * print a header at the top of the output.
893  *
894  * This list-traversal primitive may safely run concurrently with
895  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
896  * as long as the traversal is guarded by rcu_read_lock().
897  */
898 struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,
899                                             loff_t pos)
900 {
901         if (!pos)
902                 return SEQ_START_TOKEN;
903 
904         return seq_hlist_start_rcu(head, pos - 1);
905 }
906 EXPORT_SYMBOL(seq_hlist_start_head_rcu);
907 
908 /**
909  * seq_hlist_next_rcu - move to the next position of the hlist protected by RCU
910  * @v:    the current iterator
911  * @head: the head of the hlist
912  * @ppos: the current position
913  *
914  * Called at seq_file->op->next().
915  *
916  * This list-traversal primitive may safely run concurrently with
917  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
918  * as long as the traversal is guarded by rcu_read_lock().
919  */
920 struct hlist_node *seq_hlist_next_rcu(void *v,
921                                       struct hlist_head *head,
922                                       loff_t *ppos)
923 {
924         struct hlist_node *node = v;
925 
926         ++*ppos;
927         if (v == SEQ_START_TOKEN)
928                 return rcu_dereference(head->first);
929         else
930                 return rcu_dereference(node->next);
931 }
932 EXPORT_SYMBOL(seq_hlist_next_rcu);
933 
934 /**
935  * seq_hlist_start_precpu - start an iteration of a percpu hlist array
936  * @head: pointer to percpu array of struct hlist_heads
937  * @cpu:  pointer to cpu "cursor"
938  * @pos:  start position of sequence
939  *
940  * Called at seq_file->op->start().
941  */
942 struct hlist_node *
943 seq_hlist_start_percpu(struct hlist_head __percpu *head, int *cpu, loff_t pos)
944 {
945         struct hlist_node *node;
946 
947         for_each_possible_cpu(*cpu) {
948                 hlist_for_each(node, per_cpu_ptr(head, *cpu)) {
949                         if (pos-- == 0)
950                                 return node;
951                 }
952         }
953         return NULL;
954 }
955 EXPORT_SYMBOL(seq_hlist_start_percpu);
956 
957 /**
958  * seq_hlist_next_percpu - move to the next position of the percpu hlist array
959  * @v:    pointer to current hlist_node
960  * @head: pointer to percpu array of struct hlist_heads
961  * @cpu:  pointer to cpu "cursor"
962  * @pos:  start position of sequence
963  *
964  * Called at seq_file->op->next().
965  */
966 struct hlist_node *
967 seq_hlist_next_percpu(void *v, struct hlist_head __percpu *head,
968                         int *cpu, loff_t *pos)
969 {
970         struct hlist_node *node = v;
971 
972         ++*pos;
973 
974         if (node->next)
975                 return node->next;
976 
977         for (*cpu = cpumask_next(*cpu, cpu_possible_mask); *cpu < nr_cpu_ids;
978              *cpu = cpumask_next(*cpu, cpu_possible_mask)) {
979                 struct hlist_head *bucket = per_cpu_ptr(head, *cpu);
980 
981                 if (!hlist_empty(bucket))
982                         return bucket->first;
983         }
984         return NULL;
985 }
986 EXPORT_SYMBOL(seq_hlist_next_percpu);
987 

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