cifs: don't instantiate new dentries in readdir for inodes that need to be revalidate...
[linux-3.10.git] / fs / nilfs2 / cpfile.c
1 /*
2  * cpfile.c - NILFS checkpoint file.
3  *
4  * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License as published by
8  * the Free Software Foundation; either version 2 of the License, or
9  * (at your option) any later version.
10  *
11  * This program is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14  * GNU General Public License for more details.
15  *
16  * You should have received a copy of the GNU General Public License
17  * along with this program; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
19  *
20  * Written by Koji Sato <koji@osrg.net>.
21  */
22
23 #include <linux/kernel.h>
24 #include <linux/fs.h>
25 #include <linux/string.h>
26 #include <linux/buffer_head.h>
27 #include <linux/errno.h>
28 #include <linux/nilfs2_fs.h>
29 #include "mdt.h"
30 #include "cpfile.h"
31
32
33 static inline unsigned long
34 nilfs_cpfile_checkpoints_per_block(const struct inode *cpfile)
35 {
36         return NILFS_MDT(cpfile)->mi_entries_per_block;
37 }
38
39 /* block number from the beginning of the file */
40 static unsigned long
41 nilfs_cpfile_get_blkoff(const struct inode *cpfile, __u64 cno)
42 {
43         __u64 tcno = cno + NILFS_MDT(cpfile)->mi_first_entry_offset - 1;
44         do_div(tcno, nilfs_cpfile_checkpoints_per_block(cpfile));
45         return (unsigned long)tcno;
46 }
47
48 /* offset in block */
49 static unsigned long
50 nilfs_cpfile_get_offset(const struct inode *cpfile, __u64 cno)
51 {
52         __u64 tcno = cno + NILFS_MDT(cpfile)->mi_first_entry_offset - 1;
53         return do_div(tcno, nilfs_cpfile_checkpoints_per_block(cpfile));
54 }
55
56 static unsigned long
57 nilfs_cpfile_checkpoints_in_block(const struct inode *cpfile,
58                                   __u64 curr,
59                                   __u64 max)
60 {
61         return min_t(__u64,
62                      nilfs_cpfile_checkpoints_per_block(cpfile) -
63                      nilfs_cpfile_get_offset(cpfile, curr),
64                      max - curr);
65 }
66
67 static inline int nilfs_cpfile_is_in_first(const struct inode *cpfile,
68                                            __u64 cno)
69 {
70         return nilfs_cpfile_get_blkoff(cpfile, cno) == 0;
71 }
72
73 static unsigned int
74 nilfs_cpfile_block_add_valid_checkpoints(const struct inode *cpfile,
75                                          struct buffer_head *bh,
76                                          void *kaddr,
77                                          unsigned int n)
78 {
79         struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
80         unsigned int count;
81
82         count = le32_to_cpu(cp->cp_checkpoints_count) + n;
83         cp->cp_checkpoints_count = cpu_to_le32(count);
84         return count;
85 }
86
87 static unsigned int
88 nilfs_cpfile_block_sub_valid_checkpoints(const struct inode *cpfile,
89                                          struct buffer_head *bh,
90                                          void *kaddr,
91                                          unsigned int n)
92 {
93         struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
94         unsigned int count;
95
96         WARN_ON(le32_to_cpu(cp->cp_checkpoints_count) < n);
97         count = le32_to_cpu(cp->cp_checkpoints_count) - n;
98         cp->cp_checkpoints_count = cpu_to_le32(count);
99         return count;
100 }
101
102 static inline struct nilfs_cpfile_header *
103 nilfs_cpfile_block_get_header(const struct inode *cpfile,
104                               struct buffer_head *bh,
105                               void *kaddr)
106 {
107         return kaddr + bh_offset(bh);
108 }
109
110 static struct nilfs_checkpoint *
111 nilfs_cpfile_block_get_checkpoint(const struct inode *cpfile, __u64 cno,
112                                   struct buffer_head *bh,
113                                   void *kaddr)
114 {
115         return kaddr + bh_offset(bh) + nilfs_cpfile_get_offset(cpfile, cno) *
116                 NILFS_MDT(cpfile)->mi_entry_size;
117 }
118
119 static void nilfs_cpfile_block_init(struct inode *cpfile,
120                                     struct buffer_head *bh,
121                                     void *kaddr)
122 {
123         struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
124         size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
125         int n = nilfs_cpfile_checkpoints_per_block(cpfile);
126
127         while (n-- > 0) {
128                 nilfs_checkpoint_set_invalid(cp);
129                 cp = (void *)cp + cpsz;
130         }
131 }
132
133 static inline int nilfs_cpfile_get_header_block(struct inode *cpfile,
134                                                 struct buffer_head **bhp)
135 {
136         return nilfs_mdt_get_block(cpfile, 0, 0, NULL, bhp);
137 }
138
139 static inline int nilfs_cpfile_get_checkpoint_block(struct inode *cpfile,
140                                                     __u64 cno,
141                                                     int create,
142                                                     struct buffer_head **bhp)
143 {
144         return nilfs_mdt_get_block(cpfile,
145                                    nilfs_cpfile_get_blkoff(cpfile, cno),
146                                    create, nilfs_cpfile_block_init, bhp);
147 }
148
149 static inline int nilfs_cpfile_delete_checkpoint_block(struct inode *cpfile,
150                                                        __u64 cno)
151 {
152         return nilfs_mdt_delete_block(cpfile,
153                                       nilfs_cpfile_get_blkoff(cpfile, cno));
154 }
155
156 /**
157  * nilfs_cpfile_get_checkpoint - get a checkpoint
158  * @cpfile: inode of checkpoint file
159  * @cno: checkpoint number
160  * @create: create flag
161  * @cpp: pointer to a checkpoint
162  * @bhp: pointer to a buffer head
163  *
164  * Description: nilfs_cpfile_get_checkpoint() acquires the checkpoint
165  * specified by @cno. A new checkpoint will be created if @cno is the current
166  * checkpoint number and @create is nonzero.
167  *
168  * Return Value: On success, 0 is returned, and the checkpoint and the
169  * buffer head of the buffer on which the checkpoint is located are stored in
170  * the place pointed by @cpp and @bhp, respectively. On error, one of the
171  * following negative error codes is returned.
172  *
173  * %-EIO - I/O error.
174  *
175  * %-ENOMEM - Insufficient amount of memory available.
176  *
177  * %-ENOENT - No such checkpoint.
178  *
179  * %-EINVAL - invalid checkpoint.
180  */
181 int nilfs_cpfile_get_checkpoint(struct inode *cpfile,
182                                 __u64 cno,
183                                 int create,
184                                 struct nilfs_checkpoint **cpp,
185                                 struct buffer_head **bhp)
186 {
187         struct buffer_head *header_bh, *cp_bh;
188         struct nilfs_cpfile_header *header;
189         struct nilfs_checkpoint *cp;
190         void *kaddr;
191         int ret;
192
193         if (unlikely(cno < 1 || cno > nilfs_mdt_cno(cpfile) ||
194                      (cno < nilfs_mdt_cno(cpfile) && create)))
195                 return -EINVAL;
196
197         down_write(&NILFS_MDT(cpfile)->mi_sem);
198
199         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
200         if (ret < 0)
201                 goto out_sem;
202         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, create, &cp_bh);
203         if (ret < 0)
204                 goto out_header;
205         kaddr = kmap(cp_bh->b_page);
206         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
207         if (nilfs_checkpoint_invalid(cp)) {
208                 if (!create) {
209                         kunmap(cp_bh->b_page);
210                         brelse(cp_bh);
211                         ret = -ENOENT;
212                         goto out_header;
213                 }
214                 /* a newly-created checkpoint */
215                 nilfs_checkpoint_clear_invalid(cp);
216                 if (!nilfs_cpfile_is_in_first(cpfile, cno))
217                         nilfs_cpfile_block_add_valid_checkpoints(cpfile, cp_bh,
218                                                                  kaddr, 1);
219                 mark_buffer_dirty(cp_bh);
220
221                 kaddr = kmap_atomic(header_bh->b_page);
222                 header = nilfs_cpfile_block_get_header(cpfile, header_bh,
223                                                        kaddr);
224                 le64_add_cpu(&header->ch_ncheckpoints, 1);
225                 kunmap_atomic(kaddr);
226                 mark_buffer_dirty(header_bh);
227                 nilfs_mdt_mark_dirty(cpfile);
228         }
229
230         if (cpp != NULL)
231                 *cpp = cp;
232         *bhp = cp_bh;
233
234  out_header:
235         brelse(header_bh);
236
237  out_sem:
238         up_write(&NILFS_MDT(cpfile)->mi_sem);
239         return ret;
240 }
241
242 /**
243  * nilfs_cpfile_put_checkpoint - put a checkpoint
244  * @cpfile: inode of checkpoint file
245  * @cno: checkpoint number
246  * @bh: buffer head
247  *
248  * Description: nilfs_cpfile_put_checkpoint() releases the checkpoint
249  * specified by @cno. @bh must be the buffer head which has been returned by
250  * a previous call to nilfs_cpfile_get_checkpoint() with @cno.
251  */
252 void nilfs_cpfile_put_checkpoint(struct inode *cpfile, __u64 cno,
253                                  struct buffer_head *bh)
254 {
255         kunmap(bh->b_page);
256         brelse(bh);
257 }
258
259 /**
260  * nilfs_cpfile_delete_checkpoints - delete checkpoints
261  * @cpfile: inode of checkpoint file
262  * @start: start checkpoint number
263  * @end: end checkpoint numer
264  *
265  * Description: nilfs_cpfile_delete_checkpoints() deletes the checkpoints in
266  * the period from @start to @end, excluding @end itself. The checkpoints
267  * which have been already deleted are ignored.
268  *
269  * Return Value: On success, 0 is returned. On error, one of the following
270  * negative error codes is returned.
271  *
272  * %-EIO - I/O error.
273  *
274  * %-ENOMEM - Insufficient amount of memory available.
275  *
276  * %-EINVAL - invalid checkpoints.
277  */
278 int nilfs_cpfile_delete_checkpoints(struct inode *cpfile,
279                                     __u64 start,
280                                     __u64 end)
281 {
282         struct buffer_head *header_bh, *cp_bh;
283         struct nilfs_cpfile_header *header;
284         struct nilfs_checkpoint *cp;
285         size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
286         __u64 cno;
287         void *kaddr;
288         unsigned long tnicps;
289         int ret, ncps, nicps, nss, count, i;
290
291         if (unlikely(start == 0 || start > end)) {
292                 printk(KERN_ERR "%s: invalid range of checkpoint numbers: "
293                        "[%llu, %llu)\n", __func__,
294                        (unsigned long long)start, (unsigned long long)end);
295                 return -EINVAL;
296         }
297
298         down_write(&NILFS_MDT(cpfile)->mi_sem);
299
300         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
301         if (ret < 0)
302                 goto out_sem;
303         tnicps = 0;
304         nss = 0;
305
306         for (cno = start; cno < end; cno += ncps) {
307                 ncps = nilfs_cpfile_checkpoints_in_block(cpfile, cno, end);
308                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
309                 if (ret < 0) {
310                         if (ret != -ENOENT)
311                                 break;
312                         /* skip hole */
313                         ret = 0;
314                         continue;
315                 }
316
317                 kaddr = kmap_atomic(cp_bh->b_page);
318                 cp = nilfs_cpfile_block_get_checkpoint(
319                         cpfile, cno, cp_bh, kaddr);
320                 nicps = 0;
321                 for (i = 0; i < ncps; i++, cp = (void *)cp + cpsz) {
322                         if (nilfs_checkpoint_snapshot(cp)) {
323                                 nss++;
324                         } else if (!nilfs_checkpoint_invalid(cp)) {
325                                 nilfs_checkpoint_set_invalid(cp);
326                                 nicps++;
327                         }
328                 }
329                 if (nicps > 0) {
330                         tnicps += nicps;
331                         mark_buffer_dirty(cp_bh);
332                         nilfs_mdt_mark_dirty(cpfile);
333                         if (!nilfs_cpfile_is_in_first(cpfile, cno)) {
334                                 count =
335                                   nilfs_cpfile_block_sub_valid_checkpoints(
336                                                 cpfile, cp_bh, kaddr, nicps);
337                                 if (count == 0) {
338                                         /* make hole */
339                                         kunmap_atomic(kaddr);
340                                         brelse(cp_bh);
341                                         ret =
342                                           nilfs_cpfile_delete_checkpoint_block(
343                                                                    cpfile, cno);
344                                         if (ret == 0)
345                                                 continue;
346                                         printk(KERN_ERR
347                                                "%s: cannot delete block\n",
348                                                __func__);
349                                         break;
350                                 }
351                         }
352                 }
353
354                 kunmap_atomic(kaddr);
355                 brelse(cp_bh);
356         }
357
358         if (tnicps > 0) {
359                 kaddr = kmap_atomic(header_bh->b_page);
360                 header = nilfs_cpfile_block_get_header(cpfile, header_bh,
361                                                        kaddr);
362                 le64_add_cpu(&header->ch_ncheckpoints, -(u64)tnicps);
363                 mark_buffer_dirty(header_bh);
364                 nilfs_mdt_mark_dirty(cpfile);
365                 kunmap_atomic(kaddr);
366         }
367
368         brelse(header_bh);
369         if (nss > 0)
370                 ret = -EBUSY;
371
372  out_sem:
373         up_write(&NILFS_MDT(cpfile)->mi_sem);
374         return ret;
375 }
376
377 static void nilfs_cpfile_checkpoint_to_cpinfo(struct inode *cpfile,
378                                               struct nilfs_checkpoint *cp,
379                                               struct nilfs_cpinfo *ci)
380 {
381         ci->ci_flags = le32_to_cpu(cp->cp_flags);
382         ci->ci_cno = le64_to_cpu(cp->cp_cno);
383         ci->ci_create = le64_to_cpu(cp->cp_create);
384         ci->ci_nblk_inc = le64_to_cpu(cp->cp_nblk_inc);
385         ci->ci_inodes_count = le64_to_cpu(cp->cp_inodes_count);
386         ci->ci_blocks_count = le64_to_cpu(cp->cp_blocks_count);
387         ci->ci_next = le64_to_cpu(cp->cp_snapshot_list.ssl_next);
388 }
389
390 static ssize_t nilfs_cpfile_do_get_cpinfo(struct inode *cpfile, __u64 *cnop,
391                                           void *buf, unsigned cisz, size_t nci)
392 {
393         struct nilfs_checkpoint *cp;
394         struct nilfs_cpinfo *ci = buf;
395         struct buffer_head *bh;
396         size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
397         __u64 cur_cno = nilfs_mdt_cno(cpfile), cno = *cnop;
398         void *kaddr;
399         int n, ret;
400         int ncps, i;
401
402         if (cno == 0)
403                 return -ENOENT; /* checkpoint number 0 is invalid */
404         down_read(&NILFS_MDT(cpfile)->mi_sem);
405
406         for (n = 0; cno < cur_cno && n < nci; cno += ncps) {
407                 ncps = nilfs_cpfile_checkpoints_in_block(cpfile, cno, cur_cno);
408                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &bh);
409                 if (ret < 0) {
410                         if (ret != -ENOENT)
411                                 goto out;
412                         continue; /* skip hole */
413                 }
414
415                 kaddr = kmap_atomic(bh->b_page);
416                 cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
417                 for (i = 0; i < ncps && n < nci; i++, cp = (void *)cp + cpsz) {
418                         if (!nilfs_checkpoint_invalid(cp)) {
419                                 nilfs_cpfile_checkpoint_to_cpinfo(cpfile, cp,
420                                                                   ci);
421                                 ci = (void *)ci + cisz;
422                                 n++;
423                         }
424                 }
425                 kunmap_atomic(kaddr);
426                 brelse(bh);
427         }
428
429         ret = n;
430         if (n > 0) {
431                 ci = (void *)ci - cisz;
432                 *cnop = ci->ci_cno + 1;
433         }
434
435  out:
436         up_read(&NILFS_MDT(cpfile)->mi_sem);
437         return ret;
438 }
439
440 static ssize_t nilfs_cpfile_do_get_ssinfo(struct inode *cpfile, __u64 *cnop,
441                                           void *buf, unsigned cisz, size_t nci)
442 {
443         struct buffer_head *bh;
444         struct nilfs_cpfile_header *header;
445         struct nilfs_checkpoint *cp;
446         struct nilfs_cpinfo *ci = buf;
447         __u64 curr = *cnop, next;
448         unsigned long curr_blkoff, next_blkoff;
449         void *kaddr;
450         int n = 0, ret;
451
452         down_read(&NILFS_MDT(cpfile)->mi_sem);
453
454         if (curr == 0) {
455                 ret = nilfs_cpfile_get_header_block(cpfile, &bh);
456                 if (ret < 0)
457                         goto out;
458                 kaddr = kmap_atomic(bh->b_page);
459                 header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
460                 curr = le64_to_cpu(header->ch_snapshot_list.ssl_next);
461                 kunmap_atomic(kaddr);
462                 brelse(bh);
463                 if (curr == 0) {
464                         ret = 0;
465                         goto out;
466                 }
467         } else if (unlikely(curr == ~(__u64)0)) {
468                 ret = 0;
469                 goto out;
470         }
471
472         curr_blkoff = nilfs_cpfile_get_blkoff(cpfile, curr);
473         ret = nilfs_cpfile_get_checkpoint_block(cpfile, curr, 0, &bh);
474         if (unlikely(ret < 0)) {
475                 if (ret == -ENOENT)
476                         ret = 0; /* No snapshots (started from a hole block) */
477                 goto out;
478         }
479         kaddr = kmap_atomic(bh->b_page);
480         while (n < nci) {
481                 cp = nilfs_cpfile_block_get_checkpoint(cpfile, curr, bh, kaddr);
482                 curr = ~(__u64)0; /* Terminator */
483                 if (unlikely(nilfs_checkpoint_invalid(cp) ||
484                              !nilfs_checkpoint_snapshot(cp)))
485                         break;
486                 nilfs_cpfile_checkpoint_to_cpinfo(cpfile, cp, ci);
487                 ci = (void *)ci + cisz;
488                 n++;
489                 next = le64_to_cpu(cp->cp_snapshot_list.ssl_next);
490                 if (next == 0)
491                         break; /* reach end of the snapshot list */
492
493                 next_blkoff = nilfs_cpfile_get_blkoff(cpfile, next);
494                 if (curr_blkoff != next_blkoff) {
495                         kunmap_atomic(kaddr);
496                         brelse(bh);
497                         ret = nilfs_cpfile_get_checkpoint_block(cpfile, next,
498                                                                 0, &bh);
499                         if (unlikely(ret < 0)) {
500                                 WARN_ON(ret == -ENOENT);
501                                 goto out;
502                         }
503                         kaddr = kmap_atomic(bh->b_page);
504                 }
505                 curr = next;
506                 curr_blkoff = next_blkoff;
507         }
508         kunmap_atomic(kaddr);
509         brelse(bh);
510         *cnop = curr;
511         ret = n;
512
513  out:
514         up_read(&NILFS_MDT(cpfile)->mi_sem);
515         return ret;
516 }
517
518 /**
519  * nilfs_cpfile_get_cpinfo -
520  * @cpfile:
521  * @cno:
522  * @ci:
523  * @nci:
524  */
525
526 ssize_t nilfs_cpfile_get_cpinfo(struct inode *cpfile, __u64 *cnop, int mode,
527                                 void *buf, unsigned cisz, size_t nci)
528 {
529         switch (mode) {
530         case NILFS_CHECKPOINT:
531                 return nilfs_cpfile_do_get_cpinfo(cpfile, cnop, buf, cisz, nci);
532         case NILFS_SNAPSHOT:
533                 return nilfs_cpfile_do_get_ssinfo(cpfile, cnop, buf, cisz, nci);
534         default:
535                 return -EINVAL;
536         }
537 }
538
539 /**
540  * nilfs_cpfile_delete_checkpoint -
541  * @cpfile:
542  * @cno:
543  */
544 int nilfs_cpfile_delete_checkpoint(struct inode *cpfile, __u64 cno)
545 {
546         struct nilfs_cpinfo ci;
547         __u64 tcno = cno;
548         ssize_t nci;
549
550         nci = nilfs_cpfile_do_get_cpinfo(cpfile, &tcno, &ci, sizeof(ci), 1);
551         if (nci < 0)
552                 return nci;
553         else if (nci == 0 || ci.ci_cno != cno)
554                 return -ENOENT;
555         else if (nilfs_cpinfo_snapshot(&ci))
556                 return -EBUSY;
557
558         return nilfs_cpfile_delete_checkpoints(cpfile, cno, cno + 1);
559 }
560
561 static struct nilfs_snapshot_list *
562 nilfs_cpfile_block_get_snapshot_list(const struct inode *cpfile,
563                                      __u64 cno,
564                                      struct buffer_head *bh,
565                                      void *kaddr)
566 {
567         struct nilfs_cpfile_header *header;
568         struct nilfs_checkpoint *cp;
569         struct nilfs_snapshot_list *list;
570
571         if (cno != 0) {
572                 cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
573                 list = &cp->cp_snapshot_list;
574         } else {
575                 header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
576                 list = &header->ch_snapshot_list;
577         }
578         return list;
579 }
580
581 static int nilfs_cpfile_set_snapshot(struct inode *cpfile, __u64 cno)
582 {
583         struct buffer_head *header_bh, *curr_bh, *prev_bh, *cp_bh;
584         struct nilfs_cpfile_header *header;
585         struct nilfs_checkpoint *cp;
586         struct nilfs_snapshot_list *list;
587         __u64 curr, prev;
588         unsigned long curr_blkoff, prev_blkoff;
589         void *kaddr;
590         int ret;
591
592         if (cno == 0)
593                 return -ENOENT; /* checkpoint number 0 is invalid */
594         down_write(&NILFS_MDT(cpfile)->mi_sem);
595
596         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
597         if (ret < 0)
598                 goto out_sem;
599         kaddr = kmap_atomic(cp_bh->b_page);
600         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
601         if (nilfs_checkpoint_invalid(cp)) {
602                 ret = -ENOENT;
603                 kunmap_atomic(kaddr);
604                 goto out_cp;
605         }
606         if (nilfs_checkpoint_snapshot(cp)) {
607                 ret = 0;
608                 kunmap_atomic(kaddr);
609                 goto out_cp;
610         }
611         kunmap_atomic(kaddr);
612
613         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
614         if (ret < 0)
615                 goto out_cp;
616         kaddr = kmap_atomic(header_bh->b_page);
617         header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
618         list = &header->ch_snapshot_list;
619         curr_bh = header_bh;
620         get_bh(curr_bh);
621         curr = 0;
622         curr_blkoff = 0;
623         prev = le64_to_cpu(list->ssl_prev);
624         while (prev > cno) {
625                 prev_blkoff = nilfs_cpfile_get_blkoff(cpfile, prev);
626                 curr = prev;
627                 if (curr_blkoff != prev_blkoff) {
628                         kunmap_atomic(kaddr);
629                         brelse(curr_bh);
630                         ret = nilfs_cpfile_get_checkpoint_block(cpfile, curr,
631                                                                 0, &curr_bh);
632                         if (ret < 0)
633                                 goto out_header;
634                         kaddr = kmap_atomic(curr_bh->b_page);
635                 }
636                 curr_blkoff = prev_blkoff;
637                 cp = nilfs_cpfile_block_get_checkpoint(
638                         cpfile, curr, curr_bh, kaddr);
639                 list = &cp->cp_snapshot_list;
640                 prev = le64_to_cpu(list->ssl_prev);
641         }
642         kunmap_atomic(kaddr);
643
644         if (prev != 0) {
645                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, prev, 0,
646                                                         &prev_bh);
647                 if (ret < 0)
648                         goto out_curr;
649         } else {
650                 prev_bh = header_bh;
651                 get_bh(prev_bh);
652         }
653
654         kaddr = kmap_atomic(curr_bh->b_page);
655         list = nilfs_cpfile_block_get_snapshot_list(
656                 cpfile, curr, curr_bh, kaddr);
657         list->ssl_prev = cpu_to_le64(cno);
658         kunmap_atomic(kaddr);
659
660         kaddr = kmap_atomic(cp_bh->b_page);
661         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
662         cp->cp_snapshot_list.ssl_next = cpu_to_le64(curr);
663         cp->cp_snapshot_list.ssl_prev = cpu_to_le64(prev);
664         nilfs_checkpoint_set_snapshot(cp);
665         kunmap_atomic(kaddr);
666
667         kaddr = kmap_atomic(prev_bh->b_page);
668         list = nilfs_cpfile_block_get_snapshot_list(
669                 cpfile, prev, prev_bh, kaddr);
670         list->ssl_next = cpu_to_le64(cno);
671         kunmap_atomic(kaddr);
672
673         kaddr = kmap_atomic(header_bh->b_page);
674         header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
675         le64_add_cpu(&header->ch_nsnapshots, 1);
676         kunmap_atomic(kaddr);
677
678         mark_buffer_dirty(prev_bh);
679         mark_buffer_dirty(curr_bh);
680         mark_buffer_dirty(cp_bh);
681         mark_buffer_dirty(header_bh);
682         nilfs_mdt_mark_dirty(cpfile);
683
684         brelse(prev_bh);
685
686  out_curr:
687         brelse(curr_bh);
688
689  out_header:
690         brelse(header_bh);
691
692  out_cp:
693         brelse(cp_bh);
694
695  out_sem:
696         up_write(&NILFS_MDT(cpfile)->mi_sem);
697         return ret;
698 }
699
700 static int nilfs_cpfile_clear_snapshot(struct inode *cpfile, __u64 cno)
701 {
702         struct buffer_head *header_bh, *next_bh, *prev_bh, *cp_bh;
703         struct nilfs_cpfile_header *header;
704         struct nilfs_checkpoint *cp;
705         struct nilfs_snapshot_list *list;
706         __u64 next, prev;
707         void *kaddr;
708         int ret;
709
710         if (cno == 0)
711                 return -ENOENT; /* checkpoint number 0 is invalid */
712         down_write(&NILFS_MDT(cpfile)->mi_sem);
713
714         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
715         if (ret < 0)
716                 goto out_sem;
717         kaddr = kmap_atomic(cp_bh->b_page);
718         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
719         if (nilfs_checkpoint_invalid(cp)) {
720                 ret = -ENOENT;
721                 kunmap_atomic(kaddr);
722                 goto out_cp;
723         }
724         if (!nilfs_checkpoint_snapshot(cp)) {
725                 ret = 0;
726                 kunmap_atomic(kaddr);
727                 goto out_cp;
728         }
729
730         list = &cp->cp_snapshot_list;
731         next = le64_to_cpu(list->ssl_next);
732         prev = le64_to_cpu(list->ssl_prev);
733         kunmap_atomic(kaddr);
734
735         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
736         if (ret < 0)
737                 goto out_cp;
738         if (next != 0) {
739                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, next, 0,
740                                                         &next_bh);
741                 if (ret < 0)
742                         goto out_header;
743         } else {
744                 next_bh = header_bh;
745                 get_bh(next_bh);
746         }
747         if (prev != 0) {
748                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, prev, 0,
749                                                         &prev_bh);
750                 if (ret < 0)
751                         goto out_next;
752         } else {
753                 prev_bh = header_bh;
754                 get_bh(prev_bh);
755         }
756
757         kaddr = kmap_atomic(next_bh->b_page);
758         list = nilfs_cpfile_block_get_snapshot_list(
759                 cpfile, next, next_bh, kaddr);
760         list->ssl_prev = cpu_to_le64(prev);
761         kunmap_atomic(kaddr);
762
763         kaddr = kmap_atomic(prev_bh->b_page);
764         list = nilfs_cpfile_block_get_snapshot_list(
765                 cpfile, prev, prev_bh, kaddr);
766         list->ssl_next = cpu_to_le64(next);
767         kunmap_atomic(kaddr);
768
769         kaddr = kmap_atomic(cp_bh->b_page);
770         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
771         cp->cp_snapshot_list.ssl_next = cpu_to_le64(0);
772         cp->cp_snapshot_list.ssl_prev = cpu_to_le64(0);
773         nilfs_checkpoint_clear_snapshot(cp);
774         kunmap_atomic(kaddr);
775
776         kaddr = kmap_atomic(header_bh->b_page);
777         header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
778         le64_add_cpu(&header->ch_nsnapshots, -1);
779         kunmap_atomic(kaddr);
780
781         mark_buffer_dirty(next_bh);
782         mark_buffer_dirty(prev_bh);
783         mark_buffer_dirty(cp_bh);
784         mark_buffer_dirty(header_bh);
785         nilfs_mdt_mark_dirty(cpfile);
786
787         brelse(prev_bh);
788
789  out_next:
790         brelse(next_bh);
791
792  out_header:
793         brelse(header_bh);
794
795  out_cp:
796         brelse(cp_bh);
797
798  out_sem:
799         up_write(&NILFS_MDT(cpfile)->mi_sem);
800         return ret;
801 }
802
803 /**
804  * nilfs_cpfile_is_snapshot -
805  * @cpfile: inode of checkpoint file
806  * @cno: checkpoint number
807  *
808  * Description:
809  *
810  * Return Value: On success, 1 is returned if the checkpoint specified by
811  * @cno is a snapshot, or 0 if not. On error, one of the following negative
812  * error codes is returned.
813  *
814  * %-EIO - I/O error.
815  *
816  * %-ENOMEM - Insufficient amount of memory available.
817  *
818  * %-ENOENT - No such checkpoint.
819  */
820 int nilfs_cpfile_is_snapshot(struct inode *cpfile, __u64 cno)
821 {
822         struct buffer_head *bh;
823         struct nilfs_checkpoint *cp;
824         void *kaddr;
825         int ret;
826
827         /* CP number is invalid if it's zero or larger than the
828         largest exist one.*/
829         if (cno == 0 || cno >= nilfs_mdt_cno(cpfile))
830                 return -ENOENT;
831         down_read(&NILFS_MDT(cpfile)->mi_sem);
832
833         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &bh);
834         if (ret < 0)
835                 goto out;
836         kaddr = kmap_atomic(bh->b_page);
837         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
838         if (nilfs_checkpoint_invalid(cp))
839                 ret = -ENOENT;
840         else
841                 ret = nilfs_checkpoint_snapshot(cp);
842         kunmap_atomic(kaddr);
843         brelse(bh);
844
845  out:
846         up_read(&NILFS_MDT(cpfile)->mi_sem);
847         return ret;
848 }
849
850 /**
851  * nilfs_cpfile_change_cpmode - change checkpoint mode
852  * @cpfile: inode of checkpoint file
853  * @cno: checkpoint number
854  * @status: mode of checkpoint
855  *
856  * Description: nilfs_change_cpmode() changes the mode of the checkpoint
857  * specified by @cno. The mode @mode is NILFS_CHECKPOINT or NILFS_SNAPSHOT.
858  *
859  * Return Value: On success, 0 is returned. On error, one of the following
860  * negative error codes is returned.
861  *
862  * %-EIO - I/O error.
863  *
864  * %-ENOMEM - Insufficient amount of memory available.
865  *
866  * %-ENOENT - No such checkpoint.
867  */
868 int nilfs_cpfile_change_cpmode(struct inode *cpfile, __u64 cno, int mode)
869 {
870         int ret;
871
872         switch (mode) {
873         case NILFS_CHECKPOINT:
874                 if (nilfs_checkpoint_is_mounted(cpfile->i_sb, cno))
875                         /*
876                          * Current implementation does not have to protect
877                          * plain read-only mounts since they are exclusive
878                          * with a read/write mount and are protected from the
879                          * cleaner.
880                          */
881                         ret = -EBUSY;
882                 else
883                         ret = nilfs_cpfile_clear_snapshot(cpfile, cno);
884                 return ret;
885         case NILFS_SNAPSHOT:
886                 return nilfs_cpfile_set_snapshot(cpfile, cno);
887         default:
888                 return -EINVAL;
889         }
890 }
891
892 /**
893  * nilfs_cpfile_get_stat - get checkpoint statistics
894  * @cpfile: inode of checkpoint file
895  * @stat: pointer to a structure of checkpoint statistics
896  *
897  * Description: nilfs_cpfile_get_stat() returns information about checkpoints.
898  *
899  * Return Value: On success, 0 is returned, and checkpoints information is
900  * stored in the place pointed by @stat. On error, one of the following
901  * negative error codes is returned.
902  *
903  * %-EIO - I/O error.
904  *
905  * %-ENOMEM - Insufficient amount of memory available.
906  */
907 int nilfs_cpfile_get_stat(struct inode *cpfile, struct nilfs_cpstat *cpstat)
908 {
909         struct buffer_head *bh;
910         struct nilfs_cpfile_header *header;
911         void *kaddr;
912         int ret;
913
914         down_read(&NILFS_MDT(cpfile)->mi_sem);
915
916         ret = nilfs_cpfile_get_header_block(cpfile, &bh);
917         if (ret < 0)
918                 goto out_sem;
919         kaddr = kmap_atomic(bh->b_page);
920         header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
921         cpstat->cs_cno = nilfs_mdt_cno(cpfile);
922         cpstat->cs_ncps = le64_to_cpu(header->ch_ncheckpoints);
923         cpstat->cs_nsss = le64_to_cpu(header->ch_nsnapshots);
924         kunmap_atomic(kaddr);
925         brelse(bh);
926
927  out_sem:
928         up_read(&NILFS_MDT(cpfile)->mi_sem);
929         return ret;
930 }
931
932 /**
933  * nilfs_cpfile_read - read or get cpfile inode
934  * @sb: super block instance
935  * @cpsize: size of a checkpoint entry
936  * @raw_inode: on-disk cpfile inode
937  * @inodep: buffer to store the inode
938  */
939 int nilfs_cpfile_read(struct super_block *sb, size_t cpsize,
940                       struct nilfs_inode *raw_inode, struct inode **inodep)
941 {
942         struct inode *cpfile;
943         int err;
944
945         cpfile = nilfs_iget_locked(sb, NULL, NILFS_CPFILE_INO);
946         if (unlikely(!cpfile))
947                 return -ENOMEM;
948         if (!(cpfile->i_state & I_NEW))
949                 goto out;
950
951         err = nilfs_mdt_init(cpfile, NILFS_MDT_GFP, 0);
952         if (err)
953                 goto failed;
954
955         nilfs_mdt_set_entry_size(cpfile, cpsize,
956                                  sizeof(struct nilfs_cpfile_header));
957
958         err = nilfs_read_inode_common(cpfile, raw_inode);
959         if (err)
960                 goto failed;
961
962         unlock_new_inode(cpfile);
963  out:
964         *inodep = cpfile;
965         return 0;
966  failed:
967         iget_failed(cpfile);
968         return err;
969 }