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Linux/fs/nilfs2/cpfile.c

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  1 // SPDX-License-Identifier: GPL-2.0+
  2 /*
  3  * cpfile.c - NILFS checkpoint file.
  4  *
  5  * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
  6  *
  7  * Written by Koji Sato.
  8  */
  9 
 10 #include <linux/kernel.h>
 11 #include <linux/fs.h>
 12 #include <linux/string.h>
 13 #include <linux/buffer_head.h>
 14 #include <linux/errno.h>
 15 #include "mdt.h"
 16 #include "cpfile.h"
 17 
 18 
 19 static inline unsigned long
 20 nilfs_cpfile_checkpoints_per_block(const struct inode *cpfile)
 21 {
 22         return NILFS_MDT(cpfile)->mi_entries_per_block;
 23 }
 24 
 25 /* block number from the beginning of the file */
 26 static unsigned long
 27 nilfs_cpfile_get_blkoff(const struct inode *cpfile, __u64 cno)
 28 {
 29         __u64 tcno = cno + NILFS_MDT(cpfile)->mi_first_entry_offset - 1;
 30 
 31         do_div(tcno, nilfs_cpfile_checkpoints_per_block(cpfile));
 32         return (unsigned long)tcno;
 33 }
 34 
 35 /* offset in block */
 36 static unsigned long
 37 nilfs_cpfile_get_offset(const struct inode *cpfile, __u64 cno)
 38 {
 39         __u64 tcno = cno + NILFS_MDT(cpfile)->mi_first_entry_offset - 1;
 40 
 41         return do_div(tcno, nilfs_cpfile_checkpoints_per_block(cpfile));
 42 }
 43 
 44 static __u64 nilfs_cpfile_first_checkpoint_in_block(const struct inode *cpfile,
 45                                                     unsigned long blkoff)
 46 {
 47         return (__u64)nilfs_cpfile_checkpoints_per_block(cpfile) * blkoff
 48                 + 1 - NILFS_MDT(cpfile)->mi_first_entry_offset;
 49 }
 50 
 51 static unsigned long
 52 nilfs_cpfile_checkpoints_in_block(const struct inode *cpfile,
 53                                   __u64 curr,
 54                                   __u64 max)
 55 {
 56         return min_t(__u64,
 57                      nilfs_cpfile_checkpoints_per_block(cpfile) -
 58                      nilfs_cpfile_get_offset(cpfile, curr),
 59                      max - curr);
 60 }
 61 
 62 static inline int nilfs_cpfile_is_in_first(const struct inode *cpfile,
 63                                            __u64 cno)
 64 {
 65         return nilfs_cpfile_get_blkoff(cpfile, cno) == 0;
 66 }
 67 
 68 static unsigned int
 69 nilfs_cpfile_block_add_valid_checkpoints(const struct inode *cpfile,
 70                                          struct buffer_head *bh,
 71                                          void *kaddr,
 72                                          unsigned int n)
 73 {
 74         struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
 75         unsigned int count;
 76 
 77         count = le32_to_cpu(cp->cp_checkpoints_count) + n;
 78         cp->cp_checkpoints_count = cpu_to_le32(count);
 79         return count;
 80 }
 81 
 82 static unsigned int
 83 nilfs_cpfile_block_sub_valid_checkpoints(const struct inode *cpfile,
 84                                          struct buffer_head *bh,
 85                                          void *kaddr,
 86                                          unsigned int n)
 87 {
 88         struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
 89         unsigned int count;
 90 
 91         WARN_ON(le32_to_cpu(cp->cp_checkpoints_count) < n);
 92         count = le32_to_cpu(cp->cp_checkpoints_count) - n;
 93         cp->cp_checkpoints_count = cpu_to_le32(count);
 94         return count;
 95 }
 96 
 97 static inline struct nilfs_cpfile_header *
 98 nilfs_cpfile_block_get_header(const struct inode *cpfile,
 99                               struct buffer_head *bh,
100                               void *kaddr)
101 {
102         return kaddr + bh_offset(bh);
103 }
104 
105 static struct nilfs_checkpoint *
106 nilfs_cpfile_block_get_checkpoint(const struct inode *cpfile, __u64 cno,
107                                   struct buffer_head *bh,
108                                   void *kaddr)
109 {
110         return kaddr + bh_offset(bh) + nilfs_cpfile_get_offset(cpfile, cno) *
111                 NILFS_MDT(cpfile)->mi_entry_size;
112 }
113 
114 static void nilfs_cpfile_block_init(struct inode *cpfile,
115                                     struct buffer_head *bh,
116                                     void *kaddr)
117 {
118         struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
119         size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
120         int n = nilfs_cpfile_checkpoints_per_block(cpfile);
121 
122         while (n-- > 0) {
123                 nilfs_checkpoint_set_invalid(cp);
124                 cp = (void *)cp + cpsz;
125         }
126 }
127 
128 static inline int nilfs_cpfile_get_header_block(struct inode *cpfile,
129                                                 struct buffer_head **bhp)
130 {
131         return nilfs_mdt_get_block(cpfile, 0, 0, NULL, bhp);
132 }
133 
134 static inline int nilfs_cpfile_get_checkpoint_block(struct inode *cpfile,
135                                                     __u64 cno,
136                                                     int create,
137                                                     struct buffer_head **bhp)
138 {
139         return nilfs_mdt_get_block(cpfile,
140                                    nilfs_cpfile_get_blkoff(cpfile, cno),
141                                    create, nilfs_cpfile_block_init, bhp);
142 }
143 
144 /**
145  * nilfs_cpfile_find_checkpoint_block - find and get a buffer on cpfile
146  * @cpfile: inode of cpfile
147  * @start_cno: start checkpoint number (inclusive)
148  * @end_cno: end checkpoint number (inclusive)
149  * @cnop: place to store the next checkpoint number
150  * @bhp: place to store a pointer to buffer_head struct
151  *
152  * Return Value: On success, it returns 0. On error, the following negative
153  * error code is returned.
154  *
155  * %-ENOMEM - Insufficient memory available.
156  *
157  * %-EIO - I/O error
158  *
159  * %-ENOENT - no block exists in the range.
160  */
161 static int nilfs_cpfile_find_checkpoint_block(struct inode *cpfile,
162                                               __u64 start_cno, __u64 end_cno,
163                                               __u64 *cnop,
164                                               struct buffer_head **bhp)
165 {
166         unsigned long start, end, blkoff;
167         int ret;
168 
169         if (unlikely(start_cno > end_cno))
170                 return -ENOENT;
171 
172         start = nilfs_cpfile_get_blkoff(cpfile, start_cno);
173         end = nilfs_cpfile_get_blkoff(cpfile, end_cno);
174 
175         ret = nilfs_mdt_find_block(cpfile, start, end, &blkoff, bhp);
176         if (!ret)
177                 *cnop = (blkoff == start) ? start_cno :
178                         nilfs_cpfile_first_checkpoint_in_block(cpfile, blkoff);
179         return ret;
180 }
181 
182 static inline int nilfs_cpfile_delete_checkpoint_block(struct inode *cpfile,
183                                                        __u64 cno)
184 {
185         return nilfs_mdt_delete_block(cpfile,
186                                       nilfs_cpfile_get_blkoff(cpfile, cno));
187 }
188 
189 /**
190  * nilfs_cpfile_get_checkpoint - get a checkpoint
191  * @cpfile: inode of checkpoint file
192  * @cno: checkpoint number
193  * @create: create flag
194  * @cpp: pointer to a checkpoint
195  * @bhp: pointer to a buffer head
196  *
197  * Description: nilfs_cpfile_get_checkpoint() acquires the checkpoint
198  * specified by @cno. A new checkpoint will be created if @cno is the current
199  * checkpoint number and @create is nonzero.
200  *
201  * Return Value: On success, 0 is returned, and the checkpoint and the
202  * buffer head of the buffer on which the checkpoint is located are stored in
203  * the place pointed by @cpp and @bhp, respectively. On error, one of the
204  * following negative error codes is returned.
205  *
206  * %-EIO - I/O error.
207  *
208  * %-ENOMEM - Insufficient amount of memory available.
209  *
210  * %-ENOENT - No such checkpoint.
211  *
212  * %-EINVAL - invalid checkpoint.
213  */
214 int nilfs_cpfile_get_checkpoint(struct inode *cpfile,
215                                 __u64 cno,
216                                 int create,
217                                 struct nilfs_checkpoint **cpp,
218                                 struct buffer_head **bhp)
219 {
220         struct buffer_head *header_bh, *cp_bh;
221         struct nilfs_cpfile_header *header;
222         struct nilfs_checkpoint *cp;
223         void *kaddr;
224         int ret;
225 
226         if (unlikely(cno < 1 || cno > nilfs_mdt_cno(cpfile) ||
227                      (cno < nilfs_mdt_cno(cpfile) && create)))
228                 return -EINVAL;
229 
230         down_write(&NILFS_MDT(cpfile)->mi_sem);
231 
232         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
233         if (ret < 0)
234                 goto out_sem;
235         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, create, &cp_bh);
236         if (ret < 0)
237                 goto out_header;
238         kaddr = kmap(cp_bh->b_page);
239         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
240         if (nilfs_checkpoint_invalid(cp)) {
241                 if (!create) {
242                         kunmap(cp_bh->b_page);
243                         brelse(cp_bh);
244                         ret = -ENOENT;
245                         goto out_header;
246                 }
247                 /* a newly-created checkpoint */
248                 nilfs_checkpoint_clear_invalid(cp);
249                 if (!nilfs_cpfile_is_in_first(cpfile, cno))
250                         nilfs_cpfile_block_add_valid_checkpoints(cpfile, cp_bh,
251                                                                  kaddr, 1);
252                 mark_buffer_dirty(cp_bh);
253 
254                 kaddr = kmap_atomic(header_bh->b_page);
255                 header = nilfs_cpfile_block_get_header(cpfile, header_bh,
256                                                        kaddr);
257                 le64_add_cpu(&header->ch_ncheckpoints, 1);
258                 kunmap_atomic(kaddr);
259                 mark_buffer_dirty(header_bh);
260                 nilfs_mdt_mark_dirty(cpfile);
261         }
262 
263         if (cpp != NULL)
264                 *cpp = cp;
265         *bhp = cp_bh;
266 
267  out_header:
268         brelse(header_bh);
269 
270  out_sem:
271         up_write(&NILFS_MDT(cpfile)->mi_sem);
272         return ret;
273 }
274 
275 /**
276  * nilfs_cpfile_put_checkpoint - put a checkpoint
277  * @cpfile: inode of checkpoint file
278  * @cno: checkpoint number
279  * @bh: buffer head
280  *
281  * Description: nilfs_cpfile_put_checkpoint() releases the checkpoint
282  * specified by @cno. @bh must be the buffer head which has been returned by
283  * a previous call to nilfs_cpfile_get_checkpoint() with @cno.
284  */
285 void nilfs_cpfile_put_checkpoint(struct inode *cpfile, __u64 cno,
286                                  struct buffer_head *bh)
287 {
288         kunmap(bh->b_page);
289         brelse(bh);
290 }
291 
292 /**
293  * nilfs_cpfile_delete_checkpoints - delete checkpoints
294  * @cpfile: inode of checkpoint file
295  * @start: start checkpoint number
296  * @end: end checkpoint numer
297  *
298  * Description: nilfs_cpfile_delete_checkpoints() deletes the checkpoints in
299  * the period from @start to @end, excluding @end itself. The checkpoints
300  * which have been already deleted are ignored.
301  *
302  * Return Value: On success, 0 is returned. On error, one of the following
303  * negative error codes is returned.
304  *
305  * %-EIO - I/O error.
306  *
307  * %-ENOMEM - Insufficient amount of memory available.
308  *
309  * %-EINVAL - invalid checkpoints.
310  */
311 int nilfs_cpfile_delete_checkpoints(struct inode *cpfile,
312                                     __u64 start,
313                                     __u64 end)
314 {
315         struct buffer_head *header_bh, *cp_bh;
316         struct nilfs_cpfile_header *header;
317         struct nilfs_checkpoint *cp;
318         size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
319         __u64 cno;
320         void *kaddr;
321         unsigned long tnicps;
322         int ret, ncps, nicps, nss, count, i;
323 
324         if (unlikely(start == 0 || start > end)) {
325                 nilfs_msg(cpfile->i_sb, KERN_ERR,
326                           "cannot delete checkpoints: invalid range [%llu, %llu)",
327                           (unsigned long long)start, (unsigned long long)end);
328                 return -EINVAL;
329         }
330 
331         down_write(&NILFS_MDT(cpfile)->mi_sem);
332 
333         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
334         if (ret < 0)
335                 goto out_sem;
336         tnicps = 0;
337         nss = 0;
338 
339         for (cno = start; cno < end; cno += ncps) {
340                 ncps = nilfs_cpfile_checkpoints_in_block(cpfile, cno, end);
341                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
342                 if (ret < 0) {
343                         if (ret != -ENOENT)
344                                 break;
345                         /* skip hole */
346                         ret = 0;
347                         continue;
348                 }
349 
350                 kaddr = kmap_atomic(cp_bh->b_page);
351                 cp = nilfs_cpfile_block_get_checkpoint(
352                         cpfile, cno, cp_bh, kaddr);
353                 nicps = 0;
354                 for (i = 0; i < ncps; i++, cp = (void *)cp + cpsz) {
355                         if (nilfs_checkpoint_snapshot(cp)) {
356                                 nss++;
357                         } else if (!nilfs_checkpoint_invalid(cp)) {
358                                 nilfs_checkpoint_set_invalid(cp);
359                                 nicps++;
360                         }
361                 }
362                 if (nicps > 0) {
363                         tnicps += nicps;
364                         mark_buffer_dirty(cp_bh);
365                         nilfs_mdt_mark_dirty(cpfile);
366                         if (!nilfs_cpfile_is_in_first(cpfile, cno)) {
367                                 count =
368                                   nilfs_cpfile_block_sub_valid_checkpoints(
369                                                 cpfile, cp_bh, kaddr, nicps);
370                                 if (count == 0) {
371                                         /* make hole */
372                                         kunmap_atomic(kaddr);
373                                         brelse(cp_bh);
374                                         ret =
375                                           nilfs_cpfile_delete_checkpoint_block(
376                                                                    cpfile, cno);
377                                         if (ret == 0)
378                                                 continue;
379                                         nilfs_msg(cpfile->i_sb, KERN_ERR,
380                                                   "error %d deleting checkpoint block",
381                                                   ret);
382                                         break;
383                                 }
384                         }
385                 }
386 
387                 kunmap_atomic(kaddr);
388                 brelse(cp_bh);
389         }
390 
391         if (tnicps > 0) {
392                 kaddr = kmap_atomic(header_bh->b_page);
393                 header = nilfs_cpfile_block_get_header(cpfile, header_bh,
394                                                        kaddr);
395                 le64_add_cpu(&header->ch_ncheckpoints, -(u64)tnicps);
396                 mark_buffer_dirty(header_bh);
397                 nilfs_mdt_mark_dirty(cpfile);
398                 kunmap_atomic(kaddr);
399         }
400 
401         brelse(header_bh);
402         if (nss > 0)
403                 ret = -EBUSY;
404 
405  out_sem:
406         up_write(&NILFS_MDT(cpfile)->mi_sem);
407         return ret;
408 }
409 
410 static void nilfs_cpfile_checkpoint_to_cpinfo(struct inode *cpfile,
411                                               struct nilfs_checkpoint *cp,
412                                               struct nilfs_cpinfo *ci)
413 {
414         ci->ci_flags = le32_to_cpu(cp->cp_flags);
415         ci->ci_cno = le64_to_cpu(cp->cp_cno);
416         ci->ci_create = le64_to_cpu(cp->cp_create);
417         ci->ci_nblk_inc = le64_to_cpu(cp->cp_nblk_inc);
418         ci->ci_inodes_count = le64_to_cpu(cp->cp_inodes_count);
419         ci->ci_blocks_count = le64_to_cpu(cp->cp_blocks_count);
420         ci->ci_next = le64_to_cpu(cp->cp_snapshot_list.ssl_next);
421 }
422 
423 static ssize_t nilfs_cpfile_do_get_cpinfo(struct inode *cpfile, __u64 *cnop,
424                                           void *buf, unsigned int cisz,
425                                           size_t nci)
426 {
427         struct nilfs_checkpoint *cp;
428         struct nilfs_cpinfo *ci = buf;
429         struct buffer_head *bh;
430         size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
431         __u64 cur_cno = nilfs_mdt_cno(cpfile), cno = *cnop;
432         void *kaddr;
433         int n, ret;
434         int ncps, i;
435 
436         if (cno == 0)
437                 return -ENOENT; /* checkpoint number 0 is invalid */
438         down_read(&NILFS_MDT(cpfile)->mi_sem);
439 
440         for (n = 0; n < nci; cno += ncps) {
441                 ret = nilfs_cpfile_find_checkpoint_block(
442                         cpfile, cno, cur_cno - 1, &cno, &bh);
443                 if (ret < 0) {
444                         if (likely(ret == -ENOENT))
445                                 break;
446                         goto out;
447                 }
448                 ncps = nilfs_cpfile_checkpoints_in_block(cpfile, cno, cur_cno);
449 
450                 kaddr = kmap_atomic(bh->b_page);
451                 cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
452                 for (i = 0; i < ncps && n < nci; i++, cp = (void *)cp + cpsz) {
453                         if (!nilfs_checkpoint_invalid(cp)) {
454                                 nilfs_cpfile_checkpoint_to_cpinfo(cpfile, cp,
455                                                                   ci);
456                                 ci = (void *)ci + cisz;
457                                 n++;
458                         }
459                 }
460                 kunmap_atomic(kaddr);
461                 brelse(bh);
462         }
463 
464         ret = n;
465         if (n > 0) {
466                 ci = (void *)ci - cisz;
467                 *cnop = ci->ci_cno + 1;
468         }
469 
470  out:
471         up_read(&NILFS_MDT(cpfile)->mi_sem);
472         return ret;
473 }
474 
475 static ssize_t nilfs_cpfile_do_get_ssinfo(struct inode *cpfile, __u64 *cnop,
476                                           void *buf, unsigned int cisz,
477                                           size_t nci)
478 {
479         struct buffer_head *bh;
480         struct nilfs_cpfile_header *header;
481         struct nilfs_checkpoint *cp;
482         struct nilfs_cpinfo *ci = buf;
483         __u64 curr = *cnop, next;
484         unsigned long curr_blkoff, next_blkoff;
485         void *kaddr;
486         int n = 0, ret;
487 
488         down_read(&NILFS_MDT(cpfile)->mi_sem);
489 
490         if (curr == 0) {
491                 ret = nilfs_cpfile_get_header_block(cpfile, &bh);
492                 if (ret < 0)
493                         goto out;
494                 kaddr = kmap_atomic(bh->b_page);
495                 header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
496                 curr = le64_to_cpu(header->ch_snapshot_list.ssl_next);
497                 kunmap_atomic(kaddr);
498                 brelse(bh);
499                 if (curr == 0) {
500                         ret = 0;
501                         goto out;
502                 }
503         } else if (unlikely(curr == ~(__u64)0)) {
504                 ret = 0;
505                 goto out;
506         }
507 
508         curr_blkoff = nilfs_cpfile_get_blkoff(cpfile, curr);
509         ret = nilfs_cpfile_get_checkpoint_block(cpfile, curr, 0, &bh);
510         if (unlikely(ret < 0)) {
511                 if (ret == -ENOENT)
512                         ret = 0; /* No snapshots (started from a hole block) */
513                 goto out;
514         }
515         kaddr = kmap_atomic(bh->b_page);
516         while (n < nci) {
517                 cp = nilfs_cpfile_block_get_checkpoint(cpfile, curr, bh, kaddr);
518                 curr = ~(__u64)0; /* Terminator */
519                 if (unlikely(nilfs_checkpoint_invalid(cp) ||
520                              !nilfs_checkpoint_snapshot(cp)))
521                         break;
522                 nilfs_cpfile_checkpoint_to_cpinfo(cpfile, cp, ci);
523                 ci = (void *)ci + cisz;
524                 n++;
525                 next = le64_to_cpu(cp->cp_snapshot_list.ssl_next);
526                 if (next == 0)
527                         break; /* reach end of the snapshot list */
528 
529                 next_blkoff = nilfs_cpfile_get_blkoff(cpfile, next);
530                 if (curr_blkoff != next_blkoff) {
531                         kunmap_atomic(kaddr);
532                         brelse(bh);
533                         ret = nilfs_cpfile_get_checkpoint_block(cpfile, next,
534                                                                 0, &bh);
535                         if (unlikely(ret < 0)) {
536                                 WARN_ON(ret == -ENOENT);
537                                 goto out;
538                         }
539                         kaddr = kmap_atomic(bh->b_page);
540                 }
541                 curr = next;
542                 curr_blkoff = next_blkoff;
543         }
544         kunmap_atomic(kaddr);
545         brelse(bh);
546         *cnop = curr;
547         ret = n;
548 
549  out:
550         up_read(&NILFS_MDT(cpfile)->mi_sem);
551         return ret;
552 }
553 
554 /**
555  * nilfs_cpfile_get_cpinfo -
556  * @cpfile:
557  * @cno:
558  * @ci:
559  * @nci:
560  */
561 
562 ssize_t nilfs_cpfile_get_cpinfo(struct inode *cpfile, __u64 *cnop, int mode,
563                                 void *buf, unsigned int cisz, size_t nci)
564 {
565         switch (mode) {
566         case NILFS_CHECKPOINT:
567                 return nilfs_cpfile_do_get_cpinfo(cpfile, cnop, buf, cisz, nci);
568         case NILFS_SNAPSHOT:
569                 return nilfs_cpfile_do_get_ssinfo(cpfile, cnop, buf, cisz, nci);
570         default:
571                 return -EINVAL;
572         }
573 }
574 
575 /**
576  * nilfs_cpfile_delete_checkpoint -
577  * @cpfile:
578  * @cno:
579  */
580 int nilfs_cpfile_delete_checkpoint(struct inode *cpfile, __u64 cno)
581 {
582         struct nilfs_cpinfo ci;
583         __u64 tcno = cno;
584         ssize_t nci;
585 
586         nci = nilfs_cpfile_do_get_cpinfo(cpfile, &tcno, &ci, sizeof(ci), 1);
587         if (nci < 0)
588                 return nci;
589         else if (nci == 0 || ci.ci_cno != cno)
590                 return -ENOENT;
591         else if (nilfs_cpinfo_snapshot(&ci))
592                 return -EBUSY;
593 
594         return nilfs_cpfile_delete_checkpoints(cpfile, cno, cno + 1);
595 }
596 
597 static struct nilfs_snapshot_list *
598 nilfs_cpfile_block_get_snapshot_list(const struct inode *cpfile,
599                                      __u64 cno,
600                                      struct buffer_head *bh,
601                                      void *kaddr)
602 {
603         struct nilfs_cpfile_header *header;
604         struct nilfs_checkpoint *cp;
605         struct nilfs_snapshot_list *list;
606 
607         if (cno != 0) {
608                 cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
609                 list = &cp->cp_snapshot_list;
610         } else {
611                 header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
612                 list = &header->ch_snapshot_list;
613         }
614         return list;
615 }
616 
617 static int nilfs_cpfile_set_snapshot(struct inode *cpfile, __u64 cno)
618 {
619         struct buffer_head *header_bh, *curr_bh, *prev_bh, *cp_bh;
620         struct nilfs_cpfile_header *header;
621         struct nilfs_checkpoint *cp;
622         struct nilfs_snapshot_list *list;
623         __u64 curr, prev;
624         unsigned long curr_blkoff, prev_blkoff;
625         void *kaddr;
626         int ret;
627 
628         if (cno == 0)
629                 return -ENOENT; /* checkpoint number 0 is invalid */
630         down_write(&NILFS_MDT(cpfile)->mi_sem);
631 
632         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
633         if (ret < 0)
634                 goto out_sem;
635         kaddr = kmap_atomic(cp_bh->b_page);
636         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
637         if (nilfs_checkpoint_invalid(cp)) {
638                 ret = -ENOENT;
639                 kunmap_atomic(kaddr);
640                 goto out_cp;
641         }
642         if (nilfs_checkpoint_snapshot(cp)) {
643                 ret = 0;
644                 kunmap_atomic(kaddr);
645                 goto out_cp;
646         }
647         kunmap_atomic(kaddr);
648 
649         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
650         if (ret < 0)
651                 goto out_cp;
652         kaddr = kmap_atomic(header_bh->b_page);
653         header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
654         list = &header->ch_snapshot_list;
655         curr_bh = header_bh;
656         get_bh(curr_bh);
657         curr = 0;
658         curr_blkoff = 0;
659         prev = le64_to_cpu(list->ssl_prev);
660         while (prev > cno) {
661                 prev_blkoff = nilfs_cpfile_get_blkoff(cpfile, prev);
662                 curr = prev;
663                 if (curr_blkoff != prev_blkoff) {
664                         kunmap_atomic(kaddr);
665                         brelse(curr_bh);
666                         ret = nilfs_cpfile_get_checkpoint_block(cpfile, curr,
667                                                                 0, &curr_bh);
668                         if (ret < 0)
669                                 goto out_header;
670                         kaddr = kmap_atomic(curr_bh->b_page);
671                 }
672                 curr_blkoff = prev_blkoff;
673                 cp = nilfs_cpfile_block_get_checkpoint(
674                         cpfile, curr, curr_bh, kaddr);
675                 list = &cp->cp_snapshot_list;
676                 prev = le64_to_cpu(list->ssl_prev);
677         }
678         kunmap_atomic(kaddr);
679 
680         if (prev != 0) {
681                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, prev, 0,
682                                                         &prev_bh);
683                 if (ret < 0)
684                         goto out_curr;
685         } else {
686                 prev_bh = header_bh;
687                 get_bh(prev_bh);
688         }
689 
690         kaddr = kmap_atomic(curr_bh->b_page);
691         list = nilfs_cpfile_block_get_snapshot_list(
692                 cpfile, curr, curr_bh, kaddr);
693         list->ssl_prev = cpu_to_le64(cno);
694         kunmap_atomic(kaddr);
695 
696         kaddr = kmap_atomic(cp_bh->b_page);
697         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
698         cp->cp_snapshot_list.ssl_next = cpu_to_le64(curr);
699         cp->cp_snapshot_list.ssl_prev = cpu_to_le64(prev);
700         nilfs_checkpoint_set_snapshot(cp);
701         kunmap_atomic(kaddr);
702 
703         kaddr = kmap_atomic(prev_bh->b_page);
704         list = nilfs_cpfile_block_get_snapshot_list(
705                 cpfile, prev, prev_bh, kaddr);
706         list->ssl_next = cpu_to_le64(cno);
707         kunmap_atomic(kaddr);
708 
709         kaddr = kmap_atomic(header_bh->b_page);
710         header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
711         le64_add_cpu(&header->ch_nsnapshots, 1);
712         kunmap_atomic(kaddr);
713 
714         mark_buffer_dirty(prev_bh);
715         mark_buffer_dirty(curr_bh);
716         mark_buffer_dirty(cp_bh);
717         mark_buffer_dirty(header_bh);
718         nilfs_mdt_mark_dirty(cpfile);
719 
720         brelse(prev_bh);
721 
722  out_curr:
723         brelse(curr_bh);
724 
725  out_header:
726         brelse(header_bh);
727 
728  out_cp:
729         brelse(cp_bh);
730 
731  out_sem:
732         up_write(&NILFS_MDT(cpfile)->mi_sem);
733         return ret;
734 }
735 
736 static int nilfs_cpfile_clear_snapshot(struct inode *cpfile, __u64 cno)
737 {
738         struct buffer_head *header_bh, *next_bh, *prev_bh, *cp_bh;
739         struct nilfs_cpfile_header *header;
740         struct nilfs_checkpoint *cp;
741         struct nilfs_snapshot_list *list;
742         __u64 next, prev;
743         void *kaddr;
744         int ret;
745 
746         if (cno == 0)
747                 return -ENOENT; /* checkpoint number 0 is invalid */
748         down_write(&NILFS_MDT(cpfile)->mi_sem);
749 
750         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
751         if (ret < 0)
752                 goto out_sem;
753         kaddr = kmap_atomic(cp_bh->b_page);
754         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
755         if (nilfs_checkpoint_invalid(cp)) {
756                 ret = -ENOENT;
757                 kunmap_atomic(kaddr);
758                 goto out_cp;
759         }
760         if (!nilfs_checkpoint_snapshot(cp)) {
761                 ret = 0;
762                 kunmap_atomic(kaddr);
763                 goto out_cp;
764         }
765 
766         list = &cp->cp_snapshot_list;
767         next = le64_to_cpu(list->ssl_next);
768         prev = le64_to_cpu(list->ssl_prev);
769         kunmap_atomic(kaddr);
770 
771         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
772         if (ret < 0)
773                 goto out_cp;
774         if (next != 0) {
775                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, next, 0,
776                                                         &next_bh);
777                 if (ret < 0)
778                         goto out_header;
779         } else {
780                 next_bh = header_bh;
781                 get_bh(next_bh);
782         }
783         if (prev != 0) {
784                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, prev, 0,
785                                                         &prev_bh);
786                 if (ret < 0)
787                         goto out_next;
788         } else {
789                 prev_bh = header_bh;
790                 get_bh(prev_bh);
791         }
792 
793         kaddr = kmap_atomic(next_bh->b_page);
794         list = nilfs_cpfile_block_get_snapshot_list(
795                 cpfile, next, next_bh, kaddr);
796         list->ssl_prev = cpu_to_le64(prev);
797         kunmap_atomic(kaddr);
798 
799         kaddr = kmap_atomic(prev_bh->b_page);
800         list = nilfs_cpfile_block_get_snapshot_list(
801                 cpfile, prev, prev_bh, kaddr);
802         list->ssl_next = cpu_to_le64(next);
803         kunmap_atomic(kaddr);
804 
805         kaddr = kmap_atomic(cp_bh->b_page);
806         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
807         cp->cp_snapshot_list.ssl_next = cpu_to_le64(0);
808         cp->cp_snapshot_list.ssl_prev = cpu_to_le64(0);
809         nilfs_checkpoint_clear_snapshot(cp);
810         kunmap_atomic(kaddr);
811 
812         kaddr = kmap_atomic(header_bh->b_page);
813         header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
814         le64_add_cpu(&header->ch_nsnapshots, -1);
815         kunmap_atomic(kaddr);
816 
817         mark_buffer_dirty(next_bh);
818         mark_buffer_dirty(prev_bh);
819         mark_buffer_dirty(cp_bh);
820         mark_buffer_dirty(header_bh);
821         nilfs_mdt_mark_dirty(cpfile);
822 
823         brelse(prev_bh);
824 
825  out_next:
826         brelse(next_bh);
827 
828  out_header:
829         brelse(header_bh);
830 
831  out_cp:
832         brelse(cp_bh);
833 
834  out_sem:
835         up_write(&NILFS_MDT(cpfile)->mi_sem);
836         return ret;
837 }
838 
839 /**
840  * nilfs_cpfile_is_snapshot -
841  * @cpfile: inode of checkpoint file
842  * @cno: checkpoint number
843  *
844  * Description:
845  *
846  * Return Value: On success, 1 is returned if the checkpoint specified by
847  * @cno is a snapshot, or 0 if not. On error, one of the following negative
848  * error codes is returned.
849  *
850  * %-EIO - I/O error.
851  *
852  * %-ENOMEM - Insufficient amount of memory available.
853  *
854  * %-ENOENT - No such checkpoint.
855  */
856 int nilfs_cpfile_is_snapshot(struct inode *cpfile, __u64 cno)
857 {
858         struct buffer_head *bh;
859         struct nilfs_checkpoint *cp;
860         void *kaddr;
861         int ret;
862 
863         /*
864          * CP number is invalid if it's zero or larger than the
865          * largest existing one.
866          */
867         if (cno == 0 || cno >= nilfs_mdt_cno(cpfile))
868                 return -ENOENT;
869         down_read(&NILFS_MDT(cpfile)->mi_sem);
870 
871         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &bh);
872         if (ret < 0)
873                 goto out;
874         kaddr = kmap_atomic(bh->b_page);
875         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
876         if (nilfs_checkpoint_invalid(cp))
877                 ret = -ENOENT;
878         else
879                 ret = nilfs_checkpoint_snapshot(cp);
880         kunmap_atomic(kaddr);
881         brelse(bh);
882 
883  out:
884         up_read(&NILFS_MDT(cpfile)->mi_sem);
885         return ret;
886 }
887 
888 /**
889  * nilfs_cpfile_change_cpmode - change checkpoint mode
890  * @cpfile: inode of checkpoint file
891  * @cno: checkpoint number
892  * @status: mode of checkpoint
893  *
894  * Description: nilfs_change_cpmode() changes the mode of the checkpoint
895  * specified by @cno. The mode @mode is NILFS_CHECKPOINT or NILFS_SNAPSHOT.
896  *
897  * Return Value: On success, 0 is returned. On error, one of the following
898  * negative error codes is returned.
899  *
900  * %-EIO - I/O error.
901  *
902  * %-ENOMEM - Insufficient amount of memory available.
903  *
904  * %-ENOENT - No such checkpoint.
905  */
906 int nilfs_cpfile_change_cpmode(struct inode *cpfile, __u64 cno, int mode)
907 {
908         int ret;
909 
910         switch (mode) {
911         case NILFS_CHECKPOINT:
912                 if (nilfs_checkpoint_is_mounted(cpfile->i_sb, cno))
913                         /*
914                          * Current implementation does not have to protect
915                          * plain read-only mounts since they are exclusive
916                          * with a read/write mount and are protected from the
917                          * cleaner.
918                          */
919                         ret = -EBUSY;
920                 else
921                         ret = nilfs_cpfile_clear_snapshot(cpfile, cno);
922                 return ret;
923         case NILFS_SNAPSHOT:
924                 return nilfs_cpfile_set_snapshot(cpfile, cno);
925         default:
926                 return -EINVAL;
927         }
928 }
929 
930 /**
931  * nilfs_cpfile_get_stat - get checkpoint statistics
932  * @cpfile: inode of checkpoint file
933  * @stat: pointer to a structure of checkpoint statistics
934  *
935  * Description: nilfs_cpfile_get_stat() returns information about checkpoints.
936  *
937  * Return Value: On success, 0 is returned, and checkpoints information is
938  * stored in the place pointed by @stat. On error, one of the following
939  * negative error codes is returned.
940  *
941  * %-EIO - I/O error.
942  *
943  * %-ENOMEM - Insufficient amount of memory available.
944  */
945 int nilfs_cpfile_get_stat(struct inode *cpfile, struct nilfs_cpstat *cpstat)
946 {
947         struct buffer_head *bh;
948         struct nilfs_cpfile_header *header;
949         void *kaddr;
950         int ret;
951 
952         down_read(&NILFS_MDT(cpfile)->mi_sem);
953 
954         ret = nilfs_cpfile_get_header_block(cpfile, &bh);
955         if (ret < 0)
956                 goto out_sem;
957         kaddr = kmap_atomic(bh->b_page);
958         header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
959         cpstat->cs_cno = nilfs_mdt_cno(cpfile);
960         cpstat->cs_ncps = le64_to_cpu(header->ch_ncheckpoints);
961         cpstat->cs_nsss = le64_to_cpu(header->ch_nsnapshots);
962         kunmap_atomic(kaddr);
963         brelse(bh);
964 
965  out_sem:
966         up_read(&NILFS_MDT(cpfile)->mi_sem);
967         return ret;
968 }
969 
970 /**
971  * nilfs_cpfile_read - read or get cpfile inode
972  * @sb: super block instance
973  * @cpsize: size of a checkpoint entry
974  * @raw_inode: on-disk cpfile inode
975  * @inodep: buffer to store the inode
976  */
977 int nilfs_cpfile_read(struct super_block *sb, size_t cpsize,
978                       struct nilfs_inode *raw_inode, struct inode **inodep)
979 {
980         struct inode *cpfile;
981         int err;
982 
983         if (cpsize > sb->s_blocksize) {
984                 nilfs_msg(sb, KERN_ERR,
985                           "too large checkpoint size: %zu bytes", cpsize);
986                 return -EINVAL;
987         } else if (cpsize < NILFS_MIN_CHECKPOINT_SIZE) {
988                 nilfs_msg(sb, KERN_ERR,
989                           "too small checkpoint size: %zu bytes", cpsize);
990                 return -EINVAL;
991         }
992 
993         cpfile = nilfs_iget_locked(sb, NULL, NILFS_CPFILE_INO);
994         if (unlikely(!cpfile))
995                 return -ENOMEM;
996         if (!(cpfile->i_state & I_NEW))
997                 goto out;
998 
999         err = nilfs_mdt_init(cpfile, NILFS_MDT_GFP, 0);
1000         if (err)
1001                 goto failed;
1002 
1003         nilfs_mdt_set_entry_size(cpfile, cpsize,
1004                                  sizeof(struct nilfs_cpfile_header));
1005 
1006         err = nilfs_read_inode_common(cpfile, raw_inode);
1007         if (err)
1008                 goto failed;
1009 
1010         unlock_new_inode(cpfile);
1011  out:
1012         *inodep = cpfile;
1013         return 0;
1014  failed:
1015         iget_failed(cpfile);
1016         return err;
1017 }
1018 

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