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TOMOYO Linux Cross Reference
Linux/fs/ubifs/recovery.c

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  1 /*
  2  * This file is part of UBIFS.
  3  *
  4  * Copyright (C) 2006-2008 Nokia Corporation
  5  *
  6  * This program is free software; you can redistribute it and/or modify it
  7  * under the terms of the GNU General Public License version 2 as published by
  8  * the Free Software Foundation.
  9  *
 10  * This program is distributed in the hope that it will be useful, but WITHOUT
 11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 13  * more details.
 14  *
 15  * You should have received a copy of the GNU General Public License along with
 16  * this program; if not, write to the Free Software Foundation, Inc., 51
 17  * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 18  *
 19  * Authors: Adrian Hunter
 20  *          Artem Bityutskiy (Битюцкий Артём)
 21  */
 22 
 23 /*
 24  * This file implements functions needed to recover from unclean un-mounts.
 25  * When UBIFS is mounted, it checks a flag on the master node to determine if
 26  * an un-mount was completed successfully. If not, the process of mounting
 27  * incorporates additional checking and fixing of on-flash data structures.
 28  * UBIFS always cleans away all remnants of an unclean un-mount, so that
 29  * errors do not accumulate. However UBIFS defers recovery if it is mounted
 30  * read-only, and the flash is not modified in that case.
 31  *
 32  * The general UBIFS approach to the recovery is that it recovers from
 33  * corruptions which could be caused by power cuts, but it refuses to recover
 34  * from corruption caused by other reasons. And UBIFS tries to distinguish
 35  * between these 2 reasons of corruptions and silently recover in the former
 36  * case and loudly complain in the latter case.
 37  *
 38  * UBIFS writes only to erased LEBs, so it writes only to the flash space
 39  * containing only 0xFFs. UBIFS also always writes strictly from the beginning
 40  * of the LEB to the end. And UBIFS assumes that the underlying flash media
 41  * writes in @c->max_write_size bytes at a time.
 42  *
 43  * Hence, if UBIFS finds a corrupted node at offset X, it expects only the min.
 44  * I/O unit corresponding to offset X to contain corrupted data, all the
 45  * following min. I/O units have to contain empty space (all 0xFFs). If this is
 46  * not true, the corruption cannot be the result of a power cut, and UBIFS
 47  * refuses to mount.
 48  */
 49 
 50 #include <linux/crc32.h>
 51 #include <linux/slab.h>
 52 #include "ubifs.h"
 53 
 54 /**
 55  * is_empty - determine whether a buffer is empty (contains all 0xff).
 56  * @buf: buffer to clean
 57  * @len: length of buffer
 58  *
 59  * This function returns %1 if the buffer is empty (contains all 0xff) otherwise
 60  * %0 is returned.
 61  */
 62 static int is_empty(void *buf, int len)
 63 {
 64         uint8_t *p = buf;
 65         int i;
 66 
 67         for (i = 0; i < len; i++)
 68                 if (*p++ != 0xff)
 69                         return 0;
 70         return 1;
 71 }
 72 
 73 /**
 74  * first_non_ff - find offset of the first non-0xff byte.
 75  * @buf: buffer to search in
 76  * @len: length of buffer
 77  *
 78  * This function returns offset of the first non-0xff byte in @buf or %-1 if
 79  * the buffer contains only 0xff bytes.
 80  */
 81 static int first_non_ff(void *buf, int len)
 82 {
 83         uint8_t *p = buf;
 84         int i;
 85 
 86         for (i = 0; i < len; i++)
 87                 if (*p++ != 0xff)
 88                         return i;
 89         return -1;
 90 }
 91 
 92 /**
 93  * get_master_node - get the last valid master node allowing for corruption.
 94  * @c: UBIFS file-system description object
 95  * @lnum: LEB number
 96  * @pbuf: buffer containing the LEB read, is returned here
 97  * @mst: master node, if found, is returned here
 98  * @cor: corruption, if found, is returned here
 99  *
100  * This function allocates a buffer, reads the LEB into it, and finds and
101  * returns the last valid master node allowing for one area of corruption.
102  * The corrupt area, if there is one, must be consistent with the assumption
103  * that it is the result of an unclean unmount while the master node was being
104  * written. Under those circumstances, it is valid to use the previously written
105  * master node.
106  *
107  * This function returns %0 on success and a negative error code on failure.
108  */
109 static int get_master_node(const struct ubifs_info *c, int lnum, void **pbuf,
110                            struct ubifs_mst_node **mst, void **cor)
111 {
112         const int sz = c->mst_node_alsz;
113         int err, offs, len;
114         void *sbuf, *buf;
115 
116         sbuf = vmalloc(c->leb_size);
117         if (!sbuf)
118                 return -ENOMEM;
119 
120         err = ubifs_leb_read(c, lnum, sbuf, 0, c->leb_size, 0);
121         if (err && err != -EBADMSG)
122                 goto out_free;
123 
124         /* Find the first position that is definitely not a node */
125         offs = 0;
126         buf = sbuf;
127         len = c->leb_size;
128         while (offs + UBIFS_MST_NODE_SZ <= c->leb_size) {
129                 struct ubifs_ch *ch = buf;
130 
131                 if (le32_to_cpu(ch->magic) != UBIFS_NODE_MAGIC)
132                         break;
133                 offs += sz;
134                 buf  += sz;
135                 len  -= sz;
136         }
137         /* See if there was a valid master node before that */
138         if (offs) {
139                 int ret;
140 
141                 offs -= sz;
142                 buf  -= sz;
143                 len  += sz;
144                 ret = ubifs_scan_a_node(c, buf, len, lnum, offs, 1);
145                 if (ret != SCANNED_A_NODE && offs) {
146                         /* Could have been corruption so check one place back */
147                         offs -= sz;
148                         buf  -= sz;
149                         len  += sz;
150                         ret = ubifs_scan_a_node(c, buf, len, lnum, offs, 1);
151                         if (ret != SCANNED_A_NODE)
152                                 /*
153                                  * We accept only one area of corruption because
154                                  * we are assuming that it was caused while
155                                  * trying to write a master node.
156                                  */
157                                 goto out_err;
158                 }
159                 if (ret == SCANNED_A_NODE) {
160                         struct ubifs_ch *ch = buf;
161 
162                         if (ch->node_type != UBIFS_MST_NODE)
163                                 goto out_err;
164                         dbg_rcvry("found a master node at %d:%d", lnum, offs);
165                         *mst = buf;
166                         offs += sz;
167                         buf  += sz;
168                         len  -= sz;
169                 }
170         }
171         /* Check for corruption */
172         if (offs < c->leb_size) {
173                 if (!is_empty(buf, min_t(int, len, sz))) {
174                         *cor = buf;
175                         dbg_rcvry("found corruption at %d:%d", lnum, offs);
176                 }
177                 offs += sz;
178                 buf  += sz;
179                 len  -= sz;
180         }
181         /* Check remaining empty space */
182         if (offs < c->leb_size)
183                 if (!is_empty(buf, len))
184                         goto out_err;
185         *pbuf = sbuf;
186         return 0;
187 
188 out_err:
189         err = -EINVAL;
190 out_free:
191         vfree(sbuf);
192         *mst = NULL;
193         *cor = NULL;
194         return err;
195 }
196 
197 /**
198  * write_rcvrd_mst_node - write recovered master node.
199  * @c: UBIFS file-system description object
200  * @mst: master node
201  *
202  * This function returns %0 on success and a negative error code on failure.
203  */
204 static int write_rcvrd_mst_node(struct ubifs_info *c,
205                                 struct ubifs_mst_node *mst)
206 {
207         int err = 0, lnum = UBIFS_MST_LNUM, sz = c->mst_node_alsz;
208         __le32 save_flags;
209 
210         dbg_rcvry("recovery");
211 
212         save_flags = mst->flags;
213         mst->flags |= cpu_to_le32(UBIFS_MST_RCVRY);
214 
215         ubifs_prepare_node(c, mst, UBIFS_MST_NODE_SZ, 1);
216         err = ubifs_leb_change(c, lnum, mst, sz);
217         if (err)
218                 goto out;
219         err = ubifs_leb_change(c, lnum + 1, mst, sz);
220         if (err)
221                 goto out;
222 out:
223         mst->flags = save_flags;
224         return err;
225 }
226 
227 /**
228  * ubifs_recover_master_node - recover the master node.
229  * @c: UBIFS file-system description object
230  *
231  * This function recovers the master node from corruption that may occur due to
232  * an unclean unmount.
233  *
234  * This function returns %0 on success and a negative error code on failure.
235  */
236 int ubifs_recover_master_node(struct ubifs_info *c)
237 {
238         void *buf1 = NULL, *buf2 = NULL, *cor1 = NULL, *cor2 = NULL;
239         struct ubifs_mst_node *mst1 = NULL, *mst2 = NULL, *mst;
240         const int sz = c->mst_node_alsz;
241         int err, offs1, offs2;
242 
243         dbg_rcvry("recovery");
244 
245         err = get_master_node(c, UBIFS_MST_LNUM, &buf1, &mst1, &cor1);
246         if (err)
247                 goto out_free;
248 
249         err = get_master_node(c, UBIFS_MST_LNUM + 1, &buf2, &mst2, &cor2);
250         if (err)
251                 goto out_free;
252 
253         if (mst1) {
254                 offs1 = (void *)mst1 - buf1;
255                 if ((le32_to_cpu(mst1->flags) & UBIFS_MST_RCVRY) &&
256                     (offs1 == 0 && !cor1)) {
257                         /*
258                          * mst1 was written by recovery at offset 0 with no
259                          * corruption.
260                          */
261                         dbg_rcvry("recovery recovery");
262                         mst = mst1;
263                 } else if (mst2) {
264                         offs2 = (void *)mst2 - buf2;
265                         if (offs1 == offs2) {
266                                 /* Same offset, so must be the same */
267                                 if (memcmp((void *)mst1 + UBIFS_CH_SZ,
268                                            (void *)mst2 + UBIFS_CH_SZ,
269                                            UBIFS_MST_NODE_SZ - UBIFS_CH_SZ))
270                                         goto out_err;
271                                 mst = mst1;
272                         } else if (offs2 + sz == offs1) {
273                                 /* 1st LEB was written, 2nd was not */
274                                 if (cor1)
275                                         goto out_err;
276                                 mst = mst1;
277                         } else if (offs1 == 0 &&
278                                    c->leb_size - offs2 - sz < sz) {
279                                 /* 1st LEB was unmapped and written, 2nd not */
280                                 if (cor1)
281                                         goto out_err;
282                                 mst = mst1;
283                         } else
284                                 goto out_err;
285                 } else {
286                         /*
287                          * 2nd LEB was unmapped and about to be written, so
288                          * there must be only one master node in the first LEB
289                          * and no corruption.
290                          */
291                         if (offs1 != 0 || cor1)
292                                 goto out_err;
293                         mst = mst1;
294                 }
295         } else {
296                 if (!mst2)
297                         goto out_err;
298                 /*
299                  * 1st LEB was unmapped and about to be written, so there must
300                  * be no room left in 2nd LEB.
301                  */
302                 offs2 = (void *)mst2 - buf2;
303                 if (offs2 + sz + sz <= c->leb_size)
304                         goto out_err;
305                 mst = mst2;
306         }
307 
308         ubifs_msg(c, "recovered master node from LEB %d",
309                   (mst == mst1 ? UBIFS_MST_LNUM : UBIFS_MST_LNUM + 1));
310 
311         memcpy(c->mst_node, mst, UBIFS_MST_NODE_SZ);
312 
313         if (c->ro_mount) {
314                 /* Read-only mode. Keep a copy for switching to rw mode */
315                 c->rcvrd_mst_node = kmalloc(sz, GFP_KERNEL);
316                 if (!c->rcvrd_mst_node) {
317                         err = -ENOMEM;
318                         goto out_free;
319                 }
320                 memcpy(c->rcvrd_mst_node, c->mst_node, UBIFS_MST_NODE_SZ);
321 
322                 /*
323                  * We had to recover the master node, which means there was an
324                  * unclean reboot. However, it is possible that the master node
325                  * is clean at this point, i.e., %UBIFS_MST_DIRTY is not set.
326                  * E.g., consider the following chain of events:
327                  *
328                  * 1. UBIFS was cleanly unmounted, so the master node is clean
329                  * 2. UBIFS is being mounted R/W and starts changing the master
330                  *    node in the first (%UBIFS_MST_LNUM). A power cut happens,
331                  *    so this LEB ends up with some amount of garbage at the
332                  *    end.
333                  * 3. UBIFS is being mounted R/O. We reach this place and
334                  *    recover the master node from the second LEB
335                  *    (%UBIFS_MST_LNUM + 1). But we cannot update the media
336                  *    because we are being mounted R/O. We have to defer the
337                  *    operation.
338                  * 4. However, this master node (@c->mst_node) is marked as
339                  *    clean (since the step 1). And if we just return, the
340                  *    mount code will be confused and won't recover the master
341                  *    node when it is re-mounter R/W later.
342                  *
343                  *    Thus, to force the recovery by marking the master node as
344                  *    dirty.
345                  */
346                 c->mst_node->flags |= cpu_to_le32(UBIFS_MST_DIRTY);
347         } else {
348                 /* Write the recovered master node */
349                 c->max_sqnum = le64_to_cpu(mst->ch.sqnum) - 1;
350                 err = write_rcvrd_mst_node(c, c->mst_node);
351                 if (err)
352                         goto out_free;
353         }
354 
355         vfree(buf2);
356         vfree(buf1);
357 
358         return 0;
359 
360 out_err:
361         err = -EINVAL;
362 out_free:
363         ubifs_err(c, "failed to recover master node");
364         if (mst1) {
365                 ubifs_err(c, "dumping first master node");
366                 ubifs_dump_node(c, mst1);
367         }
368         if (mst2) {
369                 ubifs_err(c, "dumping second master node");
370                 ubifs_dump_node(c, mst2);
371         }
372         vfree(buf2);
373         vfree(buf1);
374         return err;
375 }
376 
377 /**
378  * ubifs_write_rcvrd_mst_node - write the recovered master node.
379  * @c: UBIFS file-system description object
380  *
381  * This function writes the master node that was recovered during mounting in
382  * read-only mode and must now be written because we are remounting rw.
383  *
384  * This function returns %0 on success and a negative error code on failure.
385  */
386 int ubifs_write_rcvrd_mst_node(struct ubifs_info *c)
387 {
388         int err;
389 
390         if (!c->rcvrd_mst_node)
391                 return 0;
392         c->rcvrd_mst_node->flags |= cpu_to_le32(UBIFS_MST_DIRTY);
393         c->mst_node->flags |= cpu_to_le32(UBIFS_MST_DIRTY);
394         err = write_rcvrd_mst_node(c, c->rcvrd_mst_node);
395         if (err)
396                 return err;
397         kfree(c->rcvrd_mst_node);
398         c->rcvrd_mst_node = NULL;
399         return 0;
400 }
401 
402 /**
403  * is_last_write - determine if an offset was in the last write to a LEB.
404  * @c: UBIFS file-system description object
405  * @buf: buffer to check
406  * @offs: offset to check
407  *
408  * This function returns %1 if @offs was in the last write to the LEB whose data
409  * is in @buf, otherwise %0 is returned. The determination is made by checking
410  * for subsequent empty space starting from the next @c->max_write_size
411  * boundary.
412  */
413 static int is_last_write(const struct ubifs_info *c, void *buf, int offs)
414 {
415         int empty_offs, check_len;
416         uint8_t *p;
417 
418         /*
419          * Round up to the next @c->max_write_size boundary i.e. @offs is in
420          * the last wbuf written. After that should be empty space.
421          */
422         empty_offs = ALIGN(offs + 1, c->max_write_size);
423         check_len = c->leb_size - empty_offs;
424         p = buf + empty_offs - offs;
425         return is_empty(p, check_len);
426 }
427 
428 /**
429  * clean_buf - clean the data from an LEB sitting in a buffer.
430  * @c: UBIFS file-system description object
431  * @buf: buffer to clean
432  * @lnum: LEB number to clean
433  * @offs: offset from which to clean
434  * @len: length of buffer
435  *
436  * This function pads up to the next min_io_size boundary (if there is one) and
437  * sets empty space to all 0xff. @buf, @offs and @len are updated to the next
438  * @c->min_io_size boundary.
439  */
440 static void clean_buf(const struct ubifs_info *c, void **buf, int lnum,
441                       int *offs, int *len)
442 {
443         int empty_offs, pad_len;
444 
445         lnum = lnum;
446         dbg_rcvry("cleaning corruption at %d:%d", lnum, *offs);
447 
448         ubifs_assert(!(*offs & 7));
449         empty_offs = ALIGN(*offs, c->min_io_size);
450         pad_len = empty_offs - *offs;
451         ubifs_pad(c, *buf, pad_len);
452         *offs += pad_len;
453         *buf += pad_len;
454         *len -= pad_len;
455         memset(*buf, 0xff, c->leb_size - empty_offs);
456 }
457 
458 /**
459  * no_more_nodes - determine if there are no more nodes in a buffer.
460  * @c: UBIFS file-system description object
461  * @buf: buffer to check
462  * @len: length of buffer
463  * @lnum: LEB number of the LEB from which @buf was read
464  * @offs: offset from which @buf was read
465  *
466  * This function ensures that the corrupted node at @offs is the last thing
467  * written to a LEB. This function returns %1 if more data is not found and
468  * %0 if more data is found.
469  */
470 static int no_more_nodes(const struct ubifs_info *c, void *buf, int len,
471                         int lnum, int offs)
472 {
473         struct ubifs_ch *ch = buf;
474         int skip, dlen = le32_to_cpu(ch->len);
475 
476         /* Check for empty space after the corrupt node's common header */
477         skip = ALIGN(offs + UBIFS_CH_SZ, c->max_write_size) - offs;
478         if (is_empty(buf + skip, len - skip))
479                 return 1;
480         /*
481          * The area after the common header size is not empty, so the common
482          * header must be intact. Check it.
483          */
484         if (ubifs_check_node(c, buf, lnum, offs, 1, 0) != -EUCLEAN) {
485                 dbg_rcvry("unexpected bad common header at %d:%d", lnum, offs);
486                 return 0;
487         }
488         /* Now we know the corrupt node's length we can skip over it */
489         skip = ALIGN(offs + dlen, c->max_write_size) - offs;
490         /* After which there should be empty space */
491         if (is_empty(buf + skip, len - skip))
492                 return 1;
493         dbg_rcvry("unexpected data at %d:%d", lnum, offs + skip);
494         return 0;
495 }
496 
497 /**
498  * fix_unclean_leb - fix an unclean LEB.
499  * @c: UBIFS file-system description object
500  * @sleb: scanned LEB information
501  * @start: offset where scan started
502  */
503 static int fix_unclean_leb(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
504                            int start)
505 {
506         int lnum = sleb->lnum, endpt = start;
507 
508         /* Get the end offset of the last node we are keeping */
509         if (!list_empty(&sleb->nodes)) {
510                 struct ubifs_scan_node *snod;
511 
512                 snod = list_entry(sleb->nodes.prev,
513                                   struct ubifs_scan_node, list);
514                 endpt = snod->offs + snod->len;
515         }
516 
517         if (c->ro_mount && !c->remounting_rw) {
518                 /* Add to recovery list */
519                 struct ubifs_unclean_leb *ucleb;
520 
521                 dbg_rcvry("need to fix LEB %d start %d endpt %d",
522                           lnum, start, sleb->endpt);
523                 ucleb = kzalloc(sizeof(struct ubifs_unclean_leb), GFP_NOFS);
524                 if (!ucleb)
525                         return -ENOMEM;
526                 ucleb->lnum = lnum;
527                 ucleb->endpt = endpt;
528                 list_add_tail(&ucleb->list, &c->unclean_leb_list);
529         } else {
530                 /* Write the fixed LEB back to flash */
531                 int err;
532 
533                 dbg_rcvry("fixing LEB %d start %d endpt %d",
534                           lnum, start, sleb->endpt);
535                 if (endpt == 0) {
536                         err = ubifs_leb_unmap(c, lnum);
537                         if (err)
538                                 return err;
539                 } else {
540                         int len = ALIGN(endpt, c->min_io_size);
541 
542                         if (start) {
543                                 err = ubifs_leb_read(c, lnum, sleb->buf, 0,
544                                                      start, 1);
545                                 if (err)
546                                         return err;
547                         }
548                         /* Pad to min_io_size */
549                         if (len > endpt) {
550                                 int pad_len = len - ALIGN(endpt, 8);
551 
552                                 if (pad_len > 0) {
553                                         void *buf = sleb->buf + len - pad_len;
554 
555                                         ubifs_pad(c, buf, pad_len);
556                                 }
557                         }
558                         err = ubifs_leb_change(c, lnum, sleb->buf, len);
559                         if (err)
560                                 return err;
561                 }
562         }
563         return 0;
564 }
565 
566 /**
567  * drop_last_group - drop the last group of nodes.
568  * @sleb: scanned LEB information
569  * @offs: offset of dropped nodes is returned here
570  *
571  * This is a helper function for 'ubifs_recover_leb()' which drops the last
572  * group of nodes of the scanned LEB.
573  */
574 static void drop_last_group(struct ubifs_scan_leb *sleb, int *offs)
575 {
576         while (!list_empty(&sleb->nodes)) {
577                 struct ubifs_scan_node *snod;
578                 struct ubifs_ch *ch;
579 
580                 snod = list_entry(sleb->nodes.prev, struct ubifs_scan_node,
581                                   list);
582                 ch = snod->node;
583                 if (ch->group_type != UBIFS_IN_NODE_GROUP)
584                         break;
585 
586                 dbg_rcvry("dropping grouped node at %d:%d",
587                           sleb->lnum, snod->offs);
588                 *offs = snod->offs;
589                 list_del(&snod->list);
590                 kfree(snod);
591                 sleb->nodes_cnt -= 1;
592         }
593 }
594 
595 /**
596  * drop_last_node - drop the last node.
597  * @sleb: scanned LEB information
598  * @offs: offset of dropped nodes is returned here
599  *
600  * This is a helper function for 'ubifs_recover_leb()' which drops the last
601  * node of the scanned LEB.
602  */
603 static void drop_last_node(struct ubifs_scan_leb *sleb, int *offs)
604 {
605         struct ubifs_scan_node *snod;
606 
607         if (!list_empty(&sleb->nodes)) {
608                 snod = list_entry(sleb->nodes.prev, struct ubifs_scan_node,
609                                   list);
610 
611                 dbg_rcvry("dropping last node at %d:%d",
612                           sleb->lnum, snod->offs);
613                 *offs = snod->offs;
614                 list_del(&snod->list);
615                 kfree(snod);
616                 sleb->nodes_cnt -= 1;
617         }
618 }
619 
620 /**
621  * ubifs_recover_leb - scan and recover a LEB.
622  * @c: UBIFS file-system description object
623  * @lnum: LEB number
624  * @offs: offset
625  * @sbuf: LEB-sized buffer to use
626  * @jhead: journal head number this LEB belongs to (%-1 if the LEB does not
627  *         belong to any journal head)
628  *
629  * This function does a scan of a LEB, but caters for errors that might have
630  * been caused by the unclean unmount from which we are attempting to recover.
631  * Returns the scanned information on success and a negative error code on
632  * failure.
633  */
634 struct ubifs_scan_leb *ubifs_recover_leb(struct ubifs_info *c, int lnum,
635                                          int offs, void *sbuf, int jhead)
636 {
637         int ret = 0, err, len = c->leb_size - offs, start = offs, min_io_unit;
638         int grouped = jhead == -1 ? 0 : c->jheads[jhead].grouped;
639         struct ubifs_scan_leb *sleb;
640         void *buf = sbuf + offs;
641 
642         dbg_rcvry("%d:%d, jhead %d, grouped %d", lnum, offs, jhead, grouped);
643 
644         sleb = ubifs_start_scan(c, lnum, offs, sbuf);
645         if (IS_ERR(sleb))
646                 return sleb;
647 
648         ubifs_assert(len >= 8);
649         while (len >= 8) {
650                 dbg_scan("look at LEB %d:%d (%d bytes left)",
651                          lnum, offs, len);
652 
653                 cond_resched();
654 
655                 /*
656                  * Scan quietly until there is an error from which we cannot
657                  * recover
658                  */
659                 ret = ubifs_scan_a_node(c, buf, len, lnum, offs, 1);
660                 if (ret == SCANNED_A_NODE) {
661                         /* A valid node, and not a padding node */
662                         struct ubifs_ch *ch = buf;
663                         int node_len;
664 
665                         err = ubifs_add_snod(c, sleb, buf, offs);
666                         if (err)
667                                 goto error;
668                         node_len = ALIGN(le32_to_cpu(ch->len), 8);
669                         offs += node_len;
670                         buf += node_len;
671                         len -= node_len;
672                 } else if (ret > 0) {
673                         /* Padding bytes or a valid padding node */
674                         offs += ret;
675                         buf += ret;
676                         len -= ret;
677                 } else if (ret == SCANNED_EMPTY_SPACE ||
678                            ret == SCANNED_GARBAGE     ||
679                            ret == SCANNED_A_BAD_PAD_NODE ||
680                            ret == SCANNED_A_CORRUPT_NODE) {
681                         dbg_rcvry("found corruption (%d) at %d:%d",
682                                   ret, lnum, offs);
683                         break;
684                 } else {
685                         ubifs_err(c, "unexpected return value %d", ret);
686                         err = -EINVAL;
687                         goto error;
688                 }
689         }
690 
691         if (ret == SCANNED_GARBAGE || ret == SCANNED_A_BAD_PAD_NODE) {
692                 if (!is_last_write(c, buf, offs))
693                         goto corrupted_rescan;
694         } else if (ret == SCANNED_A_CORRUPT_NODE) {
695                 if (!no_more_nodes(c, buf, len, lnum, offs))
696                         goto corrupted_rescan;
697         } else if (!is_empty(buf, len)) {
698                 if (!is_last_write(c, buf, offs)) {
699                         int corruption = first_non_ff(buf, len);
700 
701                         /*
702                          * See header comment for this file for more
703                          * explanations about the reasons we have this check.
704                          */
705                         ubifs_err(c, "corrupt empty space LEB %d:%d, corruption starts at %d",
706                                   lnum, offs, corruption);
707                         /* Make sure we dump interesting non-0xFF data */
708                         offs += corruption;
709                         buf += corruption;
710                         goto corrupted;
711                 }
712         }
713 
714         min_io_unit = round_down(offs, c->min_io_size);
715         if (grouped)
716                 /*
717                  * If nodes are grouped, always drop the incomplete group at
718                  * the end.
719                  */
720                 drop_last_group(sleb, &offs);
721 
722         if (jhead == GCHD) {
723                 /*
724                  * If this LEB belongs to the GC head then while we are in the
725                  * middle of the same min. I/O unit keep dropping nodes. So
726                  * basically, what we want is to make sure that the last min.
727                  * I/O unit where we saw the corruption is dropped completely
728                  * with all the uncorrupted nodes which may possibly sit there.
729                  *
730                  * In other words, let's name the min. I/O unit where the
731                  * corruption starts B, and the previous min. I/O unit A. The
732                  * below code tries to deal with a situation when half of B
733                  * contains valid nodes or the end of a valid node, and the
734                  * second half of B contains corrupted data or garbage. This
735                  * means that UBIFS had been writing to B just before the power
736                  * cut happened. I do not know how realistic is this scenario
737                  * that half of the min. I/O unit had been written successfully
738                  * and the other half not, but this is possible in our 'failure
739                  * mode emulation' infrastructure at least.
740                  *
741                  * So what is the problem, why we need to drop those nodes? Why
742                  * can't we just clean-up the second half of B by putting a
743                  * padding node there? We can, and this works fine with one
744                  * exception which was reproduced with power cut emulation
745                  * testing and happens extremely rarely.
746                  *
747                  * Imagine the file-system is full, we run GC which starts
748                  * moving valid nodes from LEB X to LEB Y (obviously, LEB Y is
749                  * the current GC head LEB). The @c->gc_lnum is -1, which means
750                  * that GC will retain LEB X and will try to continue. Imagine
751                  * that LEB X is currently the dirtiest LEB, and the amount of
752                  * used space in LEB Y is exactly the same as amount of free
753                  * space in LEB X.
754                  *
755                  * And a power cut happens when nodes are moved from LEB X to
756                  * LEB Y. We are here trying to recover LEB Y which is the GC
757                  * head LEB. We find the min. I/O unit B as described above.
758                  * Then we clean-up LEB Y by padding min. I/O unit. And later
759                  * 'ubifs_rcvry_gc_commit()' function fails, because it cannot
760                  * find a dirty LEB which could be GC'd into LEB Y! Even LEB X
761                  * does not match because the amount of valid nodes there does
762                  * not fit the free space in LEB Y any more! And this is
763                  * because of the padding node which we added to LEB Y. The
764                  * user-visible effect of this which I once observed and
765                  * analysed is that we cannot mount the file-system with
766                  * -ENOSPC error.
767                  *
768                  * So obviously, to make sure that situation does not happen we
769                  * should free min. I/O unit B in LEB Y completely and the last
770                  * used min. I/O unit in LEB Y should be A. This is basically
771                  * what the below code tries to do.
772                  */
773                 while (offs > min_io_unit)
774                         drop_last_node(sleb, &offs);
775         }
776 
777         buf = sbuf + offs;
778         len = c->leb_size - offs;
779 
780         clean_buf(c, &buf, lnum, &offs, &len);
781         ubifs_end_scan(c, sleb, lnum, offs);
782 
783         err = fix_unclean_leb(c, sleb, start);
784         if (err)
785                 goto error;
786 
787         return sleb;
788 
789 corrupted_rescan:
790         /* Re-scan the corrupted data with verbose messages */
791         ubifs_err(c, "corruption %d", ret);
792         ubifs_scan_a_node(c, buf, len, lnum, offs, 0);
793 corrupted:
794         ubifs_scanned_corruption(c, lnum, offs, buf);
795         err = -EUCLEAN;
796 error:
797         ubifs_err(c, "LEB %d scanning failed", lnum);
798         ubifs_scan_destroy(sleb);
799         return ERR_PTR(err);
800 }
801 
802 /**
803  * get_cs_sqnum - get commit start sequence number.
804  * @c: UBIFS file-system description object
805  * @lnum: LEB number of commit start node
806  * @offs: offset of commit start node
807  * @cs_sqnum: commit start sequence number is returned here
808  *
809  * This function returns %0 on success and a negative error code on failure.
810  */
811 static int get_cs_sqnum(struct ubifs_info *c, int lnum, int offs,
812                         unsigned long long *cs_sqnum)
813 {
814         struct ubifs_cs_node *cs_node = NULL;
815         int err, ret;
816 
817         dbg_rcvry("at %d:%d", lnum, offs);
818         cs_node = kmalloc(UBIFS_CS_NODE_SZ, GFP_KERNEL);
819         if (!cs_node)
820                 return -ENOMEM;
821         if (c->leb_size - offs < UBIFS_CS_NODE_SZ)
822                 goto out_err;
823         err = ubifs_leb_read(c, lnum, (void *)cs_node, offs,
824                              UBIFS_CS_NODE_SZ, 0);
825         if (err && err != -EBADMSG)
826                 goto out_free;
827         ret = ubifs_scan_a_node(c, cs_node, UBIFS_CS_NODE_SZ, lnum, offs, 0);
828         if (ret != SCANNED_A_NODE) {
829                 ubifs_err(c, "Not a valid node");
830                 goto out_err;
831         }
832         if (cs_node->ch.node_type != UBIFS_CS_NODE) {
833                 ubifs_err(c, "Node a CS node, type is %d", cs_node->ch.node_type);
834                 goto out_err;
835         }
836         if (le64_to_cpu(cs_node->cmt_no) != c->cmt_no) {
837                 ubifs_err(c, "CS node cmt_no %llu != current cmt_no %llu",
838                           (unsigned long long)le64_to_cpu(cs_node->cmt_no),
839                           c->cmt_no);
840                 goto out_err;
841         }
842         *cs_sqnum = le64_to_cpu(cs_node->ch.sqnum);
843         dbg_rcvry("commit start sqnum %llu", *cs_sqnum);
844         kfree(cs_node);
845         return 0;
846 
847 out_err:
848         err = -EINVAL;
849 out_free:
850         ubifs_err(c, "failed to get CS sqnum");
851         kfree(cs_node);
852         return err;
853 }
854 
855 /**
856  * ubifs_recover_log_leb - scan and recover a log LEB.
857  * @c: UBIFS file-system description object
858  * @lnum: LEB number
859  * @offs: offset
860  * @sbuf: LEB-sized buffer to use
861  *
862  * This function does a scan of a LEB, but caters for errors that might have
863  * been caused by unclean reboots from which we are attempting to recover
864  * (assume that only the last log LEB can be corrupted by an unclean reboot).
865  *
866  * This function returns %0 on success and a negative error code on failure.
867  */
868 struct ubifs_scan_leb *ubifs_recover_log_leb(struct ubifs_info *c, int lnum,
869                                              int offs, void *sbuf)
870 {
871         struct ubifs_scan_leb *sleb;
872         int next_lnum;
873 
874         dbg_rcvry("LEB %d", lnum);
875         next_lnum = lnum + 1;
876         if (next_lnum >= UBIFS_LOG_LNUM + c->log_lebs)
877                 next_lnum = UBIFS_LOG_LNUM;
878         if (next_lnum != c->ltail_lnum) {
879                 /*
880                  * We can only recover at the end of the log, so check that the
881                  * next log LEB is empty or out of date.
882                  */
883                 sleb = ubifs_scan(c, next_lnum, 0, sbuf, 0);
884                 if (IS_ERR(sleb))
885                         return sleb;
886                 if (sleb->nodes_cnt) {
887                         struct ubifs_scan_node *snod;
888                         unsigned long long cs_sqnum = c->cs_sqnum;
889 
890                         snod = list_entry(sleb->nodes.next,
891                                           struct ubifs_scan_node, list);
892                         if (cs_sqnum == 0) {
893                                 int err;
894 
895                                 err = get_cs_sqnum(c, lnum, offs, &cs_sqnum);
896                                 if (err) {
897                                         ubifs_scan_destroy(sleb);
898                                         return ERR_PTR(err);
899                                 }
900                         }
901                         if (snod->sqnum > cs_sqnum) {
902                                 ubifs_err(c, "unrecoverable log corruption in LEB %d",
903                                           lnum);
904                                 ubifs_scan_destroy(sleb);
905                                 return ERR_PTR(-EUCLEAN);
906                         }
907                 }
908                 ubifs_scan_destroy(sleb);
909         }
910         return ubifs_recover_leb(c, lnum, offs, sbuf, -1);
911 }
912 
913 /**
914  * recover_head - recover a head.
915  * @c: UBIFS file-system description object
916  * @lnum: LEB number of head to recover
917  * @offs: offset of head to recover
918  * @sbuf: LEB-sized buffer to use
919  *
920  * This function ensures that there is no data on the flash at a head location.
921  *
922  * This function returns %0 on success and a negative error code on failure.
923  */
924 static int recover_head(struct ubifs_info *c, int lnum, int offs, void *sbuf)
925 {
926         int len = c->max_write_size, err;
927 
928         if (offs + len > c->leb_size)
929                 len = c->leb_size - offs;
930 
931         if (!len)
932                 return 0;
933 
934         /* Read at the head location and check it is empty flash */
935         err = ubifs_leb_read(c, lnum, sbuf, offs, len, 1);
936         if (err || !is_empty(sbuf, len)) {
937                 dbg_rcvry("cleaning head at %d:%d", lnum, offs);
938                 if (offs == 0)
939                         return ubifs_leb_unmap(c, lnum);
940                 err = ubifs_leb_read(c, lnum, sbuf, 0, offs, 1);
941                 if (err)
942                         return err;
943                 return ubifs_leb_change(c, lnum, sbuf, offs);
944         }
945 
946         return 0;
947 }
948 
949 /**
950  * ubifs_recover_inl_heads - recover index and LPT heads.
951  * @c: UBIFS file-system description object
952  * @sbuf: LEB-sized buffer to use
953  *
954  * This function ensures that there is no data on the flash at the index and
955  * LPT head locations.
956  *
957  * This deals with the recovery of a half-completed journal commit. UBIFS is
958  * careful never to overwrite the last version of the index or the LPT. Because
959  * the index and LPT are wandering trees, data from a half-completed commit will
960  * not be referenced anywhere in UBIFS. The data will be either in LEBs that are
961  * assumed to be empty and will be unmapped anyway before use, or in the index
962  * and LPT heads.
963  *
964  * This function returns %0 on success and a negative error code on failure.
965  */
966 int ubifs_recover_inl_heads(struct ubifs_info *c, void *sbuf)
967 {
968         int err;
969 
970         ubifs_assert(!c->ro_mount || c->remounting_rw);
971 
972         dbg_rcvry("checking index head at %d:%d", c->ihead_lnum, c->ihead_offs);
973         err = recover_head(c, c->ihead_lnum, c->ihead_offs, sbuf);
974         if (err)
975                 return err;
976 
977         dbg_rcvry("checking LPT head at %d:%d", c->nhead_lnum, c->nhead_offs);
978 
979         return recover_head(c, c->nhead_lnum, c->nhead_offs, sbuf);
980 }
981 
982 /**
983  * clean_an_unclean_leb - read and write a LEB to remove corruption.
984  * @c: UBIFS file-system description object
985  * @ucleb: unclean LEB information
986  * @sbuf: LEB-sized buffer to use
987  *
988  * This function reads a LEB up to a point pre-determined by the mount recovery,
989  * checks the nodes, and writes the result back to the flash, thereby cleaning
990  * off any following corruption, or non-fatal ECC errors.
991  *
992  * This function returns %0 on success and a negative error code on failure.
993  */
994 static int clean_an_unclean_leb(struct ubifs_info *c,
995                                 struct ubifs_unclean_leb *ucleb, void *sbuf)
996 {
997         int err, lnum = ucleb->lnum, offs = 0, len = ucleb->endpt, quiet = 1;
998         void *buf = sbuf;
999 
1000         dbg_rcvry("LEB %d len %d", lnum, len);
1001 
1002         if (len == 0) {
1003                 /* Nothing to read, just unmap it */
1004                 return ubifs_leb_unmap(c, lnum);
1005         }
1006 
1007         err = ubifs_leb_read(c, lnum, buf, offs, len, 0);
1008         if (err && err != -EBADMSG)
1009                 return err;
1010 
1011         while (len >= 8) {
1012                 int ret;
1013 
1014                 cond_resched();
1015 
1016                 /* Scan quietly until there is an error */
1017                 ret = ubifs_scan_a_node(c, buf, len, lnum, offs, quiet);
1018 
1019                 if (ret == SCANNED_A_NODE) {
1020                         /* A valid node, and not a padding node */
1021                         struct ubifs_ch *ch = buf;
1022                         int node_len;
1023 
1024                         node_len = ALIGN(le32_to_cpu(ch->len), 8);
1025                         offs += node_len;
1026                         buf += node_len;
1027                         len -= node_len;
1028                         continue;
1029                 }
1030 
1031                 if (ret > 0) {
1032                         /* Padding bytes or a valid padding node */
1033                         offs += ret;
1034                         buf += ret;
1035                         len -= ret;
1036                         continue;
1037                 }
1038 
1039                 if (ret == SCANNED_EMPTY_SPACE) {
1040                         ubifs_err(c, "unexpected empty space at %d:%d",
1041                                   lnum, offs);
1042                         return -EUCLEAN;
1043                 }
1044 
1045                 if (quiet) {
1046                         /* Redo the last scan but noisily */
1047                         quiet = 0;
1048                         continue;
1049                 }
1050 
1051                 ubifs_scanned_corruption(c, lnum, offs, buf);
1052                 return -EUCLEAN;
1053         }
1054 
1055         /* Pad to min_io_size */
1056         len = ALIGN(ucleb->endpt, c->min_io_size);
1057         if (len > ucleb->endpt) {
1058                 int pad_len = len - ALIGN(ucleb->endpt, 8);
1059 
1060                 if (pad_len > 0) {
1061                         buf = c->sbuf + len - pad_len;
1062                         ubifs_pad(c, buf, pad_len);
1063                 }
1064         }
1065 
1066         /* Write back the LEB atomically */
1067         err = ubifs_leb_change(c, lnum, sbuf, len);
1068         if (err)
1069                 return err;
1070 
1071         dbg_rcvry("cleaned LEB %d", lnum);
1072 
1073         return 0;
1074 }
1075 
1076 /**
1077  * ubifs_clean_lebs - clean LEBs recovered during read-only mount.
1078  * @c: UBIFS file-system description object
1079  * @sbuf: LEB-sized buffer to use
1080  *
1081  * This function cleans a LEB identified during recovery that needs to be
1082  * written but was not because UBIFS was mounted read-only. This happens when
1083  * remounting to read-write mode.
1084  *
1085  * This function returns %0 on success and a negative error code on failure.
1086  */
1087 int ubifs_clean_lebs(struct ubifs_info *c, void *sbuf)
1088 {
1089         dbg_rcvry("recovery");
1090         while (!list_empty(&c->unclean_leb_list)) {
1091                 struct ubifs_unclean_leb *ucleb;
1092                 int err;
1093 
1094                 ucleb = list_entry(c->unclean_leb_list.next,
1095                                    struct ubifs_unclean_leb, list);
1096                 err = clean_an_unclean_leb(c, ucleb, sbuf);
1097                 if (err)
1098                         return err;
1099                 list_del(&ucleb->list);
1100                 kfree(ucleb);
1101         }
1102         return 0;
1103 }
1104 
1105 /**
1106  * grab_empty_leb - grab an empty LEB to use as GC LEB and run commit.
1107  * @c: UBIFS file-system description object
1108  *
1109  * This is a helper function for 'ubifs_rcvry_gc_commit()' which grabs an empty
1110  * LEB to be used as GC LEB (@c->gc_lnum), and then runs the commit. Returns
1111  * zero in case of success and a negative error code in case of failure.
1112  */
1113 static int grab_empty_leb(struct ubifs_info *c)
1114 {
1115         int lnum, err;
1116 
1117         /*
1118          * Note, it is very important to first search for an empty LEB and then
1119          * run the commit, not vice-versa. The reason is that there might be
1120          * only one empty LEB at the moment, the one which has been the
1121          * @c->gc_lnum just before the power cut happened. During the regular
1122          * UBIFS operation (not now) @c->gc_lnum is marked as "taken", so no
1123          * one but GC can grab it. But at this moment this single empty LEB is
1124          * not marked as taken, so if we run commit - what happens? Right, the
1125          * commit will grab it and write the index there. Remember that the
1126          * index always expands as long as there is free space, and it only
1127          * starts consolidating when we run out of space.
1128          *
1129          * IOW, if we run commit now, we might not be able to find a free LEB
1130          * after this.
1131          */
1132         lnum = ubifs_find_free_leb_for_idx(c);
1133         if (lnum < 0) {
1134                 ubifs_err(c, "could not find an empty LEB");
1135                 ubifs_dump_lprops(c);
1136                 ubifs_dump_budg(c, &c->bi);
1137                 return lnum;
1138         }
1139 
1140         /* Reset the index flag */
1141         err = ubifs_change_one_lp(c, lnum, LPROPS_NC, LPROPS_NC, 0,
1142                                   LPROPS_INDEX, 0);
1143         if (err)
1144                 return err;
1145 
1146         c->gc_lnum = lnum;
1147         dbg_rcvry("found empty LEB %d, run commit", lnum);
1148 
1149         return ubifs_run_commit(c);
1150 }
1151 
1152 /**
1153  * ubifs_rcvry_gc_commit - recover the GC LEB number and run the commit.
1154  * @c: UBIFS file-system description object
1155  *
1156  * Out-of-place garbage collection requires always one empty LEB with which to
1157  * start garbage collection. The LEB number is recorded in c->gc_lnum and is
1158  * written to the master node on unmounting. In the case of an unclean unmount
1159  * the value of gc_lnum recorded in the master node is out of date and cannot
1160  * be used. Instead, recovery must allocate an empty LEB for this purpose.
1161  * However, there may not be enough empty space, in which case it must be
1162  * possible to GC the dirtiest LEB into the GC head LEB.
1163  *
1164  * This function also runs the commit which causes the TNC updates from
1165  * size-recovery and orphans to be written to the flash. That is important to
1166  * ensure correct replay order for subsequent mounts.
1167  *
1168  * This function returns %0 on success and a negative error code on failure.
1169  */
1170 int ubifs_rcvry_gc_commit(struct ubifs_info *c)
1171 {
1172         struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
1173         struct ubifs_lprops lp;
1174         int err;
1175 
1176         dbg_rcvry("GC head LEB %d, offs %d", wbuf->lnum, wbuf->offs);
1177 
1178         c->gc_lnum = -1;
1179         if (wbuf->lnum == -1 || wbuf->offs == c->leb_size)
1180                 return grab_empty_leb(c);
1181 
1182         err = ubifs_find_dirty_leb(c, &lp, wbuf->offs, 2);
1183         if (err) {
1184                 if (err != -ENOSPC)
1185                         return err;
1186 
1187                 dbg_rcvry("could not find a dirty LEB");
1188                 return grab_empty_leb(c);
1189         }
1190 
1191         ubifs_assert(!(lp.flags & LPROPS_INDEX));
1192         ubifs_assert(lp.free + lp.dirty >= wbuf->offs);
1193 
1194         /*
1195          * We run the commit before garbage collection otherwise subsequent
1196          * mounts will see the GC and orphan deletion in a different order.
1197          */
1198         dbg_rcvry("committing");
1199         err = ubifs_run_commit(c);
1200         if (err)
1201                 return err;
1202 
1203         dbg_rcvry("GC'ing LEB %d", lp.lnum);
1204         mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
1205         err = ubifs_garbage_collect_leb(c, &lp);
1206         if (err >= 0) {
1207                 int err2 = ubifs_wbuf_sync_nolock(wbuf);
1208 
1209                 if (err2)
1210                         err = err2;
1211         }
1212         mutex_unlock(&wbuf->io_mutex);
1213         if (err < 0) {
1214                 ubifs_err(c, "GC failed, error %d", err);
1215                 if (err == -EAGAIN)
1216                         err = -EINVAL;
1217                 return err;
1218         }
1219 
1220         ubifs_assert(err == LEB_RETAINED);
1221         if (err != LEB_RETAINED)
1222                 return -EINVAL;
1223 
1224         err = ubifs_leb_unmap(c, c->gc_lnum);
1225         if (err)
1226                 return err;
1227 
1228         dbg_rcvry("allocated LEB %d for GC", lp.lnum);
1229         return 0;
1230 }
1231 
1232 /**
1233  * struct size_entry - inode size information for recovery.
1234  * @rb: link in the RB-tree of sizes
1235  * @inum: inode number
1236  * @i_size: size on inode
1237  * @d_size: maximum size based on data nodes
1238  * @exists: indicates whether the inode exists
1239  * @inode: inode if pinned in memory awaiting rw mode to fix it
1240  */
1241 struct size_entry {
1242         struct rb_node rb;
1243         ino_t inum;
1244         loff_t i_size;
1245         loff_t d_size;
1246         int exists;
1247         struct inode *inode;
1248 };
1249 
1250 /**
1251  * add_ino - add an entry to the size tree.
1252  * @c: UBIFS file-system description object
1253  * @inum: inode number
1254  * @i_size: size on inode
1255  * @d_size: maximum size based on data nodes
1256  * @exists: indicates whether the inode exists
1257  */
1258 static int add_ino(struct ubifs_info *c, ino_t inum, loff_t i_size,
1259                    loff_t d_size, int exists)
1260 {
1261         struct rb_node **p = &c->size_tree.rb_node, *parent = NULL;
1262         struct size_entry *e;
1263 
1264         while (*p) {
1265                 parent = *p;
1266                 e = rb_entry(parent, struct size_entry, rb);
1267                 if (inum < e->inum)
1268                         p = &(*p)->rb_left;
1269                 else
1270                         p = &(*p)->rb_right;
1271         }
1272 
1273         e = kzalloc(sizeof(struct size_entry), GFP_KERNEL);
1274         if (!e)
1275                 return -ENOMEM;
1276 
1277         e->inum = inum;
1278         e->i_size = i_size;
1279         e->d_size = d_size;
1280         e->exists = exists;
1281 
1282         rb_link_node(&e->rb, parent, p);
1283         rb_insert_color(&e->rb, &c->size_tree);
1284 
1285         return 0;
1286 }
1287 
1288 /**
1289  * find_ino - find an entry on the size tree.
1290  * @c: UBIFS file-system description object
1291  * @inum: inode number
1292  */
1293 static struct size_entry *find_ino(struct ubifs_info *c, ino_t inum)
1294 {
1295         struct rb_node *p = c->size_tree.rb_node;
1296         struct size_entry *e;
1297 
1298         while (p) {
1299                 e = rb_entry(p, struct size_entry, rb);
1300                 if (inum < e->inum)
1301                         p = p->rb_left;
1302                 else if (inum > e->inum)
1303                         p = p->rb_right;
1304                 else
1305                         return e;
1306         }
1307         return NULL;
1308 }
1309 
1310 /**
1311  * remove_ino - remove an entry from the size tree.
1312  * @c: UBIFS file-system description object
1313  * @inum: inode number
1314  */
1315 static void remove_ino(struct ubifs_info *c, ino_t inum)
1316 {
1317         struct size_entry *e = find_ino(c, inum);
1318 
1319         if (!e)
1320                 return;
1321         rb_erase(&e->rb, &c->size_tree);
1322         kfree(e);
1323 }
1324 
1325 /**
1326  * ubifs_destroy_size_tree - free resources related to the size tree.
1327  * @c: UBIFS file-system description object
1328  */
1329 void ubifs_destroy_size_tree(struct ubifs_info *c)
1330 {
1331         struct size_entry *e, *n;
1332 
1333         rbtree_postorder_for_each_entry_safe(e, n, &c->size_tree, rb) {
1334                 iput(e->inode);
1335                 kfree(e);
1336         }
1337 
1338         c->size_tree = RB_ROOT;
1339 }
1340 
1341 /**
1342  * ubifs_recover_size_accum - accumulate inode sizes for recovery.
1343  * @c: UBIFS file-system description object
1344  * @key: node key
1345  * @deletion: node is for a deletion
1346  * @new_size: inode size
1347  *
1348  * This function has two purposes:
1349  *     1) to ensure there are no data nodes that fall outside the inode size
1350  *     2) to ensure there are no data nodes for inodes that do not exist
1351  * To accomplish those purposes, a rb-tree is constructed containing an entry
1352  * for each inode number in the journal that has not been deleted, and recording
1353  * the size from the inode node, the maximum size of any data node (also altered
1354  * by truncations) and a flag indicating a inode number for which no inode node
1355  * was present in the journal.
1356  *
1357  * Note that there is still the possibility that there are data nodes that have
1358  * been committed that are beyond the inode size, however the only way to find
1359  * them would be to scan the entire index. Alternatively, some provision could
1360  * be made to record the size of inodes at the start of commit, which would seem
1361  * very cumbersome for a scenario that is quite unlikely and the only negative
1362  * consequence of which is wasted space.
1363  *
1364  * This functions returns %0 on success and a negative error code on failure.
1365  */
1366 int ubifs_recover_size_accum(struct ubifs_info *c, union ubifs_key *key,
1367                              int deletion, loff_t new_size)
1368 {
1369         ino_t inum = key_inum(c, key);
1370         struct size_entry *e;
1371         int err;
1372 
1373         switch (key_type(c, key)) {
1374         case UBIFS_INO_KEY:
1375                 if (deletion)
1376                         remove_ino(c, inum);
1377                 else {
1378                         e = find_ino(c, inum);
1379                         if (e) {
1380                                 e->i_size = new_size;
1381                                 e->exists = 1;
1382                         } else {
1383                                 err = add_ino(c, inum, new_size, 0, 1);
1384                                 if (err)
1385                                         return err;
1386                         }
1387                 }
1388                 break;
1389         case UBIFS_DATA_KEY:
1390                 e = find_ino(c, inum);
1391                 if (e) {
1392                         if (new_size > e->d_size)
1393                                 e->d_size = new_size;
1394                 } else {
1395                         err = add_ino(c, inum, 0, new_size, 0);
1396                         if (err)
1397                                 return err;
1398                 }
1399                 break;
1400         case UBIFS_TRUN_KEY:
1401                 e = find_ino(c, inum);
1402                 if (e)
1403                         e->d_size = new_size;
1404                 break;
1405         }
1406         return 0;
1407 }
1408 
1409 /**
1410  * fix_size_in_place - fix inode size in place on flash.
1411  * @c: UBIFS file-system description object
1412  * @e: inode size information for recovery
1413  */
1414 static int fix_size_in_place(struct ubifs_info *c, struct size_entry *e)
1415 {
1416         struct ubifs_ino_node *ino = c->sbuf;
1417         unsigned char *p;
1418         union ubifs_key key;
1419         int err, lnum, offs, len;
1420         loff_t i_size;
1421         uint32_t crc;
1422 
1423         /* Locate the inode node LEB number and offset */
1424         ino_key_init(c, &key, e->inum);
1425         err = ubifs_tnc_locate(c, &key, ino, &lnum, &offs);
1426         if (err)
1427                 goto out;
1428         /*
1429          * If the size recorded on the inode node is greater than the size that
1430          * was calculated from nodes in the journal then don't change the inode.
1431          */
1432         i_size = le64_to_cpu(ino->size);
1433         if (i_size >= e->d_size)
1434                 return 0;
1435         /* Read the LEB */
1436         err = ubifs_leb_read(c, lnum, c->sbuf, 0, c->leb_size, 1);
1437         if (err)
1438                 goto out;
1439         /* Change the size field and recalculate the CRC */
1440         ino = c->sbuf + offs;
1441         ino->size = cpu_to_le64(e->d_size);
1442         len = le32_to_cpu(ino->ch.len);
1443         crc = crc32(UBIFS_CRC32_INIT, (void *)ino + 8, len - 8);
1444         ino->ch.crc = cpu_to_le32(crc);
1445         /* Work out where data in the LEB ends and free space begins */
1446         p = c->sbuf;
1447         len = c->leb_size - 1;
1448         while (p[len] == 0xff)
1449                 len -= 1;
1450         len = ALIGN(len + 1, c->min_io_size);
1451         /* Atomically write the fixed LEB back again */
1452         err = ubifs_leb_change(c, lnum, c->sbuf, len);
1453         if (err)
1454                 goto out;
1455         dbg_rcvry("inode %lu at %d:%d size %lld -> %lld",
1456                   (unsigned long)e->inum, lnum, offs, i_size, e->d_size);
1457         return 0;
1458 
1459 out:
1460         ubifs_warn(c, "inode %lu failed to fix size %lld -> %lld error %d",
1461                    (unsigned long)e->inum, e->i_size, e->d_size, err);
1462         return err;
1463 }
1464 
1465 /**
1466  * ubifs_recover_size - recover inode size.
1467  * @c: UBIFS file-system description object
1468  *
1469  * This function attempts to fix inode size discrepancies identified by the
1470  * 'ubifs_recover_size_accum()' function.
1471  *
1472  * This functions returns %0 on success and a negative error code on failure.
1473  */
1474 int ubifs_recover_size(struct ubifs_info *c)
1475 {
1476         struct rb_node *this = rb_first(&c->size_tree);
1477 
1478         while (this) {
1479                 struct size_entry *e;
1480                 int err;
1481 
1482                 e = rb_entry(this, struct size_entry, rb);
1483                 if (!e->exists) {
1484                         union ubifs_key key;
1485 
1486                         ino_key_init(c, &key, e->inum);
1487                         err = ubifs_tnc_lookup(c, &key, c->sbuf);
1488                         if (err && err != -ENOENT)
1489                                 return err;
1490                         if (err == -ENOENT) {
1491                                 /* Remove data nodes that have no inode */
1492                                 dbg_rcvry("removing ino %lu",
1493                                           (unsigned long)e->inum);
1494                                 err = ubifs_tnc_remove_ino(c, e->inum);
1495                                 if (err)
1496                                         return err;
1497                         } else {
1498                                 struct ubifs_ino_node *ino = c->sbuf;
1499 
1500                                 e->exists = 1;
1501                                 e->i_size = le64_to_cpu(ino->size);
1502                         }
1503                 }
1504 
1505                 if (e->exists && e->i_size < e->d_size) {
1506                         if (c->ro_mount) {
1507                                 /* Fix the inode size and pin it in memory */
1508                                 struct inode *inode;
1509                                 struct ubifs_inode *ui;
1510 
1511                                 ubifs_assert(!e->inode);
1512 
1513                                 inode = ubifs_iget(c->vfs_sb, e->inum);
1514                                 if (IS_ERR(inode))
1515                                         return PTR_ERR(inode);
1516 
1517                                 ui = ubifs_inode(inode);
1518                                 if (inode->i_size < e->d_size) {
1519                                         dbg_rcvry("ino %lu size %lld -> %lld",
1520                                                   (unsigned long)e->inum,
1521                                                   inode->i_size, e->d_size);
1522                                         inode->i_size = e->d_size;
1523                                         ui->ui_size = e->d_size;
1524                                         ui->synced_i_size = e->d_size;
1525                                         e->inode = inode;
1526                                         this = rb_next(this);
1527                                         continue;
1528                                 }
1529                                 iput(inode);
1530                         } else {
1531                                 /* Fix the size in place */
1532                                 err = fix_size_in_place(c, e);
1533                                 if (err)
1534                                         return err;
1535                                 iput(e->inode);
1536                         }
1537                 }
1538 
1539                 this = rb_next(this);
1540                 rb_erase(&e->rb, &c->size_tree);
1541                 kfree(e);
1542         }
1543 
1544         return 0;
1545 }
1546 

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