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TOMOYO Linux Cross Reference
Linux/fs/ext4/fsmap.c

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  1 // SPDX-License-Identifier: GPL-2.0+
  2 /*
  3  * Copyright (C) 2017 Oracle.  All Rights Reserved.
  4  *
  5  * Author: Darrick J. Wong <darrick.wong@oracle.com>
  6  */
  7 #include "ext4.h"
  8 #include <linux/fsmap.h>
  9 #include "fsmap.h"
 10 #include "mballoc.h"
 11 #include <linux/sort.h>
 12 #include <linux/list_sort.h>
 13 #include <trace/events/ext4.h>
 14 
 15 /* Convert an ext4_fsmap to an fsmap. */
 16 void ext4_fsmap_from_internal(struct super_block *sb, struct fsmap *dest,
 17                               struct ext4_fsmap *src)
 18 {
 19         dest->fmr_device = src->fmr_device;
 20         dest->fmr_flags = src->fmr_flags;
 21         dest->fmr_physical = src->fmr_physical << sb->s_blocksize_bits;
 22         dest->fmr_owner = src->fmr_owner;
 23         dest->fmr_offset = 0;
 24         dest->fmr_length = src->fmr_length << sb->s_blocksize_bits;
 25         dest->fmr_reserved[0] = 0;
 26         dest->fmr_reserved[1] = 0;
 27         dest->fmr_reserved[2] = 0;
 28 }
 29 
 30 /* Convert an fsmap to an ext4_fsmap. */
 31 void ext4_fsmap_to_internal(struct super_block *sb, struct ext4_fsmap *dest,
 32                             struct fsmap *src)
 33 {
 34         dest->fmr_device = src->fmr_device;
 35         dest->fmr_flags = src->fmr_flags;
 36         dest->fmr_physical = src->fmr_physical >> sb->s_blocksize_bits;
 37         dest->fmr_owner = src->fmr_owner;
 38         dest->fmr_length = src->fmr_length >> sb->s_blocksize_bits;
 39 }
 40 
 41 /* getfsmap query state */
 42 struct ext4_getfsmap_info {
 43         struct ext4_fsmap_head  *gfi_head;
 44         ext4_fsmap_format_t     gfi_formatter;  /* formatting fn */
 45         void                    *gfi_format_arg;/* format buffer */
 46         ext4_fsblk_t            gfi_next_fsblk; /* next fsblock we expect */
 47         u32                     gfi_dev;        /* device id */
 48         ext4_group_t            gfi_agno;       /* bg number, if applicable */
 49         struct ext4_fsmap       gfi_low;        /* low rmap key */
 50         struct ext4_fsmap       gfi_high;       /* high rmap key */
 51         struct ext4_fsmap       gfi_lastfree;   /* free ext at end of last bg */
 52         struct list_head        gfi_meta_list;  /* fixed metadata list */
 53         bool                    gfi_last;       /* last extent? */
 54 };
 55 
 56 /* Associate a device with a getfsmap handler. */
 57 struct ext4_getfsmap_dev {
 58         int                     (*gfd_fn)(struct super_block *sb,
 59                                       struct ext4_fsmap *keys,
 60                                       struct ext4_getfsmap_info *info);
 61         u32                     gfd_dev;
 62 };
 63 
 64 /* Compare two getfsmap device handlers. */
 65 static int ext4_getfsmap_dev_compare(const void *p1, const void *p2)
 66 {
 67         const struct ext4_getfsmap_dev *d1 = p1;
 68         const struct ext4_getfsmap_dev *d2 = p2;
 69 
 70         return d1->gfd_dev - d2->gfd_dev;
 71 }
 72 
 73 /* Compare a record against our starting point */
 74 static bool ext4_getfsmap_rec_before_low_key(struct ext4_getfsmap_info *info,
 75                                              struct ext4_fsmap *rec)
 76 {
 77         return rec->fmr_physical < info->gfi_low.fmr_physical;
 78 }
 79 
 80 /*
 81  * Format a reverse mapping for getfsmap, having translated rm_startblock
 82  * into the appropriate daddr units.
 83  */
 84 static int ext4_getfsmap_helper(struct super_block *sb,
 85                                 struct ext4_getfsmap_info *info,
 86                                 struct ext4_fsmap *rec)
 87 {
 88         struct ext4_fsmap fmr;
 89         struct ext4_sb_info *sbi = EXT4_SB(sb);
 90         ext4_fsblk_t rec_fsblk = rec->fmr_physical;
 91         ext4_group_t agno;
 92         ext4_grpblk_t cno;
 93         int error;
 94 
 95         if (fatal_signal_pending(current))
 96                 return -EINTR;
 97 
 98         /*
 99          * Filter out records that start before our startpoint, if the
100          * caller requested that.
101          */
102         if (ext4_getfsmap_rec_before_low_key(info, rec)) {
103                 rec_fsblk += rec->fmr_length;
104                 if (info->gfi_next_fsblk < rec_fsblk)
105                         info->gfi_next_fsblk = rec_fsblk;
106                 return EXT4_QUERY_RANGE_CONTINUE;
107         }
108 
109         /* Are we just counting mappings? */
110         if (info->gfi_head->fmh_count == 0) {
111                 if (rec_fsblk > info->gfi_next_fsblk)
112                         info->gfi_head->fmh_entries++;
113 
114                 if (info->gfi_last)
115                         return EXT4_QUERY_RANGE_CONTINUE;
116 
117                 info->gfi_head->fmh_entries++;
118 
119                 rec_fsblk += rec->fmr_length;
120                 if (info->gfi_next_fsblk < rec_fsblk)
121                         info->gfi_next_fsblk = rec_fsblk;
122                 return EXT4_QUERY_RANGE_CONTINUE;
123         }
124 
125         /*
126          * If the record starts past the last physical block we saw,
127          * then we've found a gap.  Report the gap as being owned by
128          * whatever the caller specified is the missing owner.
129          */
130         if (rec_fsblk > info->gfi_next_fsblk) {
131                 if (info->gfi_head->fmh_entries >= info->gfi_head->fmh_count)
132                         return EXT4_QUERY_RANGE_ABORT;
133 
134                 ext4_get_group_no_and_offset(sb, info->gfi_next_fsblk,
135                                 &agno, &cno);
136                 trace_ext4_fsmap_mapping(sb, info->gfi_dev, agno,
137                                 EXT4_C2B(sbi, cno),
138                                 rec_fsblk - info->gfi_next_fsblk,
139                                 EXT4_FMR_OWN_UNKNOWN);
140 
141                 fmr.fmr_device = info->gfi_dev;
142                 fmr.fmr_physical = info->gfi_next_fsblk;
143                 fmr.fmr_owner = EXT4_FMR_OWN_UNKNOWN;
144                 fmr.fmr_length = rec_fsblk - info->gfi_next_fsblk;
145                 fmr.fmr_flags = FMR_OF_SPECIAL_OWNER;
146                 error = info->gfi_formatter(&fmr, info->gfi_format_arg);
147                 if (error)
148                         return error;
149                 info->gfi_head->fmh_entries++;
150         }
151 
152         if (info->gfi_last)
153                 goto out;
154 
155         /* Fill out the extent we found */
156         if (info->gfi_head->fmh_entries >= info->gfi_head->fmh_count)
157                 return EXT4_QUERY_RANGE_ABORT;
158 
159         ext4_get_group_no_and_offset(sb, rec_fsblk, &agno, &cno);
160         trace_ext4_fsmap_mapping(sb, info->gfi_dev, agno, EXT4_C2B(sbi, cno),
161                         rec->fmr_length, rec->fmr_owner);
162 
163         fmr.fmr_device = info->gfi_dev;
164         fmr.fmr_physical = rec_fsblk;
165         fmr.fmr_owner = rec->fmr_owner;
166         fmr.fmr_flags = FMR_OF_SPECIAL_OWNER;
167         fmr.fmr_length = rec->fmr_length;
168         error = info->gfi_formatter(&fmr, info->gfi_format_arg);
169         if (error)
170                 return error;
171         info->gfi_head->fmh_entries++;
172 
173 out:
174         rec_fsblk += rec->fmr_length;
175         if (info->gfi_next_fsblk < rec_fsblk)
176                 info->gfi_next_fsblk = rec_fsblk;
177         return EXT4_QUERY_RANGE_CONTINUE;
178 }
179 
180 static inline ext4_fsblk_t ext4_fsmap_next_pblk(struct ext4_fsmap *fmr)
181 {
182         return fmr->fmr_physical + fmr->fmr_length;
183 }
184 
185 /* Transform a blockgroup's free record into a fsmap */
186 static int ext4_getfsmap_datadev_helper(struct super_block *sb,
187                                         ext4_group_t agno, ext4_grpblk_t start,
188                                         ext4_grpblk_t len, void *priv)
189 {
190         struct ext4_fsmap irec;
191         struct ext4_getfsmap_info *info = priv;
192         struct ext4_fsmap *p;
193         struct ext4_fsmap *tmp;
194         struct ext4_sb_info *sbi = EXT4_SB(sb);
195         ext4_fsblk_t fsb;
196         ext4_fsblk_t fslen;
197         int error;
198 
199         fsb = (EXT4_C2B(sbi, start) + ext4_group_first_block_no(sb, agno));
200         fslen = EXT4_C2B(sbi, len);
201 
202         /* If the retained free extent record is set... */
203         if (info->gfi_lastfree.fmr_owner) {
204                 /* ...and abuts this one, lengthen it and return. */
205                 if (ext4_fsmap_next_pblk(&info->gfi_lastfree) == fsb) {
206                         info->gfi_lastfree.fmr_length += fslen;
207                         return 0;
208                 }
209 
210                 /*
211                  * There's a gap between the two free extents; emit the
212                  * retained extent prior to merging the meta_list.
213                  */
214                 error = ext4_getfsmap_helper(sb, info, &info->gfi_lastfree);
215                 if (error)
216                         return error;
217                 info->gfi_lastfree.fmr_owner = 0;
218         }
219 
220         /* Merge in any relevant extents from the meta_list */
221         list_for_each_entry_safe(p, tmp, &info->gfi_meta_list, fmr_list) {
222                 if (p->fmr_physical + p->fmr_length <= info->gfi_next_fsblk) {
223                         list_del(&p->fmr_list);
224                         kfree(p);
225                 } else if (p->fmr_physical < fsb) {
226                         error = ext4_getfsmap_helper(sb, info, p);
227                         if (error)
228                                 return error;
229 
230                         list_del(&p->fmr_list);
231                         kfree(p);
232                 }
233         }
234 
235         irec.fmr_device = 0;
236         irec.fmr_physical = fsb;
237         irec.fmr_length = fslen;
238         irec.fmr_owner = EXT4_FMR_OWN_FREE;
239         irec.fmr_flags = 0;
240 
241         /* If this is a free extent at the end of a bg, buffer it. */
242         if (ext4_fsmap_next_pblk(&irec) ==
243                         ext4_group_first_block_no(sb, agno + 1)) {
244                 info->gfi_lastfree = irec;
245                 return 0;
246         }
247 
248         /* Otherwise, emit it */
249         return ext4_getfsmap_helper(sb, info, &irec);
250 }
251 
252 /* Execute a getfsmap query against the log device. */
253 static int ext4_getfsmap_logdev(struct super_block *sb, struct ext4_fsmap *keys,
254                                 struct ext4_getfsmap_info *info)
255 {
256         journal_t *journal = EXT4_SB(sb)->s_journal;
257         struct ext4_fsmap irec;
258 
259         /* Set up search keys */
260         info->gfi_low = keys[0];
261         info->gfi_low.fmr_length = 0;
262 
263         memset(&info->gfi_high, 0xFF, sizeof(info->gfi_high));
264 
265         trace_ext4_fsmap_low_key(sb, info->gfi_dev, 0,
266                         info->gfi_low.fmr_physical,
267                         info->gfi_low.fmr_length,
268                         info->gfi_low.fmr_owner);
269 
270         trace_ext4_fsmap_high_key(sb, info->gfi_dev, 0,
271                         info->gfi_high.fmr_physical,
272                         info->gfi_high.fmr_length,
273                         info->gfi_high.fmr_owner);
274 
275         if (keys[0].fmr_physical > 0)
276                 return 0;
277 
278         /* Fabricate an rmap entry for the external log device. */
279         irec.fmr_physical = journal->j_blk_offset;
280         irec.fmr_length = journal->j_maxlen;
281         irec.fmr_owner = EXT4_FMR_OWN_LOG;
282         irec.fmr_flags = 0;
283 
284         return ext4_getfsmap_helper(sb, info, &irec);
285 }
286 
287 /* Helper to fill out an ext4_fsmap. */
288 static inline int ext4_getfsmap_fill(struct list_head *meta_list,
289                                      ext4_fsblk_t fsb, ext4_fsblk_t len,
290                                      uint64_t owner)
291 {
292         struct ext4_fsmap *fsm;
293 
294         fsm = kmalloc(sizeof(*fsm), GFP_NOFS);
295         if (!fsm)
296                 return -ENOMEM;
297         fsm->fmr_device = 0;
298         fsm->fmr_flags = 0;
299         fsm->fmr_physical = fsb;
300         fsm->fmr_owner = owner;
301         fsm->fmr_length = len;
302         list_add_tail(&fsm->fmr_list, meta_list);
303 
304         return 0;
305 }
306 
307 /*
308  * This function returns the number of file system metadata blocks at
309  * the beginning of a block group, including the reserved gdt blocks.
310  */
311 static unsigned int ext4_getfsmap_find_sb(struct super_block *sb,
312                                           ext4_group_t agno,
313                                           struct list_head *meta_list)
314 {
315         struct ext4_sb_info *sbi = EXT4_SB(sb);
316         ext4_fsblk_t fsb = ext4_group_first_block_no(sb, agno);
317         ext4_fsblk_t len;
318         unsigned long first_meta_bg = le32_to_cpu(sbi->s_es->s_first_meta_bg);
319         unsigned long metagroup = agno / EXT4_DESC_PER_BLOCK(sb);
320         int error;
321 
322         /* Record the superblock. */
323         if (ext4_bg_has_super(sb, agno)) {
324                 error = ext4_getfsmap_fill(meta_list, fsb, 1, EXT4_FMR_OWN_FS);
325                 if (error)
326                         return error;
327                 fsb++;
328         }
329 
330         /* Record the group descriptors. */
331         len = ext4_bg_num_gdb(sb, agno);
332         if (!len)
333                 return 0;
334         error = ext4_getfsmap_fill(meta_list, fsb, len,
335                                    EXT4_FMR_OWN_GDT);
336         if (error)
337                 return error;
338         fsb += len;
339 
340         /* Reserved GDT blocks */
341         if (!ext4_has_feature_meta_bg(sb) || metagroup < first_meta_bg) {
342                 len = le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
343                 error = ext4_getfsmap_fill(meta_list, fsb, len,
344                                            EXT4_FMR_OWN_RESV_GDT);
345                 if (error)
346                         return error;
347         }
348 
349         return 0;
350 }
351 
352 /* Compare two fsmap items. */
353 static int ext4_getfsmap_compare(void *priv,
354                                  struct list_head *a,
355                                  struct list_head *b)
356 {
357         struct ext4_fsmap *fa;
358         struct ext4_fsmap *fb;
359 
360         fa = container_of(a, struct ext4_fsmap, fmr_list);
361         fb = container_of(b, struct ext4_fsmap, fmr_list);
362         if (fa->fmr_physical < fb->fmr_physical)
363                 return -1;
364         else if (fa->fmr_physical > fb->fmr_physical)
365                 return 1;
366         return 0;
367 }
368 
369 /* Merge adjacent extents of fixed metadata. */
370 static void ext4_getfsmap_merge_fixed_metadata(struct list_head *meta_list)
371 {
372         struct ext4_fsmap *p;
373         struct ext4_fsmap *prev = NULL;
374         struct ext4_fsmap *tmp;
375 
376         list_for_each_entry_safe(p, tmp, meta_list, fmr_list) {
377                 if (!prev) {
378                         prev = p;
379                         continue;
380                 }
381 
382                 if (prev->fmr_owner == p->fmr_owner &&
383                     prev->fmr_physical + prev->fmr_length == p->fmr_physical) {
384                         prev->fmr_length += p->fmr_length;
385                         list_del(&p->fmr_list);
386                         kfree(p);
387                 } else
388                         prev = p;
389         }
390 }
391 
392 /* Free a list of fixed metadata. */
393 static void ext4_getfsmap_free_fixed_metadata(struct list_head *meta_list)
394 {
395         struct ext4_fsmap *p;
396         struct ext4_fsmap *tmp;
397 
398         list_for_each_entry_safe(p, tmp, meta_list, fmr_list) {
399                 list_del(&p->fmr_list);
400                 kfree(p);
401         }
402 }
403 
404 /* Find all the fixed metadata in the filesystem. */
405 static int ext4_getfsmap_find_fixed_metadata(struct super_block *sb,
406                                              struct list_head *meta_list)
407 {
408         struct ext4_group_desc *gdp;
409         ext4_group_t agno;
410         int error;
411 
412         INIT_LIST_HEAD(meta_list);
413 
414         /* Collect everything. */
415         for (agno = 0; agno < EXT4_SB(sb)->s_groups_count; agno++) {
416                 gdp = ext4_get_group_desc(sb, agno, NULL);
417                 if (!gdp) {
418                         error = -EFSCORRUPTED;
419                         goto err;
420                 }
421 
422                 /* Superblock & GDT */
423                 error = ext4_getfsmap_find_sb(sb, agno, meta_list);
424                 if (error)
425                         goto err;
426 
427                 /* Block bitmap */
428                 error = ext4_getfsmap_fill(meta_list,
429                                            ext4_block_bitmap(sb, gdp), 1,
430                                            EXT4_FMR_OWN_BLKBM);
431                 if (error)
432                         goto err;
433 
434                 /* Inode bitmap */
435                 error = ext4_getfsmap_fill(meta_list,
436                                            ext4_inode_bitmap(sb, gdp), 1,
437                                            EXT4_FMR_OWN_INOBM);
438                 if (error)
439                         goto err;
440 
441                 /* Inodes */
442                 error = ext4_getfsmap_fill(meta_list,
443                                            ext4_inode_table(sb, gdp),
444                                            EXT4_SB(sb)->s_itb_per_group,
445                                            EXT4_FMR_OWN_INODES);
446                 if (error)
447                         goto err;
448         }
449 
450         /* Sort the list */
451         list_sort(NULL, meta_list, ext4_getfsmap_compare);
452 
453         /* Merge adjacent extents */
454         ext4_getfsmap_merge_fixed_metadata(meta_list);
455 
456         return 0;
457 err:
458         ext4_getfsmap_free_fixed_metadata(meta_list);
459         return error;
460 }
461 
462 /* Execute a getfsmap query against the buddy bitmaps */
463 static int ext4_getfsmap_datadev(struct super_block *sb,
464                                  struct ext4_fsmap *keys,
465                                  struct ext4_getfsmap_info *info)
466 {
467         struct ext4_sb_info *sbi = EXT4_SB(sb);
468         ext4_fsblk_t start_fsb;
469         ext4_fsblk_t end_fsb;
470         ext4_fsblk_t bofs;
471         ext4_fsblk_t eofs;
472         ext4_group_t start_ag;
473         ext4_group_t end_ag;
474         ext4_grpblk_t first_cluster;
475         ext4_grpblk_t last_cluster;
476         int error = 0;
477 
478         bofs = le32_to_cpu(sbi->s_es->s_first_data_block);
479         eofs = ext4_blocks_count(sbi->s_es);
480         if (keys[0].fmr_physical >= eofs)
481                 return 0;
482         else if (keys[0].fmr_physical < bofs)
483                 keys[0].fmr_physical = bofs;
484         if (keys[1].fmr_physical >= eofs)
485                 keys[1].fmr_physical = eofs - 1;
486         start_fsb = keys[0].fmr_physical;
487         end_fsb = keys[1].fmr_physical;
488 
489         /* Determine first and last group to examine based on start and end */
490         ext4_get_group_no_and_offset(sb, start_fsb, &start_ag, &first_cluster);
491         ext4_get_group_no_and_offset(sb, end_fsb, &end_ag, &last_cluster);
492 
493         /*
494          * Convert the fsmap low/high keys to bg based keys.  Initialize
495          * low to the fsmap low key and max out the high key to the end
496          * of the bg.
497          */
498         info->gfi_low = keys[0];
499         info->gfi_low.fmr_physical = EXT4_C2B(sbi, first_cluster);
500         info->gfi_low.fmr_length = 0;
501 
502         memset(&info->gfi_high, 0xFF, sizeof(info->gfi_high));
503 
504         /* Assemble a list of all the fixed-location metadata. */
505         error = ext4_getfsmap_find_fixed_metadata(sb, &info->gfi_meta_list);
506         if (error)
507                 goto err;
508 
509         /* Query each bg */
510         for (info->gfi_agno = start_ag;
511              info->gfi_agno <= end_ag;
512              info->gfi_agno++) {
513                 /*
514                  * Set the bg high key from the fsmap high key if this
515                  * is the last bg that we're querying.
516                  */
517                 if (info->gfi_agno == end_ag) {
518                         info->gfi_high = keys[1];
519                         info->gfi_high.fmr_physical = EXT4_C2B(sbi,
520                                         last_cluster);
521                         info->gfi_high.fmr_length = 0;
522                 }
523 
524                 trace_ext4_fsmap_low_key(sb, info->gfi_dev, info->gfi_agno,
525                                 info->gfi_low.fmr_physical,
526                                 info->gfi_low.fmr_length,
527                                 info->gfi_low.fmr_owner);
528 
529                 trace_ext4_fsmap_high_key(sb, info->gfi_dev, info->gfi_agno,
530                                 info->gfi_high.fmr_physical,
531                                 info->gfi_high.fmr_length,
532                                 info->gfi_high.fmr_owner);
533 
534                 error = ext4_mballoc_query_range(sb, info->gfi_agno,
535                                 EXT4_B2C(sbi, info->gfi_low.fmr_physical),
536                                 EXT4_B2C(sbi, info->gfi_high.fmr_physical),
537                                 ext4_getfsmap_datadev_helper, info);
538                 if (error)
539                         goto err;
540 
541                 /*
542                  * Set the bg low key to the start of the bg prior to
543                  * moving on to the next bg.
544                  */
545                 if (info->gfi_agno == start_ag)
546                         memset(&info->gfi_low, 0, sizeof(info->gfi_low));
547         }
548 
549         /* Do we have a retained free extent? */
550         if (info->gfi_lastfree.fmr_owner) {
551                 error = ext4_getfsmap_helper(sb, info, &info->gfi_lastfree);
552                 if (error)
553                         goto err;
554         }
555 
556         /* Report any gaps at the end of the bg */
557         info->gfi_last = true;
558         error = ext4_getfsmap_datadev_helper(sb, end_ag, last_cluster, 0, info);
559         if (error)
560                 goto err;
561 
562 err:
563         ext4_getfsmap_free_fixed_metadata(&info->gfi_meta_list);
564         return error;
565 }
566 
567 /* Do we recognize the device? */
568 static bool ext4_getfsmap_is_valid_device(struct super_block *sb,
569                                           struct ext4_fsmap *fm)
570 {
571         if (fm->fmr_device == 0 || fm->fmr_device == UINT_MAX ||
572             fm->fmr_device == new_encode_dev(sb->s_bdev->bd_dev))
573                 return true;
574         if (EXT4_SB(sb)->journal_bdev &&
575             fm->fmr_device == new_encode_dev(EXT4_SB(sb)->journal_bdev->bd_dev))
576                 return true;
577         return false;
578 }
579 
580 /* Ensure that the low key is less than the high key. */
581 static bool ext4_getfsmap_check_keys(struct ext4_fsmap *low_key,
582                                      struct ext4_fsmap *high_key)
583 {
584         if (low_key->fmr_device > high_key->fmr_device)
585                 return false;
586         if (low_key->fmr_device < high_key->fmr_device)
587                 return true;
588 
589         if (low_key->fmr_physical > high_key->fmr_physical)
590                 return false;
591         if (low_key->fmr_physical < high_key->fmr_physical)
592                 return true;
593 
594         if (low_key->fmr_owner > high_key->fmr_owner)
595                 return false;
596         if (low_key->fmr_owner < high_key->fmr_owner)
597                 return true;
598 
599         return false;
600 }
601 
602 #define EXT4_GETFSMAP_DEVS      2
603 /*
604  * Get filesystem's extents as described in head, and format for
605  * output.  Calls formatter to fill the user's buffer until all
606  * extents are mapped, until the passed-in head->fmh_count slots have
607  * been filled, or until the formatter short-circuits the loop, if it
608  * is tracking filled-in extents on its own.
609  *
610  * Key to Confusion
611  * ----------------
612  * There are multiple levels of keys and counters at work here:
613  * _fsmap_head.fmh_keys         -- low and high fsmap keys passed in;
614  *                                 these reflect fs-wide block addrs.
615  * dkeys                        -- fmh_keys used to query each device;
616  *                                 these are fmh_keys but w/ the low key
617  *                                 bumped up by fmr_length.
618  * _getfsmap_info.gfi_next_fsblk-- next fs block we expect to see; this
619  *                                 is how we detect gaps in the fsmap
620  *                                 records and report them.
621  * _getfsmap_info.gfi_low/high  -- per-bg low/high keys computed from
622  *                                 dkeys; used to query the free space.
623  */
624 int ext4_getfsmap(struct super_block *sb, struct ext4_fsmap_head *head,
625                   ext4_fsmap_format_t formatter, void *arg)
626 {
627         struct ext4_fsmap dkeys[2];     /* per-dev keys */
628         struct ext4_getfsmap_dev handlers[EXT4_GETFSMAP_DEVS];
629         struct ext4_getfsmap_info info = { NULL };
630         int i;
631         int error = 0;
632 
633         if (head->fmh_iflags & ~FMH_IF_VALID)
634                 return -EINVAL;
635         if (!ext4_getfsmap_is_valid_device(sb, &head->fmh_keys[0]) ||
636             !ext4_getfsmap_is_valid_device(sb, &head->fmh_keys[1]))
637                 return -EINVAL;
638 
639         head->fmh_entries = 0;
640 
641         /* Set up our device handlers. */
642         memset(handlers, 0, sizeof(handlers));
643         handlers[0].gfd_dev = new_encode_dev(sb->s_bdev->bd_dev);
644         handlers[0].gfd_fn = ext4_getfsmap_datadev;
645         if (EXT4_SB(sb)->journal_bdev) {
646                 handlers[1].gfd_dev = new_encode_dev(
647                                 EXT4_SB(sb)->journal_bdev->bd_dev);
648                 handlers[1].gfd_fn = ext4_getfsmap_logdev;
649         }
650 
651         sort(handlers, EXT4_GETFSMAP_DEVS, sizeof(struct ext4_getfsmap_dev),
652                         ext4_getfsmap_dev_compare, NULL);
653 
654         /*
655          * To continue where we left off, we allow userspace to use the
656          * last mapping from a previous call as the low key of the next.
657          * This is identified by a non-zero length in the low key. We
658          * have to increment the low key in this scenario to ensure we
659          * don't return the same mapping again, and instead return the
660          * very next mapping.
661          *
662          * Bump the physical offset as there can be no other mapping for
663          * the same physical block range.
664          */
665         dkeys[0] = head->fmh_keys[0];
666         dkeys[0].fmr_physical += dkeys[0].fmr_length;
667         dkeys[0].fmr_owner = 0;
668         dkeys[0].fmr_length = 0;
669         memset(&dkeys[1], 0xFF, sizeof(struct ext4_fsmap));
670 
671         if (!ext4_getfsmap_check_keys(dkeys, &head->fmh_keys[1]))
672                 return -EINVAL;
673 
674         info.gfi_next_fsblk = head->fmh_keys[0].fmr_physical +
675                           head->fmh_keys[0].fmr_length;
676         info.gfi_formatter = formatter;
677         info.gfi_format_arg = arg;
678         info.gfi_head = head;
679 
680         /* For each device we support... */
681         for (i = 0; i < EXT4_GETFSMAP_DEVS; i++) {
682                 /* Is this device within the range the user asked for? */
683                 if (!handlers[i].gfd_fn)
684                         continue;
685                 if (head->fmh_keys[0].fmr_device > handlers[i].gfd_dev)
686                         continue;
687                 if (head->fmh_keys[1].fmr_device < handlers[i].gfd_dev)
688                         break;
689 
690                 /*
691                  * If this device number matches the high key, we have
692                  * to pass the high key to the handler to limit the
693                  * query results.  If the device number exceeds the
694                  * low key, zero out the low key so that we get
695                  * everything from the beginning.
696                  */
697                 if (handlers[i].gfd_dev == head->fmh_keys[1].fmr_device)
698                         dkeys[1] = head->fmh_keys[1];
699                 if (handlers[i].gfd_dev > head->fmh_keys[0].fmr_device)
700                         memset(&dkeys[0], 0, sizeof(struct ext4_fsmap));
701 
702                 info.gfi_dev = handlers[i].gfd_dev;
703                 info.gfi_last = false;
704                 info.gfi_agno = -1;
705                 error = handlers[i].gfd_fn(sb, dkeys, &info);
706                 if (error)
707                         break;
708                 info.gfi_next_fsblk = 0;
709         }
710 
711         head->fmh_oflags = FMH_OF_DEV_T;
712         return error;
713 }
714 

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