| blob | caade185e568da4783e55301f34bd9b81447176b |
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (C) International Business Machines Corp., 2000-2004
4 * Portions Copyright (C) Tino Reichardt, 2012
5 */
7 #include <linux/fs.h>
8 #include <linux/slab.h>
18 /*
19 * SERIALIZATION of the Block Allocation Map.
20 *
21 * the working state of the block allocation map is accessed in
22 * two directions:
23 *
24 * 1) allocation and free requests that start at the dmap
25 * level and move up through the dmap control pages (i.e.
26 * the vast majority of requests).
27 *
28 * 2) allocation requests that start at dmap control page
29 * level and work down towards the dmaps.
30 *
31 * the serialization scheme used here is as follows.
32 *
33 * requests which start at the bottom are serialized against each
34 * other through buffers and each requests holds onto its buffers
35 * as it works it way up from a single dmap to the required level
36 * of dmap control page.
37 * requests that start at the top are serialized against each other
38 * and request that start from the bottom by the multiple read/single
39 * write inode lock of the bmap inode. requests starting at the top
40 * take this lock in write mode while request starting at the bottom
41 * take the lock in read mode. a single top-down request may proceed
42 * exclusively while multiple bottoms-up requests may proceed
43 * simultaneously (under the protection of busy buffers).
44 *
45 * in addition to information found in dmaps and dmap control pages,
46 * the working state of the block allocation map also includes read/
47 * write information maintained in the bmap descriptor (i.e. total
48 * free block count, allocation group level free block counts).
49 * a single exclusive lock (BMAP_LOCK) is used to guard this information
50 * in the face of multiple-bottoms up requests.
51 * (lock ordering: IREAD_LOCK, BMAP_LOCK);
52 *
53 * accesses to the persistent state of the block allocation map (limited
54 * to the persistent bitmaps in dmaps) is guarded by (busy) buffers.
55 */
57 #define BMAP_LOCK_INIT(bmp) mutex_init(&bmp->db_bmaplock)
58 #define BMAP_LOCK(bmp) mutex_lock(&bmp->db_bmaplock)
59 #define BMAP_UNLOCK(bmp) mutex_unlock(&bmp->db_bmaplock)
61 /*
62 * forward references
63 */
109 /*
110 * buddy table
111 *
112 * table used for determining buddy sizes within characters of
113 * dmap bitmap words. the characters themselves serve as indexes
114 * into the table, with the table elements yielding the maximum
115 * binary buddy of free bits within the character.
116 */
134 };
136 /*
137 * NAME: dbMount()
138 *
139 * FUNCTION: initializate the block allocation map.
140 *
141 * memory is allocated for the in-core bmap descriptor and
142 * the in-core descriptor is initialized from disk.
143 *
144 * PARAMETERS:
145 * ipbmap - pointer to in-core inode for the block map.
146 *
147 * RETURN VALUES:
148 * 0 - success
149 * -ENOMEM - insufficient memory
150 * -EIO - i/o error
151 */
153 {
159 /*
160 * allocate/initialize the in-memory bmap descriptor
161 */
162 /* allocate memory for the in-memory bmap descriptor */
167 /* read the on-disk bmap descriptor. */
174 }
176 /* copy the on-disk bmap descriptor to its in-memory version. */
195 /* release the buffer. */
198 /* bind the bmap inode and the bmap descriptor to each other. */
204 /*
205 * allocate/initialize the bmap lock
206 */
210 }
213 /*
214 * NAME: dbUnmount()
215 *
216 * FUNCTION: terminate the block allocation map in preparation for
217 * file system unmount.
218 *
219 * the in-core bmap descriptor is written to disk and
220 * the memory for this descriptor is freed.
221 *
222 * PARAMETERS:
223 * ipbmap - pointer to in-core inode for the block map.
224 *
225 * RETURN VALUES:
226 * 0 - success
227 * -EIO - i/o error
228 */
230 {
236 /*
237 * Invalidate the page cache buffers
238 */
241 /* free the memory for the in-memory bmap. */
245 }
247 /*
248 * dbSync()
249 */
251 {
257 /*
258 * write bmap global control page
259 */
260 /* get the buffer for the on-disk bmap descriptor. */
267 }
268 /* copy the in-memory version of the bmap to the on-disk version */
287 /* write the buffer */
290 /*
291 * write out dirty pages of bmap
292 */
298 }
300 /*
301 * NAME: dbFree()
302 *
303 * FUNCTION: free the specified block range from the working block
304 * allocation map.
305 *
306 * the blocks will be free from the working map one dmap
307 * at a time.
308 *
309 * PARAMETERS:
310 * ip - pointer to in-core inode;
311 * blkno - starting block number to be freed.
312 * nblocks - number of blocks to be freed.
313 *
314 * RETURN VALUES:
315 * 0 - success
316 * -EIO - i/o error
317 */
319 {
330 /* block to be freed better be within the mapsize. */
338 }
340 /**
341 * TRIM the blocks, when mounted with discard option
342 */
347 /*
348 * free the blocks a dmap at a time.
349 */
352 /* release previous dmap if any */
355 }
357 /* get the buffer for the current dmap. */
363 }
366 /* determine the number of blocks to be freed from
367 * this dmap.
368 */
371 /* free the blocks. */
377 }
378 }
380 /* write the last buffer. */
386 }
389 /*
390 * NAME: dbUpdatePMap()
391 *
392 * FUNCTION: update the allocation state (free or allocate) of the
393 * specified block range in the persistent block allocation map.
394 *
395 * the blocks will be updated in the persistent map one
396 * dmap at a time.
397 *
398 * PARAMETERS:
399 * ipbmap - pointer to in-core inode for the block map.
400 * free - 'true' if block range is to be freed from the persistent
401 * map; 'false' if it is to be allocated.
402 * blkno - starting block number of the range.
403 * nblocks - number of contiguous blocks in the range.
404 * tblk - transaction block;
405 *
406 * RETURN VALUES:
407 * 0 - success
408 * -EIO - i/o error
409 */
410 int
413 {
418 u32 mask;
425 /* the blocks better be within the mapsize. */
432 }
434 /* compute delta of transaction lsn from log syncpt */
439 /*
440 * update the block state a dmap at a time.
441 */
445 /* get the buffer for the current dmap. */
450 }
457 }
460 /* determine the bit number and word within the dmap of
461 * the starting block. also determine how many blocks
462 * are to be updated within this dmap.
463 */
468 /* update the bits of the dmap words. the first and last
469 * words may only have a subset of their bits updated. if
470 * this is the case, we'll work against that word (i.e.
471 * partial first and/or last) only in a single pass. a
472 * single pass will also be used to update all words that
473 * are to have all their bits updated.
474 */
477 /* determine the bit number within the word and
478 * the number of bits within the word.
479 */
483 /* check if only part of the word is to be updated. */
485 /* update (free or allocate) the bits
486 * in this word.
487 */
488 mask =
493 else
499 /* one or more words are to have all
500 * their bits updated. determine how
501 * many words and how many bits.
502 */
506 /* update (free or allocate) the bits
507 * in these words.
508 */
512 else
517 }
518 }
520 /*
521 * update dmap lsn
522 */
530 /* inherit older/smaller lsn */
535 /* move bp after tblock in logsync list */
537 }
539 /* inherit younger/larger clsn */
548 /* insert bp after tblock in logsync list */
553 }
555 }
557 /* write the last buffer. */
560 }
563 }
566 /*
567 * NAME: dbNextAG()
568 *
569 * FUNCTION: find the preferred allocation group for new allocations.
570 *
571 * Within the allocation groups, we maintain a preferred
572 * allocation group which consists of a group with at least
573 * average free space. It is the preferred group that we target
574 * new inode allocation towards. The tie-in between inode
575 * allocation and block allocation occurs as we allocate the
576 * first (data) block of an inode and specify the inode (block)
577 * as the allocation hint for this block.
578 *
579 * We try to avoid having more than one open file growing in
580 * an allocation group, as this will lead to fragmentation.
581 * This differs from the old OS/2 method of trying to keep
582 * empty ags around for large allocations.
583 *
584 * PARAMETERS:
585 * ipbmap - pointer to in-core inode for the block map.
586 *
587 * RETURN VALUES:
588 * the preferred allocation group number.
589 */
591 {
592 s64 avgfree;
601 /* determine the average number of free blocks within the ags. */
604 /*
605 * if the current preferred ag does not have an active allocator
606 * and has at least average freespace, return it
607 */
613 /* From the last preferred ag, find the next one with at least
614 * average free space.
615 */
621 /* open file is currently growing in this ag */
624 /* Return this one */
628 /* Less than avg. freespace, but best so far */
631 }
632 }
634 /*
635 * If no inactive ag was found with average freespace, use the
636 * next best
637 */
640 /* else leave db_agpref unchanged */
641 unlock:
644 /* return the preferred group.
645 */
647 }
649 /*
650 * NAME: dbAlloc()
651 *
652 * FUNCTION: attempt to allocate a specified number of contiguous free
653 * blocks from the working allocation block map.
654 *
655 * the block allocation policy uses hints and a multi-step
656 * approach.
657 *
658 * for allocation requests smaller than the number of blocks
659 * per dmap, we first try to allocate the new blocks
660 * immediately following the hint. if these blocks are not
661 * available, we try to allocate blocks near the hint. if
662 * no blocks near the hint are available, we next try to
663 * allocate within the same dmap as contains the hint.
664 *
665 * if no blocks are available in the dmap or the allocation
666 * request is larger than the dmap size, we try to allocate
667 * within the same allocation group as contains the hint. if
668 * this does not succeed, we finally try to allocate anywhere
669 * within the aggregate.
670 *
671 * we also try to allocate anywhere within the aggregate for
672 * for allocation requests larger than the allocation group
673 * size or requests that specify no hint value.
674 *
675 * PARAMETERS:
676 * ip - pointer to in-core inode;
677 * hint - allocation hint.
678 * nblocks - number of contiguous blocks in the range.
679 * results - on successful return, set to the starting block number
680 * of the newly allocated contiguous range.
681 *
682 * RETURN VALUES:
683 * 0 - success
684 * -ENOSPC - insufficient disk resources
685 * -EIO - i/o error
686 */
688 {
696 s64 mapSize;
699 /* assert that nblocks is valid */
702 /* get the log2 number of blocks to be allocated.
703 * if the number of blocks is not a log2 multiple,
704 * it will be rounded up to the next log2 multiple.
705 */
712 /* the hint should be within the map */
716 }
718 /* if the number of blocks to be allocated is greater than the
719 * allocation group size, try to allocate anywhere.
720 */
727 }
729 /*
730 * If no hint, let dbNextAG recommend an allocation group
731 */
735 /* we would like to allocate close to the hint. adjust the
736 * hint to the block following the hint since the allocators
737 * will start looking for free space starting at this point.
738 */
746 /* check if blkno crosses over into a new allocation group.
747 * if so, check if we should allow allocations within this
748 * allocation group.
749 */
751 /* check if the AG is currently being written to.
752 * if so, call dbNextAG() to find a non-busy
753 * AG with sufficient free space.
754 */
758 /* check if the allocation request size can be satisfied from a
759 * single dmap. if so, try to allocate from the dmap containing
760 * the hint using a tiered strategy.
761 */
765 /* get the buffer for the dmap containing the hint.
766 */
775 /* first, try to satisfy the allocation request with the
776 * blocks beginning at the hint.
777 */
783 }
787 }
792 /*
793 * Someone else is writing in this allocation
794 * group. To avoid fragmenting, try another ag
795 */
799 }
801 /* next, try to satisfy the allocation request with blocks
802 * near the hint.
803 */
812 }
814 /* try to satisfy the allocation request with blocks within
815 * the same dmap as the hint.
816 */
824 }
828 }
830 /* try to satisfy the allocation request with blocks within
831 * the same allocation group as the hint.
832 */
840 pref_ag:
841 /*
842 * Let dbNextAG recommend a preferred allocation group
843 */
847 /* Try to allocate within this allocation group. if that fails, try to
848 * allocate anywhere in the map.
849 */
853 write_unlock:
858 read_unlock:
862 }
864 #ifdef _NOTYET
865 /*
866 * NAME: dbAllocExact()
867 *
868 * FUNCTION: try to allocate the requested extent;
869 *
870 * PARAMETERS:
871 * ip - pointer to in-core inode;
872 * blkno - extent address;
873 * nblocks - extent length;
874 *
875 * RETURN VALUES:
876 * 0 - success
877 * -ENOSPC - insufficient disk resources
878 * -EIO - i/o error
879 */
881 {
886 s64 lblkno;
891 /*
892 * validate extent request:
893 *
894 * note: defragfs policy:
895 * max 64 blocks will be moved.
896 * allocation request size must be satisfied from a single dmap.
897 */
901 }
904 /* the free space is no longer available */
907 }
909 /* read in the dmap covering the extent */
915 }
918 /* try to allocate the requested extent */
929 }
932 /*
933 * NAME: dbReAlloc()
934 *
935 * FUNCTION: attempt to extend a current allocation by a specified
936 * number of blocks.
937 *
938 * this routine attempts to satisfy the allocation request
939 * by first trying to extend the existing allocation in
940 * place by allocating the additional blocks as the blocks
941 * immediately following the current allocation. if these
942 * blocks are not available, this routine will attempt to
943 * allocate a new set of contiguous blocks large enough
944 * to cover the existing allocation plus the additional
945 * number of blocks required.
946 *
947 * PARAMETERS:
948 * ip - pointer to in-core inode requiring allocation.
949 * blkno - starting block of the current allocation.
950 * nblocks - number of contiguous blocks within the current
951 * allocation.
952 * addnblocks - number of blocks to add to the allocation.
953 * results - on successful return, set to the starting block number
954 * of the existing allocation if the existing allocation
955 * was extended in place or to a newly allocated contiguous
956 * range if the existing allocation could not be extended
957 * in place.
958 *
959 * RETURN VALUES:
960 * 0 - success
961 * -ENOSPC - insufficient disk resources
962 * -EIO - i/o error
963 */
964 int
967 {
970 /* try to extend the allocation in place.
971 */
978 }
980 /* could not extend the allocation in place, so allocate a
981 * new set of blocks for the entire request (i.e. try to get
982 * a range of contiguous blocks large enough to cover the
983 * existing allocation plus the additional blocks.)
984 */
987 }
990 /*
991 * NAME: dbExtend()
992 *
993 * FUNCTION: attempt to extend a current allocation by a specified
994 * number of blocks.
995 *
996 * this routine attempts to satisfy the allocation request
997 * by first trying to extend the existing allocation in
998 * place by allocating the additional blocks as the blocks
999 * immediately following the current allocation.
1000 *
1001 * PARAMETERS:
1002 * ip - pointer to in-core inode requiring allocation.
1003 * blkno - starting block of the current allocation.
1004 * nblocks - number of contiguous blocks within the current
1005 * allocation.
1006 * addnblocks - number of blocks to add to the allocation.
1007 *
1008 * RETURN VALUES:
1009 * 0 - success
1010 * -ENOSPC - insufficient disk resources
1011 * -EIO - i/o error
1012 */
1014 {
1017 uint rel_block;
1024 /*
1025 * We don't want a non-aligned extent to cross a page boundary
1026 */
1031 /* get the last block of the current allocation */
1034 /* determine the block number of the block following
1035 * the existing allocation.
1036 */
1041 /* better be within the file system */
1047 }
1049 /* we'll attempt to extend the current allocation in place by
1050 * allocating the additional blocks as the blocks immediately
1051 * following the current allocation. we only try to extend the
1052 * current allocation in place if the number of additional blocks
1053 * can fit into a dmap, the last block of the current allocation
1054 * is not the last block of the file system, and the start of the
1055 * inplace extension is not on an allocation group boundary.
1056 */
1061 }
1063 /* get the buffer for the dmap containing the first block
1064 * of the extension.
1065 */
1071 }
1075 /* try to allocate the blocks immediately following the
1076 * current allocation.
1077 */
1082 /* were we successful ? */
1085 else
1086 /* we were not successful */
1090 }
1093 /*
1094 * NAME: dbAllocNext()
1095 *
1096 * FUNCTION: attempt to allocate the blocks of the specified block
1097 * range within a dmap.
1098 *
1099 * PARAMETERS:
1100 * bmp - pointer to bmap descriptor
1101 * dp - pointer to dmap.
1102 * blkno - starting block number of the range.
1103 * nblocks - number of contiguous free blocks of the range.
1104 *
1105 * RETURN VALUES:
1106 * 0 - success
1107 * -ENOSPC - insufficient disk resources
1108 * -EIO - i/o error
1109 *
1110 * serialization: IREAD_LOCK(ipbmap) held on entry/exit;
1111 */
1114 {
1118 u32 mask;
1123 }
1125 /* pick up a pointer to the leaves of the dmap tree.
1126 */
1129 /* determine the bit number and word within the dmap of the
1130 * starting block.
1131 */
1135 /* check if the specified block range is contained within
1136 * this dmap.
1137 */
1141 /* check if the starting leaf indicates that anything
1142 * is free.
1143 */
1147 /* check the dmaps words corresponding to block range to see
1148 * if the block range is free. not all bits of the first and
1149 * last words may be contained within the block range. if this
1150 * is the case, we'll work against those words (i.e. partial first
1151 * and/or last) on an individual basis (a single pass) and examine
1152 * the actual bits to determine if they are free. a single pass
1153 * will be used for all dmap words fully contained within the
1154 * specified range. within this pass, the leaves of the dmap
1155 * tree will be examined to determine if the blocks are free. a
1156 * single leaf may describe the free space of multiple dmap
1157 * words, so we may visit only a subset of the actual leaves
1158 * corresponding to the dmap words of the block range.
1159 */
1161 /* determine the bit number within the word and
1162 * the number of bits within the word.
1163 */
1167 /* check if only part of the word is to be examined.
1168 */
1170 /* check if the bits are free.
1171 */
1178 /* one or more dmap words are fully contained
1179 * within the block range. determine how many
1180 * words and how many bits.
1181 */
1185 /* now examine the appropriate leaves to determine
1186 * if the blocks are free.
1187 */
1189 /* does the leaf describe any free space ?
1190 */
1194 /* determine the l2 number of bits provided
1195 * by this leaf.
1196 */
1197 l2size =
1200 /* determine how many words were handled.
1201 */
1206 }
1207 }
1208 }
1210 /* allocate the blocks.
1211 */
1213 }
1216 /*
1217 * NAME: dbAllocNear()
1218 *
1219 * FUNCTION: attempt to allocate a number of contiguous free blocks near
1220 * a specified block (hint) within a dmap.
1221 *
1222 * starting with the dmap leaf that covers the hint, we'll
1223 * check the next four contiguous leaves for sufficient free
1224 * space. if sufficient free space is found, we'll allocate
1225 * the desired free space.
1226 *
1227 * PARAMETERS:
1228 * bmp - pointer to bmap descriptor
1229 * dp - pointer to dmap.
1230 * blkno - block number to allocate near.
1231 * nblocks - actual number of contiguous free blocks desired.
1232 * l2nb - log2 number of contiguous free blocks desired.
1233 * results - on successful return, set to the starting block number
1234 * of the newly allocated range.
1235 *
1236 * RETURN VALUES:
1237 * 0 - success
1238 * -ENOSPC - insufficient disk resources
1239 * -EIO - i/o error
1240 *
1241 * serialization: IREAD_LOCK(ipbmap) held on entry/exit;
1242 */
1243 static int
1246 {
1253 }
1257 /* determine the word within the dmap that holds the hint
1258 * (i.e. blkno). also, determine the last word in the dmap
1259 * that we'll include in our examination.
1260 */
1264 /* examine the leaves for sufficient free space.
1265 */
1267 /* does the leaf describe sufficient free space ?
1268 */
1272 /* determine the block number within the file system
1273 * of the first block described by this dmap word.
1274 */
1277 /* if not all bits of the dmap word are free, get the
1278 * starting bit number within the dmap word of the required
1279 * string of free bits and adjust the block number with the
1280 * value.
1281 */
1283 blkno +=
1286 /* allocate the blocks.
1287 */
1292 }
1295 }
1298 /*
1299 * NAME: dbAllocAG()
1300 *
1301 * FUNCTION: attempt to allocate the specified number of contiguous
1302 * free blocks within the specified allocation group.
1303 *
1304 * unless the allocation group size is equal to the number
1305 * of blocks per dmap, the dmap control pages will be used to
1306 * find the required free space, if available. we start the
1307 * search at the highest dmap control page level which
1308 * distinctly describes the allocation group's free space
1309 * (i.e. the highest level at which the allocation group's
1310 * free space is not mixed in with that of any other group).
1311 * in addition, we start the search within this level at a
1312 * height of the dmapctl dmtree at which the nodes distinctly
1313 * describe the allocation group's free space. at this height,
1314 * the allocation group's free space may be represented by 1
1315 * or two sub-trees, depending on the allocation group size.
1316 * we search the top nodes of these subtrees left to right for
1317 * sufficient free space. if sufficient free space is found,
1318 * the subtree is searched to find the leftmost leaf that
1319 * has free space. once we have made it to the leaf, we
1320 * move the search to the next lower level dmap control page
1321 * corresponding to this leaf. we continue down the dmap control
1322 * pages until we find the dmap that contains or starts the
1323 * sufficient free space and we allocate at this dmap.
1324 *
1325 * if the allocation group size is equal to the dmap size,
1326 * we'll start at the dmap corresponding to the allocation
1327 * group and attempt the allocation at this level.
1328 *
1329 * the dmap control page search is also not performed if the
1330 * allocation group is completely free and we go to the first
1331 * dmap of the allocation group to do the allocation. this is
1332 * done because the allocation group may be part (not the first
1333 * part) of a larger binary buddy system, causing the dmap
1334 * control pages to indicate no free space (NOFREE) within
1335 * the allocation group.
1336 *
1337 * PARAMETERS:
1338 * bmp - pointer to bmap descriptor
1339 * agno - allocation group number.
1340 * nblocks - actual number of contiguous free blocks desired.
1341 * l2nb - log2 number of contiguous free blocks desired.
1342 * results - on successful return, set to the starting block number
1343 * of the newly allocated range.
1344 *
1345 * RETURN VALUES:
1346 * 0 - success
1347 * -ENOSPC - insufficient disk resources
1348 * -EIO - i/o error
1349 *
1350 * note: IWRITE_LOCK(ipmap) held on entry/exit;
1351 */
1352 static int
1354 {
1361 /* allocation request should not be for more than the
1362 * allocation group size.
1363 */
1368 }
1370 /* determine the starting block number of the allocation
1371 * group.
1372 */
1375 /* check if the allocation group size is the minimum allocation
1376 * group size or if the allocation group is completely free. if
1377 * the allocation group size is the minimum size of BPERDMAP (i.e.
1378 * 1 dmap), there is no need to search the dmap control page (below)
1379 * that fully describes the allocation group since the allocation
1380 * group is already fully described by a dmap. in this case, we
1381 * just call dbAllocCtl() to search the dmap tree and allocate the
1382 * required space if available.
1383 *
1384 * if the allocation group is completely free, dbAllocCtl() is
1385 * also called to allocate the required space. this is done for
1386 * two reasons. first, it makes no sense searching the dmap control
1387 * pages for free space when we know that free space exists. second,
1388 * the dmap control pages may indicate that the allocation group
1389 * has no free space if the allocation group is part (not the first
1390 * part) of a larger binary buddy system.
1391 */
1402 }
1404 }
1406 /* the buffer for the dmap control page that fully describes the
1407 * allocation group.
1408 */
1420 }
1422 /* search the subtree(s) of the dmap control page that describes
1423 * the allocation group, looking for sufficient free space. to begin,
1424 * determine how many allocation groups are represented in a dmap
1425 * control page at the control page level (i.e. L0, L1, L2) that
1426 * fully describes an allocation group. next, determine the starting
1427 * tree index of this allocation group within the control page.
1428 */
1429 agperlev =
1433 /* dmap control page trees fan-out by 4 and a single allocation
1434 * group may be described by 1 or 2 subtrees within the ag level
1435 * dmap control page, depending upon the ag size. examine the ag's
1436 * subtrees for sufficient free space, starting with the leftmost
1437 * subtree.
1438 */
1440 /* is there sufficient free space ?
1441 */
1445 /* sufficient free space found in a subtree. now search down
1446 * the subtree to find the leftmost leaf that describes this
1447 * free space.
1448 */
1454 }
1455 }
1461 }
1462 }
1464 /* determine the block number within the file system
1465 * that corresponds to this leaf.
1466 */
1474 blkno +=
1477 /* release the buffer in preparation for going down
1478 * the next level of dmap control pages.
1479 */
1482 /* check if we need to continue to search down the lower
1483 * level dmap control pages. we need to if the number of
1484 * blocks required is less than maximum number of blocks
1485 * described at the next lower level.
1486 */
1489 /* search the lower level dmap control pages to get
1490 * the starting block number of the dmap that
1491 * contains or starts off the free space.
1492 */
1500 }
1502 }
1503 }
1505 /* allocate the blocks.
1506 */
1512 }
1514 }
1516 /* no space in the allocation group. release the buffer and
1517 * return -ENOSPC.
1518 */
1522 }
1525 /*
1526 * NAME: dbAllocAny()
1527 *
1528 * FUNCTION: attempt to allocate the specified number of contiguous
1529 * free blocks anywhere in the file system.
1530 *
1531 * dbAllocAny() attempts to find the sufficient free space by
1532 * searching down the dmap control pages, starting with the
1533 * highest level (i.e. L0, L1, L2) control page. if free space
1534 * large enough to satisfy the desired free space is found, the
1535 * desired free space is allocated.
1536 *
1537 * PARAMETERS:
1538 * bmp - pointer to bmap descriptor
1539 * nblocks - actual number of contiguous free blocks desired.
1540 * l2nb - log2 number of contiguous free blocks desired.
1541 * results - on successful return, set to the starting block number
1542 * of the newly allocated range.
1543 *
1544 * RETURN VALUES:
1545 * 0 - success
1546 * -ENOSPC - insufficient disk resources
1547 * -EIO - i/o error
1548 *
1549 * serialization: IWRITE_LOCK(ipbmap) held on entry/exit;
1550 */
1552 {
1556 /* starting with the top level dmap control page, search
1557 * down the dmap control levels for sufficient free space.
1558 * if free space is found, dbFindCtl() returns the starting
1559 * block number of the dmap that contains or starts off the
1560 * range of free space.
1561 */
1565 /* allocate the blocks.
1566 */
1571 }
1573 }
1576 /*
1577 * NAME: dbDiscardAG()
1578 *
1579 * FUNCTION: attempt to discard (TRIM) all free blocks of specific AG
1580 *
1581 * algorithm:
1582 * 1) allocate blocks, as large as possible and save them
1583 * while holding IWRITE_LOCK on ipbmap
1584 * 2) trim all these saved block/length values
1585 * 3) mark the blocks free again
1586 *
1587 * benefit:
1588 * - we work only on one ag at some time, minimizing how long we
1589 * need to lock ipbmap
1590 * - reading / writing the fs is possible most time, even on
1591 * trimming
1592 *
1593 * downside:
1594 * - we write two times to the dmapctl and dmap pages
1595 * - but for me, this seems the best way, better ideas?
1596 * /TR 2012
1597 *
1598 * PARAMETERS:
1599 * ip - pointer to in-core inode
1600 * agno - ag to trim
1601 * minlen - minimum value of contiguous blocks
1602 *
1603 * RETURN VALUES:
1604 * s64 - actual number of blocks trimmed
1605 */
1607 {
1616 u64 blkno;
1617 u64 nblocks;
1620 /* max blkno / nblocks pairs to trim */
1622 u64 max_ranges;
1624 /* prevent others from writing new stuff here, while trimming */
1636 }
1642 /* 0 = okay, -EIO = fatal, -ENOSPC -> try smaller block */
1649 /* the whole ag is free, trim now */
1653 /* give a hint for the next while */
1657 /* search for next smaller log2 block */
1661 /* Trim any already allocated blocks */
1664 }
1666 /* check, if our trim array is full */
1669 }
1674 /* when mounted with online discard, dbFree() will
1675 * call jfs_issue_discard() itself */
1680 }
1684 }
1686 /*
1687 * NAME: dbFindCtl()
1688 *
1689 * FUNCTION: starting at a specified dmap control page level and block
1690 * number, search down the dmap control levels for a range of
1691 * contiguous free blocks large enough to satisfy an allocation
1692 * request for the specified number of free blocks.
1693 *
1694 * if sufficient contiguous free blocks are found, this routine
1695 * returns the starting block number within a dmap page that
1696 * contains or starts a range of contiqious free blocks that
1697 * is sufficient in size.
1698 *
1699 * PARAMETERS:
1700 * bmp - pointer to bmap descriptor
1701 * level - starting dmap control page level.
1702 * l2nb - log2 number of contiguous free blocks desired.
1703 * *blkno - on entry, starting block number for conducting the search.
1704 * on successful return, the first block within a dmap page
1705 * that contains or starts a range of contiguous free blocks.
1706 *
1707 * RETURN VALUES:
1708 * 0 - success
1709 * -ENOSPC - insufficient disk resources
1710 * -EIO - i/o error
1711 *
1712 * serialization: IWRITE_LOCK(ipbmap) held on entry/exit;
1713 */
1715 {
1722 /* starting at the specified dmap control page level and block
1723 * number, search down the dmap control levels for the starting
1724 * block number of a dmap page that contains or starts off
1725 * sufficient free blocks.
1726 */
1728 /* get the buffer of the dmap control page for the block
1729 * number and level (i.e. L0, L1, L2).
1730 */
1743 }
1745 /* search the tree within the dmap control page for
1746 * sufficient free space. if sufficient free space is found,
1747 * dbFindLeaf() returns the index of the leaf at which
1748 * free space was found.
1749 */
1752 /* release the buffer.
1753 */
1756 /* space found ?
1757 */
1763 }
1765 }
1767 /* adjust the block number to reflect the location within
1768 * the dmap control page (i.e. the leaf) at which free
1769 * space was found.
1770 */
1773 /* we stop the search at this dmap control page level if
1774 * the number of blocks required is greater than or equal
1775 * to the maximum number of blocks described at the next
1776 * (lower) level.
1777 */
1780 }
1784 }
1787 /*
1788 * NAME: dbAllocCtl()
1789 *
1790 * FUNCTION: attempt to allocate a specified number of contiguous
1791 * blocks starting within a specific dmap.
1792 *
1793 * this routine is called by higher level routines that search
1794 * the dmap control pages above the actual dmaps for contiguous
1795 * free space. the result of successful searches by these
1796 * routines are the starting block numbers within dmaps, with
1797 * the dmaps themselves containing the desired contiguous free
1798 * space or starting a contiguous free space of desired size
1799 * that is made up of the blocks of one or more dmaps. these
1800 * calls should not fail due to insufficent resources.
1801 *
1802 * this routine is called in some cases where it is not known
1803 * whether it will fail due to insufficient resources. more
1804 * specifically, this occurs when allocating from an allocation
1805 * group whose size is equal to the number of blocks per dmap.
1806 * in this case, the dmap control pages are not examined prior
1807 * to calling this routine (to save pathlength) and the call
1808 * might fail.
1809 *
1810 * for a request size that fits within a dmap, this routine relies
1811 * upon the dmap's dmtree to find the requested contiguous free
1812 * space. for request sizes that are larger than a dmap, the
1813 * requested free space will start at the first block of the
1814 * first dmap (i.e. blkno).
1815 *
1816 * PARAMETERS:
1817 * bmp - pointer to bmap descriptor
1818 * nblocks - actual number of contiguous free blocks to allocate.
1819 * l2nb - log2 number of contiguous free blocks to allocate.
1820 * blkno - starting block number of the dmap to start the allocation
1821 * from.
1822 * results - on successful return, set to the starting block number
1823 * of the newly allocated range.
1824 *
1825 * RETURN VALUES:
1826 * 0 - success
1827 * -ENOSPC - insufficient disk resources
1828 * -EIO - i/o error
1829 *
1830 * serialization: IWRITE_LOCK(ipbmap) held on entry/exit;
1831 */
1832 static int
1834 {
1840 /* check if the allocation request is confined to a single dmap.
1841 */
1843 /* get the buffer for the dmap.
1844 */
1851 /* try to allocate the blocks.
1852 */
1860 }
1862 /* allocation request involving multiple dmaps. it must start on
1863 * a dmap boundary.
1864 */
1867 /* allocate the blocks dmap by dmap.
1868 */
1870 /* get the buffer for the dmap.
1871 */
1877 }
1880 /* the dmap better be all free.
1881 */
1888 }
1890 /* determine how many blocks to allocate from this dmap.
1891 */
1894 /* allocate the blocks from the dmap.
1895 */
1899 }
1901 /* write the buffer.
1902 */
1904 }
1906 /* set the results (starting block number) and return.
1907 */
1911 /* something failed in handling an allocation request involving
1912 * multiple dmaps. we'll try to clean up by backing out any
1913 * allocation that has already happened for this request. if
1914 * we fail in backing out the allocation, we'll mark the file
1915 * system to indicate that blocks have been leaked.
1916 */
1917 backout:
1919 /* try to backout the allocations dmap by dmap.
1920 */
1923 /* get the buffer for this dmap.
1924 */
1928 /* could not back out. mark the file system
1929 * to indicate that we have leaked blocks.
1930 */
1934 }
1937 /* free the blocks is this dmap.
1938 */
1940 /* could not back out. mark the file system
1941 * to indicate that we have leaked blocks.
1942 */
1946 }
1948 /* write the buffer.
1949 */
1951 }
1954 }
1957 /*
1958 * NAME: dbAllocDmapLev()
1959 *
1960 * FUNCTION: attempt to allocate a specified number of contiguous blocks
1961 * from a specified dmap.
1962 *
1963 * this routine checks if the contiguous blocks are available.
1964 * if so, nblocks of blocks are allocated; otherwise, ENOSPC is
1965 * returned.
1966 *
1967 * PARAMETERS:
1968 * mp - pointer to bmap descriptor
1969 * dp - pointer to dmap to attempt to allocate blocks from.
1970 * l2nb - log2 number of contiguous block desired.
1971 * nblocks - actual number of contiguous block desired.
1972 * results - on successful return, set to the starting block number
1973 * of the newly allocated range.
1974 *
1975 * RETURN VALUES:
1976 * 0 - success
1977 * -ENOSPC - insufficient disk resources
1978 * -EIO - i/o error
1979 *
1980 * serialization: IREAD_LOCK(ipbmap), e.g., from dbAlloc(), or
1981 * IWRITE_LOCK(ipbmap), e.g., dbAllocCtl(), held on entry/exit;
1982 */
1983 static int
1986 {
1987 s64 blkno;
1990 /* can't be more than a dmaps worth of blocks */
1993 /* search the tree within the dmap page for sufficient
1994 * free space. if sufficient free space is found, dbFindLeaf()
1995 * returns the index of the leaf at which free space was found.
1996 */
2000 /* determine the block number within the file system corresponding
2001 * to the leaf at which free space was found.
2002 */
2005 /* if not all bits of the dmap word are free, get the starting
2006 * bit number within the dmap word of the required string of free
2007 * bits and adjust the block number with this value.
2008 */
2012 /* allocate the blocks */
2017 }
2020 /*
2021 * NAME: dbAllocDmap()
2022 *
2023 * FUNCTION: adjust the disk allocation map to reflect the allocation
2024 * of a specified block range within a dmap.
2025 *
2026 * this routine allocates the specified blocks from the dmap
2027 * through a call to dbAllocBits(). if the allocation of the
2028 * block range causes the maximum string of free blocks within
2029 * the dmap to change (i.e. the value of the root of the dmap's
2030 * dmtree), this routine will cause this change to be reflected
2031 * up through the appropriate levels of the dmap control pages
2032 * by a call to dbAdjCtl() for the L0 dmap control page that
2033 * covers this dmap.
2034 *
2035 * PARAMETERS:
2036 * bmp - pointer to bmap descriptor
2037 * dp - pointer to dmap to allocate the block range from.
2038 * blkno - starting block number of the block to be allocated.
2039 * nblocks - number of blocks to be allocated.
2040 *
2041 * RETURN VALUES:
2042 * 0 - success
2043 * -EIO - i/o error
2044 *
2045 * serialization: IREAD_LOCK(ipbmap) or IWRITE_LOCK(ipbmap) held on entry/exit;
2046 */
2049 {
2050 s8 oldroot;
2053 /* save the current value of the root (i.e. maximum free string)
2054 * of the dmap tree.
2055 */
2058 /* allocate the specified (blocks) bits */
2061 /* if the root has not changed, done. */
2065 /* root changed. bubble the change up to the dmap control pages.
2066 * if the adjustment of the upper level control pages fails,
2067 * backout the bit allocation (thus making everything consistent).
2068 */
2073 }
2076 /*
2077 * NAME: dbFreeDmap()
2078 *
2079 * FUNCTION: adjust the disk allocation map to reflect the allocation
2080 * of a specified block range within a dmap.
2081 *
2082 * this routine frees the specified blocks from the dmap through
2083 * a call to dbFreeBits(). if the deallocation of the block range
2084 * causes the maximum string of free blocks within the dmap to
2085 * change (i.e. the value of the root of the dmap's dmtree), this
2086 * routine will cause this change to be reflected up through the
2087 * appropriate levels of the dmap control pages by a call to
2088 * dbAdjCtl() for the L0 dmap control page that covers this dmap.
2089 *
2090 * PARAMETERS:
2091 * bmp - pointer to bmap descriptor
2092 * dp - pointer to dmap to free the block range from.
2093 * blkno - starting block number of the block to be freed.
2094 * nblocks - number of blocks to be freed.
2095 *
2096 * RETURN VALUES:
2097 * 0 - success
2098 * -EIO - i/o error
2099 *
2100 * serialization: IREAD_LOCK(ipbmap) or IWRITE_LOCK(ipbmap) held on entry/exit;
2101 */
2104 {
2105 s8 oldroot;
2108 /* save the current value of the root (i.e. maximum free string)
2109 * of the dmap tree.
2110 */
2113 /* free the specified (blocks) bits */
2116 /* if error or the root has not changed, done. */
2120 /* root changed. bubble the change up to the dmap control pages.
2121 * if the adjustment of the upper level control pages fails,
2122 * backout the deallocation.
2123 */
2127 /* as part of backing out the deallocation, we will have
2128 * to back split the dmap tree if the deallocation caused
2129 * the freed blocks to become part of a larger binary buddy
2130 * system.
2131 */
2136 }
2139 }
2142 /*
2143 * NAME: dbAllocBits()
2144 *
2145 * FUNCTION: allocate a specified block range from a dmap.
2146 *
2147 * this routine updates the dmap to reflect the working
2148 * state allocation of the specified block range. it directly
2149 * updates the bits of the working map and causes the adjustment
2150 * of the binary buddy system described by the dmap's dmtree
2151 * leaves to reflect the bits allocated. it also causes the
2152 * dmap's dmtree, as a whole, to reflect the allocated range.
2153 *
2154 * PARAMETERS:
2155 * bmp - pointer to bmap descriptor
2156 * dp - pointer to dmap to allocate bits from.
2157 * blkno - starting block number of the bits to be allocated.
2158 * nblocks - number of bits to be allocated.
2159 *
2160 * RETURN VALUES: none
2161 *
2162 * serialization: IREAD_LOCK(ipbmap) or IWRITE_LOCK(ipbmap) held on entry/exit;
2163 */
2166 {
2172 /* pick up a pointer to the leaves of the dmap tree */
2175 /* determine the bit number and word within the dmap of the
2176 * starting block.
2177 */
2181 /* block range better be within the dmap */
2184 /* allocate the bits of the dmap's words corresponding to the block
2185 * range. not all bits of the first and last words may be contained
2186 * within the block range. if this is the case, we'll work against
2187 * those words (i.e. partial first and/or last) on an individual basis
2188 * (a single pass), allocating the bits of interest by hand and
2189 * updating the leaf corresponding to the dmap word. a single pass
2190 * will be used for all dmap words fully contained within the
2191 * specified range. within this pass, the bits of all fully contained
2192 * dmap words will be marked as free in a single shot and the leaves
2193 * will be updated. a single leaf may describe the free space of
2194 * multiple dmap words, so we may update only a subset of the actual
2195 * leaves corresponding to the dmap words of the block range.
2196 */
2198 /* determine the bit number within the word and
2199 * the number of bits within the word.
2200 */
2204 /* check if only part of a word is to be allocated.
2205 */
2207 /* allocate (set to 1) the appropriate bits within
2208 * this dmap word.
2209 */
2213 /* update the leaf for this dmap word. in addition
2214 * to setting the leaf value to the binary buddy max
2215 * of the updated dmap word, dbSplit() will split
2216 * the binary system of the leaves if need be.
2217 */
2223 /* one or more dmap words are fully contained
2224 * within the block range. determine how many
2225 * words and allocate (set to 1) the bits of these
2226 * words.
2227 */
2231 /* determine how many bits.
2232 */
2235 /* now update the appropriate leaves to reflect
2236 * the allocated words.
2237 */
2243 }
2245 /* determine what the leaf value should be
2246 * updated to as the minimum of the l2 number
2247 * of bits being allocated and the l2 number
2248 * of bits currently described by this leaf.
2249 */
2253 /* update the leaf to reflect the allocation.
2254 * in addition to setting the leaf value to
2255 * NOFREE, dbSplit() will split the binary
2256 * system of the leaves to reflect the current
2257 * allocation (size).
2258 */
2261 /* get the number of dmap words handled */
2264 }
2265 }
2266 }
2268 /* update the free count for this dmap */
2273 /* if this allocation group is completely free,
2274 * update the maximum allocation group number if this allocation
2275 * group is the new max.
2276 */
2281 /* update the free count for the allocation group and map */
2286 }
2289 /*
2290 * NAME: dbFreeBits()
2291 *
2292 * FUNCTION: free a specified block range from a dmap.
2293 *
2294 * this routine updates the dmap to reflect the working
2295 * state allocation of the specified block range. it directly
2296 * updates the bits of the working map and causes the adjustment
2297 * of the binary buddy system described by the dmap's dmtree
2298 * leaves to reflect the bits freed. it also causes the dmap's
2299 * dmtree, as a whole, to reflect the deallocated range.
2300 *
2301 * PARAMETERS:
2302 * bmp - pointer to bmap descriptor
2303 * dp - pointer to dmap to free bits from.
2304 * blkno - starting block number of the bits to be freed.
2305 * nblocks - number of bits to be freed.
2306 *
2307 * RETURN VALUES: 0 for success
2308 *
2309 * serialization: IREAD_LOCK(ipbmap) or IWRITE_LOCK(ipbmap) held on entry/exit;
2310 */
2313 {
2319 /* determine the bit number and word within the dmap of the
2320 * starting block.
2321 */
2325 /* block range better be within the dmap.
2326 */
2329 /* free the bits of the dmaps words corresponding to the block range.
2330 * not all bits of the first and last words may be contained within
2331 * the block range. if this is the case, we'll work against those
2332 * words (i.e. partial first and/or last) on an individual basis
2333 * (a single pass), freeing the bits of interest by hand and updating
2334 * the leaf corresponding to the dmap word. a single pass will be used
2335 * for all dmap words fully contained within the specified range.
2336 * within this pass, the bits of all fully contained dmap words will
2337 * be marked as free in a single shot and the leaves will be updated. a
2338 * single leaf may describe the free space of multiple dmap words,
2339 * so we may update only a subset of the actual leaves corresponding
2340 * to the dmap words of the block range.
2341 *
2342 * dbJoin() is used to update leaf values and will join the binary
2343 * buddy system of the leaves if the new leaf values indicate this
2344 * should be done.
2345 */
2347 /* determine the bit number within the word and
2348 * the number of bits within the word.
2349 */
2353 /* check if only part of a word is to be freed.
2354 */
2356 /* free (zero) the appropriate bits within this
2357 * dmap word.
2358 */
2363 /* update the leaf for this dmap word.
2364 */
2372 /* one or more dmap words are fully contained
2373 * within the block range. determine how many
2374 * words and free (zero) the bits of these words.
2375 */
2379 /* determine how many bits.
2380 */
2383 /* now update the appropriate leaves to reflect
2384 * the freed words.
2385 */
2387 /* determine what the leaf value should be
2388 * updated to as the minimum of the l2 number
2389 * of bits being freed and the l2 (max) number
2390 * of bits that can be described by this leaf.
2391 */
2392 size =
2397 /* update the leaf.
2398 */
2403 /* get the number of dmap words handled.
2404 */
2407 }
2408 }
2409 }
2411 /* update the free count for this dmap.
2412 */
2417 /* update the free count for the allocation group and
2418 * map.
2419 */
2424 /* check if this allocation group is not completely free and
2425 * if it is currently the maximum (rightmost) allocation group.
2426 * if so, establish the new maximum allocation group number by
2427 * searching left for the first allocation group with allocation.
2428 */
2437 }
2439 /* re-establish the allocation group preference if the
2440 * current preference is right of the maximum allocation
2441 * group.
2442 */
2445 }
2450 }
2453 /*
2454 * NAME: dbAdjCtl()
2455 *
2456 * FUNCTION: adjust a dmap control page at a specified level to reflect
2457 * the change in a lower level dmap or dmap control page's
2458 * maximum string of free blocks (i.e. a change in the root
2459 * of the lower level object's dmtree) due to the allocation
2460 * or deallocation of a range of blocks with a single dmap.
2461 *
2462 * on entry, this routine is provided with the new value of
2463 * the lower level dmap or dmap control page root and the
2464 * starting block number of the block range whose allocation
2465 * or deallocation resulted in the root change. this range
2466 * is respresented by a single leaf of the current dmapctl
2467 * and the leaf will be updated with this value, possibly
2468 * causing a binary buddy system within the leaves to be
2469 * split or joined. the update may also cause the dmapctl's
2470 * dmtree to be updated.
2471 *
2472 * if the adjustment of the dmap control page, itself, causes its
2473 * root to change, this change will be bubbled up to the next dmap
2474 * control level by a recursive call to this routine, specifying
2475 * the new root value and the next dmap control page level to
2476 * be adjusted.
2477 * PARAMETERS:
2478 * bmp - pointer to bmap descriptor
2479 * blkno - the first block of a block range within a dmap. it is
2480 * the allocation or deallocation of this block range that
2481 * requires the dmap control page to be adjusted.
2482 * newval - the new value of the lower level dmap or dmap control
2483 * page root.
2484 * alloc - 'true' if adjustment is due to an allocation.
2485 * level - current level of dmap control page (i.e. L0, L1, L2) to
2486 * be adjusted.
2487 *
2488 * RETURN VALUES:
2489 * 0 - success
2490 * -EIO - i/o error
2491 *
2492 * serialization: IREAD_LOCK(ipbmap) or IWRITE_LOCK(ipbmap) held on entry/exit;
2493 */
2494 static int
2496 {
2498 s8 oldroot;
2500 s64 lblkno;
2504 /* get the buffer for the dmap control page for the specified
2505 * block number and control page level.
2506 */
2517 }
2519 /* determine the leaf number corresponding to the block and
2520 * the index within the dmap control tree.
2521 */
2525 /* save the current leaf value and the current root level (i.e.
2526 * maximum l2 free string described by this dmapctl).
2527 */
2531 /* check if this is a control page update for an allocation.
2532 * if so, update the leaf to reflect the new leaf value using
2533 * dbSplit(); otherwise (deallocation), use dbJoin() to update
2534 * the leaf with the new value. in addition to updating the
2535 * leaf, dbSplit() will also split the binary buddy system of
2536 * the leaves, if required, and bubble new values within the
2537 * dmapctl tree, if required. similarly, dbJoin() will join
2538 * the binary buddy system of leaves and bubble new values up
2539 * the dmapctl tree as required by the new leaf value.
2540 */
2542 /* check if we are in the middle of a binary buddy
2543 * system. this happens when we are performing the
2544 * first allocation out of an allocation group that
2545 * is part (not the first part) of a larger binary
2546 * buddy system. if we are in the middle, back split
2547 * the system prior to calling dbSplit() which assumes
2548 * that it is at the front of a binary buddy system.
2549 */
2555 }
2561 }
2563 /* check if the root of the current dmap control page changed due
2564 * to the update and if the current dmap control page is not at
2565 * the current top level (i.e. L0, L1, L2) of the map. if so (i.e.
2566 * root changed and this is not the top level), call this routine
2567 * again (recursion) for the next higher level of the mapping to
2568 * reflect the change in root for the current dmap control page.
2569 */
2571 /* are we below the top level of the map. if so,
2572 * bubble the root up to the next higher level.
2573 */
2575 /* bubble up the new root of this dmap control page to
2576 * the next level.
2577 */
2581 /* something went wrong in bubbling up the new
2582 * root value, so backout the changes to the
2583 * current dmap control page.
2584 */
2587 oldval);
2589 /* the dbJoin() above might have
2590 * caused a larger binary buddy system
2591 * to form and we may now be in the
2592 * middle of it. if this is the case,
2593 * back split the buddies.
2594 */
2600 }
2602 /* release the buffer and return the error.
2603 */
2606 }
2608 /* we're at the top level of the map. update
2609 * the bmap control page to reflect the size
2610 * of the maximum free buddy system.
2611 */
2616 }
2618 }
2619 }
2621 /* write the buffer.
2622 */
2626 }
2629 /*
2630 * NAME: dbSplit()
2631 *
2632 * FUNCTION: update the leaf of a dmtree with a new value, splitting
2633 * the leaf from the binary buddy system of the dmtree's
2634 * leaves, as required.
2635 *
2636 * PARAMETERS:
2637 * tp - pointer to the tree containing the leaf.
2638 * leafno - the number of the leaf to be updated.
2639 * splitsz - the size the binary buddy system starting at the leaf
2640 * must be split to, specified as the log2 number of blocks.
2641 * newval - the new value for the leaf.
2642 *
2643 * RETURN VALUES: none
2644 *
2645 * serialization: IREAD_LOCK(ipbmap) or IWRITE_LOCK(ipbmap) held on entry/exit;
2646 */
2648 {
2653 /* check if the leaf needs to be split.
2654 */
2656 /* the split occurs by cutting the buddy system in half
2657 * at the specified leaf until we reach the specified
2658 * size. pick up the starting split size (current size
2659 * - 1 in l2) and the corresponding buddy size.
2660 */
2664 /* split until we reach the specified size.
2665 */
2667 /* update the buddy's leaf with its new value.
2668 */
2671 /* on to the next size and buddy.
2672 */
2675 }
2676 }
2678 /* adjust the dmap tree to reflect the specified leaf's new
2679 * value.
2680 */
2682 }
2685 /*
2686 * NAME: dbBackSplit()
2687 *
2688 * FUNCTION: back split the binary buddy system of dmtree leaves
2689 * that hold a specified leaf until the specified leaf
2690 * starts its own binary buddy system.
2691 *
2692 * the allocators typically perform allocations at the start
2693 * of binary buddy systems and dbSplit() is used to accomplish
2694 * any required splits. in some cases, however, allocation
2695 * may occur in the middle of a binary system and requires a
2696 * back split, with the split proceeding out from the middle of
2697 * the system (less efficient) rather than the start of the
2698 * system (more efficient). the cases in which a back split
2699 * is required are rare and are limited to the first allocation
2700 * within an allocation group which is a part (not first part)
2701 * of a larger binary buddy system and a few exception cases
2702 * in which a previous join operation must be backed out.
2703 *
2704 * PARAMETERS:
2705 * tp - pointer to the tree containing the leaf.
2706 * leafno - the number of the leaf to be updated.
2707 *
2708 * RETURN VALUES: none
2709 *
2710 * serialization: IREAD_LOCK(ipbmap) or IWRITE_LOCK(ipbmap) held on entry/exit;
2711 */
2713 {
2718 /* leaf should be part (not first part) of a binary
2719 * buddy system.
2720 */
2723 /* the back split is accomplished by iteratively finding the leaf
2724 * that starts the buddy system that contains the specified leaf and
2725 * splitting that system in two. this iteration continues until
2726 * the specified leaf becomes the start of a buddy system.
2727 *
2728 * determine maximum possible l2 size for the specified leaf.
2729 */
2730 size =
2734 /* determine the number of leaves covered by this size. this
2735 * is the buddy size that we will start with as we search for
2736 * the buddy system that contains the specified leaf.
2737 */
2740 /* back split.
2741 */
2743 /* find the leftmost buddy leaf.
2744 */
2750 }
2752 /* determine the buddy.
2753 */
2756 /* check if this buddy is the start of the system.
2757 */
2759 /* split the leaf at the start of the
2760 * system in two.
2761 */
2765 }
2766 }
2767 }
2772 }
2774 }
2777 /*
2778 * NAME: dbJoin()
2779 *
2780 * FUNCTION: update the leaf of a dmtree with a new value, joining
2781 * the leaf with other leaves of the dmtree into a multi-leaf
2782 * binary buddy system, as required.
2783 *
2784 * PARAMETERS:
2785 * tp - pointer to the tree containing the leaf.
2786 * leafno - the number of the leaf to be updated.
2787 * newval - the new value for the leaf.
2788 *
2789 * RETURN VALUES: none
2790 */
2792 {
2796 /* can the new leaf value require a join with other leaves ?
2797 */
2799 /* pickup a pointer to the leaves of the tree.
2800 */
2803 /* try to join the specified leaf into a large binary
2804 * buddy system. the join proceeds by attempting to join
2805 * the specified leafno with its buddy (leaf) at new value.
2806 * if the join occurs, we attempt to join the left leaf
2807 * of the joined buddies with its buddy at new value + 1.
2808 * we continue to join until we find a buddy that cannot be
2809 * joined (does not have a value equal to the size of the
2810 * last join) or until all leaves have been joined into a
2811 * single system.
2812 *
2813 * get the buddy size (number of words covered) of
2814 * the new value.
2815 */
2818 /* try to join.
2819 */
2821 /* get the buddy leaf.
2822 */
2825 /* if the leaf's new value is greater than its
2826 * buddy's value, we join no more.
2827 */
2831 /* It shouldn't be less */
2835 /* check which (leafno or buddy) is the left buddy.
2836 * the left buddy gets to claim the blocks resulting
2837 * from the join while the right gets to claim none.
2838 * the left buddy is also eligible to participate in
2839 * a join at the next higher level while the right
2840 * is not.
2841 *
2842 */
2844 /* leafno is the left buddy.
2845 */
2848 /* buddy is the left buddy and becomes
2849 * leafno.
2850 */
2853 }
2855 /* on to try the next join.
2856 */
2859 }
2860 }
2862 /* update the leaf value.
2863 */
2867 }
2870 /*
2871 * NAME: dbAdjTree()
2872 *
2873 * FUNCTION: update a leaf of a dmtree with a new value, adjusting
2874 * the dmtree, as required, to reflect the new leaf value.
2875 * the combination of any buddies must already be done before
2876 * this is called.
2877 *
2878 * PARAMETERS:
2879 * tp - pointer to the tree to be adjusted.
2880 * leafno - the number of the leaf to be updated.
2881 * newval - the new value for the leaf.
2882 *
2883 * RETURN VALUES: none
2884 */
2886 {
2890 /* pick up the index of the leaf for this leafno.
2891 */
2894 /* is the current value the same as the old value ? if so,
2895 * there is nothing to do.
2896 */
2900 /* set the new value.
2901 */
2904 /* bubble the new value up the tree as required.
2905 */
2907 /* get the index of the first leaf of the 4 leaf
2908 * group containing the specified leaf (leafno).
2909 */
2912 /* get the index of the parent of this 4 leaf group.
2913 */
2916 /* determine the maximum of the 4 leaves.
2917 */
2920 /* if the maximum of the 4 is the same as the
2921 * parent's value, we're done.
2922 */
2926 /* parent gets new value.
2927 */
2930 /* parent becomes leaf for next go-round.
2931 */
2933 }
2934 }
2937 /*
2938 * NAME: dbFindLeaf()
2939 *
2940 * FUNCTION: search a dmtree_t for sufficient free blocks, returning
2941 * the index of a leaf describing the free blocks if
2942 * sufficient free blocks are found.
2943 *
2944 * the search starts at the top of the dmtree_t tree and
2945 * proceeds down the tree to the leftmost leaf with sufficient
2946 * free space.
2947 *
2948 * PARAMETERS:
2949 * tp - pointer to the tree to be searched.
2950 * l2nb - log2 number of free blocks to search for.
2951 * leafidx - return pointer to be set to the index of the leaf
2952 * describing at least l2nb free blocks if sufficient
2953 * free blocks are found.
2954 *
2955 * RETURN VALUES:
2956 * 0 - success
2957 * -ENOSPC - insufficient free blocks.
2958 */
2960 {
2963 /* first check the root of the tree to see if there is
2964 * sufficient free space.
2965 */
2969 /* sufficient free space available. now search down the tree
2970 * starting at the next level for the leftmost leaf that
2971 * describes sufficient free space.
2972 */
2975 /* search the four nodes at this level, starting from
2976 * the left.
2977 */
2979 /* sufficient free space found. move to the next
2980 * level (or quit if this is the last level).
2981 */
2984 }
2986 /* better have found something since the higher
2987 * levels of the tree said it was here.
2988 */
2990 }
2992 /* set the return to the leftmost leaf describing sufficient
2993 * free space.
2994 */
2998 }
3001 /*
3002 * NAME: dbFindBits()
3003 *
3004 * FUNCTION: find a specified number of binary buddy free bits within a
3005 * dmap bitmap word value.
3006 *
3007 * this routine searches the bitmap value for (1 << l2nb) free
3008 * bits at (1 << l2nb) alignments within the value.
3009 *
3010 * PARAMETERS:
3011 * word - dmap bitmap word value.
3012 * l2nb - number of free bits specified as a log2 number.
3013 *
3014 * RETURN VALUES:
3015 * starting bit number of free bits.
3016 */
3018 {
3020 u32 mask;
3022 /* get the number of bits.
3023 */
3027 /* complement the word so we can use a mask (i.e. 0s represent
3028 * free bits) and compute the mask.
3029 */
3033 /* scan the word for nb free bits at nb alignments.
3034 */
3038 }
3042 /* return the bit number.
3043 */
3045 }
3048 /*
3049 * NAME: dbMaxBud(u8 *cp)
3050 *
3051 * FUNCTION: determine the largest binary buddy string of free
3052 * bits within 32-bits of the map.
3053 *
3054 * PARAMETERS:
3055 * cp - pointer to the 32-bit value.
3056 *
3057 * RETURN VALUES:
3058 * largest binary buddy of free bits within a dmap word.
3059 */
3061 {
3064 /* check if the wmap word is all free. if so, the
3065 * free buddy size is BUDMIN.
3066 */
3070 /* check if the wmap word is half free. if so, the
3071 * free buddy size is BUDMIN-1.
3072 */
3076 /* not all free or half free. determine the free buddy
3077 * size thru table lookup using quarters of the wmap word.
3078 */
3082 }
3085 /*
3086 * NAME: cnttz(uint word)
3087 *
3088 * FUNCTION: determine the number of trailing zeros within a 32-bit
3089 * value.
3090 *
3091 * PARAMETERS:
3092 * value - 32-bit value to be examined.
3093 *
3094 * RETURN VALUES:
3095 * count of trailing zeros
3096 */
3098 {
3104 }
3107 }
3110 /*
3111 * NAME: cntlz(u32 value)
3112 *
3113 * FUNCTION: determine the number of leading zeros within a 32-bit
3114 * value.
3115 *
3116 * PARAMETERS:
3117 * value - 32-bit value to be examined.
3118 *
3119 * RETURN VALUES:
3120 * count of leading zeros
3121 */
3123 {
3129 }
3131 }
3134 /*
3135 * NAME: blkstol2(s64 nb)
3136 *
3137 * FUNCTION: convert a block count to its log2 value. if the block
3138 * count is not a l2 multiple, it is rounded up to the next
3139 * larger l2 multiple.
3140 *
3141 * PARAMETERS:
3142 * nb - number of blocks
3143 *
3144 * RETURN VALUES:
3145 * log2 number of blocks
3146 */
3148 {
3154 /* count the leading bits.
3155 */
3157 /* leading bit found.
3158 */
3160 /* determine the l2 value.
3161 */
3164 /* check if we need to round up.
3165 */
3167 l2nb++;
3170 }
3171 }
3174 }
3177 /*
3178 * NAME: dbAllocBottomUp()
3179 *
3180 * FUNCTION: alloc the specified block range from the working block
3181 * allocation map.
3182 *
3183 * the blocks will be alloc from the working map one dmap
3184 * at a time.
3185 *
3186 * PARAMETERS:
3187 * ip - pointer to in-core inode;
3188 * blkno - starting block number to be freed.
3189 * nblocks - number of blocks to be freed.
3190 *
3191 * RETURN VALUES:
3192 * 0 - success
3193 * -EIO - i/o error
3194 */
3196 {
3206 /* block to be allocated better be within the mapsize. */
3209 /*
3210 * allocate the blocks a dmap at a time.
3211 */
3214 /* release previous dmap if any */
3217 }
3219 /* get the buffer for the current dmap. */
3225 }
3228 /* determine the number of blocks to be allocated from
3229 * this dmap.
3230 */
3233 /* allocate the blocks. */
3238 }
3239 }
3241 /* write the last buffer. */
3247 }
3252 {
3255 s8 oldroot;
3258 /* save the current value of the root (i.e. maximum free string)
3259 * of the dmap tree.
3260 */
3263 /* determine the bit number and word within the dmap of the
3264 * starting block.
3265 */
3269 /* block range better be within the dmap */
3272 /* allocate the bits of the dmap's words corresponding to the block
3273 * range. not all bits of the first and last words may be contained
3274 * within the block range. if this is the case, we'll work against
3275 * those words (i.e. partial first and/or last) on an individual basis
3276 * (a single pass), allocating the bits of interest by hand and
3277 * updating the leaf corresponding to the dmap word. a single pass
3278 * will be used for all dmap words fully contained within the
3279 * specified range. within this pass, the bits of all fully contained
3280 * dmap words will be marked as free in a single shot and the leaves
3281 * will be updated. a single leaf may describe the free space of
3282 * multiple dmap words, so we may update only a subset of the actual
3283 * leaves corresponding to the dmap words of the block range.
3284 */
3286 /* determine the bit number within the word and
3287 * the number of bits within the word.
3288 */
3292 /* check if only part of a word is to be allocated.
3293 */
3295 /* allocate (set to 1) the appropriate bits within
3296 * this dmap word.
3297 */
3301 word++;
3303 /* one or more dmap words are fully contained
3304 * within the block range. determine how many
3305 * words and allocate (set to 1) the bits of these
3306 * words.
3307 */
3311 /* determine how many bits */
3314 }
3315 }
3317 /* update the free count for this dmap */
3320 /* reconstruct summary tree */
3325 /* if this allocation group is completely free,
3326 * update the highest active allocation group number
3327 * if this allocation group is the new max.
3328 */
3333 /* update the free count for the allocation group and map */
3339 /* if the root has not changed, done. */
3343 /* root changed. bubble the change up to the dmap control pages.
3344 * if the adjustment of the upper level control pages fails,
3345 * backout the bit allocation (thus making everything consistent).
3346 */
3351 }
3354 /*
3355 * NAME: dbExtendFS()
3356 *
3357 * FUNCTION: extend bmap from blkno for nblocks;
3358 * dbExtendFS() updates bmap ready for dbAllocBottomUp();
3359 *
3360 * L2
3361 * |
3362 * L1---------------------------------L1
3363 * | |
3364 * L0---------L0---------L0 L0---------L0---------L0
3365 * | | | | | |
3366 * d0,...,dn d0,...,dn d0,...,dn d0,...,dn d0,...,dn d0,.,dm;
3367 * L2L1L0d0,...,dnL0d0,...,dnL0d0,...,dnL1L0d0,...,dnL0d0,...,dnL0d0,..dm
3368 *
3369 * <---old---><----------------------------extend----------------------->
3370 */
3372 {
3376 s64 newsize;
3377 s64 p;
3384 s64 ag_rem;
3391 /*
3392 * initialize bmap control page.
3393 *
3394 * all the data in bmap control page should exclude
3395 * the mkfs hidden dmap page.
3396 */
3398 /* update mapsize */
3402 /* compute new AG size */
3409 /* compute new number of AG */
3414 /*
3415 * reconfigure db_agfree[]
3416 * from old AG configuration to new AG configuration;
3417 *
3418 * coalesce contiguous k (newAGSize/oldAGSize) AGs;
3419 * i.e., (AGi, ..., AGj) where i = k*n and j = k*(n+1) - 1 to AGn;
3420 * note: new AG size = old AG size * (2**x).
3421 */
3429 /* coalesce contiguous k AGs; */
3431 /* merge AGi to AGn */
3433 }
3434 }
3440 /*
3441 * update highest active ag number
3442 */
3446 /*
3447 * extend bmap
3448 *
3449 * update bit maps and corresponding level control pages;
3450 * global control page db_nfree, db_agfree[agno], db_maxfreebud;
3451 */
3452 extend:
3453 /* get L2 page */
3459 }
3462 /* compute start L1 */
3467 /*
3468 * extend each L1 in L2
3469 */
3471 /* get L1 page */
3473 /* read in L1 page: (blkno & (MAXL1SIZE - 1)) */
3479 /* compute start L0 */
3485 /* assign/init L1 page */
3492 /* compute start L0 */
3496 }
3498 /*
3499 * extend each L0 in L1
3500 */
3502 /* get L0 page */
3504 /* read in L0 page: (blkno & (MAXL0SIZE - 1)) */
3511 /* compute start dmap */
3513 L2BPERDMAP;
3519 /* assign/init L0 page */
3526 /* compute start dmap */
3530 }
3532 /*
3533 * extend each dmap in L0
3534 */
3536 /*
3537 * reconstruct the dmap page, and
3538 * initialize corresponding parent L0 leaf
3539 */
3541 /* read in dmap page: */
3548 /* assign/init dmap page */
3555 }
3566 l0leaf++;
3575 /*
3576 * build current L0 page from its leaves, and
3577 * initialize corresponding parent L1 leaf
3578 */
3586 /* more than 1 L0 ? */
3590 /* summarize in global bmap page */
3595 }
3596 }
3599 /*
3600 * build current L1 page from its leaves, and
3601 * initialize corresponding parent L2 leaf
3602 */
3610 /* more than 1 L1 ? */
3614 /* summarize in global bmap page */
3618 }
3619 }
3623 errout:
3631 /*
3632 * finalize bmap control page
3633 */
3634 finalize:
3637 }
3640 /*
3641 * dbFinalizeBmap()
3642 */
3644 {
3650 /*
3651 * finalize bmap control page
3652 */
3653 //finalize:
3654 /*
3655 * compute db_agpref: preferred ag to allocate from
3656 * (the leftmost ag with average free space in it);
3657 */
3658 //agpref:
3659 /* get the number of active ags and inacitve ags */
3664 /* determine how many blocks are in the inactive allocation
3665 * groups. in doing this, we must account for the fact that
3666 * the rightmost group might be a partial group (i.e. file
3667 * system size is not a multiple of the group size).
3668 */
3673 /* determine how many free blocks are in the active
3674 * allocation groups plus the average number of free blocks
3675 * within the active ags.
3676 */
3680 /* if the preferred allocation group has not average free space.
3681 * re-establish the preferred group as the leftmost
3682 * group with average free space.
3683 */
3689 }
3693 }
3694 }
3696 /*
3697 * compute db_aglevel, db_agheight, db_width, db_agstart:
3698 * an ag is covered in aglevel dmapctl summary tree,
3699 * at agheight level height (from leaf) with agwidth number of nodes
3700 * each, which starts at agstart index node of the smmary tree node
3701 * array;
3702 */
3704 l2nl =
3709 i--) {
3712 }
3714 }
3717 /*
3718 * NAME: dbInitDmap()/ujfs_idmap_page()
3719 *
3720 * FUNCTION: initialize working/persistent bitmap of the dmap page
3721 * for the specified number of blocks:
3722 *
3723 * at entry, the bitmaps had been initialized as free (ZEROS);
3724 * The number of blocks will only account for the actually
3725 * existing blocks. Blocks which don't actually exist in
3726 * the aggregate will be marked as allocated (ONES);
3727 *
3728 * PARAMETERS:
3729 * dp - pointer to page of map
3730 * nblocks - number of blocks this page
3731 *
3732 * RETURNS: NONE
3733 */
3735 {
3738 /* starting block number within the dmap */
3749 }
3753 }
3755 /* word number containing start block number */
3758 /*
3759 * free the bits corresponding to the block range (ZEROS):
3760 * note: not all bits of the first and last words may be contained
3761 * within the block range.
3762 */
3764 /* number of bits preceding range to be freed in the word */
3766 /* number of bits to free in the word */
3769 /* is partial word to be freed ? */
3771 /* free (set to 0) from the bitmap word */
3777 /* skip the word freed */
3778 w++;
3780 /* free (set to 0) contiguous bitmap words */
3785 /* skip the words freed */
3788 }
3789 }
3791 /*
3792 * mark bits following the range to be freed (non-existing
3793 * blocks) as allocated (ONES)
3794 */
3799 /* the first word beyond the end of existing blocks */
3802 /* does nblocks fall on a 32-bit boundary ? */
3805 /* mark a partial word allocated */
3807 w++;
3808 }
3810 /* set the rest of the words in the page to allocated (ONES) */
3814 /*
3815 * init tree
3816 */
3817 initTree:
3819 }
3822 /*
3823 * NAME: dbInitDmapTree()/ujfs_complete_dmap()
3824 *
3825 * FUNCTION: initialize summary tree of the specified dmap:
3826 *
3827 * at entry, bitmap of the dmap has been initialized;
3828 *
3829 * PARAMETERS:
3830 * dp - dmap to complete
3831 * blkno - starting block number for this dmap
3832 * treemax - will be filled in with max free for this dmap
3833 *
3834 * RETURNS: max free string at the root of the tree
3835 */
3837 {
3842 /* init fixed info of tree */
3850 /* init each leaf from corresponding wmap word:
3851 * note: leaf is set to NOFREE(-1) if all blocks of corresponding
3852 * bitmap word are allocated.
3853 */
3858 /* build the dmap's binary buddy summary tree */
3860 }
3863 /*
3864 * NAME: dbInitTree()/ujfs_adjtree()
3865 *
3866 * FUNCTION: initialize binary buddy summary tree of a dmap or dmapctl.
3867 *
3868 * at entry, the leaves of the tree has been initialized
3869 * from corresponding bitmap word or root of summary tree
3870 * of the child control page;
3871 * configure binary buddy system at the leaf level, then
3872 * bubble up the values of the leaf nodes up the tree.
3873 *
3874 * PARAMETERS:
3875 * cp - Pointer to the root of the tree
3876 * l2leaves- Number of leaf nodes as a power of 2
3877 * l2min - Number of blocks that can be covered by a leaf
3878 * as a power of 2
3879 *
3880 * RETURNS: max free string at the root of the tree
3881 */
3883 {
3890 /* Determine the maximum free string possible for the leaves */
3893 /*
3894 * configure the leaf levevl into binary buddy system
3895 *
3896 * Try to combine buddies starting with a buddy size of 1
3897 * (i.e. two leaves). At a buddy size of 1 two buddy leaves
3898 * can be combined if both buddies have a maximum free of l2min;
3899 * the combination will result in the left-most buddy leaf having
3900 * a maximum free of l2min+1.
3901 * After processing all buddies for a given size, process buddies
3902 * at the next higher buddy size (i.e. current size * 2) and
3903 * the next maximum free (current free + 1).
3904 * This continues until the maximum possible buddy combination
3905 * yields maximum free.
3906 */
3909 /* get next buddy size == current buddy pair size */
3912 /* scan each adjacent buddy pair at current buddy size */
3916 /* coalesce if both adjacent buddies are max free */
3920 }
3921 }
3922 }
3924 /*
3925 * bubble summary information of leaves up the tree.
3926 *
3927 * Starting at the leaf node level, the four nodes described by
3928 * the higher level parent node are compared for a maximum free and
3929 * this maximum becomes the value of the parent node.
3930 * when all lower level nodes are processed in this fashion then
3931 * move up to the next level (parent becomes a lower level node) and
3932 * continue the process for that level.
3933 */
3937 /* get index of 1st node of parent level */
3940 /* set the value of the parent node as the maximum
3941 * of the four nodes of the current level.
3942 */
3946 }
3949 }
3952 /*
3953 * dbInitDmapCtl()
3954 *
3955 * function: initialize dmapctl page
3956 */
3967 /*
3968 * initialize the leaves of current level that were not covered
3969 * by the specified input block range (i.e. the leaves have no
3970 * low level dmapctl or dmap).
3971 */
3976 /* build the dmap's binary buddy summary tree */
3978 }
3981 /*
3982 * NAME: dbGetL2AGSize()/ujfs_getagl2size()
3983 *
3984 * FUNCTION: Determine log2(allocation group size) from aggregate size
3985 *
3986 * PARAMETERS:
3987 * nblocks - Number of blocks in aggregate
3988 *
3989 * RETURNS: log2(allocation group size) in aggregate blocks
3990 */
3992 {
3993 s64 sz;
3994 s64 m;
4000 /* round up aggregate size to power of 2 */
4005 }
4011 /* agsize = roundupSize/max_number_of_ag */
4013 }
4016 /*
4017 * NAME: dbMapFileSizeToMapSize()
4018 *
4019 * FUNCTION: compute number of blocks the block allocation map file
4020 * can cover from the map file size;
4021 *
4022 * RETURNS: Number of blocks which can be covered by this block map file;
4023 */
4025 /*
4026 * maximum number of map pages at each level including control pages
4027 */
4028 #define MAXL0PAGES (1 + LPERCTL)
4029 #define MAXL1PAGES (1 + LPERCTL * MAXL0PAGES)
4030 #define MAXL2PAGES (1 + LPERCTL * MAXL1PAGES)
4032 /*
4033 * convert number of map pages to the zero origin top dmapctl level
4034 */
4035 #define BMAPPGTOLEV(npages) \
4036 (((npages) <= 3 + MAXL0PAGES) ? 0 : \
4037 ((npages) <= 2 + MAXL1PAGES) ? 1 : 2)
4040 {
4042 s64 nblocks;
4051 /* At each level, accumulate the number of dmap pages covered by
4052 * the number of full child levels below it;
4053 * repeat for the last incomplete child level.
4054 */
4057 /* skip higher level control pages above top level covered by map */
4061 factor =
4067 /* pages in last/incomplete child */
4069 /* skip incomplete child's level control page */
4070 npages--;
4071 }
4073 /* convert the number of dmaps into the number of blocks
4074 * which can be covered by the dmaps;
4075 */
4079 }