Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
[linux/fpc-iii.git] / fs / ufs / util.h
blobe1f1b2e868a7d55cc66b4333ad542573df5a5acc
1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * linux/fs/ufs/util.h
5 * Copyright (C) 1998
6 * Daniel Pirkl <daniel.pirkl@email.cz>
7 * Charles University, Faculty of Mathematics and Physics
8 */
10 #include <linux/buffer_head.h>
11 #include <linux/fs.h>
12 #include "swab.h"
16 * some useful macros
18 #define in_range(b,first,len) ((b)>=(first)&&(b)<(first)+(len))
21 * functions used for retyping
23 static inline struct ufs_buffer_head *UCPI_UBH(struct ufs_cg_private_info *cpi)
25 return &cpi->c_ubh;
27 static inline struct ufs_buffer_head *USPI_UBH(struct ufs_sb_private_info *spi)
29 return &spi->s_ubh;
35 * macros used for accessing structures
37 static inline s32
38 ufs_get_fs_state(struct super_block *sb, struct ufs_super_block_first *usb1,
39 struct ufs_super_block_third *usb3)
41 switch (UFS_SB(sb)->s_flags & UFS_ST_MASK) {
42 case UFS_ST_SUNOS:
43 if (fs32_to_cpu(sb, usb3->fs_postblformat) == UFS_42POSTBLFMT)
44 return fs32_to_cpu(sb, usb1->fs_u0.fs_sun.fs_state);
45 /* Fall Through - to UFS_ST_SUN */
46 case UFS_ST_SUN:
47 return fs32_to_cpu(sb, usb3->fs_un2.fs_sun.fs_state);
48 case UFS_ST_SUNx86:
49 return fs32_to_cpu(sb, usb1->fs_u1.fs_sunx86.fs_state);
50 case UFS_ST_44BSD:
51 default:
52 return fs32_to_cpu(sb, usb3->fs_un2.fs_44.fs_state);
56 static inline void
57 ufs_set_fs_state(struct super_block *sb, struct ufs_super_block_first *usb1,
58 struct ufs_super_block_third *usb3, s32 value)
60 switch (UFS_SB(sb)->s_flags & UFS_ST_MASK) {
61 case UFS_ST_SUNOS:
62 if (fs32_to_cpu(sb, usb3->fs_postblformat) == UFS_42POSTBLFMT) {
63 usb1->fs_u0.fs_sun.fs_state = cpu_to_fs32(sb, value);
64 break;
66 /* Fall Through - to UFS_ST_SUN */
67 case UFS_ST_SUN:
68 usb3->fs_un2.fs_sun.fs_state = cpu_to_fs32(sb, value);
69 break;
70 case UFS_ST_SUNx86:
71 usb1->fs_u1.fs_sunx86.fs_state = cpu_to_fs32(sb, value);
72 break;
73 case UFS_ST_44BSD:
74 usb3->fs_un2.fs_44.fs_state = cpu_to_fs32(sb, value);
75 break;
79 static inline u32
80 ufs_get_fs_npsect(struct super_block *sb, struct ufs_super_block_first *usb1,
81 struct ufs_super_block_third *usb3)
83 if ((UFS_SB(sb)->s_flags & UFS_ST_MASK) == UFS_ST_SUNx86)
84 return fs32_to_cpu(sb, usb3->fs_un2.fs_sunx86.fs_npsect);
85 else
86 return fs32_to_cpu(sb, usb1->fs_u1.fs_sun.fs_npsect);
89 static inline u64
90 ufs_get_fs_qbmask(struct super_block *sb, struct ufs_super_block_third *usb3)
92 __fs64 tmp;
94 switch (UFS_SB(sb)->s_flags & UFS_ST_MASK) {
95 case UFS_ST_SUNOS:
96 case UFS_ST_SUN:
97 ((__fs32 *)&tmp)[0] = usb3->fs_un2.fs_sun.fs_qbmask[0];
98 ((__fs32 *)&tmp)[1] = usb3->fs_un2.fs_sun.fs_qbmask[1];
99 break;
100 case UFS_ST_SUNx86:
101 ((__fs32 *)&tmp)[0] = usb3->fs_un2.fs_sunx86.fs_qbmask[0];
102 ((__fs32 *)&tmp)[1] = usb3->fs_un2.fs_sunx86.fs_qbmask[1];
103 break;
104 case UFS_ST_44BSD:
105 ((__fs32 *)&tmp)[0] = usb3->fs_un2.fs_44.fs_qbmask[0];
106 ((__fs32 *)&tmp)[1] = usb3->fs_un2.fs_44.fs_qbmask[1];
107 break;
110 return fs64_to_cpu(sb, tmp);
113 static inline u64
114 ufs_get_fs_qfmask(struct super_block *sb, struct ufs_super_block_third *usb3)
116 __fs64 tmp;
118 switch (UFS_SB(sb)->s_flags & UFS_ST_MASK) {
119 case UFS_ST_SUNOS:
120 case UFS_ST_SUN:
121 ((__fs32 *)&tmp)[0] = usb3->fs_un2.fs_sun.fs_qfmask[0];
122 ((__fs32 *)&tmp)[1] = usb3->fs_un2.fs_sun.fs_qfmask[1];
123 break;
124 case UFS_ST_SUNx86:
125 ((__fs32 *)&tmp)[0] = usb3->fs_un2.fs_sunx86.fs_qfmask[0];
126 ((__fs32 *)&tmp)[1] = usb3->fs_un2.fs_sunx86.fs_qfmask[1];
127 break;
128 case UFS_ST_44BSD:
129 ((__fs32 *)&tmp)[0] = usb3->fs_un2.fs_44.fs_qfmask[0];
130 ((__fs32 *)&tmp)[1] = usb3->fs_un2.fs_44.fs_qfmask[1];
131 break;
134 return fs64_to_cpu(sb, tmp);
137 static inline u16
138 ufs_get_de_namlen(struct super_block *sb, struct ufs_dir_entry *de)
140 if ((UFS_SB(sb)->s_flags & UFS_DE_MASK) == UFS_DE_OLD)
141 return fs16_to_cpu(sb, de->d_u.d_namlen);
142 else
143 return de->d_u.d_44.d_namlen; /* XXX this seems wrong */
146 static inline void
147 ufs_set_de_namlen(struct super_block *sb, struct ufs_dir_entry *de, u16 value)
149 if ((UFS_SB(sb)->s_flags & UFS_DE_MASK) == UFS_DE_OLD)
150 de->d_u.d_namlen = cpu_to_fs16(sb, value);
151 else
152 de->d_u.d_44.d_namlen = value; /* XXX this seems wrong */
155 static inline void
156 ufs_set_de_type(struct super_block *sb, struct ufs_dir_entry *de, int mode)
158 if ((UFS_SB(sb)->s_flags & UFS_DE_MASK) != UFS_DE_44BSD)
159 return;
162 * TODO turn this into a table lookup
164 switch (mode & S_IFMT) {
165 case S_IFSOCK:
166 de->d_u.d_44.d_type = DT_SOCK;
167 break;
168 case S_IFLNK:
169 de->d_u.d_44.d_type = DT_LNK;
170 break;
171 case S_IFREG:
172 de->d_u.d_44.d_type = DT_REG;
173 break;
174 case S_IFBLK:
175 de->d_u.d_44.d_type = DT_BLK;
176 break;
177 case S_IFDIR:
178 de->d_u.d_44.d_type = DT_DIR;
179 break;
180 case S_IFCHR:
181 de->d_u.d_44.d_type = DT_CHR;
182 break;
183 case S_IFIFO:
184 de->d_u.d_44.d_type = DT_FIFO;
185 break;
186 default:
187 de->d_u.d_44.d_type = DT_UNKNOWN;
191 static inline u32
192 ufs_get_inode_uid(struct super_block *sb, struct ufs_inode *inode)
194 switch (UFS_SB(sb)->s_flags & UFS_UID_MASK) {
195 case UFS_UID_44BSD:
196 return fs32_to_cpu(sb, inode->ui_u3.ui_44.ui_uid);
197 case UFS_UID_EFT:
198 if (inode->ui_u1.oldids.ui_suid == 0xFFFF)
199 return fs32_to_cpu(sb, inode->ui_u3.ui_sun.ui_uid);
200 /* Fall through */
201 default:
202 return fs16_to_cpu(sb, inode->ui_u1.oldids.ui_suid);
206 static inline void
207 ufs_set_inode_uid(struct super_block *sb, struct ufs_inode *inode, u32 value)
209 switch (UFS_SB(sb)->s_flags & UFS_UID_MASK) {
210 case UFS_UID_44BSD:
211 inode->ui_u3.ui_44.ui_uid = cpu_to_fs32(sb, value);
212 inode->ui_u1.oldids.ui_suid = cpu_to_fs16(sb, value);
213 break;
214 case UFS_UID_EFT:
215 inode->ui_u3.ui_sun.ui_uid = cpu_to_fs32(sb, value);
216 if (value > 0xFFFF)
217 value = 0xFFFF;
218 /* Fall through */
219 default:
220 inode->ui_u1.oldids.ui_suid = cpu_to_fs16(sb, value);
221 break;
225 static inline u32
226 ufs_get_inode_gid(struct super_block *sb, struct ufs_inode *inode)
228 switch (UFS_SB(sb)->s_flags & UFS_UID_MASK) {
229 case UFS_UID_44BSD:
230 return fs32_to_cpu(sb, inode->ui_u3.ui_44.ui_gid);
231 case UFS_UID_EFT:
232 if (inode->ui_u1.oldids.ui_sgid == 0xFFFF)
233 return fs32_to_cpu(sb, inode->ui_u3.ui_sun.ui_gid);
234 /* Fall through */
235 default:
236 return fs16_to_cpu(sb, inode->ui_u1.oldids.ui_sgid);
240 static inline void
241 ufs_set_inode_gid(struct super_block *sb, struct ufs_inode *inode, u32 value)
243 switch (UFS_SB(sb)->s_flags & UFS_UID_MASK) {
244 case UFS_UID_44BSD:
245 inode->ui_u3.ui_44.ui_gid = cpu_to_fs32(sb, value);
246 inode->ui_u1.oldids.ui_sgid = cpu_to_fs16(sb, value);
247 break;
248 case UFS_UID_EFT:
249 inode->ui_u3.ui_sun.ui_gid = cpu_to_fs32(sb, value);
250 if (value > 0xFFFF)
251 value = 0xFFFF;
252 /* Fall through */
253 default:
254 inode->ui_u1.oldids.ui_sgid = cpu_to_fs16(sb, value);
255 break;
259 extern dev_t ufs_get_inode_dev(struct super_block *, struct ufs_inode_info *);
260 extern void ufs_set_inode_dev(struct super_block *, struct ufs_inode_info *, dev_t);
261 extern int ufs_prepare_chunk(struct page *page, loff_t pos, unsigned len);
264 * These functions manipulate ufs buffers
266 #define ubh_bread(sb,fragment,size) _ubh_bread_(uspi,sb,fragment,size)
267 extern struct ufs_buffer_head * _ubh_bread_(struct ufs_sb_private_info *, struct super_block *, u64 , u64);
268 extern struct ufs_buffer_head * ubh_bread_uspi(struct ufs_sb_private_info *, struct super_block *, u64, u64);
269 extern void ubh_brelse (struct ufs_buffer_head *);
270 extern void ubh_brelse_uspi (struct ufs_sb_private_info *);
271 extern void ubh_mark_buffer_dirty (struct ufs_buffer_head *);
272 extern void ubh_mark_buffer_uptodate (struct ufs_buffer_head *, int);
273 extern void ubh_sync_block(struct ufs_buffer_head *);
274 extern void ubh_bforget (struct ufs_buffer_head *);
275 extern int ubh_buffer_dirty (struct ufs_buffer_head *);
276 #define ubh_ubhcpymem(mem,ubh,size) _ubh_ubhcpymem_(uspi,mem,ubh,size)
277 extern void _ubh_ubhcpymem_(struct ufs_sb_private_info *, unsigned char *, struct ufs_buffer_head *, unsigned);
278 #define ubh_memcpyubh(ubh,mem,size) _ubh_memcpyubh_(uspi,ubh,mem,size)
279 extern void _ubh_memcpyubh_(struct ufs_sb_private_info *, struct ufs_buffer_head *, unsigned char *, unsigned);
281 /* This functions works with cache pages*/
282 extern struct page *ufs_get_locked_page(struct address_space *mapping,
283 pgoff_t index);
284 static inline void ufs_put_locked_page(struct page *page)
286 unlock_page(page);
287 put_page(page);
292 * macros and inline function to get important structures from ufs_sb_private_info
295 static inline void *get_usb_offset(struct ufs_sb_private_info *uspi,
296 unsigned int offset)
298 unsigned int index;
300 index = offset >> uspi->s_fshift;
301 offset &= ~uspi->s_fmask;
302 return uspi->s_ubh.bh[index]->b_data + offset;
305 #define ubh_get_usb_first(uspi) \
306 ((struct ufs_super_block_first *)get_usb_offset((uspi), 0))
308 #define ubh_get_usb_second(uspi) \
309 ((struct ufs_super_block_second *)get_usb_offset((uspi), UFS_SECTOR_SIZE))
311 #define ubh_get_usb_third(uspi) \
312 ((struct ufs_super_block_third *)get_usb_offset((uspi), 2*UFS_SECTOR_SIZE))
315 #define ubh_get_ucg(ubh) \
316 ((struct ufs_cylinder_group *)((ubh)->bh[0]->b_data))
320 * Extract byte from ufs_buffer_head
321 * Extract the bits for a block from a map inside ufs_buffer_head
323 #define ubh_get_addr8(ubh,begin) \
324 ((u8*)(ubh)->bh[(begin) >> uspi->s_fshift]->b_data + \
325 ((begin) & ~uspi->s_fmask))
327 #define ubh_get_addr16(ubh,begin) \
328 (((__fs16*)((ubh)->bh[(begin) >> (uspi->s_fshift-1)]->b_data)) + \
329 ((begin) & ((uspi->fsize>>1) - 1)))
331 #define ubh_get_addr32(ubh,begin) \
332 (((__fs32*)((ubh)->bh[(begin) >> (uspi->s_fshift-2)]->b_data)) + \
333 ((begin) & ((uspi->s_fsize>>2) - 1)))
335 #define ubh_get_addr64(ubh,begin) \
336 (((__fs64*)((ubh)->bh[(begin) >> (uspi->s_fshift-3)]->b_data)) + \
337 ((begin) & ((uspi->s_fsize>>3) - 1)))
339 #define ubh_get_addr ubh_get_addr8
341 static inline void *ubh_get_data_ptr(struct ufs_sb_private_info *uspi,
342 struct ufs_buffer_head *ubh,
343 u64 blk)
345 if (uspi->fs_magic == UFS2_MAGIC)
346 return ubh_get_addr64(ubh, blk);
347 else
348 return ubh_get_addr32(ubh, blk);
351 #define ubh_blkmap(ubh,begin,bit) \
352 ((*ubh_get_addr(ubh, (begin) + ((bit) >> 3)) >> ((bit) & 7)) & (0xff >> (UFS_MAXFRAG - uspi->s_fpb)))
354 static inline u64
355 ufs_freefrags(struct ufs_sb_private_info *uspi)
357 return ufs_blkstofrags(uspi->cs_total.cs_nbfree) +
358 uspi->cs_total.cs_nffree;
362 * Macros to access cylinder group array structures
364 #define ubh_cg_blktot(ucpi,cylno) \
365 (*((__fs32*)ubh_get_addr(UCPI_UBH(ucpi), (ucpi)->c_btotoff + ((cylno) << 2))))
367 #define ubh_cg_blks(ucpi,cylno,rpos) \
368 (*((__fs16*)ubh_get_addr(UCPI_UBH(ucpi), \
369 (ucpi)->c_boff + (((cylno) * uspi->s_nrpos + (rpos)) << 1 ))))
372 * Bitmap operations
373 * These functions work like classical bitmap operations.
374 * The difference is that we don't have the whole bitmap
375 * in one contiguous chunk of memory, but in several buffers.
376 * The parameters of each function are super_block, ufs_buffer_head and
377 * position of the beginning of the bitmap.
379 #define ubh_setbit(ubh,begin,bit) \
380 (*ubh_get_addr(ubh, (begin) + ((bit) >> 3)) |= (1 << ((bit) & 7)))
382 #define ubh_clrbit(ubh,begin,bit) \
383 (*ubh_get_addr (ubh, (begin) + ((bit) >> 3)) &= ~(1 << ((bit) & 7)))
385 #define ubh_isset(ubh,begin,bit) \
386 (*ubh_get_addr (ubh, (begin) + ((bit) >> 3)) & (1 << ((bit) & 7)))
388 #define ubh_isclr(ubh,begin,bit) (!ubh_isset(ubh,begin,bit))
390 #define ubh_find_first_zero_bit(ubh,begin,size) _ubh_find_next_zero_bit_(uspi,ubh,begin,size,0)
392 #define ubh_find_next_zero_bit(ubh,begin,size,offset) _ubh_find_next_zero_bit_(uspi,ubh,begin,size,offset)
393 static inline unsigned _ubh_find_next_zero_bit_(
394 struct ufs_sb_private_info * uspi, struct ufs_buffer_head * ubh,
395 unsigned begin, unsigned size, unsigned offset)
397 unsigned base, count, pos;
399 size -= offset;
400 begin <<= 3;
401 offset += begin;
402 base = offset >> uspi->s_bpfshift;
403 offset &= uspi->s_bpfmask;
404 for (;;) {
405 count = min_t(unsigned int, size + offset, uspi->s_bpf);
406 size -= count - offset;
407 pos = find_next_zero_bit_le(ubh->bh[base]->b_data, count, offset);
408 if (pos < count || !size)
409 break;
410 base++;
411 offset = 0;
413 return (base << uspi->s_bpfshift) + pos - begin;
416 static inline unsigned find_last_zero_bit (unsigned char * bitmap,
417 unsigned size, unsigned offset)
419 unsigned bit, i;
420 unsigned char * mapp;
421 unsigned char map;
423 mapp = bitmap + (size >> 3);
424 map = *mapp--;
425 bit = 1 << (size & 7);
426 for (i = size; i > offset; i--) {
427 if ((map & bit) == 0)
428 break;
429 if ((i & 7) != 0) {
430 bit >>= 1;
431 } else {
432 map = *mapp--;
433 bit = 1 << 7;
436 return i;
439 #define ubh_find_last_zero_bit(ubh,begin,size,offset) _ubh_find_last_zero_bit_(uspi,ubh,begin,size,offset)
440 static inline unsigned _ubh_find_last_zero_bit_(
441 struct ufs_sb_private_info * uspi, struct ufs_buffer_head * ubh,
442 unsigned begin, unsigned start, unsigned end)
444 unsigned base, count, pos, size;
446 size = start - end;
447 begin <<= 3;
448 start += begin;
449 base = start >> uspi->s_bpfshift;
450 start &= uspi->s_bpfmask;
451 for (;;) {
452 count = min_t(unsigned int,
453 size + (uspi->s_bpf - start), uspi->s_bpf)
454 - (uspi->s_bpf - start);
455 size -= count;
456 pos = find_last_zero_bit (ubh->bh[base]->b_data,
457 start, start - count);
458 if (pos > start - count || !size)
459 break;
460 base--;
461 start = uspi->s_bpf;
463 return (base << uspi->s_bpfshift) + pos - begin;
466 #define ubh_isblockclear(ubh,begin,block) (!_ubh_isblockset_(uspi,ubh,begin,block))
468 #define ubh_isblockset(ubh,begin,block) _ubh_isblockset_(uspi,ubh,begin,block)
469 static inline int _ubh_isblockset_(struct ufs_sb_private_info * uspi,
470 struct ufs_buffer_head * ubh, unsigned begin, unsigned block)
472 u8 mask;
473 switch (uspi->s_fpb) {
474 case 8:
475 return (*ubh_get_addr (ubh, begin + block) == 0xff);
476 case 4:
477 mask = 0x0f << ((block & 0x01) << 2);
478 return (*ubh_get_addr (ubh, begin + (block >> 1)) & mask) == mask;
479 case 2:
480 mask = 0x03 << ((block & 0x03) << 1);
481 return (*ubh_get_addr (ubh, begin + (block >> 2)) & mask) == mask;
482 case 1:
483 mask = 0x01 << (block & 0x07);
484 return (*ubh_get_addr (ubh, begin + (block >> 3)) & mask) == mask;
486 return 0;
489 #define ubh_clrblock(ubh,begin,block) _ubh_clrblock_(uspi,ubh,begin,block)
490 static inline void _ubh_clrblock_(struct ufs_sb_private_info * uspi,
491 struct ufs_buffer_head * ubh, unsigned begin, unsigned block)
493 switch (uspi->s_fpb) {
494 case 8:
495 *ubh_get_addr (ubh, begin + block) = 0x00;
496 return;
497 case 4:
498 *ubh_get_addr (ubh, begin + (block >> 1)) &= ~(0x0f << ((block & 0x01) << 2));
499 return;
500 case 2:
501 *ubh_get_addr (ubh, begin + (block >> 2)) &= ~(0x03 << ((block & 0x03) << 1));
502 return;
503 case 1:
504 *ubh_get_addr (ubh, begin + (block >> 3)) &= ~(0x01 << ((block & 0x07)));
505 return;
509 #define ubh_setblock(ubh,begin,block) _ubh_setblock_(uspi,ubh,begin,block)
510 static inline void _ubh_setblock_(struct ufs_sb_private_info * uspi,
511 struct ufs_buffer_head * ubh, unsigned begin, unsigned block)
513 switch (uspi->s_fpb) {
514 case 8:
515 *ubh_get_addr(ubh, begin + block) = 0xff;
516 return;
517 case 4:
518 *ubh_get_addr(ubh, begin + (block >> 1)) |= (0x0f << ((block & 0x01) << 2));
519 return;
520 case 2:
521 *ubh_get_addr(ubh, begin + (block >> 2)) |= (0x03 << ((block & 0x03) << 1));
522 return;
523 case 1:
524 *ubh_get_addr(ubh, begin + (block >> 3)) |= (0x01 << ((block & 0x07)));
525 return;
529 static inline void ufs_fragacct (struct super_block * sb, unsigned blockmap,
530 __fs32 * fraglist, int cnt)
532 struct ufs_sb_private_info * uspi;
533 unsigned fragsize, pos;
535 uspi = UFS_SB(sb)->s_uspi;
537 fragsize = 0;
538 for (pos = 0; pos < uspi->s_fpb; pos++) {
539 if (blockmap & (1 << pos)) {
540 fragsize++;
542 else if (fragsize > 0) {
543 fs32_add(sb, &fraglist[fragsize], cnt);
544 fragsize = 0;
547 if (fragsize > 0 && fragsize < uspi->s_fpb)
548 fs32_add(sb, &fraglist[fragsize], cnt);
551 static inline void *ufs_get_direct_data_ptr(struct ufs_sb_private_info *uspi,
552 struct ufs_inode_info *ufsi,
553 unsigned blk)
555 BUG_ON(blk > UFS_TIND_BLOCK);
556 return uspi->fs_magic == UFS2_MAGIC ?
557 (void *)&ufsi->i_u1.u2_i_data[blk] :
558 (void *)&ufsi->i_u1.i_data[blk];
561 static inline u64 ufs_data_ptr_to_cpu(struct super_block *sb, void *p)
563 return UFS_SB(sb)->s_uspi->fs_magic == UFS2_MAGIC ?
564 fs64_to_cpu(sb, *(__fs64 *)p) :
565 fs32_to_cpu(sb, *(__fs32 *)p);
568 static inline void ufs_cpu_to_data_ptr(struct super_block *sb, void *p, u64 val)
570 if (UFS_SB(sb)->s_uspi->fs_magic == UFS2_MAGIC)
571 *(__fs64 *)p = cpu_to_fs64(sb, val);
572 else
573 *(__fs32 *)p = cpu_to_fs32(sb, val);
576 static inline void ufs_data_ptr_clear(struct ufs_sb_private_info *uspi,
577 void *p)
579 if (uspi->fs_magic == UFS2_MAGIC)
580 *(__fs64 *)p = 0;
581 else
582 *(__fs32 *)p = 0;
585 static inline int ufs_is_data_ptr_zero(struct ufs_sb_private_info *uspi,
586 void *p)
588 if (uspi->fs_magic == UFS2_MAGIC)
589 return *(__fs64 *)p == 0;
590 else
591 return *(__fs32 *)p == 0;
594 static inline __fs32 ufs_get_seconds(struct super_block *sbp)
596 time64_t now = ktime_get_real_seconds();
598 /* Signed 32-bit interpretation wraps around in 2038, which
599 * happens in ufs1 inode stamps but not ufs2 using 64-bits
600 * stamps. For superblock and blockgroup, let's assume
601 * unsigned 32-bit stamps, which are good until y2106.
602 * Wrap around rather than clamp here to make the dirty
603 * file system detection work in the superblock stamp.
605 return cpu_to_fs32(sbp, lower_32_bits(now));