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TOMOYO Linux Cross Reference
Linux/fs/xfs/xfs_rtalloc.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * Copyright (c) 2000-2005 Silicon Graphics, Inc.
  4  * All Rights Reserved.
  5  */
  6 #include "xfs.h"
  7 #include "xfs_fs.h"
  8 #include "xfs_shared.h"
  9 #include "xfs_format.h"
 10 #include "xfs_log_format.h"
 11 #include "xfs_trans_resv.h"
 12 #include "xfs_bit.h"
 13 #include "xfs_mount.h"
 14 #include "xfs_inode.h"
 15 #include "xfs_bmap.h"
 16 #include "xfs_bmap_btree.h"
 17 #include "xfs_trans.h"
 18 #include "xfs_trans_space.h"
 19 #include "xfs_icache.h"
 20 #include "xfs_rtalloc.h"
 21 
 22 
 23 /*
 24  * Read and return the summary information for a given extent size,
 25  * bitmap block combination.
 26  * Keeps track of a current summary block, so we don't keep reading
 27  * it from the buffer cache.
 28  */
 29 static int
 30 xfs_rtget_summary(
 31         xfs_mount_t     *mp,            /* file system mount structure */
 32         xfs_trans_t     *tp,            /* transaction pointer */
 33         int             log,            /* log2 of extent size */
 34         xfs_rtblock_t   bbno,           /* bitmap block number */
 35         xfs_buf_t       **rbpp,         /* in/out: summary block buffer */
 36         xfs_fsblock_t   *rsb,           /* in/out: summary block number */
 37         xfs_suminfo_t   *sum)           /* out: summary info for this block */
 38 {
 39         return xfs_rtmodify_summary_int(mp, tp, log, bbno, 0, rbpp, rsb, sum);
 40 }
 41 
 42 /*
 43  * Return whether there are any free extents in the size range given
 44  * by low and high, for the bitmap block bbno.
 45  */
 46 STATIC int                              /* error */
 47 xfs_rtany_summary(
 48         xfs_mount_t     *mp,            /* file system mount structure */
 49         xfs_trans_t     *tp,            /* transaction pointer */
 50         int             low,            /* low log2 extent size */
 51         int             high,           /* high log2 extent size */
 52         xfs_rtblock_t   bbno,           /* bitmap block number */
 53         xfs_buf_t       **rbpp,         /* in/out: summary block buffer */
 54         xfs_fsblock_t   *rsb,           /* in/out: summary block number */
 55         int             *stat)          /* out: any good extents here? */
 56 {
 57         int             error;          /* error value */
 58         int             log;            /* loop counter, log2 of ext. size */
 59         xfs_suminfo_t   sum;            /* summary data */
 60 
 61         /* There are no extents at levels < m_rsum_cache[bbno]. */
 62         if (mp->m_rsum_cache && low < mp->m_rsum_cache[bbno])
 63                 low = mp->m_rsum_cache[bbno];
 64 
 65         /*
 66          * Loop over logs of extent sizes.
 67          */
 68         for (log = low; log <= high; log++) {
 69                 /*
 70                  * Get one summary datum.
 71                  */
 72                 error = xfs_rtget_summary(mp, tp, log, bbno, rbpp, rsb, &sum);
 73                 if (error) {
 74                         return error;
 75                 }
 76                 /*
 77                  * If there are any, return success.
 78                  */
 79                 if (sum) {
 80                         *stat = 1;
 81                         goto out;
 82                 }
 83         }
 84         /*
 85          * Found nothing, return failure.
 86          */
 87         *stat = 0;
 88 out:
 89         /* There were no extents at levels < log. */
 90         if (mp->m_rsum_cache && log > mp->m_rsum_cache[bbno])
 91                 mp->m_rsum_cache[bbno] = log;
 92         return 0;
 93 }
 94 
 95 
 96 /*
 97  * Copy and transform the summary file, given the old and new
 98  * parameters in the mount structures.
 99  */
100 STATIC int                              /* error */
101 xfs_rtcopy_summary(
102         xfs_mount_t     *omp,           /* old file system mount point */
103         xfs_mount_t     *nmp,           /* new file system mount point */
104         xfs_trans_t     *tp)            /* transaction pointer */
105 {
106         xfs_rtblock_t   bbno;           /* bitmap block number */
107         xfs_buf_t       *bp;            /* summary buffer */
108         int             error;          /* error return value */
109         int             log;            /* summary level number (log length) */
110         xfs_suminfo_t   sum;            /* summary data */
111         xfs_fsblock_t   sumbno;         /* summary block number */
112 
113         bp = NULL;
114         for (log = omp->m_rsumlevels - 1; log >= 0; log--) {
115                 for (bbno = omp->m_sb.sb_rbmblocks - 1;
116                      (xfs_srtblock_t)bbno >= 0;
117                      bbno--) {
118                         error = xfs_rtget_summary(omp, tp, log, bbno, &bp,
119                                 &sumbno, &sum);
120                         if (error)
121                                 return error;
122                         if (sum == 0)
123                                 continue;
124                         error = xfs_rtmodify_summary(omp, tp, log, bbno, -sum,
125                                 &bp, &sumbno);
126                         if (error)
127                                 return error;
128                         error = xfs_rtmodify_summary(nmp, tp, log, bbno, sum,
129                                 &bp, &sumbno);
130                         if (error)
131                                 return error;
132                         ASSERT(sum > 0);
133                 }
134         }
135         return 0;
136 }
137 /*
138  * Mark an extent specified by start and len allocated.
139  * Updates all the summary information as well as the bitmap.
140  */
141 STATIC int                              /* error */
142 xfs_rtallocate_range(
143         xfs_mount_t     *mp,            /* file system mount point */
144         xfs_trans_t     *tp,            /* transaction pointer */
145         xfs_rtblock_t   start,          /* start block to allocate */
146         xfs_extlen_t    len,            /* length to allocate */
147         xfs_buf_t       **rbpp,         /* in/out: summary block buffer */
148         xfs_fsblock_t   *rsb)           /* in/out: summary block number */
149 {
150         xfs_rtblock_t   end;            /* end of the allocated extent */
151         int             error;          /* error value */
152         xfs_rtblock_t   postblock = 0;  /* first block allocated > end */
153         xfs_rtblock_t   preblock = 0;   /* first block allocated < start */
154 
155         end = start + len - 1;
156         /*
157          * Assume we're allocating out of the middle of a free extent.
158          * We need to find the beginning and end of the extent so we can
159          * properly update the summary.
160          */
161         error = xfs_rtfind_back(mp, tp, start, 0, &preblock);
162         if (error) {
163                 return error;
164         }
165         /*
166          * Find the next allocated block (end of free extent).
167          */
168         error = xfs_rtfind_forw(mp, tp, end, mp->m_sb.sb_rextents - 1,
169                 &postblock);
170         if (error) {
171                 return error;
172         }
173         /*
174          * Decrement the summary information corresponding to the entire
175          * (old) free extent.
176          */
177         error = xfs_rtmodify_summary(mp, tp,
178                 XFS_RTBLOCKLOG(postblock + 1 - preblock),
179                 XFS_BITTOBLOCK(mp, preblock), -1, rbpp, rsb);
180         if (error) {
181                 return error;
182         }
183         /*
184          * If there are blocks not being allocated at the front of the
185          * old extent, add summary data for them to be free.
186          */
187         if (preblock < start) {
188                 error = xfs_rtmodify_summary(mp, tp,
189                         XFS_RTBLOCKLOG(start - preblock),
190                         XFS_BITTOBLOCK(mp, preblock), 1, rbpp, rsb);
191                 if (error) {
192                         return error;
193                 }
194         }
195         /*
196          * If there are blocks not being allocated at the end of the
197          * old extent, add summary data for them to be free.
198          */
199         if (postblock > end) {
200                 error = xfs_rtmodify_summary(mp, tp,
201                         XFS_RTBLOCKLOG(postblock - end),
202                         XFS_BITTOBLOCK(mp, end + 1), 1, rbpp, rsb);
203                 if (error) {
204                         return error;
205                 }
206         }
207         /*
208          * Modify the bitmap to mark this extent allocated.
209          */
210         error = xfs_rtmodify_range(mp, tp, start, len, 0);
211         return error;
212 }
213 
214 /*
215  * Attempt to allocate an extent minlen<=len<=maxlen starting from
216  * bitmap block bbno.  If we don't get maxlen then use prod to trim
217  * the length, if given.  Returns error; returns starting block in *rtblock.
218  * The lengths are all in rtextents.
219  */
220 STATIC int                              /* error */
221 xfs_rtallocate_extent_block(
222         xfs_mount_t     *mp,            /* file system mount point */
223         xfs_trans_t     *tp,            /* transaction pointer */
224         xfs_rtblock_t   bbno,           /* bitmap block number */
225         xfs_extlen_t    minlen,         /* minimum length to allocate */
226         xfs_extlen_t    maxlen,         /* maximum length to allocate */
227         xfs_extlen_t    *len,           /* out: actual length allocated */
228         xfs_rtblock_t   *nextp,         /* out: next block to try */
229         xfs_buf_t       **rbpp,         /* in/out: summary block buffer */
230         xfs_fsblock_t   *rsb,           /* in/out: summary block number */
231         xfs_extlen_t    prod,           /* extent product factor */
232         xfs_rtblock_t   *rtblock)       /* out: start block allocated */
233 {
234         xfs_rtblock_t   besti;          /* best rtblock found so far */
235         xfs_rtblock_t   bestlen;        /* best length found so far */
236         xfs_rtblock_t   end;            /* last rtblock in chunk */
237         int             error;          /* error value */
238         xfs_rtblock_t   i;              /* current rtblock trying */
239         xfs_rtblock_t   next;           /* next rtblock to try */
240         int             stat;           /* status from internal calls */
241 
242         /*
243          * Loop over all the extents starting in this bitmap block,
244          * looking for one that's long enough.
245          */
246         for (i = XFS_BLOCKTOBIT(mp, bbno), besti = -1, bestlen = 0,
247                 end = XFS_BLOCKTOBIT(mp, bbno + 1) - 1;
248              i <= end;
249              i++) {
250                 /*
251                  * See if there's a free extent of maxlen starting at i.
252                  * If it's not so then next will contain the first non-free.
253                  */
254                 error = xfs_rtcheck_range(mp, tp, i, maxlen, 1, &next, &stat);
255                 if (error) {
256                         return error;
257                 }
258                 if (stat) {
259                         /*
260                          * i for maxlen is all free, allocate and return that.
261                          */
262                         error = xfs_rtallocate_range(mp, tp, i, maxlen, rbpp,
263                                 rsb);
264                         if (error) {
265                                 return error;
266                         }
267                         *len = maxlen;
268                         *rtblock = i;
269                         return 0;
270                 }
271                 /*
272                  * In the case where we have a variable-sized allocation
273                  * request, figure out how big this free piece is,
274                  * and if it's big enough for the minimum, and the best
275                  * so far, remember it.
276                  */
277                 if (minlen < maxlen) {
278                         xfs_rtblock_t   thislen;        /* this extent size */
279 
280                         thislen = next - i;
281                         if (thislen >= minlen && thislen > bestlen) {
282                                 besti = i;
283                                 bestlen = thislen;
284                         }
285                 }
286                 /*
287                  * If not done yet, find the start of the next free space.
288                  */
289                 if (next < end) {
290                         error = xfs_rtfind_forw(mp, tp, next, end, &i);
291                         if (error) {
292                                 return error;
293                         }
294                 } else
295                         break;
296         }
297         /*
298          * Searched the whole thing & didn't find a maxlen free extent.
299          */
300         if (minlen < maxlen && besti != -1) {
301                 xfs_extlen_t    p;      /* amount to trim length by */
302 
303                 /*
304                  * If size should be a multiple of prod, make that so.
305                  */
306                 if (prod > 1) {
307                         div_u64_rem(bestlen, prod, &p);
308                         if (p)
309                                 bestlen -= p;
310                 }
311 
312                 /*
313                  * Allocate besti for bestlen & return that.
314                  */
315                 error = xfs_rtallocate_range(mp, tp, besti, bestlen, rbpp, rsb);
316                 if (error) {
317                         return error;
318                 }
319                 *len = bestlen;
320                 *rtblock = besti;
321                 return 0;
322         }
323         /*
324          * Allocation failed.  Set *nextp to the next block to try.
325          */
326         *nextp = next;
327         *rtblock = NULLRTBLOCK;
328         return 0;
329 }
330 
331 /*
332  * Allocate an extent of length minlen<=len<=maxlen, starting at block
333  * bno.  If we don't get maxlen then use prod to trim the length, if given.
334  * Returns error; returns starting block in *rtblock.
335  * The lengths are all in rtextents.
336  */
337 STATIC int                              /* error */
338 xfs_rtallocate_extent_exact(
339         xfs_mount_t     *mp,            /* file system mount point */
340         xfs_trans_t     *tp,            /* transaction pointer */
341         xfs_rtblock_t   bno,            /* starting block number to allocate */
342         xfs_extlen_t    minlen,         /* minimum length to allocate */
343         xfs_extlen_t    maxlen,         /* maximum length to allocate */
344         xfs_extlen_t    *len,           /* out: actual length allocated */
345         xfs_buf_t       **rbpp,         /* in/out: summary block buffer */
346         xfs_fsblock_t   *rsb,           /* in/out: summary block number */
347         xfs_extlen_t    prod,           /* extent product factor */
348         xfs_rtblock_t   *rtblock)       /* out: start block allocated */
349 {
350         int             error;          /* error value */
351         xfs_extlen_t    i;              /* extent length trimmed due to prod */
352         int             isfree;         /* extent is free */
353         xfs_rtblock_t   next;           /* next block to try (dummy) */
354 
355         ASSERT(minlen % prod == 0 && maxlen % prod == 0);
356         /*
357          * Check if the range in question (for maxlen) is free.
358          */
359         error = xfs_rtcheck_range(mp, tp, bno, maxlen, 1, &next, &isfree);
360         if (error) {
361                 return error;
362         }
363         if (isfree) {
364                 /*
365                  * If it is, allocate it and return success.
366                  */
367                 error = xfs_rtallocate_range(mp, tp, bno, maxlen, rbpp, rsb);
368                 if (error) {
369                         return error;
370                 }
371                 *len = maxlen;
372                 *rtblock = bno;
373                 return 0;
374         }
375         /*
376          * If not, allocate what there is, if it's at least minlen.
377          */
378         maxlen = next - bno;
379         if (maxlen < minlen) {
380                 /*
381                  * Failed, return failure status.
382                  */
383                 *rtblock = NULLRTBLOCK;
384                 return 0;
385         }
386         /*
387          * Trim off tail of extent, if prod is specified.
388          */
389         if (prod > 1 && (i = maxlen % prod)) {
390                 maxlen -= i;
391                 if (maxlen < minlen) {
392                         /*
393                          * Now we can't do it, return failure status.
394                          */
395                         *rtblock = NULLRTBLOCK;
396                         return 0;
397                 }
398         }
399         /*
400          * Allocate what we can and return it.
401          */
402         error = xfs_rtallocate_range(mp, tp, bno, maxlen, rbpp, rsb);
403         if (error) {
404                 return error;
405         }
406         *len = maxlen;
407         *rtblock = bno;
408         return 0;
409 }
410 
411 /*
412  * Allocate an extent of length minlen<=len<=maxlen, starting as near
413  * to bno as possible.  If we don't get maxlen then use prod to trim
414  * the length, if given.  The lengths are all in rtextents.
415  */
416 STATIC int                              /* error */
417 xfs_rtallocate_extent_near(
418         xfs_mount_t     *mp,            /* file system mount point */
419         xfs_trans_t     *tp,            /* transaction pointer */
420         xfs_rtblock_t   bno,            /* starting block number to allocate */
421         xfs_extlen_t    minlen,         /* minimum length to allocate */
422         xfs_extlen_t    maxlen,         /* maximum length to allocate */
423         xfs_extlen_t    *len,           /* out: actual length allocated */
424         xfs_buf_t       **rbpp,         /* in/out: summary block buffer */
425         xfs_fsblock_t   *rsb,           /* in/out: summary block number */
426         xfs_extlen_t    prod,           /* extent product factor */
427         xfs_rtblock_t   *rtblock)       /* out: start block allocated */
428 {
429         int             any;            /* any useful extents from summary */
430         xfs_rtblock_t   bbno;           /* bitmap block number */
431         int             error;          /* error value */
432         int             i;              /* bitmap block offset (loop control) */
433         int             j;              /* secondary loop control */
434         int             log2len;        /* log2 of minlen */
435         xfs_rtblock_t   n;              /* next block to try */
436         xfs_rtblock_t   r;              /* result block */
437 
438         ASSERT(minlen % prod == 0 && maxlen % prod == 0);
439         /*
440          * If the block number given is off the end, silently set it to
441          * the last block.
442          */
443         if (bno >= mp->m_sb.sb_rextents)
444                 bno = mp->m_sb.sb_rextents - 1;
445         /*
446          * Try the exact allocation first.
447          */
448         error = xfs_rtallocate_extent_exact(mp, tp, bno, minlen, maxlen, len,
449                 rbpp, rsb, prod, &r);
450         if (error) {
451                 return error;
452         }
453         /*
454          * If the exact allocation worked, return that.
455          */
456         if (r != NULLRTBLOCK) {
457                 *rtblock = r;
458                 return 0;
459         }
460         bbno = XFS_BITTOBLOCK(mp, bno);
461         i = 0;
462         ASSERT(minlen != 0);
463         log2len = xfs_highbit32(minlen);
464         /*
465          * Loop over all bitmap blocks (bbno + i is current block).
466          */
467         for (;;) {
468                 /*
469                  * Get summary information of extents of all useful levels
470                  * starting in this bitmap block.
471                  */
472                 error = xfs_rtany_summary(mp, tp, log2len, mp->m_rsumlevels - 1,
473                         bbno + i, rbpp, rsb, &any);
474                 if (error) {
475                         return error;
476                 }
477                 /*
478                  * If there are any useful extents starting here, try
479                  * allocating one.
480                  */
481                 if (any) {
482                         /*
483                          * On the positive side of the starting location.
484                          */
485                         if (i >= 0) {
486                                 /*
487                                  * Try to allocate an extent starting in
488                                  * this block.
489                                  */
490                                 error = xfs_rtallocate_extent_block(mp, tp,
491                                         bbno + i, minlen, maxlen, len, &n, rbpp,
492                                         rsb, prod, &r);
493                                 if (error) {
494                                         return error;
495                                 }
496                                 /*
497                                  * If it worked, return it.
498                                  */
499                                 if (r != NULLRTBLOCK) {
500                                         *rtblock = r;
501                                         return 0;
502                                 }
503                         }
504                         /*
505                          * On the negative side of the starting location.
506                          */
507                         else {          /* i < 0 */
508                                 /*
509                                  * Loop backwards through the bitmap blocks from
510                                  * the starting point-1 up to where we are now.
511                                  * There should be an extent which ends in this
512                                  * bitmap block and is long enough.
513                                  */
514                                 for (j = -1; j > i; j--) {
515                                         /*
516                                          * Grab the summary information for
517                                          * this bitmap block.
518                                          */
519                                         error = xfs_rtany_summary(mp, tp,
520                                                 log2len, mp->m_rsumlevels - 1,
521                                                 bbno + j, rbpp, rsb, &any);
522                                         if (error) {
523                                                 return error;
524                                         }
525                                         /*
526                                          * If there's no extent given in the
527                                          * summary that means the extent we
528                                          * found must carry over from an
529                                          * earlier block.  If there is an
530                                          * extent given, we've already tried
531                                          * that allocation, don't do it again.
532                                          */
533                                         if (any)
534                                                 continue;
535                                         error = xfs_rtallocate_extent_block(mp,
536                                                 tp, bbno + j, minlen, maxlen,
537                                                 len, &n, rbpp, rsb, prod, &r);
538                                         if (error) {
539                                                 return error;
540                                         }
541                                         /*
542                                          * If it works, return the extent.
543                                          */
544                                         if (r != NULLRTBLOCK) {
545                                                 *rtblock = r;
546                                                 return 0;
547                                         }
548                                 }
549                                 /*
550                                  * There weren't intervening bitmap blocks
551                                  * with a long enough extent, or the
552                                  * allocation didn't work for some reason
553                                  * (i.e. it's a little * too short).
554                                  * Try to allocate from the summary block
555                                  * that we found.
556                                  */
557                                 error = xfs_rtallocate_extent_block(mp, tp,
558                                         bbno + i, minlen, maxlen, len, &n, rbpp,
559                                         rsb, prod, &r);
560                                 if (error) {
561                                         return error;
562                                 }
563                                 /*
564                                  * If it works, return the extent.
565                                  */
566                                 if (r != NULLRTBLOCK) {
567                                         *rtblock = r;
568                                         return 0;
569                                 }
570                         }
571                 }
572                 /*
573                  * Loop control.  If we were on the positive side, and there's
574                  * still more blocks on the negative side, go there.
575                  */
576                 if (i > 0 && (int)bbno - i >= 0)
577                         i = -i;
578                 /*
579                  * If positive, and no more negative, but there are more
580                  * positive, go there.
581                  */
582                 else if (i > 0 && (int)bbno + i < mp->m_sb.sb_rbmblocks - 1)
583                         i++;
584                 /*
585                  * If negative or 0 (just started), and there are positive
586                  * blocks to go, go there.  The 0 case moves to block 1.
587                  */
588                 else if (i <= 0 && (int)bbno - i < mp->m_sb.sb_rbmblocks - 1)
589                         i = 1 - i;
590                 /*
591                  * If negative or 0 and there are more negative blocks,
592                  * go there.
593                  */
594                 else if (i <= 0 && (int)bbno + i > 0)
595                         i--;
596                 /*
597                  * Must be done.  Return failure.
598                  */
599                 else
600                         break;
601         }
602         *rtblock = NULLRTBLOCK;
603         return 0;
604 }
605 
606 /*
607  * Allocate an extent of length minlen<=len<=maxlen, with no position
608  * specified.  If we don't get maxlen then use prod to trim
609  * the length, if given.  The lengths are all in rtextents.
610  */
611 STATIC int                              /* error */
612 xfs_rtallocate_extent_size(
613         xfs_mount_t     *mp,            /* file system mount point */
614         xfs_trans_t     *tp,            /* transaction pointer */
615         xfs_extlen_t    minlen,         /* minimum length to allocate */
616         xfs_extlen_t    maxlen,         /* maximum length to allocate */
617         xfs_extlen_t    *len,           /* out: actual length allocated */
618         xfs_buf_t       **rbpp,         /* in/out: summary block buffer */
619         xfs_fsblock_t   *rsb,           /* in/out: summary block number */
620         xfs_extlen_t    prod,           /* extent product factor */
621         xfs_rtblock_t   *rtblock)       /* out: start block allocated */
622 {
623         int             error;          /* error value */
624         int             i;              /* bitmap block number */
625         int             l;              /* level number (loop control) */
626         xfs_rtblock_t   n;              /* next block to be tried */
627         xfs_rtblock_t   r;              /* result block number */
628         xfs_suminfo_t   sum;            /* summary information for extents */
629 
630         ASSERT(minlen % prod == 0 && maxlen % prod == 0);
631         ASSERT(maxlen != 0);
632 
633         /*
634          * Loop over all the levels starting with maxlen.
635          * At each level, look at all the bitmap blocks, to see if there
636          * are extents starting there that are long enough (>= maxlen).
637          * Note, only on the initial level can the allocation fail if
638          * the summary says there's an extent.
639          */
640         for (l = xfs_highbit32(maxlen); l < mp->m_rsumlevels; l++) {
641                 /*
642                  * Loop over all the bitmap blocks.
643                  */
644                 for (i = 0; i < mp->m_sb.sb_rbmblocks; i++) {
645                         /*
646                          * Get the summary for this level/block.
647                          */
648                         error = xfs_rtget_summary(mp, tp, l, i, rbpp, rsb,
649                                 &sum);
650                         if (error) {
651                                 return error;
652                         }
653                         /*
654                          * Nothing there, on to the next block.
655                          */
656                         if (!sum)
657                                 continue;
658                         /*
659                          * Try allocating the extent.
660                          */
661                         error = xfs_rtallocate_extent_block(mp, tp, i, maxlen,
662                                 maxlen, len, &n, rbpp, rsb, prod, &r);
663                         if (error) {
664                                 return error;
665                         }
666                         /*
667                          * If it worked, return that.
668                          */
669                         if (r != NULLRTBLOCK) {
670                                 *rtblock = r;
671                                 return 0;
672                         }
673                         /*
674                          * If the "next block to try" returned from the
675                          * allocator is beyond the next bitmap block,
676                          * skip to that bitmap block.
677                          */
678                         if (XFS_BITTOBLOCK(mp, n) > i + 1)
679                                 i = XFS_BITTOBLOCK(mp, n) - 1;
680                 }
681         }
682         /*
683          * Didn't find any maxlen blocks.  Try smaller ones, unless
684          * we're asking for a fixed size extent.
685          */
686         if (minlen > --maxlen) {
687                 *rtblock = NULLRTBLOCK;
688                 return 0;
689         }
690         ASSERT(minlen != 0);
691         ASSERT(maxlen != 0);
692 
693         /*
694          * Loop over sizes, from maxlen down to minlen.
695          * This time, when we do the allocations, allow smaller ones
696          * to succeed.
697          */
698         for (l = xfs_highbit32(maxlen); l >= xfs_highbit32(minlen); l--) {
699                 /*
700                  * Loop over all the bitmap blocks, try an allocation
701                  * starting in that block.
702                  */
703                 for (i = 0; i < mp->m_sb.sb_rbmblocks; i++) {
704                         /*
705                          * Get the summary information for this level/block.
706                          */
707                         error = xfs_rtget_summary(mp, tp, l, i, rbpp, rsb,
708                                                   &sum);
709                         if (error) {
710                                 return error;
711                         }
712                         /*
713                          * If nothing there, go on to next.
714                          */
715                         if (!sum)
716                                 continue;
717                         /*
718                          * Try the allocation.  Make sure the specified
719                          * minlen/maxlen are in the possible range for
720                          * this summary level.
721                          */
722                         error = xfs_rtallocate_extent_block(mp, tp, i,
723                                         XFS_RTMAX(minlen, 1 << l),
724                                         XFS_RTMIN(maxlen, (1 << (l + 1)) - 1),
725                                         len, &n, rbpp, rsb, prod, &r);
726                         if (error) {
727                                 return error;
728                         }
729                         /*
730                          * If it worked, return that extent.
731                          */
732                         if (r != NULLRTBLOCK) {
733                                 *rtblock = r;
734                                 return 0;
735                         }
736                         /*
737                          * If the "next block to try" returned from the
738                          * allocator is beyond the next bitmap block,
739                          * skip to that bitmap block.
740                          */
741                         if (XFS_BITTOBLOCK(mp, n) > i + 1)
742                                 i = XFS_BITTOBLOCK(mp, n) - 1;
743                 }
744         }
745         /*
746          * Got nothing, return failure.
747          */
748         *rtblock = NULLRTBLOCK;
749         return 0;
750 }
751 
752 /*
753  * Allocate space to the bitmap or summary file, and zero it, for growfs.
754  */
755 STATIC int
756 xfs_growfs_rt_alloc(
757         struct xfs_mount        *mp,            /* file system mount point */
758         xfs_extlen_t            oblocks,        /* old count of blocks */
759         xfs_extlen_t            nblocks,        /* new count of blocks */
760         struct xfs_inode        *ip)            /* inode (bitmap/summary) */
761 {
762         xfs_fileoff_t           bno;            /* block number in file */
763         struct xfs_buf          *bp;    /* temporary buffer for zeroing */
764         xfs_daddr_t             d;              /* disk block address */
765         int                     error;          /* error return value */
766         xfs_fsblock_t           fsbno;          /* filesystem block for bno */
767         struct xfs_bmbt_irec    map;            /* block map output */
768         int                     nmap;           /* number of block maps */
769         int                     resblks;        /* space reservation */
770         struct xfs_trans        *tp;
771 
772         /*
773          * Allocate space to the file, as necessary.
774          */
775         while (oblocks < nblocks) {
776                 resblks = XFS_GROWFSRT_SPACE_RES(mp, nblocks - oblocks);
777                 /*
778                  * Reserve space & log for one extent added to the file.
779                  */
780                 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_growrtalloc, resblks,
781                                 0, 0, &tp);
782                 if (error)
783                         return error;
784                 /*
785                  * Lock the inode.
786                  */
787                 xfs_ilock(ip, XFS_ILOCK_EXCL);
788                 xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
789 
790                 /*
791                  * Allocate blocks to the bitmap file.
792                  */
793                 nmap = 1;
794                 error = xfs_bmapi_write(tp, ip, oblocks, nblocks - oblocks,
795                                         XFS_BMAPI_METADATA, resblks, &map,
796                                         &nmap);
797                 if (!error && nmap < 1)
798                         error = -ENOSPC;
799                 if (error)
800                         goto out_trans_cancel;
801                 /*
802                  * Free any blocks freed up in the transaction, then commit.
803                  */
804                 error = xfs_trans_commit(tp);
805                 if (error)
806                         return error;
807                 /*
808                  * Now we need to clear the allocated blocks.
809                  * Do this one block per transaction, to keep it simple.
810                  */
811                 for (bno = map.br_startoff, fsbno = map.br_startblock;
812                      bno < map.br_startoff + map.br_blockcount;
813                      bno++, fsbno++) {
814                         /*
815                          * Reserve log for one block zeroing.
816                          */
817                         error = xfs_trans_alloc(mp, &M_RES(mp)->tr_growrtzero,
818                                         0, 0, 0, &tp);
819                         if (error)
820                                 return error;
821                         /*
822                          * Lock the bitmap inode.
823                          */
824                         xfs_ilock(ip, XFS_ILOCK_EXCL);
825                         xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
826                         /*
827                          * Get a buffer for the block.
828                          */
829                         d = XFS_FSB_TO_DADDR(mp, fsbno);
830                         bp = xfs_trans_get_buf(tp, mp->m_ddev_targp, d,
831                                 mp->m_bsize, 0);
832                         if (bp == NULL) {
833                                 error = -EIO;
834                                 goto out_trans_cancel;
835                         }
836                         memset(bp->b_addr, 0, mp->m_sb.sb_blocksize);
837                         xfs_trans_log_buf(tp, bp, 0, mp->m_sb.sb_blocksize - 1);
838                         /*
839                          * Commit the transaction.
840                          */
841                         error = xfs_trans_commit(tp);
842                         if (error)
843                                 return error;
844                 }
845                 /*
846                  * Go on to the next extent, if any.
847                  */
848                 oblocks = map.br_startoff + map.br_blockcount;
849         }
850 
851         return 0;
852 
853 out_trans_cancel:
854         xfs_trans_cancel(tp);
855         return error;
856 }
857 
858 static void
859 xfs_alloc_rsum_cache(
860         xfs_mount_t     *mp,            /* file system mount structure */
861         xfs_extlen_t    rbmblocks)      /* number of rt bitmap blocks */
862 {
863         /*
864          * The rsum cache is initialized to all zeroes, which is trivially a
865          * lower bound on the minimum level with any free extents. We can
866          * continue without the cache if it couldn't be allocated.
867          */
868         mp->m_rsum_cache = kmem_zalloc_large(rbmblocks, KM_SLEEP);
869         if (!mp->m_rsum_cache)
870                 xfs_warn(mp, "could not allocate realtime summary cache");
871 }
872 
873 /*
874  * Visible (exported) functions.
875  */
876 
877 /*
878  * Grow the realtime area of the filesystem.
879  */
880 int
881 xfs_growfs_rt(
882         xfs_mount_t     *mp,            /* mount point for filesystem */
883         xfs_growfs_rt_t *in)            /* growfs rt input struct */
884 {
885         xfs_rtblock_t   bmbno;          /* bitmap block number */
886         xfs_buf_t       *bp;            /* temporary buffer */
887         int             error;          /* error return value */
888         xfs_mount_t     *nmp;           /* new (fake) mount structure */
889         xfs_rfsblock_t  nrblocks;       /* new number of realtime blocks */
890         xfs_extlen_t    nrbmblocks;     /* new number of rt bitmap blocks */
891         xfs_rtblock_t   nrextents;      /* new number of realtime extents */
892         uint8_t         nrextslog;      /* new log2 of sb_rextents */
893         xfs_extlen_t    nrsumblocks;    /* new number of summary blocks */
894         uint            nrsumlevels;    /* new rt summary levels */
895         uint            nrsumsize;      /* new size of rt summary, bytes */
896         xfs_sb_t        *nsbp;          /* new superblock */
897         xfs_extlen_t    rbmblocks;      /* current number of rt bitmap blocks */
898         xfs_extlen_t    rsumblocks;     /* current number of rt summary blks */
899         xfs_sb_t        *sbp;           /* old superblock */
900         xfs_fsblock_t   sumbno;         /* summary block number */
901         uint8_t         *rsum_cache;    /* old summary cache */
902 
903         sbp = &mp->m_sb;
904         /*
905          * Initial error checking.
906          */
907         if (!capable(CAP_SYS_ADMIN))
908                 return -EPERM;
909         if (mp->m_rtdev_targp == NULL || mp->m_rbmip == NULL ||
910             (nrblocks = in->newblocks) <= sbp->sb_rblocks ||
911             (sbp->sb_rblocks && (in->extsize != sbp->sb_rextsize)))
912                 return -EINVAL;
913         if ((error = xfs_sb_validate_fsb_count(sbp, nrblocks)))
914                 return error;
915         /*
916          * Read in the last block of the device, make sure it exists.
917          */
918         error = xfs_buf_read_uncached(mp->m_rtdev_targp,
919                                 XFS_FSB_TO_BB(mp, nrblocks - 1),
920                                 XFS_FSB_TO_BB(mp, 1), 0, &bp, NULL);
921         if (error)
922                 return error;
923         xfs_buf_relse(bp);
924 
925         /*
926          * Calculate new parameters.  These are the final values to be reached.
927          */
928         nrextents = nrblocks;
929         do_div(nrextents, in->extsize);
930         nrbmblocks = howmany_64(nrextents, NBBY * sbp->sb_blocksize);
931         nrextslog = xfs_highbit32(nrextents);
932         nrsumlevels = nrextslog + 1;
933         nrsumsize = (uint)sizeof(xfs_suminfo_t) * nrsumlevels * nrbmblocks;
934         nrsumblocks = XFS_B_TO_FSB(mp, nrsumsize);
935         nrsumsize = XFS_FSB_TO_B(mp, nrsumblocks);
936         /*
937          * New summary size can't be more than half the size of
938          * the log.  This prevents us from getting a log overflow,
939          * since we'll log basically the whole summary file at once.
940          */
941         if (nrsumblocks > (mp->m_sb.sb_logblocks >> 1))
942                 return -EINVAL;
943         /*
944          * Get the old block counts for bitmap and summary inodes.
945          * These can't change since other growfs callers are locked out.
946          */
947         rbmblocks = XFS_B_TO_FSB(mp, mp->m_rbmip->i_d.di_size);
948         rsumblocks = XFS_B_TO_FSB(mp, mp->m_rsumip->i_d.di_size);
949         /*
950          * Allocate space to the bitmap and summary files, as necessary.
951          */
952         error = xfs_growfs_rt_alloc(mp, rbmblocks, nrbmblocks, mp->m_rbmip);
953         if (error)
954                 return error;
955         error = xfs_growfs_rt_alloc(mp, rsumblocks, nrsumblocks, mp->m_rsumip);
956         if (error)
957                 return error;
958 
959         rsum_cache = mp->m_rsum_cache;
960         if (nrbmblocks != sbp->sb_rbmblocks)
961                 xfs_alloc_rsum_cache(mp, nrbmblocks);
962 
963         /*
964          * Allocate a new (fake) mount/sb.
965          */
966         nmp = kmem_alloc(sizeof(*nmp), KM_SLEEP);
967         /*
968          * Loop over the bitmap blocks.
969          * We will do everything one bitmap block at a time.
970          * Skip the current block if it is exactly full.
971          * This also deals with the case where there were no rtextents before.
972          */
973         for (bmbno = sbp->sb_rbmblocks -
974                      ((sbp->sb_rextents & ((1 << mp->m_blkbit_log) - 1)) != 0);
975              bmbno < nrbmblocks;
976              bmbno++) {
977                 xfs_trans_t     *tp;
978 
979                 *nmp = *mp;
980                 nsbp = &nmp->m_sb;
981                 /*
982                  * Calculate new sb and mount fields for this round.
983                  */
984                 nsbp->sb_rextsize = in->extsize;
985                 nsbp->sb_rbmblocks = bmbno + 1;
986                 nsbp->sb_rblocks =
987                         XFS_RTMIN(nrblocks,
988                                   nsbp->sb_rbmblocks * NBBY *
989                                   nsbp->sb_blocksize * nsbp->sb_rextsize);
990                 nsbp->sb_rextents = nsbp->sb_rblocks;
991                 do_div(nsbp->sb_rextents, nsbp->sb_rextsize);
992                 ASSERT(nsbp->sb_rextents != 0);
993                 nsbp->sb_rextslog = xfs_highbit32(nsbp->sb_rextents);
994                 nrsumlevels = nmp->m_rsumlevels = nsbp->sb_rextslog + 1;
995                 nrsumsize =
996                         (uint)sizeof(xfs_suminfo_t) * nrsumlevels *
997                         nsbp->sb_rbmblocks;
998                 nrsumblocks = XFS_B_TO_FSB(mp, nrsumsize);
999                 nmp->m_rsumsize = nrsumsize = XFS_FSB_TO_B(mp, nrsumblocks);
1000                 /*
1001                  * Start a transaction, get the log reservation.
1002                  */
1003                 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_growrtfree, 0, 0, 0,
1004                                 &tp);
1005                 if (error)
1006                         break;
1007                 /*
1008                  * Lock out other callers by grabbing the bitmap inode lock.
1009                  */
1010                 xfs_ilock(mp->m_rbmip, XFS_ILOCK_EXCL);
1011                 xfs_trans_ijoin(tp, mp->m_rbmip, XFS_ILOCK_EXCL);
1012                 /*
1013                  * Update the bitmap inode's size.
1014                  */
1015                 mp->m_rbmip->i_d.di_size =
1016                         nsbp->sb_rbmblocks * nsbp->sb_blocksize;
1017                 xfs_trans_log_inode(tp, mp->m_rbmip, XFS_ILOG_CORE);
1018                 /*
1019                  * Get the summary inode into the transaction.
1020                  */
1021                 xfs_ilock(mp->m_rsumip, XFS_ILOCK_EXCL);
1022                 xfs_trans_ijoin(tp, mp->m_rsumip, XFS_ILOCK_EXCL);
1023                 /*
1024                  * Update the summary inode's size.
1025                  */
1026                 mp->m_rsumip->i_d.di_size = nmp->m_rsumsize;
1027                 xfs_trans_log_inode(tp, mp->m_rsumip, XFS_ILOG_CORE);
1028                 /*
1029                  * Copy summary data from old to new sizes.
1030                  * Do this when the real size (not block-aligned) changes.
1031                  */
1032                 if (sbp->sb_rbmblocks != nsbp->sb_rbmblocks ||
1033                     mp->m_rsumlevels != nmp->m_rsumlevels) {
1034                         error = xfs_rtcopy_summary(mp, nmp, tp);
1035                         if (error)
1036                                 goto error_cancel;
1037                 }
1038                 /*
1039                  * Update superblock fields.
1040                  */
1041                 if (nsbp->sb_rextsize != sbp->sb_rextsize)
1042                         xfs_trans_mod_sb(tp, XFS_TRANS_SB_REXTSIZE,
1043                                 nsbp->sb_rextsize - sbp->sb_rextsize);
1044                 if (nsbp->sb_rbmblocks != sbp->sb_rbmblocks)
1045                         xfs_trans_mod_sb(tp, XFS_TRANS_SB_RBMBLOCKS,
1046                                 nsbp->sb_rbmblocks - sbp->sb_rbmblocks);
1047                 if (nsbp->sb_rblocks != sbp->sb_rblocks)
1048                         xfs_trans_mod_sb(tp, XFS_TRANS_SB_RBLOCKS,
1049                                 nsbp->sb_rblocks - sbp->sb_rblocks);
1050                 if (nsbp->sb_rextents != sbp->sb_rextents)
1051                         xfs_trans_mod_sb(tp, XFS_TRANS_SB_REXTENTS,
1052                                 nsbp->sb_rextents - sbp->sb_rextents);
1053                 if (nsbp->sb_rextslog != sbp->sb_rextslog)
1054                         xfs_trans_mod_sb(tp, XFS_TRANS_SB_REXTSLOG,
1055                                 nsbp->sb_rextslog - sbp->sb_rextslog);
1056                 /*
1057                  * Free new extent.
1058                  */
1059                 bp = NULL;
1060                 error = xfs_rtfree_range(nmp, tp, sbp->sb_rextents,
1061                         nsbp->sb_rextents - sbp->sb_rextents, &bp, &sumbno);
1062                 if (error) {
1063 error_cancel:
1064                         xfs_trans_cancel(tp);
1065                         break;
1066                 }
1067                 /*
1068                  * Mark more blocks free in the superblock.
1069                  */
1070                 xfs_trans_mod_sb(tp, XFS_TRANS_SB_FREXTENTS,
1071                         nsbp->sb_rextents - sbp->sb_rextents);
1072                 /*
1073                  * Update mp values into the real mp structure.
1074                  */
1075                 mp->m_rsumlevels = nrsumlevels;
1076                 mp->m_rsumsize = nrsumsize;
1077 
1078                 error = xfs_trans_commit(tp);
1079                 if (error)
1080                         break;
1081         }
1082 
1083         /*
1084          * Free the fake mp structure.
1085          */
1086         kmem_free(nmp);
1087 
1088         /*
1089          * If we had to allocate a new rsum_cache, we either need to free the
1090          * old one (if we succeeded) or free the new one and restore the old one
1091          * (if there was an error).
1092          */
1093         if (rsum_cache != mp->m_rsum_cache) {
1094                 if (error) {
1095                         kmem_free(mp->m_rsum_cache);
1096                         mp->m_rsum_cache = rsum_cache;
1097                 } else {
1098                         kmem_free(rsum_cache);
1099                 }
1100         }
1101 
1102         return error;
1103 }
1104 
1105 /*
1106  * Allocate an extent in the realtime subvolume, with the usual allocation
1107  * parameters.  The length units are all in realtime extents, as is the
1108  * result block number.
1109  */
1110 int                                     /* error */
1111 xfs_rtallocate_extent(
1112         xfs_trans_t     *tp,            /* transaction pointer */
1113         xfs_rtblock_t   bno,            /* starting block number to allocate */
1114         xfs_extlen_t    minlen,         /* minimum length to allocate */
1115         xfs_extlen_t    maxlen,         /* maximum length to allocate */
1116         xfs_extlen_t    *len,           /* out: actual length allocated */
1117         int             wasdel,         /* was a delayed allocation extent */
1118         xfs_extlen_t    prod,           /* extent product factor */
1119         xfs_rtblock_t   *rtblock)       /* out: start block allocated */
1120 {
1121         xfs_mount_t     *mp = tp->t_mountp;
1122         int             error;          /* error value */
1123         xfs_rtblock_t   r;              /* result allocated block */
1124         xfs_fsblock_t   sb;             /* summary file block number */
1125         xfs_buf_t       *sumbp;         /* summary file block buffer */
1126 
1127         ASSERT(xfs_isilocked(mp->m_rbmip, XFS_ILOCK_EXCL));
1128         ASSERT(minlen > 0 && minlen <= maxlen);
1129 
1130         /*
1131          * If prod is set then figure out what to do to minlen and maxlen.
1132          */
1133         if (prod > 1) {
1134                 xfs_extlen_t    i;
1135 
1136                 if ((i = maxlen % prod))
1137                         maxlen -= i;
1138                 if ((i = minlen % prod))
1139                         minlen += prod - i;
1140                 if (maxlen < minlen) {
1141                         *rtblock = NULLRTBLOCK;
1142                         return 0;
1143                 }
1144         }
1145 
1146 retry:
1147         sumbp = NULL;
1148         if (bno == 0) {
1149                 error = xfs_rtallocate_extent_size(mp, tp, minlen, maxlen, len,
1150                                 &sumbp, &sb, prod, &r);
1151         } else {
1152                 error = xfs_rtallocate_extent_near(mp, tp, bno, minlen, maxlen,
1153                                 len, &sumbp, &sb, prod, &r);
1154         }
1155 
1156         if (error)
1157                 return error;
1158 
1159         /*
1160          * If it worked, update the superblock.
1161          */
1162         if (r != NULLRTBLOCK) {
1163                 long    slen = (long)*len;
1164 
1165                 ASSERT(*len >= minlen && *len <= maxlen);
1166                 if (wasdel)
1167                         xfs_trans_mod_sb(tp, XFS_TRANS_SB_RES_FREXTENTS, -slen);
1168                 else
1169                         xfs_trans_mod_sb(tp, XFS_TRANS_SB_FREXTENTS, -slen);
1170         } else if (prod > 1) {
1171                 prod = 1;
1172                 goto retry;
1173         }
1174 
1175         *rtblock = r;
1176         return 0;
1177 }
1178 
1179 /*
1180  * Initialize realtime fields in the mount structure.
1181  */
1182 int                             /* error */
1183 xfs_rtmount_init(
1184         struct xfs_mount        *mp)    /* file system mount structure */
1185 {
1186         struct xfs_buf          *bp;    /* buffer for last block of subvolume */
1187         struct xfs_sb           *sbp;   /* filesystem superblock copy in mount */
1188         xfs_daddr_t             d;      /* address of last block of subvolume */
1189         int                     error;
1190 
1191         sbp = &mp->m_sb;
1192         if (sbp->sb_rblocks == 0)
1193                 return 0;
1194         if (mp->m_rtdev_targp == NULL) {
1195                 xfs_warn(mp,
1196         "Filesystem has a realtime volume, use rtdev=device option");
1197                 return -ENODEV;
1198         }
1199         mp->m_rsumlevels = sbp->sb_rextslog + 1;
1200         mp->m_rsumsize =
1201                 (uint)sizeof(xfs_suminfo_t) * mp->m_rsumlevels *
1202                 sbp->sb_rbmblocks;
1203         mp->m_rsumsize = roundup(mp->m_rsumsize, sbp->sb_blocksize);
1204         mp->m_rbmip = mp->m_rsumip = NULL;
1205         /*
1206          * Check that the realtime section is an ok size.
1207          */
1208         d = (xfs_daddr_t)XFS_FSB_TO_BB(mp, mp->m_sb.sb_rblocks);
1209         if (XFS_BB_TO_FSB(mp, d) != mp->m_sb.sb_rblocks) {
1210                 xfs_warn(mp, "realtime mount -- %llu != %llu",
1211                         (unsigned long long) XFS_BB_TO_FSB(mp, d),
1212                         (unsigned long long) mp->m_sb.sb_rblocks);
1213                 return -EFBIG;
1214         }
1215         error = xfs_buf_read_uncached(mp->m_rtdev_targp,
1216                                         d - XFS_FSB_TO_BB(mp, 1),
1217                                         XFS_FSB_TO_BB(mp, 1), 0, &bp, NULL);
1218         if (error) {
1219                 xfs_warn(mp, "realtime device size check failed");
1220                 return error;
1221         }
1222         xfs_buf_relse(bp);
1223         return 0;
1224 }
1225 
1226 /*
1227  * Get the bitmap and summary inodes and the summary cache into the mount
1228  * structure at mount time.
1229  */
1230 int                                     /* error */
1231 xfs_rtmount_inodes(
1232         xfs_mount_t     *mp)            /* file system mount structure */
1233 {
1234         int             error;          /* error return value */
1235         xfs_sb_t        *sbp;
1236 
1237         sbp = &mp->m_sb;
1238         error = xfs_iget(mp, NULL, sbp->sb_rbmino, 0, 0, &mp->m_rbmip);
1239         if (error)
1240                 return error;
1241         ASSERT(mp->m_rbmip != NULL);
1242 
1243         error = xfs_iget(mp, NULL, sbp->sb_rsumino, 0, 0, &mp->m_rsumip);
1244         if (error) {
1245                 xfs_irele(mp->m_rbmip);
1246                 return error;
1247         }
1248         ASSERT(mp->m_rsumip != NULL);
1249         xfs_alloc_rsum_cache(mp, sbp->sb_rbmblocks);
1250         return 0;
1251 }
1252 
1253 void
1254 xfs_rtunmount_inodes(
1255         struct xfs_mount        *mp)
1256 {
1257         kmem_free(mp->m_rsum_cache);
1258         if (mp->m_rbmip)
1259                 xfs_irele(mp->m_rbmip);
1260         if (mp->m_rsumip)
1261                 xfs_irele(mp->m_rsumip);
1262 }
1263 
1264 /*
1265  * Pick an extent for allocation at the start of a new realtime file.
1266  * Use the sequence number stored in the atime field of the bitmap inode.
1267  * Translate this to a fraction of the rtextents, and return the product
1268  * of rtextents and the fraction.
1269  * The fraction sequence is 0, 1/2, 1/4, 3/4, 1/8, ..., 7/8, 1/16, ...
1270  */
1271 int                                     /* error */
1272 xfs_rtpick_extent(
1273         xfs_mount_t     *mp,            /* file system mount point */
1274         xfs_trans_t     *tp,            /* transaction pointer */
1275         xfs_extlen_t    len,            /* allocation length (rtextents) */
1276         xfs_rtblock_t   *pick)          /* result rt extent */
1277 {
1278         xfs_rtblock_t   b;              /* result block */
1279         int             log2;           /* log of sequence number */
1280         uint64_t        resid;          /* residual after log removed */
1281         uint64_t        seq;            /* sequence number of file creation */
1282         uint64_t        *seqp;          /* pointer to seqno in inode */
1283 
1284         ASSERT(xfs_isilocked(mp->m_rbmip, XFS_ILOCK_EXCL));
1285 
1286         seqp = (uint64_t *)&VFS_I(mp->m_rbmip)->i_atime;
1287         if (!(mp->m_rbmip->i_d.di_flags & XFS_DIFLAG_NEWRTBM)) {
1288                 mp->m_rbmip->i_d.di_flags |= XFS_DIFLAG_NEWRTBM;
1289                 *seqp = 0;
1290         }
1291         seq = *seqp;
1292         if ((log2 = xfs_highbit64(seq)) == -1)
1293                 b = 0;
1294         else {
1295                 resid = seq - (1ULL << log2);
1296                 b = (mp->m_sb.sb_rextents * ((resid << 1) + 1ULL)) >>
1297                     (log2 + 1);
1298                 if (b >= mp->m_sb.sb_rextents)
1299                         div64_u64_rem(b, mp->m_sb.sb_rextents, &b);
1300                 if (b + len > mp->m_sb.sb_rextents)
1301                         b = mp->m_sb.sb_rextents - len;
1302         }
1303         *seqp = seq + 1;
1304         xfs_trans_log_inode(tp, mp->m_rbmip, XFS_ILOG_CORE);
1305         *pick = b;
1306         return 0;
1307 }
1308 

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