The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_unit.c

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    1 /*-
    2  * Copyright (c) 2004 Poul-Henning Kamp
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  *
   26  * $FreeBSD: releng/9.2/sys/kern/subr_unit.c 240579 2012-09-17 00:44:16Z eadler $
   27  *
   28  *
   29  * Unit number allocation functions.
   30  *
   31  * These functions implement a mixed run-length/bitmap management of unit
   32  * number spaces in a very memory efficient manner.
   33  *
   34  * Allocation policy is always lowest free number first.
   35  *
   36  * A return value of -1 signals that no more unit numbers are available.
   37  *
   38  * There is no cost associated with the range of unitnumbers, so unless
   39  * the resource really is finite, specify INT_MAX to new_unrhdr() and
   40  * forget about checking the return value.
   41  *
   42  * If a mutex is not provided when the unit number space is created, a
   43  * default global mutex is used.  The advantage to passing a mutex in, is
   44  * that the alloc_unrl() function can be called with the mutex already
   45  * held (it will not be released by alloc_unrl()).
   46  *
   47  * The allocation function alloc_unr{l}() never sleeps (but it may block on
   48  * the mutex of course).
   49  *
   50  * Freeing a unit number may require allocating memory, and can therefore
   51  * sleep so the free_unr() function does not come in a pre-locked variant.
   52  *
   53  * A userland test program is included.
   54  *
   55  * Memory usage is a very complex function of the exact allocation
   56  * pattern, but always very compact:
   57  *    * For the very typical case where a single unbroken run of unit
   58  *      numbers are allocated 44 bytes are used on i386.
   59  *    * For a unit number space of 1000 units and the random pattern
   60  *      in the usermode test program included, the worst case usage
   61  *      was 252 bytes on i386 for 500 allocated and 500 free units.
   62  *    * For a unit number space of 10000 units and the random pattern
   63  *      in the usermode test program included, the worst case usage
   64  *      was 798 bytes on i386 for 5000 allocated and 5000 free units.
   65  *    * The worst case is where every other unit number is allocated and
   66  *      the rest are free.  In that case 44 + N/4 bytes are used where
   67  *      N is the number of the highest unit allocated.
   68  */
   69 
   70 #include <sys/types.h>
   71 #include <sys/queue.h>
   72 #include <sys/bitstring.h>
   73 
   74 #ifdef _KERNEL
   75 
   76 #include <sys/param.h>
   77 #include <sys/malloc.h>
   78 #include <sys/kernel.h>
   79 #include <sys/systm.h>
   80 #include <sys/limits.h>
   81 #include <sys/lock.h>
   82 #include <sys/mutex.h>
   83 
   84 /*
   85  * In theory it would be smarter to allocate the individual blocks
   86  * with the zone allocator, but at this time the expectation is that
   87  * there will typically not even be enough allocations to fill a single
   88  * page, so we stick with malloc for now.
   89  */
   90 static MALLOC_DEFINE(M_UNIT, "Unitno", "Unit number allocation");
   91 
   92 #define Malloc(foo) malloc(foo, M_UNIT, M_WAITOK | M_ZERO)
   93 #define Free(foo) free(foo, M_UNIT)
   94 
   95 static struct mtx unitmtx;
   96 
   97 MTX_SYSINIT(unit, &unitmtx, "unit# allocation", MTX_DEF);
   98 
   99 #else /* ...USERLAND */
  100 
  101 #include <stdio.h>
  102 #include <stdlib.h>
  103 #include <string.h>
  104 
  105 #define KASSERT(cond, arg) \
  106         do { \
  107                 if (!(cond)) { \
  108                         printf arg; \
  109                         abort(); \
  110                 } \
  111         } while (0)
  112 
  113 static int no_alloc;
  114 #define Malloc(foo) _Malloc(foo, __LINE__)
  115 static void *
  116 _Malloc(size_t foo, int line)
  117 {
  118 
  119         KASSERT(no_alloc == 0, ("malloc in wrong place() line %d", line));
  120         return (calloc(foo, 1));
  121 }
  122 #define Free(foo) free(foo)
  123 
  124 struct unrhdr;
  125 
  126 
  127 struct mtx {
  128         int     state;
  129 } unitmtx;
  130 
  131 static void
  132 mtx_lock(struct mtx *mp)
  133 {
  134         KASSERT(mp->state == 0, ("mutex already locked"));
  135         mp->state = 1;
  136 }
  137 
  138 static void
  139 mtx_unlock(struct mtx *mp)
  140 {
  141         KASSERT(mp->state == 1, ("mutex not locked"));
  142         mp->state = 0;
  143 }
  144 
  145 #define MA_OWNED        9
  146 
  147 static void
  148 mtx_assert(struct mtx *mp, int flag)
  149 {
  150         if (flag == MA_OWNED) {
  151                 KASSERT(mp->state == 1, ("mtx_assert(MA_OWNED) not true"));
  152         }
  153 }
  154 
  155 #define CTASSERT(foo)
  156 #define WITNESS_WARN(flags, lock, fmt, ...)     (void)0
  157 
  158 #endif /* USERLAND */
  159 
  160 /*
  161  * This is our basic building block.
  162  *
  163  * It can be used in three different ways depending on the value of the ptr
  164  * element:
  165  *     If ptr is NULL, it represents a run of free items.
  166  *     If ptr points to the unrhdr it represents a run of allocated items.
  167  *     Otherwise it points to an bitstring of allocated items.
  168  *
  169  * For runs the len field is the length of the run.
  170  * For bitmaps the len field represents the number of allocated items.
  171  *
  172  * The bitmap is the same size as struct unr to optimize memory management.
  173  */
  174 struct unr {
  175         TAILQ_ENTRY(unr)        list;
  176         u_int                   len;
  177         void                    *ptr;
  178 };
  179 
  180 struct unrb {
  181         u_char                  busy;
  182         bitstr_t                map[sizeof(struct unr) - 1];
  183 };
  184 
  185 CTASSERT(sizeof(struct unr) == sizeof(struct unrb));
  186 
  187 /* Number of bits in the bitmap */
  188 #define NBITS   ((int)sizeof(((struct unrb *)NULL)->map) * 8)
  189 
  190 /* Header element for a unr number space. */
  191 
  192 struct unrhdr {
  193         TAILQ_HEAD(unrhd,unr)   head;
  194         u_int                   low;    /* Lowest item */
  195         u_int                   high;   /* Highest item */
  196         u_int                   busy;   /* Count of allocated items */
  197         u_int                   alloc;  /* Count of memory allocations */
  198         u_int                   first;  /* items in allocated from start */
  199         u_int                   last;   /* items free at end */
  200         struct mtx              *mtx;
  201         TAILQ_HEAD(unrfr,unr)   ppfree; /* Items to be freed after mtx
  202                                            lock dropped */
  203 };
  204 
  205 
  206 #if defined(DIAGNOSTIC) || !defined(_KERNEL)
  207 /*
  208  * Consistency check function.
  209  *
  210  * Checks the internal consistency as well as we can.
  211  * 
  212  * Called at all boundaries of this API.
  213  */
  214 static void
  215 check_unrhdr(struct unrhdr *uh, int line)
  216 {
  217         struct unr *up;
  218         struct unrb *ub;
  219         u_int x, y, z, w;
  220 
  221         y = uh->first;
  222         z = 0;
  223         TAILQ_FOREACH(up, &uh->head, list) {
  224                 z++;
  225                 if (up->ptr != uh && up->ptr != NULL) {
  226                         ub = up->ptr;
  227                         KASSERT (up->len <= NBITS,
  228                             ("UNR inconsistency: len %u max %d (line %d)\n",
  229                             up->len, NBITS, line));
  230                         z++;
  231                         w = 0;
  232                         for (x = 0; x < up->len; x++)
  233                                 if (bit_test(ub->map, x))
  234                                         w++;
  235                         KASSERT (w == ub->busy,
  236                             ("UNR inconsistency: busy %u found %u (line %d)\n",
  237                             ub->busy, w, line));
  238                         y += w;
  239                 } else if (up->ptr != NULL) 
  240                         y += up->len;
  241         }
  242         KASSERT (y == uh->busy,
  243             ("UNR inconsistency: items %u found %u (line %d)\n",
  244             uh->busy, y, line));
  245         KASSERT (z == uh->alloc,
  246             ("UNR inconsistency: chunks %u found %u (line %d)\n",
  247             uh->alloc, z, line));
  248 }
  249 
  250 #else
  251 
  252 static __inline void
  253 check_unrhdr(struct unrhdr *uh, int line)
  254 {
  255 
  256 }
  257 
  258 #endif
  259 
  260 
  261 /*
  262  * Userland memory management.  Just use calloc and keep track of how
  263  * many elements we have allocated for check_unrhdr().
  264  */
  265 
  266 static __inline void *
  267 new_unr(struct unrhdr *uh, void **p1, void **p2)
  268 {
  269         void *p;
  270 
  271         uh->alloc++;
  272         KASSERT(*p1 != NULL || *p2 != NULL, ("Out of cached memory"));
  273         if (*p1 != NULL) {
  274                 p = *p1;
  275                 *p1 = NULL;
  276                 return (p);
  277         } else {
  278                 p = *p2;
  279                 *p2 = NULL;
  280                 return (p);
  281         }
  282 }
  283 
  284 static __inline void
  285 delete_unr(struct unrhdr *uh, void *ptr)
  286 {
  287         struct unr *up;
  288 
  289         uh->alloc--;
  290         up = ptr;
  291         TAILQ_INSERT_TAIL(&uh->ppfree, up, list);
  292 }
  293 
  294 void
  295 clean_unrhdrl(struct unrhdr *uh)
  296 {
  297         struct unr *up;
  298 
  299         mtx_assert(uh->mtx, MA_OWNED);
  300         while ((up = TAILQ_FIRST(&uh->ppfree)) != NULL) {
  301                 TAILQ_REMOVE(&uh->ppfree, up, list);
  302                 mtx_unlock(uh->mtx);
  303                 Free(up);
  304                 mtx_lock(uh->mtx);
  305         }
  306 
  307 }
  308 
  309 void
  310 clean_unrhdr(struct unrhdr *uh)
  311 {
  312 
  313         mtx_lock(uh->mtx);
  314         clean_unrhdrl(uh);
  315         mtx_unlock(uh->mtx);
  316 }
  317 
  318 /*
  319  * Allocate a new unrheader set.
  320  *
  321  * Highest and lowest valid values given as parameters.
  322  */
  323 
  324 struct unrhdr *
  325 new_unrhdr(int low, int high, struct mtx *mutex)
  326 {
  327         struct unrhdr *uh;
  328 
  329         KASSERT(low >= 0 && low <= high,
  330             ("UNR: use error: new_unrhdr(%d, %d)", low, high));
  331         uh = Malloc(sizeof *uh);
  332         if (mutex != NULL)
  333                 uh->mtx = mutex;
  334         else
  335                 uh->mtx = &unitmtx;
  336         TAILQ_INIT(&uh->head);
  337         TAILQ_INIT(&uh->ppfree);
  338         uh->low = low;
  339         uh->high = high;
  340         uh->first = 0;
  341         uh->last = 1 + (high - low);
  342         check_unrhdr(uh, __LINE__);
  343         return (uh);
  344 }
  345 
  346 void
  347 delete_unrhdr(struct unrhdr *uh)
  348 {
  349 
  350         check_unrhdr(uh, __LINE__);
  351         KASSERT(uh->busy == 0, ("unrhdr has %u allocations", uh->busy));
  352         KASSERT(uh->alloc == 0, ("UNR memory leak in delete_unrhdr"));
  353         KASSERT(TAILQ_FIRST(&uh->ppfree) == NULL,
  354             ("unrhdr has postponed item for free"));
  355         Free(uh);
  356 }
  357 
  358 static __inline int
  359 is_bitmap(struct unrhdr *uh, struct unr *up)
  360 {
  361         return (up->ptr != uh && up->ptr != NULL);
  362 }
  363 
  364 /*
  365  * Look for sequence of items which can be combined into a bitmap, if
  366  * multiple are present, take the one which saves most memory.
  367  * 
  368  * Return (1) if a sequence was found to indicate that another call
  369  * might be able to do more.  Return (0) if we found no suitable sequence.
  370  *
  371  * NB: called from alloc_unr(), no new memory allocation allowed.
  372  */
  373 static int
  374 optimize_unr(struct unrhdr *uh)
  375 {
  376         struct unr *up, *uf, *us;
  377         struct unrb *ub, *ubf;
  378         u_int a, l, ba;
  379 
  380         /*
  381          * Look for the run of items (if any) which when collapsed into
  382          * a bitmap would save most memory.
  383          */
  384         us = NULL;
  385         ba = 0;
  386         TAILQ_FOREACH(uf, &uh->head, list) {
  387                 if (uf->len >= NBITS)
  388                         continue;
  389                 a = 1;
  390                 if (is_bitmap(uh, uf))
  391                         a++;
  392                 l = uf->len;
  393                 up = uf;
  394                 while (1) {
  395                         up = TAILQ_NEXT(up, list);
  396                         if (up == NULL)
  397                                 break;
  398                         if ((up->len + l) > NBITS)
  399                                 break;
  400                         a++;
  401                         if (is_bitmap(uh, up))
  402                                 a++;
  403                         l += up->len;
  404                 }
  405                 if (a > ba) {
  406                         ba = a;
  407                         us = uf;
  408                 }
  409         }
  410         if (ba < 3)
  411                 return (0);
  412 
  413         /*
  414          * If the first element is not a bitmap, make it one.
  415          * Trying to do so without allocating more memory complicates things
  416          * a bit
  417          */
  418         if (!is_bitmap(uh, us)) {
  419                 uf = TAILQ_NEXT(us, list);
  420                 TAILQ_REMOVE(&uh->head, us, list);
  421                 a = us->len;
  422                 l = us->ptr == uh ? 1 : 0;
  423                 ub = (void *)us;
  424                 ub->busy = 0;
  425                 if (l) {
  426                         bit_nset(ub->map, 0, a);
  427                         ub->busy += a;
  428                 } else {
  429                         bit_nclear(ub->map, 0, a);
  430                 }
  431                 if (!is_bitmap(uh, uf)) {
  432                         if (uf->ptr == NULL) {
  433                                 bit_nclear(ub->map, a, a + uf->len - 1);
  434                         } else {
  435                                 bit_nset(ub->map, a, a + uf->len - 1);
  436                                 ub->busy += uf->len;
  437                         }
  438                         uf->ptr = ub;
  439                         uf->len += a;
  440                         us = uf;
  441                 } else {
  442                         ubf = uf->ptr;
  443                         for (l = 0; l < uf->len; l++, a++) {
  444                                 if (bit_test(ubf->map, l)) {
  445                                         bit_set(ub->map, a);
  446                                         ub->busy++;
  447                                 } else {
  448                                         bit_clear(ub->map, a);
  449                                 }
  450                         }
  451                         uf->len = a;
  452                         delete_unr(uh, uf->ptr);
  453                         uf->ptr = ub;
  454                         us = uf;
  455                 }
  456         }
  457         ub = us->ptr;
  458         while (1) {
  459                 uf = TAILQ_NEXT(us, list);
  460                 if (uf == NULL)
  461                         return (1);
  462                 if (uf->len + us->len > NBITS)
  463                         return (1);
  464                 if (uf->ptr == NULL) {
  465                         bit_nclear(ub->map, us->len, us->len + uf->len - 1);
  466                         us->len += uf->len;
  467                         TAILQ_REMOVE(&uh->head, uf, list);
  468                         delete_unr(uh, uf);
  469                 } else if (uf->ptr == uh) {
  470                         bit_nset(ub->map, us->len, us->len + uf->len - 1);
  471                         ub->busy += uf->len;
  472                         us->len += uf->len;
  473                         TAILQ_REMOVE(&uh->head, uf, list);
  474                         delete_unr(uh, uf);
  475                 } else {
  476                         ubf = uf->ptr;
  477                         for (l = 0; l < uf->len; l++, us->len++) {
  478                                 if (bit_test(ubf->map, l)) {
  479                                         bit_set(ub->map, us->len);
  480                                         ub->busy++;
  481                                 } else {
  482                                         bit_clear(ub->map, us->len);
  483                                 }
  484                         }
  485                         TAILQ_REMOVE(&uh->head, uf, list);
  486                         delete_unr(uh, ubf);
  487                         delete_unr(uh, uf);
  488                 }
  489         }
  490 }
  491 
  492 /*
  493  * See if a given unr should be collapsed with a neighbor.
  494  *
  495  * NB: called from alloc_unr(), no new memory allocation allowed.
  496  */
  497 static void
  498 collapse_unr(struct unrhdr *uh, struct unr *up)
  499 {
  500         struct unr *upp;
  501         struct unrb *ub;
  502 
  503         /* If bitmap is all set or clear, change it to runlength */
  504         if (is_bitmap(uh, up)) {
  505                 ub = up->ptr;
  506                 if (ub->busy == up->len) {
  507                         delete_unr(uh, up->ptr);
  508                         up->ptr = uh;
  509                 } else if (ub->busy == 0) {
  510                         delete_unr(uh, up->ptr);
  511                         up->ptr = NULL;
  512                 }
  513         }
  514 
  515         /* If nothing left in runlength, delete it */
  516         if (up->len == 0) {
  517                 upp = TAILQ_PREV(up, unrhd, list);
  518                 if (upp == NULL)
  519                         upp = TAILQ_NEXT(up, list);
  520                 TAILQ_REMOVE(&uh->head, up, list);
  521                 delete_unr(uh, up);
  522                 up = upp;
  523         }
  524 
  525         /* If we have "hot-spot" still, merge with neighbor if possible */
  526         if (up != NULL) {
  527                 upp = TAILQ_PREV(up, unrhd, list);
  528                 if (upp != NULL && up->ptr == upp->ptr) {
  529                         up->len += upp->len;
  530                         TAILQ_REMOVE(&uh->head, upp, list);
  531                         delete_unr(uh, upp);
  532                         }
  533                 upp = TAILQ_NEXT(up, list);
  534                 if (upp != NULL && up->ptr == upp->ptr) {
  535                         up->len += upp->len;
  536                         TAILQ_REMOVE(&uh->head, upp, list);
  537                         delete_unr(uh, upp);
  538                 }
  539         }
  540 
  541         /* Merge into ->first if possible */
  542         upp = TAILQ_FIRST(&uh->head);
  543         if (upp != NULL && upp->ptr == uh) {
  544                 uh->first += upp->len;
  545                 TAILQ_REMOVE(&uh->head, upp, list);
  546                 delete_unr(uh, upp);
  547                 if (up == upp)
  548                         up = NULL;
  549         }
  550 
  551         /* Merge into ->last if possible */
  552         upp = TAILQ_LAST(&uh->head, unrhd);
  553         if (upp != NULL && upp->ptr == NULL) {
  554                 uh->last += upp->len;
  555                 TAILQ_REMOVE(&uh->head, upp, list);
  556                 delete_unr(uh, upp);
  557                 if (up == upp)
  558                         up = NULL;
  559         }
  560 
  561         /* Try to make bitmaps */
  562         while (optimize_unr(uh))
  563                 continue;
  564 }
  565 
  566 /*
  567  * Allocate a free unr.
  568  */
  569 int
  570 alloc_unrl(struct unrhdr *uh)
  571 {
  572         struct unr *up;
  573         struct unrb *ub;
  574         u_int x;
  575         int y;
  576 
  577         mtx_assert(uh->mtx, MA_OWNED);
  578         check_unrhdr(uh, __LINE__);
  579         x = uh->low + uh->first;
  580 
  581         up = TAILQ_FIRST(&uh->head);
  582 
  583         /*
  584          * If we have an ideal split, just adjust the first+last
  585          */
  586         if (up == NULL && uh->last > 0) {
  587                 uh->first++;
  588                 uh->last--;
  589                 uh->busy++;
  590                 return (x);
  591         }
  592 
  593         /*
  594          * We can always allocate from the first list element, so if we have 
  595          * nothing on the list, we must have run out of unit numbers.
  596          */
  597         if (up == NULL)
  598                 return (-1);
  599 
  600         KASSERT(up->ptr != uh, ("UNR first element is allocated"));
  601 
  602         if (up->ptr == NULL) {  /* free run */
  603                 uh->first++;
  604                 up->len--;
  605         } else {                /* bitmap */
  606                 ub = up->ptr;
  607                 KASSERT(ub->busy < up->len, ("UNR bitmap confusion"));
  608                 bit_ffc(ub->map, up->len, &y);
  609                 KASSERT(y != -1, ("UNR corruption: No clear bit in bitmap."));
  610                 bit_set(ub->map, y);
  611                 ub->busy++;
  612                 x += y;
  613         }
  614         uh->busy++;
  615         collapse_unr(uh, up);
  616         return (x);
  617 }
  618 
  619 int
  620 alloc_unr(struct unrhdr *uh)
  621 {
  622         int i;
  623 
  624         mtx_lock(uh->mtx);
  625         i = alloc_unrl(uh);
  626         clean_unrhdrl(uh);
  627         mtx_unlock(uh->mtx);
  628         return (i);
  629 }
  630 
  631 static int
  632 alloc_unr_specificl(struct unrhdr *uh, u_int item, void **p1, void **p2)
  633 {
  634         struct unr *up, *upn;
  635         struct unrb *ub;
  636         u_int i, last, tl;
  637 
  638         mtx_assert(uh->mtx, MA_OWNED);
  639 
  640         if (item < uh->low + uh->first || item > uh->high)
  641                 return (-1);
  642 
  643         up = TAILQ_FIRST(&uh->head);
  644         /* Ideal split. */
  645         if (up == NULL && item - uh->low == uh->first) {
  646                 uh->first++;
  647                 uh->last--;
  648                 uh->busy++;
  649                 check_unrhdr(uh, __LINE__);
  650                 return (item);
  651         }
  652 
  653         i = item - uh->low - uh->first;
  654 
  655         if (up == NULL) {
  656                 up = new_unr(uh, p1, p2);
  657                 up->ptr = NULL;
  658                 up->len = i;
  659                 TAILQ_INSERT_TAIL(&uh->head, up, list);
  660                 up = new_unr(uh, p1, p2);
  661                 up->ptr = uh;
  662                 up->len = 1;
  663                 TAILQ_INSERT_TAIL(&uh->head, up, list);
  664                 uh->last = uh->high - uh->low - i;
  665                 uh->busy++;
  666                 check_unrhdr(uh, __LINE__);
  667                 return (item);
  668         } else {
  669                 /* Find the item which contains the unit we want to allocate. */
  670                 TAILQ_FOREACH(up, &uh->head, list) {
  671                         if (up->len > i)
  672                                 break;
  673                         i -= up->len;
  674                 }
  675         }
  676 
  677         if (up == NULL) {
  678                 if (i > 0) {
  679                         up = new_unr(uh, p1, p2);
  680                         up->ptr = NULL;
  681                         up->len = i;
  682                         TAILQ_INSERT_TAIL(&uh->head, up, list);
  683                 }
  684                 up = new_unr(uh, p1, p2);
  685                 up->ptr = uh;
  686                 up->len = 1;
  687                 TAILQ_INSERT_TAIL(&uh->head, up, list);
  688                 goto done;
  689         }
  690 
  691         if (is_bitmap(uh, up)) {
  692                 ub = up->ptr;
  693                 if (bit_test(ub->map, i) == 0) {
  694                         bit_set(ub->map, i);
  695                         ub->busy++;
  696                         goto done;
  697                 } else
  698                         return (-1);
  699         } else if (up->ptr == uh)
  700                 return (-1);
  701 
  702         KASSERT(up->ptr == NULL,
  703             ("alloc_unr_specificl: up->ptr != NULL (up=%p)", up));
  704 
  705         /* Split off the tail end, if any. */
  706         tl = up->len - (1 + i);
  707         if (tl > 0) {
  708                 upn = new_unr(uh, p1, p2);
  709                 upn->ptr = NULL;
  710                 upn->len = tl;
  711                 TAILQ_INSERT_AFTER(&uh->head, up, upn, list);
  712         }
  713 
  714         /* Split off head end, if any */
  715         if (i > 0) {
  716                 upn = new_unr(uh, p1, p2);
  717                 upn->len = i;
  718                 upn->ptr = NULL;
  719                 TAILQ_INSERT_BEFORE(up, upn, list);
  720         }
  721         up->len = 1;
  722         up->ptr = uh;
  723 
  724 done:
  725         last = uh->high - uh->low - (item - uh->low);
  726         if (uh->last > last)
  727                 uh->last = last;
  728         uh->busy++;
  729         collapse_unr(uh, up);
  730         check_unrhdr(uh, __LINE__);
  731         return (item);
  732 }
  733 
  734 int
  735 alloc_unr_specific(struct unrhdr *uh, u_int item)
  736 {
  737         void *p1, *p2;
  738         int i;
  739 
  740         WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "alloc_unr_specific");
  741 
  742         p1 = Malloc(sizeof(struct unr));
  743         p2 = Malloc(sizeof(struct unr));
  744 
  745         mtx_lock(uh->mtx);
  746         i = alloc_unr_specificl(uh, item, &p1, &p2);
  747         mtx_unlock(uh->mtx);
  748 
  749         if (p1 != NULL)
  750                 Free(p1);
  751         if (p2 != NULL)
  752                 Free(p2);
  753 
  754         return (i);
  755 }
  756 
  757 /*
  758  * Free a unr.
  759  *
  760  * If we can save unrs by using a bitmap, do so.
  761  */
  762 static void
  763 free_unrl(struct unrhdr *uh, u_int item, void **p1, void **p2)
  764 {
  765         struct unr *up, *upp, *upn;
  766         struct unrb *ub;
  767         u_int pl;
  768 
  769         KASSERT(item >= uh->low && item <= uh->high,
  770             ("UNR: free_unr(%u) out of range [%u...%u]",
  771              item, uh->low, uh->high));
  772         check_unrhdr(uh, __LINE__);
  773         item -= uh->low;
  774         upp = TAILQ_FIRST(&uh->head);
  775         /*
  776          * Freeing in the ideal split case
  777          */
  778         if (item + 1 == uh->first && upp == NULL) {
  779                 uh->last++;
  780                 uh->first--;
  781                 uh->busy--;
  782                 check_unrhdr(uh, __LINE__);
  783                 return;
  784         }
  785         /*
  786          * Freeing in the ->first section.  Create a run starting at the
  787          * freed item.  The code below will subdivide it.
  788          */
  789         if (item < uh->first) {
  790                 up = new_unr(uh, p1, p2);
  791                 up->ptr = uh;
  792                 up->len = uh->first - item;
  793                 TAILQ_INSERT_HEAD(&uh->head, up, list);
  794                 uh->first -= up->len;
  795         }
  796 
  797         item -= uh->first;
  798 
  799         /* Find the item which contains the unit we want to free */
  800         TAILQ_FOREACH(up, &uh->head, list) {
  801                 if (up->len > item)
  802                         break;
  803                 item -= up->len;
  804         }
  805 
  806         /* Handle bitmap items */
  807         if (is_bitmap(uh, up)) {
  808                 ub = up->ptr;
  809                 
  810                 KASSERT(bit_test(ub->map, item) != 0,
  811                     ("UNR: Freeing free item %d (bitmap)\n", item));
  812                 bit_clear(ub->map, item);
  813                 uh->busy--;
  814                 ub->busy--;
  815                 collapse_unr(uh, up);
  816                 return;
  817         }
  818 
  819         KASSERT(up->ptr == uh, ("UNR Freeing free item %d (run))\n", item));
  820 
  821         /* Just this one left, reap it */
  822         if (up->len == 1) {
  823                 up->ptr = NULL;
  824                 uh->busy--;
  825                 collapse_unr(uh, up);
  826                 return;
  827         }
  828 
  829         /* Check if we can shift the item into the previous 'free' run */
  830         upp = TAILQ_PREV(up, unrhd, list);
  831         if (item == 0 && upp != NULL && upp->ptr == NULL) {
  832                 upp->len++;
  833                 up->len--;
  834                 uh->busy--;
  835                 collapse_unr(uh, up);
  836                 return;
  837         }
  838 
  839         /* Check if we can shift the item to the next 'free' run */
  840         upn = TAILQ_NEXT(up, list);
  841         if (item == up->len - 1 && upn != NULL && upn->ptr == NULL) {
  842                 upn->len++;
  843                 up->len--;
  844                 uh->busy--;
  845                 collapse_unr(uh, up);
  846                 return;
  847         }
  848 
  849         /* Split off the tail end, if any. */
  850         pl = up->len - (1 + item);
  851         if (pl > 0) {
  852                 upp = new_unr(uh, p1, p2);
  853                 upp->ptr = uh;
  854                 upp->len = pl;
  855                 TAILQ_INSERT_AFTER(&uh->head, up, upp, list);
  856         }
  857 
  858         /* Split off head end, if any */
  859         if (item > 0) {
  860                 upp = new_unr(uh, p1, p2);
  861                 upp->len = item;
  862                 upp->ptr = uh;
  863                 TAILQ_INSERT_BEFORE(up, upp, list);
  864         }
  865         up->len = 1;
  866         up->ptr = NULL;
  867         uh->busy--;
  868         collapse_unr(uh, up);
  869 }
  870 
  871 void
  872 free_unr(struct unrhdr *uh, u_int item)
  873 {
  874         void *p1, *p2;
  875 
  876         WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "free_unr");
  877         p1 = Malloc(sizeof(struct unr));
  878         p2 = Malloc(sizeof(struct unr));
  879         mtx_lock(uh->mtx);
  880         free_unrl(uh, item, &p1, &p2);
  881         clean_unrhdrl(uh);
  882         mtx_unlock(uh->mtx);
  883         if (p1 != NULL)
  884                 Free(p1);
  885         if (p2 != NULL)
  886                 Free(p2);
  887 }
  888 
  889 #ifndef _KERNEL /* USERLAND test driver */
  890 
  891 /*
  892  * Simple stochastic test driver for the above functions
  893  */
  894 
  895 static void
  896 print_unr(struct unrhdr *uh, struct unr *up)
  897 {
  898         u_int x;
  899         struct unrb *ub;
  900 
  901         printf("  %p len = %5u ", up, up->len);
  902         if (up->ptr == NULL)
  903                 printf("free\n");
  904         else if (up->ptr == uh)
  905                 printf("alloc\n");
  906         else {
  907                 ub = up->ptr;
  908                 printf("bitmap(%d) [", ub->busy);
  909                 for (x = 0; x < up->len; x++) {
  910                         if (bit_test(ub->map, x))
  911                                 printf("#");
  912                         else 
  913                                 printf(" ");
  914                 }
  915                 printf("]\n");
  916         }
  917 }
  918 
  919 static void
  920 print_unrhdr(struct unrhdr *uh)
  921 {
  922         struct unr *up;
  923         u_int x;
  924 
  925         printf(
  926             "%p low = %u high = %u first = %u last = %u busy %u chunks = %u\n",
  927             uh, uh->low, uh->high, uh->first, uh->last, uh->busy, uh->alloc);
  928         x = uh->low + uh->first;
  929         TAILQ_FOREACH(up, &uh->head, list) {
  930                 printf("  from = %5u", x);
  931                 print_unr(uh, up);
  932                 if (up->ptr == NULL || up->ptr == uh)
  933                         x += up->len;
  934                 else
  935                         x += NBITS;
  936         }
  937 }
  938 
  939 static void
  940 test_alloc_unr(struct unrhdr *uh, u_int i, char a[])
  941 {
  942         int j;
  943 
  944         if (a[i]) {
  945                 printf("F %u\n", i);
  946                 free_unr(uh, i);
  947                 a[i] = 0;
  948         } else {
  949                 no_alloc = 1;
  950                 j = alloc_unr(uh);
  951                 if (j != -1) {
  952                         a[j] = 1;
  953                         printf("A %d\n", j);
  954                 }
  955                 no_alloc = 0;
  956         }
  957 }
  958 
  959 static void
  960 test_alloc_unr_specific(struct unrhdr *uh, u_int i, char a[])
  961 {
  962         int j;
  963 
  964         j = alloc_unr_specific(uh, i);
  965         if (j == -1) {
  966                 printf("F %u\n", i);
  967                 a[i] = 0;
  968                 free_unr(uh, i);
  969         } else {
  970                 a[i] = 1;
  971                 printf("A %d\n", j);
  972         }
  973 }
  974 
  975 /* Number of unrs to test */
  976 #define NN      10000
  977 
  978 int
  979 main(int argc __unused, const char **argv __unused)
  980 {
  981         struct unrhdr *uh;
  982         u_int i, x, m, j;
  983         char a[NN];
  984 
  985         setbuf(stdout, NULL);
  986         uh = new_unrhdr(0, NN - 1, NULL);
  987         print_unrhdr(uh);
  988 
  989         memset(a, 0, sizeof a);
  990         srandomdev();
  991 
  992         fprintf(stderr, "sizeof(struct unr) %zu\n", sizeof(struct unr));
  993         fprintf(stderr, "sizeof(struct unrb) %zu\n", sizeof(struct unrb));
  994         fprintf(stderr, "sizeof(struct unrhdr) %zu\n", sizeof(struct unrhdr));
  995         fprintf(stderr, "NBITS %d\n", NBITS);
  996         x = 1;
  997         for (m = 0; m < NN * 100; m++) {
  998                 j = random();
  999                 i = (j >> 1) % NN;
 1000 #if 0
 1001                 if (a[i] && (j & 1))
 1002                         continue;
 1003 #endif
 1004                 if ((random() & 1) != 0)
 1005                         test_alloc_unr(uh, i, a);
 1006                 else
 1007                         test_alloc_unr_specific(uh, i, a);
 1008 
 1009                 if (1)  /* XXX: change this for detailed debug printout */
 1010                         print_unrhdr(uh);
 1011                 check_unrhdr(uh, __LINE__);
 1012         }
 1013         for (i = 0; i < NN; i++) {
 1014                 if (a[i]) {
 1015                         printf("C %u\n", i);
 1016                         free_unr(uh, i);
 1017                         print_unrhdr(uh);
 1018                 }
 1019         }
 1020         print_unrhdr(uh);
 1021         delete_unrhdr(uh);
 1022         return (0);
 1023 }
 1024 #endif

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