HAMMER 60I/Many: Mirroring

[dragonfly.git] / sys / kern / subr_alist.c

/*
 * ALIST.C -    Bitmap allocator/deallocator, using a radix tree with hinting.
 *              Unlimited-size allocations, power-of-2 only, power-of-2
 *              aligned results only.
 * 
 * Copyright (c) 2007 The DragonFly Project.  All rights reserved.
 * 
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@backplane.com>
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $DragonFly: src/sys/kern/subr_alist.c,v 1.4 2008/04/23 17:21:08 dillon Exp $
 */
/*
 * This module has been adapted from the BLIST module, which was written
 * by Matthew Dillon many years ago.
 *
 * This module implements a general power-of-2 bitmap allocator/deallocator.
 * All allocations must be in powers of 2 and will return similarly aligned
 * results.  The module does not try to interpret the meaning of a 'block'
 * other then to return ALIST_BLOCK_NONE on an allocation failure.  
 *
 * A maximum of 2 billion blocks is supported so, for example, if one block
 * represented 64 bytes a maximally sized ALIST would represent
 * 128 gigabytes.
 *
 * A radix tree is used to maintain the bitmap and layed out in a manner
 * similar to the blist code.  Meta nodes use a radix of 16 and 2 bits per
 * block while leaf nodes use a radix of 32 and 1 bit per block (stored in
 * a 32 bit bitmap field).  Both meta and leaf nodes have a hint field.
 * This field gives us a hint as to the largest free contiguous range of
 * blocks under the node.  It may contain a value that is too high, but
 * will never contain a value that is too low.  When the radix tree is
 * searched, allocation failures in subtrees update the hint. 
 *
 * The radix tree is layed out recursively using a linear array.  Each meta
 * node is immediately followed (layed out sequentially in memory) by
 * ALIST_META_RADIX lower level nodes.  This is a recursive structure but one
 * that can be easily scanned through a very simple 'skip' calculation.  In
 * order to support large radixes, portions of the tree may reside outside our
 * memory allocation.  We handle this with an early-terminate optimization
 * in the meta-node.  The memory allocation is only large enough to cover
 * the number of blocks requested at creation time even if it must be
 * encompassed in larger root-node radix.
 *
 * This code can be compiled stand-alone for debugging.
 */

#ifdef _KERNEL

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/lock.h>
#include <sys/kernel.h>
#include <sys/alist.h>
#include <sys/malloc.h>
#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/vm_kern.h>
#include <vm/vm_extern.h>
#include <vm/vm_page.h>

#else

#ifndef ALIST_NO_DEBUG
#define ALIST_DEBUG
#endif

#include <sys/types.h>
#include <stdio.h>
#include <assert.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>

#define kmalloc(a,b,c)  malloc(a)
#define kfree(a,b)      free(a)
#define kprintf         printf
#define KKASSERT(exp)   assert(exp)
struct malloc_type;

typedef unsigned int u_daddr_t;

#include <sys/alist.h>

void panic(const char *ctl, ...);

#endif

/*
 * static support functions
 */

static daddr_t alst_leaf_alloc(almeta_t *scan, daddr_t blk, int count);
static daddr_t alst_meta_alloc(almeta_t *scan, daddr_t blk, 
                                daddr_t count, daddr_t radix, int skip);
static void alst_leaf_free(almeta_t *scan, daddr_t relblk, int count);
static void alst_meta_free(almeta_t *scan, daddr_t freeBlk, daddr_t count, 
                                        daddr_t radix, int skip, daddr_t blk);
static daddr_t  alst_radix_init(almeta_t *scan, daddr_t radix, 
                                                int skip, daddr_t count);
#ifndef _KERNEL
static void     alst_radix_print(almeta_t *scan, daddr_t blk, 
                                        daddr_t radix, int skip, int tab);
#endif

/*
 * alist_create() - create a alist capable of handling up to the specified
 *                  number of blocks
 *
 *      blocks must be greater then 0
 *
 *      The smallest alist consists of a single leaf node capable of 
 *      managing ALIST_BMAP_RADIX blocks.
 */

alist_t 
alist_create(daddr_t blocks, struct malloc_type *mtype)
{
        alist_t bl;
        int radix;
        int skip = 0;

        /*
         * Calculate radix and skip field used for scanning.
         */
        radix = ALIST_BMAP_RADIX;

        while (radix < blocks) {
                radix *= ALIST_META_RADIX;
                skip = (skip + 1) * ALIST_META_RADIX;
        }

        bl = kmalloc(sizeof(struct alist), mtype, M_WAITOK);

        bzero(bl, sizeof(*bl));

        bl->bl_blocks = blocks;
        bl->bl_radix = radix;
        bl->bl_skip = skip;
        bl->bl_rootblks = 1 +
            alst_radix_init(NULL, bl->bl_radix, bl->bl_skip, blocks);
        bl->bl_root = kmalloc(sizeof(almeta_t) * bl->bl_rootblks, mtype, M_WAITOK);

#if defined(ALIST_DEBUG)
        kprintf(
                "ALIST representing %d blocks (%d MB of swap)"
                ", requiring %dK (%d bytes) of ram\n",
                bl->bl_blocks,
                bl->bl_blocks * 4 / 1024,
                (bl->bl_rootblks * sizeof(almeta_t) + 1023) / 1024,
                (bl->bl_rootblks * sizeof(almeta_t))
        );
        kprintf("ALIST raw radix tree contains %d records\n", bl->bl_rootblks);
#endif
        alst_radix_init(bl->bl_root, bl->bl_radix, bl->bl_skip, blocks);

        return(bl);
}

void 
alist_destroy(alist_t bl, struct malloc_type *mtype)
{
        kfree(bl->bl_root, mtype);
        kfree(bl, mtype);
}

/*
 * alist_alloc() - reserve space in the block bitmap.  Return the base
 *                 of a contiguous region or ALIST_BLOCK_NONE if space
 *                 could not be allocated.
 */

daddr_t 
alist_alloc(alist_t bl, daddr_t count)
{
        daddr_t blk = ALIST_BLOCK_NONE;

        KKASSERT((count | (count - 1)) == (count << 1) - 1);

        if (bl && count < bl->bl_radix) {
                if (bl->bl_radix == ALIST_BMAP_RADIX)
                        blk = alst_leaf_alloc(bl->bl_root, 0, count);
                else
                        blk = alst_meta_alloc(bl->bl_root, 0, count, bl->bl_radix, bl->bl_skip);
                if (blk != ALIST_BLOCK_NONE)
                        bl->bl_free -= count;
        }
        return(blk);
}

/*
 * alist_free() -       free up space in the block bitmap.  Return the base
 *                      of a contiguous region.  Panic if an inconsistancy is
 *                      found.
 */

void 
alist_free(alist_t bl, daddr_t blkno, daddr_t count)
{
        if (bl) {
                KKASSERT(blkno + count <= bl->bl_blocks);
                if (bl->bl_radix == ALIST_BMAP_RADIX)
                        alst_leaf_free(bl->bl_root, blkno, count);
                else
                        alst_meta_free(bl->bl_root, blkno, count, bl->bl_radix, bl->bl_skip, 0);
                bl->bl_free += count;
        }
}

#ifdef ALIST_DEBUG

/*
 * alist_print()    - dump radix tree
 */

void
alist_print(alist_t bl)
{
        kprintf("ALIST {\n");
        alst_radix_print(bl->bl_root, 0, bl->bl_radix, bl->bl_skip, 4);
        kprintf("}\n");
}

#endif

/************************************************************************
 *                        ALLOCATION SUPPORT FUNCTIONS                  *
 ************************************************************************
 *
 *      These support functions do all the actual work.  They may seem 
 *      rather longish, but that's because I've commented them up.  The
 *      actual code is straight forward.
 *
 */

/*
 * alist_leaf_alloc() - allocate at a leaf in the radix tree (a bitmap).
 *
 *      This is the core of the allocator and is optimized for the 1 block
 *      and the ALIST_BMAP_RADIX block allocation cases.  Other cases are
 *      somewhat slower.  The 1 block allocation case is log2 and extremely
 *      quick.
 */

static daddr_t
alst_leaf_alloc(
        almeta_t *scan,
        daddr_t blk,
        int count
) {
        u_daddr_t orig = scan->bm_bitmap;

        /*
         * Optimize bitmap all-allocated case.  Also, count = 1
         * case assumes at least 1 bit is free in the bitmap, so
         * we have to take care of this case here.
         */
        if (orig == 0) {
                scan->bm_bighint = 0;
                return(ALIST_BLOCK_NONE);
        }

        /*
         * Optimized code to allocate one bit out of the bitmap
         */
        if (count == 1) {
                u_daddr_t mask;
                int j = ALIST_BMAP_RADIX/2;
                int r = 0;

                mask = (u_daddr_t)-1 >> (ALIST_BMAP_RADIX/2);

                while (j) {
                        if ((orig & mask) == 0) {
                            r += j;
                            orig >>= j;
                        }
                        j >>= 1;
                        mask >>= j;
                }
                scan->bm_bitmap &= ~(1 << r);
                return(blk + r);
        }

        /*
         * non-optimized code to allocate N bits out of the bitmap.
         * The more bits, the faster the code runs.  It will run
         * the slowest allocating 2 bits, but since there aren't any
         * memory ops in the core loop (or shouldn't be, anyway),
         * you probably won't notice the difference.
         *
         * Similar to the blist case, the alist code also requires
         * allocations to be power-of-2 sized and aligned to the
         * size of the allocation, which simplifies the algorithm.
         */
        {
                int j;
                int n = ALIST_BMAP_RADIX - count;
                u_daddr_t mask;

                mask = (u_daddr_t)-1 >> n;

                for (j = 0; j <= n; j += count) {
                        if ((orig & mask) == mask) {
                                scan->bm_bitmap &= ~mask;
                                return(blk + j);
                        }
                        mask = mask << count;
                }
        }

        /*
         * We couldn't allocate count in this subtree, update bighint.
         */
        scan->bm_bighint = count - 1;
        return(ALIST_BLOCK_NONE);
}

/*
 * alist_meta_alloc() - allocate at a meta in the radix tree.
 *
 *      Attempt to allocate at a meta node.  If we can't, we update
 *      bighint and return a failure.  Updating bighint optimize future
 *      calls that hit this node.  We have to check for our collapse cases
 *      and we have a few optimizations strewn in as well.
 */

static daddr_t
alst_meta_alloc(
        almeta_t *scan, 
        daddr_t blk,
        daddr_t count,
        daddr_t radix, 
        int skip
) {
        int i;
        u_daddr_t mask;
        u_daddr_t pmask;
        int next_skip = ((u_int)skip / ALIST_META_RADIX);

        /*
         * ALL-ALLOCATED special case
         */
        if (scan->bm_bitmap == 0)  {
                scan->bm_bighint = 0;
                return(ALIST_BLOCK_NONE);
        }

        radix /= ALIST_META_RADIX;

        /*
         * Radix now represents each bitmap entry for this meta node.  If
         * the number of blocks being allocated can be fully represented,
         * we allocate directly out of this meta node.
         *
         * Meta node bitmaps use 2 bits per block.
         *
         *      00      ALL-ALLOCATED
         *      01      PARTIALLY-FREE/PARTIALLY-ALLOCATED
         *      10      (RESERVED)
         *      11      ALL-FREE
         */
        if (count >= radix) {
                int n = count / radix * 2;      /* number of bits */
                int j;

                mask = (u_daddr_t)-1 >> (ALIST_BMAP_RADIX - n);
                for (j = 0; j < ALIST_META_RADIX; j += n / 2) {
                        if ((scan->bm_bitmap & mask) == mask) {
                                scan->bm_bitmap &= ~mask;
                                return(blk + j * radix);
                        }
                        mask <<= n;
                }
                if (scan->bm_bighint >= count)
                        scan->bm_bighint = count >> 1;
                return(ALIST_BLOCK_NONE);
        }

        /*
         * If not we have to recurse.
         */
        mask = 0x00000003;
        pmask = 0x00000001;
        for (i = 1; i <= skip; i += next_skip) {
                if (scan[i].bm_bighint == (daddr_t)-1) {
                        /* 
                         * Terminator
                         */
                        break;
                }

                /*
                 * If the element is marked completely free (11), initialize
                 * the recursion.
                 */
                if ((scan->bm_bitmap & mask) == mask) {
                        scan[i].bm_bitmap = (u_daddr_t)-1;
                        scan[i].bm_bighint = radix;
                } 

                if ((scan->bm_bitmap & mask) == 0) {
                        /*
                         * Object marked completely allocated, recursion
                         * contains garbage.
                         */
                        /* Skip it */
                } else if (count <= scan[i].bm_bighint) {
                        /*
                         * count fits in object
                         */
                        daddr_t r;
                        if (next_skip == 1) {
                                r = alst_leaf_alloc(&scan[i], blk, count);
                        } else {
                                r = alst_meta_alloc(&scan[i], blk, count, radix, next_skip - 1);
                        }
                        if (r != ALIST_BLOCK_NONE) {
                                if (scan[i].bm_bitmap == 0) {
                                        scan->bm_bitmap &= ~mask;
                                } else {
                                        scan->bm_bitmap &= ~mask;
                                        scan->bm_bitmap |= pmask;
                                }
                                return(r);
                        }
                } 
                blk += radix;
                mask <<= 2;
                pmask <<= 2;
        }

        /*
         * We couldn't allocate count in this subtree, update bighint.
         */
        if (scan->bm_bighint >= count)
                scan->bm_bighint = count >> 1;
        return(ALIST_BLOCK_NONE);
}

/*
 * BLST_LEAF_FREE() -   free allocated block from leaf bitmap
 *
 */
static void
alst_leaf_free(
        almeta_t *scan,
        daddr_t blk,
        int count
) {
        /*
         * free some data in this bitmap
         *
         * e.g.
         *      0000111111111110000
         *          \_________/\__/
         *              v        n
         */
        int n = blk & (ALIST_BMAP_RADIX - 1);
        u_daddr_t mask;

        mask = ((u_daddr_t)-1 << n) &
            ((u_daddr_t)-1 >> (ALIST_BMAP_RADIX - count - n));

        if (scan->bm_bitmap & mask)
                panic("alst_radix_free: freeing free block");
        scan->bm_bitmap |= mask;

        /*
         * We could probably do a better job here.  We are required to make
         * bighint at least as large as the biggest contiguous block of 
         * data.  If we just shoehorn it, a little extra overhead will
         * be incured on the next allocation (but only that one typically).
         */
        scan->bm_bighint = ALIST_BMAP_RADIX;
}

/*
 * BLST_META_FREE() - free allocated blocks from radix tree meta info
 *
 *      This support routine frees a range of blocks from the bitmap.
 *      The range must be entirely enclosed by this radix node.  If a
 *      meta node, we break the range down recursively to free blocks
 *      in subnodes (which means that this code can free an arbitrary
 *      range whereas the allocation code cannot allocate an arbitrary
 *      range).
 */

static void 
alst_meta_free(
        almeta_t *scan, 
        daddr_t freeBlk,
        daddr_t count,
        daddr_t radix, 
        int skip,
        daddr_t blk
) {
        int next_skip = ((u_int)skip / ALIST_META_RADIX);
        u_daddr_t mask;
        u_daddr_t pmask;
        int i;

        /*
         * Break the free down into its components.  Because it is so easy
         * to implement, frees are not limited to power-of-2 sizes.
         *
         * Each block in a meta-node bitmap takes two bits.
         */
        radix /= ALIST_META_RADIX;

        i = (freeBlk - blk) / radix;
        blk += i * radix;
        mask = 0x00000003 << (i * 2);
        pmask = 0x00000001 << (i * 2);

        i = i * next_skip + 1;

        while (i <= skip && blk < freeBlk + count) {
                daddr_t v;

                v = blk + radix - freeBlk;
                if (v > count)
                        v = count;

                if (scan->bm_bighint == (daddr_t)-1)
                        panic("alst_meta_free: freeing unexpected range");

                if (freeBlk == blk && count >= radix) {
                        /*
                         * All-free case, no need to update sub-tree
                         */
                        scan->bm_bitmap |= mask;
                        scan->bm_bighint = radix * ALIST_META_RADIX;/*XXX*/
                } else {
                        /*
                         * If we were previously marked all-allocated, fix-up
                         * the next layer so we can recurse down into it.
                         */
                        if ((scan->bm_bitmap & mask) == 0) {
                                scan[i].bm_bitmap = (u_daddr_t)0;
                                scan[i].bm_bighint = 0;
                        } 

                        /*
                         * Recursion case
                         */
                        if (next_skip == 1)
                                alst_leaf_free(&scan[i], freeBlk, v);
                        else
                                alst_meta_free(&scan[i], freeBlk, v, radix, next_skip - 1, blk);
                        if (scan[i].bm_bitmap == (u_daddr_t)-1)
                                scan->bm_bitmap |= mask;
                        else
                                scan->bm_bitmap |= pmask;
                        if (scan->bm_bighint < scan[i].bm_bighint)
                            scan->bm_bighint = scan[i].bm_bighint;
                }
                mask <<= 2;
                pmask <<= 2;
                count -= v;
                freeBlk += v;
                blk += radix;
                i += next_skip;
        }
}

/*
 * BLST_RADIX_INIT() - initialize radix tree
 *
 *      Initialize our meta structures and bitmaps and calculate the exact
 *      amount of space required to manage 'count' blocks - this space may
 *      be considerably less then the calculated radix due to the large
 *      RADIX values we use.
 */

static daddr_t  
alst_radix_init(almeta_t *scan, daddr_t radix, int skip, daddr_t count)
{
        int i;
        int next_skip;
        daddr_t memindex = 0;
        u_daddr_t mask;
        u_daddr_t pmask;

        /*
         * Leaf node
         */
        if (radix == ALIST_BMAP_RADIX) {
                if (scan) {
                        scan->bm_bighint = 0;
                        scan->bm_bitmap = 0;
                }
                return(memindex);
        }

        /*
         * Meta node.  If allocating the entire object we can special
         * case it.  However, we need to figure out how much memory
         * is required to manage 'count' blocks, so we continue on anyway.
         */

        if (scan) {
                scan->bm_bighint = 0;
                scan->bm_bitmap = 0;
        }

        radix /= ALIST_META_RADIX;
        next_skip = ((u_int)skip / ALIST_META_RADIX);
        mask = 0x00000003;
        pmask = 0x00000001;

        for (i = 1; i <= skip; i += next_skip) {
                if (count >= radix) {
                        /*
                         * Allocate the entire object
                         */
                        memindex = i + alst_radix_init(
                            ((scan) ? &scan[i] : NULL),
                            radix,
                            next_skip - 1,
                            radix
                        );
                        count -= radix;
                        /* already marked as wholely allocated */
                } else if (count > 0) {
                        /*
                         * Allocate a partial object
                         */
                        memindex = i + alst_radix_init(
                            ((scan) ? &scan[i] : NULL),
                            radix,
                            next_skip - 1,
                            count
                        );
                        count = 0;

                        /*
                         * Mark as partially allocated
                         */
                        if (scan)
                                scan->bm_bitmap |= pmask;
                } else {
                        /*
                         * Add terminator and break out
                         */
                        if (scan)
                                scan[i].bm_bighint = (daddr_t)-1;
                        /* already marked as wholely allocated */
                        break;
                }
                mask <<= 2;
                pmask <<= 2;
        }
        if (memindex < i)
                memindex = i;
        return(memindex);
}

#ifdef ALIST_DEBUG

static void     
alst_radix_print(almeta_t *scan, daddr_t blk, daddr_t radix, int skip, int tab)
{
        int i;
        int next_skip;
        int lastState = 0;
        u_daddr_t mask;

        if (radix == ALIST_BMAP_RADIX) {
                kprintf(
                    "%*.*s(%04x,%d): bitmap %08x big=%d\n", 
                    tab, tab, "",
                    blk, radix,
                    scan->bm_bitmap,
                    scan->bm_bighint
                );
                return;
        }

        if (scan->bm_bitmap == 0) {
                kprintf(
                    "%*.*s(%04x,%d) ALL ALLOCATED\n",
                    tab, tab, "",
                    blk,
                    radix
                );
                return;
        }
        if (scan->bm_bitmap == (u_daddr_t)-1) {
                kprintf(
                    "%*.*s(%04x,%d) ALL FREE\n",
                    tab, tab, "",
                    blk,
                    radix
                );
                return;
        }

        kprintf(
            "%*.*s(%04x,%d): subtree (%d) bitmap=%08x big=%d {\n",
            tab, tab, "",
            blk, radix,
            radix,
            scan->bm_bitmap,
            scan->bm_bighint
        );

        radix /= ALIST_META_RADIX;
        next_skip = ((u_int)skip / ALIST_META_RADIX);
        tab += 4;
        mask = 0x00000003;

        for (i = 1; i <= skip; i += next_skip) {
                if (scan[i].bm_bighint == (daddr_t)-1) {
                        kprintf(
                            "%*.*s(%04x,%d): Terminator\n",
                            tab, tab, "",
                            blk, radix
                        );
                        lastState = 0;
                        break;
                }
                if ((scan->bm_bitmap & mask) == mask) {
                        kprintf(
                            "%*.*s(%04x,%d): ALL FREE\n",
                            tab, tab, "",
                            blk, radix
                        );
                } else if ((scan->bm_bitmap & mask) == 0) {
                        kprintf(
                            "%*.*s(%04x,%d): ALL ALLOCATED\n",
                            tab, tab, "",
                            blk, radix
                        );
                } else {
                        alst_radix_print(
                            &scan[i],
                            blk,
                            radix,
                            next_skip - 1,
                            tab
                        );
                }
                blk += radix;
                mask <<= 2;
        }
        tab -= 4;

        kprintf(
            "%*.*s}\n",
            tab, tab, ""
        );
}

#endif

#ifdef ALIST_DEBUG

int
main(int ac, char **av)
{
        int size = 1024;
        int i;
        alist_t bl;

        for (i = 1; i < ac; ++i) {
                const char *ptr = av[i];
                if (*ptr != '-') {
                        size = strtol(ptr, NULL, 0);
                        continue;
                }
                ptr += 2;
                fprintf(stderr, "Bad option: %s\n", ptr - 2);
                exit(1);
        }
        bl = alist_create(size, NULL);
        alist_free(bl, 0, size);

        for (;;) {
                char buf[1024];
                daddr_t da = 0;
                daddr_t count = 0;


                kprintf("%d/%d/%d> ", bl->bl_free, size, bl->bl_radix);
                fflush(stdout);
                if (fgets(buf, sizeof(buf), stdin) == NULL)
                        break;
                switch(buf[0]) {
                case 'p':
                        alist_print(bl);
                        break;
                case 'a':
                        if (sscanf(buf + 1, "%d", &count) == 1) {
                                daddr_t blk = alist_alloc(bl, count);
                                kprintf("    R=%04x\n", blk);
                        } else {
                                kprintf("?\n");
                        }
                        break;
                case 'f':
                        if (sscanf(buf + 1, "%x %d", &da, &count) == 2) {
                                alist_free(bl, da, count);
                        } else {
                                kprintf("?\n");
                        }
                        break;
                case '?':
                case 'h':
                        puts(
                            "p          -print\n"
                            "a %d       -allocate\n"
                            "f %x %d    -free\n"
                            "h/?        -help"
                        );
                        break;
                default:
                        kprintf("?\n");
                        break;
                }
        }
        return(0);
}

void
panic(const char *ctl, ...)
{
        __va_list va;

        __va_start(va, ctl);
        vfprintf(stderr, ctl, va);
        fprintf(stderr, "\n");
        __va_end(va);
        exit(1);
}

#endif