ext4: fix a potential fiemap/page fault deadlock w/ inline_data

[linux/fpc-iii.git] / fs / ufs / balloc.c

/*
 *  linux/fs/ufs/balloc.c
 *
 * Copyright (C) 1998
 * Daniel Pirkl <daniel.pirkl@email.cz>
 * Charles University, Faculty of Mathematics and Physics
 *
 * UFS2 write support Evgeniy Dushistov <dushistov@mail.ru>, 2007
 */

#include <linux/fs.h>
#include <linux/stat.h>
#include <linux/time.h>
#include <linux/string.h>
#include <linux/buffer_head.h>
#include <linux/capability.h>
#include <linux/bitops.h>
#include <asm/byteorder.h>

#include "ufs_fs.h"
#include "ufs.h"
#include "swab.h"
#include "util.h"

#define INVBLOCK ((u64)-1L)

static u64 ufs_add_fragments(struct inode *, u64, unsigned, unsigned);
static u64 ufs_alloc_fragments(struct inode *, unsigned, u64, unsigned, int *);
static u64 ufs_alloccg_block(struct inode *, struct ufs_cg_private_info *, u64, int *);
static u64 ufs_bitmap_search (struct super_block *, struct ufs_cg_private_info *, u64, unsigned);
static unsigned char ufs_fragtable_8fpb[], ufs_fragtable_other[];
static void ufs_clusteracct(struct super_block *, struct ufs_cg_private_info *, unsigned, int);

/*
 * Free 'count' fragments from fragment number 'fragment'
 */
void ufs_free_fragments(struct inode *inode, u64 fragment, unsigned count)
{
        struct super_block * sb;
        struct ufs_sb_private_info * uspi;
        struct ufs_cg_private_info * ucpi;
        struct ufs_cylinder_group * ucg;
        unsigned cgno, bit, end_bit, bbase, blkmap, i;
        u64 blkno;
        
        sb = inode->i_sb;
        uspi = UFS_SB(sb)->s_uspi;
        
        UFSD("ENTER, fragment %llu, count %u\n",
             (unsigned long long)fragment, count);
        
        if (ufs_fragnum(fragment) + count > uspi->s_fpg)
                ufs_error (sb, "ufs_free_fragments", "internal error");

        mutex_lock(&UFS_SB(sb)->s_lock);
        
        cgno = ufs_dtog(uspi, fragment);
        bit = ufs_dtogd(uspi, fragment);
        if (cgno >= uspi->s_ncg) {
                ufs_panic (sb, "ufs_free_fragments", "freeing blocks are outside device");
                goto failed;
        }
                
        ucpi = ufs_load_cylinder (sb, cgno);
        if (!ucpi) 
                goto failed;
        ucg = ubh_get_ucg (UCPI_UBH(ucpi));
        if (!ufs_cg_chkmagic(sb, ucg)) {
                ufs_panic (sb, "ufs_free_fragments", "internal error, bad magic number on cg %u", cgno);
                goto failed;
        }

        end_bit = bit + count;
        bbase = ufs_blknum (bit);
        blkmap = ubh_blkmap (UCPI_UBH(ucpi), ucpi->c_freeoff, bbase);
        ufs_fragacct (sb, blkmap, ucg->cg_frsum, -1);
        for (i = bit; i < end_bit; i++) {
                if (ubh_isclr (UCPI_UBH(ucpi), ucpi->c_freeoff, i))
                        ubh_setbit (UCPI_UBH(ucpi), ucpi->c_freeoff, i);
                else 
                        ufs_error (sb, "ufs_free_fragments",
                                   "bit already cleared for fragment %u", i);
        }

        inode_sub_bytes(inode, count << uspi->s_fshift);
        fs32_add(sb, &ucg->cg_cs.cs_nffree, count);
        uspi->cs_total.cs_nffree += count;
        fs32_add(sb, &UFS_SB(sb)->fs_cs(cgno).cs_nffree, count);
        blkmap = ubh_blkmap (UCPI_UBH(ucpi), ucpi->c_freeoff, bbase);
        ufs_fragacct(sb, blkmap, ucg->cg_frsum, 1);

        /*
         * Trying to reassemble free fragments into block
         */
        blkno = ufs_fragstoblks (bbase);
        if (ubh_isblockset(UCPI_UBH(ucpi), ucpi->c_freeoff, blkno)) {
                fs32_sub(sb, &ucg->cg_cs.cs_nffree, uspi->s_fpb);
                uspi->cs_total.cs_nffree -= uspi->s_fpb;
                fs32_sub(sb, &UFS_SB(sb)->fs_cs(cgno).cs_nffree, uspi->s_fpb);
                if ((UFS_SB(sb)->s_flags & UFS_CG_MASK) == UFS_CG_44BSD)
                        ufs_clusteracct (sb, ucpi, blkno, 1);
                fs32_add(sb, &ucg->cg_cs.cs_nbfree, 1);
                uspi->cs_total.cs_nbfree++;
                fs32_add(sb, &UFS_SB(sb)->fs_cs(cgno).cs_nbfree, 1);
                if (uspi->fs_magic != UFS2_MAGIC) {
                        unsigned cylno = ufs_cbtocylno (bbase);

                        fs16_add(sb, &ubh_cg_blks(ucpi, cylno,
                                                  ufs_cbtorpos(bbase)), 1);
                        fs32_add(sb, &ubh_cg_blktot(ucpi, cylno), 1);
                }
        }
        
        ubh_mark_buffer_dirty (USPI_UBH(uspi));
        ubh_mark_buffer_dirty (UCPI_UBH(ucpi));
        if (sb->s_flags & MS_SYNCHRONOUS)
                ubh_sync_block(UCPI_UBH(ucpi));
        ufs_mark_sb_dirty(sb);

        mutex_unlock(&UFS_SB(sb)->s_lock);
        UFSD("EXIT\n");
        return;

failed:
        mutex_unlock(&UFS_SB(sb)->s_lock);
        UFSD("EXIT (FAILED)\n");
        return;
}

/*
 * Free 'count' fragments from fragment number 'fragment' (free whole blocks)
 */
void ufs_free_blocks(struct inode *inode, u64 fragment, unsigned count)
{
        struct super_block * sb;
        struct ufs_sb_private_info * uspi;
        struct ufs_cg_private_info * ucpi;
        struct ufs_cylinder_group * ucg;
        unsigned overflow, cgno, bit, end_bit, i;
        u64 blkno;
        
        sb = inode->i_sb;
        uspi = UFS_SB(sb)->s_uspi;

        UFSD("ENTER, fragment %llu, count %u\n",
             (unsigned long long)fragment, count);
        
        if ((fragment & uspi->s_fpbmask) || (count & uspi->s_fpbmask)) {
                ufs_error (sb, "ufs_free_blocks", "internal error, "
                           "fragment %llu, count %u\n",
                           (unsigned long long)fragment, count);
                goto failed;
        }

        mutex_lock(&UFS_SB(sb)->s_lock);
        
do_more:
        overflow = 0;
        cgno = ufs_dtog(uspi, fragment);
        bit = ufs_dtogd(uspi, fragment);
        if (cgno >= uspi->s_ncg) {
                ufs_panic (sb, "ufs_free_blocks", "freeing blocks are outside device");
                goto failed_unlock;
        }
        end_bit = bit + count;
        if (end_bit > uspi->s_fpg) {
                overflow = bit + count - uspi->s_fpg;
                count -= overflow;
                end_bit -= overflow;
        }

        ucpi = ufs_load_cylinder (sb, cgno);
        if (!ucpi) 
                goto failed_unlock;
        ucg = ubh_get_ucg (UCPI_UBH(ucpi));
        if (!ufs_cg_chkmagic(sb, ucg)) {
                ufs_panic (sb, "ufs_free_blocks", "internal error, bad magic number on cg %u", cgno);
                goto failed_unlock;
        }

        for (i = bit; i < end_bit; i += uspi->s_fpb) {
                blkno = ufs_fragstoblks(i);
                if (ubh_isblockset(UCPI_UBH(ucpi), ucpi->c_freeoff, blkno)) {
                        ufs_error(sb, "ufs_free_blocks", "freeing free fragment");
                }
                ubh_setblock(UCPI_UBH(ucpi), ucpi->c_freeoff, blkno);
                inode_sub_bytes(inode, uspi->s_fpb << uspi->s_fshift);
                if ((UFS_SB(sb)->s_flags & UFS_CG_MASK) == UFS_CG_44BSD)
                        ufs_clusteracct (sb, ucpi, blkno, 1);

                fs32_add(sb, &ucg->cg_cs.cs_nbfree, 1);
                uspi->cs_total.cs_nbfree++;
                fs32_add(sb, &UFS_SB(sb)->fs_cs(cgno).cs_nbfree, 1);

                if (uspi->fs_magic != UFS2_MAGIC) {
                        unsigned cylno = ufs_cbtocylno(i);

                        fs16_add(sb, &ubh_cg_blks(ucpi, cylno,
                                                  ufs_cbtorpos(i)), 1);
                        fs32_add(sb, &ubh_cg_blktot(ucpi, cylno), 1);
                }
        }

        ubh_mark_buffer_dirty (USPI_UBH(uspi));
        ubh_mark_buffer_dirty (UCPI_UBH(ucpi));
        if (sb->s_flags & MS_SYNCHRONOUS)
                ubh_sync_block(UCPI_UBH(ucpi));

        if (overflow) {
                fragment += count;
                count = overflow;
                goto do_more;
        }

        ufs_mark_sb_dirty(sb);
        mutex_unlock(&UFS_SB(sb)->s_lock);
        UFSD("EXIT\n");
        return;

failed_unlock:
        mutex_unlock(&UFS_SB(sb)->s_lock);
failed:
        UFSD("EXIT (FAILED)\n");
        return;
}

/*
 * Modify inode page cache in such way:
 * have - blocks with b_blocknr equal to oldb...oldb+count-1
 * get - blocks with b_blocknr equal to newb...newb+count-1
 * also we suppose that oldb...oldb+count-1 blocks
 * situated at the end of file.
 *
 * We can come here from ufs_writepage or ufs_prepare_write,
 * locked_page is argument of these functions, so we already lock it.
 */
static void ufs_change_blocknr(struct inode *inode, sector_t beg,
                               unsigned int count, sector_t oldb,
                               sector_t newb, struct page *locked_page)
{
        const unsigned blks_per_page =
                1 << (PAGE_CACHE_SHIFT - inode->i_blkbits);
        const unsigned mask = blks_per_page - 1;
        struct address_space * const mapping = inode->i_mapping;
        pgoff_t index, cur_index, last_index;
        unsigned pos, j, lblock;
        sector_t end, i;
        struct page *page;
        struct buffer_head *head, *bh;

        UFSD("ENTER, ino %lu, count %u, oldb %llu, newb %llu\n",
              inode->i_ino, count,
             (unsigned long long)oldb, (unsigned long long)newb);

        BUG_ON(!locked_page);
        BUG_ON(!PageLocked(locked_page));

        cur_index = locked_page->index;
        end = count + beg;
        last_index = end >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
        for (i = beg; i < end; i = (i | mask) + 1) {
                index = i >> (PAGE_CACHE_SHIFT - inode->i_blkbits);

                if (likely(cur_index != index)) {
                        page = ufs_get_locked_page(mapping, index);
                        if (!page)/* it was truncated */
                                continue;
                        if (IS_ERR(page)) {/* or EIO */
                                ufs_error(inode->i_sb, __func__,
                                          "read of page %llu failed\n",
                                          (unsigned long long)index);
                                continue;
                        }
                } else
                        page = locked_page;

                head = page_buffers(page);
                bh = head;
                pos = i & mask;
                for (j = 0; j < pos; ++j)
                        bh = bh->b_this_page;


                if (unlikely(index == last_index))
                        lblock = end & mask;
                else
                        lblock = blks_per_page;

                do {
                        if (j >= lblock)
                                break;
                        pos = (i - beg) + j;

                        if (!buffer_mapped(bh))
                                        map_bh(bh, inode->i_sb, oldb + pos);
                        if (!buffer_uptodate(bh)) {
                                ll_rw_block(READ, 1, &bh);
                                wait_on_buffer(bh);
                                if (!buffer_uptodate(bh)) {
                                        ufs_error(inode->i_sb, __func__,
                                                  "read of block failed\n");
                                        break;
                                }
                        }

                        UFSD(" change from %llu to %llu, pos %u\n",
                             (unsigned long long)(pos + oldb),
                             (unsigned long long)(pos + newb), pos);

                        bh->b_blocknr = newb + pos;
                        unmap_underlying_metadata(bh->b_bdev,
                                                  bh->b_blocknr);
                        mark_buffer_dirty(bh);
                        ++j;
                        bh = bh->b_this_page;
                } while (bh != head);

                if (likely(cur_index != index))
                        ufs_put_locked_page(page);
        }
        UFSD("EXIT\n");
}

static void ufs_clear_frags(struct inode *inode, sector_t beg, unsigned int n,
                            int sync)
{
        struct buffer_head *bh;
        sector_t end = beg + n;

        for (; beg < end; ++beg) {
                bh = sb_getblk(inode->i_sb, beg);
                lock_buffer(bh);
                memset(bh->b_data, 0, inode->i_sb->s_blocksize);
                set_buffer_uptodate(bh);
                mark_buffer_dirty(bh);
                unlock_buffer(bh);
                if (IS_SYNC(inode) || sync)
                        sync_dirty_buffer(bh);
                brelse(bh);
        }
}

u64 ufs_new_fragments(struct inode *inode, void *p, u64 fragment,
                           u64 goal, unsigned count, int *err,
                           struct page *locked_page)
{
        struct super_block * sb;
        struct ufs_sb_private_info * uspi;
        struct ufs_super_block_first * usb1;
        unsigned cgno, oldcount, newcount;
        u64 tmp, request, result;
        
        UFSD("ENTER, ino %lu, fragment %llu, goal %llu, count %u\n",
             inode->i_ino, (unsigned long long)fragment,
             (unsigned long long)goal, count);
        
        sb = inode->i_sb;
        uspi = UFS_SB(sb)->s_uspi;
        usb1 = ubh_get_usb_first(uspi);
        *err = -ENOSPC;

        mutex_lock(&UFS_SB(sb)->s_lock);
        tmp = ufs_data_ptr_to_cpu(sb, p);

        if (count + ufs_fragnum(fragment) > uspi->s_fpb) {
                ufs_warning(sb, "ufs_new_fragments", "internal warning"
                            " fragment %llu, count %u",
                            (unsigned long long)fragment, count);
                count = uspi->s_fpb - ufs_fragnum(fragment); 
        }
        oldcount = ufs_fragnum (fragment);
        newcount = oldcount + count;

        /*
         * Somebody else has just allocated our fragments
         */
        if (oldcount) {
                if (!tmp) {
                        ufs_error(sb, "ufs_new_fragments", "internal error, "
                                  "fragment %llu, tmp %llu\n",
                                  (unsigned long long)fragment,
                                  (unsigned long long)tmp);
                        mutex_unlock(&UFS_SB(sb)->s_lock);
                        return INVBLOCK;
                }
                if (fragment < UFS_I(inode)->i_lastfrag) {
                        UFSD("EXIT (ALREADY ALLOCATED)\n");
                        mutex_unlock(&UFS_SB(sb)->s_lock);
                        return 0;
                }
        }
        else {
                if (tmp) {
                        UFSD("EXIT (ALREADY ALLOCATED)\n");
                        mutex_unlock(&UFS_SB(sb)->s_lock);
                        return 0;
                }
        }

        /*
         * There is not enough space for user on the device
         */
        if (!capable(CAP_SYS_RESOURCE) && ufs_freespace(uspi, UFS_MINFREE) <= 0) {
                mutex_unlock(&UFS_SB(sb)->s_lock);
                UFSD("EXIT (FAILED)\n");
                return 0;
        }

        if (goal >= uspi->s_size) 
                goal = 0;
        if (goal == 0) 
                cgno = ufs_inotocg (inode->i_ino);
        else
                cgno = ufs_dtog(uspi, goal);
         
        /*
         * allocate new fragment
         */
        if (oldcount == 0) {
                result = ufs_alloc_fragments (inode, cgno, goal, count, err);
                if (result) {
                        ufs_clear_frags(inode, result + oldcount,
                                        newcount - oldcount, locked_page != NULL);
                        write_seqlock(&UFS_I(inode)->meta_lock);
                        ufs_cpu_to_data_ptr(sb, p, result);
                        write_sequnlock(&UFS_I(inode)->meta_lock);
                        *err = 0;
                        UFS_I(inode)->i_lastfrag =
                                max(UFS_I(inode)->i_lastfrag, fragment + count);
                }
                mutex_unlock(&UFS_SB(sb)->s_lock);
                UFSD("EXIT, result %llu\n", (unsigned long long)result);
                return result;
        }

        /*
         * resize block
         */
        result = ufs_add_fragments(inode, tmp, oldcount, newcount);
        if (result) {
                *err = 0;
                UFS_I(inode)->i_lastfrag = max(UFS_I(inode)->i_lastfrag,
                                                fragment + count);
                ufs_clear_frags(inode, result + oldcount, newcount - oldcount,
                                locked_page != NULL);
                mutex_unlock(&UFS_SB(sb)->s_lock);
                UFSD("EXIT, result %llu\n", (unsigned long long)result);
                return result;
        }

        /*
         * allocate new block and move data
         */
        switch (fs32_to_cpu(sb, usb1->fs_optim)) {
            case UFS_OPTSPACE:
                request = newcount;
                if (uspi->s_minfree < 5 || uspi->cs_total.cs_nffree
                    > uspi->s_dsize * uspi->s_minfree / (2 * 100))
                        break;
                usb1->fs_optim = cpu_to_fs32(sb, UFS_OPTTIME);
                break;
            default:
                usb1->fs_optim = cpu_to_fs32(sb, UFS_OPTTIME);
        
            case UFS_OPTTIME:
                request = uspi->s_fpb;
                if (uspi->cs_total.cs_nffree < uspi->s_dsize *
                    (uspi->s_minfree - 2) / 100)
                        break;
                usb1->fs_optim = cpu_to_fs32(sb, UFS_OPTTIME);
                break;
        }
        result = ufs_alloc_fragments (inode, cgno, goal, request, err);
        if (result) {
                ufs_clear_frags(inode, result + oldcount, newcount - oldcount,
                                locked_page != NULL);
                ufs_change_blocknr(inode, fragment - oldcount, oldcount,
                                   uspi->s_sbbase + tmp,
                                   uspi->s_sbbase + result, locked_page);
                write_seqlock(&UFS_I(inode)->meta_lock);
                ufs_cpu_to_data_ptr(sb, p, result);
                write_sequnlock(&UFS_I(inode)->meta_lock);
                *err = 0;
                UFS_I(inode)->i_lastfrag = max(UFS_I(inode)->i_lastfrag,
                                                fragment + count);
                mutex_unlock(&UFS_SB(sb)->s_lock);
                if (newcount < request)
                        ufs_free_fragments (inode, result + newcount, request - newcount);
                ufs_free_fragments (inode, tmp, oldcount);
                UFSD("EXIT, result %llu\n", (unsigned long long)result);
                return result;
        }

        mutex_unlock(&UFS_SB(sb)->s_lock);
        UFSD("EXIT (FAILED)\n");
        return 0;
}               

static bool try_add_frags(struct inode *inode, unsigned frags)
{
        unsigned size = frags * i_blocksize(inode);
        spin_lock(&inode->i_lock);
        __inode_add_bytes(inode, size);
        if (unlikely((u32)inode->i_blocks != inode->i_blocks)) {
                __inode_sub_bytes(inode, size);
                spin_unlock(&inode->i_lock);
                return false;
        }
        spin_unlock(&inode->i_lock);
        return true;
}

static u64 ufs_add_fragments(struct inode *inode, u64 fragment,
                             unsigned oldcount, unsigned newcount)
{
        struct super_block * sb;
        struct ufs_sb_private_info * uspi;
        struct ufs_cg_private_info * ucpi;
        struct ufs_cylinder_group * ucg;
        unsigned cgno, fragno, fragoff, count, fragsize, i;
        
        UFSD("ENTER, fragment %llu, oldcount %u, newcount %u\n",
             (unsigned long long)fragment, oldcount, newcount);
        
        sb = inode->i_sb;
        uspi = UFS_SB(sb)->s_uspi;
        count = newcount - oldcount;
        
        cgno = ufs_dtog(uspi, fragment);
        if (fs32_to_cpu(sb, UFS_SB(sb)->fs_cs(cgno).cs_nffree) < count)
                return 0;
        if ((ufs_fragnum (fragment) + newcount) > uspi->s_fpb)
                return 0;
        ucpi = ufs_load_cylinder (sb, cgno);
        if (!ucpi)
                return 0;
        ucg = ubh_get_ucg (UCPI_UBH(ucpi));
        if (!ufs_cg_chkmagic(sb, ucg)) {
                ufs_panic (sb, "ufs_add_fragments",
                        "internal error, bad magic number on cg %u", cgno);
                return 0;
        }

        fragno = ufs_dtogd(uspi, fragment);
        fragoff = ufs_fragnum (fragno);
        for (i = oldcount; i < newcount; i++)
                if (ubh_isclr (UCPI_UBH(ucpi), ucpi->c_freeoff, fragno + i))
                        return 0;

        if (!try_add_frags(inode, count))
                return 0;
        /*
         * Block can be extended
         */
        ucg->cg_time = cpu_to_fs32(sb, get_seconds());
        for (i = newcount; i < (uspi->s_fpb - fragoff); i++)
                if (ubh_isclr (UCPI_UBH(ucpi), ucpi->c_freeoff, fragno + i))
                        break;
        fragsize = i - oldcount;
        if (!fs32_to_cpu(sb, ucg->cg_frsum[fragsize]))
                ufs_panic (sb, "ufs_add_fragments",
                        "internal error or corrupted bitmap on cg %u", cgno);
        fs32_sub(sb, &ucg->cg_frsum[fragsize], 1);
        if (fragsize != count)
                fs32_add(sb, &ucg->cg_frsum[fragsize - count], 1);
        for (i = oldcount; i < newcount; i++)
                ubh_clrbit (UCPI_UBH(ucpi), ucpi->c_freeoff, fragno + i);

        fs32_sub(sb, &ucg->cg_cs.cs_nffree, count);
        fs32_sub(sb, &UFS_SB(sb)->fs_cs(cgno).cs_nffree, count);
        uspi->cs_total.cs_nffree -= count;
        
        ubh_mark_buffer_dirty (USPI_UBH(uspi));
        ubh_mark_buffer_dirty (UCPI_UBH(ucpi));
        if (sb->s_flags & MS_SYNCHRONOUS)
                ubh_sync_block(UCPI_UBH(ucpi));
        ufs_mark_sb_dirty(sb);

        UFSD("EXIT, fragment %llu\n", (unsigned long long)fragment);
        
        return fragment;
}

#define UFS_TEST_FREE_SPACE_CG \
        ucg = (struct ufs_cylinder_group *) UFS_SB(sb)->s_ucg[cgno]->b_data; \
        if (fs32_to_cpu(sb, ucg->cg_cs.cs_nbfree)) \
                goto cg_found; \
        for (k = count; k < uspi->s_fpb; k++) \
                if (fs32_to_cpu(sb, ucg->cg_frsum[k])) \
                        goto cg_found; 

static u64 ufs_alloc_fragments(struct inode *inode, unsigned cgno,
                               u64 goal, unsigned count, int *err)
{
        struct super_block * sb;
        struct ufs_sb_private_info * uspi;
        struct ufs_cg_private_info * ucpi;
        struct ufs_cylinder_group * ucg;
        unsigned oldcg, i, j, k, allocsize;
        u64 result;
        
        UFSD("ENTER, ino %lu, cgno %u, goal %llu, count %u\n",
             inode->i_ino, cgno, (unsigned long long)goal, count);

        sb = inode->i_sb;
        uspi = UFS_SB(sb)->s_uspi;
        oldcg = cgno;
        
        /*
         * 1. searching on preferred cylinder group
         */
        UFS_TEST_FREE_SPACE_CG

        /*
         * 2. quadratic rehash
         */
        for (j = 1; j < uspi->s_ncg; j *= 2) {
                cgno += j;
                if (cgno >= uspi->s_ncg) 
                        cgno -= uspi->s_ncg;
                UFS_TEST_FREE_SPACE_CG
        }

        /*
         * 3. brute force search
         * We start at i = 2 ( 0 is checked at 1.step, 1 at 2.step )
         */
        cgno = (oldcg + 1) % uspi->s_ncg;
        for (j = 2; j < uspi->s_ncg; j++) {
                cgno++;
                if (cgno >= uspi->s_ncg)
                        cgno = 0;
                UFS_TEST_FREE_SPACE_CG
        }
        
        UFSD("EXIT (FAILED)\n");
        return 0;

cg_found:
        ucpi = ufs_load_cylinder (sb, cgno);
        if (!ucpi)
                return 0;
        ucg = ubh_get_ucg (UCPI_UBH(ucpi));
        if (!ufs_cg_chkmagic(sb, ucg)) 
                ufs_panic (sb, "ufs_alloc_fragments",
                        "internal error, bad magic number on cg %u", cgno);
        ucg->cg_time = cpu_to_fs32(sb, get_seconds());

        if (count == uspi->s_fpb) {
                result = ufs_alloccg_block (inode, ucpi, goal, err);
                if (result == INVBLOCK)
                        return 0;
                goto succed;
        }

        for (allocsize = count; allocsize < uspi->s_fpb; allocsize++)
                if (fs32_to_cpu(sb, ucg->cg_frsum[allocsize]) != 0)
                        break;
        
        if (allocsize == uspi->s_fpb) {
                result = ufs_alloccg_block (inode, ucpi, goal, err);
                if (result == INVBLOCK)
                        return 0;
                goal = ufs_dtogd(uspi, result);
                for (i = count; i < uspi->s_fpb; i++)
                        ubh_setbit (UCPI_UBH(ucpi), ucpi->c_freeoff, goal + i);
                i = uspi->s_fpb - count;

                inode_sub_bytes(inode, i << uspi->s_fshift);
                fs32_add(sb, &ucg->cg_cs.cs_nffree, i);
                uspi->cs_total.cs_nffree += i;
                fs32_add(sb, &UFS_SB(sb)->fs_cs(cgno).cs_nffree, i);
                fs32_add(sb, &ucg->cg_frsum[i], 1);
                goto succed;
        }

        result = ufs_bitmap_search (sb, ucpi, goal, allocsize);
        if (result == INVBLOCK)
                return 0;
        if (!try_add_frags(inode, count))
                return 0;
        for (i = 0; i < count; i++)
                ubh_clrbit (UCPI_UBH(ucpi), ucpi->c_freeoff, result + i);
        
        fs32_sub(sb, &ucg->cg_cs.cs_nffree, count);
        uspi->cs_total.cs_nffree -= count;
        fs32_sub(sb, &UFS_SB(sb)->fs_cs(cgno).cs_nffree, count);
        fs32_sub(sb, &ucg->cg_frsum[allocsize], 1);

        if (count != allocsize)
                fs32_add(sb, &ucg->cg_frsum[allocsize - count], 1);

succed:
        ubh_mark_buffer_dirty (USPI_UBH(uspi));
        ubh_mark_buffer_dirty (UCPI_UBH(ucpi));
        if (sb->s_flags & MS_SYNCHRONOUS)
                ubh_sync_block(UCPI_UBH(ucpi));
        ufs_mark_sb_dirty(sb);

        result += cgno * uspi->s_fpg;
        UFSD("EXIT3, result %llu\n", (unsigned long long)result);
        return result;
}

static u64 ufs_alloccg_block(struct inode *inode,
                             struct ufs_cg_private_info *ucpi,
                             u64 goal, int *err)
{
        struct super_block * sb;
        struct ufs_sb_private_info * uspi;
        struct ufs_cylinder_group * ucg;
        u64 result, blkno;

        UFSD("ENTER, goal %llu\n", (unsigned long long)goal);

        sb = inode->i_sb;
        uspi = UFS_SB(sb)->s_uspi;
        ucg = ubh_get_ucg(UCPI_UBH(ucpi));

        if (goal == 0) {
                goal = ucpi->c_rotor;
                goto norot;
        }
        goal = ufs_blknum (goal);
        goal = ufs_dtogd(uspi, goal);
        
        /*
         * If the requested block is available, use it.
         */
        if (ubh_isblockset(UCPI_UBH(ucpi), ucpi->c_freeoff, ufs_fragstoblks(goal))) {
                result = goal;
                goto gotit;
        }
        
norot:  
        result = ufs_bitmap_search (sb, ucpi, goal, uspi->s_fpb);
        if (result == INVBLOCK)
                return INVBLOCK;
        ucpi->c_rotor = result;
gotit:
        if (!try_add_frags(inode, uspi->s_fpb))
                return 0;
        blkno = ufs_fragstoblks(result);
        ubh_clrblock (UCPI_UBH(ucpi), ucpi->c_freeoff, blkno);
        if ((UFS_SB(sb)->s_flags & UFS_CG_MASK) == UFS_CG_44BSD)
                ufs_clusteracct (sb, ucpi, blkno, -1);

        fs32_sub(sb, &ucg->cg_cs.cs_nbfree, 1);
        uspi->cs_total.cs_nbfree--;
        fs32_sub(sb, &UFS_SB(sb)->fs_cs(ucpi->c_cgx).cs_nbfree, 1);

        if (uspi->fs_magic != UFS2_MAGIC) {
                unsigned cylno = ufs_cbtocylno((unsigned)result);

                fs16_sub(sb, &ubh_cg_blks(ucpi, cylno,
                                          ufs_cbtorpos((unsigned)result)), 1);
                fs32_sub(sb, &ubh_cg_blktot(ucpi, cylno), 1);
        }
        
        UFSD("EXIT, result %llu\n", (unsigned long long)result);

        return result;
}

static unsigned ubh_scanc(struct ufs_sb_private_info *uspi,
                          struct ufs_buffer_head *ubh,
                          unsigned begin, unsigned size,
                          unsigned char *table, unsigned char mask)
{
        unsigned rest, offset;
        unsigned char *cp;
        

        offset = begin & ~uspi->s_fmask;
        begin >>= uspi->s_fshift;
        for (;;) {
                if ((offset + size) < uspi->s_fsize)
                        rest = size;
                else
                        rest = uspi->s_fsize - offset;
                size -= rest;
                cp = ubh->bh[begin]->b_data + offset;
                while ((table[*cp++] & mask) == 0 && --rest)
                        ;
                if (rest || !size)
                        break;
                begin++;
                offset = 0;
        }
        return (size + rest);
}

/*
 * Find a block of the specified size in the specified cylinder group.
 * @sp: pointer to super block
 * @ucpi: pointer to cylinder group info
 * @goal: near which block we want find new one
 * @count: specified size
 */
static u64 ufs_bitmap_search(struct super_block *sb,
                             struct ufs_cg_private_info *ucpi,
                             u64 goal, unsigned count)
{
        /*
         * Bit patterns for identifying fragments in the block map
         * used as ((map & mask_arr) == want_arr)
         */
        static const int mask_arr[9] = {
                0x3, 0x7, 0xf, 0x1f, 0x3f, 0x7f, 0xff, 0x1ff, 0x3ff
        };
        static const int want_arr[9] = {
                0x0, 0x2, 0x6, 0xe, 0x1e, 0x3e, 0x7e, 0xfe, 0x1fe
        };
        struct ufs_sb_private_info *uspi = UFS_SB(sb)->s_uspi;
        unsigned start, length, loc;
        unsigned pos, want, blockmap, mask, end;
        u64 result;

        UFSD("ENTER, cg %u, goal %llu, count %u\n", ucpi->c_cgx,
             (unsigned long long)goal, count);

        if (goal)
                start = ufs_dtogd(uspi, goal) >> 3;
        else
                start = ucpi->c_frotor >> 3;
                
        length = ((uspi->s_fpg + 7) >> 3) - start;
        loc = ubh_scanc(uspi, UCPI_UBH(ucpi), ucpi->c_freeoff + start, length,
                (uspi->s_fpb == 8) ? ufs_fragtable_8fpb : ufs_fragtable_other,
                1 << (count - 1 + (uspi->s_fpb & 7))); 
        if (loc == 0) {
                length = start + 1;
                loc = ubh_scanc(uspi, UCPI_UBH(ucpi), ucpi->c_freeoff, length,
                                (uspi->s_fpb == 8) ? ufs_fragtable_8fpb :
                                ufs_fragtable_other,
                                1 << (count - 1 + (uspi->s_fpb & 7)));
                if (loc == 0) {
                        ufs_error(sb, "ufs_bitmap_search",
                                  "bitmap corrupted on cg %u, start %u,"
                                  " length %u, count %u, freeoff %u\n",
                                  ucpi->c_cgx, start, length, count,
                                  ucpi->c_freeoff);
                        return INVBLOCK;
                }
                start = 0;
        }
        result = (start + length - loc) << 3;
        ucpi->c_frotor = result;

        /*
         * found the byte in the map
         */

        for (end = result + 8; result < end; result += uspi->s_fpb) {
                blockmap = ubh_blkmap(UCPI_UBH(ucpi), ucpi->c_freeoff, result);
                blockmap <<= 1;
                mask = mask_arr[count];
                want = want_arr[count];
                for (pos = 0; pos <= uspi->s_fpb - count; pos++) {
                        if ((blockmap & mask) == want) {
                                UFSD("EXIT, result %llu\n",
                                     (unsigned long long)result);
                                return result + pos;
                        }
                        mask <<= 1;
                        want <<= 1;
                }
        }

        ufs_error(sb, "ufs_bitmap_search", "block not in map on cg %u\n",
                  ucpi->c_cgx);
        UFSD("EXIT (FAILED)\n");
        return INVBLOCK;
}

static void ufs_clusteracct(struct super_block * sb,
        struct ufs_cg_private_info * ucpi, unsigned blkno, int cnt)
{
        struct ufs_sb_private_info * uspi;
        int i, start, end, forw, back;
        
        uspi = UFS_SB(sb)->s_uspi;
        if (uspi->s_contigsumsize <= 0)
                return;

        if (cnt > 0)
                ubh_setbit(UCPI_UBH(ucpi), ucpi->c_clusteroff, blkno);
        else
                ubh_clrbit(UCPI_UBH(ucpi), ucpi->c_clusteroff, blkno);

        /*
         * Find the size of the cluster going forward.
         */
        start = blkno + 1;
        end = start + uspi->s_contigsumsize;
        if ( end >= ucpi->c_nclusterblks)
                end = ucpi->c_nclusterblks;
        i = ubh_find_next_zero_bit (UCPI_UBH(ucpi), ucpi->c_clusteroff, end, start);
        if (i > end)
                i = end;
        forw = i - start;
        
        /*
         * Find the size of the cluster going backward.
         */
        start = blkno - 1;
        end = start - uspi->s_contigsumsize;
        if (end < 0 ) 
                end = -1;
        i = ubh_find_last_zero_bit (UCPI_UBH(ucpi), ucpi->c_clusteroff, start, end);
        if ( i < end) 
                i = end;
        back = start - i;
        
        /*
         * Account for old cluster and the possibly new forward and
         * back clusters.
         */
        i = back + forw + 1;
        if (i > uspi->s_contigsumsize)
                i = uspi->s_contigsumsize;
        fs32_add(sb, (__fs32*)ubh_get_addr(UCPI_UBH(ucpi), ucpi->c_clustersumoff + (i << 2)), cnt);
        if (back > 0)
                fs32_sub(sb, (__fs32*)ubh_get_addr(UCPI_UBH(ucpi), ucpi->c_clustersumoff + (back << 2)), cnt);
        if (forw > 0)
                fs32_sub(sb, (__fs32*)ubh_get_addr(UCPI_UBH(ucpi), ucpi->c_clustersumoff + (forw << 2)), cnt);
}


static unsigned char ufs_fragtable_8fpb[] = {
        0x00, 0x01, 0x01, 0x02, 0x01, 0x01, 0x02, 0x04, 0x01, 0x01, 0x01, 0x03, 0x02, 0x03, 0x04, 0x08,
        0x01, 0x01, 0x01, 0x03, 0x01, 0x01, 0x03, 0x05, 0x02, 0x03, 0x03, 0x02, 0x04, 0x05, 0x08, 0x10,
        0x01, 0x01, 0x01, 0x03, 0x01, 0x01, 0x03, 0x05, 0x01, 0x01, 0x01, 0x03, 0x03, 0x03, 0x05, 0x09,
        0x02, 0x03, 0x03, 0x02, 0x03, 0x03, 0x02, 0x06, 0x04, 0x05, 0x05, 0x06, 0x08, 0x09, 0x10, 0x20,
        0x01, 0x01, 0x01, 0x03, 0x01, 0x01, 0x03, 0x05, 0x01, 0x01, 0x01, 0x03, 0x03, 0x03, 0x05, 0x09, 
        0x01, 0x01, 0x01, 0x03, 0x01, 0x01, 0x03, 0x05, 0x03, 0x03, 0x03, 0x03, 0x05, 0x05, 0x09, 0x11,
        0x02, 0x03, 0x03, 0x02, 0x03, 0x03, 0x02, 0x06, 0x03, 0x03, 0x03, 0x03, 0x02, 0x03, 0x06, 0x0A,
        0x04, 0x05, 0x05, 0x06, 0x05, 0x05, 0x06, 0x04, 0x08, 0x09, 0x09, 0x0A, 0x10, 0x11, 0x20, 0x40,
        0x01, 0x01, 0x01, 0x03, 0x01, 0x01, 0x03, 0x05, 0x01, 0x01, 0x01, 0x03, 0x03, 0x03, 0x05, 0x09,
        0x01, 0x01, 0x01, 0x03, 0x01, 0x01, 0x03, 0x05, 0x03, 0x03, 0x03, 0x03, 0x05, 0x05, 0x09, 0x11,
        0x01, 0x01, 0x01, 0x03, 0x01, 0x01, 0x03, 0x05, 0x01, 0x01, 0x01, 0x03, 0x03, 0x03, 0x05, 0x09,
        0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x07, 0x05, 0x05, 0x05, 0x07, 0x09, 0x09, 0x11, 0x21,
        0x02, 0x03, 0x03, 0x02, 0x03, 0x03, 0x02, 0x06, 0x03, 0x03, 0x03, 0x03, 0x02, 0x03, 0x06, 0x0A,
        0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x07, 0x02, 0x03, 0x03, 0x02, 0x06, 0x07, 0x0A, 0x12,
        0x04, 0x05, 0x05, 0x06, 0x05, 0x05, 0x06, 0x04, 0x05, 0x05, 0x05, 0x07, 0x06, 0x07, 0x04, 0x0C,
        0x08, 0x09, 0x09, 0x0A, 0x09, 0x09, 0x0A, 0x0C, 0x10, 0x11, 0x11, 0x12, 0x20, 0x21, 0x40, 0x80,
};

static unsigned char ufs_fragtable_other[] = {
        0x00, 0x16, 0x16, 0x2A, 0x16, 0x16, 0x26, 0x4E, 0x16, 0x16, 0x16, 0x3E, 0x2A, 0x3E, 0x4E, 0x8A,
        0x16, 0x16, 0x16, 0x3E, 0x16, 0x16, 0x36, 0x5E, 0x16, 0x16, 0x16, 0x3E, 0x3E, 0x3E, 0x5E, 0x9E,
        0x16, 0x16, 0x16, 0x3E, 0x16, 0x16, 0x36, 0x5E, 0x16, 0x16, 0x16, 0x3E, 0x3E, 0x3E, 0x5E, 0x9E,
        0x2A, 0x3E, 0x3E, 0x2A, 0x3E, 0x3E, 0x2E, 0x6E, 0x3E, 0x3E, 0x3E, 0x3E, 0x2A, 0x3E, 0x6E, 0xAA,
        0x16, 0x16, 0x16, 0x3E, 0x16, 0x16, 0x36, 0x5E, 0x16, 0x16, 0x16, 0x3E, 0x3E, 0x3E, 0x5E, 0x9E,
        0x16, 0x16, 0x16, 0x3E, 0x16, 0x16, 0x36, 0x5E, 0x16, 0x16, 0x16, 0x3E, 0x3E, 0x3E, 0x5E, 0x9E,
        0x26, 0x36, 0x36, 0x2E, 0x36, 0x36, 0x26, 0x6E, 0x36, 0x36, 0x36, 0x3E, 0x2E, 0x3E, 0x6E, 0xAE,
        0x4E, 0x5E, 0x5E, 0x6E, 0x5E, 0x5E, 0x6E, 0x4E, 0x5E, 0x5E, 0x5E, 0x7E, 0x6E, 0x7E, 0x4E, 0xCE,
        0x16, 0x16, 0x16, 0x3E, 0x16, 0x16, 0x36, 0x5E, 0x16, 0x16, 0x16, 0x3E, 0x3E, 0x3E, 0x5E, 0x9E,
        0x16, 0x16, 0x16, 0x3E, 0x16, 0x16, 0x36, 0x5E, 0x16, 0x16, 0x16, 0x3E, 0x3E, 0x3E, 0x5E, 0x9E,
        0x16, 0x16, 0x16, 0x3E, 0x16, 0x16, 0x36, 0x5E, 0x16, 0x16, 0x16, 0x3E, 0x3E, 0x3E, 0x5E, 0x9E,
        0x3E, 0x3E, 0x3E, 0x3E, 0x3E, 0x3E, 0x3E, 0x7E, 0x3E, 0x3E, 0x3E, 0x3E, 0x3E, 0x3E, 0x7E, 0xBE,
        0x2A, 0x3E, 0x3E, 0x2A, 0x3E, 0x3E, 0x2E, 0x6E, 0x3E, 0x3E, 0x3E, 0x3E, 0x2A, 0x3E, 0x6E, 0xAA,
        0x3E, 0x3E, 0x3E, 0x3E, 0x3E, 0x3E, 0x3E, 0x7E, 0x3E, 0x3E, 0x3E, 0x3E, 0x3E, 0x3E, 0x7E, 0xBE,
        0x4E, 0x5E, 0x5E, 0x6E, 0x5E, 0x5E, 0x6E, 0x4E, 0x5E, 0x5E, 0x5E, 0x7E, 0x6E, 0x7E, 0x4E, 0xCE,
        0x8A, 0x9E, 0x9E, 0xAA, 0x9E, 0x9E, 0xAE, 0xCE, 0x9E, 0x9E, 0x9E, 0xBE, 0xAA, 0xBE, 0xCE, 0x8A,
};