cylinder.c

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/*
 *  linux/fs/ufs/cylinder.c
 *
 * Copyright (C) 1998
 * Daniel Pirkl <[email protected]>
 * Charles University, Faculty of Mathematics and Physics
 *
 *  ext2 - inode (block) bitmap caching inspired
 */

#include <linux/fs.h>
#include <linux/time.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/bitops.h>

#include <asm/byteorder.h>

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

/*
 * Read cylinder group into cache. The memory space for ufs_cg_private_info
 * structure is already allocated during ufs_read_super.
 */
static void ufs_read_cylinder (struct super_block * sb,
    unsigned cgno, unsigned bitmap_nr)
{
    struct ufs_sb_info * sbi = UFS_SB(sb);
    struct ufs_sb_private_info * uspi;
    struct ufs_cg_private_info * ucpi;
    struct ufs_cylinder_group * ucg;
    unsigned i, j;

    UFSD("ENTER, cgno %u, bitmap_nr %u\n", cgno, bitmap_nr);
    uspi = sbi->s_uspi;
    ucpi = sbi->s_ucpi[bitmap_nr];
    ucg = (struct ufs_cylinder_group *)sbi->s_ucg[cgno]->b_data;

    UCPI_UBH(ucpi)->fragment = ufs_cgcmin(cgno);
    UCPI_UBH(ucpi)->count = uspi->s_cgsize >> sb->s_blocksize_bits;
    /*
     * We have already the first fragment of cylinder group block in buffer
     */
    UCPI_UBH(ucpi)->bh[0] = sbi->s_ucg[cgno];
    for (i = 1; i < UCPI_UBH(ucpi)->count; i++)
        if (!(UCPI_UBH(ucpi)->bh[i] = sb_bread(sb, UCPI_UBH(ucpi)->fragment + i)))
            goto failed;
    sbi->s_cgno[bitmap_nr] = cgno;
            
    ucpi->c_cgx = fs32_to_cpu(sb, ucg->cg_cgx);
    ucpi->c_ncyl    = fs16_to_cpu(sb, ucg->cg_ncyl);
    ucpi->c_niblk   = fs16_to_cpu(sb, ucg->cg_niblk);
    ucpi->c_ndblk   = fs32_to_cpu(sb, ucg->cg_ndblk);
    ucpi->c_rotor   = fs32_to_cpu(sb, ucg->cg_rotor);
    ucpi->c_frotor  = fs32_to_cpu(sb, ucg->cg_frotor);
    ucpi->c_irotor  = fs32_to_cpu(sb, ucg->cg_irotor);
    ucpi->c_btotoff = fs32_to_cpu(sb, ucg->cg_btotoff);
    ucpi->c_boff    = fs32_to_cpu(sb, ucg->cg_boff);
    ucpi->c_iusedoff = fs32_to_cpu(sb, ucg->cg_iusedoff);
    ucpi->c_freeoff = fs32_to_cpu(sb, ucg->cg_freeoff);
    ucpi->c_nextfreeoff = fs32_to_cpu(sb, ucg->cg_nextfreeoff);
    ucpi->c_clustersumoff = fs32_to_cpu(sb, ucg->cg_u.cg_44.cg_clustersumoff);
    ucpi->c_clusteroff = fs32_to_cpu(sb, ucg->cg_u.cg_44.cg_clusteroff);
    ucpi->c_nclusterblks = fs32_to_cpu(sb, ucg->cg_u.cg_44.cg_nclusterblks);
    UFSD("EXIT\n");
    return; 
    
failed:
    for (j = 1; j < i; j++)
        brelse (sbi->s_ucg[j]);
    sbi->s_cgno[bitmap_nr] = UFS_CGNO_EMPTY;
    ufs_error (sb, "ufs_read_cylinder", "can't read cylinder group block %u", cgno);
}

/*
 * Remove cylinder group from cache, doesn't release memory
 * allocated for cylinder group (this is done at ufs_put_super only).
 */
void ufs_put_cylinder (struct super_block * sb, unsigned bitmap_nr)
{
    struct ufs_sb_info * sbi = UFS_SB(sb);
    struct ufs_sb_private_info * uspi; 
    struct ufs_cg_private_info * ucpi;
    struct ufs_cylinder_group * ucg;
    unsigned i;

    UFSD("ENTER, bitmap_nr %u\n", bitmap_nr);

    uspi = sbi->s_uspi;
    if (sbi->s_cgno[bitmap_nr] == UFS_CGNO_EMPTY) {
        UFSD("EXIT\n");
        return;
    }
    ucpi = sbi->s_ucpi[bitmap_nr];
    ucg = ubh_get_ucg(UCPI_UBH(ucpi));

    if (uspi->s_ncg > UFS_MAX_GROUP_LOADED && bitmap_nr >= sbi->s_cg_loaded) {
        ufs_panic (sb, "ufs_put_cylinder", "internal error");
        return;
    }
    /*
     * rotor is not so important data, so we put it to disk 
     * at the end of working with cylinder
     */
    ucg->cg_rotor = cpu_to_fs32(sb, ucpi->c_rotor);
    ucg->cg_frotor = cpu_to_fs32(sb, ucpi->c_frotor);
    ucg->cg_irotor = cpu_to_fs32(sb, ucpi->c_irotor);
    ubh_mark_buffer_dirty (UCPI_UBH(ucpi));
    for (i = 1; i < UCPI_UBH(ucpi)->count; i++) {
        brelse (UCPI_UBH(ucpi)->bh[i]);
    }

    sbi->s_cgno[bitmap_nr] = UFS_CGNO_EMPTY;
    UFSD("EXIT\n");
}

/*
 * Find cylinder group in cache and return it as pointer.
 * If cylinder group is not in cache, we will load it from disk.
 *
 * The cache is managed by LRU algorithm. 
 */
struct ufs_cg_private_info * ufs_load_cylinder (
    struct super_block * sb, unsigned cgno)
{
    struct ufs_sb_info * sbi = UFS_SB(sb);
    struct ufs_sb_private_info * uspi;
    struct ufs_cg_private_info * ucpi;
    unsigned cg, i, j;

    UFSD("ENTER, cgno %u\n", cgno);

    uspi = sbi->s_uspi;
    if (cgno >= uspi->s_ncg) {
        ufs_panic (sb, "ufs_load_cylinder", "internal error, high number of cg");
        return NULL;
    }
    /*
     * Cylinder group number cg it in cache and it was last used
     */
    if (sbi->s_cgno[0] == cgno) {
        UFSD("EXIT\n");
        return sbi->s_ucpi[0];
    }
    /*
     * Number of cylinder groups is not higher than UFS_MAX_GROUP_LOADED
     */
    if (uspi->s_ncg <= UFS_MAX_GROUP_LOADED) {
        if (sbi->s_cgno[cgno] != UFS_CGNO_EMPTY) {
            if (sbi->s_cgno[cgno] != cgno) {
                ufs_panic (sb, "ufs_load_cylinder", "internal error, wrong number of cg in cache");
                UFSD("EXIT (FAILED)\n");
                return NULL;
            }
            else {
                UFSD("EXIT\n");
                return sbi->s_ucpi[cgno];
            }
        } else {
            ufs_read_cylinder (sb, cgno, cgno);
            UFSD("EXIT\n");
            return sbi->s_ucpi[cgno];
        }
    }
    /*
     * Cylinder group number cg is in cache but it was not last used, 
     * we will move to the first position
     */
    for (i = 0; i < sbi->s_cg_loaded && sbi->s_cgno[i] != cgno; i++);
    if (i < sbi->s_cg_loaded && sbi->s_cgno[i] == cgno) {
        cg = sbi->s_cgno[i];
        ucpi = sbi->s_ucpi[i];
        for (j = i; j > 0; j--) {
            sbi->s_cgno[j] = sbi->s_cgno[j-1];
            sbi->s_ucpi[j] = sbi->s_ucpi[j-1];
        }
        sbi->s_cgno[0] = cg;
        sbi->s_ucpi[0] = ucpi;
    /*
     * Cylinder group number cg is not in cache, we will read it from disk
     * and put it to the first position
     */
    } else {
        if (sbi->s_cg_loaded < UFS_MAX_GROUP_LOADED)
            sbi->s_cg_loaded++;
        else
            ufs_put_cylinder (sb, UFS_MAX_GROUP_LOADED-1);
        ucpi = sbi->s_ucpi[sbi->s_cg_loaded - 1];
        for (j = sbi->s_cg_loaded - 1; j > 0; j--) {
            sbi->s_cgno[j] = sbi->s_cgno[j-1];
            sbi->s_ucpi[j] = sbi->s_ucpi[j-1];
        }
        sbi->s_ucpi[0] = ucpi;
        ufs_read_cylinder (sb, cgno, 0);
    }
    UFSD("EXIT\n");
    return sbi->s_ucpi[0];
}