Miscellanious performance adjustments to the kernel

[dragonfly.git] / sys / vfs / gnu / ext2fs / ext2_linux_balloc.c

/*
 *  modified for Lites 1.1
 *
 *  Aug 1995, Godmar Back (gback@cs.utah.edu)
 *  University of Utah, Department of Computer Science
 *
 * $FreeBSD: src/sys/gnu/ext2fs/ext2_linux_balloc.c,v 1.11.2.3 2001/08/14 18:03:19 gallatin Exp $
 * $DragonFly: src/sys/vfs/gnu/ext2fs/ext2_linux_balloc.c,v 1.11 2007/09/23 04:09:55 yanyh Exp $
 */
/*
 *  linux/fs/ext2/balloc.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  Enhanced block allocation by Stephen Tweedie (sct@dcs.ed.ac.uk), 1993
 */

/*
 * The free blocks are managed by bitmaps.  A file system contains several
 * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
 * block for inodes, N blocks for the inode table and data blocks.
 *
 * The file system contains group descriptors which are located after the
 * super block.  Each descriptor contains the number of the bitmap block and
 * the free blocks count in the block.  The descriptors are loaded in memory
 * when a file system is mounted (see ext2_read_super).
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/proc.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/buf2.h>
#include <sys/thread2.h>

#include "quota.h"
#include "dinode.h"
#include "inode.h"
#include "ext2mount.h"
#include "ext2_extern.h"
#include "ext2_fs.h"
#include "ext2_fs_sb.h"
#include "fs.h"

#ifdef __i386__
#include "i386-bitops.h"
#else
#include "ext2_bitops.h"
#endif

#define in_range(b, first, len)         ((b) >= (first) && (b) <= (first) + (len) - 1)

/* got rid of get_group_desc since it can already be found in 
 * ext2_linux_ialloc.c
 */

static void
read_block_bitmap(struct mount *mp, unsigned int block_group,
                  unsigned long bitmap_nr)
{
        struct ext2_sb_info *sb = VFSTOEXT2(mp)->um_e2fs;
        struct ext2_group_desc * gdp;
        struct buffer_head * bh;
        int    error;
        
        gdp = get_group_desc (mp, block_group, NULL);
        error = bread(VFSTOEXT2(mp)->um_devvp, 
                      fsbtodoff(sb, gdp->bg_block_bitmap),
                      sb->s_blocksize, &bh);
        if (error) {
                panic ( "read_block_bitmap: "
                            "Cannot read block bitmap - "
                            "block_group = %d, block_bitmap = %lu",
                            block_group, (unsigned long) gdp->bg_block_bitmap);
        }
        sb->s_block_bitmap_number[bitmap_nr] = block_group;
        sb->s_block_bitmap[bitmap_nr] = bh;
        LCK_BUF(bh)
}

/*
 * load_block_bitmap loads the block bitmap for a blocks group
 *
 * It maintains a cache for the last bitmaps loaded.  This cache is managed
 * with a LRU algorithm.
 *
 * Notes:
 * 1/ There is one cache per mounted file system.
 * 2/ If the file system contains less than EXT2_MAX_GROUP_LOADED groups,
 *    this function reads the bitmap without maintaining a LRU cache.
 */
static int
load__block_bitmap(struct mount *mp, unsigned int block_group)
{
        int i, j;
        struct ext2_sb_info *sb = VFSTOEXT2(mp)->um_e2fs;
        unsigned long block_bitmap_number;
        struct buffer_head * block_bitmap;

        if (block_group >= sb->s_groups_count)
                panic ( "load_block_bitmap: "
                            "block_group >= groups_count - "
                            "block_group = %d, groups_count = %lu",
                            block_group, sb->s_groups_count);

        if (sb->s_groups_count <= EXT2_MAX_GROUP_LOADED) {
                if (sb->s_block_bitmap[block_group]) {
                        if (sb->s_block_bitmap_number[block_group] !=
                            block_group)
                                panic ( "load_block_bitmap: "
                                            "block_group != block_bitmap_number");
                        else
                                return block_group;
                } else {
                        read_block_bitmap (mp, block_group, block_group);
                        return block_group;
                }
        }

        for (i = 0; i < sb->s_loaded_block_bitmaps &&
                    sb->s_block_bitmap_number[i] != block_group; i++)
                ;
        if (i < sb->s_loaded_block_bitmaps &&
            sb->s_block_bitmap_number[i] == block_group) {
                block_bitmap_number = sb->s_block_bitmap_number[i];
                block_bitmap = sb->s_block_bitmap[i];
                for (j = i; j > 0; j--) {
                        sb->s_block_bitmap_number[j] =
                                sb->s_block_bitmap_number[j - 1];
                        sb->s_block_bitmap[j] =
                                sb->s_block_bitmap[j - 1];
                }
                sb->s_block_bitmap_number[0] = block_bitmap_number;
                sb->s_block_bitmap[0] = block_bitmap;
        } else {
                if (sb->s_loaded_block_bitmaps < EXT2_MAX_GROUP_LOADED)
                        sb->s_loaded_block_bitmaps++;
                else
                        ULCK_BUF(sb->s_block_bitmap[EXT2_MAX_GROUP_LOADED - 1])

                for (j = sb->s_loaded_block_bitmaps - 1; j > 0;  j--) {
                        sb->s_block_bitmap_number[j] =
                                sb->s_block_bitmap_number[j - 1];
                        sb->s_block_bitmap[j] =
                                sb->s_block_bitmap[j - 1];
                }
                read_block_bitmap (mp, block_group, 0);
        }
        return 0;
}

static __inline int
load_block_bitmap(struct mount * mp, unsigned int block_group)
{
        struct ext2_sb_info *sb = VFSTOEXT2(mp)->um_e2fs;
        if (sb->s_loaded_block_bitmaps > 0 &&
            sb->s_block_bitmap_number[0] == block_group)
                return 0;
        
        if (sb->s_groups_count <= EXT2_MAX_GROUP_LOADED && 
            sb->s_block_bitmap_number[block_group] == block_group &&
            sb->s_block_bitmap[block_group]) 
                return block_group;

        return load__block_bitmap (mp, block_group);
}

void
ext2_free_blocks(struct mount * mp, unsigned long block,
                 unsigned long count)
{
        struct ext2_sb_info *sb = VFSTOEXT2(mp)->um_e2fs;
        struct buffer_head * bh;
        struct buffer_head * bh2;
        unsigned long block_group;
        unsigned long bit;
        unsigned long i;
        int bitmap_nr;
        struct ext2_group_desc * gdp;
        struct ext2_super_block * es = sb->s_es;

        if (!sb) {
                kprintf ("ext2_free_blocks: nonexistent device");
                return;
        }
        lock_super (VFSTOEXT2(mp)->um_devvp);
        if (block < es->s_first_data_block || 
            (block + count) > es->s_blocks_count) {
                kprintf ( "ext2_free_blocks: "
                            "Freeing blocks not in datazone - "
                            "block = %lu, count = %lu", block, count);
                unlock_super (VFSTOEXT2(mp)->um_devvp);
                return;
        }

        ext2_debug ("freeing blocks %lu to %lu\n", block, block+count-1);

        block_group = (block - es->s_first_data_block) /
                      EXT2_BLOCKS_PER_GROUP(sb);
        bit = (block - es->s_first_data_block) % EXT2_BLOCKS_PER_GROUP(sb);
        if (bit + count > EXT2_BLOCKS_PER_GROUP(sb))
                panic ( "ext2_free_blocks: "
                            "Freeing blocks across group boundary - "
                            "Block = %lu, count = %lu",
                            block, count);
        bitmap_nr = load_block_bitmap (mp, block_group);
        bh = sb->s_block_bitmap[bitmap_nr];
        gdp = get_group_desc (mp, block_group, &bh2);

        if (/* test_opt (sb, CHECK_STRICT) &&   assume always strict ! */
            (in_range (gdp->bg_block_bitmap, block, count) ||
             in_range (gdp->bg_inode_bitmap, block, count) ||
             in_range (block, gdp->bg_inode_table,
                       sb->s_itb_per_group) ||
             in_range (block + count - 1, gdp->bg_inode_table,
                       sb->s_itb_per_group)))
                panic ( "ext2_free_blocks: "
                            "Freeing blocks in system zones - "
                            "Block = %lu, count = %lu",
                            block, count);

        for (i = 0; i < count; i++) {
                if (!clear_bit (bit + i, bh->b_data))
                        kprintf ("ext2_free_blocks: "
                                      "bit already cleared for block %lu", 
                                      block);
                else {
                        gdp->bg_free_blocks_count++;
                        es->s_free_blocks_count++;
                }
        }

        mark_buffer_dirty(bh2);
        mark_buffer_dirty(bh);
/****
        if (sb->s_flags & MS_SYNCHRONOUS) {
                ll_rw_block (WRITE, 1, &bh);
                wait_on_buffer (bh);
        }
****/
        sb->s_dirt = 1;
        unlock_super (VFSTOEXT2(mp)->um_devvp);
        return;
}

/*
 * ext2_new_block uses a goal block to assist allocation.  If the goal is
 * free, or there is a free block within 32 blocks of the goal, that block
 * is allocated.  Otherwise a forward search is made for a free block; within 
 * each block group the search first looks for an entire free byte in the block
 * bitmap, and then for any free bit if that fails.
 */
int
ext2_new_block(struct mount * mp, unsigned long goal,
               u_int32_t * prealloc_count,
               u_int32_t * prealloc_block)
{
        struct ext2_sb_info *sb = VFSTOEXT2(mp)->um_e2fs;
        struct buffer_head * bh;
        struct buffer_head * bh2;
        char * p, * r;
        int i, j, k, tmp;
        int bitmap_nr;
        struct ext2_group_desc * gdp;
        struct ext2_super_block * es = sb->s_es;

#ifdef EXT2FS_DEBUG
        static int goal_hits = 0, goal_attempts = 0;
#endif
        if (!sb) {
                kprintf ("ext2_new_block: nonexistent device");
                return 0;
        }
        lock_super (VFSTOEXT2(mp)->um_devvp);

        ext2_debug ("goal=%lu.\n", goal);

repeat:
        /*
         * First, test whether the goal block is free.
         */
        if (goal < es->s_first_data_block || goal >= es->s_blocks_count)
                goal = es->s_first_data_block;
        i = (goal - es->s_first_data_block) / EXT2_BLOCKS_PER_GROUP(sb);
        gdp = get_group_desc (mp, i, &bh2);
        if (gdp->bg_free_blocks_count > 0) {
                j = ((goal - es->s_first_data_block) % EXT2_BLOCKS_PER_GROUP(sb));
#ifdef EXT2FS_DEBUG
                if (j)
                        goal_attempts++;
#endif
                bitmap_nr = load_block_bitmap (mp, i);
                bh = sb->s_block_bitmap[bitmap_nr];

                ext2_debug ("goal is at %d:%d.\n", i, j); 

                if (!test_bit(j, bh->b_data)) {
#ifdef EXT2FS_DEBUG
                        goal_hits++;
                        ext2_debug ("goal bit allocated.\n");
#endif
                        goto got_block;
                }
                if (j) {
                        /*
                         * The goal was occupied; search forward for a free 
                         * block within the next XX blocks.
                         *
                         * end_goal is more or less random, but it has to be
                         * less than EXT2_BLOCKS_PER_GROUP. Aligning up to the
                         * next 64-bit boundary is simple..
                         */
                        int end_goal = (j + 63) & ~63;
                        j = find_next_zero_bit(bh->b_data, end_goal, j);
                        if (j < end_goal)
                                goto got_block;
                }
        
                ext2_debug ("Bit not found near goal\n");

                /*
                 * There has been no free block found in the near vicinity
                 * of the goal: do a search forward through the block groups,
                 * searching in each group first for an entire free byte in
                 * the bitmap and then for any free bit.
                 * 
                 * Search first in the remainder of the current group; then,
                 * cyclicly search through the rest of the groups.
                 */
                p = ((char *) bh->b_data) + (j >> 3);
                r = memscan(p, 0, (EXT2_BLOCKS_PER_GROUP(sb) - j + 7) >> 3);
                k = (r - ((char *) bh->b_data)) << 3;
                if (k < EXT2_BLOCKS_PER_GROUP(sb)) {
                        j = k;
                        goto search_back;
                }
                k = find_next_zero_bit ((unsigned long *) bh->b_data, 
                                        EXT2_BLOCKS_PER_GROUP(sb),
                                        j);
                if (k < EXT2_BLOCKS_PER_GROUP(sb)) {
                        j = k;
                        goto got_block;
                }
        }

        ext2_debug ("Bit not found in block group %d.\n", i); 

        /*
         * Now search the rest of the groups.  We assume that 
         * i and gdp correctly point to the last group visited.
         */
        for (k = 0; k < sb->s_groups_count; k++) {
                i++;
                if (i >= sb->s_groups_count)
                        i = 0;
                gdp = get_group_desc (mp, i, &bh2);
                if (gdp->bg_free_blocks_count > 0)
                        break;
        }
        if (k >= sb->s_groups_count) {
                unlock_super (VFSTOEXT2(mp)->um_devvp);
                return 0;
        }
        bitmap_nr = load_block_bitmap (mp, i);
        bh = sb->s_block_bitmap[bitmap_nr];
        r = memscan(bh->b_data, 0, EXT2_BLOCKS_PER_GROUP(sb) >> 3);
        j = (r - bh->b_data) << 3;

        if (j < EXT2_BLOCKS_PER_GROUP(sb))
                goto search_back;
        else
                j = find_first_zero_bit ((unsigned long *) bh->b_data,
                                         EXT2_BLOCKS_PER_GROUP(sb));
        if (j >= EXT2_BLOCKS_PER_GROUP(sb)) {
                kprintf ( "ext2_new_block: "
                         "Free blocks count corrupted for block group %d", i);
                unlock_super (VFSTOEXT2(mp)->um_devvp);
                return 0;
        }

search_back:
        /* 
         * We have succeeded in finding a free byte in the block
         * bitmap.  Now search backwards up to 7 bits to find the
         * start of this group of free blocks.
         */
        for (k = 0; k < 7 && j > 0 && !test_bit (j - 1, bh->b_data); k++, j--);
        
got_block:

        ext2_debug ("using block group %d(%d)\n", i, gdp->bg_free_blocks_count);

        tmp = j + i * EXT2_BLOCKS_PER_GROUP(sb) + es->s_first_data_block;

        if (/* test_opt (sb, CHECK_STRICT) && we are always strict. */
            (tmp == gdp->bg_block_bitmap ||
             tmp == gdp->bg_inode_bitmap ||
             in_range (tmp, gdp->bg_inode_table, sb->s_itb_per_group)))
                panic ( "ext2_new_block: "
                            "Allocating block in system zone - "
                            "%dth block = %u in group %u", j, tmp, i);

        if (set_bit (j, bh->b_data)) {
                kprintf ( "ext2_new_block: "
                         "bit already set for block %d", j);
                goto repeat;
        }

        ext2_debug ("found bit %d\n", j);

        /*
         * Do block preallocation now if required.
         */
#ifdef EXT2_PREALLOCATE
        if (prealloc_block) {
                *prealloc_count = 0;
                *prealloc_block = tmp + 1;
                for (k = 1;
                     k < 8 && (j + k) < EXT2_BLOCKS_PER_GROUP(sb); k++) {
                        if (set_bit (j + k, bh->b_data))
                                break;
                        (*prealloc_count)++;
                }       
                gdp->bg_free_blocks_count -= *prealloc_count;
                es->s_free_blocks_count -= *prealloc_count;
                ext2_debug ("Preallocated a further %lu bits.\n",
                            *prealloc_count); 
        }
#endif

        j = tmp;

        mark_buffer_dirty(bh);
/****
        if (sb->s_flags & MS_SYNCHRONOUS) {
                ll_rw_block (WRITE, 1, &bh);
                wait_on_buffer (bh);
        }
****/
        if (j >= es->s_blocks_count) {
                kprintf ( "ext2_new_block: "
                            "block >= blocks count - "
                            "block_group = %d, block=%d", i, j);
                unlock_super (VFSTOEXT2(mp)->um_devvp);
                return 0;
        }

        ext2_debug ("allocating block %d. "
                    "Goal hits %d of %d.\n", j, goal_hits, goal_attempts);

        gdp->bg_free_blocks_count--;
        mark_buffer_dirty(bh2);
        es->s_free_blocks_count--;
        sb->s_dirt = 1;
        unlock_super (VFSTOEXT2(mp)->um_devvp);
        return j;
}

#ifdef unused
static unsigned long
ext2_count_free_blocks(struct mount * mp)
{
        struct ext2_sb_info *sb = VFSTOEXT2(mp)->um_e2fs;
#ifdef EXT2FS_DEBUG
        struct ext2_super_block * es;
        unsigned long desc_count, bitmap_count, x;
        int bitmap_nr;
        struct ext2_group_desc * gdp;
        int i;
        
        lock_super (VFSTOEXT2(mp)->um_devvp);
        es = sb->s_es;
        desc_count = 0;
        bitmap_count = 0;
        gdp = NULL;
        for (i = 0; i < sb->s_groups_count; i++) {
                gdp = get_group_desc (mp, i, NULL);
                desc_count += gdp->bg_free_blocks_count;
                bitmap_nr = load_block_bitmap (mp, i);
                x = ext2_count_free (sb->s_block_bitmap[bitmap_nr],
                                     sb->s_blocksize);
                ext2_debug ("group %d: stored = %d, counted = %lu\n",
                        i, gdp->bg_free_blocks_count, x);
                bitmap_count += x;
        }
        ext2_debug( "stored = %lu, computed = %lu, %lu\n",
               es->s_free_blocks_count, desc_count, bitmap_count);
        unlock_super (VFSTOEXT2(mp)->um_devvp);
        return bitmap_count;
#else
        return sb->s_es->s_free_blocks_count;
#endif
}
#endif /* unused */

static __inline int
block_in_use (unsigned long block, struct ext2_sb_info *sb,
              unsigned char * map)
{
        return test_bit ((block - sb->s_es->s_first_data_block) %
                         EXT2_BLOCKS_PER_GROUP(sb), map);
}

static int
test_root(int a, int b)
{
        if (a == 0)
                return 1;
        while (1) {
                if (a == 1)
                        return 1;
                if (a % b)
                        return 0;
                a = a / b;
        }
}

int
ext2_group_sparse(int group)
{
        return (test_root(group, 3) || test_root(group, 5) ||
                test_root(group, 7));
}

#ifdef unused
static void
ext2_check_blocks_bitmap(struct mount * mp)
{
        struct ext2_sb_info *sb = VFSTOEXT2(mp)->um_e2fs;
        struct buffer_head * bh;
        struct ext2_super_block * es;
        unsigned long desc_count, bitmap_count, x;
        unsigned long desc_blocks;
        int bitmap_nr;
        struct ext2_group_desc * gdp;
        int i, j;

        lock_super (VFSTOEXT2(mp)->um_devvp);
        es = sb->s_es;
        desc_count = 0;
        bitmap_count = 0;
        gdp = NULL;
        desc_blocks = (sb->s_groups_count + EXT2_DESC_PER_BLOCK(sb) - 1) /
                      EXT2_DESC_PER_BLOCK(sb);
        for (i = 0; i < sb->s_groups_count; i++) {
                gdp = get_group_desc (mp, i, NULL);
                desc_count += gdp->bg_free_blocks_count;
                bitmap_nr = load_block_bitmap (mp, i);
                bh = sb->s_block_bitmap[bitmap_nr];

                if (!(es->s_feature_ro_compat &
                     EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER) ||
                    ext2_group_sparse(i)) {
                        if (!test_bit (0, bh->b_data))
                                kprintf ("ext2_check_blocks_bitmap: "
                                            "Superblock in group %d "
                                            "is marked free", i);

                        for (j = 0; j < desc_blocks; j++)
                                if (!test_bit (j + 1, bh->b_data))
                                        kprintf ("ext2_check_blocks_bitmap: "
                                            "Descriptor block #%d in group "
                                            "%d is marked free", j, i);
                }

                if (!block_in_use (gdp->bg_block_bitmap, sb, bh->b_data))
                        kprintf ("ext2_check_blocks_bitmap: "
                                    "Block bitmap for group %d is marked free",
                                    i);

                if (!block_in_use (gdp->bg_inode_bitmap, sb, bh->b_data))
                        kprintf ("ext2_check_blocks_bitmap: "
                                    "Inode bitmap for group %d is marked free",
                                    i);

                for (j = 0; j < sb->s_itb_per_group; j++)
                        if (!block_in_use (gdp->bg_inode_table + j, sb, bh->b_data))
                                kprintf ("ext2_check_blocks_bitmap: "
                                            "Block #%d of the inode table in "
                                            "group %d is marked free", j, i);

                x = ext2_count_free (bh, sb->s_blocksize);
                if (gdp->bg_free_blocks_count != x)
                        kprintf ("ext2_check_blocks_bitmap: "
                                    "Wrong free blocks count for group %d, "
                                    "stored = %d, counted = %lu", i,
                                    gdp->bg_free_blocks_count, x);
                bitmap_count += x;
        }
        if (es->s_free_blocks_count != bitmap_count)
                kprintf ("ext2_check_blocks_bitmap: "
                            "Wrong free blocks count in super block, "
                            "stored = %lu, counted = %lu",
                            (unsigned long) es->s_free_blocks_count, bitmap_count);
        unlock_super (VFSTOEXT2(mp)->um_devvp);
}
#endif /* unused */

/*
 *  this function is taken from 
 *  linux/fs/ext2/bitmap.c
 */

static int nibblemap[] = {4, 3, 3, 2, 3, 2, 2, 1, 3, 2, 2, 1, 2, 1, 1, 0};

unsigned long ext2_count_free (struct buffer_head * map, unsigned int numchars)
{
        unsigned int i;
        unsigned long sum = 0;

        if (!map)
                return (0);
        for (i = 0; i < numchars; i++)
                sum += nibblemap[map->b_data[i] & 0xf] +
                        nibblemap[(map->b_data[i] >> 4) & 0xf];
        return (sum);
}