656 lines
18 KiB
C
656 lines
18 KiB
C
/*
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* linux/fs/ext2/balloc.c
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*
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* Copyright (C) 1992, 1993, 1994 Remy Card (card@masi.ibp.fr)
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* Laboratoire MASI - Institut Blaise Pascal
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* Universite Pierre et Marie Curie (Paris VI)
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*
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* Enhanced block allocation by Stephen Tweedie (sct@dcs.ed.ac.uk), 1993
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*/
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/*
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* balloc.c contains the blocks allocation and deallocation routines
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*/
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/*
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* The free blocks are managed by bitmaps. A file system contains several
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* blocks groups. Each group contains 1 bitmap block for blocks, 1 bitmap
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* block for inodes, N blocks for the inode table and data blocks.
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*
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* The file system contains group descriptors which are located after the
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* super block. Each descriptor contains the number of the bitmap block and
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* the free blocks count in the block. The descriptors are loaded in memory
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* when a file system is mounted (see ext2_read_super).
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*/
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#include <linux/fs.h>
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#include <linux/ext2_fs.h>
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#include <linux/stat.h>
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#include <linux/sched.h>
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#include <linux/string.h>
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#include <linux/locks.h>
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#include <asm/bitops.h>
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#define clear_block(addr,size) \
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__asm__("cld\n\t" \
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"rep\n\t" \
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"stosl" \
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: \
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:"a" (0), "c" (size / 4), "D" ((long) (addr)) \
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:"cx", "di")
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#define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1)
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static inline int find_first_zero_bit (unsigned long * addr, unsigned size)
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{
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int res;
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if (!size)
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return 0;
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__asm__("
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cld
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movl $-1,%%eax
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repe; scasl
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je 1f
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subl $4,%%edi
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movl (%%edi),%%eax
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notl %%eax
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bsfl %%eax,%%edx
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jmp 2f
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1: xorl %%edx,%%edx
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2: subl %%ebx,%%edi
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shll $3,%%edi
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addl %%edi,%%edx"
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:"=d" (res)
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:"c" ((size + 31) >> 5), "D" (addr), "b" (addr)
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:"ax", "bx", "cx", "di");
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return res;
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}
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static inline int find_next_zero_bit (unsigned long * addr, int size,
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int offset)
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{
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unsigned long * p = ((unsigned long *) addr) + (offset >> 5);
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int set = 0, bit = offset & 31, res;
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if (bit) {
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/*
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* Look for zero in first byte
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*/
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__asm__("
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bsfl %1,%0
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jne 1f
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movl $32, %0
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1: "
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: "=r" (set)
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: "r" (~(*p >> bit)));
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if (set < (32 - bit))
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return set + offset;
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set = 32 - bit;
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p++;
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}
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/*
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* No zero yet, search remaining full bytes for a zero
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*/
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res = find_first_zero_bit (p, size - 32 * (p - addr));
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return (offset + set + res);
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}
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static inline char * find_first_zero_byte (char * addr, int size)
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{
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char *res;
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if (!size)
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return 0;
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__asm__("
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cld
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mov $0,%%eax
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repnz; scasb
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jnz 1f
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dec %%edi
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1: "
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: "=D" (res)
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: "0" (addr), "c" (size)
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: "ax");
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return res;
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}
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static struct ext2_group_desc * get_group_desc (struct super_block * sb,
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unsigned int block_group,
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struct buffer_head ** bh)
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{
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unsigned long group_desc;
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unsigned long desc;
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struct ext2_group_desc * gdp;
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if (block_group >= sb->u.ext2_sb.s_groups_count)
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ext2_panic (sb, "get_group_desc",
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"block_group >= groups_count\n"
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"block_group = %d, groups_count = %lu",
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block_group, sb->u.ext2_sb.s_groups_count);
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group_desc = block_group / EXT2_DESC_PER_BLOCK(sb);
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desc = block_group % EXT2_DESC_PER_BLOCK(sb);
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if (!sb->u.ext2_sb.s_group_desc[group_desc])
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ext2_panic (sb, "get_group_desc",
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"Group descriptor not loaded\n"
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"block_group = %d, group_desc = %lu, desc = %lu",
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block_group, group_desc, desc);
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gdp = (struct ext2_group_desc *)
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sb->u.ext2_sb.s_group_desc[group_desc]->b_data;
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if (bh)
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*bh = sb->u.ext2_sb.s_group_desc[group_desc];
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return gdp + desc;
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}
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static void read_block_bitmap (struct super_block * sb,
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unsigned int block_group,
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unsigned long bitmap_nr)
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{
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struct ext2_group_desc * gdp;
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struct buffer_head * bh;
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gdp = get_group_desc (sb, block_group, NULL);
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bh = bread (sb->s_dev, gdp->bg_block_bitmap, sb->s_blocksize);
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if (!bh)
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ext2_panic (sb, "read_block_bitmap",
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"Cannot read block bitmap\n"
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"block_group = %d, block_bitmap = %lu",
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block_group, gdp->bg_block_bitmap);
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sb->u.ext2_sb.s_block_bitmap_number[bitmap_nr] = block_group;
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sb->u.ext2_sb.s_block_bitmap[bitmap_nr] = bh;
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}
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/*
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* load_block_bitmap loads the block bitmap for a blocks group
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*
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* It maintains a cache for the last bitmaps loaded. This cache is managed
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* with a LRU algorithm.
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*
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* Notes:
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* 1/ There is one cache per mounted file system.
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* 2/ If the file system contains less than EXT2_MAX_GROUP_LOADED groups,
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* this function reads the bitmap without maintaining a LRU cache.
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*/
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static int load__block_bitmap (struct super_block * sb,
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unsigned int block_group)
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{
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int i, j;
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unsigned long block_bitmap_number;
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struct buffer_head * block_bitmap;
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if (block_group >= sb->u.ext2_sb.s_groups_count)
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ext2_panic (sb, "load_block_bitmap",
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"block_group >= groups_count\n"
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"block_group = %d, groups_count = %lu",
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block_group, sb->u.ext2_sb.s_groups_count);
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if (sb->u.ext2_sb.s_groups_count <= EXT2_MAX_GROUP_LOADED) {
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if (sb->u.ext2_sb.s_block_bitmap[block_group]) {
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if (sb->u.ext2_sb.s_block_bitmap_number[block_group] !=
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block_group)
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ext2_panic (sb, "load_block_bitmap",
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"block_group != block_bitmap_number");
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else
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return block_group;
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} else {
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read_block_bitmap (sb, block_group, block_group);
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return block_group;
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}
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}
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for (i = 0; i < sb->u.ext2_sb.s_loaded_block_bitmaps &&
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sb->u.ext2_sb.s_block_bitmap_number[i] != block_group; i++)
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;
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if (i < sb->u.ext2_sb.s_loaded_block_bitmaps &&
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sb->u.ext2_sb.s_block_bitmap_number[i] == block_group) {
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block_bitmap_number = sb->u.ext2_sb.s_block_bitmap_number[i];
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block_bitmap = sb->u.ext2_sb.s_block_bitmap[i];
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for (j = i; j > 0; j--) {
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sb->u.ext2_sb.s_block_bitmap_number[j] =
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sb->u.ext2_sb.s_block_bitmap_number[j - 1];
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sb->u.ext2_sb.s_block_bitmap[j] =
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sb->u.ext2_sb.s_block_bitmap[j - 1];
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}
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sb->u.ext2_sb.s_block_bitmap_number[0] = block_bitmap_number;
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sb->u.ext2_sb.s_block_bitmap[0] = block_bitmap;
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} else {
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if (sb->u.ext2_sb.s_loaded_block_bitmaps < EXT2_MAX_GROUP_LOADED)
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sb->u.ext2_sb.s_loaded_block_bitmaps++;
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else
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brelse (sb->u.ext2_sb.s_block_bitmap[EXT2_MAX_GROUP_LOADED - 1]);
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for (j = sb->u.ext2_sb.s_loaded_block_bitmaps - 1; j > 0; j--) {
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sb->u.ext2_sb.s_block_bitmap_number[j] =
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sb->u.ext2_sb.s_block_bitmap_number[j - 1];
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sb->u.ext2_sb.s_block_bitmap[j] =
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sb->u.ext2_sb.s_block_bitmap[j - 1];
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}
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read_block_bitmap (sb, block_group, 0);
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}
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return 0;
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}
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static inline int load_block_bitmap (struct super_block * sb,
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unsigned int block_group)
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{
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if (sb->u.ext2_sb.s_loaded_block_bitmaps > 0 &&
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sb->u.ext2_sb.s_block_bitmap_number[0] == block_group)
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return 0;
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if (sb->u.ext2_sb.s_groups_count <= EXT2_MAX_GROUP_LOADED &&
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sb->u.ext2_sb.s_block_bitmap_number[block_group] == block_group &&
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sb->u.ext2_sb.s_block_bitmap[block_group])
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return block_group;
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return load__block_bitmap (sb, block_group);
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}
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void ext2_free_blocks (struct super_block * sb, unsigned long block,
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unsigned long count)
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{
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struct buffer_head * bh;
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struct buffer_head * bh2;
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unsigned long block_group;
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unsigned long bit;
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unsigned long i;
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int bitmap_nr;
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struct ext2_group_desc * gdp;
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struct ext2_super_block * es;
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if (!sb) {
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printk ("ext2_free_blocks: nonexistent device");
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return;
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}
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lock_super (sb);
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es = sb->u.ext2_sb.s_es;
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if (block < es->s_first_data_block ||
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(block + count) > es->s_blocks_count) {
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ext2_error (sb, "ext2_free_blocks",
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"Freeing blocks not in datazone\n"
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"block = %lu, count = %lu", block, count);
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unlock_super (sb);
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return;
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}
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ext2_debug ("freeing block %lu\n", block);
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block_group = (block - es->s_first_data_block) /
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EXT2_BLOCKS_PER_GROUP(sb);
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bit = (block - es->s_first_data_block) % EXT2_BLOCKS_PER_GROUP(sb);
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if (bit + count > EXT2_BLOCKS_PER_GROUP(sb))
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ext2_panic (sb, "ext2_free_blocks",
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"Freeing blocks across group boundary\n"
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"Block = %lu, count = %lu",
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block, count);
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bitmap_nr = load_block_bitmap (sb, block_group);
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bh = sb->u.ext2_sb.s_block_bitmap[bitmap_nr];
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gdp = get_group_desc (sb, block_group, &bh2);
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if (test_opt (sb, CHECK_STRICT) &&
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(in_range (gdp->bg_block_bitmap, block, count) ||
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in_range (gdp->bg_inode_bitmap, block, count) ||
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in_range (block, gdp->bg_inode_table,
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sb->u.ext2_sb.s_itb_per_group) ||
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in_range (block + count - 1, gdp->bg_inode_table,
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sb->u.ext2_sb.s_itb_per_group)))
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ext2_panic (sb, "ext2_free_blocks",
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"Freeing blocks in system zones\n"
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"Block = %lu, count = %lu",
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block, count);
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for (i = 0; i < count; i++) {
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if (!clear_bit (bit + i, bh->b_data))
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ext2_warning (sb, "ext2_free_blocks",
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"bit already cleared for block %lu",
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block);
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else {
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gdp->bg_free_blocks_count++;
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es->s_free_blocks_count++;
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}
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}
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bh2->b_dirt = 1;
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sb->u.ext2_sb.s_sbh->b_dirt = 1;
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bh->b_dirt = 1;
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if (sb->s_flags & MS_SYNC) {
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ll_rw_block (WRITE, 1, &bh);
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wait_on_buffer (bh);
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}
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sb->s_dirt = 1;
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unlock_super (sb);
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return;
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}
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/*
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* ext2_new_block uses a goal block to assist allocation. If the goal is
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* free, or there is a free block within 32 blocks of the goal, that block
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* is allocated. Otherwise a forward search is made for a free block; within
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* each block group the search first looks for an entire free byte in the block
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* bitmap, and then for any free bit if that fails.
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*/
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int ext2_new_block (struct super_block * sb, unsigned long goal,
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unsigned long * prealloc_count,
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unsigned long * prealloc_block)
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{
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struct buffer_head * bh;
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struct buffer_head * bh2;
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char * p, * r;
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int i, j, k, tmp;
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unsigned long lmap;
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int bitmap_nr;
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struct ext2_group_desc * gdp;
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struct ext2_super_block * es;
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#ifdef EXT2FS_DEBUG
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static int goal_hits = 0, goal_attempts = 0;
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#endif
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if (!sb) {
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printk ("ext2_new_block: nonexistent device");
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return 0;
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}
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lock_super (sb);
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es = sb->u.ext2_sb.s_es;
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if (es->s_free_blocks_count <= es->s_r_blocks_count && !suser()) {
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unlock_super (sb);
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return 0;
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}
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ext2_debug ("goal=%lu.\n", goal);
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if (goal < es->s_first_data_block || goal >= es->s_blocks_count) {
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ext2_warning (sb, "ext2_new_block",
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"Goal out of bounds: %lu", goal);
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goal = es->s_first_data_block;
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}
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repeat:
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/*
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* First, test whether the goal block is free.
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*/
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i = ((goal - es->s_first_data_block) / EXT2_BLOCKS_PER_GROUP(sb));
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gdp = get_group_desc (sb, i, &bh2);
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if (gdp->bg_free_blocks_count > 0) {
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j = ((goal - es->s_first_data_block) % EXT2_BLOCKS_PER_GROUP(sb));
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#ifdef EXT2FS_DEBUG
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if (j)
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goal_attempts++;
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#endif
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bitmap_nr = load_block_bitmap (sb, i);
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bh = sb->u.ext2_sb.s_block_bitmap[bitmap_nr];
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ext2_debug ("goal is at %d:%d.\n", i, j);
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if (!test_bit(j, bh->b_data)) {
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#ifdef EXT2FS_DEBUG
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goal_hits++;
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ext2_debug ("goal bit allocated.\n");
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#endif
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goto got_block;
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}
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if (j) {
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/*
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* The goal was occupied; search forward for a free
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* block within the next 32 blocks
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*/
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lmap = ((((unsigned long *) bh->b_data)[j >> 5]) >>
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((j & 31) + 1));
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if (j < EXT2_BLOCKS_PER_GROUP(sb) - 32)
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lmap |= (((unsigned long *) bh->b_data)[(j >> 5) + 1]) <<
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(31 - (j & 31));
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else
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lmap |= 0xffffffff << (31 - (j & 31));
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if (lmap != 0xffffffffl) {
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__asm__ ("bsfl %1,%0"
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: "=r" (k)
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: "r" (~lmap));
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k++;
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if ((j + k) < EXT2_BLOCKS_PER_GROUP(sb)) {
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j += k;
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goto got_block;
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}
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}
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}
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ext2_debug ("Bit not found near goal\n");
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/*
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* There has been no free block found in the near vicinity
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* of the goal: do a search forward through the block groups,
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* searching in each group first for an entire free byte in
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* the bitmap and then for any free bit.
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*
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* Search first in the remainder of the current group; then,
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* cyclicly search throught the rest of the groups.
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*/
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p = ((char *) bh->b_data) + (j >> 3);
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r = find_first_zero_byte (p,
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(EXT2_BLOCKS_PER_GROUP(sb) - j + 7) >> 3);
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k = (r - ((char *) bh->b_data)) << 3;
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if (k < EXT2_BLOCKS_PER_GROUP(sb)) {
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j = k;
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goto search_back;
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}
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k = find_next_zero_bit ((unsigned long *) bh->b_data,
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EXT2_BLOCKS_PER_GROUP(sb),
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j);
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if (k < EXT2_BLOCKS_PER_GROUP(sb)) {
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j = k;
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goto got_block;
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}
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}
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ext2_debug ("Bit not found in block group %d.\n", i);
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/*
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* Now search the rest of the groups. We assume that
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* i and gdp correctly point to the last group visited.
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*/
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for (k = 0; k < sb->u.ext2_sb.s_groups_count; k++) {
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i++;
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if (i >= sb->u.ext2_sb.s_groups_count)
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i = 0;
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gdp = get_group_desc (sb, i, &bh2);
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if (gdp->bg_free_blocks_count > 0)
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break;
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}
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if (k >= sb->u.ext2_sb.s_groups_count) {
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unlock_super (sb);
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return 0;
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}
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bitmap_nr = load_block_bitmap (sb, i);
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bh = sb->u.ext2_sb.s_block_bitmap[bitmap_nr];
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r = find_first_zero_byte (bh->b_data,
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EXT2_BLOCKS_PER_GROUP(sb) >> 3);
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j = (r - bh->b_data) << 3;
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if (j < EXT2_BLOCKS_PER_GROUP(sb))
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goto search_back;
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else
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j = find_first_zero_bit ((unsigned long *) bh->b_data,
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EXT2_BLOCKS_PER_GROUP(sb));
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if (j >= EXT2_BLOCKS_PER_GROUP(sb)) {
|
|
ext2_error (sb, "ext2_new_block",
|
|
"Free blocks count corrupted for block group %d", i);
|
|
unlock_super (sb);
|
|
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) &&
|
|
(tmp == gdp->bg_block_bitmap ||
|
|
tmp == gdp->bg_inode_bitmap ||
|
|
in_range (tmp, gdp->bg_inode_table, sb->u.ext2_sb.s_itb_per_group)))
|
|
ext2_panic (sb, "ext2_new_block",
|
|
"Allocating block in system zone\n"
|
|
"block = %u", tmp);
|
|
|
|
if (set_bit (j, bh->b_data)) {
|
|
ext2_warning (sb, "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;
|
|
|
|
bh->b_dirt = 1;
|
|
if (sb->s_flags & MS_SYNC) {
|
|
ll_rw_block (WRITE, 1, &bh);
|
|
wait_on_buffer (bh);
|
|
}
|
|
|
|
if (j >= es->s_blocks_count) {
|
|
ext2_error (sb, "ext2_new_block",
|
|
"block >= blocks count\n"
|
|
"block_group = %d, block=%d", i, j);
|
|
unlock_super (sb);
|
|
return 0;
|
|
}
|
|
if (!(bh = getblk (sb->s_dev, j, sb->s_blocksize))) {
|
|
ext2_error (sb, "ext2_new_block", "cannot get block %d", j);
|
|
unlock_super (sb);
|
|
return 0;
|
|
}
|
|
clear_block (bh->b_data, sb->s_blocksize);
|
|
bh->b_uptodate = 1;
|
|
bh->b_dirt = 1;
|
|
brelse (bh);
|
|
|
|
ext2_debug ("allocating block %d. "
|
|
"Goal hits %d of %d.\n", j, goal_hits, goal_attempts);
|
|
|
|
gdp->bg_free_blocks_count--;
|
|
bh2->b_dirt = 1;
|
|
es->s_free_blocks_count--;
|
|
sb->u.ext2_sb.s_sbh->b_dirt = 1;
|
|
sb->s_dirt = 1;
|
|
unlock_super (sb);
|
|
return j;
|
|
}
|
|
|
|
unsigned long ext2_count_free_blocks (struct super_block * sb)
|
|
{
|
|
#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 (sb);
|
|
es = sb->u.ext2_sb.s_es;
|
|
desc_count = 0;
|
|
bitmap_count = 0;
|
|
gdp = NULL;
|
|
for (i = 0; i < sb->u.ext2_sb.s_groups_count; i++) {
|
|
gdp = get_group_desc (sb, i, NULL);
|
|
desc_count += gdp->bg_free_blocks_count;
|
|
bitmap_nr = load_block_bitmap (sb, i);
|
|
x = ext2_count_free (sb->u.ext2_sb.s_block_bitmap[bitmap_nr],
|
|
sb->s_blocksize);
|
|
printk ("group %d: stored = %d, counted = %lu\n",
|
|
i, gdp->bg_free_blocks_count, x);
|
|
bitmap_count += x;
|
|
}
|
|
printk("ext2_count_free_blocks: stored = %lu, computed = %lu, %lu\n",
|
|
es->s_free_blocks_count, desc_count, bitmap_count);
|
|
unlock_super (sb);
|
|
return bitmap_count;
|
|
#else
|
|
return sb->u.ext2_sb.s_es->s_free_blocks_count;
|
|
#endif
|
|
}
|
|
|
|
static inline int block_in_use (unsigned long block,
|
|
struct super_block * sb,
|
|
unsigned char * map)
|
|
{
|
|
return test_bit ((block - sb->u.ext2_sb.s_es->s_first_data_block) %
|
|
EXT2_BLOCKS_PER_GROUP(sb), map);
|
|
}
|
|
|
|
void ext2_check_blocks_bitmap (struct super_block * sb)
|
|
{
|
|
struct buffer_head * bh;
|
|
struct ext2_super_block * es;
|
|
unsigned long desc_count, bitmap_count, x;
|
|
int bitmap_nr;
|
|
struct ext2_group_desc * gdp;
|
|
int i, j;
|
|
|
|
lock_super (sb);
|
|
es = sb->u.ext2_sb.s_es;
|
|
desc_count = 0;
|
|
bitmap_count = 0;
|
|
gdp = NULL;
|
|
for (i = 0; i < sb->u.ext2_sb.s_groups_count; i++) {
|
|
gdp = get_group_desc (sb, i, NULL);
|
|
desc_count += gdp->bg_free_blocks_count;
|
|
bitmap_nr = load_block_bitmap (sb, i);
|
|
bh = sb->u.ext2_sb.s_block_bitmap[bitmap_nr];
|
|
|
|
if (!block_in_use (gdp->bg_block_bitmap, sb, bh->b_data))
|
|
ext2_error (sb, "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))
|
|
ext2_error (sb, "ext2_check_blocks_bitmap",
|
|
"Inode bitmap for group %d is marked free",
|
|
i);
|
|
|
|
for (j = 0; j < sb->u.ext2_sb.s_itb_per_group; j++)
|
|
if (!block_in_use (gdp->bg_inode_table + j, sb, bh->b_data))
|
|
ext2_error (sb, "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)
|
|
ext2_error (sb, "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)
|
|
ext2_error (sb, "ext2_check_blocks_bitmap",
|
|
"Wrong free blocks count in super block, "
|
|
"stored = %lu, counted = %lu",
|
|
es->s_free_blocks_count, bitmap_count);
|
|
unlock_super (sb);
|
|
}
|