balloc.c

Linux Kernel 2.6.9 for OMAP1710

/*
 *  linux/fs/ext2/balloc.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card ([e-mail])
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  Enhanced block allocation by Stephen Tweedie ([e-mail]), 1993
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller ([e-mail]), 1995
 */

#include <linux/config.h>
#include "ext2.h"
#include <linux/quotaops.h>
#include <linux/sched.h>
#include <linux/buffer_head.h>

/*
 * balloc.c contains the blocks allocation and deallocation routines
 */

/*
 * 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).
 */


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

struct ext2_group_desc * ext2_get_group_desc(struct super_block * sb,
					     unsigned int block_group,
					     struct buffer_head ** bh)
{
	unsigned long group_desc;
	unsigned long offset;
	struct ext2_group_desc * desc;
	struct ext2_sb_info *sbi = EXT2_SB(sb);

	if (block_group >= sbi->s_groups_count) {
		ext2_error (sb, "ext2_get_group_desc",
			    "block_group >= groups_count - "
			    "block_group = %d, groups_count = %lu",
			    block_group, sbi->s_groups_count);

		return NULL;
	}
	
	group_desc = block_group / EXT2_DESC_PER_BLOCK(sb);
	offset = block_group % EXT2_DESC_PER_BLOCK(sb);
	if (!sbi->s_group_desc[group_desc]) {
		ext2_error (sb, "ext2_get_group_desc",
			    "Group descriptor not loaded - "
			    "block_group = %d, group_desc = %lu, desc = %lu",
			     block_group, group_desc, offset);
		return NULL;
	}
	
	desc = (struct ext2_group_desc *) sbi->s_group_desc[group_desc]->b_data;
	if (bh)
		*bh = sbi->s_group_desc[group_desc];
	return desc + offset;
}

/*
 * Read the bitmap for a given block_group, reading into the specified 
 * slot in the superblock's bitmap cache.
 *
 * Return buffer_head on success or NULL in case of failure.
 */
static struct buffer_head *
read_block_bitmap(struct super_block *sb, unsigned int block_group)
{
	struct ext2_group_desc * desc;
	struct buffer_head * bh = NULL;
	
	desc = ext2_get_group_desc (sb, block_group, NULL);
	if (!desc)
		goto error_out;
	bh = sb_bread(sb, le32_to_cpu(desc->bg_block_bitmap));
	if (!bh)
		ext2_error (sb, "read_block_bitmap",
			    "Cannot read block bitmap - "
			    "block_group = %d, block_bitmap = %u",
			    block_group, le32_to_cpu(desc->bg_block_bitmap));
error_out:
	return bh;
}

/*
 * Set sb->s_dirt here because the superblock was "logically" altered.  We
 * need to recalculate its free blocks count and flush it out.
 */
static int reserve_blocks(struct super_block *sb, int count)
{
	struct ext2_sb_info *sbi = EXT2_SB(sb);
	struct ext2_super_block *es = sbi->s_es;
	unsigned free_blocks;
	unsigned root_blocks;

	free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
	root_blocks = le32_to_cpu(es->s_r_blocks_count);

	if (free_blocks < count)
		count = free_blocks;

	if (free_blocks < root_blocks + count && !capable(CAP_SYS_RESOURCE) &&
	    sbi->s_resuid != current->fsuid &&
	    (sbi->s_resgid == 0 || !in_group_p (sbi->s_resgid))) {
		/*
		 * We are too close to reserve and we are not privileged.
		 * Can we allocate anything at all?
		 */
		if (free_blocks > root_blocks)
			count = free_blocks - root_blocks;
		else
			return 0;
	}

	percpu_counter_mod(&sbi->s_freeblocks_counter, -count);
	sb->s_dirt = 1;
	return count;
}

static void release_blocks(struct super_block *sb, int count)
{
	if (count) {
		struct ext2_sb_info *sbi = EXT2_SB(sb);

		percpu_counter_mod(&sbi->s_freeblocks_counter, count);
		sb->s_dirt = 1;
	}
}

static int group_reserve_blocks(struct ext2_sb_info *sbi, int group_no,
	struct ext2_group_desc *desc, struct buffer_head *bh, int count)
{
	unsigned free_blocks;

	if (!desc->bg_free_blocks_count)
		return 0;

	spin_lock(sb_bgl_lock(sbi, group_no));
	free_blocks = le16_to_cpu(desc->bg_free_blocks_count);
	if (free_blocks < count)
		count = free_blocks;
	desc->bg_free_blocks_count = cpu_to_le16(free_blocks - count);
	spin_unlock(sb_bgl_lock(sbi, group_no));
	mark_buffer_dirty(bh);
	return count;
}

static void group_release_blocks(struct super_block *sb, int group_no,
	struct ext2_group_desc *desc, struct buffer_head *bh, int count)
{
	if (count) {
		struct ext2_sb_info *sbi = EXT2_SB(sb);
		unsigned free_blocks;

		spin_lock(sb_bgl_lock(sbi, group_no));
		free_blocks = le16_to_cpu(desc->bg_free_blocks_count);
		desc->bg_free_blocks_count = cpu_to_le16(free_blocks + count);
		spin_unlock(sb_bgl_lock(sbi, group_no));
		sb->s_dirt = 1;
		mark_buffer_dirty(bh);
	}
}

/* Free given blocks, update quota and i_blocks field */
void ext2_free_blocks (struct inode * inode, unsigned long block,
		       unsigned long count)
{
	struct buffer_head *bitmap_bh = NULL;
	struct buffer_head * bh2;
	unsigned long block_group;
	unsigned long bit;
	unsigned long i;
	unsigned long overflow;
	struct super_block * sb = inode->i_sb;
	struct ext2_sb_info * sbi = EXT2_SB(sb);
	struct ext2_group_desc * desc;
	struct ext2_super_block * es = sbi->s_es;
	unsigned freed = 0, group_freed;

	if (block < le32_to_cpu(es->s_first_data_block) ||
	    block + count < block ||
	    block + count > le32_to_cpu(es->s_blocks_count)) {
		ext2_error (sb, "ext2_free_blocks",
			    "Freeing blocks not in datazone - "
			    "block = %lu, count = %lu", block, count);
		goto error_return;
	}

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

do_more:
	overflow = 0;
	block_group = (block - le32_to_cpu(es->s_first_data_block)) /
		      EXT2_BLOCKS_PER_GROUP(sb);
	bit = (block - le32_to_cpu(es->s_first_data_block)) %
		      EXT2_BLOCKS_PER_GROUP(sb);
	/*
	 * Check to see if we are freeing blocks across a group
	 * boundary.
	 */
	if (bit + count > EXT2_BLOCKS_PER_GROUP(sb)) {
		overflow = bit + count - EXT2_BLOCKS_PER_GROUP(sb);
		count -= overflow;
	}
	brelse(bitmap_bh);
	bitmap_bh = read_block_bitmap(sb, block_group);
	if (!bitmap_bh)
		goto error_return;

	desc = ext2_get_group_desc (sb, block_group, &bh2);
	if (!desc)
		goto error_return;

	if (in_range (le32_to_cpu(desc->bg_block_bitmap), block, count) ||
	    in_range (le32_to_cpu(desc->bg_inode_bitmap), block, count) ||
	    in_range (block, le32_to_cpu(desc->bg_inode_table),
		      sbi->s_itb_per_group) ||
	    in_range (block + count - 1, le32_to_cpu(desc->bg_inode_table),
		      sbi->s_itb_per_group))
		ext2_error (sb, "ext2_free_blocks",
			    "Freeing blocks in system zones - "
			    "Block = %lu, count = %lu",
			    block, count);

	for (i = 0, group_freed = 0; i < count; i++) {
		if (!ext2_clear_bit_atomic(sb_bgl_lock(sbi, block_group),
					bit + i, (void *) bitmap_bh->b_data))
			ext2_error (sb, "ext2_free_blocks",
				      "bit already cleared for block %lu",
				      block + i);
		else
			group_freed++;
	}

	mark_buffer_dirty(bitmap_bh);
	if (sb->s_flags & MS_SYNCHRONOUS)
		sync_dirty_buffer(bitmap_bh);

	group_release_blocks(sb, block_group, desc, bh2, group_freed);
	freed += group_freed;

	if (overflow) {
		block += count;
		count = overflow;
		goto do_more;
	}
error_return:
	brelse(bitmap_bh);
	release_blocks(sb, freed);
	DQUOT_FREE_BLOCK(inode, freed);
}

static int grab_block(spinlock_t *lock, char *map, unsigned size, int goal)
{
	int k;
	char *p, *r;

	if (!ext2_test_bit(goal, map))
		goto got_it;

repeat:
	if (goal) {
		/*
		 * 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..
		 */
		k = (goal + 63) & ~63;
		goal = ext2_find_next_zero_bit(map, k, goal);
		if (goal < k)
			goto got_it;
		/*
		 * Search in the remainder of the current group.
		 */
	}

	p = map + (goal >> 3);
	r = memscan(p, 0, (size - goal + 7) >> 3);
	k = (r - map) << 3;
	if (k < size) {
		/* 
		 * We have succeeded in finding a free byte in the block
		 * bitmap.  Now search backwards to find the start of this
		 * group of free blocks - won't take more than 7 iterations.
		 */
		for (goal = k; goal && !ext2_test_bit (goal - 1, map); goal--)
			;
		goto got_it;
	}

	k = ext2_find_next_zero_bit ((u32 *)map, size, goal);
	if (k < size) {
		goal = k;
		goto got_it;
	}
	return -1;
got_it:
	if (ext2_set_bit_atomic(lock, goal, (void *) map)) 
		goto repeat;	
	return goal;
}

/*
 * 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.
 * This function also updates quota and i_blocks field.
 */
int ext2_new_block(struct inode *inode, unsigned long goal,
			u32 *prealloc_count, u32 *prealloc_block, int *err)
{
	struct buffer_head *bitmap_bh = NULL;
	struct buffer_head *gdp_bh;	/* bh2 */
	struct ext2_group_desc *desc;
	int group_no;			/* i */
	int ret_block;			/* j */
	int group_idx;			/* k */
	int target_block;		/* tmp */
	int block = 0;
	struct super_block *sb = inode->i_sb;
	struct ext2_sb_info *sbi = EXT2_SB(sb);
	struct ext2_super_block *es = sbi->s_es;
	unsigned group_size = EXT2_BLOCKS_PER_GROUP(sb);
	unsigned prealloc_goal = es->s_prealloc_blocks;
	unsigned group_alloc = 0, es_alloc, dq_alloc;
	int nr_scanned_groups;

	if (!prealloc_goal--)
		prealloc_goal = EXT2_DEFAULT_PREALLOC_BLOCKS - 1;
	if (!prealloc_count || *prealloc_count)
		prealloc_goal = 0;

	if (DQUOT_ALLOC_BLOCK(inode, 1)) {
		*err = -EDQUOT;