path: root/fs/ext2/balloc.c

/*
 *  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@redhat.com), 1993
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller (davem@caip.rutgers.edu), 1995
 */

#include "ext2.h"
#include <linux/quotaops.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/buffer_head.h>
#include <linux/capability.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_fill_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_BITS(sb);
	offset = block_group & (EXT2_DESC_PER_BLOCK(sb) - 1);
	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;
}

static int ext2_valid_block_bitmap(struct super_block *sb,
					struct ext2_group_desc *desc,
					unsigned int block_group,
					struct buffer_head *bh)
{
	ext2_grpblk_t offset;
	ext2_grpblk_t next_zero_bit;
	ext2_fsblk_t bitmap_blk;
	ext2_fsblk_t group_first_block;

	group_first_block = ext2_group_first_block_no(sb, block_group);

	/* check whether block bitmap block number is set */
	bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
	offset = bitmap_blk - group_first_block;
	if (!ext2_test_bit(offset, bh->b_data))
		/* bad block bitmap */
		goto err_out;

	/* check whether the inode bitmap block number is set */
	bitmap_blk = le32_to_cpu(desc->bg_inode_bitmap);
	offset = bitmap_blk - group_first_block;
	if (!ext2_test_bit(offset, bh->b_data))
		/* bad block bitmap */
		goto err_out;

	/* check whether the inode table block number is set */
	bitmap_blk = le32_to_cpu(desc->bg_inode_table);
	offset = bitmap_blk - group_first_block;
	next_zero_bit = ext2_find_next_zero_bit(bh->b_data,
				offset + EXT2_SB(sb)->s_itb_per_group,
				offset);
	if (next_zero_bit >= offset + EXT2_SB(sb)->s_itb_per_group)
		/* good bitmap for inode tables */
		return 1;

err_out:
	ext2_error(sb, __func__,
			"Invalid block bitmap - "
			"block_group = %d, block = %lu",
			block_group, bitmap_blk);
	return 0;
}

/*
 * Read the bitmap for a given block_group,and validate the
 * bits for block/inode/inode tables are set in the bitmaps
 *
 * 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;
	ext2_fsblk_t bitmap_blk;

	desc = ext2_get_group_desc(sb, block_group, NULL);
	if (!desc)
		return NULL;
	bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
	bh = sb_getblk(sb, bitmap_blk);
	if (unlikely(!bh)) {
		ext2_error(sb, __func__,
			    "Cannot read block bitmap - "
			    "block_group = %d, block_bitmap = %u",
			    block_group, le32_to_cpu(desc->bg_block_bitmap));
		return NULL;
	}
	if (likely(bh_uptodate_or_lock(bh)))
		return bh;

	if (bh_submit_read(bh) < 0) {
		brelse(bh);
		ext2_error(sb, __func__,
			    "Cannot read block bitmap - "
			    "block_group = %d, block_bitmap = %u",
			    block_group, le32_to_cpu(desc->bg_block_bitmap));
		return NULL;
	}

	ext2_valid_block_bitmap(sb, desc, block_group, bh);
	/*
	 * file system mounted not to panic on error, continue with corrupt
	 * bitmap
	 */
	return bh;
}

static void group_adjust_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));
		mark_buffer_dirty(bh);
	}
}

/*
 * The reservation window structure operations
 * --------------------------------------------
 * Operations include:
 * dump, find, add, remove, is_empty, find_next_reservable_window, etc.
 *
 * We use a red-black tree to represent per-filesystem reservation
 * windows.
 *
 */

/**
 * __rsv_window_dump() -- Dump the filesystem block allocation reservation map
 * @rb_root:		root of per-filesystem reservation rb tree
 * @verbose:		verbose mode
 * @fn:			function which wishes to dump the reservation map
 *
 * If verbose is turned on, it will print the whole block reservation
 * windows(start, end). Otherwise, it will only print out the "bad" windows,
 * those windows that overlap with their immediate neighbors.
 */
#if 1
static void __rsv_window_dump(struct rb_root *root, int verbose,
			      const char *fn)
{
	struct rb_node *n;
	struct ext2_reserve_window_node *rsv, *prev;
	int bad;

restart:
	n = rb_first(root);
	bad = 0;
	prev = NULL;

	printk("Block Allocation Reservation Windows Map (%s):\n", fn);
	while (n) {
		rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
		if (verbose)
			printk("reservation window 0x%p "
				"start: %lu, end: %lu\n",
				rsv, rsv->rsv_start, rsv->rsv_end);
		if (rsv->rsv_start && rsv->rsv_start >= rsv->rsv_end) {
			printk("Bad reservation %p (start >= end)\n",
			       rsv);
			bad = 1;
		}
		if (prev && prev->