block_validity.c

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/*
 *  linux/fs/ext4/block_validity.c
 *
 * Copyright (C) 2009
 * Theodore Ts'o ([email protected])
 *
 * Track which blocks in the filesystem are metadata blocks that
 * should never be used as data blocks by files or directories.
 */

#include <linux/time.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/quotaops.h>
#include <linux/buffer_head.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/blkdev.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include "ext4.h"

struct ext4_system_zone {
    struct rb_node  node;
    ext4_fsblk_t    start_blk;
    unsigned int    count;
};

static struct kmem_cache *ext4_system_zone_cachep;

int __init ext4_init_system_zone(void)
{
    ext4_system_zone_cachep = KMEM_CACHE(ext4_system_zone, 0);
    if (ext4_system_zone_cachep == NULL)
        return -ENOMEM;
    return 0;
}

void ext4_exit_system_zone(void)
{
    kmem_cache_destroy(ext4_system_zone_cachep);
}

static inline int can_merge(struct ext4_system_zone *entry1,
             struct ext4_system_zone *entry2)
{
    if ((entry1->start_blk + entry1->count) == entry2->start_blk)
        return 1;
    return 0;
}

/*
 * Mark a range of blocks as belonging to the "system zone" --- that
 * is, filesystem metadata blocks which should never be used by
 * inodes.
 */
static int add_system_zone(struct ext4_sb_info *sbi,
               ext4_fsblk_t start_blk,
               unsigned int count)
{
    struct ext4_system_zone *new_entry = NULL, *entry;
    struct rb_node **n = &sbi->system_blks.rb_node, *node;
    struct rb_node *parent = NULL, *new_node = NULL;

    while (*n) {
        parent = *n;
        entry = rb_entry(parent, struct ext4_system_zone, node);
        if (start_blk < entry->start_blk)
            n = &(*n)->rb_left;
        else if (start_blk >= (entry->start_blk + entry->count))
            n = &(*n)->rb_right;
        else {
            if (start_blk + count > (entry->start_blk +
                         entry->count))
                entry->count = (start_blk + count -
                        entry->start_blk);
            new_node = *n;
            new_entry = rb_entry(new_node, struct ext4_system_zone,
                         node);
            break;
        }
    }

    if (!new_entry) {
        new_entry = kmem_cache_alloc(ext4_system_zone_cachep,
                         GFP_KERNEL);
        if (!new_entry)
            return -ENOMEM;
        new_entry->start_blk = start_blk;
        new_entry->count = count;
        new_node = &new_entry->node;

        rb_link_node(new_node, parent, n);
        rb_insert_color(new_node, &sbi->system_blks);
    }

    /* Can we merge to the left? */
    node = rb_prev(new_node);
    if (node) {
        entry = rb_entry(node, struct ext4_system_zone, node);
        if (can_merge(entry, new_entry)) {
            new_entry->start_blk = entry->start_blk;
            new_entry->count += entry->count;
            rb_erase(node, &sbi->system_blks);
            kmem_cache_free(ext4_system_zone_cachep, entry);
        }
    }

    /* Can we merge to the right? */
    node = rb_next(new_node);
    if (node) {
        entry = rb_entry(node, struct ext4_system_zone, node);
        if (can_merge(new_entry, entry)) {
            new_entry->count += entry->count;
            rb_erase(node, &sbi->system_blks);
            kmem_cache_free(ext4_system_zone_cachep, entry);
        }
    }
    return 0;
}

static void debug_print_tree(struct ext4_sb_info *sbi)
{
    struct rb_node *node;
    struct ext4_system_zone *entry;
    int first = 1;

    printk(KERN_INFO "System zones: ");
    node = rb_first(&sbi->system_blks);
    while (node) {
        entry = rb_entry(node, struct ext4_system_zone, node);
        printk("%s%llu-%llu", first ? "" : ", ",
               entry->start_blk, entry->start_blk + entry->count - 1);
        first = 0;
        node = rb_next(node);
    }
    printk("\n");
}

int ext4_setup_system_zone(struct super_block *sb)
{
    ext4_group_t ngroups = ext4_get_groups_count(sb);
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    struct ext4_group_desc *gdp;
    ext4_group_t i;
    int flex_size = ext4_flex_bg_size(sbi);
    int ret;

    if (!test_opt(sb, BLOCK_VALIDITY)) {
        if (EXT4_SB(sb)->system_blks.rb_node)
            ext4_release_system_zone(sb);
        return 0;
    }
    if (EXT4_SB(sb)->system_blks.rb_node)
        return 0;

    for (i=0; i < ngroups; i++) {
        if (ext4_bg_has_super(sb, i) &&
            ((i < 5) || ((i % flex_size) == 0)))
            add_system_zone(sbi, ext4_group_first_block_no(sb, i),
                    ext4_bg_num_gdb(sb, i) + 1);
        gdp = ext4_get_group_desc(sb, i, NULL);
        ret = add_system_zone(sbi, ext4_block_bitmap(sb, gdp), 1);
        if (ret)
            return ret;
        ret = add_system_zone(sbi, ext4_inode_bitmap(sb, gdp), 1);
        if (ret)
            return ret;
        ret = add_system_zone(sbi, ext4_inode_table(sb, gdp),
                sbi->s_itb_per_group);
        if (ret)
            return ret;
    }

    if (test_opt(sb, DEBUG))
        debug_print_tree(EXT4_SB(sb));
    return 0;
}

/* Called when the filesystem is unmounted */
void ext4_release_system_zone(struct super_block *sb)
{
    struct rb_node  *n = EXT4_SB(sb)->system_blks.rb_node;
    struct rb_node  *parent;
    struct ext4_system_zone *entry;

    while (n) {
        /* Do the node's children first */
        if (n->rb_left) {
            n = n->rb_left;
            continue;
        }
        if (n->rb_right) {
            n = n->rb_right;
            continue;
        }
        /*
         * The node has no children; free it, and then zero
         * out parent's link to it.  Finally go to the
         * beginning of the loop and try to free the parent
         * node.
         */
        parent = rb_parent(n);
        entry = rb_entry(n, struct ext4_system_zone, node);
        kmem_cache_free(ext4_system_zone_cachep, entry);
        if (!parent)
            EXT4_SB(sb)->system_blks = RB_ROOT;
        else if (parent->rb_left == n)
            parent->rb_left = NULL;
        else if (parent->rb_right == n)
            parent->rb_right = NULL;
        n = parent;
    }
    EXT4_SB(sb)->system_blks = RB_ROOT;
}

/*
 * Returns 1 if the passed-in block region (start_blk,
 * start_blk+count) is valid; 0 if some part of the block region
 * overlaps with filesystem metadata blocks.
 */
int ext4_data_block_valid(struct ext4_sb_info *sbi, ext4_fsblk_t start_blk,
              unsigned int count)
{
    struct ext4_system_zone *entry;
    struct rb_node *n = sbi->system_blks.rb_node;

    if ((start_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
        (start_blk + count < start_blk) ||
        (start_blk + count > ext4_blocks_count(sbi->s_es))) {
        sbi->s_es->s_last_error_block = cpu_to_le64(start_blk);
        return 0;
    }
    while (n) {
        entry = rb_entry(n, struct ext4_system_zone, node);
        if (start_blk + count - 1 < entry->start_blk)
            n = n->rb_left;
        else if (start_blk >= (entry->start_blk + entry->count))
            n = n->rb_right;
        else {
            sbi->s_es->s_last_error_block = cpu_to_le64(start_blk);
            return 0;
        }
    }
    return 1;
}

int ext4_check_blockref(const char *function, unsigned int line,
            struct inode *inode, __le32 *p, unsigned int max)
{
    struct ext4_super_block *es = EXT4_SB(inode->i_sb)->s_es;
    __le32 *bref = p;
    unsigned int blk;

    while (bref < p+max) {
        blk = le32_to_cpu(*bref++);
        if (blk &&
            unlikely(!ext4_data_block_valid(EXT4_SB(inode->i_sb),
                            blk, 1))) {
            es->s_last_error_block = cpu_to_le64(blk);
            ext4_error_inode(inode, function, line, blk,
                     "invalid block");
            return -EIO;
        }
    }
    return 0;
}