1 files changed, 244 insertions, 0 deletions

diff --git a/fs/ext4/block_validity.c b/fs/ext4/block_validity.c
new file mode 100644
index 000000000000..50784ef07563
--- /dev/null
+++ b/fs/ext4/block_validity.c
@@ -0,0 +1,244 @@
+/*
+ *  linux/fs/ext4/block_validity.c
+ *
+ * Copyright (C) 2009
+ * Theodore Ts'o (tytso@mit.edu)
+ *
+ * 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/module.h>
+#include <linux/swap.h>
+#include <linux/pagemap.h>
+#include <linux/version.h>
+#include <linux/blkdev.h>
+#include <linux/mutex.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 init_ext4_system_zone(void)
+{
+        ext4_system_zone_cachep = KMEM_CACHE(ext4_system_zone,
+                                             SLAB_RECLAIM_ACCOUNT);
+        if (ext4_system_zone_cachep == NULL)
+                return -ENOMEM;
+        return 0;
+}
+
+void exit_ext4_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),
+                                        sbi->s_gdb_count + 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_node = NULL;
+                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_node = NULL;
+}
+
+/*
+ * 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 > ext4_blocks_count(sbi->s_es)))
+                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
+                        return 0;
+        }
+        return 1;
+}
+