Btrfs: Fix super block updates during transaction commit

The super block written during commit was not consistent with the state of
the trees.  This change adds an in-memory copy of the super so that we can
make sure to write out consistent data during a commit.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index fb6fffb..1998f86 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -306,6 +306,7 @@ struct btrfs_fs_info {
        u64 generation;
        struct btrfs_transaction *running_transaction;
        struct btrfs_super_block *disk_super;
+       struct btrfs_super_block super_copy;
        struct buffer_head *sb_buffer;
        struct super_block *sb;
        struct inode *btree_inode;

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index d7615e1..7081729 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -471,6 +471,8 @@ struct btrfs_root *open_ctree(struct super_block *sb)
        if (!fs_info->sb_buffer)
                goto fail_iput;
        disk_super = (struct btrfs_super_block *)fs_info->sb_buffer->b_data;
+       fs_info->disk_super = disk_super;
+       memcpy(&fs_info->super_copy, disk_super, sizeof(fs_info->super_copy));
 
        if (!btrfs_super_root(disk_super))
                goto fail_sb_buffer;
@@ -479,7 +481,6 @@ struct btrfs_root *open_ctree(struct super_block *sb)
                     btrfs_super_total_blocks(disk_super) <<
                     fs_info->btree_inode->i_blkbits);
 
-       fs_info->disk_super = disk_super;
 
        if (strncmp((char *)(&disk_super->magic), BTRFS_MAGIC,
                    sizeof(disk_super->magic))) {
@@ -527,8 +528,6 @@ int write_ctree_super(struct btrfs_trans_handle *trans, struct btrfs_root
        int ret;
        struct buffer_head *bh = root->fs_info->sb_buffer;
 
-       btrfs_set_super_root(root->fs_info->disk_super,
-                            bh_blocknr(root->fs_info->tree_root->node));
        lock_buffer(bh);
        WARN_ON(atomic_read(&bh->b_count) < 1);
        clear_buffer_dirty(bh);

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 8025e9f..7e55034 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -796,8 +796,8 @@ static int finish_current_insert(struct btrfs_trans_handle *trans, struct
 
        for (i = 0; i < extent_root->fs_info->extent_tree_insert_nr; i++) {
                ins.objectid = extent_root->fs_info->extent_tree_insert[i];
-               super_blocks_used = btrfs_super_blocks_used(info->disk_super);
-               btrfs_set_super_blocks_used(info->disk_super,
+               super_blocks_used = btrfs_super_blocks_used(&info->super_copy);
+               btrfs_set_super_blocks_used(&info->super_copy,
                                            super_blocks_used + 1);
                ret = btrfs_insert_item(trans, extent_root, &ins, &extent_item,
                                        sizeof(extent_item));
@@ -892,8 +892,8 @@ static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
                        BUG_ON(ret);
                }
 
-               super_blocks_used = btrfs_super_blocks_used(info->disk_super);
-               btrfs_set_super_blocks_used(info->disk_super,
+               super_blocks_used = btrfs_super_blocks_used(&info->super_copy);
+               btrfs_set_super_blocks_used(&info->super_copy,
                                            super_blocks_used - num_blocks);
                ret = btrfs_del_item(trans, extent_root, path);
                if (ret) {
@@ -1032,7 +1032,7 @@ static int find_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
                info->extent_tree_prealloc_nr = 0;
        }
        if (search_end == (u64)-1)
-               search_end = btrfs_super_total_blocks(info->disk_super);
+               search_end = btrfs_super_total_blocks(&info->super_copy);
        if (hint_block) {
                block_group = btrfs_lookup_block_group(info, hint_block);
                block_group = btrfs_find_block_group(root, block_group,
@@ -1361,8 +1361,8 @@ int btrfs_alloc_extent(struct btrfs_trans_handle *trans,
                }
        }
 
-       super_blocks_used = btrfs_super_blocks_used(info->disk_super);
-       btrfs_set_super_blocks_used(info->disk_super, super_blocks_used +
+       super_blocks_used = btrfs_super_blocks_used(&info->super_copy);
+       btrfs_set_super_blocks_used(&info->super_copy, super_blocks_used +
                                    num_blocks);
        ret = btrfs_insert_item(trans, extent_root, ins, &extent_item,
                                sizeof(extent_item));
@@ -1737,7 +1737,7 @@ int btrfs_read_block_groups(struct btrfs_root *root)
                                           BTRFS_BLOCK_GROUP_AVAIL);
                }
                if (key.objectid >=
-                   btrfs_super_total_blocks(info->disk_super))
+                   btrfs_super_total_blocks(&info->super_copy))
                        break;
        }
 

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index c11ecf5..2e797d5 100644 (file)
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -144,7 +144,7 @@ static int btrfs_get_sb(struct file_system_type *fs_type,
 static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
        struct btrfs_root *root = btrfs_sb(dentry->d_sb);
-       struct btrfs_super_block *disk_super = root->fs_info->disk_super;
+       struct btrfs_super_block *disk_super = &root->fs_info->super_copy;
 
        buf->f_namelen = BTRFS_NAME_LEN;
        buf->f_blocks = btrfs_super_total_blocks(disk_super);

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index a5a63d4..3b2face 100644 (file)
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -380,6 +380,12 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
                else
                        prev_trans->use_count++;
        }
+       btrfs_set_super_generation(&root->fs_info->super_copy,
+                                  cur_trans->transid);
+       btrfs_set_super_root(&root->fs_info->super_copy,
+                            bh_blocknr(root->fs_info->tree_root->node));
+       memcpy(root->fs_info->disk_super, &root->fs_info->super_copy,
+              sizeof(root->fs_info->super_copy));
        mutex_unlock(&root->fs_info->trans_mutex);
        mutex_unlock(&root->fs_info->fs_mutex);
        ret = btrfs_write_and_wait_transaction(trans, root);
@@ -389,8 +395,6 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
                put_transaction(prev_trans);
                mutex_unlock(&root->fs_info->trans_mutex);
        }
-       btrfs_set_super_generation(root->fs_info->disk_super,
-                                  cur_trans->transid);
        BUG_ON(ret);
        write_ctree_super(trans, root);