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>

5 files changed, 18 insertions, 14 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index fb6fffb71dd0..1998f86df08a 100644
--- 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 d7615e1578cc..7081729d5b16 100644
--- 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 8025e9f8ef19..7e550343aee7 100644
--- 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 c11ecf500202..2e797d5fb281 100644
--- 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 a5a63d471e43..3b2face593e9 100644
--- 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);