Wrap decrease btree height in a transaction (fix utsaslab#9)

Linux-5.1/fs/winefs/inode.c

@@ -564,16 +564,8 @@ static void pmfs_decrease_btree_height(struct super_block *sb,
  height--;
  }
 update_root_and_height:
- /* pi->height and pi->root need to be atomically updated. use
- * cmpxchg16 here. The following is dependent on a specific layout of
- * inode fields */
- *(u64 *)b = *(u64 *)pi;
- /* pi->height is at offset 2 from pi */
- b[2] = (u8)new_height;
- /* TODO: the following function assumes cmpxchg16b instruction writes
- * 16 bytes atomically. Confirm if it is really true. */
- cmpxchg_double_local((u64 *)pi, &pi->root, *(u64 *)pi, pi->root,
- *(u64 *)b, newroot);
+ pi->root = newroot;
+ pi->height = height;
 }
 
 static unsigned long pmfs_inode_count_iblocks_recursive(struct super_block *sb,
@@ -630,6 +622,7 @@ static void __pmfs_truncate_blocks(struct inode *inode, loff_t start,
  unsigned int freed = 0;
  unsigned int data_bits = blk_type_to_shift[pi->i_blk_type];
  unsigned int meta_bits = META_BLK_SHIFT;
+ struct pmfs_transaction *trans;
  bool mpty;
 
  inode->i_mtime = inode->i_ctime = current_time(inode);
@@ -681,6 +674,11 @@ static void __pmfs_truncate_blocks(struct inode *inode, loff_t start,
  inode->i_blocks -= (freed * (1 << (data_bits -
  sb->s_blocksize_bits)));
 
+ PERSISTENT_BARRIER();
+ BUG_ON(pmfs_current_transaction());
+ trans = pmfs_new_transaction(sb, MAX_INODE_LENTRIES, pmfs_get_cpuid(sb));
+ pmfs_add_logentry(sb, trans, pi, sizeof(*pi), LE_DATA);
+
  pmfs_memunlock_inode(sb, pi);
  pi->i_blocks = cpu_to_le64(inode->i_blocks);
  pi->i_mtime = cpu_to_le32(inode->i_mtime.tv_sec);
@@ -690,7 +688,8 @@ static void __pmfs_truncate_blocks(struct inode *inode, loff_t start,
  check_eof_blocks(sb, pi, inode->i_size);
  pmfs_memlock_inode(sb, pi);
  /* now flush the inode's first cacheline which was modified */
- pmfs_flush_buffer(pi, 1, false);
+ pmfs_flush_buffer(pi, 1, true);
+ pmfs_commit_transaction(sb, trans);
  return;
 end_truncate_blocks:
  /* we still need to update ctime and mtime */