NTFS: - In fs/ntfs/compress.c, use i_size_read() at the start and then use the

cached value everywhere.  Cache the initialized_size in the same way
	and protect the critical region where the two sizes are read using the
	new size_lock of the ntfs inode.
      - Add the new size_lock to the ntfs_inode structure (fs/ntfs/inode.h)
	and initialize it (fs/ntfs/inode.c).

Signed-off-by: Anton Altaparmakov <aia21@cantab.net>

fs/ntfs/inode.h

@@ -44,6 +44,7 @@ typedef struct _ntfs_inode ntfs_inode;
  * fields already provided in the VFS inode.
  */
 struct _ntfs_inode {
+	rwlock_t size_lock;	/* Lock serializing access to inode sizes. */
 	s64 initialized_size;	/* Copy from the attribute record. */
 	s64 allocated_size;	/* Copy from the attribute record. */
 	unsigned long state;	/* NTFS specific flags describing this inode.