1)Function ecryptfs_do_readpage() calls flush_dcache_page(lower_page),
  but lower_page was't changed here. So remove this line.

2)prepare_write ret val was ignored in ecryptfs_write_inode_size_to_header().
If error happends we can't call commit_write, just do cleanup and fial.
It is issue easy to reproduce with full lower_fs, in this case prepare_write()
will return ENOSPC.
Signed-off-by: Dmitriy Monakhov <dmonakhov@openvz.org>
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