1. don't allocate redundant memory in read_all_xattrs.
2. introduce RESERVED_XATTR_SIZE for cleanup.
Signed-off-by: NChao Yu <yuchao0@huawei.com>
Reviewed-by: NKinglong Mee <kinglongmee@gmail.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>