Comment 2 for bug 1669414

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Laurynas Biveinis (laurynas-biveinis) wrote : Re: Failed to set O_DIRECT on file ...mysql-test/var/mysqld.1/data/xb_doublewrite when run MTR test cases

Besides the warning message, this might result in reduced durability if innodb_flush_method=ALL_O_DIRECT, similar to bug 801989.

Parallel doublewrite O_DIRECT setting is unconditional and not dependent on innodb_flush_method. The fix would be:
- only for the doublewrite buffer, downgrade the message to Note severity;
- add check for os_file_set_nocache failure in parallel doublewrite create, save it in a flag, check it before flushing in buf_dblwr_flush_buffered_writes
- fix the incorrect comment added by bug 801989 fix in os_file_create_func re. fsync on parallel doublewrite (as it uses the simple os0file API)