[PATCH 2/3] ext4: honor the O_SYNC flag for aysnchronous direct I/O requests

Jeff Moyer jmoyer at redhat.com
Wed Feb 8 09:11:47 CST 2012

Jan Kara <jack at suse.cz> writes:

>   Look at what ext4_sync_file() does. It's more efficient than this.
> You need something like:
> 	commit_tid = file->f_flags & __O_SYNC ? EXT4_I(inode)->i_sync_tid :
> 						EXT4_I(inode)->i_datasync_tid;
> 	if (journal->j_flags & JBD2_BARRIER &&
> 	    !jbd2_trans_will_send_data_barrier(journal, commit_tid))
> 		needs_barrier = true;
> 	jbd2_log_start_commit(journal, commit_tid);
> 	jbd2_log_wait_commit(journal, commit_tid);
> 	if (needs_barrier)
> 		blkdev_issue_flush(inode->i_sb->s_bdev, GFP_NOIO, NULL);

If the transaction won't send a data barrier, wouldn't you want to issue
the flush on the data device prior to commiting the transaction, not
after it?


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