Re: [PATCH 5/7] xfs: honor the O_SYNC flag for aysnchronous direct I/O requests

Jeff Moyer [off-list ref] writes:

Hi, Dave,

Thanks for the review!

quoted

or better still, factor xfs_file_fsync() so that it calls a helper
that doesn't wait for data IO completion, and call that helper here
too. The semantics of fsync/fdatasync are too complex to have to
implement and maintain in multiple locations....

I definitely agree with consolidating things.  However, there are four
blocking calls in xfs_file_fsync (filemap_write_and_wait_range,
xfs_blkdev_issue_flush, _xfs_log_force_lsn, and another call to
xfs_blkdev_issue_flush).  How would you propose to make that
non-blocking given that those steps have to happen in sequence?

OK, so re-reading your mail, I think you meant to just factor out
everything except the filemap_write_and_wait_range.  Here are a couple
of patches which do that.  Also, since we're not worried about blocking
in the endio processing, just making things synchronous makes the code a
lot simpler.  Let me know what you think of the attached two patches
(which I've already run through xfstests).

Thanks!
Jeff