linux-ext4 - Re: [PATCH 5/7] xfs: honor the O_SYNC flag for aysnchronous direct I/O requests

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Message-ID: <x49d37tj2ji.fsf@segfault.boston.devel.redhat.com>
Date:	Fri, 30 Mar 2012 15:45:37 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Dave Chinner <david@...morbit.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
	xfs@....sgi.com, jack@...e.cz, hch@...radead.org
Subject: Re: [PATCH 5/7] xfs: honor the O_SYNC flag for aysnchronous direct I/O requests

Jeff Moyer <jmoyer@...hat.com> writes:

> Hi, Dave,
>
> Thanks for the review!
>
>> 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


View attachment "xfs-factor-out-xfs-file-fsync.patch" of type "text/plain" (1678 bytes)

View attachment "xfs-flush-disk-cache-for-aio-dio-osync-writes.patch" of type "text/plain" (5318 bytes)