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Re: [PATCH 4/9] xfs: honor the O_SYNC flag for aysnchronous direct I/O r

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 4/9] xfs: honor the O_SYNC flag for aysnchronous direct I/O requests
From: Jeff Moyer <jmoyer@xxxxxxxxxx>
Date: Tue, 20 Nov 2012 14:42:48 -0500
Cc: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>, axboe@xxxxxxxxx, tytso@xxxxxxx, bpm@xxxxxxx, viro@xxxxxxxxxxxxxxxxxx, jack@xxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, hch@xxxxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, djwong+kernel@xxxxxxxxxx
In-reply-to: <20121120112038.GC2591@dastard> (Dave Chinner's message of "Tue, 20 Nov 2012 22:20:38 +1100")
References: <20121120074116.24645.36369.stgit@xxxxxxxxxxxxxxxxxxx> <20121120075114.25270.40680.stgit@xxxxxxxxxxxxxxxxxxx> <20121120112038.GC2591@dastard>
User-agent: Gnus/5.110011 (No Gnus v0.11) Emacs/23.1 (gnu/linux)
Dave Chinner <david@xxxxxxxxxxxxx> writes:

> And requeuing work from one workqueue to the next is something that
> we can avoid.  We know at IO submission time (i.e.
> xfs_vm_direct_io)) whether an fsync completion is going to be needed
> during Io completion.  The ioend->io_needs_fsync flag can be set
> then, and the first pass through xfs_finish_ioend() can queue it to
> the correct workqueue.  i.e. it only needs to be queued if it's not
> already an unwritten or append ioend and it needs an fsync.
>
> As it is, all the data completion workqueues run the same completion
> function so all you need to do is handle the fsync case at the end
> of the existing processing - it's not an else case. i.e the end of
> xfs_end_io() becomes:
>
>       if (ioend->io_needs_fsync) {
>               error = xfs_ioend_fsync(ioend);
>               if (error)
>                       ioend->io_error = -error;
>               goto done;
>       }
> done:
>       xfs_destroy_ioend(ioend);

Works for me, that makes things simpler.

> As it is, this code is going to change before these changes go in -
> there's a nasty regression in the DIO code that I found this
> afternoon that requires reworking this IO completion logic to
> avoid. The patch will appear on the list soon....

I'm not on the xfs list, so if you haven't already sent it, mind Cc-ing
me?

>> --- a/fs/xfs/xfs_mount.h
>> +++ b/fs/xfs/xfs_mount.h
>> @@ -209,6 +209,7 @@ typedef struct xfs_mount {
>>      struct workqueue_struct *m_data_workqueue;
>>      struct workqueue_struct *m_unwritten_workqueue;
>>      struct workqueue_struct *m_cil_workqueue;
>> +    struct workqueue_struct *m_aio_blkdev_flush_wq;
>
>       struct workqueue_struct *m_aio_fsync_wq;

For the record, m_aio_blkdev_flush_wq is the name you chose previously.
;-)

Thanks for the review!

Cheers,
Jeff

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