On Fri, Jun 15, 2018 at 04:24:14AM -0700, Christoph Hellwig wrote:
> On Thu, Jun 14, 2018 at 09:43:07AM -0400, Brian Foster wrote:
> > Sync and async buffer submission both do generally similar things
> > with a couple odd exceptions. Refactor the core buffer submission
> > code into a common helper to isolate buffer submission from
> > completion handling of synchronous buffer I/O.
> >
> > This patch does not change behavior. It is a step towards support
> > for using synchronous buffer I/O via synchronous delwri queue
> > submission.
> >
> > Designed-by: Dave Chinner <dchinner@xxxxxxxxxx>
> > Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
> > ---
> >
> > v3:
> > - Leave tracepoint in __xfs_buf_submit and kill
> > trace_xfs_buf_submit_wait().
> >
> > fs/xfs/xfs_buf.c | 85 ++++++++++++++++++++--------------------------
> > fs/xfs/xfs_trace.h | 1 -
> > 2 files changed, 37 insertions(+), 49 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> > index e9c058e3761c..7b0f7c79cd62 100644
> > --- a/fs/xfs/xfs_buf.c
> > +++ b/fs/xfs/xfs_buf.c
> > @@ -1458,22 +1458,20 @@ _xfs_buf_ioapply(
> > * a call to this function unless the caller holds an additional reference
> > * itself.
> > */
> > -void
> > -xfs_buf_submit(
> > +static int
> > +__xfs_buf_submit(
> > struct xfs_buf *bp)
> > {
> > trace_xfs_buf_submit(bp, _RET_IP_);
> >
> > ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
> > - ASSERT(bp->b_flags & XBF_ASYNC);
> >
> > /* on shutdown we stale and complete the buffer immediately */
> > if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
> > xfs_buf_ioerror(bp, -EIO);
> > bp->b_flags &= ~XBF_DONE;
> > xfs_buf_stale(bp);
> > - xfs_buf_ioend(bp);
> > - return;
> > + return -EIO;
> > }
> >
> > if (bp->b_flags & XBF_WRITE)
> > @@ -1482,23 +1480,14 @@ xfs_buf_submit(
> > /* clear the internal error state to avoid spurious errors */
> > bp->b_io_error = 0;
> >
> > - /*
> > - * The caller's reference is released during I/O completion.
> > - * This occurs some time after the last b_io_remaining reference is
> > - * released, so after we drop our Io reference we have to have some
> > - * other reference to ensure the buffer doesn't go away from underneath
> > - * us. Take a direct reference to ensure we have safe access to the
> > - * buffer until we are finished with it.
> > - */
> > - xfs_buf_hold(bp);
> > -
> > /*
> > * Set the count to 1 initially, this will stop an I/O completion
> > * callout which happens before we have started all the I/O from calling
> > * xfs_buf_ioend too early.
> > */
> > atomic_set(&bp->b_io_remaining, 1);
> > - xfs_buf_ioacct_inc(bp);
> > + if (bp->b_flags & XBF_ASYNC)
> > + xfs_buf_ioacct_inc(bp);
> > _xfs_buf_ioapply(bp);
> >
> > /*
> > @@ -1507,14 +1496,39 @@ xfs_buf_submit(
> > * that we don't return to the caller with completion still pending.
> > */
> > if (atomic_dec_and_test(&bp->b_io_remaining) == 1) {
> > - if (bp->b_error)
> > + if (bp->b_error || !(bp->b_flags & XBF_ASYNC))
> > xfs_buf_ioend(bp);
> > else
> > xfs_buf_ioend_async(bp);
> > }
> >
> > - xfs_buf_rele(bp);
> > + return 0;
> > +}
> > +
> > +void
> > +xfs_buf_submit(
> > + struct xfs_buf *bp)
> > +{
> > + int error;
> > +
> > + ASSERT(bp->b_flags & XBF_ASYNC);
> > +
> > + /*
> > + * The caller's reference is released during I/O completion.
> > + * This occurs some time after the last b_io_remaining reference is
> > + * released, so after we drop our Io reference we have to have some
> > + * other reference to ensure the buffer doesn't go away from underneath
> > + * us. Take a direct reference to ensure we have safe access to the
> > + * buffer until we are finished with it.
> > + */
> > + xfs_buf_hold(bp);
> > +
> > + error = __xfs_buf_submit(bp);
> > + if (error)
> > + xfs_buf_ioend(bp);
> > +
>
> It seems like we could simple throw in a:
>
> if (!(bp->b_flags & XBF_ASYNC)) {
> trace_xfs_buf_iowait(bp, _RET_IP_);
> wait_for_completion(&bp->b_iowait);
> trace_xfs_buf_iowait_done(bp, _RET_IP_);
> error = bp->b_error;;
> }
>
> here and get ret rid of the separate xfs_buf_submit_wait function
> entirely. Or even factor the above out into a nice little helper.
>
As you already noted in patch 2, we need this code split up to support
fixing the delwri queue thing..
> Otherwise this looks fine to me:
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Thanks. I assume you mean Reviewed-by... ;)
Brian
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