Re: [PATCH 2/9] xfs: xfs_buf_ioend and xfs_buf_iodone_work duplicate functionality

Brian Foster
2014-08-15T13:18:27Z

On Fri, Aug 15, 2014 at 04:39:00PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> We do some work in xfs_buf_ioend, and some work in
> xfs_buf_iodone_work, but much of that functionality is the same.
> This work can all be done in a single function, leaving
> xfs_buf_iodone just a wrapper to determine if we should execute it
> by workqueue or directly. hence rename xfs_buf_iodone_work to
> xfs_buf_ioend(), and add a new xfs_buf_ioend_async() for places that
> need async processing.
>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
> fs/xfs/xfs_buf.c | 79 +++++++++++++++++++++---------------------------
> fs/xfs/xfs_buf.h | 2 +-
> fs/xfs/xfs_buf_item.c | 4 +--
> fs/xfs/xfs_inode.c | 2 +-
> fs/xfs/xfs_log.c | 2 +-
> fs/xfs/xfs_log_recover.c | 2 +-
> 6 files changed, 40 insertions(+), 51 deletions(-)
>
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index 5d86bbd..1b7f0bc 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -999,54 +999,49 @@ xfs_buf_wait_unpin(
> */
>
> STATIC void
> -xfs_buf_iodone_work(
> - struct work_struct *work)
> +xfs_buf_ioend(
> + struct xfs_buf *bp)

Compile failure here due to STATIC.

> {
> - struct xfs_buf *bp =
> - container_of(work, xfs_buf_t, b_iodone_work);
> - bool read = !!(bp->b_flags & XBF_READ);
> + bool read = !!(bp->b_flags & XBF_READ);
> +
> + trace_xfs_buf_iodone(bp, _RET_IP_);
>
> bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD);
>
> - /* only validate buffers that were read without errors */
> - if (read && bp->b_ops && !bp->b_error && (bp->b_flags & XBF_DONE))
> - bp->b_ops->verify_read(bp);
> + if (!bp->b_error) {
> + bp->b_flags |= XBF_DONE;
> +
> + /* only validate buffers that were read without errors */
> + if (read && bp->b_ops)
> + bp->b_ops->verify_read(bp);
> + }

Probably not a cause of errors, but this code is now executed twice for
I/O with b_iodone callbacks. Once for the initial call from bio_end_io,
again from the callback via the b_iodone handler. The flags bits are
probably fine, but we don't want to be running the verifiers multiple
times unnecessarily.

>
> if (bp->b_iodone)
> (*(bp->b_iodone))(bp);
> else if (bp->b_flags & XBF_ASYNC)
> xfs_buf_relse(bp);
> else {
> - ASSERT(read && bp->b_ops);
> complete(&bp->b_iowait);
> xfs_buf_rele(bp);
> }
> }
>
> -void
> -xfs_buf_ioend(
> - struct xfs_buf *bp,
> - int schedule)
> +static void
> +xfs_buf_ioend_work(
> + struct work_struct *work)
> {
> - bool read = !!(bp->b_flags & XBF_READ);
> -
> - trace_xfs_buf_iodone(bp, _RET_IP_);
> + struct xfs_buf *bp =
> + container_of(work, xfs_buf_t, b_iodone_work);
>
> - if (bp->b_error == 0)
> - bp->b_flags |= XBF_DONE;
> + xfs_buf_ioend(bp);
> +}
>
> - if (bp->b_iodone || (read && bp->b_ops) || (bp->b_flags & XBF_ASYNC)) {
> - if (schedule) {
> - INIT_WORK(&bp->b_iodone_work, xfs_buf_iodone_work);
> - queue_work(xfslogd_workqueue, &bp->b_iodone_work);
> - } else {
> - xfs_buf_iodone_work(&bp->b_iodone_work);
> - }
> - } else {
> - bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD);
> - complete(&bp->b_iowait);
> - xfs_buf_rele(bp);
> - }
> +void
> +xfs_buf_ioend_async(
> + struct xfs_buf *bp)
> +{
> + INIT_WORK(&bp->b_iodone_work, xfs_buf_ioend_work);
> + queue_work(xfslogd_workqueue, &bp->b_iodone_work);
> }
>
> void
> @@ -1094,7 +1089,7 @@ xfs_bioerror(
> XFS_BUF_UNDONE(bp);
> xfs_buf_stale(bp);
>
> - xfs_buf_ioend(bp, 0);
> + xfs_buf_ioend(bp);
>
> return -EIO;
> }
> @@ -1181,15 +1176,6 @@ xfs_bwrite(
> }
>
> STATIC void
> -_xfs_buf_ioend(
> - xfs_buf_t *bp,
> - int schedule)
> -{
> - if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
> - xfs_buf_ioend(bp, schedule);
> -}
> -
> -STATIC void
> xfs_buf_bio_end_io(
> struct bio *bio,
> int error)
> @@ -1206,7 +1192,8 @@ xfs_buf_bio_end_io(
> if (!bp->b_error && xfs_buf_is_vmapped(bp) && (bp->b_flags & XBF_READ))
> invalidate_kernel_vmap_range(bp->b_addr, xfs_buf_vmap_len(bp));
>
> - _xfs_buf_ioend(bp, 1);
> + if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
> + xfs_buf_ioend_async(bp);
> bio_put(bio);
> }
>
> @@ -1425,10 +1412,12 @@ xfs_buf_iorequest(
> * waiting, and in the synchronous IO case it avoids unnecessary context
> * switches an latency for high-peformance devices.
> */
> - if (bp->b_error || !(bp->b_flags & XBF_ASYNC))
> - _xfs_buf_ioend(bp, 0);
> - else
> - _xfs_buf_ioend(bp, 1);
> + if (atomic_dec_and_test(&bp->b_io_remaining) == 1) {
> + if (bp->b_error || !(bp->b_flags & XBF_ASYNC))
> + xfs_buf_ioend(bp);
> + else
> + xfs_buf_ioend_async(bp);
> + }

This looks cleaner, but the comment is out of whack at this point.

Brian

>
> xfs_buf_rele(bp);
> }
> diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
> index c753183..4585c15 100644
> --- a/fs/xfs/xfs_buf.h
> +++ b/fs/xfs/xfs_buf.h
> @@ -286,7 +286,7 @@ extern void xfs_buf_unlock(xfs_buf_t *);
>
> /* Buffer Read and Write Routines */
> extern int xfs_bwrite(struct xfs_buf *bp);
> -extern void xfs_buf_ioend(xfs_buf_t *, int);
> +extern void xfs_buf_ioend(struct xfs_buf *bp);
> extern void xfs_buf_ioerror(xfs_buf_t *, int);
> extern void xfs_buf_ioerror_alert(struct xfs_buf *, const char *func);
> extern void xfs_buf_iorequest(xfs_buf_t *);
> diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
> index 76007de..4fd41b5 100644
> --- a/fs/xfs/xfs_buf_item.c
> +++ b/fs/xfs/xfs_buf_item.c
> @@ -491,7 +491,7 @@ xfs_buf_item_unpin(
> xfs_buf_ioerror(bp, -EIO);
> XFS_BUF_UNDONE(bp);
> xfs_buf_stale(bp);
> - xfs_buf_ioend(bp, 0);
> + xfs_buf_ioend(bp);
> }
> }
>
> @@ -1115,7 +1115,7 @@ do_callbacks:
> xfs_buf_do_callbacks(bp);
> bp->b_fspriv = NULL;
> bp->b_iodone = NULL;
> - xfs_buf_ioend(bp, 0);
> + xfs_buf_ioend(bp);
> }
>
> /*
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index fea3c92..00d210b 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -3056,7 +3056,7 @@ cluster_corrupt_out:
> XFS_BUF_UNDONE(bp);
> xfs_buf_stale(bp);
> xfs_buf_ioerror(bp, -EIO);
> - xfs_buf_ioend(bp, 0);
> + xfs_buf_ioend(bp);
> } else {
> xfs_buf_stale(bp);
> xfs_buf_relse(bp);
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index 8eaa8f5..e4665db 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -1689,7 +1689,7 @@ xlog_bdstrat(
> if (iclog->ic_state & XLOG_STATE_IOERROR) {
> xfs_buf_ioerror(bp, -EIO);
> xfs_buf_stale(bp);
> - xfs_buf_ioend(bp, 0);
> + xfs_buf_ioend(bp);
> /*
> * It would seem logical to return EIO here, but we rely on
> * the log state machine to propagate I/O errors instead of
> diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
> index 1fd5787..4ba19bf 100644
> --- a/fs/xfs/xfs_log_recover.c
> +++ b/fs/xfs/xfs_log_recover.c
> @@ -383,7 +383,7 @@ xlog_recover_iodone(
> SHUTDOWN_META_IO_ERROR);
> }
> bp->b_iodone = NULL;
> - xfs_buf_ioend(bp, 0);
> + xfs_buf_ioend(bp);
> }
>
> /*
> --
> 2.0.0
>
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