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Commit eaebb515 authored by Brian Foster's avatar Brian Foster Committed by Darrick J. Wong
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xfs: refactor buffer submission into a common helper 



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: default avatarDave Chinner <dchinner@redhat.com>
Signed-off-by: default avatarBrian Foster <bfoster@redhat.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
parent 5fdd9794

fs/xfs/xfs_buf.c

+37 −48
Original line number Diff line number Diff line
@@ -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)
@@ -1482,22 +1480,13 @@ 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);

	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);



	/* Note: it is not safe to reference bp now we've dropped our ref */

	xfs_buf_rele(bp);

}



/*
@@ -1526,22 +1540,7 @@ xfs_buf_submit_wait( 
{

	int		error;



	trace_xfs_buf_submit_wait(bp, _RET_IP_);



	ASSERT(!(bp->b_flags & (_XBF_DELWRI_Q | XBF_ASYNC)));



	if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {

		xfs_buf_ioerror(bp, -EIO);

		xfs_buf_stale(bp);

		bp->b_flags &= ~XBF_DONE;

		return -EIO;

	}



	if (bp->b_flags & XBF_WRITE)

		xfs_buf_wait_unpin(bp);



	/* clear the internal error state to avoid spurious errors */

	bp->b_io_error = 0;

	ASSERT(!(bp->b_flags & XBF_ASYNC));



	/*

	 * For synchronous IO, the IO does not inherit the submitters reference
@@ -1551,20 +1550,9 @@ xfs_buf_submit_wait( 
	 */

	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_ioapply(bp);



	/*

	 * make sure we run completion synchronously if it raced with us and is

	 * already complete.

	 */

	if (atomic_dec_and_test(&bp->b_io_remaining) == 1)

		xfs_buf_ioend(bp);

	error = __xfs_buf_submit(bp);

	if (error)

		goto out;



	/* wait for completion before gathering the error from the buffer */

	trace_xfs_buf_iowait(bp, _RET_IP_);
@@ -1572,6 +1560,7 @@ xfs_buf_submit_wait( 
	trace_xfs_buf_iowait_done(bp, _RET_IP_);

	error = bp->b_error;



out:

	/*

	 * all done now, we can release the hold that keeps the buffer

	 * referenced for the entire IO.

fs/xfs/xfs_trace.h

+0 −1
Original line number Diff line number Diff line
@@ -310,7 +310,6 @@ DEFINE_BUF_EVENT(xfs_buf_hold); 
DEFINE_BUF_EVENT(xfs_buf_rele);

DEFINE_BUF_EVENT(xfs_buf_iodone);

DEFINE_BUF_EVENT(xfs_buf_submit);

DEFINE_BUF_EVENT(xfs_buf_submit_wait);

DEFINE_BUF_EVENT(xfs_buf_lock);

DEFINE_BUF_EVENT(xfs_buf_lock_done);

DEFINE_BUF_EVENT(xfs_buf_trylock_fail);