Re: [PATCH 12/12] iomap: add tracing for the address space operations
On Tue, Jun 25, 2019 at 12:15:15PM +0200, Christoph Hellwig wrote: > On Tue, Jun 25, 2019 at 09:49:21AM +1000, Dave Chinner wrote: > > > +#undef TRACE_SYSTEM > > > +#define TRACE_SYSTEM iomap > > > > Can you add a comment somewhere here that says these tracepoints are > > volatile and we reserve the right to change them at any time so they > > don't form any sort of persistent UAPI that we have to maintain? > > Sure. Note that we don't have any such comment in xfs either.. Yes, but that is buries inside the xfs code where we largely set our own rules. This, however, is generic code where people have a habit of arguing that tracepoints are stable API and they can never be changed because some random userspace application may have hard coded a dependency on it... Hence we need to be explicit here that this is diagnostic/debug code and anyone who tries to rely on it as a stable API gets to keep all the broken bits to themselves. Cheers, Dave. -- Dave Chinner da...@fromorbit.com
Re: [PATCH 12/12] iomap: add tracing for the address space operations
On Tue, Jun 25, 2019 at 12:15:15PM +0200, Christoph Hellwig wrote: > On Tue, Jun 25, 2019 at 09:49:21AM +1000, Dave Chinner wrote: > > > +#undef TRACE_SYSTEM > > > +#define TRACE_SYSTEM iomap > > > > Can you add a comment somewhere here that says these tracepoints are > > volatile and we reserve the right to change them at any time so they > > don't form any sort of persistent UAPI that we have to maintain? > > Sure. Note that we don't have any such comment in xfs either.. I think we ought to add a comment to both of the tracepoint header files in xfs then... --D
Re: [PATCH 12/12] iomap: add tracing for the address space operations
On Tue, Jun 25, 2019 at 09:49:21AM +1000, Dave Chinner wrote: > > +#undef TRACE_SYSTEM > > +#define TRACE_SYSTEM iomap > > Can you add a comment somewhere here that says these tracepoints are > volatile and we reserve the right to change them at any time so they > don't form any sort of persistent UAPI that we have to maintain? Sure. Note that we don't have any such comment in xfs either..
Re: [PATCH 12/12] iomap: add tracing for the address space operations
On Mon, Jun 24, 2019 at 07:52:53AM +0200, Christoph Hellwig wrote: > Lift the xfs code for tracing address space operations to the iomap > layer. > > Signed-off-by: Christoph Hellwig > diff --git a/include/trace/events/iomap.h b/include/trace/events/iomap.h > new file mode 100644 > index ..da50ece663f8 > --- /dev/null > +++ b/include/trace/events/iomap.h > @@ -0,0 +1,82 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright (c) 2009-2019, Christoph Hellwig > + * All Rights Reserved. > + */ > +#undef TRACE_SYSTEM > +#define TRACE_SYSTEM iomap Can you add a comment somewhere here that says these tracepoints are volatile and we reserve the right to change them at any time so they don't form any sort of persistent UAPI that we have to maintain? -Dave. -- Dave Chinner da...@fromorbit.com
