On Thu, Apr 27, 2023 at 07:20:55PM -0700, Darrick J. Wong wrote: > On Fri, Apr 28, 2023 at 12:13:46PM +1000, Dave Chinner wrote: > > On Thu, Apr 27, 2023 at 03:49:16PM -0700, Darrick J. Wong wrote: > > > From: Darrick J. Wong <djwong@xxxxxxxxxx> > > > > > > For an unshare request, we only have to take action if the data fork has > > > a shared mapping. We don't care if someone else set up a cow operation. > > > If we find nothing in the data fork, return a hole to avoid allocating > > > space. > > > > > > Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx> > > > --- > > > fs/xfs/xfs_iomap.c | 5 +++-- > > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > Looks ok, but I'm unsure of what bad behaviour this might be fixing. > > Did you just notice this, or does it fix some kind of test failure? > > I noticed it while I was running the freespace defrag code in djwong-dev > with tracepoints turned on. THere was a math bug that I was trying to > sort out that resulted in FUNSHARE being called on a hole, and I was > surprised that it would create a delalloc reservation and then convert > it to an unwritten extent instead of going straight to an unwritten > extent. > > AFAICT it has no user visible effect other than not wasting cycles on > pointless work. Ok. If you add that to the commit message, then consider it Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx> -- Dave Chinner david@xxxxxxxxxxxxx
