On Thu, Oct 22, 2020 at 12:39:14AM +0100, Al Viro wrote: > On Wed, Oct 21, 2020 at 06:13:01PM +0200, Greg KH wrote: > > On Fri, Sep 25, 2020 at 06:51:39AM +0200, Christoph Hellwig wrote: > > > From: David Laight <David.Laight@xxxxxxxxxx> > > > > > > This lets the compiler inline it into import_iovec() generating > > > much better code. > > > > > > Signed-off-by: David Laight <david.laight@xxxxxxxxxx> > > > Signed-off-by: Christoph Hellwig <hch@xxxxxx> > > > --- > > > fs/read_write.c | 179 ------------------------------------------------ > > > lib/iov_iter.c | 176 +++++++++++++++++++++++++++++++++++++++++++++++ > > > 2 files changed, 176 insertions(+), 179 deletions(-) > > > > Strangely, this commit causes a regression in Linus's tree right now. > > > > I can't really figure out what the regression is, only that this commit > > triggers a "large Android system binary" from working properly. There's > > no kernel log messages anywhere, and I don't have any way to strace the > > thing in the testing framework, so any hints that people can provide > > would be most appreciated. > > It's a pure move - modulo changed line breaks in the argument lists > the functions involved are identical before and after that (just checked > that directly, by checking out the trees before and after, extracting two > functions in question from fs/read_write.c and lib/iov_iter.c (before and > after, resp.) and checking the diff between those. > > How certain is your bisection? The bisection is very reproducable. But, this looks now to be a compiler bug. I'm using the latest version of clang and if I put "noinline" at the front of the function, everything works. Nick, any ideas here as to who I should report this to? I'll work on a fixup patch for the Android kernel tree to see if I can work around it there, but others will hit this in Linus's tree sooner or later... thanks, greg k-h
