On 03/30/2017 09:45 PM, Linus Torvalds wrote: > On Thu, Mar 30, 2017 at 11:26 AM, Christoph Hellwig <hch@xxxxxx> wrote: >> >> That would be nice, but still won't work as we blindly copy f_flags >> into F_GETFL, not even masking our internal FMODE_ bits. > > Ok, *that* is just silly of us, and we could try to just fix, and even backport. > > There's no possible valid use I could see where that should break > (famous last words - user code does some damn odd things at times). > > Of course, that won't fix old kernels that are out there, but then > neither would your original patch... > > Side note: I think you *can* detect the O_ATOMIC support by using > F_SETFL, because F_SETFL only allows you to change flags that we > recognize. So somebody who really wants to *guarantee* that O_ATOMIC > is there and honored even with old kernels could presumable do > something like > > fd = open(..); // *no* O_ATOMIC > fcnt(fd, F_SETFL, O_ATOMIC); > if (fcnt(fd, F_GETFL, NULL) & O_ATOMIC) > // Yay! We actually got it > else > // I guess we need to fall back on old behavior > > although I agree that that is ridiculously inconvenient and not a > great thing, and it's worth trying to aim for some better model. > Perhaps in that case it is time for an F_GETFL2 an F_GET_REAL_FL that gives you the nice simple user code Linus wanted for new applications. and solves forward and backwords for applications and Kernels? Just my $0.017 Boaz > Linus >
