On Mon, Jan 18, 2021 at 08:39:59AM -0500, Sasha Levin wrote: > On Mon, Jan 18, 2021 at 10:24:33AM +0100, Greg KH wrote: > > On Mon, Jan 18, 2021 at 10:21:16AM +0100, Greg KH wrote: > > > On Sun, Jan 17, 2021 at 08:49:51PM -0500, Sasha Levin wrote: > > > > SUBLEVEL only has 8 bits of space, which means that we'll overflow it > > > > once it reaches 256. > > > > > > > > Few of the stable branches will imminently overflow SUBLEVEL while > > > > there's no risk of overflowing VERSION. > > > > > > > > Thus, give SUBLEVEL 8 more bits which will be stolen from VERSION, this > > > > should create a better balance between the different version numbers we > > > > use. > > > > > > > > The downside here is that Linus will have 8 bits less to play with, but > > > > given our current release cadence (~10 weeks), the number of Linus's > > > > fingers & toes (20), and the current VERSION (5) we can calculate that > > > > VERSION will overflow in just over 1,000 years, so I'm kicking this can > > > > down the road. > > > > > > > > Cc: stable@xxxxxxxxxx > > > > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> > > > > --- > > > > Makefile | 4 ++-- > > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/Makefile b/Makefile > > > > index 9e73f82e0d863..dc2bad7a440d8 100644 > > > > --- a/Makefile > > > > +++ b/Makefile > > > > @@ -1252,8 +1252,8 @@ endef > > > > > > > > define filechk_version.h > > > > echo \#define LINUX_VERSION_CODE $(shell \ > > > > - expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 0$(SUBLEVEL)); \ > > > > - echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))' > > > > + expr $(VERSION) \* 16777216 + 0$(PATCHLEVEL) \* 65536 + 0$(SUBLEVEL)); \ > > > > + echo '#define KERNEL_VERSION(a,b,c) (((a) << 24) + ((b) << 16) + (c))' > > > > > > As much as I agree, this will break in-tree users of LINUX_VERSION_CODE > > > that try to suck out the version/patchlevel number of the kernel release > > > into their own fields. Things like USB host controller strings, v4l > > > ioctl reports, scsi driver ioctls, and other places do fun bit-movements > > > to try to unreverse this bit packing. > > > > > > So how about we just provide a "real" version/subversion/revision > > > #define as well, and clean up all in-kernel users, so we can get this to > > > work, and we can change it in the future more easily. > > > > Or, I can just stop doing stable releases at .255 and then abuse the > > EXTRAVERSION field to put in sub-revision values. > > > > Or, we can just not worry about it as anyone using these really old > > kernels, userspace will work just fine (the number going backwards for > > these fields isn't going to break anything), it's only any crazy > > out-of-tree code that will get confused if they are trying to do > > different build options based on SUBLEVEL :) > > I think it would also affect code that doesn't do things based on > SBULEVEL. Consider something like: > > if (LINUX_VERSION_CODE < KERNEL_VERSION(4,5,0)) > > Which will cause 4.4.256 to now change the result of that comparison. Sure, but there are no in-kernel users like this, so my sympathy is quite low :)
