On Tue, Oct 25, 2016 at 12:22:47AM +0200, Arnd Bergmann wrote: > On Monday, October 24, 2016 12:30:47 PM CEST Chris Metcalf wrote: > > On 10/21/2016 4:33 PM, Yury Norov wrote: > > > All new 32-bit architectures should have 64-bit off_t type, but existing > > > architectures has 32-bit ones. > > > > > > [...] > > > For syscalls sys_openat() and sys_open_by_handle_at() force_o_largefile() > > > is called, to set O_LARGEFILE flag, and this is the only difference > > > comparing to compat versions. All compat ABIs are already turned to use > > > 64-bit off_t, except tile. So, compat versions for this syscalls are not > > > needed anymore. Tile is handled explicitly. > > > > > > [...] > > > --- a/arch/tile/kernel/compat.c > > > +++ b/arch/tile/kernel/compat.c > > > @@ -103,6 +103,9 @@ COMPAT_SYSCALL_DEFINE5(llseek, unsigned int, fd, unsigned int, offset_high, > > > #define compat_sys_readahead sys32_readahead > > > #define sys_llseek compat_sys_llseek > > > > > > +#define sys_openat compat_sys_openat > > > +#define sys_open_by_handle_at compat_sys_open_by_handle_at > > > + > > > /* Call the assembly trampolines where necessary. */ > > > #define compat_sys_rt_sigreturn _compat_sys_rt_sigreturn > > > #define sys_clone _sys_clone > > > > This patch accomplishes two goals that could be completely separated. > > It's confusing to have them mixed in the same patch without any > > discussion of why they are in the same patch. > > > > First, you want to modify the default <asm/unistd.h> behavior for > > compat syscalls so that the default is sys_openat (etc) rather than > > the existing compat_sys_openat, and then use that new behavior for > > arm64 ILP32. This lets you force O_LARGEFILE for arm64 ILP32 to > > support having a 64-bit off_t at all times. To do that, you fix the > > asm-generic header, and then make tile have a special override. > > This seems reasonable enough. > > > > Second, you introduce ARCH_32BIT_OFF_T basically as a synonym for > > "BITS_PER_WORD == 32", so that new 32-bit architectures can choose not > > to enable it. This is fine in the abstract, but I'm a bit troubled by > > the fact that you are not actually introducing a new 32-bit > > architecture here (just a new 32-bit mode for the arm 64-bit kernel). > > Shouldn't this part of the change wait until someone actually has a > > new 32-bit kernel to drive this forward? > > I asked for this specifically because we identified the problem > during the review of the aarch64 ilp32 code, and it might not > be noticed in the next architecture submission. > > The most important aspect from my perspective is that the new > ilp32 ABI on aarch64 behaves the same way that any native 32-bit > architecture does, and when we change the default, it should > be done for both compat mode and native mode at the same time. > > > If you want to push forward the ARCH_32BIT_OFF_T change in the absence > > of an architecture that supports it, I would think it would be a lot > > less confusing to have these two in separate patches, and make it > > clear that the ARCH_32BIT_OFF_T change is just laying groundwork > > for some hypothetical future architecture. > > > > The existing commit language itself is also confusing. You write "All > > compat ABIs are already turned to use 64-bit off_t, except tile." > > First, I'm not sure what you mean by "turned" here. And, tile is just > > one of many compat ABIs that allow O_LARGEFILE not to be part of the > > open call: see arm64's AArch32 ABI, MIPS o32, s390 31-bit emulation, > > sparc64's 32-bit mode, and of course x86's 32-bit compat mode. > > Presumably your point here is that tile is the only pre-existing > > architecture that #includes <asm/unistd.h> to create its compat > > syscall table, and so I think "all except tile" here is particularly > > confusing, since there are no architectures except tile that use the > > __SYSCALL_COMPAT functionality in the current tree. > > Agreed, this could be made clearer, and splitting the patch up > in two also seems reasonable, though I didn't see it as important. > > Arnd In the past it was a separated series of 2 patches, and it was even acked by Arnd, but not submitted. http://lists-archives.com/linux-kernel/28471253-32-bit-abi-introduce-arch_32bit_off_t-config-option.html I can restore that small series in aarch64/ilp32 for next iteration, or resend it separately if you think to submit it before aarch64/ilp32 (which is better, for me). Yury -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
