Re: [brauner-vfs:vfs.misc 12/13] include/linux/fs.h:911:9: error: call to '__compiletime_assert_207' declared with 'error' attribute: Need native word sized stores/loads for atomicity.

Baokun Li
2024-01-23T07:08:08Z

On 2024/1/23 8:12, kernel test robot wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git vfs.misc
> head: 297983dc9011461cba6278bfe03f4305c4a2caa0
> commit: 4bbd51d0f0ad709c0f02c100439d6c9ba6811d4b [12/13] fs: make the i_size_read/write helpers be smp_load_acquire/store_release()
> config: i386-randconfig-015-20240123 (https://download.01.org/0day-ci/archive/20240123/202401230837.TXro0PHi-lkp@intel.com/config)
> compiler: ClangBuiltLinux clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240123/202401230837.TXro0PHi-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202401230837.TXro0PHi-lkp@intel.com/
>
> All errors (new ones prefixed by >>):
>
> In file included from fs/netfs/buffered_read.c:10:
> In file included from fs/netfs/internal.h:9:
> In file included from include/linux/seq_file.h:12:
>>> include/linux/fs.h:911:9: error: call to '__compiletime_assert_207' declared with 'error' attribute: Need native word sized stores/loads for atomicity.
> 911 | return smp_load_acquire(&inode->i_size);
> | ^
> include/asm-generic/barrier.h:206:2: note: expanded from macro 'smp_load_acquire'
> 206 | compiletime_assert_atomic_type(*p); \
> | ^
> include/linux/compiler_types.h:438:2: note: expanded from macro 'compiletime_assert_atomic_type'
> 438 | compiletime_assert(__native_word(t), \
> | ^
> include/linux/compiler_types.h:435:2: note: expanded from macro 'compiletime_assert'
> 435 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> | ^
> include/linux/compiler_types.h:423:2: note: expanded from macro '_compiletime_assert'
> 423 | __compiletime_assert(condition, msg, prefix, suffix)
> | ^
> include/linux/compiler_types.h:416:4: note: expanded from macro '__compiletime_assert'
> 416 | prefix ## suffix(); \
> | ^
> <scratch space>:38:1: note: expanded from here
> 38 | __compiletime_assert_207
> | ^
> 1 error generated.
> --
> In file included from fs/netfs/buffered_write.c:9:
>>> include/linux/fs.h:911:9: error: call to '__compiletime_assert_207' declared with 'error' attribute: Need native word sized stores/loads for atomicity.
> 911 | return smp_load_acquire(&inode->i_size);
> | ^
> include/asm-generic/barrier.h:206:2: note: expanded from macro 'smp_load_acquire'
> 206 | compiletime_assert_atomic_type(*p); \
> | ^
> include/linux/compiler_types.h:438:2: note: expanded from macro 'compiletime_assert_atomic_type'
> 438 | compiletime_assert(__native_word(t), \
> | ^
> include/linux/compiler_types.h:435:2: note: expanded from macro 'compiletime_assert'
> 435 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> | ^
> include/linux/compiler_types.h:423:2: note: expanded from macro '_compiletime_assert'
> 423 | __compiletime_assert(condition, msg, prefix, suffix)
> | ^
> include/linux/compiler_types.h:416:4: note: expanded from macro '__compiletime_assert'
> 416 | prefix ## suffix(); \
> | ^
> <scratch space>:253:1: note: expanded from here
> 253 | __compiletime_assert_207
> | ^
> In file included from fs/netfs/buffered_write.c:9:
>>> include/linux/fs.h:911:9: error: call to '__compiletime_assert_207' declared with 'error' attribute: Need native word sized stores/loads for atomicity.
> include/asm-generic/barrier.h:206:2: note: expanded from macro 'smp_load_acquire'
> 206 | compiletime_assert_atomic_type(*p); \
> | ^
> include/linux/compiler_types.h:438:2: note: expanded from macro 'compiletime_assert_atomic_type'
> 438 | compiletime_assert(__native_word(t), \
> | ^
> include/linux/compiler_types.h:435:2: note: expanded from macro 'compiletime_assert'
> 435 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> | ^
> include/linux/compiler_types.h:423:2: note: expanded from macro '_compiletime_assert'
> 423 | __compiletime_assert(condition, msg, prefix, suffix)
> | ^
> include/linux/compiler_types.h:416:4: note: expanded from macro '__compiletime_assert'
> 416 | prefix ## suffix(); \
> | ^
> <scratch space>:253:1: note: expanded from here
> 253 | __compiletime_assert_207
> | ^
> In file included from fs/netfs/buffered_write.c:9:
>>> include/linux/fs.h:911:9: error: call to '__compiletime_assert_207' declared with 'error' attribute: Need native word sized stores/loads for atomicity.
> include/asm-generic/barrier.h:206:2: note: expanded from macro 'smp_load_acquire'
> 206 | compiletime_assert_atomic_type(*p); \
> | ^
> include/linux/compiler_types.h:438:2: note: expanded from macro 'compiletime_assert_atomic_type'
> 438 | compiletime_assert(__native_word(t), \
> | ^
> include/linux/compiler_types.h:435:2: note: expanded from macro 'compiletime_assert'
> 435 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> | ^
> include/linux/compiler_types.h:423:2: note: expanded from macro '_compiletime_assert'
> 423 | __compiletime_assert(condition, msg, prefix, suffix)
> | ^
> include/linux/compiler_types.h:416:4: note: expanded from macro '__compiletime_assert'
> 416 | prefix ## suffix(); \
> | ^
> <scratch space>:253:1: note: expanded from here
> 253 | __compiletime_assert_207
> | ^
> In file included from fs/netfs/buffered_write.c:9:
>>> include/linux/fs.h:911:9: error: call to '__compiletime_assert_207' declared with 'error' attribute: Need native word sized stores/loads for atomicity.
> include/asm-generic/barrier.h:206:2: note: expanded from macro 'smp_load_acquire'
> 206 | compiletime_assert_atomic_type(*p); \
> | ^
> include/linux/compiler_types.h:438:2: note: expanded from macro 'compiletime_assert_atomic_type'
> 438 | compiletime_assert(__native_word(t), \
> | ^
> include/linux/compiler_types.h:435:2: note: expanded from macro 'compiletime_assert'
> 435 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> | ^
> include/linux/compiler_types.h:423:2: note: expanded from macro '_compiletime_assert'
> 423 | __compiletime_assert(condition, msg, prefix, suffix)
> | ^
> include/linux/compiler_types.h:416:4: note: expanded from macro '__compiletime_assert'
> 416 | prefix ## suffix(); \
> | ^
> <scratch space>:253:1: note: expanded from here
> 253 | __compiletime_assert_207
> | ^
> 4 errors generated.
> --
> In file included from fs/netfs/misc.c:8:
> In file included from include/linux/swap.h:9:
> In file included from include/linux/memcontrol.h:13:
> In file included from include/linux/cgroup.h:17:
>>> include/linux/fs.h:911:9: error: call to '__compiletime_assert_207' declared with 'error' attribute: Need native word sized stores/loads for atomicity.
> 911 | return smp_load_acquire(&inode->i_size);
> | ^
> include/asm-generic/barrier.h:206:2: note: expanded from macro 'smp_load_acquire'
> 206 | compiletime_assert_atomic_type(*p); \
> | ^
> include/linux/compiler_types.h:438:2: note: expanded from macro 'compiletime_assert_atomic_type'
> 438 | compiletime_assert(__native_word(t), \
> | ^
> include/linux/compiler_types.h:435:2: note: expanded from macro 'compiletime_assert'
> 435 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> | ^
> include/linux/compiler_types.h:423:2: note: expanded from macro '_compiletime_assert'
> 423 | __compiletime_assert(condition, msg, prefix, suffix)
> | ^
> include/linux/compiler_types.h:416:4: note: expanded from macro '__compiletime_assert'
> 416 | prefix ## suffix(); \
> | ^
> <scratch space>:251:1: note: expanded from here
> 251 | __compiletime_assert_207
> | ^
> 1 error generated.
>
> Kconfig warnings: (for reference only)
> WARNING: unmet direct dependencies detected for DRM_I915_DEBUG_GEM
> Depends on [n]: HAS_IOMEM [=y] && DRM_I915 [=y] && EXPERT [=y] && DRM_I915_WERROR [=n]
> Selected by [y]:
> - DRM_I915_DEBUG [=y] && HAS_IOMEM [=y] && DRM_I915 [=y] && EXPERT [=y] && !COMPILE_TEST [=n]
>
>
> vim +911 include/linux/fs.h
>
> 874
> 875 void filemap_invalidate_lock_two(struct address_space *mapping1,
> 876 struct address_space *mapping2);
> 877 void filemap_invalidate_unlock_two(struct address_space *mapping1,
> 878 struct address_space *mapping2);
> 879
> 880
> 881 /*
> 882 * NOTE: in a 32bit arch with a preemptable kernel and
> 883 * an UP compile the i_size_read/write must be atomic
> 884 * with respect to the local cpu (unlike with preempt disabled),
> 885 * but they don't need to be atomic with respect to other cpus like in
> 886 * true SMP (so they need either to either locally disable irq around
> 887 * the read or for example on x86 they can be still implemented as a
> 888 * cmpxchg8b without the need of the lock prefix). For SMP compiles
> 889 * and 64bit archs it makes no difference if preempt is enabled or not.
> 890 */
> 891 static inline loff_t i_size_read(const struct inode *inode)
> 892 {
> 893 #if BITS_PER_LONG==32 && defined(CONFIG_SMP)
> 894 loff_t i_size;
> 895 unsigned int seq;
> 896
> 897 do {
> 898 seq = read_seqcount_begin(&inode->i_size_seqcount);
> 899 i_size = inode->i_size;
> 900 } while (read_seqcount_retry(&inode->i_size_seqcount, seq));
> 901 return i_size;
> 902 #elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPTION)
> 903 loff_t i_size;
> 904
> 905 preempt_disable();
> 906 i_size = inode->i_size;
> 907 preempt_enable();
> 908 return i_size;
> 909 #else
> 910 /* Pairs with smp_store_release() in i_size_write() */
> > 911 return smp_load_acquire(&inode->i_size);
> 912 #endif
> 913 }
> 914
Sorry to cause this compilation error, I have not encountered this
before when testing compilation with gcc on x86 and arm64.
Is there a special config required for this, or is it just clang that
triggers this compile error?

The compile error seems to be that some architectural implementations
of smp_load_acquire() do not support pointers to long long data
types. Can't think of a good way to avoid this problem, any ideas
from linus and christian?