On 2024/1/24 21:27, Christian Brauner wrote:
If CONFIG_SMP is not enabled in include/asm-generic/barrier.h,
then smp_load_acquire/smp_store_release is implemented as
READ_ONCE/READ_ONCE and barrier() and type checking.
READ_ONCE/READ_ONCE already checks the pointer type,
but then checks it more stringently outside, but here the
more stringent checking seems unnecessary, so it is removed
and only the type checking in READ_ONCE/READ_ONCE is kept
to avoid compilation errors.
Maha, brainfart on my end, I missed the !CONFIG_SMP case.
Sorry about that.
Never mind. 😊
When CONFIG_SMP is enabled on 32-bit architectures,
smp_load_acquire/smp_store_release is not called in i_size_read/write,
so there is no compilation problem. On 64-bit architectures, there
is no compilation problem because sizeof(long long) == sizeof(long),
regardless of whether CONFIG_SMP is enabled or not.
Yes, of course.
Yes, using smp_rmb()/smp_wmb() would also solve the problem, but
the initial purpose of this patch was to replace smp_rmb() in filemap_read()
with the clearer smp_load_acquire/smp_store_release, and that's where
the community is going with this evolution. Later on, buffer and page/folio
will also switch to acquire/release, which is why I think Linus' suggestion
is better.
Ah ok, thanks for the context. Can you send an updated series then, please?
No problem, I'll send a new version soon!
Cheers!
--
With Best Regards,
Baokun Li
.
