On 2022-05-29 23:59, Christoph Hellwig wrote: > On Thu, May 26, 2022 at 10:35:59AM -0600, Logan Gunthorpe wrote: >> Move struct r5l_log definition to raid5-log.h. While this reduces >> encapsulation, it is necessary for the definition of r5l_log to be >> public so that rcu_access_pointer() can be used on conf-log in the >> next patch. >> >> rcu_access_pointer(p) doesn't technically dereference the log pointer >> however, it does use typeof(*p) and some older GCC versions (anything >> earlier than gcc-10) will wrongly try to dereference the structure: >> >> include/linux/rcupdate.h:384:9: error: dereferencing pointer to >> incomplete type ‘struct r5l_log’ >> >> typeof(*p) *local = (typeof(*p) *__force)READ_ONCE(p); \ >> ^ >> >> include/linux/rcupdate.h:495:31: note: in expansion of >> macro ‘__rcu_access_pointer’ >> >> #define rcu_access_pointer(p) __rcu_access_pointer((p), >> __UNIQUE_ID(rcu), __rcu) >> >> To prevent this, simply provide the definition where >> rcu_access_pointer() may be used. > > What about just moving any code that does the rcu_access_pointer on > conf->log to raid5-cache.c and doing an out of line call for it > instead? I guess we could do that. All the inline functions in raid5-log.h are there to choose between the r5l or the ppl implementaiton. So it that would mean the r5l implementation would probably be inlined and ppl would be doing a second out of line call. Not sure if that matters, but it seems a little odd. Logan
