On Mon, May 30, 2022 at 8:48 AM Logan Gunthorpe <logang@xxxxxxxxxxxx> wrote: > > > > 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. I like the current version better. raid5-log.h is not used in many files anyway. Thanks, Song
