powerpc: Add __must_check to set_memory_...()

After the following powerpc commits, all calls to set_memory_...()
functions check returned value.
- Commit 8f17bd2f4196 ("powerpc: Handle error in mark_rodata_ro() and
mark_initmem_nx()")
- Commit f7f18e30b468 ("powerpc/kprobes: Handle error returned by
set_memory_rox()")
- Commit 009cf11d4aab ("powerpc: Don't ignore errors from
set_memory_{n}p() in __kernel_map_pages()")
- Commit 9cbacb834b4a ("powerpc: Don't ignore errors from
set_memory_{n}p() in __kernel_map_pages()")
- Commit 78cb0945f714 ("powerpc: Handle error in mark_rodata_ro() and
mark_initmem_nx()")

All calls in core parts of the kernel also always check returned value,
can be looked at with following query:

$ git grep -w -e set_memory_ro -e set_memory_rw -e set_memory_x -e set_memory_nx -e set_memory_rox `find . -maxdepth 1 -type d | grep -v arch | grep /`

It is now possible to flag those functions with __must_check to make
sure no new unchecked call it added.

Link: https://github.com/KSPP/linux/issues/7
Signed-off-by: Christophe Leroy <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://patch.msgid.link/775dae48[e-mail]

arch/powerpc/include/asm/set_memory.h

···
 
 int change_memory_attr(unsigned long addr, int numpages, long action);
 
-static inline int set_memory_ro(unsigned long addr, int numpages)
+static inline int __must_check set_memory_ro(unsigned long addr, int numpages)
 {
 	return change_memory_attr(addr, numpages, SET_MEMORY_RO);
 }
 
-static inline int set_memory_rw(unsigned long addr, int numpages)
+static inline int __must_check set_memory_rw(unsigned long addr, int numpages)
 {
 	return change_memory_attr(addr, numpages, SET_MEMORY_RW);
 }
 
-static inline int set_memory_nx(unsigned long addr, int numpages)
+static inline int __must_check set_memory_nx(unsigned long addr, int numpages)
 {
 	return change_memory_attr(addr, numpages, SET_MEMORY_NX);
 }
 
-static inline int set_memory_x(unsigned long addr, int numpages)
+static inline int __must_check set_memory_x(unsigned long addr, int numpages)
 {
 	return change_memory_attr(addr, numpages, SET_MEMORY_X);
 }
 
-static inline int set_memory_np(unsigned long addr, int numpages)
+static inline int __must_check set_memory_np(unsigned long addr, int numpages)
 {
 	return change_memory_attr(addr, numpages, SET_MEMORY_NP);
 }
 
-static inline int set_memory_p(unsigned long addr, int numpages)
+static inline int __must_check set_memory_p(unsigned long addr, int numpages)
 {
 	return change_memory_attr(addr, numpages, SET_MEMORY_P);
 }
 
-static inline int set_memory_rox(unsigned long addr, int numpages)
+static inline int __must_check set_memory_rox(unsigned long addr, int numpages)
 {
 	return change_memory_attr(addr, numpages, SET_MEMORY_ROX);
 }