Re: [PATCH] powerpc/powernv: fix variable "c" set but not used
On Thu, May 23, 2019 at 09:26:53AM +0200, Christophe Leroy wrote: > You are not fixing the problem, you are just hiding it. > > If the result of __get_user() is unneeded, it means __get_user() is not the > good function to use. > > Should use fault_in_pages_readable() instead. Also it is not just the variable that is unused, but that whole function. I'll resend my series to remote it in a bit.
Re: [PATCH] powerpc/powernv: fix variable "c" set but not used
Le 23/05/2019 à 04:31, Qian Cai a écrit : The commit 58629c0dc349 ("powerpc/powernv/npu: Fault user page into the hypervisor's pagetable") introduced a variable "c" to be used in __get_user() and __get_user_nocheck() which need to stay as macros for performance reasons, and "c" is not actually used in pnv_npu2_handle_fault(), arch/powerpc/platforms/powernv/npu-dma.c: In function 'pnv_npu2_handle_fault': arch/powerpc/platforms/powernv/npu-dma.c:1122:7: warning: variable 'c' set but not used [-Wunused-but-set-variable] Fixed it by appending the __maybe_unused attribute, so compilers would ignore it. You are not fixing the problem, you are just hiding it. If the result of __get_user() is unneeded, it means __get_user() is not the good function to use. Should use fault_in_pages_readable() instead. A similar warning was fixed in commit 9f9eae5ce717 ("powerpc/kvm: Prefer fault_in_pages_readable function") See https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/powerpc?id=9f9eae5ce Signed-off-by: Qian Cai You should add a Fixes: tag 58629c0dc349 ("powerpc/powernv/npu: Fault user page into the hypervisor's pagetable") Christophe --- arch/powerpc/platforms/powernv/npu-dma.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/platforms/powernv/npu-dma.c b/arch/powerpc/platforms/powernv/npu-dma.c index 495550432f3d..5bbe59573ee6 100644 --- a/arch/powerpc/platforms/powernv/npu-dma.c +++ b/arch/powerpc/platforms/powernv/npu-dma.c @@ -1119,7 +1119,8 @@ int pnv_npu2_handle_fault(struct npu_context *context, uintptr_t *ea, int i, is_write; struct page *page[1]; const char __user *u; - char c; + /* To silence a -Wunused-but-set-variable warning. */ + char c __maybe_unused; /* mmap_sem should be held so the struct_mm must be present */ struct mm_struct *mm = context->mm;
[PATCH] powerpc/powernv: fix variable "c" set but not used
The commit 58629c0dc349 ("powerpc/powernv/npu: Fault user page into the hypervisor's pagetable") introduced a variable "c" to be used in __get_user() and __get_user_nocheck() which need to stay as macros for performance reasons, and "c" is not actually used in pnv_npu2_handle_fault(), arch/powerpc/platforms/powernv/npu-dma.c: In function 'pnv_npu2_handle_fault': arch/powerpc/platforms/powernv/npu-dma.c:1122:7: warning: variable 'c' set but not used [-Wunused-but-set-variable] Fixed it by appending the __maybe_unused attribute, so compilers would ignore it. Signed-off-by: Qian Cai --- arch/powerpc/platforms/powernv/npu-dma.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/platforms/powernv/npu-dma.c b/arch/powerpc/platforms/powernv/npu-dma.c index 495550432f3d..5bbe59573ee6 100644 --- a/arch/powerpc/platforms/powernv/npu-dma.c +++ b/arch/powerpc/platforms/powernv/npu-dma.c @@ -1119,7 +1119,8 @@ int pnv_npu2_handle_fault(struct npu_context *context, uintptr_t *ea, int i, is_write; struct page *page[1]; const char __user *u; - char c; + /* To silence a -Wunused-but-set-variable warning. */ + char c __maybe_unused; /* mmap_sem should be held so the struct_mm must be present */ struct mm_struct *mm = context->mm; -- 2.20.1 (Apple Git-117)