| Message ID | 20190523023141.2973-1-cai@lca.pw (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | powerpc/powernv: fix variable "c" set but not used | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch next (8150a153c013aa2dd1ffae43370b89ac1347a7fb) |
| snowpatch_ozlabs/build-ppc64le | fail | Test build-ppc64le on branch next |
| snowpatch_ozlabs/build-ppc64be | fail | Test build-ppc64be on branch next |
| snowpatch_ozlabs/build-ppc64e | fail | Test build-ppc64e on branch next |
| snowpatch_ozlabs/build-pmac32 | fail | Test build-pmac32 on branch next |
| snowpatch_ozlabs/checkpatch | fail | Test checkpatch on branch next |
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch next (8150a153c013aa2dd1ffae43370b89ac1347a7fb) |
| snowpatch_ozlabs/build-ppc64le | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64be | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64e | success | Build succeeded |
| snowpatch_ozlabs/build-pmac32 | success | Build succeeded |
| snowpatch_ozlabs/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 9 lines checked |
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 <cai@lca.pw> 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; >
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.
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;
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 <cai@lca.pw> --- arch/powerpc/platforms/powernv/npu-dma.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)