2023-04-03 11:16:31

by Steven Price

Subject: [PATCH] smaps: Fix defined but not used smaps_shmem_walk_ops

When !CONFIG_SHMEM smaps_shmem_walk_ops is defined but not used,
triggering a compiler warning. Surround the definition with an #ifdef to
keep the compiler happy.

Fixes: 7b86ac3371b7 ("pagewalk: separate function pointers from iterator data")
Reported-by: kernel test robot <[email protected]>
Link: https://lore.kernel.org/oe-kbuild-all/[email protected]/
Signed-off-by: Steven Price <[email protected]>
---
fs/proc/task_mmu.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 6a96e1713fd5..3d4f8859dac1 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -761,11 +761,13 @@ static const struct mm_walk_ops smaps_walk_ops = {
.hugetlb_entry = smaps_hugetlb_range,
};

+#ifdef CONFIG_SHMEM
static const struct mm_walk_ops smaps_shmem_walk_ops = {
.pmd_entry = smaps_pte_range,
.hugetlb_entry = smaps_hugetlb_range,
.pte_hole = smaps_pte_hole,
};
+#endif

/*
* Gather mem stats from @vma with the indicated beginning
--
2.34.1

2023-04-03 15:24:19

by Jason Gunthorpe

Subject: Re: [PATCH] smaps: Fix defined but not used smaps_shmem_walk_ops

On Mon, Apr 03, 2023 at 12:12:55PM +0100, Steven Price wrote:
> When !CONFIG_SHMEM smaps_shmem_walk_ops is defined but not used,
> triggering a compiler warning. Surround the definition with an #ifdef to
> keep the compiler happy.
>
> Fixes: 7b86ac3371b7 ("pagewalk: separate function pointers from iterator data")
> Reported-by: kernel test robot <[email protected]>
> Link: https://lore.kernel.org/oe-kbuild-all/[email protected]/
> Signed-off-by: Steven Price <[email protected]>
> ---
> fs/proc/task_mmu.c | 2 ++
> 1 file changed, 2 insertions(+)

I think it would be better to enclose the definition of
shmem_swap_usage() in its header with a stub like shmem_mapping and
remove the ifdef completely. shmem_mapping() is already compile time
false.

#ifdef CONFIG_SHMEM
if (vma->vm_file && shmem_mapping(vma->vm_file->f_mapping)) {
/*
* For shared or readonly shmem mappings we know that all
* swapped out pages belong to the shmem object, and we can
* obtain the swap value much more efficiently. For private
* writable mappings, we might have COW pages that are
* not affected by the parent swapped out pages of the shmem
* object, so we have to distinguish them during the page walk.
* Unless we know that the shmem object (or the part mapped by
* our VMA) has no swapped out pages at all.
*/
unsigned long shmem_swapped = shmem_swap_usage(vma);

if (!start && (!shmem_swapped || (vma->vm_flags & VM_SHARED) ||
!(vma->vm_flags & VM_WRITE))) {
mss->swap += shmem_swapped;
} else {
ops = &smaps_shmem_walk_ops;
}
}
#endif


Jason