On 06/03/25 1:48 pm, Lorenzo Stoakes wrote:
On Thu, Mar 06, 2025 at 12:00:37PM +0530, Dev Jain wrote:
We already are registering private-anon VMAs with khugepaged during fault
time, in do_huge_pmd_anonymous_page(). Commit "register suitable readonly
file vmas for khugepaged" moved the khugepaged registration logic from
shmem_mmap to the generic mmap path. Make this logic specific for non-anon
mappings.
This does sound reasonable, thanks! Though does need to be expanded as
Andrew says for user-visible effects just to be crystal clear.
Sure.
Fixes: 613bec092fe7 ("mm: mmap: register suitable readonly file vmas for khugepaged")
Signed-off-by: Dev Jain <dev.jain@xxxxxxx>
---
mm/vma.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/vma.c b/mm/vma.c
index af1d549b179c..730a26bf14a5 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -2377,7 +2377,8 @@ static int __mmap_new_vma(struct mmap_state *map, struct vm_area_struct **vmap)
* vma_merge_new_range() calls khugepaged_enter_vma() too, the below
* call covers the non-merge case.
*/
- khugepaged_enter_vma(vma, map->flags);
+ if (!vma_is_anonymous(vma))
+ khugepaged_enter_vma(vma, map->flags);
This really needs a comment :) as a Joe Bloggs coder coming to this my
immediate thought would be 'huh? Why?'
Something like:
/* Just added so khugepaged has nothing to do. We call again on fault. */
Would be great.
Thanks!
Sure.
BTW does this patch merit a CC:stable? I am not aware of the general
practice but I am not sure if this is a *serious bug*, as per
submitting-patches.rst.
ksm_add_vma(vma);
*vmap = vma;
return 0;
--
2.30.2
