sysbot reported a splat [1] on __unmap_hugepage_range().
This is because vma_needs_reservation() can return -ENOMEM if
allocate_file_region_entries() fails to allocate the file_region struct for
the reservation.
Check for that and do not call vma_add_reservation() if that is the case,
otherwise region_abort() and region_del() will see that we do not have any
file_regions.
If we detect that vma_needs_reservation() returned -ENOMEM, we clear the
hugetlb_restore_reserve flag as if this reservation was still consumed,
so free_huge_folio() will not increment the resv count.
[1] https://lore.kernel.org/linux-mm/[email protected]/T/#ma5983bc1ab18a54910da83416b3f89f3c7ee43aa
Fixes: df7a6d1f6405 ("mm/hugetlb: restore the reservation if needed")
Reported-and-tested-by: [email protected]
Closes: https://lore.kernel.org/linux-mm/[email protected]/
Signed-off-by: Oscar Salvador <[email protected]>
---
mm/hugetlb.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 6be78e7d4f6e..f35abff8be60 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5768,8 +5768,20 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
* do_exit() will not see it, and will keep the reservation
* forever.
*/
- if (adjust_reservation && vma_needs_reservation(h, vma, address))
- vma_add_reservation(h, vma, address);
+ if (adjust_reservation) {
+ int rc = vma_needs_reservation(h, vma, address);
+
+ if (rc < 0)
+ /* Pressumably allocate_file_region_entries failed
+ * to allocate a file_region struct. Clear
+ * hugetlb_restore_reserve so that global reserve
+ * count will not be incremented by free_huge_folio.
+ * Act as if we consumed the reservation.
+ */
+ folio_clear_hugetlb_restore_reserve(page_folio(page));
+ else if (rc)
+ vma_add_reservation(h, vma, address);
+ }
tlb_remove_page_size(tlb, page, huge_page_size(h));
/*
--
2.45.1
On Tue, May 28, 2024 at 10:53:23PM +0200, Oscar Salvador wrote:
> sysbot reported a splat [1] on __unmap_hugepage_range().
> This is because vma_needs_reservation() can return -ENOMEM if
> allocate_file_region_entries() fails to allocate the file_region struct for
> the reservation.
> Check for that and do not call vma_add_reservation() if that is the case,
> otherwise region_abort() and region_del() will see that we do not have any
> file_regions.
>
> If we detect that vma_needs_reservation() returned -ENOMEM, we clear the
> hugetlb_restore_reserve flag as if this reservation was still consumed,
> so free_huge_folio() will not increment the resv count.
>
> [1] https://lore.kernel.org/linux-mm/[email protected]/T/#ma5983bc1ab18a54910da83416b3f89f3c7ee43aa
>
> Fixes: df7a6d1f6405 ("mm/hugetlb: restore the reservation if needed")
> Reported-and-tested-by: [email protected]
> Closes: https://lore.kernel.org/linux-mm/[email protected]/
> Signed-off-by: Oscar Salvador <[email protected]>
> ---
> mm/hugetlb.c | 16 ++++++++++++++--
> 1 file changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 6be78e7d4f6e..f35abff8be60 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -5768,8 +5768,20 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
> * do_exit() will not see it, and will keep the reservation
> * forever.
> */
> - if (adjust_reservation && vma_needs_reservation(h, vma, address))
> - vma_add_reservation(h, vma, address);
> + if (adjust_reservation) {
> + int rc = vma_needs_reservation(h, vma, address);
vma_needs_reservation returns a long.
static long vma_needs_reservation(struct hstate *h,
struct vm_area_struct *vma, unsigned long addr)
Other than that, this is reviewed.
Reviewed-by: Breno Leitao <[email protected]>
Thanks for fixing it.
On Wed, May 29, 2024 at 08:43:06AM -0700, Breno Leitao wrote:
> vma_needs_reservation returns a long.
>
> static long vma_needs_reservation(struct hstate *h,
> struct vm_area_struct *vma, unsigned long addr)
Yeah, I missed that, thanks.
@Andrew: Can you fold the following in? Thanks
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index f35abff8be60..0b9e64aa279b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5769,7 +5769,7 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
* forever.
*/
if (adjust_reservation) {
- int rc = vma_needs_reservation(h, vma, address);
+ long rc = vma_needs_reservation(h, vma, address);
if (rc < 0)
/* Pressumably allocate_file_region_entries failed
> Reviewed-by: Breno Leitao <[email protected]>
Thanks
--
Oscar Salvador
SUSE Labs