On 2/6/22 20:26, Alistair Popple wrote:
migrate_vma_setup() checks that a valid vma is passed so that the page
tables can be walked to find the pfns associated with a given address
range. However in some cases the pfns are already known, such as when
migrating device coherent pages during pin_user_pages() meaning a valid
vma isn't required.
Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>
Acked-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>
---
Changes for v2:
- Added Felix's Acked-by
mm/migrate.c | 34 +++++++++++++++++-----------------
1 file changed, 17 insertions(+), 17 deletions(-)
Hi Alistair,
Another late-breaking review question, below. :)
diff --git a/mm/migrate.c b/mm/migrate.c
index a9aed12..0d6570d 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2602,24 +2602,24 @@ int migrate_vma_setup(struct migrate_vma *args)
args->start &= PAGE_MASK;
args->end &= PAGE_MASK;
- if (!args->vma || is_vm_hugetlb_page(args->vma) ||
- (args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma))
- return -EINVAL;
- if (nr_pages <= 0)
- return -EINVAL;
Was the above check left out intentionally? If so, then it needs a
commit description note. And maybe even a separate patch, because it
changes the behavior.
If you do want to change the behavior:
* The kerneldoc comment above this function supports such a change: it
requires returning 0 for the case of zero pages requested. So your
change would bring the comments into alignment with the code.
* I don't think memset deals properly with a zero length input arg, so
it's probably better to return 0, before that point.
thanks,
--
John Hubbard
NVIDIA
- if (args->start < args->vma->vm_start ||
- args->start >= args->vma->vm_end)
- return -EINVAL;
- if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end)
- return -EINVAL;
if (!args->src || !args->dst)
return -EINVAL;
-
- memset(args->src, 0, sizeof(*args->src) * nr_pages);
- args->cpages = 0;
- args->npages = 0;
-
- migrate_vma_collect(args);
+ if (args->vma) {
+ if (is_vm_hugetlb_page(args->vma) ||
+ (args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma))
+ return -EINVAL;
+ if (args->start < args->vma->vm_start ||
+ args->start >= args->vma->vm_end)
+ return -EINVAL;
+ if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end)
+ return -EINVAL;
+
+ memset(args->src, 0, sizeof(*args->src) * nr_pages);
+ args->cpages = 0;
+ args->npages = 0;
+
+ migrate_vma_collect(args);
+ }
if (args->cpages)
migrate_vma_unmap(args);
@@ -2804,7 +2804,7 @@ void migrate_vma_pages(struct migrate_vma *migrate)
continue;
}
- if (!page) {
+ if (!page && migrate->vma) {
if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE))
continue;
if (!notified) {
