Re: [PATCH v3 23/40] mm/mlock: clear VMA_LOCKED_MASK over mmap callback

On Thu, Oct 01, 2026 at 11:20:17AM -0400, Zi Yan wrote:

On Thu Sep 17, 2026 at 12:22 PM EDT, Lorenzo Stoakes (ARM) wrote:

quoted

Currently there's a confusing mess around VMA_LOCKED_BIT and
VMA_LOCKONFAULT_BIT.

It is permitted for drivers to set any flags they like, with the VMA
already possessing lock flags.

This results in the absurd situation of a VMA possessing both
VMA_SPECIAL_FLAGS and VMA_LOCKED_MASK flags, which is not permitted.

This has resulted in mlock_vma_folio() having a very silly check for this
scenario to work around it.

There is no need for this - just clear the flags before invoking the hook
and reinstate them afterwards if they are required.

Nothing relies upon this being set during the mmap operation.

mmap_prepare is unaffected by this so requires no fix.

Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
---
 mm/internal.h |  9 +--------
 mm/vma.c      | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 8 deletions(-)

<snip>

quoted

+	/* If VMA flags still valid for locked mask, reinstate. */
+	if (vma_supports_mlock(vma)) {
+		const vma_flags_t mask =
+			vma_flags_and_mask(&map->vma_flags,
+					   VMA_LOCKED_MASK);
+
+		vma_set_flags_mask(vma, mask);

It took me a while to figure out vma_set_flags_mask() is an OR
operation.

Yeah naming is hard :)

Let me add a comment here though because it's kinda a bit unusual.

quoted

+	}
+
 	map->vma_flags = vma->flags;

 	return 0;

Otherwise, LGTM.

Reviewed-by: Zi Yan <ziy@nvidia.com>

Thanks!

--
Best Regards,
Yan, Zi

--
Cheers, Lorenzo