On Mon, Jun 05, 2023 at 10:41:12AM -0700, Peter Collingbourne wrote:
On Mon, Jun 5, 2023 at 7:06 AM Will Deacon will@kernel.org wrote:
On Mon, May 22, 2023 at 05:43:08PM -0700, Peter Collingbourne wrote:
Commit c145e0b47c77 ("mm: streamline COW logic in do_swap_page()") moved the call to swap_free() before the call to set_pte_at(), which meant that the MTE tags could end up being freed before set_pte_at() had a chance to restore them. Fix it by adding a call to the arch_swap_restore() hook before the call to swap_free().
Signed-off-by: Peter Collingbourne pcc@google.com Link: https://linux-review.googlesource.com/id/I6470efa669e8bd2f841049b8c61020c510... Cc: stable@vger.kernel.org # 6.1 Fixes: c145e0b47c77 ("mm: streamline COW logic in do_swap_page()") Reported-by: Qun-wei Lin (林群崴) Qun-wei.Lin@mediatek.com Closes: https://lore.kernel.org/all/5050805753ac469e8d727c797c2218a9d780d434.camel@m... Acked-by: David Hildenbrand david@redhat.com Acked-by: "Huang, Ying" ying.huang@intel.com Reviewed-by: Steven Price steven.price@arm.com Acked-by: Catalin Marinas catalin.marinas@arm.com
v2:
- Call arch_swap_restore() directly instead of via arch_do_swap_page()
mm/memory.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/mm/memory.c b/mm/memory.c index f69fbc251198..fc25764016b3 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3932,6 +3932,13 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) } }
/** Some architectures may have to restore extra metadata to the page* when reading from swap. This metadata may be indexed by swap entry* so this must be called before swap_free().*/arch_swap_restore(entry, folio);/* * Remove the swap entry and conditionally try to free up the swapcache. * We're already holding a reference on the page but haven't mapped itIt looks like the intention is for this patch to land in 6.4, whereas the other two in the series could go in later, right? If so, I was expecting Andrew to pick this one up but he's not actually on CC. I've added him now, but you may want to send this as a separate fix so it's obvious what needs picking up for this cycle.
I was expecting that this whole series could be picked up in mm. There was a previous attempt to apply v3 of this series to mm, but that failed because a dependent patch (commit c4c597f1b367 ("arm64: mte: Do not set PG_mte_tagged if tags were not initialized")) hadn't been merged into Linus's master branch yet. The series should be good to go in now that that patch has been merged.
Did this series fall through the cracks? I can't see it in linux-next (or maybe my grep'ing failed). The commit mentioned above is in 6.4-rc3 AFAICT. Unfortunately Andrew was not cc'ed on the initial post, Will added him later, so he likely missed it. For reference, the series is here:
https://lore.kernel.org/r/20230523004312.1807357-1-pcc@google.com/
Andrew, what's your preference for this series? I'd like at least the first patch to go into 6.5 as a fix. The second patch seems to be fairly low risk and I'm happy for the third arm64 patch/cleanup to go in 6.5-rc1 (but it depends on the second patch). If you prefer, I can pick them up and send a pull request to Linus next week before -rc1. Otherwise you (or I) can queue the first patch and leave the other two for 6.6.
Thanks.