Re: [PATCH 6.1.y] mm,swapops: update check in is_pfn_swap_entry for hwpoison entries

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, May 07, 2024 at 05:28:22PM +0800, Miaohe Lin wrote:
> From: Oscar Salvador <osalvador@suse.de>
> 
> Tony reported that the Machine check recovery was broken in v6.9-rc1, as
> he was hitting a VM_BUG_ON when injecting uncorrectable memory errors to
> DRAM.
> 
> After some more digging and debugging on his side, he realized that this
> went back to v6.1, with the introduction of 'commit 0d206b5d2e0d
> ("mm/swap: add swp_offset_pfn() to fetch PFN from swap entry")'.  That
> commit, among other things, introduced swp_offset_pfn(), replacing
> hwpoison_entry_to_pfn() in its favour.
> 
> The patch also introduced a VM_BUG_ON() check for is_pfn_swap_entry(), but
> is_pfn_swap_entry() never got updated to cover hwpoison entries, which
> means that we would hit the VM_BUG_ON whenever we would call
> swp_offset_pfn() for such entries on environments with CONFIG_DEBUG_VM
> set.  Fix this by updating the check to cover hwpoison entries as well,
> and update the comment while we are it.
> 
> Link: https://lkml.kernel.org/r/20240407130537.16977-1-osalvador@suse.de
> Fixes: 0d206b5d2e0d ("mm/swap: add swp_offset_pfn() to fetch PFN from swap entry")
> Signed-off-by: Oscar Salvador <osalvador@suse.de>
> Reported-by: Tony Luck <tony.luck@intel.com>
> Closes: https://lore.kernel.org/all/Zg8kLSl2yAlA3o5D@agluck-desk3/
> Tested-by: Tony Luck <tony.luck@intel.com>
> Reviewed-by: Peter Xu <peterx@redhat.com>
> Reviewed-by: David Hildenbrand <david@redhat.com>
> Acked-by: Miaohe Lin <linmiaohe@huawei.com>
> Cc: <stable@vger.kernel.org>	[6.1.x]
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> (cherry picked from commit 07a57a338adb6ec9e766d6a6790f76527f45ceb5)
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
>  include/linux/swapops.h | 105 ++++++++++++++++++++--------------------
>  1 file changed, 53 insertions(+), 52 deletions(-)

Now queued up, thanks.

greg k-h