Mike Kravetz [off-list ref] writes:

On 12/19/22 13:06, Michal Hocko wrote:

quoted

On Fri 16-12-22 11:20:12, Mike Kravetz wrote:

quoted

zap_page_range was originally designed to unmap pages within an address
range that could span multiple vmas.  While working on [1], it was
discovered that all callers of zap_page_range pass a range entirely within
a single vma.  In addition, the mmu notification call within zap_page
range does not correctly handle ranges that span multiple vmas as calls
should be vma specific.

Could you spend a sentence or two explaining what is wrong here?

Hmmmm?  My assumption was that the range passed to mmu_notifier_range_init()
was supposed to be within the specified vma.  When looking into the notifier
routines, I could not find any documentation about the usage of the vma within
the mmu_notifier_range structure.  It was introduced with commit bf198b2b34bf
"mm/mmu_notifier: pass down vma and reasons why mmu notifier is happening".
However, I do not see this being used today.

Of course, I could be missing something, so adding Jérôme.

The only use for mmu_notifier_range->vma I can find is in
mmu_notifier_range_update_to_read_only() which was introduced in
c6d23413f81b ("mm/mmu_notifier: mmu_notifier_range_update_to_read_only()
helper"). However there are no users of that symbol so I think we can
remove it along with the mmu_notifier_range->vma field.

I will put togeather a patch to do that.

quoted

quoted

Instead of fixing zap_page_range, change all callers to use the new
routine zap_vma_page_range.  zap_vma_page_range is just a wrapper around
zap_page_range_single passing in NULL zap details.  The name is also
more in line with other exported routines that operate within a vma.
We can then remove zap_page_range.

I would stick with zap_page_range_single rather than adding a new
wrapper but nothing really critical.

I am fine with doing that as well.  My only reason for the wrapper is that all 
callers outside mm/memory.c would pass in NULL zap details.

quoted

quoted

Also, change madvise_dontneed_single_vma to use this new routine.

[1] https://lore.kernel.org/linux-mm/20221114235507.294320-2-mike.kravetz@oracle.com/ (local)
Suggested-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Mike Kravetz <redacted>

Other than that LGTM
Acked-by: Michal Hocko <mhocko@suse.com>

Thanks!

Thanks for taking a look.