On Wed, May 26, 2021 at 01:12:38PM -0700, Yang Shi wrote:

When debugging the bug reported by Wang Yugui [1], try_to_unmap() may
fail, but the first VM_BUG_ON_PAGE() just checks page_mapcount() however
it may miss the failure when head page is unmapped but other subpage is
mapped.  Then the second DEBUG_VM BUG() that check total mapcount would
catch it.  This may incur some confusion.  And this is not a fatal issue,
so consolidate the two DEBUG_VM checks into one VM_WARN_ON_ONCE_PAGE().

[1] https://lore.kernel.org/linux-mm/20210412180659.B9E3.409509F4@e16-tech.com/ (local)

Reviewed-by: Zi Yan <ziy@nvidia.com>
Signed-off-by: Yang Shi <redacted>

For both patches: 

Acked-by: Kirill A. Shutemov <redacted>

-- 
 Kirill A. Shutemov