From: Christoph Hellwig <hch@xxxxxx> Subject: mm: allow a NULL fn callback in apply_to_page_range Besides calling the callback on each page, apply_to_page_range also has the effect of pre-faulting all PTEs for the range. To support callers that only need the pre-faulting, make the callback optional. Based on a patch from Minchan Kim <minchan@xxxxxxxxxx>. Link: https://lkml.kernel.org/r/20201002122204.1534411-5-hch@xxxxxx Signed-off-by: Christoph Hellwig <hch@xxxxxx> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> Cc: Juergen Gross <jgross@xxxxxxxx> Cc: Matthew Auld <matthew.auld@xxxxxxxxx> Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> Cc: Nitin Gupta <ngupta@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> Cc: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memory.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) --- a/mm/memory.c~mm-allow-a-null-fn-callback-in-apply_to_page_range +++ a/mm/memory.c @@ -2391,13 +2391,15 @@ static int apply_to_pte_range(struct mm_ arch_enter_lazy_mmu_mode(); - do { - if (create || !pte_none(*pte)) { - err = fn(pte++, addr, data); - if (err) - break; - } - } while (addr += PAGE_SIZE, addr != end); + if (fn) { + do { + if (create || !pte_none(*pte)) { + err = fn(pte++, addr, data); + if (err) + break; + } + } while (addr += PAGE_SIZE, addr != end); + } *mask |= PGTBL_PTE_MODIFIED; arch_leave_lazy_mmu_mode(); _
