mm/page_alloc: update comments in __free_pages_ok()

Add a comment to explain why we call get_pfnblock_migratetype() twice in
__free_pages_ok().

Link: https://lkml.kernel.org/r/20221201135045.31663-1-wonder_rock@126.com
Signed-off-by: Deyan Wang <wonder_rock@126.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Deyan Wang 2022-12-01 21:50:45 +08:00 committed by Andrew Morton
parent 480017957d
commit ac4b2901a1
1 changed files with 5 additions and 0 deletions

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@ -1702,6 +1702,11 @@ static void __free_pages_ok(struct page *page, unsigned int order,
if (!free_pages_prepare(page, order, true, fpi_flags))
return;
/*
* Calling get_pfnblock_migratetype() without spin_lock_irqsave() here
* is used to avoid calling get_pfnblock_migratetype() under the lock.
* This will reduce the lock holding time.
*/
migratetype = get_pfnblock_migratetype(page, pfn);
spin_lock_irqsave(&zone->lock, flags);