mm/page_vma_mapped.c: check possible huge PMD map with transhuge_vma_suitable()
authorYang Shi <shy828301@gmail.com>
Fri, 13 May 2022 19:17:05 +0000 (12:17 -0700)
committerakpm <akpm@linux-foundation.org>
Mon, 4 Jul 2022 01:08:37 +0000 (18:08 -0700)
commit27b1a336c2b8982bca1988edfc9d5773d3e484fe
treee9002d90743acd58901113b8a5af798343e83ba2
parent53feb49b893066e102fbef6c96f9eaf669963f1d
mm/page_vma_mapped.c: check possible huge PMD map with transhuge_vma_suitable()

IIUC page_vma_mapped_walk() checks if the vma is possibly huge PMD mapped
with transparent_hugepage_active() and "pvmw->nr_pages >= HPAGE_PMD_NR".

Actually pvmw->nr_pages is returned by compound_nr() or folio_nr_pages(),
so the page should be THP as long as "pvmw->nr_pages >= HPAGE_PMD_NR".
And it is guaranteed THP is allocated for valid VMA in the first place.
But it may be not PMD mapped if the VMA is file VMA and it is not properly
aligned.  The transhuge_vma_suitable() is used to do such check, so
replace transparent_hugepage_active() to it, which is too heavy and
overkilling.

Link: https://lkml.kernel.org/r/20220513191705.457775-1-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
include/linux/huge_mm.h
mm/page_vma_mapped.c