diff options
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/mm.h | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 059477821625..c7470da5797f 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2184,7 +2184,7 @@ static inline size_t folio_size(struct folio *folio) * indicate "mapped shared" (false positive) when two VMAs in the same MM * cover the same file range. * #. For (small) KSM folios, the return value can wrongly indicate "mapped - * shared" (false negative), when the folio is mapped multiple times into + * shared" (false positive), when the folio is mapped multiple times into * the same MM. * * Further, this function only considers current page table mappings that @@ -2201,7 +2201,22 @@ static inline size_t folio_size(struct folio *folio) */ static inline bool folio_likely_mapped_shared(struct folio *folio) { - return page_mapcount(folio_page(folio, 0)) > 1; + int mapcount = folio_mapcount(folio); + + /* Only partially-mappable folios require more care. */ + if (!folio_test_large(folio) || unlikely(folio_test_hugetlb(folio))) + return mapcount > 1; + + /* A single mapping implies "mapped exclusively". */ + if (mapcount <= 1) + return false; + + /* If any page is mapped more than once we treat it "mapped shared". */ + if (folio_entire_mapcount(folio) || mapcount > folio_nr_pages(folio)) + return true; + + /* Let's guess based on the first subpage. */ + return atomic_read(&folio->_mapcount) > 0; } #ifndef HAVE_ARCH_MAKE_PAGE_ACCESSIBLE |