diff options
| -rw-r--r-- | include/linux/mm.h | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index bd219ac9c026..2f6c08b53e4f 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2132,14 +2132,19 @@ static inline size_t folio_size(const struct folio *folio) * MM ("mapped shared"), or if the folio is only mapped into a single MM * ("mapped exclusively"). * + * For KSM folios, this function also returns "mapped shared" when a folio is + * mapped multiple times into the same MM, because the individual page mappings + * are independent. + * * As precise information is not easily available for all folios, this function * estimates the number of MMs ("sharers") that are currently mapping a folio * using the number of times the first page of the folio is currently mapped * into page tables. * - * For small anonymous folios (except KSM folios) and anonymous hugetlb folios, - * the return value will be exactly correct, because they can only be mapped - * at most once into an MM, and they cannot be partially mapped. + * For small anonymous folios and anonymous hugetlb folios, the return + * value will be exactly correct: non-KSM folios can only be mapped at most once + * into an MM, and they cannot be partially mapped. KSM folios are + * considered shared even if mapped multiple times into the same MM. * * For other folios, the result can be fuzzy: * #. For partially-mappable large folios (THP), the return value can wrongly @@ -2148,9 +2153,6 @@ static inline size_t folio_size(const struct folio *folio) * #. For pagecache folios (including hugetlb), the return value can wrongly * 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 positive), when the folio is mapped multiple times into - * the same MM. * * Further, this function only considers current page table mappings that * are tracked using the folio mapcount(s). |