collapse_file() requires FSes supporting large folio with at least PMD_ORDER, so replace the READ_ONLY_THP_FOR_FS check with that. MADV_COLLAPSE ignores shmem huge config, so exclude the check for shmem.
While at it, replace VM_BUG_ON with VM_WARN_ON_ONCE. Add a helper function mapping_pmd_folio_support() for FSes supporting large folio with at least PMD_ORDER. Signed-off-by: Zi Yan <[email protected]> Reviewed-by: Lance Yang <[email protected]> Reviewed-by: Baolin Wang <[email protected]> Acked-by: David Hildenbrand (Arm) <[email protected]> Reviewed-by: Nico Pache <[email protected]> Cc: Al Viro <[email protected]> Cc: Barry Song <[email protected]> Cc: Chris Mason <[email protected]> Cc: Christian Brauner <[email protected]> Cc: David Sterba <[email protected]> Cc: Dev Jain <[email protected]> Cc: Jan Kara <[email protected]> Cc: Liam Howlett <[email protected]> Cc: Lorenzo Stoakes <[email protected]> Cc: Matthew Wilcox (Oracle) <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Mike Rapoport <[email protected]> Cc: Ryan Roberts <[email protected]> Cc: Shuah Khan <[email protected]> Cc: Song Liu <[email protected]> Cc: Suren Baghdasaryan <[email protected]> Cc: Vlastimil Babka <[email protected]> --- include/linux/pagemap.h | 27 +++++++++++++++++++++++++++ mm/khugepaged.c | 10 ++++++++-- 2 files changed, 35 insertions(+), 2 deletions(-) diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 1f50991b43e3b..308d846531d03 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -513,6 +513,33 @@ static inline bool mapping_large_folio_support(const struct address_space *mappi return mapping_max_folio_order(mapping) > 0; } +/** + * mapping_pmd_folio_support() - Check if a mapping supports PMD-sized folio + * @mapping: The address_space + * + * While some mappings support large folios, they might not support PMD-sized + * folios. This function checks whether a mapping supports PMD-sized folios. + * For example, khugepaged needs this information before attempting to + * collapsing THPs. + * + * Return: True if PMD-sized folios are supported, otherwise false. + */ +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +static inline bool mapping_pmd_folio_support(const struct address_space *mapping) +{ + /* AS_FOLIO_ORDER is only reasonable for pagecache folios */ + VM_WARN_ON_ONCE((unsigned long)mapping & FOLIO_MAPPING_ANON); + + return mapping_min_folio_order(mapping) <= PMD_ORDER && + mapping_max_folio_order(mapping) >= PMD_ORDER; +} +#else +static inline bool mapping_pmd_folio_support(const struct address_space *mapping) +{ + return false; +} +#endif + /* Return the maximum folio size for this pagecache mapping, in bytes. */ static inline size_t mapping_max_folio_size(const struct address_space *mapping) { diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 5ba298d420b74..afd61168d915c 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2243,8 +2243,14 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, int nr_none = 0; bool is_shmem = shmem_file(file); - VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem); - VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); + /* + * MADV_COLLAPSE ignores shmem huge config, so do not check shmem + * + * TODO: once shmem always calls mapping_set_large_folios() on its + * mapping, the shmem check can be removed. + */ + VM_WARN_ON_ONCE(!is_shmem && !mapping_pmd_folio_support(mapping)); + VM_WARN_ON_ONCE(start & (HPAGE_PMD_NR - 1)); result = alloc_charge_folio(&new_folio, mm, cc, HPAGE_PMD_ORDER); if (result != SCAN_SUCCEED) -- 2.53.0
