On Thu, Mar 26, 2026 at 09:42:48PM -0400, Zi Yan wrote: > They are used by READ_ONLY_THP_FOR_FS to handle writes to FSes without > large folio support, so that read-only THPs created in these FSes are not > seen by the FSes when the underlying fd becomes writable. Now read-only PMD > THPs only appear in a FS with large folio support and the supported orders > include PMD_ORDRE.
Typo: PMD_ORDRE -> PMD_ORDER > > Signed-off-by: Zi Yan <[email protected]> This looks obviously-correct since this stuff wouldn't have been invoked for large folio file systems before + they already had to handle it separately, and this function is only tied to CONFIG_READ_ONLY_THP_FOR_FS (+ a quick grep suggests you didn't miss anything), so: Reviewed-by: Lorenzo Stoakes (Oracle) <[email protected]> > --- > fs/open.c | 27 --------------------------- > include/linux/pagemap.h | 29 ----------------------------- > mm/filemap.c | 1 - > mm/huge_memory.c | 1 - > mm/khugepaged.c | 29 ++--------------------------- > 5 files changed, 2 insertions(+), 85 deletions(-) > > diff --git a/fs/open.c b/fs/open.c > index 91f1139591ab..cef382d9d8b8 100644 > --- a/fs/open.c > +++ b/fs/open.c > @@ -970,33 +970,6 @@ static int do_dentry_open(struct file *f, > if ((f->f_flags & O_DIRECT) && !(f->f_mode & FMODE_CAN_ODIRECT)) > return -EINVAL; > > - /* > - * XXX: Huge page cache doesn't support writing yet. Drop all page > - * cache for this file before processing writes. > - */ > - if (f->f_mode & FMODE_WRITE) { > - /* > - * Depends on full fence from get_write_access() to synchronize > - * against collapse_file() regarding i_writecount and nr_thps > - * updates. Ensures subsequent insertion of THPs into the page > - * cache will fail. > - */ > - if (filemap_nr_thps(inode->i_mapping)) { > - struct address_space *mapping = inode->i_mapping; > - > - filemap_invalidate_lock(inode->i_mapping); > - /* > - * unmap_mapping_range just need to be called once > - * here, because the private pages is not need to be > - * unmapped mapping (e.g. data segment of dynamic > - * shared libraries here). > - */ > - unmap_mapping_range(mapping, 0, 0, 0); > - truncate_inode_pages(mapping, 0); > - filemap_invalidate_unlock(inode->i_mapping); > - } > - } > - > return 0; > > cleanup_all: > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h > index ec442af3f886..dad3f8846cdc 100644 > --- a/include/linux/pagemap.h > +++ b/include/linux/pagemap.h > @@ -530,35 +530,6 @@ static inline size_t mapping_max_folio_size(const struct > address_space *mapping) > return PAGE_SIZE << mapping_max_folio_order(mapping); > } > > -static inline int filemap_nr_thps(const struct address_space *mapping) > -{ > -#ifdef CONFIG_READ_ONLY_THP_FOR_FS > - return atomic_read(&mapping->nr_thps); > -#else > - return 0; > -#endif > -} > - > -static inline void filemap_nr_thps_inc(struct address_space *mapping) > -{ > -#ifdef CONFIG_READ_ONLY_THP_FOR_FS > - if (!mapping_large_folio_support(mapping)) > - atomic_inc(&mapping->nr_thps); > -#else > - WARN_ON_ONCE(mapping_large_folio_support(mapping) == 0); > -#endif > -} > - > -static inline void filemap_nr_thps_dec(struct address_space *mapping) > -{ > -#ifdef CONFIG_READ_ONLY_THP_FOR_FS > - if (!mapping_large_folio_support(mapping)) > - atomic_dec(&mapping->nr_thps); > -#else > - WARN_ON_ONCE(mapping_large_folio_support(mapping) == 0); > -#endif > -} > - > struct address_space *folio_mapping(const struct folio *folio); > > /** > diff --git a/mm/filemap.c b/mm/filemap.c > index 2b933a1da9bd..4248e7cdecf3 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -189,7 +189,6 @@ static void filemap_unaccount_folio(struct address_space > *mapping, > lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, -nr); > } else if (folio_test_pmd_mappable(folio)) { > lruvec_stat_mod_folio(folio, NR_FILE_THPS, -nr); > - filemap_nr_thps_dec(mapping); > } > if (test_bit(AS_KERNEL_FILE, &folio->mapping->flags)) > mod_node_page_state(folio_pgdat(folio), > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index b2a6060b3c20..c7873dbdc470 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -3833,7 +3833,6 @@ static int __folio_freeze_and_split_unmapped(struct > folio *folio, unsigned int n > } else { > lruvec_stat_mod_folio(folio, > NR_FILE_THPS, -nr); > - filemap_nr_thps_dec(mapping); > } > } > } > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 45b12ffb1550..8004ab8de6d2 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -2104,20 +2104,8 @@ static enum scan_result collapse_file(struct mm_struct > *mm, unsigned long addr, > goto xa_unlocked; > } > > - if (!is_shmem) { > - filemap_nr_thps_inc(mapping); > - /* > - * Paired with the fence in do_dentry_open() -> > get_write_access() > - * to ensure i_writecount is up to date and the update to > nr_thps > - * is visible. Ensures the page cache will be truncated if the > - * file is opened writable. > - */ > - smp_mb(); > - if (inode_is_open_for_write(mapping->host)) { > - result = SCAN_FAIL; > - filemap_nr_thps_dec(mapping); > - } > - } > + if (!is_shmem && inode_is_open_for_write(mapping->host)) > + result = SCAN_FAIL; > > xa_locked: > xas_unlock_irq(&xas); > @@ -2296,19 +2284,6 @@ static enum scan_result collapse_file(struct mm_struct > *mm, unsigned long addr, > folio_putback_lru(folio); > folio_put(folio); > } > - /* > - * Undo the updates of filemap_nr_thps_inc for non-SHMEM > - * file only. This undo is not needed unless failure is > - * due to SCAN_COPY_MC. > - */ > - if (!is_shmem && result == SCAN_COPY_MC) { > - filemap_nr_thps_dec(mapping); > - /* > - * Paired with the fence in do_dentry_open() -> > get_write_access() > - * to ensure the update to nr_thps is visible. > - */ > - smp_mb(); > - } > > new_folio->mapping = NULL; > > -- > 2.43.0 > Cheers, Lorenzo
