From: Zhang Peng shrink_folio_list() contains two large self-contained sections: the pageout() dispatch state machine and the folio-freeing path (buffer release, lazyfree, __remove_mapping, folio_batch). Extract them into pageout_one() and folio_free() respectively to reduce the size of shrink_folio_list() and make each step independently readable. No functional change Suggested-by: Kairui Song Signed-off-by: Zhang Peng --- mm/vmscan.c | 270 ++++++++++++++++++++++++++++++++++-------------------------- 1 file changed, 155 insertions(+), 115 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 0860a48d5bf3..c8ff742ed891 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1070,6 +1070,153 @@ static void folio_active_bounce(struct folio *folio, struct reclaim_stat *stat, } } +static bool folio_free(struct folio *folio, struct folio_batch *free_folios, + struct scan_control *sc, struct reclaim_stat *stat) +{ + unsigned int nr_pages = folio_nr_pages(folio); + struct address_space *mapping = folio_mapping(folio); + + /* + * If the folio has buffers, try to free the buffer + * mappings associated with this folio. If we succeed + * we try to free the folio as well. + * + * We do this even if the folio is dirty. + * filemap_release_folio() does not perform I/O, but it + * is possible for a folio to have the dirty flag set, + * but it is actually clean (all its buffers are clean). + * This happens if the buffers were written out directly, + * with submit_bh(). ext3 will do this, as well as + * the blockdev mapping. filemap_release_folio() will + * discover that cleanness and will drop the buffers + * and mark the folio clean - it can be freed. + * + * Rarely, folios can have buffers and no ->mapping. + * These are the folios which were not successfully + * invalidated in truncate_cleanup_folio(). We try to + * drop those buffers here and if that worked, and the + * folio is no longer mapped into process address space + * (refcount == 1) it can be freed. Otherwise, leave + * the folio on the LRU so it is swappable. + */ + if (folio_needs_release(folio)) { + if (!filemap_release_folio(folio, sc->gfp_mask)) { + folio_active_bounce(folio, stat, nr_pages); + return false; + } + + if (!mapping && folio_ref_count(folio) == 1) { + folio_unlock(folio); + if (folio_put_testzero(folio)) + goto free_it; + else { + /* + * rare race with speculative reference. + * the speculative reference will free + * this folio shortly, so we may + * increment nr_reclaimed here (and + * leave it off the LRU). + */ + stat->nr_reclaimed += nr_pages; + return true; + } + } + } + + if (folio_test_lazyfree(folio)) { + /* follow __remove_mapping for reference */ + if (!folio_ref_freeze(folio, 1)) + return false; + /* + * The folio has only one reference left, which is + * from the isolation. After the caller puts the + * folio back on the lru and drops the reference, the + * folio will be freed anyway. It doesn't matter + * which lru it goes on. So we don't bother checking + * the dirty flag here. + */ + count_vm_events(PGLAZYFREED, nr_pages); + count_memcg_folio_events(folio, PGLAZYFREED, nr_pages); + } else if (!mapping || !__remove_mapping(mapping, folio, true, + sc->target_mem_cgroup)) + return false; + + folio_unlock(folio); +free_it: + /* + * Folio may get swapped out as a whole, need to account + * all pages in it. + */ + stat->nr_reclaimed += nr_pages; + + folio_unqueue_deferred_split(folio); + if (folio_batch_add(free_folios, folio) == 0) { + mem_cgroup_uncharge_folios(free_folios); + try_to_unmap_flush(); + free_unref_folios(free_folios); + } + return true; +} + +static void pageout_one(struct folio *folio, struct list_head *ret_folios, + struct folio_batch *free_folios, + struct scan_control *sc, struct reclaim_stat *stat, + struct swap_iocb **plug, struct list_head *folio_list) +{ + struct address_space *mapping = folio_mapping(folio); + unsigned int nr_pages = folio_nr_pages(folio); + + switch (pageout(folio, mapping, plug, folio_list)) { + case PAGE_ACTIVATE: + /* + * If shmem folio is split when writeback to swap, + * the tail pages will make their own pass through + * this function and be accounted then. + */ + if (nr_pages > 1 && !folio_test_large(folio)) { + sc->nr_scanned -= (nr_pages - 1); + nr_pages = 1; + } + folio_active_bounce(folio, stat, nr_pages); + fallthrough; + case PAGE_KEEP: + goto locked_keepit; + case PAGE_SUCCESS: + if (nr_pages > 1 && !folio_test_large(folio)) { + sc->nr_scanned -= (nr_pages - 1); + nr_pages = 1; + } + stat->nr_pageout += nr_pages; + + if (folio_test_writeback(folio)) + goto keepit; + if (folio_test_dirty(folio)) + goto keepit; + + /* + * A synchronous write - probably a ramdisk. Go + * ahead and try to reclaim the folio. + */ + if (!folio_trylock(folio)) + goto keepit; + if (folio_test_dirty(folio) || + folio_test_writeback(folio)) + goto locked_keepit; + mapping = folio_mapping(folio); + fallthrough; + case PAGE_CLEAN: + ; /* try to free the folio below */ + } + if (folio_free(folio, free_folios, sc, stat)) + return; +locked_keepit: + folio_unlock(folio); +keepit: + list_add(&folio->lru, ret_folios); + VM_BUG_ON_FOLIO(folio_test_lru(folio) || + folio_test_unevictable(folio), folio); +} + /* * Reclaimed folios are counted in stat->nr_reclaimed. */ @@ -1415,125 +1562,16 @@ static void shrink_folio_list(struct list_head *folio_list, * starts and then write it out here. */ try_to_unmap_flush_dirty(); - switch (pageout(folio, mapping, &plug, folio_list)) { - case PAGE_KEEP: - goto keep_locked; - case PAGE_ACTIVATE: - /* - * If shmem folio is split when writeback to swap, - * the tail pages will make their own pass through - * this function and be accounted then. - */ - if (nr_pages > 1 && !folio_test_large(folio)) { - sc->nr_scanned -= (nr_pages - 1); - nr_pages = 1; - } - goto activate_locked; - case PAGE_SUCCESS: - if (nr_pages > 1 && !folio_test_large(folio)) { - sc->nr_scanned -= (nr_pages - 1); - nr_pages = 1; - } - stat->nr_pageout += nr_pages; - - if (folio_test_writeback(folio)) - goto keep; - if (folio_test_dirty(folio)) - goto keep; - - /* - * A synchronous write - probably a ramdisk. Go - * ahead and try to reclaim the folio. - */ - if (!folio_trylock(folio)) - goto keep; - if (folio_test_dirty(folio) || - folio_test_writeback(folio)) - goto keep_locked; - mapping = folio_mapping(folio); - fallthrough; - case PAGE_CLEAN: - ; /* try to free the folio below */ - } - } - - /* - * If the folio has buffers, try to free the buffer - * mappings associated with this folio. If we succeed - * we try to free the folio as well. - * - * We do this even if the folio is dirty. - * filemap_release_folio() does not perform I/O, but it - * is possible for a folio to have the dirty flag set, - * but it is actually clean (all its buffers are clean). - * This happens if the buffers were written out directly, - * with submit_bh(). ext3 will do this, as well as - * the blockdev mapping. filemap_release_folio() will - * discover that cleanness and will drop the buffers - * and mark the folio clean - it can be freed. - * - * Rarely, folios can have buffers and no ->mapping. - * These are the folios which were not successfully - * invalidated in truncate_cleanup_folio(). We try to - * drop those buffers here and if that worked, and the - * folio is no longer mapped into process address space - * (refcount == 1) it can be freed. Otherwise, leave - * the folio on the LRU so it is swappable. - */ - if (folio_needs_release(folio)) { - if (!filemap_release_folio(folio, sc->gfp_mask)) - goto activate_locked; - if (!mapping && folio_ref_count(folio) == 1) { - folio_unlock(folio); - if (folio_put_testzero(folio)) - goto free_it; - else { - /* - * rare race with speculative reference. - * the speculative reference will free - * this folio shortly, so we may - * increment nr_reclaimed here (and - * leave it off the LRU). - */ - stat->nr_reclaimed += nr_pages; - continue; - } - } + pageout_one(folio, &ret_folios, &free_folios, sc, stat, + &plug, folio_list); + goto next; } - if (folio_test_lazyfree(folio)) { - /* follow __remove_mapping for reference */ - if (!folio_ref_freeze(folio, 1)) - goto keep_locked; - /* - * The folio has only one reference left, which is - * from the isolation. After the caller puts the - * folio back on the lru and drops the reference, the - * folio will be freed anyway. It doesn't matter - * which lru it goes on. So we don't bother checking - * the dirty flag here. - */ - count_vm_events(PGLAZYFREED, nr_pages); - count_memcg_folio_events(folio, PGLAZYFREED, nr_pages); - } else if (!mapping || !__remove_mapping(mapping, folio, true, - sc->target_mem_cgroup)) + if (!folio_free(folio, &free_folios, sc, stat)) goto keep_locked; - folio_unlock(folio); -free_it: - /* - * Folio may get swapped out as a whole, need to account - * all pages in it. - */ - stat->nr_reclaimed += nr_pages; - - folio_unqueue_deferred_split(folio); - if (folio_batch_add(&free_folios, folio) == 0) { - mem_cgroup_uncharge_folios(&free_folios); - try_to_unmap_flush(); - free_unref_folios(&free_folios); - } - continue; + else + continue; activate_locked_split: /* @@ -1552,6 +1590,8 @@ static void shrink_folio_list(struct list_head *folio_list, list_add(&folio->lru, &ret_folios); VM_BUG_ON_FOLIO(folio_test_lru(folio) || folio_test_unevictable(folio), folio); +next: + continue; } /* 'folio_list' is always empty here */ -- 2.43.7