Similar to zswap_load(), also return proper error codes for swap_read_folio_zeromap(): * 0 on success. The folio is unlocked and marked up-to-date. * -ENOENT, if the folio is entirely not zeromapped. * -EINVAL (with the follio unlocked but not marked to date), if the folio is partially zeromapped. This is not supported, and will SIGBUS the faulting process. This patch is purely a clean-up, and should not have any behavioral change. It is based on (and should be applied on top of) [1]. [1]: https://lore.kernel.org/linux-mm/20250306205011.784787-1-nphamcs@xxxxxxxxx/ Suggested-by: Yosry Ahmed <yosry.ahmed@xxxxxxxxx> Suggested-by: Johannes Weiner <hannes@xxxxxxxxxxx> Signed-off-by: Nhat Pham <nphamcs@xxxxxxxxx> --- mm/page_io.c | 35 ++++++++++++++++++++++++++--------- 1 file changed, 26 insertions(+), 9 deletions(-) diff --git a/mm/page_io.c b/mm/page_io.c index 4bce19df557b..48ed1e810392 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -511,7 +511,23 @@ static void sio_read_complete(struct kiocb *iocb, long ret) mempool_free(sio, sio_pool); } -static bool swap_read_folio_zeromap(struct folio *folio) +/** + * swap_read_folio_zeromap - check if the folio was zeromapped, and if so, + * zero-fill it. + * @folio: the folio. + * + * Return: 0 on success, with the folio zero-filled, unlocked, and marked + * up-to-date, or one of the following error codes: + * + * -ENOENT: the folio is entirely not zeromapped. The folio remains locked. + * + * -EINVAL: some of the subpages in the folio are zeromaped, but not all of + * them. This is an error because we don't currently support a large folio + * that is partially in the zeromap. The folio is unlocked, but NOT marked + * up-to-date, so that an IO error is emitted (e.g. do_swap_page() will + * sigbus). + */ +static int swap_read_folio_zeromap(struct folio *folio) { int nr_pages = folio_nr_pages(folio); struct obj_cgroup *objcg; @@ -519,15 +535,17 @@ static bool swap_read_folio_zeromap(struct folio *folio) /* * Swapping in a large folio that is partially in the zeromap is not - * currently handled. Return true without marking the folio uptodate so + * currently handled. Return -EINVAL without marking the folio uptodate so * that an IO error is emitted (e.g. do_swap_page() will sigbus). */ if (WARN_ON_ONCE(swap_zeromap_batch(folio->swap, nr_pages, - &is_zeromap) != nr_pages)) - return true; + &is_zeromap) != nr_pages)) { + folio_unlock(folio); + return -EINVAL; + } if (!is_zeromap) - return false; + return -ENOENT; objcg = get_obj_cgroup_from_folio(folio); count_vm_events(SWPIN_ZERO, nr_pages); @@ -538,7 +556,8 @@ static bool swap_read_folio_zeromap(struct folio *folio) folio_zero_range(folio, 0, folio_size(folio)); folio_mark_uptodate(folio); - return true; + folio_unlock(folio); + return 0; } static void swap_read_folio_fs(struct folio *folio, struct swap_iocb **plug) @@ -635,10 +654,8 @@ void swap_read_folio(struct folio *folio, struct swap_iocb **plug) } delayacct_swapin_start(); - if (swap_read_folio_zeromap(folio)) { - folio_unlock(folio); + if (swap_read_folio_zeromap(folio) != -ENOENT) goto finish; - } if (zswap_load(folio) != -ENOENT) goto finish; -- 2.43.5
