On Thu, Mar 06, 2025 at 03:00:15PM -0800, Nhat Pham wrote: > 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). This is a bit repetitive. Maybe: * -EINVAL: The folio is partially in the zeromap, which is not * currently supported. 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). > */ I would drop this whole comment now because it's mostly repeating what's now documneted above. With the comments fixed up: Reviewed-by: Yosry Ahmed <yosry.ahmed@xxxxxxxxx> > 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 >
