From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-181.mta0.migadu.com (out-181.mta0.migadu.com [91.218.175.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E3A7A27811E for ; Thu, 6 Mar 2025 23:42:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741304542; cv=none; b=PVPQVRMg5RcqQZHcSHnD2w0UcXOK7LQGmC7iv3NO2hYvIlmcAgbzDHFsbYuS8nNMqRo99ZGU7tYtirCetXZys4qXvZ+IFUev0+2wWksC1FO5NM3GRP7YyEm6VNKbmbgXZKLKaRufAAkiOHCKIY2tCUv+VYS56Ud0PUllFBZUiK8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741304542; c=relaxed/simple; bh=LtCL5Wa78a/OLv3g+IY7kOW6zY+LdenxnBgMM/9q5fA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Y/E9nUWKsm3vtPkI9SLqP+Yddw+ppND+R2hGnpJwoNV5+QgsMoXb0ShBaCPGr6SKfg9ixluR9dmiVBPziASYztWeHQhtFdy1P7YU65dkfJem1WUClQSIlKzYwBFhadFW1xve7hc29atcNGz22hNNyH7IW52GA7jr/uVystLJzuo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=bSNq+nD1; arc=none smtp.client-ip=91.218.175.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="bSNq+nD1" Date: Thu, 6 Mar 2025 23:42:08 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1741304534; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=fU6cPBemXEC5vkZEvT/CCIy/jzWhHpo6npFWGn/8iRI=; b=bSNq+nD1O3vZsgkjn7awJJ37l2cfr7+cFXTCbKGFr854zjuC25z94Ey3ogM7Nwvj5hnuB+ wa1rA4qoXjZTxqL1Eadkf1PdzqrSQn2LWuqUt3o6koSmCVbSG/9j4SOhLOo5mpL92/BFHQ 8AOOM2y3mFvAYh0rOi217HSy2TSW/Lw= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yosry Ahmed To: Nhat Pham Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, chengming.zhou@linux.dev, linux-mm@kvack.org, kernel-team@meta.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] page_io: return proper error codes for swap_read_folio_zeromap() Message-ID: References: <20250306230015.1456794-1-nphamcs@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250306230015.1456794-1-nphamcs@gmail.com> X-Migadu-Flow: FLOW_OUT 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@gmail.com/ > > Suggested-by: Yosry Ahmed > Suggested-by: Johannes Weiner > Signed-off-by: Nhat Pham > --- > 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 > 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 >