From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7228CC6FD1A for ; Mon, 6 Mar 2023 20:04:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230191AbjCFUEj (ORCPT ); Mon, 6 Mar 2023 15:04:39 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45530 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229650AbjCFUEh (ORCPT ); Mon, 6 Mar 2023 15:04:37 -0500 Received: from mail-ed1-x52a.google.com (mail-ed1-x52a.google.com [IPv6:2a00:1450:4864:20::52a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8341E6544A for ; Mon, 6 Mar 2023 12:04:35 -0800 (PST) Received: by mail-ed1-x52a.google.com with SMTP id ay14so39918075edb.11 for ; Mon, 06 Mar 2023 12:04:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1678133074; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=gwdV6oPXDHYeWDAi/RiRemVmk6PbuPEZPN9dBbLlQuc=; b=AJidX8wsGSpgBXq+HxNIxFLkm81d+8OurwL3na6qTBQ4BpQOYCBwEz/dKNWutHzm7L mlz36IyLPJrpnu3GM4tRf2PktEV3BAxsGIrxkgsp2eSJTKzGc6XLQEcWApPxNiW0LBUU ntgB+Sj4RmC/VsBWGD/4QdFpH92ppHWE/ASHWyQy20Ag/Zt92zCjslrPxonpjvEeA0pQ 8lqQ0App73sRlQPVzWX3CaakOPb8FXxw8deDwpIV9HCotapXR9w0kbM02ZKMzrAKSglk ZF4/lJ2lbFJ57ryjC3Id66rPruFGZwEQnGKZVLsoi7VrcQ4FSgvtd60lErkV8ESI7cPY 5Bmg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1678133074; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=gwdV6oPXDHYeWDAi/RiRemVmk6PbuPEZPN9dBbLlQuc=; b=WxzF8z+HCy60Q3YLKsJZ6YtdzGU3nKpu7FAV1+87BUaN/qf+l5s3NC+eQTm3l2TLC4 xvzsZMkPTmzRBkKag+kdjW6qYgaSM6zAC3+WYizIShFVUuarIUJ82FHJ8lap2bN3PCfa Avv6J0L5Cx42pEgdK3EgPLXvTCe/9sQQIRUaIr+Kk3iiYfSabp+hgw3XGOxWcIxIzwjb WVvPZ9WHzCjxPcpmlmkGfyT2ZsWNIV+gyFDi4FsDQMoAunj3Xo31Ny7Q+8N9DwnyiqMA jOhQ7mqWUrg6unS99T7y7rdtwQDvNbnhvVJ7V+MGX9FYPSY6MGq817TE5SajtYahvtpI /Z2Q== X-Gm-Message-State: AO0yUKWC0f/4qH0kSztKQj9gm3829FyHz0emrrV4/f4E/9u17SA9UUta mZ77Hr82/mumm5BtRXzxB34wMiKFtTnjVgGF3Bx3UA== X-Google-Smtp-Source: AK7set99xlB4THBtP/IHqKjKahSVsEGzPuzvwz4xiE2wyonl2vPjHgwa67gOzP+IYXOz+SHmhf8/P2UvrONDkbNJ78k= X-Received: by 2002:a50:bae3:0:b0:4c0:ef64:9299 with SMTP id x90-20020a50bae3000000b004c0ef649299mr6578904ede.5.1678133073729; Mon, 06 Mar 2023 12:04:33 -0800 (PST) MIME-Version: 1.0 References: <20230302232758.888157-1-mcgrof@kernel.org> <20230302232758.888157-7-mcgrof@kernel.org> In-Reply-To: <20230302232758.888157-7-mcgrof@kernel.org> From: Yosry Ahmed Date: Mon, 6 Mar 2023 12:03:57 -0800 Message-ID: Subject: Re: [PATCH 6/6] shmem: add support to ignore swap To: Luis Chamberlain Cc: hughd@google.com, akpm@linux-foundation.org, willy@infradead.org, brauner@kernel.org, linux-mm@kvack.org, p.raghav@samsung.com, da.gomez@samsung.com, a.manzanares@samsung.com, dave@stgolabs.net, keescook@chromium.org, patches@lists.linux.dev, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 2, 2023 at 3:28=E2=80=AFPM Luis Chamberlain = wrote: > > In doing experimentations with shmem having the option to avoid swap > becomes a useful mechanism. One of the *raves* about brd over shmem is > you can avoid swap, but that's not really a good reason to use brd if > we can instead use shmem. Using brd has its own good reasons to exist, > but just because "tmpfs" doesn't let you do that is not a great reason > to avoid it if we can easily add support for it. > > I don't add support for reconfiguring incompatible options, but if > we really wanted to we can add support for that. > > To avoid swap we use mapping_set_unevictable() upon inode creation, > and put a WARN_ON_ONCE() stop-gap on writepages() for reclaim. > > Acked-by: Christian Brauner > Signed-off-by: Luis Chamberlain > --- > Documentation/filesystems/tmpfs.rst | 9 ++++++--- > Documentation/mm/unevictable-lru.rst | 2 ++ > include/linux/shmem_fs.h | 1 + > mm/shmem.c | 28 +++++++++++++++++++++++++++- > 4 files changed, 36 insertions(+), 4 deletions(-) > > diff --git a/Documentation/filesystems/tmpfs.rst b/Documentation/filesyst= ems/tmpfs.rst > index e77ebdacadd0..551b621f34d9 100644 > --- a/Documentation/filesystems/tmpfs.rst > +++ b/Documentation/filesystems/tmpfs.rst > @@ -13,7 +13,8 @@ everything stored therein is lost. > > tmpfs puts everything into the kernel internal caches and grows and > shrinks to accommodate the files it contains and is able to swap > -unneeded pages out to swap space. > +unneeded pages out to swap space, if swap was enabled for the tmpfs > +filesystem. Nit: s/filesystem/mount to make it clear it's a per-mount setting? > > tmpfs extends ramfs with a few userspace configurable options listed and > explained further below, some of which can be reconfigured dynamically o= n the > @@ -33,8 +34,8 @@ configured in size at initialization and you cannot dyn= amically resize them. > Contrary to brd ramdisks, tmpfs has its own filesystem, it does not rely= on the > block layer at all. > > -Since tmpfs lives completely in the page cache and on swap, all tmpfs > -pages will be shown as "Shmem" in /proc/meminfo and "Shared" in > +Since tmpfs lives completely in the page cache and on optionally on swap= , Nit: s/on optionally on swap/optionally on swap (extra on) > +all tmpfs pages will be shown as "Shmem" in /proc/meminfo and "Shared" i= n > free(1). Notice that these counters also include shared memory > (shmem, see ipcs(1)). The most reliable way to get the count is > using df(1) and du(1). > @@ -83,6 +84,8 @@ nr_inodes The maximum number of inodes for this instan= ce. The default > is half of the number of your physical RAM pages, or (on a > machine with highmem) the number of lowmem RAM pages, > whichever is the lower. > +noswap Disables swap. Remounts must respect the original settings. > + By default swap is enabled. > =3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > These parameters accept a suffix k, m or g for kilo, mega and giga and > diff --git a/Documentation/mm/unevictable-lru.rst b/Documentation/mm/unev= ictable-lru.rst > index 92ac5dca420c..3cdcbb6e00a0 100644 > --- a/Documentation/mm/unevictable-lru.rst > +++ b/Documentation/mm/unevictable-lru.rst > @@ -42,6 +42,8 @@ The unevictable list addresses the following classes of= unevictable pages: > > * Those owned by ramfs. > > + * Those owned by tmpfs with the noswap option. > + Nit: s/noswap option/noswap mount option to make it easier to understand what noswap is > * Those mapped into SHM_LOCK'd shared memory regions. > > * Those mapped into VM_LOCKED [mlock()ed] VMAs. > diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h > index 103d1000a5a2..21989d4f8cbe 100644 > --- a/include/linux/shmem_fs.h > +++ b/include/linux/shmem_fs.h > @@ -45,6 +45,7 @@ struct shmem_sb_info { > kuid_t uid; /* Mount uid for root directory */ > kgid_t gid; /* Mount gid for root directory */ > bool full_inums; /* If i_ino should be uint or ino_t *= / > + bool noswap; /* ingores VM relcaim / swap requests= */ Nit: typos s/ingores/ignores s/relcaim/reclaim > ino_t next_ino; /* The next per-sb inode number to us= e */ > ino_t __percpu *ino_batch; /* The next per-cpu inode number to u= se */ > struct mempolicy *mpol; /* default memory policy for mappings= */ > diff --git a/mm/shmem.c b/mm/shmem.c > index 6006dbb7dbcb..cd36cb3d974c 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -119,10 +119,12 @@ struct shmem_options { > bool full_inums; > int huge; > int seen; > + bool noswap; > #define SHMEM_SEEN_BLOCKS 1 > #define SHMEM_SEEN_INODES 2 > #define SHMEM_SEEN_HUGE 4 > #define SHMEM_SEEN_INUMS 8 > +#define SHMEM_SEEN_NOSWAP 16 > }; > > #ifdef CONFIG_TMPFS > @@ -1337,6 +1339,7 @@ static int shmem_writepage(struct page *page, struc= t writeback_control *wbc) > struct address_space *mapping =3D folio->mapping; > struct inode *inode =3D mapping->host; > struct shmem_inode_info *info =3D SHMEM_I(inode); > + struct shmem_sb_info *sbinfo =3D SHMEM_SB(inode->i_sb); > swp_entry_t swap; > pgoff_t index; > > @@ -1352,7 +1355,7 @@ static int shmem_writepage(struct page *page, struc= t writeback_control *wbc) > goto redirty; > } > > - if (WARN_ON_ONCE(info->flags & VM_LOCKED)) > + if (WARN_ON_ONCE((info->flags & VM_LOCKED) || sbinfo->noswap)) > goto redirty; > > if (!total_swap_pages) > @@ -2489,6 +2492,8 @@ static struct inode *shmem_get_inode(struct mnt_idm= ap *idmap, struct super_block > shmem_set_inode_flags(inode, info->fsflags); > INIT_LIST_HEAD(&info->shrinklist); > INIT_LIST_HEAD(&info->swaplist); > + if (sbinfo->noswap) > + mapping_set_unevictable(inode->i_mapping); > simple_xattrs_init(&info->xattrs); > cache_no_acl(inode); > mapping_set_large_folios(inode->i_mapping); > @@ -3576,6 +3581,7 @@ enum shmem_param { > Opt_uid, > Opt_inode32, > Opt_inode64, > + Opt_noswap, > }; > > static const struct constant_table shmem_param_enums_huge[] =3D { > @@ -3597,6 +3603,7 @@ const struct fs_parameter_spec shmem_fs_parameters[= ] =3D { > fsparam_u32 ("uid", Opt_uid), > fsparam_flag ("inode32", Opt_inode32), > fsparam_flag ("inode64", Opt_inode64), > + fsparam_flag ("noswap", Opt_noswap), > {} > }; > > @@ -3680,6 +3687,10 @@ static int shmem_parse_one(struct fs_context *fc, = struct fs_parameter *param) > ctx->full_inums =3D true; > ctx->seen |=3D SHMEM_SEEN_INUMS; > break; > + case Opt_noswap: > + ctx->noswap =3D true; > + ctx->seen |=3D SHMEM_SEEN_NOSWAP; > + break; > } > return 0; > > @@ -3778,6 +3789,14 @@ static int shmem_reconfigure(struct fs_context *fc= ) > err =3D "Current inum too high to switch to 32-bit inums"= ; > goto out; > } > + if ((ctx->seen & SHMEM_SEEN_NOSWAP) && ctx->noswap && !sbinfo->no= swap) { > + err =3D "Cannot disable swap on remount"; > + goto out; > + } > + if (!(ctx->seen & SHMEM_SEEN_NOSWAP) && !ctx->noswap && sbinfo->n= oswap) { > + err =3D "Cannot enable swap on remount if it was disabled= on first mount"; > + goto out; > + } > > if (ctx->seen & SHMEM_SEEN_HUGE) > sbinfo->huge =3D ctx->huge; > @@ -3798,6 +3817,10 @@ static int shmem_reconfigure(struct fs_context *fc= ) > sbinfo->mpol =3D ctx->mpol; /* transfers initial re= f */ > ctx->mpol =3D NULL; > } > + > + if (ctx->noswap) > + sbinfo->noswap =3D true; > + > raw_spin_unlock(&sbinfo->stat_lock); > mpol_put(mpol); > return 0; > @@ -3852,6 +3875,8 @@ static int shmem_show_options(struct seq_file *seq,= struct dentry *root) > seq_printf(seq, ",huge=3D%s", shmem_format_huge(sbinfo->h= uge)); > #endif > shmem_show_mpol(seq, sbinfo->mpol); > + if (sbinfo->noswap) > + seq_printf(seq, ",noswap"); > return 0; > } > > @@ -3895,6 +3920,7 @@ static int shmem_fill_super(struct super_block *sb,= struct fs_context *fc) > ctx->inodes =3D shmem_default_max_inodes(); > if (!(ctx->seen & SHMEM_SEEN_INUMS)) > ctx->full_inums =3D IS_ENABLED(CONFIG_TMPFS_INODE= 64); > + sbinfo->noswap =3D ctx->noswap; > } else { > sb->s_flags |=3D SB_NOUSER; > } > -- > 2.39.1 > The change logically makes sense to me but I am not at all familiar with shmem and fs stuff, so I would rather someone else take a look.