Message-ID: <ba9a4b5405774f157df790c57d658b9f37e1ae61.camel@collabora.com>
Subject: Re: [PATCH] hostfs: Fix writeback of dirty pages
From:   Ritesh Raj Sarraf <ritesh.sarraf@collabora.com>
Reply-To: ritesh.sarraf@collabora.com
To:     Sjoerd Simons <sjoerd@collabora.com>, linux-um@lists.infradead.org
Cc:     Anton Ivanov <anton.ivanov@cambridgegreys.com>,
        Jeff Dike <jdike@addtoit.com>,
        Richard Weinberger <richard@nod.at>,
        linux-kernel@vger.kernel.org
Date:   Thu, 11 Nov 2021 22:40:02 +0530
In-Reply-To: <20211105081052.2353801-1-sjoerd@collabora.com>
References: <20211105081052.2353801-1-sjoerd@collabora.com>
Organization: Collabora
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On Fri, 2021-11-05 at 09:10 +0100, Sjoerd Simons wrote:
> Hostfs was not setting up the backing device information, which means
> it
> uses the noop bdi. The noop bdi does not have the writeback
> capability
> enabled, which in turns means=C2=A0 dirty pages never got written back to
> storage.
>=20
> In other words programs using mmap to write to files on=C2=A0 hostfs neve=
r
> actually got their data written out...
>=20
> Fix this by simply setting up the bdi with default settings as all
> the
> required code for writeback is already in place.
>=20
> Signed-off-by: Sjoerd Simons <sjoerd@collabora.com>
>=20

Tested-by: Ritesh Raj Sarraf <ritesh@collabora.com>

> ---
>=20
> =C2=A0fs/hostfs/hostfs_kern.c | 3 +++
> =C2=A01 file changed, 3 insertions(+)
>=20
> diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c
> index d5c9d886cd9f..ef481c3d9019 100644
> --- a/fs/hostfs/hostfs_kern.c
> +++ b/fs/hostfs/hostfs_kern.c
> @@ -924,6 +924,9 @@ static int hostfs_fill_sb_common(struct
> super_block *sb, void *d, int silent)
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0sb->s_op =3D &hostfs_sbop=
s;
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0sb->s_d_op =3D &simple_de=
ntry_operations;
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0sb->s_maxbytes =3D MAX_LF=
S_FILESIZE;
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0err =3D super_setup_bdi(sb);
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (err)
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0goto out;
> =C2=A0
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0/* NULL is printed as '(n=
ull)' by printf(): avoid that. */
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (req_root =3D=3D NULL)

--=20
Ritesh Raj Sarraf
Collabora

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