Re: [PATCH 4/5] common/rc: fix scratch mount options for tmpfs

["Darrick J. Wong" <djwong@kernel.org>]

On Mon, Jun 24, 2024 at 01:50:33PM +0000, Daniel Gomez wrote:
> On Fri, Jun 14, 2024 at 08:47:28AM GMT, Darrick J. Wong wrote:
> > On Fri, Jun 14, 2024 at 06:17:25AM +0000, Daniel Gomez wrote:
> > > Make sure tmpfs scratch device inherits the extra tmpfs mount options
> > > variable (TMPFS_MOUNT_OPTIONS).
> > > 
> > > Signed-off-by: Daniel Gomez <da.gomez@samsung.com>
> > > ---
> > >  common/rc | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/common/rc b/common/rc
> > > index 7f995b0fa..a42792c37 100644
> > > --- a/common/rc
> > > +++ b/common/rc
> > > @@ -224,7 +224,7 @@ _test_options()
> > >  # hosted on $SCRATCH_DEV, so can't use external scratch devices).
> > >  _common_dev_mount_options()
> > >  {
> > > -	echo $MOUNT_OPTIONS $SELINUX_MOUNT_OPTIONS $*
> > > +	echo $MOUNT_OPTIONS $SELINUX_MOUNT_OPTIONS $TMPFS_MOUNT_OPTIONS $*
> > 
> > Why is it necessary to include tmpfs mount options for all fs types?
> > XFS does not accept tmpfs mount options.
> 
> You are right. We should not do this.
> 
> However, _scratch_mount_options() calls _common_dev_mount_options() ignoring the
> specific mount options based on fstyp.

Ah, _mount_opts only gets run for configuration files.

> specific mount options based on fstyp. Replacing it with _common_mount_opts()
> makes this work. In addition, _common_dev_mount_options() function description
> says 'Used for mounting non-scratch devices with the safe set of scratch mount
> options'. So, why is it used to mount scratch devices?

I think the comment isn't very good.  Six of the seven callers:

common/dmdelay|23| _mount -t $FSTYP `_common_dev_mount_options` $SCRATCH_OPTIONS \
common/dmdust|19| _mount -t $FSTYP `_common_dev_mount_options $*` $SCRATCH_OPTIONS \
common/dmerror|94| _mount -t $FSTYP `_common_dev_mount_options $*` $SCRATCH_OPTIONS \
common/dmlogwrites|107| _mount -t $FSTYP `_common_dev_mount_options $*` $SCRATCH_OPTIONS \
common/dmthin|226| echo `_common_dev_mount_options $*` $SCRATCH_OPTIONS $DMTHIN_VOL_DEV $SCRATCH_MNT
common/rc|272| echo `_common_dev_mount_options $*` $SCRATCH_OPTIONS \

appear to use this to mount the scratch filesystem from devices that are
not the regular scratch device.  The one exception is this one:

common/overlay|32| _mount -t overlay $diropts `_common_dev_mount_options $*`

which AFAICT seem to mount arbitrary overlayfs instances with some of
the mount options.

> This fixes the issue:
> 
> diff --git a/common/rc b/common/rc
> index 51827119c..627dbaaaa 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -231,8 +231,8 @@ _scratch_mount_options()
>  {
>         _scratch_options mount
> 
> -       echo `_common_dev_mount_options $*` $SCRATCH_OPTIONS \
> -                                       $SCRATCH_DEV $SCRATCH_MNT
> +       echo `_common_mount_opts` $SCRATCH_OPTIONS \
> +                                       $SCRATCH_DEV $SCRATCH_MNT $*
>  }
> 
> > 
> > For that matter, why is TMPFS_MOUNT_OPTIONS necessary at all?  Shouldn't
> > that simply be "MOUNT_OPTIONS=<stuff> FSTYP=tmpfs ./check" ?
> 
> TMPFS_MOUNT_OPTIONS is used to specify mount options in each section of the
> configuration file. For example, the following snippet is part of my conf file:
> 
> ```
> [tmpfs_noswap_huge_always]
> TMPFS_MOUNT_OPTIONS="-o noswap,huge=always"
> 
> [tmpfs_noswap_huge_within_size]
> TMPFS_MOUNT_OPTIONS="-o noswap,huge=within_size"
> ```
> 
> Then I run -s option to switch between profiles, e.g., 'check -s
> tmpfs_noswap_huge_within_size -R xunit -g auto'.
> 
> I’m not sure if this addresses your question. Please let me know if I
> misunderstood.

Ahah, this is one of those parts of fstests that differ depending on
whether you use configuration files (you do) or not (I don't).  AFAICT,
get_next_config has this slightly odd (to me) behavior where if a config
section doesn't explicitly set MOUNT_OPTIONS, it will reuse
MOUNT_OPTIONS from a previous section if FSTYP hasn't changed.  You
instead want to change the mount between sections

So I /think/ the correct thing to do here is

[tmpfs_noswap_huge_always]
MOUNT_OPTIONS="-o noswap,huge=always"

[tmpfs_noswap_huge_within_size]
MOUNT_OPTIONS="-o noswap,huge=within_size"

Though I'm not exactly an expert on these things.

--D

> 
> > 
> > --D
> > 
> > >  }
> > >  
> > >  _scratch_mount_options()
> > > -- 
> > > 2.43.0
> > >