linux-kernel - Re: [PATCH 2/3][try 1] init: enable system-on-initramfs: root-on-tmpfs

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Message-Id: <200707262334.18999.a1426z@gawab.com>
Date:	Thu, 26 Jul 2007 23:34:18 +0300
From:	Al Boldi <a1426z@...ab.com>
To:	Bodo Eggert <7eggert@....de>
Cc:	linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
	akpm@...ux-foundation.org
Subject: Re: [PATCH 2/3][try 1] init: enable system-on-initramfs: root-on-tmpfs

 
What happened to this one?  Is it in -mm?


Thanks!

--
Al

Al Boldi wrote:
> Bodo Eggert wrote:
> > Al Boldi <a1426z@...ab.com> wrote:
> > > Bodo Eggert wrote:
> > >> This is a rework of Al Boldi's "[PATCH] initramfs: Allow rootfs to
> > >> use tmpfs instead of ramfs". All the fame belongs to him, the bugs
> > >> belong to me.
> > >
> > > Actually, my patch was a rework of John Zielinski's
> > > http://marc.info/?l=linux-kernel&m=107013630212011&w=4 patch, so the
> > > credit really goes to him.
> > >
> > >> Signed-Off-By: Bodo Eggert <7eggert@....de>
> > >>
> > >>
> > >> diff -Xdontdiff -pruN linux-2.6.22.base/fs/Kconfig
> > >> linux-2.6.22.tmpfsroot/fs/Kconfig --- linux-2.6.22.base/fs/Kconfig
> > >> 2007-07-12 14:05:16.000000000 +0200 +++
> > >> linux-2.6.22.tmpfsroot/fs/Kconfig 2007-07-12 15:10:09.000000000 +0200
> > >> @@ -989,6 +989,22 @@ config TMPFS_POSIX_ACL
> > >
> > > Setting this in fs/Kconfig is way to deep, and too far away from the
> > > initramfs Kconfig, which makes it obscure.
> >
> > If it were under general setup, you'd have to enter fs to select tmpfs,
> > enter general setup to replace ramfs, and re-enter fs to disable ramfs.
> > I consider making people do that to be an evil deed.
>
> That's easy to fix, just change "depends on" to "select" in Kconfig.
>
> > The current position is very convenient, ramfs is below tmpfs, and while
> > you go from top to the bottom, you can enable tmpfs,
> > tmpfs-replaces-ramfs and ramfs=n.
> >
> > >>           If you don't know what Access Control Lists are, say N.
> > >>
> > >> +config TMPFS_ROOT
> > >> +       bool "Use tmpfs instrad of ramfs for initramfs"
> > >
> > > Check typo.
> > >
> > >> +       depends on TMPFS
> > >
> > > Should probably depend on SHMEM too.
> >
> > Sounds reasonable.
> >
> > >> @@ -1003,7 +1019,7 @@ config HUGETLB_PAGE
> > >>         def_bool HUGETLBFS
> > >>
> > >>  config RAMFS
> > >> -       bool
> > >> +       bool "Ramfs file system support" if TMPFS_ROOT
> > >
> > > What's wrong with the original Kconfig of making this tristate?
> >
> > I tested =m, found it not to compile because of a nonexported __symbol
> > and decided it wasn't worth the effort of adding another export while
> > other people struggle to reduce their number.
>
> Ok.
>
> > >> diff -Xdontdiff -pruN linux-2.6.22.base/mm/shmem.c
> > >> linux-2.6.22.tmpfsroot/mm/shmem.c --- linux-2.6.22.base/mm/shmem.c
> > >> 2007-07-12 14:05:25.000000000 +0200 +++
> > >> linux-2.6.22.tmpfsroot/mm/shmem.c 2007-07-12 15:01:32.000000000 +0200
> > >> @@ -2369,6 +2369,8 @@ static void init_once(void *foo, struct
> > >>
> > >>  static int init_inodecache(void)
> > >>  {
> > >> +       if (shmem_inode_cachep)
> > >> +               return 0;
> > >>         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
> > >>                                 sizeof(struct shmem_inode_info),
> > >>                                 0, 0, init_once, NULL);
> > >> @@ -2582,6 +2584,34 @@ put_memory:
> > >>         return ERR_PTR(error);
> > >>  }
> > >>
> > >> +#ifdef CONFIG_TMPFS_ROOT
> > >> +static int rootfs_get_sb(struct file_system_type *fs_type,
> > >> +       int flags, const char *dev_name, void *data, struct vfsmount
> > >> *mnt) +{
> > >> +       return get_sb_nodev(fs_type, flags|MS_NOUSER, data,
> > >> shmem_fill_super, +                           mnt);
> > >
> > > Setting the MS_NOUSER flag will make this invisible to df (diskfree).
> >
> > Which is obviously a bad thing for my cause, but good if you'd boot a
> > normal system. Is there any way out?
>
> Just remove the MS_NOUSER flag.  Normal systems would want to umount it
> after pivoting, so it won't be visible then.
>
> > >> +}
> > >> +
> > >> +/*static struct super_block *rootfs_get_sb(struct file_system_type
> > >> *fs_type, +       int flags, const char *dev_name, void *data)
> > >> +{
> > >> +       return get_sb_single(fs_type, flags, data, shmem_fill_super);
> > >> +}*/
> > >
> > > You commented this out, probably asking for clarification:  IIRC, it's
> > > get_sb_single instead of get_sb_nodev, because tmpfs can be mounted
> > > more than once and thus needs to be reference counted.
> >
> > No, I had left it there accidentially. Your comment tells me it was ment
> > to happen.
>
> Thanks!
>
> --
> Al

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