Bodo Eggert wrote:
> Change the root filesystem to tmpfs. Doing this makes having a system on
> tmpfs much easier, while allowing to discard the now unnecessary ramfs.
Thanks a lot!
> Having the rootfs on tmpfs allows to safely run e.g. a rescue system
> without using tricks. You might even include the rescue system into the
> kernel.
>
> 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 <[email protected]>
>
>
> 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 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.
> + default n
> + help
> + This replaces the ramfs used for unpacking the cpio images
> + with tmpfs, thereby allowing swapping these contents to disk and
> + adding size limit support.
> +
> + Side effect:
> + This is useful only if you don't plan on mounting a different
> + root filesystem. Therefore it will change the default of the
> + root= parameter to "rootfs".
> +
> + If unsure, say N
> +
> config HUGETLBFS
> bool "HugeTLB file system support"
> depends on X86 || IA64 || PPC64 || SPARC64 || SUPERH || BROKEN
> @@ -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?
> default y
> ---help---
> Ramfs is a file system which keeps all files in RAM. It allows
:
:
> 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).
> +}
> +
> +/*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.
> +
> +static struct file_system_type rootfs_fs_type = {
> + .name = "rootfs",
> + .get_sb = rootfs_get_sb,
> + .kill_sb = kill_litter_super,
> +};
> +
> +int __init init_rootfs(void)
> +{
> + if (init_inodecache())
> + panic("Can't initialize shm inode cache");
> + return register_filesystem(&rootfs_fs_type);
> +}
> +#endif
> +
> /*
> * shmem_zero_setup - setup a shared anonymous mapping
> *
Thanks!
--
Al
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