Re: [PATCH] use tmpfs for rootfs v2

["Jeff Schroeder" <jeffschroed@gmail.com>]

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On Thu, Oct 16, 2008 at 10:39 AM, Bodo Eggert <7eggert@gmx.de> wrote:
> This patch allows chosing tmpfs instead of ramfs for the root filesystem.
> Having tmpfs is usefull for running systems from RAM, because it does not
> risk deadlocking the system and possibly allows swapping. Using tmpfs
> increases the kernel by 10 bytes on x86_64.
>
> Having tmpfs as the root filesystem allows you to get rid of the now unused
> ramfs and free some kernel memory. On my system, that's about 5198 bytes
> compared to having a ramfs root.
>
> Off cause you can mount tmpfs and move around the data, but this is slower
> (having to copy around the data), more error-prone and it uses more memory.
> Besides that, I don't see the point in explicitely doing the wrong thing
> and then having everybody fix it.
>
>
> Signed-off-by: Bodo Eggert <7eggert@gmx.de>
>
> ---
> Changes to v1: Include the change to the Makefile.
>
> Some numbers for my system: (from make and from size vmlinux)
>
> Setup is 10716 bytes (padded to 10752 bytes).
> System is 2659 kB
> text    data     bss     dec     hex filename
> 5341667  874212  562992 6778871  676ff7 vmlinux
>
> having TMPFS_IS_ROOT:
> Setup is 10716 bytes (padded to 10752 bytes).
> System is 2659 kB
> text    data     bss     dec     hex filename
> 5341677  874212  562992 6778881  677001 vmlinux
>    +10
>
> not having ramfs:
> Setup is 10716 bytes (padded to 10752 bytes).
> System is 2659 kB
> text    data     bss     dec     hex filename
> 5336733  873948  562992 6773673  675ba9 vmlinux
>  -4934    -264
>
>
>  fs/Kconfig       |   21 +++++++++++++++++++++
>  fs/Makefile      |    2 +-
>  fs/ramfs/inode.c |   39 +++++++++++++++++++++------------------
>  mm/shmem.c       |   26 ++++++++++++++++++++++++++
>  4 files changed, 69 insertions(+), 19 deletions(-)
>
> diff -pruNXdontdiff linux-2.6.27.2-numlock/fs/Kconfig linux-2.6.27.3-tmpfs/fs/Kconfig
> --- linux-2.6.27.2-numlock/fs/Kconfig   2008-10-10 13:18:34.000000000 +0200
> +++ linux-2.6.27.3-tmpfs/fs/Kconfig     2008-10-11 15:42:21.000000000 +0200
> @@ -953,6 +953,27 @@ config TMPFS_POSIX_ACL
>
>          If you don't know what Access Control Lists are, say N.
>
> +config TMPFS_ROOT
> +       bool "Use tmpfs instrad of ramfs for initramfs"
> +       depends on TMPFS && SHMEM
> +       default n
> +       help
> +         This replaces the ramfs used for unpacking the cpio images
> +         with tmpfs.
> +
> +         If unsure, say N
> +
> +config RAMFS
> +       bool "Ramfs file system support" if TMPFS_ROOT
> +       default y
> +       ---help---
> +         Ramfs is a file system which keeps all files in RAM. Unlike tmpfs,
> +         it cannot be swapped to disk, and it has the risk of deadlocking
> +         the system by using all memory.
> +
> +         Ramfs is used for booting the system and unpacking the cpio if
> +         TMPFS_ROOT is not set.
> +
>  config HUGETLBFS
>        bool "HugeTLB file system support"
>        depends on X86 || IA64 || PPC64 || SPARC64 || (SUPERH && MMU) || \
> diff -pruNXdontdiff linux-2.6.27.2-numlock/fs/ramfs/inode.c linux-2.6.27.3-tmpfs/fs/ramfs/inode.c
> --- linux-2.6.27.2-numlock/fs/ramfs/inode.c     2008-07-13 23:51:29.000000000 +0200
> +++ linux-2.6.27.3-tmpfs/fs/ramfs/inode.c       2008-10-11 15:50:03.000000000 +0200
> @@ -190,6 +190,13 @@ int ramfs_get_sb(struct file_system_type
>        return get_sb_nodev(fs_type, flags, data, ramfs_fill_super, mnt);
>  }
>
> +static struct file_system_type ramfs_fs_type = {
> +       .name           = "ramfs",
> +       .get_sb         = ramfs_get_sb,
> +       .kill_sb        = kill_litter_super,
> +};
> +
> +#ifndef 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)
>  {
> @@ -197,30 +204,12 @@ static int rootfs_get_sb(struct file_sys
>                            mnt);
>  }
>
> -static struct file_system_type ramfs_fs_type = {
> -       .name           = "ramfs",
> -       .get_sb         = ramfs_get_sb,
> -       .kill_sb        = kill_litter_super,
> -};
>  static struct file_system_type rootfs_fs_type = {
>        .name           = "rootfs",
>        .get_sb         = rootfs_get_sb,
>        .kill_sb        = kill_litter_super,
>  };
>
> -static int __init init_ramfs_fs(void)
> -{
> -       return register_filesystem(&ramfs_fs_type);
> -}
> -
> -static void __exit exit_ramfs_fs(void)
> -{
> -       unregister_filesystem(&ramfs_fs_type);
> -}
> -
> -module_init(init_ramfs_fs)
> -module_exit(exit_ramfs_fs)
> -
>  int __init init_rootfs(void)
>  {
>        int err;
> @@ -235,5 +224,19 @@ int __init init_rootfs(void)
>
>        return err;
>  }
> +#endif
> +
> +static int __init init_ramfs_fs(void)
> +{
> +       return register_filesystem(&ramfs_fs_type);
> +}
> +
> +static void __exit exit_ramfs_fs(void)
> +{
> +       unregister_filesystem(&ramfs_fs_type);
> +}
> +
> +module_init(init_ramfs_fs)
> +module_exit(exit_ramfs_fs)
>
>  MODULE_LICENSE("GPL");
> diff -pruNXdontdiff linux-2.6.27.2-numlock/mm/shmem.c linux-2.6.27.3-tmpfs/mm/shmem.c
> --- linux-2.6.27.2-numlock/mm/shmem.c   2008-10-10 13:18:47.000000000 +0200
> +++ linux-2.6.27.3-tmpfs/mm/shmem.c     2008-10-11 16:05:52.000000000 +0200
> @@ -2366,6 +2366,10 @@ static void init_once(void *foo)
>
>  static int init_inodecache(void)
>  {
> +#ifdef CONFIG_TMPFS_ROOT
> +       if (shmem_inode_cachep)
> +               return 0;
> +#endif
>        shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
>                                sizeof(struct shmem_inode_info),
>                                0, SLAB_PANIC, init_once);
> @@ -2583,6 +2587,28 @@ 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, data, shmem_fill_super, mnt);
> +}
> +
> +
> + 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
>  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
> diff -pruNXdontdiff linux-2.6.27.2-numlock/fs/Makefile linux-2.6.27.3-tmpfs/fs/Makefile
> --- linux-2.6.27.2-numlock/fs/Makefile  2008-10-16 19:25:20.000000000 +0200
> +++ linux-2.6.27.3-tmpfs/fs/Makefile    2008-10-16 19:24:00.000000000 +0200
> @@ -67,6 +67,7 @@ obj-$(CONFIG_PROFILING)               += dcookies.o
>  obj-$(CONFIG_DLM)              += dlm/
>
>  # Do not add any filesystems before this line
> +obj-$(CONFIG_RAMFS)             += ramfs/
>  obj-$(CONFIG_REISERFS_FS)      += reiserfs/
>  obj-$(CONFIG_EXT3_FS)          += ext3/ # Before ext2 so root fs can be ext3
>  obj-$(CONFIG_EXT4DEV_FS)       += ext4/ # Before ext2 so root fs can be ext4dev
> @@ -74,7 +75,6 @@ obj-$(CONFIG_JBD)             += jbd/
>  obj-$(CONFIG_JBD2)             += jbd2/
>  obj-$(CONFIG_EXT2_FS)          += ext2/
>  obj-$(CONFIG_CRAMFS)           += cramfs/
> -obj-y                          += ramfs/
>  obj-$(CONFIG_HUGETLBFS)                += hugetlbfs/
>  obj-$(CONFIG_CODA_FS)          += coda/
>  obj-$(CONFIG_MINIX_FS)         += minix/

Haven't gotten the hang of attaching patches inline using gmail yet.
Here is a patch ontop of the previous one that fixes whitespace problems
pointed out by checkpatch.pl. It is based on 2.7.27
3fa8749e584b55f1180411ab1b51117190bac1e5

It is also available here:
http://www.digitalprognosis.com/opensource/patches/linux-2.6/0001-Cleanup-the-whitespace-to-be-checkpatch-compliant.patch

-- 
Jeff Schroeder

Don't drink and derive, alcohol and analysis don't mix.
http://www.digitalprognosis.com

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From e1fe0b8129d1769c834bff4262bab356e8d444bb Mon Sep 17 00:00:00 2001
From: Jeff Schroeder <jeffschroeder@computer.org>
Date: Thu, 16 Oct 2008 13:47:20 -0700
Subject: [PATCH] Cleanup the whitespace to be checkpatch compliant

Applies ontop of: http://lkml.org/lkml/diff/2008/10/16/388/1
Signed-off-by: Jeff Schroeder <jeffschroeder@computer.org>
---
 mm/shmem.c |   30 +++++++++++++++---------------
 1 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index a1d2042..d1b3cd8 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2594,21 +2594,21 @@ static int rootfs_get_sb(struct file_system_type *fs_type,
 	return get_sb_nodev(fs_type, flags, data, shmem_fill_super, mnt);
 }
 
- 
- 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
- 
+
+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
  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
-- 
1.5.4.3