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Date: Thu, 16 Oct 2008 14:03:06 -0700
From: "Jeff Schroeder" <jeffschroed@...il.com>
To: "Bodo Eggert" <7eggert@....de>
Cc: "Geert Uytterhoeven" <geert@...ux-m68k.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] use tmpfs for rootfs v2
On Thu, Oct 16, 2008 at 10:39 AM, Bodo Eggert <7eggert@....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@....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
View attachment "0001-Cleanup-the-whitespace-to-be-checkpatch-compliant.patch" of type "text/x-diff" (1469 bytes)
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