From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764262AbXGNDTH (ORCPT ); Fri, 13 Jul 2007 23:19:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762920AbXGNDS5 (ORCPT ); Fri, 13 Jul 2007 23:18:57 -0400 Received: from [212.12.190.58] ([212.12.190.58]:33029 "EHLO raad.intranet" rhost-flags-FAIL-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1760587AbXGNDS4 (ORCPT ); Fri, 13 Jul 2007 23:18:56 -0400 From: Al Boldi To: linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3][try 1] init: enable system-on-initramfs: root-on-tmpfs Date: Sat, 14 Jul 2007 06:18:57 +0300 User-Agent: KMail/1.5 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200707140618.57354.a1426z@gawab.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org 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 <7eggert@gmx.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 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