Hey all.
I'm going through the kernel source for XFS and I'm trying to find out
how many superblocks a partition usually has and the maximum it's
allowed to have. So far in xfs_mount.h, I'm seeing that we are allowed
two superblocks. I am proposing that we have two consecutive primary
superblocks (duplicates) in use. In other words, mirrored blocks.
So, if lilo or any other boot loader comes along and overwrites a part
of the first superblock, the mounting code can still get at the 2nd sb.
But, the problem is that the size of the superblock I've seen varies
from 512 bytes to 65535 bytes. In lilo's sources, we got blocks of size
1024 and sector sizes of 512. Any ideas on what to do on this?
On Mon, 2002-03-25 at 16:52, Derek James Witt wrote:
> Hi, Eric. Thanks for the suggestion. That made it cleaner. Here's the
> new patch.
>
> On Mon, 2002-03-25 at 15:53, Eric Sandeen wrote:
> > hi Derek -
> >
> > Rather than parsing /etc/mtab, it would probably be better to look for
> > "XFSB" in the first 4 bytes of the target partition - that way you
> > _know_ the target has (or has had....) an xfs filesystem on it.
> >
> > -Eric
> >
> > --
> > Eric Sandeen XFS for Linux http://oss.sgi.com/projects/xfs
> > sandeen@sgi.com SGI, Inc.
> --
> ** Derek J Witt **
> * Email: mailto:djw@flinthills.com *
> * Home Page: http://www.flinthills.com/~djw/ *
> *** "...and on the eighth day, God met Bill Gates." - Unknown **
> ----
>
> --- lilo.c Sun Dec 30 16:10:26 2001
> +++ ../lilo-xfs.c Mon Mar 25 16:43:40 2002
> @@ -755,16 +755,40 @@
> fprintf(errstd,"%7s%s -A /dev/XXX [ N ]\t\tactivate a partition\n","",name);
> fprintf(errstd,"%7s%s -M /dev/XXX [ mbr_file ]\tinstall master boot record\n","",name);
> fprintf(errstd,"%7s%s -T help \t\t\tlist additional options\n", "", name);
> + fprintf(errstd,"%7s%s -F \t\t\t\tforce install on XFS partition\n\t\t\t\t\tWARNING: This will corrupt\n\t\t\t\t\tthe superblock on XFS partitions.\n\n", "", name);
> fprintf(errstd,"%7s%s -V [ -v ]\t\t\tversion information\n\n","",name);
> exit(1);
> }
>
>
> +int is_xfs(char* device)
> +{
> + FILE* mounts;
> + unsigned char xfs_sig[] = {'X','F','S','B'};
> + int got_xfs = 1, i;
> +
> + if ((mounts = fopen(device, "rb")) == NULL)
> + { /* Just some insurance. If this does not exists, there's something
> + seriously wrong here. How are you even in Linux in the first place?
> + */
> + die("ERROR: I cannot find %s! Nothing done.\n",device);
> + }
> +
> + for (i = 0; (i < 4) && (got_xfs == 1); i++)
> + if (xfs_sig[i] == fgetc(mounts)) got_xfs = 1; else got_xfs = 0;
> +
> + fclose(mounts);
> +
> + return got_xfs;
> +}
> +
> int main(int argc,char **argv)
> {
> char *name,*reboot_arg,*identify,*ident_opt,*new_root;
> char *tell_param, *uninst_dev, *param, *act1, *act2, ch;
> int query,more,version,uninstall,validate,activate,instmbr,geom;
> + int force_xfs;
> + char *boot_device = NULL;
> struct stat st;
> int fd;
> long raid_offset;
> @@ -775,6 +799,7 @@
> reboot_arg = identify = ident_opt = new_root = uninst_dev = NULL;
> lowest = do_md_install = zflag =
> query = version = uninstall = validate = activate = instmbr = 0;
> + force_xfs = 0;
> verbose = -1;
> name = *argv;
> argc--;
> @@ -806,6 +831,8 @@
> break;
> case 'b':
> cfg_set(cf_options,"boot",param,NULL);
> + boot_device = (char*)malloc((sizeof (char)) * 255);
> + strcpy(boot_device,param);
> break;
> case 'c':
> cfg_set(cf_options,"compact",NULL,NULL);
> @@ -823,6 +850,11 @@
> case 'f':
> cfg_set(cf_options,"disktab",param,NULL);
> break;
> + case 'F':
> + if (!nowarn)
> + fprintf(errstd,"WARNING: Forcing install on XFS partitions...\nBe prepared to run xfs_repair\non any XFS root partitions\nthat LILO selects as boot.\n");
> + force_xfs = 1;
> + break;
> case 'g':
> geometric |= 1;
> break;
> @@ -1104,6 +1136,13 @@
> if (verbose >=2 && do_md_install)
> printf("raid flags: at bsect_open 0x%02X\n", raid_flags);
>
> + if (boot_device == NULL)
> + {
> + boot_device = (char*)malloc((sizeof (char)) * 255);
> + strcpy(boot_device,cfg_get_strg(cf_options,"boot"));
> + }
> + if ((is_xfs(boot_device) == 1) && (force_xfs == 0)) die("root (%s) is XFS. Aborted.",boot_device);
> +
> bsect_open(cfg_get_strg(cf_options,"boot"),cfg_get_strg(cf_options,"map") ?
> cfg_get_strg(cf_options,"map") : MAP_FILE,cfg_get_strg(cf_options,
> "install"),cfg_get_strg(cf_options,"delay") ? to_number(cfg_get_strg(
--
** Derek J Witt **
* Email: mailto:djw@flinthills.com *
* Home Page: http://www.flinthills.com/~djw/ *
*** "...and on the eighth day, God met Bill Gates." - Unknown **
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