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From: Lubomir Rintel on 25 Jul 2010 19:00
A mount-time option was added that makes it possible to override the
endianness and an attempt is made to autodetect it (which seems easy,
given the disk addresses are 3-byte.

No attempt is made to detect big-endian filesystems -- were there any?
Tested with PDP-11 v7 filesystems and PC-IX maintenance floppy.

Cc: Christoph Hellwig <hch(a)lst.de>
Cc: Al Viro <viro(a)ZenIV.linux.org.uk>
Signed-off-by: Lubomir Rintel <lkundrak(a)v3.sk>
---
fs/sysv/super.c | 74 +++++++++++++++++++++++++++++++++++++------------------
1 files changed, 50 insertions(+), 24 deletions(-)

diff --git a/fs/sysv/super.c b/fs/sysv/super.c
index ac7b008..0433f23 100644
--- a/fs/sysv/super.c
+++ b/fs/sysv/super.c
@@ -24,6 +24,7 @@
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/buffer_head.h>
+#include <linux/parser.h>
#include "sysv.h"

/*
@@ -435,12 +436,46 @@ Ebadsize:
goto failed;
}

-static int v7_fill_super(struct super_block *sb, void *data, int silent)
+static int v7_sanity_check(struct super_block *sb, struct buffer_head *bh)
{
- struct sysv_sb_info *sbi;
- struct buffer_head *bh, *bh2 = NULL;
struct v7_super_block *v7sb;
struct sysv_inode *v7i;
+ struct buffer_head *bh2;
+ struct sysv_sb_info *sbi;
+
+ sbi = sb->s_fs_info;
+
+ /* plausibility check on superblock */
+ v7sb = (struct v7_super_block *) bh->b_data;
+ if (fs16_to_cpu(sbi, v7sb->s_nfree) > V7_NICFREE ||
+ fs16_to_cpu(sbi, v7sb->s_ninode) > V7_NICINOD ||
+ fs32_to_cpu(sbi, v7sb->s_fsize) > V7_MAXSIZE)
+ return 0;
+
+ /* plausibility check on root inode: it is a directory,
+ with a nonzero size that is a multiple of 16 */
+ if ((bh2 = sb_bread(sb, 2)) == NULL) {
+ return 0;
+ }
+
+ v7i = (struct sysv_inode *)(bh2->b_data + 64);
+ if ((fs16_to_cpu(sbi, v7i->i_mode) & ~0777) != S_IFDIR ||
+ (fs32_to_cpu(sbi, v7i->i_size) == 0) ||
+ (fs32_to_cpu(sbi, v7i->i_size) & 017) ||
+ (fs32_to_cpu(sbi, v7i->i_size) > V7_NFILES *
+ sizeof (struct sysv_dir_entry))) {
+ brelse(bh2);
+ return 0;
+ }
+
+ brelse(bh2);
+ return 1;
+}
+
+static int v7_fill_super(struct super_block *sb, void *data, int silent)
+{
+ struct sysv_sb_info *sbi;
+ struct buffer_head *bh;

if (440 != sizeof (struct v7_super_block))
panic("V7 FS: bad super-block size");
@@ -454,7 +489,6 @@ static int v7_fill_super(struct super_block *sb, void *data, int silent)
sbi->s_sb = sb;
sbi->s_block_base = 0;
sbi->s_type = FSTYPE_V7;
- sbi->s_bytesex = BYTESEX_PDP;
sb->s_fs_info = sbi;

sb_set_blocksize(sb, 512);
@@ -466,34 +500,26 @@ static int v7_fill_super(struct super_block *sb, void *data, int silent)
goto failed;
}

- /* plausibility check on superblock */
- v7sb = (struct v7_super_block *) bh->b_data;
- if (fs16_to_cpu(sbi, v7sb->s_nfree) > V7_NICFREE ||
- fs16_to_cpu(sbi, v7sb->s_ninode) > V7_NICINOD ||
- fs32_to_cpu(sbi, v7sb->s_fsize) > V7_MAXSIZE)
- goto failed;
+ /* Try PDP-11 UNIX */
+ sbi->s_bytesex = BYTESEX_PDP;
+ if (v7_sanity_check (sb, bh))
+ goto detected;

- /* plausibility check on root inode: it is a directory,
- with a nonzero size that is a multiple of 16 */
- if ((bh2 = sb_bread(sb, 2)) == NULL)
- goto failed;
- v7i = (struct sysv_inode *)(bh2->b_data + 64);
- if ((fs16_to_cpu(sbi, v7i->i_mode) & ~0777) != S_IFDIR ||
- (fs32_to_cpu(sbi, v7i->i_size) == 0) ||
- (fs32_to_cpu(sbi, v7i->i_size) & 017) ||
- (fs32_to_cpu(sbi, v7i->i_size) > V7_NFILES *
- sizeof (struct sysv_dir_entry)))
- goto failed;
- brelse(bh2);
- bh2 = NULL;
+ /* Try PC/IX, v7/x86 */
+ sbi->s_bytesex = BYTESEX_LE;
+ if (v7_sanity_check (sb, bh))
+ goto detected;

+ goto failed;
+
+detected:
sbi->s_bh1 = bh;
sbi->s_bh2 = bh;
if (complete_read_super(sb, silent, 1))
return 0;

failed:
- brelse(bh2);
+ printk("VFS: could not find a valid V7 on %s.\n", sb->s_id);
brelse(bh);
kfree(sbi);
return -EINVAL;
--
1.7.2

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