fs/sysv/super.c: add support for non-PDP11 v7 filesystems

This adds byte order autodetection (of PDP-11 and LE filesystems).  No
attempt is made to detect big-endian filesystems -- were there any?
Tested with PDP-11 v7 filesystems and PC-IX maintenance floppy.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 51 insertions, 24 deletions

diff --git a/fs/sysv/super.c b/fs/sysv/super.c
index 3785262b98e0..85359a8df605 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"
 
 /*
@@ -434,12 +435,46 @@ 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 */
+        bh2 = sb_bread(sb, 2);
+        if (bh2 == 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");
@@ -453,7 +488,6 @@ 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);
@@ -465,34 +499,27 @@ 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(KERN_ERR "VFS: could not find a valid V7 on %s.\n",
+                sb->s_id);
         brelse(bh);
         kfree(sbi);
         return -EINVAL;