Re: Parted-2.3 can not detecte USB disk partition(SandDiak CRUZER SDCZ6-016G 16GB), but parted-1.8.8.

[Jim Meyering]

ChenMin wrote:
> THe model of USB disk is "SandDiak CRUZER SDCZ6-016G 16GB", and there
> is one signal partition on it.
>
> GNU Parted 2.3
> Using /dev/sde
> Welcome to GNU Parted! Type 'help' to view a list of commands.
> (parted) p
> Model: SanDisk Cruzer (scsi)
> Disk /dev/sde: 16.0GB
> Sector size (logical/physical): 512B/512B
> Partition Table: msdos
> Number  Start  End  Size  Type  File system  Flags
> (parted)
>
>
> GNU Parted 1.8.8
> Using /dev/sde
> Welcome to GNU Parted! Type 'help' to view a list of commands.
> (parted) p
> Model: SanDisk Cruzer (scsi)
> Disk /dev/sde: 16.0GB
> Sector size (logical/physical): 512B/512B
> Partition Table: loop
> Number  Start  End     Size    File system  Flags
>  1      0.00B  16.0GB  16.0GB  fat32
> (parted)

Thanks for reporting that regression.
I've reproduced it like this:

    $ dd if=/dev/null of=F bs=1 seek=40M
    $ mkfs.vfat -F 16 F
    $ parted -s F print
    Model:  (file)
    Disk /f12/home/meyering/w/co/parted/parted/F: 41.9MB
    Sector size (logical/physical): 512B/512B
    Partition Table: msdos

    Number  Start  End  Size  Type  File system  Flags

Note there is no partition listed above.
Repeating the final command using parted built with
the patch below, it works as expected:

    $ parted/parted -s F print|grep fat
     1      0.00B  41.9MB  41.9MB  fat16

I'll use something like the following patch,
once I've written a test:

>From 7167b646e82dd29372a0239bec0bc9053bae678b Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Wed, 14 Jul 2010 19:16:14 -0500
Subject: [PATCH] libparted: avoid regression when processing a whole-disk FAT 
partition

Without this change, we would improperly classify a whole-disk partition
containing a FAT file system as a DOS partition table with no partitions.
Introduced by commit d732a2b7 on 2008-05-28.
* libparted/labels/dos.c (maybe_FAT): New function.
(msdos_probe): Use it.
Reported by ChenMin in
http://thread.gmane.org/gmane.comp.gnu.parted.bugs/10115
---
 libparted/labels/dos.c |   75 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 75 insertions(+), 0 deletions(-)

diff --git a/libparted/labels/dos.c b/libparted/labels/dos.c
index f66ca47..d9e7d4a 100644
--- a/libparted/labels/dos.c
+++ b/libparted/labels/dos.c
@@ -164,6 +164,73 @@ typedef struct {

 static PedDiskType msdos_disk_type;

+#if 0
+From http://www.win.tue.nl/~aeb/linux/fs/fat/fat-1.html
+
+The 2-byte numbers are stored little endian (low order byte first).
+
+Here the FAT12 version, that is also the common part of the FAT12, FAT16 and 
FAT32 boot sectors. See further below.
+
+Bytes   Content
+0-2     Jump to bootstrap (E.g. eb 3c 90; on i86: JMP 003E NOP.
+        One finds either eb xx 90, or e9 xx xx.
+        The position of the bootstrap varies.)
+3-10    OEM name/version (E.g. "IBM  3.3", "IBM 20.0", "MSDOS5.0", "MSWIN4.0".
+        Various format utilities leave their own name, like "CH-FOR18".
+        Sometimes just garbage. Microsoft recommends "MSWIN4.1".)
+        /* BIOS Parameter Block starts here */
+11-12   Number of bytes per sector (512)
+        Must be one of 512, 1024, 2048, 4096.
+13      Number of sectors per cluster (1)
+        Must be one of 1, 2, 4, 8, 16, 32, 64, 128.
+        A cluster should have at most 32768 bytes. In rare cases 65536 is OK.
+14-15   Number of reserved sectors (1)
+        FAT12 and FAT16 use 1. FAT32 uses 32.
+16      Number of FAT copies (2)
+17-18   Number of root directory entries (224)
+        0 for FAT32. 512 is recommended for FAT16.
+19-20   Total number of sectors in the filesystem (2880)
+        (in case the partition is not FAT32 and smaller than 32 MB)
+21      Media descriptor type (f0: 1.4 MB floppy, f8: hard disk; see below)
+22-23   Number of sectors per FAT (9)
+        0 for FAT32.
+24-25   Number of sectors per track (12)
+26-27   Number of heads (2, for a double-sided diskette)
+28-29   Number of hidden sectors (0)
+        Hidden sectors are sectors preceding the partition.
+        /* BIOS Parameter Block ends here */
+30-509  Bootstrap
+510-511 Signature 55 aa
+#endif
+
+/* There is a significant risk of misclassifying (as msdos)
+   a disk that is composed solely of a single FAT partition.
+   Return false if sector S could not be a valid FAT boot sector.
+   Otherwise, return true.  */
+static bool
+maybe_FAT (unsigned char const *s)
+{
+  if (! (s[0] == 0xeb || s[0] == 0xe9))
+    return false;
+
+  unsigned int sector_size = PED_LE16_TO_CPU (*(uint16_t *) (s + 11));
+  switch (sector_size)
+    {
+    case 512:
+    case 1024:
+    case 2048:
+    case 4096:
+      break;
+    default:
+      return false;
+    }
+
+  if (! (s[21] == 0xf0 || s[21] == 0xf8))
+    return false;
+
+  return true;
+}
+
 static int
 msdos_probe (const PedDevice *dev)
 {
@@ -191,12 +258,20 @@ msdos_probe (const PedDevice *dev)
         * and ensure that each partition has a boot indicator that is
         * either 0 or 0x80.
         */
+       unsigned int n_active = 0;
        for (i = 0; i < DOS_N_PRI_PARTITIONS; i++) {
+               if (part_table->partitions[i].boot_ind == 0x80)
+                       ++n_active;
                if (part_table->partitions[i].boot_ind != 0
                    && part_table->partitions[i].boot_ind != 0x80)
                        goto probe_fail;
        }

+       /* If there are no active partitions and this is probably
+          a FAT file system, do not classify it as msdos.  */
+       if (n_active == 0 && maybe_FAT (label))
+         goto probe_fail;
+
        /* If this is a GPT disk, fail here */
        for (i = 0; i < DOS_N_PRI_PARTITIONS; i++) {
                if (part_table->partitions[i].type == PARTITION_GPT)
--
1.7.1.460.gf3c4c