[PATCH] relax check for AIX in msdos partition table

The patch to identify AIX disks and ignore them has caused at least one
machine to fail to find the root partition on 2.6.19. The patch is:

http://lkml.org/lkml/2006/7/31/117

The problem is some disk formatters do not blow away the first 4 bytes
of the disk. If the disk we are installing to used to have AIX on it,
then the first 4 bytes will still have IBMA in EBCDIC.

The install in question was debian etch. Im not sure what the best fix
is, perhaps the AIX detection code could check more than the first 4
bytes.

The whole partition info for primary partitions is in this block:

  dd if=/dev/sdb count=$(( 4 * 16 )) bs=1 skip=$(( 0x1be ))

All other data do not matter, beside the 0x55aa marker at the end of the
first block.

Signed-off-by: Olaf Hering <olh@suse.de>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/partitions/msdos.c b/fs/partitions/msdos.c
index 8c7af1777819e2b2d5cdeabc49ef87298ca89c19..dafd3b6b2dc3301be1c03946bfaf0dfd5e6a9f0f 100644 (file)
--- a/fs/partitions/msdos.c
+++ b/fs/partitions/msdos.c
@@ -63,15 +63,25 @@ msdos_magic_present(unsigned char *p)
 #define AIX_LABEL_MAGIC4       0xC1
 static int aix_magic_present(unsigned char *p, struct block_device *bdev)
 {
+       struct partition *pt = (struct partition *) (p + 0x1be);
        Sector sect;
        unsigned char *d;
-       int ret = 0;
+       int slot, ret = 0;
 
        if (p[0] != AIX_LABEL_MAGIC1 &&
                p[1] != AIX_LABEL_MAGIC2 &&
                p[2] != AIX_LABEL_MAGIC3 &&
                p[3] != AIX_LABEL_MAGIC4)
                return 0;
+       /* Assume the partition table is valid if Linux partitions exists */
+       for (slot = 1; slot <= 4; slot++, pt++) {
+               if (pt->sys_ind == LINUX_SWAP_PARTITION ||
+                       pt->sys_ind == LINUX_RAID_PARTITION ||
+                       pt->sys_ind == LINUX_DATA_PARTITION ||
+                       pt->sys_ind == LINUX_LVM_PARTITION ||
+                       is_extended_partition(pt))
+                       return 0;
+       }
        d = read_dev_sector(bdev, 7, &sect);
        if (d) {
                if (d[0] == '_' && d[1] == 'L' && d[2] == 'V' && d[3] == 'M')

diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 0a022b2f63fc0fa95fa35df16784e2fcaef225b3..7a566fad3f72f72a4ae6f350049536538c7df0cf 100644 (file)
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -21,6 +21,8 @@ enum {
        WIN98_EXTENDED_PARTITION = 0x0f,
 
        LINUX_SWAP_PARTITION = 0x82,
+       LINUX_DATA_PARTITION = 0x83,
+       LINUX_LVM_PARTITION = 0x8e,
        LINUX_RAID_PARTITION = 0xfd,    /* autodetect RAID partition */
 
        SOLARIS_X86_PARTITION = LINUX_SWAP_PARTITION,