On Feb 28, 2008 13:32 +0100, Frank Seidel wrote:
> i received a complaint that some FAT formated medias
> (e.g. sd memory cards) trigger a "unknown partition table" message even though
> there is no partition table and they work correctly, while in general
> (when e.g. formated with mkdosfs or even Windows Vista) this message is not
> shown.
> Currently this seems only to happen when the medias get formatted with
> Windows XP (and possibly Win 2000). Then the boot indicator byte contains
> garbage (part of text message) and so do the other parts checked by
> msdos_paritition which then later triggers this message.
>
> Would the patch below be appropriate to solve this issue/calm those users?
> It works ok here for the medias i could test.
There is also a similar complaint from users who format ext3 directly on
a disk/LUN without a partition table, because the partition table offset
negatively impacts the performance of the filesystem (causing unaligned
IO on a RAID device). Turning off this message is very good.
> ---
> From: Frank Seidel <fseidel@xxxxxxx>
> Subject: detect fat media without partition table correctly
> References: novell bug #364365
>
> Most fat formatted media without partition table contains
> zeros in the boot indication and the other tested bytes
> and so falls through the checks in msdos_partition, leading
> it to return with 1 (all is fine).
> But some (e.g. WinXP formatted) fat fomated medias don't
> use boot_ind and so the check fails and causes a
> "unkown partition table" warning eventhough there is none
> and everything would be fine.
> This additional check directly verifies if there is a
> fat formatted medium without a partition table.
>
> Signed-off-by: Frank Seidel <fseidel@xxxxxxx>
> ---
> fs/partitions/msdos.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> --- a/fs/partitions/msdos.c
> +++ b/fs/partitions/msdos.c
> @@ -18,7 +18,7 @@
> *
> * Re-organised Feb 1998 Russell King
> */
> -
> +#include <linux/msdos_fs.h>
>
> #include "check.h"
> #include "msdos.h"
> @@ -419,6 +419,7 @@ int msdos_partition(struct parsed_partit
> Sector sect;
> unsigned char *data;
> struct partition *p;
> + struct fat_boot_sector *fb;
> int slot;
>
> data = read_dev_sector(bdev, 0, §);
> @@ -441,6 +442,12 @@ int msdos_partition(struct parsed_partit
> * partition table. Reject this in case the boot indicator
> * is not 0 or 0x80.
> */
> + fb = (struct fat_boot_sector *) data;
> + if (fb->reserved && fb->fats && FAT_VALID_MEDIA(fb->media)) {
> + printk("\n");
> + put_dev_sector(sect);
> + return 1;
> + }
> p = (struct partition *) (data + 0x1be);
> for (slot = 1; slot <= 4; slot++, p++) {
> if (p->boot_ind != 0 && p->boot_ind != 0x80) {
> -
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Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.
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