Joey Boggs wrote this to me:
> Been working on an issue with device-mapper/parted for RHEV-H's
> upstream project just not sure where the fault possibly lies.
>
> I'm specifically working on adding efi support to the installation
> drive, which involves creating a specific partition on the disk and
> marking with the boot flag. /dev/mapper device names are used where
> available for all available devices including local sata/ide/scsi
>
> Typical Installer parted steps in order for ovirt-node/RHEV-H
> parted -s /dev/mapper/XXXXX "mklabel gpt"
> parted -s /dev/mapper/XXXXX "mkpart efi 0M 256M"
> parted -s /dev/mapper/XXXXX "mkpart primary 256M 512M"
> parted -s /dev/mapper/XXXXX "mkpart primary 512M 768M"
> mkfs.vfat /dev/mapper/XXXXp1 -n EFI
> mke2fs /dev/mapper/XXXXp2 -L Root
> mke2fs /dev/mapper/XXXXp3 -L RootBackup
> The created efi partition is fine up to this point and can be
> mounted/unmounted freely
> When adding a fourth and final partition we run into an issue.
> parted -s /dev/mapper/XXXXX "mkpart efi 768M -1" is ran for the last
> partition used for lvm
> # this step erases/corrupts the vfat file system(unable to mount)
> somehow easily reproduced by adding a 4th partition no matter the size
> with parted
>
> Any ideas what could possibly be happening to corrupt that file system
> or write to a part of the disk incorrectly within parted?
>
> Using RHEL6.2 based parted/device-mapper this completes fine but there
> is a major version difference with parted
>
> Fedora 16 Versions
> parted 3.0.4
> device-mapper 1.02-65-5
>
> RHEL6.2 Versions
> parted 2.1.17
> device-mapper 1.02-66-6
Hi Joey,
Thanks for the report.
I first tried to reproduce that on F16 using a regular scsi device:
---------------------------------
modprobe scsi_debug dev_size_mb=1000
dev=/dev/sdd
parted -s $dev mklabel gpt
mkpart efi 0M 256M
mkpart root 256M 512M
mkpart roo2 512M 768M
That worked fine. I.e., no error, no reproducer.
Starting to think that this is somehow DM-specific.
Try again, but now using DM:
(testing via "mount" is not reliable --
instead, let's just compare first the sector, pre/post)
---------------------------------
This is surely a bug, but where?
Creating the 4th partition should not affect contents of first.
$ parted -s $dev u s p
Model: Linux device-mapper (linear) (dm)
Disk /dev/mapper/barz: 2097152s
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Number Start End Size File system Name Flags
1 34s 500000s 499967s fat16 efi
2 500001s 1000000s 500000s ext2 p1
3 1000001s 1500000s 500000s ext2 p2
4 1500001s 2095199s 595199s data
I straced the parted invocation that added the 4th partition,
and the only two write syscalls were the ones I expected:
to rewrite the 32 sectors at beginning and end of the disk.
================================================== ====
retry with DM and trivially small partitions
cd /tmp; truncate -s 10m g && loop=$(losetup --show -f g)
echo 0 100 linear $loop 0 | dmsetup create zub
dev=/dev/mapper/zub
parted -s $dev
mklabel gpt
mkpart efi 34s 34s
mkpart root 35s 35s
mkpart roo2 36s 36s
u s p
# Same problem: something modifies the 35th sector, and in this case,
# clears it: that cmp shows random bits on the LHS and all 0 bytes on
# the RHS.
$ parted -s $dev u s p
Model: Linux device-mapper (linear) (dm)
Disk /dev/mapper/zub: 100s
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Number Start End Size File system Name Flags
1 34s 34s 1s efi
2 35s 35s 1s root
3 36s 36s 1s roo2
4 37s 37s 1s p4
I'll investigate more tomorrow.
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01-17-2012, 11:38 PM
Alasdair G Kergon
parted issue/question
Try
blkdev --flushbufs
after any cmd that writes to a dev to see if that makes any difference.
Alasdair
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parted issue/question
