On Tue, Dec 13, 2016 at 10:15:25AM -0600, Eric Sandeen wrote: > On 12/13/16 9:39 AM, Heinz Nimmervoll wrote: > > I still got no answer for my problem thats why I try it here... hopefully you could help me out. > > > > System: > > > > Embedded board with Atmel SAM9x25 > > Debian Wheezy Kernel 3.11.6 > > 32GB Samsung SDHC card with ext4 root- partition (journal activated) > > > > > > After system running two weeks or so superblock from rootfs (ext4) at block 0 got overwritten with "trash data". > > This is happening with like 20% of the embedded devices. > > > > hex comparision between faulty and good superblock starting at byte 1024: > > > > Before (good): > > > > 00000000 00 ee 02 00 00 b8 0b 00 00 96 00 00 ab a9 05 00 |................| > > 00000010 c3 0c 02 00 00 00 00 00 02 00 00 00 02 00 00 00 |................| > > 00000020 00 80 00 00 00 80 00 00 40 1f 00 00 9e 68 46 58 |........@....hFX| > > 00000030 9e 68 46 58 2e 00 64 00 53 ef 01 00 01 00 00 00 |.hFX..d.S.......| > > <snip> > > > > > After (corrupted): > > > > 00000000 00 00 00 00 a4 81 00 00 dd 00 00 00 24 8e 5d 54 |............$.]T| > > 00000010 7e 8e 5d 54 18 a6 9f 41 00 00 00 00 00 00 01 00 |~.]T...A........| > > 00000020 08 00 00 00 00 00 08 00 01 00 00 00 0a f3 01 00 |................| > > 00000030 04 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00 |................| 81a4? f30a? That looks like an inode block (i_mode 0x81a4) and an extent tree root (eh_magic 0xf30a), shifted up by 4 bytes before being written onto sector 0. > <snip> > > > - How is it possible, that even the magic number (and everything else) got overwritten? > > - Why could it ever be overwritten? > > I don't think anyone here can tell you what happened, it is almost certainly not > an ext4 bug. Could be a driver bug, or an admin running a stray "dd" command, > or some other utility gone astray, or ... anything, really. Bad/malicious SDHC card would be my guess? (Are you doing power fail testing?) --D > As a very long shot, what does "blkid" or "file -s" tell you about the block device > after it's been overwritten? Perhaps it will recognize a signature. > > Otherwise, you could do something like a modified kernel to trap any IO to block > zero on the device and issue a printk about the process which is doing it, filtering > out any expected ext4 accesses. > > -Eric > > > Thank you so much! > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
