* Matteo Croce <technoboy85@xxxxxxxxx>: > 2014-07-02 12:17 GMT+02:00 David Jander <david@xxxxxxxxxxx>: > > > > Hi Eric, > > > > On Tue, 1 Jul 2014 12:36:46 -0400 > > Eric Whitney <enwlinux@xxxxxxxxx> wrote: > > > >> * Theodore Ts'o <tytso@xxxxxxx>: > >> > On Tue, Jul 01, 2014 at 09:07:27PM +0900, Jaehoon Chung wrote: > >> > > Hi, > >> > > > >> > > i have interesting for this problem..Because i also found the same problem.. > >> > > Is it Journal problem? > >> > > > >> > > I used the Linux version 3.16.0-rc3. > >> > > > >> > > [ 3.866449] EXT4-fs error (device mmcblk0p13): ext4_mb_generate_buddy:756: group 0, 20490 clusters in bitmap, 20488 in gd; block bitmap corrupt. > >> > > [ 3.877937] Aborting journal on device mmcblk0p13-8. > >> > > [ 3.885025] Kernel panic - not syncing: EXT4-fs (device mmcblk0p13): panic forced after error > >> > > >> > This message means that the file system has detected an inconsistency > >> > --- specifically, that the number of blocks marked as in use in the > >> > allocation bbitmap is different from what is in the block group > >> > descriptors. > >> > > >> > The file system has been marked to force a panic after an error, at > >> > which point e2fsck will be able to repair the inconsistency. > >> > > >> > What's not clear is *how* the why this happened. It can happen simply > >> > because of a hardware problem. (In particular, not all mmc flash > >> > devices handle power failures gracefully.) Or it could be a cosmic, > >> > ray, or it might be a kernel bug. > >> > > >> > Normally I would chalk this up to a hardware bug, bug it's possible > >> > that it is a kernel bug. If people can reliably reproduce the problem > >> > where no power failures or other unclean shutdowns were involved > >> > (since the last time file system has been checked using e2fsck) then > >> > that would be realy interesting. > >> > >> Hi Ted: > >> > >> I saw a similar failure during 3.16-rc3 (plus ext4 stable fixes plus msync > >> patch) regression on the Pandaboard this morning. A generic/068 hang > >> on data_journal required a reboot for recovery (old bug, though rarer lately). > >> On reboot, the root filesystem - default 4K, and on an SD card - went ro > >> after the same sort of bad block bitmap / journal abort sequence. Rebooting > >> forced a fsck that cleared up the problem. The target test filesystem was on > >> a USB-attached disk, and it did not exhibit the same problems on recovery. > > > > Please be careful about conclusions from regular SD cards and USB sticks for > > mass-storage. Unlike hardened eMMC (4.41+), these COTS mass-storage devices > > are not meant for intensive use and can perfectly easily corrupt data out of > > themselves. I've seen it happening many times already. > > > >> So, it looks like there might be more than just hardware involved here, > >> although eMMC/flash might be a common denominator. I'll see if I can come up > >> with a reliable reproducer once the regression pass is finished if someone > >> doesn't beat me to it. I've not found a reproducer that doesn't involve an unclean shutdown, which is what Ted's looking for. However, I've noted a behavioral change that might be of interest with the failure scenario described above using xfstests generic/068 that occurred between 3.14 and 3.15-rc3. It's possible that this change would make filesystem damage caused by an unclean shutdown more likely or more noticable, and perhaps it's in play for the power fail/cycle cases described in this thread. FWIW, I've also been able to reproduce that failure scenario on an x86_64 KVM with raw virtio disks alone. It's just a lot harder to get there with that configuration - many more trials required. The change is that the root filesystem sustains damage reported as - EXT4-fs error (device mmcblk0p3): ext4_mb_generate_buddy:757: group 65, 1243 clusters in bitmap, 1244 in gd; block bitmap corrupt. Aborting journal on device mmcblk0p3-8. EXT4-fs error (device mmcblk0p3): ext4_journal_check_start:56: Detected aborted journal EXT4-fs (mmcblk0p3): Remounting filesystem read-only - when generic/068 is run on a separate test filesystem that forces an ext4 failure requiring a power cycle / reset to recover from a hung reboot attempt. This doesn't happen in 3.14 on either my x86_64 or ARM test systems. Generally, the root filesystem doesn't appear to be affected at all or is minimally affected (does not require fsck to fully recover) in 3.14, whereas a fsck is usually required to recover the root in 3.15-rc3. My attempts to bisect further into 3.15-rc1 to 3.15-rc3 haven't gone well as yet - other kernel problems are making it difficult to work in there. Eric > > > > I agree that there is a strong correlation towards flash-based storage, but I > > cannot explain why this factor would make a difference. How are flash-based > > block-devices different to ext4 than spinning-disk media (besides trim > > support)? > > maybe the zero access time can trigger some race condition? > > > Best regards, > > > > -- > > David Jander > > Protonic Holland. > > > > -- > Matteo Croce > OpenWrt Developer -- 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
