On Thu, Mar 15, 2018 at 07:55:42PM +0100, Christoph Biedl wrote: > Greg Kroah-Hartman wrote... > > > 4.14-stable review patch. If anyone has any objections, please let me know. > > > commit 3c181c12c431fe33b669410d663beb9cceefcd1b upstream. > (...) > > > If the filesystem is always used on a same endian host, this will not > > be a problem. > > >From my observations I cannot quite subscribe to that. > > On big-endian systems, this change intruduces severe corruption, > resulting in complete loss of the data on the used block device. > > Steps to reproduce (tested on ppc/powerpc and parisc/hppa): > > # mkfs.btrfs $DEV > # mount $DEV /mnt/tmp/ > # umount /mnt/tmp/ > > This simple umount corrupts the file system: > > # mount $DEV /mnt/tmp/ > mount: /mnt/tmp: wrong fs type, bad option, bad superblock on $DEV, missing codepage or helper program, or other error. > > # dmesg: > BTRFS critical (device <dev>): unable to find logical 4294967296 length 4096 > BTRFS critical (device <dev>): unable to find logical 4294967296 length 4096 > BTRFS critical (device <dev>): unable to find logical 18102363734671360 length 16384 > BTRFS error (device <dev>): failed to read chunk root > BTRFS error (device <dev>): open_ctree failed > > Also fsck is of no help: > > # btrfsck $DEV > Couldn't map the block 18102363734671360 > No mapping for 18102363734671360-18102363734687744 > Couldn't map the block 18102363734671360 > bytenr mismatch, want=18102363734671360, have=0 > ERROR: cannot read chunk root > ERROR: cannot open file system > > > Trying mount or fsck on a little-endian system does not help either. So > I consider the data on that device lost - luckily I use btrfs only for > files where a backup exists all the time. > > > Reverting that change restored the previous error-free behaviour. I > didn't check HEAD, i.e. v4.16-rc5, since the upstream commt was the last > that affected these files. Still I could give this a try if anybody > wishes so. That sucks. Can you test Linus's tree to verify the problem is there? I'll gladly revert this if Linus's tree also gets the revert, I don't want you to hit this when you upgrade to a newer kernel. thanks, greg k-h