On Thu, Sep 20, 2012 at 9:46 PM, Marc MERLIN [off-list ref] wrote:

On Thu, Sep 20, 2012 at 10:17:47AM -0700, Marc MERLIN wrote:

quoted

I had a btrfs built on top of 5 drives (dmcrypt devices).

The drive then died while I was writing to the filesystem and my system
crashed and rebooted:

[384555.534020] sd 10:0:0:0: rejecting I/O to offline device
[384555.535057] sd 10:0:0:0: rejecting I/O to offline device
[384556.666885] ------------[ cut here ]------------
[384556.667909] sd 10:0:0:0: [sdj] Synchronizing SCSI cache
[384556.677509] kernel BUG at fs/btrfs/ctree.c:3451!
[384556.682551] invalid opcode: 0000 [#1] PREEMPT SMP
[384556.687878] CPU 2

Oh my, now I'm trying again with a new drive, and a big cp from an
existing array to a new one dies with:
[32042.079411] ------------[ cut here ]------------
[32042.085799] kernel BUG at fs/btrfs/extent_io.c:1884!
[32042.092528] invalid opcode: 0000 [#1] PREEMPT SMP
[32042.099227] CPU 1
[32042.101095] Modules linked in:[32042.105950]  raid456 async_raid6_recov async
_pq raid6_pq async_xor xor async_memcpy async_tx ppdev lp tun autofs4 kl5kusb105
 ftdi_sio keyspan nfsd nfs lockd fscache auth_rpcgss nfs_acl sunrpc rc_ati_x10 s
nd_timer i915 usbserial snd drm_kms_helper eeepc_wmi drm ati_remote asus_wmi rc_
core sparse_keymap

    int repair_io_failure(struct btrfs_mapping_tree *map_tree, u64 start,
                            u64 length, u64 logical, struct page *page,
                            int mirror_num)
    {
            struct bio *bio;
            struct btrfs_device *dev;
            DECLARE_COMPLETION_ONSTACK(compl);
            u64 map_length = 0;
            u64 sector;
            struct btrfs_bio *bbio = NULL;
            int ret;

            BUG_ON(!mirror_num); <<<<<

This is more of a problem since I can't backup my filesystem (source is
ext4 and destination is btrfs).

Any suggestion on what went wrong here?

There should have been a stack trace as well as a couple other things,
can you post those as well please?