On Tue, Nov 29, 2011 at 01:12:14PM -0500, Chris Mason wrote:
> > Nov 28 00:11:14 karl-workstation kernel: [212918.235050] kernel BUG at
> > /home/apw/COD/linux/fs/btrfs/extent-tree.c:4775!
> > Nov 28 00:11:14 karl-workstation kernel: [212918.235118] RAX:
> > 00000000ea000001 RBX: ffff880412c3ab40 RCX: ffff880380173900
> > ^^^^^^^^^^^^^^^^
> >
> > 4765 ret = btrfs_search_slot(trans, extent_root,
> > 4766 &key, path, -1, 1);
> > 4767 if (ret) {
> > 4768 printk(KERN_ERR "umm, got %d back from search"
> > 4769 ", was looking for %llu\n", ret,
> > 4770 (unsigned long long)bytenr);
> > 4771 if (ret > 0)
> > 4772 btrfs_print_leaf(extent_root,
> > 4773 path->nodes[0]);
> > 4774 }
> > 4775 BUG_ON(ret);
> >
> > the ret value comes from btrfs_search_slot, returning " < 0" or 1, but
> > RAX has some extra bits set, this could really be a RAM failure.
>
> Interesting, look at this:
>
> > karl@karl-precise:~/git/btrfs-progs$ sudo ./btrfsck /dev/md0
> > ref mismatch on [2176962560 8192] extent item 480, found 1
> > Incorrect local backref count on 2176970752 root 5 owner 2101705
> > offset 368640 found 1 wanted 3925868545
> > backpointer mismatch on [2176970752 4096]
>
> 3925868545 == EA000001
I applied usual first analysis steps (source line, registers, call
chain), search slot could return 1 and taking a memory failure into
account looks possible, though bit count of 'EA' is 5, seems too high.
> Are you sure this is the BUG_ON he was triggering?
This was referring to the second BUG_ON in the logs. I checked the first
BUG_ON again and see:
kernel: [ 100.963478] kernel BUG at
/build/buildd/linux-3.2.0/fs/btrfs/extent-tree.c:4816!
RAX: 00000000ea000001
4815 if (iref) {
4816 BUG_ON(!found_extent);
4817 } else {
4818 btrfs_set_extent_refs(leaf, ei, refs);
4819 btrfs_mark_buffer_dirty(leaf);
4820 }
found_extent is int and modified at
4686 int found_extent = 0;
and
4712 if (key.type == BTRFS_EXTENT_ITEM_KEY &&
4713 key.offset == num_bytes) {
4714 found_extent = 1;
4715 break;
4716 }
This looks like a crappy memory as well.
> > offset 368640 found 1 wanted 3925868545
> 3925868545 == EA000001
"found 1 wanted 1"
david
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