# mkfs.btrfs /dev/sdd && btrfs-debug-tree -R /dev/sdd | egrep checksum
::
checksum tree key (CSUM_TREE ROOT_ITEM 0) 29376512 level 0
# btrfs-corrupt-block -l 29376512 /dev/sdd
mirror 1 logical 29376512 physical 37765120 device /dev/sdd
corrupting 29376512 copy 1
mirror 2 logical 29376512 physical 145113088 device /dev/sdd
corrupting 29376512 copy 2
# btrfsck /dev/sdd
Check tree block failed, want=29376512, have=0
Check tree block failed, want=29376512, have=0
Check tree block failed, want=29376512, have=0
Check tree block failed, want=29376512, have=0
Check tree block failed, want=29376512, have=0
read block failed check_tree_block
Couldn't setup csum tree
checking extents
Check tree block failed, want=29376512, have=0
Check tree block failed, want=29376512, have=0
Check tree block failed, want=29376512, have=0
Check tree block failed, want=29376512, have=0
Check tree block failed, want=29376512, have=0
read block failed check_tree_block <---- !!
Segmentation fault (core dumped) <--- !!
#
----------------
read_tree_block frees buf and returns NULL
----------------
struct extent_buffer *read_tree_block(struct btrfs_root *root, u64 bytenr,
u32 blocksize, u64 parent_transid)
{
::
while (1) {
::
if (ignore) {
if (check_tree_block(root, eb))
printk("read block failed check_tree_block\n");
<----
else
printk("Csum didn't match\n");
break;
}
::
}
free_extent_buffer(eb);
return NULL;
}
----------------
we don't check if the buf is NULL and fails with
Segmentation faults in add_root_to_pending
---------------------
static int check_extents(struct btrfs_trans_handle *trans,
struct btrfs_root *root, int repair)
{
::
buf = read_tree_block(root->fs_info->tree_root,
btrfs_root_bytenr(&ri),
btrfs_level_size(root,
btrfs_root_level(&ri)), 0);
<--- buf is NULL
add_root_to_pending(buf, bits, bits_nr, &extent_cache,
&pending, &seen, &reada, &nodes,
&found_key);
free_extent_buffer(buf);
}
-----------------------
Seems like the simple fix is to redirect btrfsck user to use
--init-csum-tree when csum root is corrupted
thanks
Anand
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