Re: [PATCH] btrfs: print-tree: print header owner as signed

在 2026/6/24 13:56, Boris Burkov 写道:
> On Tue, Jun 23, 2026 at 08:25:40AM +0930, Qu Wenruo wrote:
>> When dumpping a tree block, btrfs_header::owner is printed as
>> unsigned, which can result in numbers that are hard to read, e.g:
>>
>>   BTRFS info (device loop0): leaf 8908800 gen 16 total ptrs 28 free space 1676 owner 18446744073709551607
>>
>> For the above output, 18446744073709551607 is (s64)-9, the root id of data
>> reloc tree.
>>
>> Despite those pre-defined root ids that are already negative, existing
>> subvolume trees will not have any negative values, as subvolume trees can
>> only utilize the lower 48 bits, so there will be no output change for
>> existing subvolumes, thus no extra confusion.
>>
> 
> What do you think about a macro or function wrapping a switch statement
> that also prints the string name of known trees?

That is possible, but I'm not sure if we need to go this complex for 
kernel modules.

A signed s64 output would be enough for most developers/advanced users 
to debug.
For end users, I do not know if things like 2 or EXTENT_TREE make any 
difference.

> What about some identifying
> info like a volume path for subvol trees? That one might be a stretch.

That's is too dangerous, it will need extra tree search and backref lookup.
Meanwhile for a tree dump inside a kernel, it's already an emergency, 
normally we do not have the extra headroom for such complex workload 
just to make the subvolume id a little easier to read.

Thanks,
Qu

> 
> Anyway, this is already a definite improvement, thanks.
> Reviewed-by: Boris Burkov <[email protected]>
> 
>> Signed-off-by: Qu Wenruo <[email protected]>
>> ---
>>   fs/btrfs/print-tree.c | 8 ++++----
>>   1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/btrfs/print-tree.c b/fs/btrfs/print-tree.c
>> index 87e60a2d4bd8..53e726119ca7 100644
>> --- a/fs/btrfs/print-tree.c
>> +++ b/fs/btrfs/print-tree.c
>> @@ -449,9 +449,9 @@ void btrfs_print_leaf(const struct extent_buffer *l)
>>   	nr = btrfs_header_nritems(l);
>>   
>>   	btrfs_info(fs_info,
>> -		   "leaf %llu gen %llu total ptrs %d free space %d owner %llu",
>> +		   "leaf %llu gen %llu total ptrs %d free space %d owner %lld",
>>   		   btrfs_header_bytenr(l), btrfs_header_generation(l), nr,
>> -		   btrfs_leaf_free_space(l), btrfs_header_owner(l));
>> +		   btrfs_leaf_free_space(l), (s64)btrfs_header_owner(l));
>>   	print_eb_refs_lock(l);
>>   	for (i = 0 ; i < nr ; i++) {
>>   		char key_buf[KEY_TYPE_BUF_SIZE];
>> @@ -600,10 +600,10 @@ void btrfs_print_tree(const struct extent_buffer *c, bool follow)
>>   		return;
>>   	}
>>   	btrfs_info(fs_info,
>> -		   "node %llu level %d gen %llu total ptrs %d free spc %u owner %llu",
>> +		   "node %llu level %d gen %llu total ptrs %d free spc %u owner %lld",
>>   		   btrfs_header_bytenr(c), level, btrfs_header_generation(c),
>>   		   nr, (u32)BTRFS_NODEPTRS_PER_BLOCK(fs_info) - nr,
>> -		   btrfs_header_owner(c));
>> +		   (s64)btrfs_header_owner(c));
>>   	print_eb_refs_lock(c);
>>   	for (i = 0; i < nr; i++) {
>>   		btrfs_node_key_to_cpu(c, &key, i);
>> -- 
>> 2.54.0
>>