Re: [PATCH 1/2] fs: btrfs: implement opendir(), readdir() and closedir()

[Qu Wenruo]

在 2026/6/26 18:51, Alexey Charkov 写道:
On Fri, Jun 26, 2026 at 10:38 AM Qu Wenruo <w...@suse.com> wrote:
[...]

So it looks like u-boot only supports the above 3 types, and unlike
linux kernel the values doesn't match the btrfs internal ones.

In that case, I'd still prefer a proper convertor function.

Hmm, but the convertor function would still be the same switch
statement, and it's only used in this single place. Would factoring it
out actually improve readability?

This is mostly a cross-project tendency.

Inside kernel, we do not need a conversion because all the BTRFS_FT* 
flags matches the FT_* inside kernel.

In progs we have btrfs_type_to_imode() to do the conversion to S_IF* flags.

Thus I'd prefer a convertor, even if there is only a single user.


[...]
+
+             *offset = key.offset + 1;
+             type = btrfs_dir_type(path.nodes[0], di);
+
+             /* XATTRs share the key space but are not directory entries. */
+             if (type == BTRFS_FT_XATTR) {

This doesn't looks correct again.

XATTR has their own keys, they should not show up among DIR_INDEX keys.

Firstly, xattr is per-inode, not per-dentry.
Thus I doubt if you can hit an XATTR type inside a DIR_INDEX.

The easily way to test the theory is just create a simple XATTR for 
compression:

 # mkfs.btrfs -f test.img
 # mount test.img /mnt/btrfs
 # touch /mnt/btrfs/foobar
 # btrfs prop set /mnt/btrfs/foobar compression zstd
 # sync
 # btrfs ins dump-tree -t 5 test.img
 [...]
        item 6 key (257 XATTR_ITEM 550297449) itemoff 15812 itemsize 51
                location key (0 UNKNOWN.0 0) type XATTR
                transid 10 data_len 4 name_len 17
                name: btrfs.compression
                data zstd

You can see that XATTR_ITEM key is for that inode 257, not for the 
parent directory inode (256).


Secondly, if you check the tree-checker.c from the kernel, 
check_dir_item() will reject an XATTR dir type if the key is not 
XATTR_ITEM_KEY.

So even if you really find a btrfs with XATTR dir type but with 
DIR_INDEX key, btrfs will refuse to reject that tree block.

Thanks,
Qu


Let me double check and adjust accordingly.

Thanks a lot for your review!

Best regards,
Alexey