Re: [PATCH] ext4: do not BUG when INLINE_DATA_FL lacks system.data xattr

[Moon Hee Lee]

>
> Thanks ofor the patch!  However, instead of doing an xattr lookup in
> ext4_prepare_inline_data(), we can more simply and more efficiently
> just not BUG in ext4_update_inline_data, like this:

Thanks for the response and for taking the time to address the issue.

Just to clarify the intent behind the earlier patch [1]: it was meant to
catch the missing system.data xattr early in ext4_prepare_inline_data(),
before branching into paths that assume the xattr is present.

> @@ -354,6 +354,12 @@ static int ext4_update_inline_data(handle_t *handle, struct inode *inode,
>         if (error)
>                 goto out;
>
> +       if (is.s.not_found) {
> +               EXT4_ERROR_INODE(inode, "missing inline data xattr");
> +               error = -EFSCORRUPTED;
> +               goto out;
> +       }
> +
>         BUG_ON(is.s.not_found);

The current patch addresses ext4_update_inline_data() directly, but the
same condition also leads to a BUG_ON in ext4_create_inline_data() [2],
which the earlier approach intended to prevent as well.

Later, a third instance was found in ext4_inline_data_truncate() [3],
which also contains a similar BUG_ON and might need the same kind of
check.

Reducing duplicated checks across these sites would be beneficial, though
fixing each case directly also looks reasonable and straightforward.

[1] https://lore.kernel.org/all/20250710175837.29822-2-moonhee.lee.ca@xxxxxxxxx/
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/ext4/inline.c?h=v6.16-rc6#n306
[3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/ext4/inline.c?h=v6.16-rc6#n1906