[PATCH 4/6] fs: fat: update parent dirs metadata on rename

[Heinrich Schuchardt]

On 22.01.25 06:32, Gabriel Dalimonte wrote:
> None of the existing fat code appears to update parent dir properties
> however, the POSIX specification for rename() mentions that the
> last modified timestamp should be updated. In addition, I believe
> the ATTR_ARCH attribute should also be reset on the parent directories
> as the content of those directories has changed.

Could you, please, provide a link to the referenced specification.

E.g. https://pubs.opengroup.org/onlinepubs/9799919799/functions/rename.html

Here I find:
"Upon successful completion, rename() shall mark for update the last
data modification and last file status change timestamps of the parent
directory of each file."

Does this mean that if we move a directory we would have to update the
fields of all moved non-empty sub-directories?

On many boards we don't have a real time clock. Should we skip updating
if we have no RTC?

If we want to update parent directories, we should do this for file
creation, too. The update function could be called in the function where
we create directory entries.

Best regards

Heinrich

>
> Signed-off-by: Gabriel Dalimonte <gabriel.dalimonte at gmail.com>
> ---
>
>   fs/fat/fat_write.c | 42 ++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 42 insertions(+)
>
> diff --git a/fs/fat/fat_write.c b/fs/fat/fat_write.c
> index f9f7051e30..2559e38d5b 100644
> --- a/fs/fat/fat_write.c
> +++ b/fs/fat/fat_write.c
> @@ -1912,6 +1912,42 @@ exit:
>   	return ret;
>   }
>
> +/**
> + * update_parent_dir_props - updates the modified time and resets the archive
> + * attribute for the parent directory
> + *
> + * @itr:	iterator positioned anywhere in a directory whose parent should be
> + *	updated
> + * @Return:	0 for success
> + */
> +static int update_parent_dir_props(fat_itr *itr)
> +{
> +	int ret = 0;
> +	__u32 target_clust = itr->start_clust;
> +	/* For START macro */
> +	fsdata *mydata = itr->fsdata;
> +
> +	if (!itr->is_root) {
> +		ret = fat_itr_parent(itr);
> +		if (ret)
> +			return ret;
> +
> +		while (fat_itr_next(itr)) {
> +			if (START(itr->dent) == target_clust)
> +				goto update;
> +		}
> +
> +		/* dent not found */
> +		return -EIO;
> +update:
> +		dentry_set_time(itr->dent);
> +		itr->dent->attr |= ATTR_ARCH;
> +		ret = flush_dir(itr);
> +	}
> +
> +	return ret;
> +}
> +
>   /**
>    * fat_rename - rename/move a file or directory
>    *
> @@ -2086,7 +2122,12 @@ int fat_rename(const char *old_path, const char *new_path)
>   		ret = flush_dir(new_itr);
>   		if (ret)
>   			goto exit;
> +		/* restore directory location to update parent props below */
> +		fat_itr_child(new_itr, new_itr);
>   	}
> +	ret = update_parent_dir_props(new_itr);
> +	if (ret)
> +		goto exit;
>
>   	/* refresh old in case write happened to the same block. */
>   	ret = fat_move_to_cluster(old_itr, old_itr->dent_clust);
> @@ -2097,6 +2138,7 @@ int fat_rename(const char *old_path, const char *new_path)
>   	if (ret)
>   		goto exit;
>
> +	ret = update_parent_dir_props(old_itr);
>   exit:
>   	free(new_datablock.fatbuf);
>   	free(old_datablock.fatbuf);