23. 7. 16. 08:36에 Dave Chinner 이(가) 쓴 글:
On Sat, Jul 15, 2023 at 05:22:04PM +0900, Leesoo Ahn wrote:
> Return -EOPNOTSUPP instead of -EINVAL which has the meaning of
> the argument is an inappropriate value. The current error code doesn't
> make sense to represent that a file system doesn't support bmap
operation.
>
> Signed-off-by: Leesoo Ahn <lsahn@xxxxxxxxxxxxxx>
> ---
> Changes since v1:
> - Modify the comments of bmap()
> - Modify subject and description requested by Markus Elfring
>
https://lore.kernel.org/lkml/20230715060217.1469690-1-lsahn@xxxxxxxxxxxxxx/
>
> fs/inode.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/inode.c b/fs/inode.c
> index 8fefb69e1f84..697c51ed226a 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -1831,13 +1831,13 @@ EXPORT_SYMBOL(iput);
> * 4 in ``*block``, with disk block relative to the disk start that
holds that
> * block of the file.
> *
> - * Returns -EINVAL in case of error, 0 otherwise. If mapping falls
into a
> + * Returns -EOPNOTSUPP in case of error, 0 otherwise. If mapping
falls into a
> * hole, returns 0 and ``*block`` is also set to 0.
> */
> int bmap(struct inode *inode, sector_t *block)
> {
> if (!inode->i_mapping->a_ops->bmap)
> - return -EINVAL;
> + return -EOPNOTSUPP;
>
> *block = inode->i_mapping->a_ops->bmap(inode->i_mapping, *block);
> return 0;
What about the CONFIG_BLOCK=n wrapper?
How does it work? Could you explain that in details, pls?
However, as far as I understand, bmap operation could be NULL even
though CONFIG_BLOCK is enabled. It totally depends on the implementation
of file systems.
Also, all the in kernel consumers squash this error back to 0, -EIO
or -EINVAL, so this change only ever propagates out to userspace via
the return from ioctl(FIBMAP). Do we really need to change this and
risk breaking userspace that handles -EINVAL correctly but not
-EOPNOTSUPP?
That's a consideration and we must carefully modify the APIs which
communicate to users. But -EINVAL could be interpreted by two cases at
this point that the first, for sure an argument from user to kernel is
inappropriate, on the other hand, the second case would be that a file
system doesn't support bmap operation. However, I don't think there is a
proper way to know which one is right from user.
For me, the big problem is that user could get confused by these two
cases with the same error code.
Best regards,
Leesoo
