Re: [PATCH v5 3/5] vvfat: Fix wrong checks for cluster mappings invariant

[Kevin Wolf]

Am 12.06.2024 um 14:43 hat Amjad Alsharafi geschrieben:
> How this `abort` was intended to check for was:
> - if the `mapping->first_mapping_index` is not the same as
>   `first_mapping_index`, which **should** happen only in one case,
>   when we are handling the first mapping, in that case
>   `mapping->first_mapping_index == -1`, in all other cases, the other
>   mappings after the first should have the condition `true`.
> - From above, we know that this is the first mapping, so if the offset
>   is not `0`, then abort, since this is an invalid state.
> 
> The issue was that `first_mapping_index` is not set if we are
> checking from the middle, the variable `first_mapping_index` is
> only set if we passed through the check `cluster_was_modified` with the
> first mapping, and in the same function call we checked the other
> mappings.
> 
> One approach is to go into the loop even if `cluster_was_modified`
> is not true so that we will be able to set `first_mapping_index` for the
> first mapping, but since `first_mapping_index` is only used here,
> another approach is to just check manually for the
> `mapping->first_mapping_index != -1` since we know that this is the
> value for the only entry where `offset == 0` (i.e. first mapping).
> 
> Signed-off-by: Amjad Alsharafi <amjadsharafi10@gmail.com>

Reviewed-by: Kevin Wolf <kwolf@redhat.com>