Re: [PATCH v4 3/7] mm: shmem: Update shmem handler to the MF_DELAYED definition

[Ackerley Tng]

Lisa Wang <wyihan@xxxxxxxxxx> writes:

> To align with the definition of MF_DELAYED, update
> shmem_error_remove_folio() to return MF_DELAYED.
>
> shmem handles memory failures but defers the actual file truncation. The
> function's return value should therefore be MF_DELAYED to accurately
> reflect the state.
>
> Currently, this logical error does not cause a bug, because:
>
> - For shmem folios, folio->private is not set.
> - As a result, filemap_release_folio() is a no-op and returns true.
> - This, in turn, causes truncate_error_folio() to incorrectly return
>   MF_RECOVERED.
> - The caller then treats MF_RECOVERED as a success condition, masking the
>   issue.
>
> The previous patch relays MF_DELAYED to the caller of
> truncate_error_folio() before any logging, so returning MF_DELAYED from
> shmem_error_remove_folio() will retain the original behavior of not
> adding any logs.
>
> The return value of truncate_error_folio() is consumed in action_result(),
> which treats MF_DELAYED the same way as MF_RECOVERED, hence action_result()
> also returns the same thing after this change.
>

Thanks for explaining here!

Reviewed-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>

> Signed-off-by: Lisa Wang <wyihan@xxxxxxxxxx>
> ---
>  mm/shmem.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
>
> [...snip...]
>