Re: [RFC PATCH] fs/ntfs3: prevent positive E_NTFS_NONRESIDENT from reaching writeback error handling

[Konstantin Komarov <almaz.alexandrovich@paragon-software.com>]

On 7/13/26 10:41, Vidhu Sarwal wrote:

> attr_data_write_resident() returns the internal positive status code
> E_NTFS_NONRESIDENT when the DATA attribute becomes non-resident.
> ntfs_writepages() propagates this value into generic writeback error
> handling, which expects a standard negative errno and triggers
> WARN_ON_ONCE(err > 0).
>
> Translate positive E_NTFS_* status codes to -EIO before recording
> the writeback error. This prevents positive internal status codes from
> reaching generic writeback code while preserving the existing behaviour
> of treating this path as a writeback error.
>
> Reported-by: syzbot+57f9327d593d301ce2a2@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=57f9327d593d301ce2a2
> Signed-off-by: Vidhu Sarwal <vidhu.linux@gmail.com>
> ---
> RFC:
>
> I'd appreciate guidance on whether -EIO is the appropriate errno here.
>
> E_NTFS_NONRESIDENT indicates that the DATA attribute became
> non-resident during writeback. Translating it to -EIO prevents the
> positive internal status code from reaching generic writeback code and
> preserves the existing behaviour of treating this path as a writeback
> error.
>
> However, if the intended behaviour is to retry the write using the
> non-resident path instead of failing it, then the correct solution would
> be more than a simple errno translation. The proposed change assumes the
> current terminal-error behaviour is intentional.
>   fs/ntfs3/inode.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
>
> diff --git a/fs/ntfs3/inode.c b/fs/ntfs3/inode.c
> index 0c9bd669117d..9458867c6b0b 100644
> --- a/fs/ntfs3/inode.c
> +++ b/fs/ntfs3/inode.c
> @@ -1019,6 +1019,15 @@ static int ntfs_writepages(struct address_space *mapping,
>
>                          folio_unlock(folio);
>                          if (err2) {
> +                               /*
> +                                * attr_data_write_resident() can return the
> +                                * positive internal code E_NTFS_NONRESIDENT;
> +                                * both mapping_set_error() and writeback_iter()
> +                                * need a negative errno and warn on a positive
> +                                * value.
> +                                */
> +                               if (err2 > 0)
> +                                       err2 = -EIO;
>                                  mapping_set_error(mapping, err2);
>                                  if (!err)
>                                          err = err2;
>
> base-commit: a13c140cc289c0b7b3770bce5b3ad42ab35074aa
> --
> 2.53.0

Hello,

Sorry for the delay.
Your patch was applied, thanks.

Regards,
Konstantin