[dm-devel] [PATCH v2 07/12] multipathd: ignore failed wwid recheck

[Martin Wilck]

On Fri, 2019-03-08 at 17:12 -0600, Benjamin Marzinski wrote:
> If disable_changed_wwids is set, when multipathd gets a change event
> on
> a path, it verifies that the wwid hasn't changed in
> uev_update_path().
> If get_uid() failed, uev_update_path treated this as a wwid change to
> 0.
> This could cause paths to suddenly be dropped due to an issue with
> getting the wwid.  Even if get_uid() failed because the path was
> down,
> it no change uevent happend when it later became active, multipathd
> would continue to ignore the path. Also, scsi_uid_fallback() clears
> the
> failure return if it doesn't attempt to fallback, causing get_uid()
> to return success, when it actually failed.
> 
> Multipathd should neither set nor clear wwid_changed if get_uid()
> returned failure. Also, scsi_uid_fallback() should retain the old
> return
> value if it doesn't attempt to fallback.
> 
> Signed-off-by: Benjamin Marzinski <bmarzins at redhat.com>
> ---
>  libmultipath/discovery.c | 6 +++---
>  multipathd/main.c        | 6 ++++--
>  2 files changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/libmultipath/discovery.c b/libmultipath/discovery.c
> index 729bcb9..b08cb2d 100644
> --- a/libmultipath/discovery.c
> +++ b/libmultipath/discovery.c
> @@ -1755,9 +1755,9 @@ get_vpd_uid(struct path * pp)
>  }
>  
>  static ssize_t scsi_uid_fallback(struct path *pp, int path_state,
> -			     const char **origin)
> +			     const char **origin, ssize_t old_len)
>  {
> -	ssize_t len = 0;
> +	ssize_t len = old_len;
>  	int retrigger;
>  	struct config *conf;

Please don't call this variable "old_len" but "errcode" or the like. If
this is called, "old_len" is always negative (indicating a previous
error) or 0 (indicating previous attempts returned an empty WWID, which
is also likely an error).

Otherwise, ACK. But you revert most of this later in 12/12; I think the
two should be merged (except for the scsi_uid_fallback part, maybe).

Martin

-- 
Dr. Martin Wilck <mwilck at suse.com>, Tel. +49 (0)911 74053 2107
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)