[dm-devel] [PATCH v2] dm era: only resize metadata in preresume

[Mike Snitzer]

On Thu, Feb 11 2021 at  9:22am -0500,
Nikos Tsironis <ntsironis at arrikto.com> wrote:

> Metadata resize shouldn't happen in the ctr. The ctr loads a temporary
> (inactive) table that will only become active upon resume. That is why
> resize should always be done in terms of resume. Otherwise a load (ctr)
> whose inactive table never becomes active will incorrectly resize the
> metadata.
> 
> Also, perform the resize directly in preresume, instead of using the
> worker to do it.
> 
> The worker might run other metadata operations, e.g., it could start
> digestion, before resizing the metadata. These operations will end up
> using the old size.
> 
> This could lead to errors, like:
> 
>   device-mapper: era: metadata_digest_transcribe_writeset: dm_array_set_value failed
>   device-mapper: era: process_old_eras: digest step failed, stopping digestion
> 
> The reason of the above error is that the worker started the digestion
> of the archived writeset using the old, larger size.
> 
> As a result, metadata_digest_transcribe_writeset tried to write beyond
> the end of the era array.
> 
> Fixes: eec40579d84873 ("dm: add era target")
> Cc: stable at vger.kernel.org # v3.15+
> Signed-off-by: Nikos Tsironis <ntsironis at arrikto.com>
> ---
>  drivers/md/dm-era-target.c | 21 ++++++++++-----------
>  1 file changed, 10 insertions(+), 11 deletions(-)

Thanks, I replaced the patch I created (that used a worker to resize
from preresume) with this.

Now staged for 5.12.

Mike