[dm-devel] dm cache metadata: fix cmd_read_lock acquiring write lock

[Mike Snitzer]

On Sun, Apr 17 2016 at  1:37P -0400,
Ahmed Samy <f.fallen45 at gmail.com> wrote:

> commit 9567366fefdd ("dm cache metadata: fix READ_LOCK macros and cleanup WRITE_LOCK macros")
> seemed to use down_write instead of down_read in cmd_read_lock(), yet
> releasing it with up_read() in READ_UNLOCK.  Fix it.
> 
> Cc: Mike Snitzer <snitzer at redhat.com>
> Cc: stable at vger.kernel.org
> Signed-off-by: Ahmed Samy <f.fallen45 at gmail.com>

Ugh, very frustrating -- I must've looked at this code 3 different times
to try to make sure I didn't have a thinko.  And strangely sparse didn't
catch this locking bug (from cut-n-paste).

Anyway, thanks... I'll see if I can get this to Linus ASAP.

Mike