Motivation and Context

Build is failing on my Debian9 builder:

     CC [M]  module/zfs/spa.o
   module/zfs/spa.c: In function ‘spa_wait_common.part.31’:
   module/zfs/spa.c:9468:6: error: ‘in_progress’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
      if (!in_progress || spa->spa_waiters_cancel || error)
         ^
   cc1: all warnings being treated as errors

Description

in_progress may be used uninitialized if we return EINVAL in spa_vdev_initializing():

spa_wait_common()
  -> spa_activity_in_progress()
    -> spa_vdev_initializing() <- returns EINVAL, does not initialize "in_progress"

When this happens error is guaranteed to be != 0; this change prevents access to the uninitialized in_progress thanks to short-circuit evaluation

diff --git a/module/zfs/spa.c b/module/zfs/spa.c
index 0f1a2a9eb..7e5c474eb 100644
--- a/module/zfs/spa.c
+++ b/module/zfs/spa.c
@@ -9465,7 +9465,7 @@ spa_wait_common(const char *pool, zpool_wait_activity_t activity,
                error = spa_activity_in_progress(spa, activity, use_tag, tag,
                    &in_progress);
 
-               if (!in_progress || spa->spa_waiters_cancel || error)
+               if (error || !in_progress || spa->spa_waiters_cancel)
                        break;
 
                *waited = B_TRUE;

How Has This Been Tested?

Compiled on Debian9 builder (GCC 6.3.0)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the ZFS on Linux code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• All new and existing tests passed.
• All commit messages are properly formatted and contain Signed-off-by.