Re: [PATCH 3/3] xfs: shut up -Wuninitialized in xfsaild_push

[Dave Chinner <david@fromorbit.com>]

On Thu, Nov 24, 2022 at 08:59:35AM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> -Wuninitialized complains about @target in xfsaild_push being
> uninitialized in the case where the waitqueue is active but there is no
> last item in the AIL to wait for.  I /think/ it should never be the case
> that the subsequent xfs_trans_ail_cursor_first returns a log item and
> hence we'll never end up at XFS_LSN_CMP, but let's make this explicit.

If xfs_ail_max() returns NULL, then xfs_trans_ail_cursor_first()
must return NULL as the AIL is empty. So we always jump out of the
code in that case, and never use an uninitialised target value.
Older compilers (gcc-11) don't complain about target being used
uninitialised, only newer, "smarter" versions.

FWIW, the patchset I have that reworks the AIL push
target/wakeup/grant head accounting completely reworks this target
code[1], so in the mean time doing this to shut up the compiler
warnings is fine.

Reviewed-by: Dave Chinner <dchinner@redhat.com>

[1] https://lore.kernel.org/linux-xfs/20220809230353.3353059-1-david@fromorbit.com/

-- 
Dave Chinner
david@fromorbit.com