Re: [PATCH 4/4] block: cleanup the flush plug helpers

[Jens Axboe <axboe@kernel.dk>]

On 10/22/21 2:09 PM, Nathan Chancellor wrote:
> On Wed, Oct 20, 2021 at 04:41:19PM +0200, Christoph Hellwig wrote:
>> Consolidate the various helpers into a single blk_flush_plug helper that
>> takes a plk_plug and the from_scheduler bool and switch all callsites to
>> call it directly.  Checks that the plug is non-NULL must be performed by
>> the caller, something that most already do anyway.
>>
>> Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> This patch as commit 008f75a20e70 ("block: cleanup the flush plug
> helpers") in -next causes the following errors with CONFIG_BLOCK=n
> (tinyconfig):
> 
> kernel/sched/core.c: In function ‘sched_submit_work’:
> kernel/sched/core.c:6346:35: error: ‘struct task_struct’ has no member named ‘plug’
>  6346 |                 blk_flush_plug(tsk->plug, true);
>       |                                   ^~
> kernel/sched/core.c: In function ‘io_schedule_prepare’:
> kernel/sched/core.c:8357:20: error: ‘struct task_struct’ has no member named ‘plug’
>  8357 |         if (current->plug)
>       |                    ^~
> kernel/sched/core.c:8358:39: error: ‘struct task_struct’ has no member named ‘plug’
>  8358 |                 blk_flush_plug(current->plug, true);
>       |                                       ^~
> 
> I tested the latest block tree and did not see it fixed nor did I see it
> reported or fixed elsewhere.

This should fix it, thanks for reporting.

commit 599593a82fc57f5e9453c8ef7420df3206934a0c
Author: Jens Axboe <axboe@kernel.dk>
Date:   Fri Oct 22 19:35:45 2021 -0600

    sched: make task_struct->plug always defined
    
    If CONFIG_BLOCK isn't set, then it's an empty struct anyway. Just make
    it generally available, so we don't break the compile:
    
    kernel/sched/core.c: In function ‘sched_submit_work’:
    kernel/sched/core.c:6346:35: error: ‘struct task_struct’ has no member named ‘plug’
     6346 |                 blk_flush_plug(tsk->plug, true);
          |                                   ^~
    kernel/sched/core.c: In function ‘io_schedule_prepare’:
    kernel/sched/core.c:8357:20: error: ‘struct task_struct’ has no member named ‘plug’
     8357 |         if (current->plug)
          |                    ^~
    kernel/sched/core.c:8358:39: error: ‘struct task_struct’ has no member named ‘plug’
     8358 |                 blk_flush_plug(current->plug, true);
          |                                       ^~
    
    Reported-by: Nathan Chancellor <nathan@kernel.org>
    Fixes: 008f75a20e70 ("block: cleanup the flush plug helpers")
    Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/include/linux/sched.h b/include/linux/sched.h
index c1a927ddec64..e0454e60fe8f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1160,10 +1160,8 @@ struct task_struct {
 	/* Stacked block device info: */
 	struct bio_list			*bio_list;
 
-#ifdef CONFIG_BLOCK
 	/* Stack plugging: */
 	struct blk_plug			*plug;
-#endif
 
 	/* VM state: */
 	struct reclaim_state		*reclaim_state;

-- 
Jens Axboe