Re: [PATCH RFC v7 08/23] dept: Apply sdt_might_sleep_strong() to PG_{locked,writeback} wait

From: Hillf Danton <hdanton@sina.com>
To: Byungchul Park <byungchul.park@lge.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Waiman Long <longman@redhat.com>,
	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Subject: Re: [PATCH RFC v7 08/23] dept: Apply sdt_might_sleep_strong() to PG_{locked,writeback} wait
Date: Mon,  9 Jan 2023 19:37:20 +0800	[thread overview]
Message-ID: <20230109113720.221-1-hdanton@sina.com> (raw)
In-Reply-To: <1673235231-30302-9-git-send-email-byungchul.park@lge.com>

On 9 Jan 2023 12:33:36 +0900 Byungchul Park <byungchul.park@lge.com>
> Makes Dept able to track dependencies by PG_{locked,writeback} waits.
> 
> Signed-off-by: Byungchul Park <byungchul.park@lge.com>
> ---

Hey Byungchul 

Is DEPT able to get deadlock reported for the syzbot report [1]?

Hillf

[1] https://lore.kernel.org/lkml/6383cde5-cf4b-facf-6e07-1378a485657d@I-love.SAKURA.ne.jp/

>  mm/filemap.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index c4d4ace..b013a5b 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -42,6 +42,7 @@
>  #include <linux/ramfs.h>
>  #include <linux/page_idle.h>
>  #include <linux/migrate.h>
> +#include <linux/dept_sdt.h>
>  #include <asm/pgalloc.h>
>  #include <asm/tlbflush.h>
>  #include "internal.h"
> @@ -1215,6 +1216,9 @@ static inline bool folio_trylock_flag(struct folio *folio, int bit_nr,
>  /* How many times do we accept lock stealing from under a waiter? */
>  int sysctl_page_lock_unfairness = 5;
>  
> +static struct dept_map __maybe_unused PG_locked_map = DEPT_MAP_INITIALIZER(PG_locked_map, NULL);
> +static struct dept_map __maybe_unused PG_writeback_map = DEPT_MAP_INITIALIZER(PG_writeback_map, NULL);
> +
>  static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
>  		int state, enum behavior behavior)
>  {
> @@ -1226,6 +1230,11 @@ static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
>  	unsigned long pflags;
>  	bool in_thrashing;
>  
> +	if (bit_nr == PG_locked)
> +		sdt_might_sleep_strong(&PG_locked_map);
> +	else if (bit_nr == PG_writeback)
> +		sdt_might_sleep_strong(&PG_writeback_map);
> +
>  	if (bit_nr == PG_locked &&
>  	    !folio_test_uptodate(folio) && folio_test_workingset(folio)) {
>  		delayacct_thrashing_start(&in_thrashing);
> @@ -1327,6 +1336,8 @@ static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
>  	 */
>  	finish_wait(q, wait);
>  
> +	sdt_might_sleep_finish();
> +
>  	if (thrashing) {
>  		delayacct_thrashing_end(&in_thrashing);
>  		psi_memstall_leave(&pflags);
> -- 
> 1.9.1