Commit 3d1c7fd9 authored by Yafang Shao's avatar Yafang Shao Committed by Linus Torvalds
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delayacct: clear right task's flag after blkio completes 

When I was implementing a latency analyzer tool by using task->delays
and other things, I found an issue in delayacct.  The issue is it should
clear the target's flag instead of current's in delayacct_blkio_end().

When I git blame delayacct, I found there're some similar issues we have
fixed in delayacct_blkio_end().

 - Commit c96f5471 ("delayacct: Account blkio completion on the
   correct task") fixed the issue that it should account blkio
   completion on the target task instead of current.

 - Commit b512719f ("delayacct: fix crash in delayacct_blkio_end()
   after delayacct init failure") fixed the issue that it should check
   target task's delays instead of current task'.

It seems that delayacct_blkio_{begin, end} are error prone.

So I introduce a new paratmeter - the target task 'p' - to these
helpers.  After that change, the callsite will specifilly set the right
task, which should make it less error prone.

Link: https://lkml.kernel.org/r/20210414083720.24083-1-laoar.shao@gmail.com


Signed-off-by: default avatarYafang Shao <laoar.shao@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Josh Snyder <joshs@netflix.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6f1f942c

include/linux/delayacct.h

+10 −10
Original line number Diff line number Diff line
@@ -82,16 +82,16 @@ static inline int delayacct_is_task_waiting_on_io(struct task_struct *p) 
		return 0;

}



static inline void delayacct_set_flag(int flag)

static inline void delayacct_set_flag(struct task_struct *p, int flag)

{

	if (current->delays)

		current->delays->flags |= flag;

	if (p->delays)

		p->delays->flags |= flag;

}



static inline void delayacct_clear_flag(int flag)

static inline void delayacct_clear_flag(struct task_struct *p, int flag)

{

	if (current->delays)

		current->delays->flags &= ~flag;

	if (p->delays)

		p->delays->flags &= ~flag;

}



static inline void delayacct_tsk_init(struct task_struct *tsk)
@@ -114,7 +114,7 @@ static inline void delayacct_tsk_free(struct task_struct *tsk) 


static inline void delayacct_blkio_start(void)

{

	delayacct_set_flag(DELAYACCT_PF_BLKIO);

	delayacct_set_flag(current, DELAYACCT_PF_BLKIO);

	if (current->delays)

		__delayacct_blkio_start();

}
@@ -123,7 +123,7 @@ static inline void delayacct_blkio_end(struct task_struct *p) 
{

	if (p->delays)

		__delayacct_blkio_end(p);

	delayacct_clear_flag(DELAYACCT_PF_BLKIO);

	delayacct_clear_flag(p, DELAYACCT_PF_BLKIO);

}



static inline int delayacct_add_tsk(struct taskstats *d,
@@ -166,9 +166,9 @@ static inline void delayacct_thrashing_end(void) 
}



#else

static inline void delayacct_set_flag(int flag)

static inline void delayacct_set_flag(struct task_struct *p, int flag)

{}

static inline void delayacct_clear_flag(int flag)

static inline void delayacct_clear_flag(struct task_struct *p, int flag)

{}

static inline void delayacct_init(void)

{}

mm/memory.c

+4 −4
Original line number Diff line number Diff line
@@ -3339,7 +3339,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) 
	}





	delayacct_set_flag(DELAYACCT_PF_SWAPIN);

	delayacct_set_flag(current, DELAYACCT_PF_SWAPIN);

	page = lookup_swap_cache(entry, vma, vmf->address);

	swapcache = page;
@@ -3388,7 +3388,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) 
					vmf->address, &vmf->ptl);

			if (likely(pte_same(*vmf->pte, vmf->orig_pte)))

				ret = VM_FAULT_OOM;

			delayacct_clear_flag(DELAYACCT_PF_SWAPIN);

			delayacct_clear_flag(current, DELAYACCT_PF_SWAPIN);

			goto unlock;

		}
@@ -3402,13 +3402,13 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) 
		 * owner processes (which may be unknown at hwpoison time)

		 */

		ret = VM_FAULT_HWPOISON;

		delayacct_clear_flag(DELAYACCT_PF_SWAPIN);

		delayacct_clear_flag(current, DELAYACCT_PF_SWAPIN);

		goto out_release;

	}



	locked = lock_page_or_retry(page, vma->vm_mm, vmf->flags);



	delayacct_clear_flag(DELAYACCT_PF_SWAPIN);

	delayacct_clear_flag(current, DELAYACCT_PF_SWAPIN);

	if (!locked) {

		ret |= VM_FAULT_RETRY;

		goto out_release;