On Wed, Apr 14, 2021 at 04:37:20PM +0800, Yafang Shao wrote:
> When I was implementing a latency analyze tool by using task->delays and
> other things, I found there's 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 c96f5471ce7d ("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 b512719f771a ("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' into these helpers,
> after that change, the callsite will specifilly set the right task, which
> should make it less error prone.
>
> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> Cc: Tejun Heo <tj@xxxxxxxxxx>
> Cc: Josh Snyder <joshs@xxxxxxxxxxx>
> ---
> include/linux/delayacct.h | 20 ++++++++++----------
> mm/memory.c | 8 ++++----
> 2 files changed, 14 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/delayacct.h b/include/linux/delayacct.h
> index 2d3bdcccf5eb..21651f946751 100644
> --- a/include/linux/delayacct.h
> +++ b/include/linux/delayacct.h
> @@ -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)
> {}
> diff --git a/mm/memory.c b/mm/memory.c
> index 550405fc3b5e..a013d32a6611 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3296,7 +3296,7 @@ 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;
>
> @@ -3347,7 +3347,7 @@ 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;
> }
>
> @@ -3361,13 +3361,13 @@ 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;
Acked-by: Balbir Singh <bsingharora@xxxxxxxxx>
The changes seem reasonable to me. I don't maintain a git tree, Andrew can we
please queue them up in your tree?
Balbir Singh.
