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 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' - 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: Yafang 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/delayacct.h b/include/linux/delayacct.h
index 2d3bdcc..21651f9 100644 (file)
--- 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 cbdc2cd..8c491f8 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -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;