linux-kernel - [PATCH] mm: khugepaged: fix the arguments order in khugepaged_collapse

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Message-ID: <20241012011702.1084846-1-yang@os.amperecomputing.com>
Date: Fri, 11 Oct 2024 18:17:02 -0700
From: Yang Shi <yang@...amperecomputing.com>
To: gautammenghani201@...il.com,
	rostedt@...dmis.org,
	akpm@...ux-foundation.org
Cc: yang@...amperecomputing.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] mm: khugepaged: fix the arguments order in khugepaged_collapse_file trace point

The "addr" and "is_shmem" arguments have different order in TP_PROTO and
TP_ARGS.  This resulted in the incorrect trace result:

text-hugepage-644429 [276] 392092.878683: mm_khugepaged_collapse_file:
mm=0xffff20025d52c440, hpage_pfn=0x200678c00, index=512, addr=1, is_shmem=0,
filename=text-hugepage, nr=512, result=failed

The value of "addr" is wrong because it was treated as bool value, the
type of is_shmem.

Fix the order in TP_PROTO to keep "addr" is before "is_shmem" since the
original patch review suggested this order to achieve best packing.

And use "lx" for "addr" instead of "ld" in TP_printk because address is
typically shown in hex.

After the fix, the trace result looks correct:

text-hugepage-7291  [004]   128.627251: mm_khugepaged_collapse_file:
mm=0xffff0001328f9500, hpage_pfn=0x20016ea00, index=512, addr=0x400000,
is_shmem=0, filename=text-hugepage, nr=512, result=failed

Fixes: 4c9473e87e75 ("mm/khugepaged: add tracepoint to collapse_file()")
Cc: <stable@...r.kernel.org>    [6.2+]
Signed-off-by: Yang Shi <yang@...amperecomputing.com>
---
 include/trace/events/huge_memory.h | 4 ++--
 mm/khugepaged.c                    | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
index b5f5369b6300..9d5c00b0285c 100644
--- a/include/trace/events/huge_memory.h
+++ b/include/trace/events/huge_memory.h
@@ -208,7 +208,7 @@ TRACE_EVENT(mm_khugepaged_scan_file,
 
 TRACE_EVENT(mm_khugepaged_collapse_file,
 	TP_PROTO(struct mm_struct *mm, struct folio *new_folio, pgoff_t index,
-			bool is_shmem, unsigned long addr, struct file *file,
+			unsigned long addr, bool is_shmem, struct file *file,
 			int nr, int result),
 	TP_ARGS(mm, new_folio, index, addr, is_shmem, file, nr, result),
 	TP_STRUCT__entry(
@@ -233,7 +233,7 @@ TRACE_EVENT(mm_khugepaged_collapse_file,
 		__entry->result = result;
 	),
 
-	TP_printk("mm=%p, hpage_pfn=0x%lx, index=%ld, addr=%ld, is_shmem=%d, filename=%s, nr=%d, result=%s",
+	TP_printk("mm=%p, hpage_pfn=0x%lx, index=%ld, addr=%lx, is_shmem=%d, filename=%s, nr=%d, result=%s",
 		__entry->mm,
 		__entry->hpfn,
 		__entry->index,
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index f9c39898eaff..a420eff92011 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2227,7 +2227,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
 	folio_put(new_folio);
 out:
 	VM_BUG_ON(!list_empty(&pagelist));
-	trace_mm_khugepaged_collapse_file(mm, new_folio, index, is_shmem, addr, file, HPAGE_PMD_NR, result);
+	trace_mm_khugepaged_collapse_file(mm, new_folio, index, addr, is_shmem, file, HPAGE_PMD_NR, result);
 	return result;
 }
 
-- 
2.41.0