[PATCH v10 14/18] mm/debug: print vm_refcnt state when dumping the vma

[Suren Baghdasaryan <surenb@google.com>]

vm_refcnt encodes a number of useful states:
- whether vma is attached or detached
- the number of current vma readers
- presence of a vma writer
Let's include it in the vma dump.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
---
Changes since v9 [1]:
- Minimized duplicate code, per Lorenzo Stoakes

[1] https://lore.kernel.org/all/20250111042604.3230628-14-surenb@google.com/

 mm/debug.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/debug.c b/mm/debug.c
index e1282b85a877..2d1bd67d957b 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -181,11 +181,17 @@ void dump_vma(const struct vm_area_struct *vma)
 	pr_emerg("vma %px start %px end %px mm %px\n"
 		"prot %lx anon_vma %px vm_ops %px\n"
 		"pgoff %lx file %px private_data %px\n"
+#ifdef CONFIG_PER_VMA_LOCK
+		"refcnt %x\n"
+#endif
 		"flags: %#lx(%pGv)\n",
 		vma, (void *)vma->vm_start, (void *)vma->vm_end, vma->vm_mm,
 		(unsigned long)pgprot_val(vma->vm_page_prot),
 		vma->anon_vma, vma->vm_ops, vma->vm_pgoff,
 		vma->vm_file, vma->vm_private_data,
+#ifdef CONFIG_PER_VMA_LOCK
+		refcount_read(&vma->vm_refcnt),
+#endif
 		vma->vm_flags, &vma->vm_flags);
 }
 EXPORT_SYMBOL(dump_vma);
-- 
2.48.1.601.g30ceb7b040-goog