linux-kernel - [RFC PATCH] vmalloc: show more detail info in vmallocinfo for clarify

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Date:   Sat, 20 May 2017 14:47:41 +0800
From:   Yisheng Xie <xieyisheng1@...wei.com>
To:     <akpm@...ux-foundation.org>, <mhocko@...e.com>, <zijun_hu@....com>,
        <mingo@...nel.org>, <thgarnie@...gle.com>,
        <kirill.shutemov@...ux.intel.com>, <aryabinin@...tuozzo.com>,
        <chris@...is-wilson.co.uk>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <guohanjun@...wei.com>
Subject: [RFC PATCH] vmalloc: show more detail info in vmallocinfo for clarify

When ioremap a 67112960 bytes vm_area with the vmallocinfo:
 [..]
 0xec79b000-0xec7fa000  389120 ftl_add_mtd+0x4d0/0x754 pages=94 vmalloc
 0xec800000-0xecbe1000 4067328 kbox_proc_mem_write+0x104/0x1c4 phys=8b520000 ioremap

we get result:
 0xf1000000-0xf5001000 67112960 devm_ioremap+0x38/0x7c phys=40000000 ioremap

For the align for ioremap must be less than '1 << IOREMAP_MAX_ORDER':
	if (flags & VM_IOREMAP)
		align = 1ul << clamp_t(int, get_count_order_long(size),
			PAGE_SHIFT, IOREMAP_MAX_ORDER);

So it makes idiot like me a litter puzzle why jump the vm_area from
0xec800000-0xecbe1000 to 0xf1000000-0xf5001000, and leave
0xed000000-0xf1000000 as a big hole.

This is to show all of vm_area, including which is freeing but still in
vmap_area_list, to make it more clear about why we will get
0xf1000000-0xf5001000 int the above case. And we will get the
vmallocinfo like:
 [..]
 0xec79b000-0xec7fa000  389120 ftl_add_mtd+0x4d0/0x754 pages=94 vmalloc
 0xec800000-0xecbe1000 4067328 kbox_proc_mem_write+0x104/0x1c4 phys=8b520000 ioremap
 [..]
 0xece7c000-0xece7e000    8192 freeing vm_area
 0xece7e000-0xece83000   20480 vm_map_ram
 0xf0099000-0xf00aa000   69632 vm_map_ram
 0xf1000000-0xf5001000 67112960 devm_ioremap+0x38/0x7c phys=40000000 ioremap
after apply this patch.

Signed-off-by: Yisheng Xie <xieyisheng1@...wei.com>
---
 mm/vmalloc.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index b52aeed..dbb24fc 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -314,6 +314,7 @@ unsigned long vmalloc_to_pfn(const void *vmalloc_addr)
 
 /*** Global kva allocator ***/
 
+#define VM_LAZY_FREE	0x02
 #define VM_VM_AREA	0x04
 
 static DEFINE_SPINLOCK(vmap_area_lock);
@@ -1486,6 +1487,7 @@ struct vm_struct *remove_vm_area(const void *addr)
 		spin_lock(&vmap_area_lock);
 		va->vm = NULL;
 		va->flags &= ~VM_VM_AREA;
+		va->flags |= VM_LAZY_FREE;
 		spin_unlock(&vmap_area_lock);
 
 		vmap_debug_free_range(va->va_start, va->va_end);
@@ -2684,8 +2686,14 @@ static int s_show(struct seq_file *m, void *p)
 	 * s_show can encounter race with remove_vm_area, !VM_VM_AREA on
 	 * behalf of vmap area is being tear down or vm_map_ram allocation.
 	 */
-	if (!(va->flags & VM_VM_AREA))
+	if (!(va->flags & VM_VM_AREA)) {
+		seq_printf(m, "0x%pK-0x%pK %7ld %s\n",
+			(void *)va->va_start, (void *)va->va_end,
+			va->va_end - va->va_start,
+			va->flags & VM_LAZY_FREE ? "freeing vm_area" : "vm_map_ram");
+
 		return 0;
+	}
 
 	v = va->vm;
 
-- 
1.7.12.4