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Date: Fri, 7 Dec 2012 01:09:33 +0900
From: Joonsoo Kim <js1304@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Russell King <rmk+kernel@....linux.org.uk>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
kexec@...ts.infradead.org, Joonsoo Kim <js1304@...il.com>
Subject: [RFC PATCH 6/8] mm, vmalloc: iterate vmap_area_list, instead of vmlist, in vmallocinfo()
This patch is preparing step for removing vmlist entirely.
For above purpose, we change iterating a vmap_list codes to iterating a
vmap_area_list. It is somewhat trivial change, but just one thing
should be noticed.
Using vmap_area_list in vmallocinfo() introduce ordering problem in SMP
system. In s_show(), we retrieve some values from vm_struct. vm_struct's
values is not fully setup when va->vm is assigned. Full setup is notified
by removing VM_UNLIST flag without holding a lock. When we see that
VM_UNLIST is removed, it is not ensured that vm_struct has proper values
in view of other CPUs. So we need smp_[rw]mb for ensuring that proper
values is assigned when we see that VM_UNLIST is removed.
Therefore, this patch not only change a iteration list, but also add a
appropriate smp_[rw]mb to right places.
Signed-off-by: Joonsoo Kim <js1304@...il.com>
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index f7f4a35..f134950 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1304,7 +1304,14 @@ static void insert_vmalloc_vmlist(struct vm_struct *vm)
{
struct vm_struct *tmp, **p;
+ /*
+ * Before removing VM_UNLIST,
+ * we should make sure that vm has proper values.
+ * Pair with smp_rmb() in show_numa_info().
+ */
+ smp_wmb();
vm->flags &= ~VM_UNLIST;
+
write_lock(&vmlist_lock);
for (p = &vmlist; (tmp = *p) != NULL; p = &tmp->next) {
if (tmp->addr >= vm->addr)
@@ -2539,19 +2546,19 @@ void pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
#ifdef CONFIG_PROC_FS
static void *s_start(struct seq_file *m, loff_t *pos)
- __acquires(&vmlist_lock)
+ __acquires(&vmap_area_lock)
{
loff_t n = *pos;
- struct vm_struct *v;
+ struct vmap_area *va;
- read_lock(&vmlist_lock);
- v = vmlist;
- while (n > 0 && v) {
+ spin_lock(&vmap_area_lock);
+ va = list_entry((&vmap_area_list)->next, typeof(*va), list);
+ while (n > 0 && &va->list != &vmap_area_list) {
n--;
- v = v->next;
+ va = list_entry(va->list.next, typeof(*va), list);
}
- if (!n)
- return v;
+ if (!n && &va->list != &vmap_area_list)
+ return va;
return NULL;
@@ -2559,16 +2566,20 @@ static void *s_start(struct seq_file *m, loff_t *pos)
static void *s_next(struct seq_file *m, void *p, loff_t *pos)
{
- struct vm_struct *v = p;
+ struct vmap_area *va = p, *next;
++*pos;
- return v->next;
+ next = list_entry(va->list.next, typeof(*va), list);
+ if (&next->list != &vmap_area_list)
+ return next;
+
+ return NULL;
}
static void s_stop(struct seq_file *m, void *p)
- __releases(&vmlist_lock)
+ __releases(&vmap_area_lock)
{
- read_unlock(&vmlist_lock);
+ spin_unlock(&vmap_area_lock);
}
static void show_numa_info(struct seq_file *m, struct vm_struct *v)
@@ -2579,6 +2590,11 @@ static void show_numa_info(struct seq_file *m, struct vm_struct *v)
if (!counters)
return;
+ /* Pair with smp_wmb() in insert_vmalloc_vmlist() */
+ smp_rmb();
+ if (v->flags & VM_UNLIST)
+ return;
+
memset(counters, 0, nr_node_ids * sizeof(unsigned int));
for (nr = 0; nr < v->nr_pages; nr++)
@@ -2592,36 +2608,50 @@ static void show_numa_info(struct seq_file *m, struct vm_struct *v)
static int s_show(struct seq_file *m, void *p)
{
- struct vm_struct *v = p;
+ struct vmap_area *va = p;
+ struct vm_struct *vm;
+
+ if (!(va->flags & VM_VM_AREA)) {
+ seq_printf(m, "0x%pK-0x%pK %7ld",
+ (void *)va->va_start, (void *)va->va_end,
+ va->va_end - va->va_start);
+ if (va->flags & (VM_LAZY_FREE | VM_LAZY_FREEING))
+ seq_printf(m, " (freeing)");
+
+ seq_putc(m, '\n');
+ return 0;
+ }
+
+ vm = va->vm;
seq_printf(m, "0x%pK-0x%pK %7ld",
- v->addr, v->addr + v->size, v->size);
+ vm->addr, vm->addr + vm->size, vm->size);
- if (v->caller)
- seq_printf(m, " %pS", v->caller);
+ if (vm->caller)
+ seq_printf(m, " %pS", vm->caller);
- if (v->nr_pages)
- seq_printf(m, " pages=%d", v->nr_pages);
+ if (vm->nr_pages)
+ seq_printf(m, " pages=%d", vm->nr_pages);
- if (v->phys_addr)
- seq_printf(m, " phys=%llx", (unsigned long long)v->phys_addr);
+ if (vm->phys_addr)
+ seq_printf(m, " phys=%llx", (unsigned long long)vm->phys_addr);
- if (v->flags & VM_IOREMAP)
+ if (vm->flags & VM_IOREMAP)
seq_printf(m, " ioremap");
- if (v->flags & VM_ALLOC)
+ if (vm->flags & VM_ALLOC)
seq_printf(m, " vmalloc");
- if (v->flags & VM_MAP)
+ if (vm->flags & VM_MAP)
seq_printf(m, " vmap");
- if (v->flags & VM_USERMAP)
+ if (vm->flags & VM_USERMAP)
seq_printf(m, " user");
- if (v->flags & VM_VPAGES)
+ if (vm->flags & VM_VPAGES)
seq_printf(m, " vpages");
- show_numa_info(m, v);
+ show_numa_info(m, vm);
seq_putc(m, '\n');
return 0;
}
--
1.7.9.5
--
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