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Date: Fri, 7 Dec 2012 01:09:31 +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 4/8] mm, vmalloc: iterate vmap_area_list, instead of vmlist in vread/vwrite()
Now, when we hold a vmap_area_lock, va->vm can't be discarded. So we can
safely access to va->vm when iterating a vmap_area_list with holding a
vmap_area_lock. With this property, change iterating vmlist codes in
vread/vwrite() to iterating vmap_area_list.
There is a little difference relate to lock, because vmlist_lock is mutex,
but, vmap_area_lock is spin_lock. It may introduce a spinning overhead
during vread/vwrite() is executing. But, these are debug-oriented
functions, so this overhead is not real problem for common case.
Signed-off-by: Joonsoo Kim <js1304@...il.com>
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index a0b85a6..d21167f 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2009,7 +2009,8 @@ static int aligned_vwrite(char *buf, char *addr, unsigned long count)
long vread(char *buf, char *addr, unsigned long count)
{
- struct vm_struct *tmp;
+ struct vmap_area *va;
+ struct vm_struct *vm;
char *vaddr, *buf_start = buf;
unsigned long buflen = count;
unsigned long n;
@@ -2018,10 +2019,17 @@ long vread(char *buf, char *addr, unsigned long count)
if ((unsigned long) addr + count < count)
count = -(unsigned long) addr;
- read_lock(&vmlist_lock);
- for (tmp = vmlist; count && tmp; tmp = tmp->next) {
- vaddr = (char *) tmp->addr;
- if (addr >= vaddr + tmp->size - PAGE_SIZE)
+ spin_lock(&vmap_area_lock);
+ list_for_each_entry(va, &vmap_area_list, list) {
+ if (!count)
+ break;
+
+ if (!(va->flags & VM_VM_AREA))
+ continue;
+
+ vm = va->vm;
+ vaddr = (char *) vm->addr;
+ if (addr >= vaddr + vm->size - PAGE_SIZE)
continue;
while (addr < vaddr) {
if (count == 0)
@@ -2031,10 +2039,10 @@ long vread(char *buf, char *addr, unsigned long count)
addr++;
count--;
}
- n = vaddr + tmp->size - PAGE_SIZE - addr;
+ n = vaddr + vm->size - PAGE_SIZE - addr;
if (n > count)
n = count;
- if (!(tmp->flags & VM_IOREMAP))
+ if (!(vm->flags & VM_IOREMAP))
aligned_vread(buf, addr, n);
else /* IOREMAP area is treated as memory hole */
memset(buf, 0, n);
@@ -2043,7 +2051,7 @@ long vread(char *buf, char *addr, unsigned long count)
count -= n;
}
finished:
- read_unlock(&vmlist_lock);
+ spin_unlock(&vmap_area_lock);
if (buf == buf_start)
return 0;
@@ -2082,7 +2090,8 @@ finished:
long vwrite(char *buf, char *addr, unsigned long count)
{
- struct vm_struct *tmp;
+ struct vmap_area *va;
+ struct vm_struct *vm;
char *vaddr;
unsigned long n, buflen;
int copied = 0;
@@ -2092,10 +2101,17 @@ long vwrite(char *buf, char *addr, unsigned long count)
count = -(unsigned long) addr;
buflen = count;
- read_lock(&vmlist_lock);
- for (tmp = vmlist; count && tmp; tmp = tmp->next) {
- vaddr = (char *) tmp->addr;
- if (addr >= vaddr + tmp->size - PAGE_SIZE)
+ spin_lock(&vmap_area_lock);
+ list_for_each_entry(va, &vmap_area_list, list) {
+ if (!count)
+ break;
+
+ if (!(va->flags & VM_VM_AREA))
+ continue;
+
+ vm = va->vm;
+ vaddr = (char *) vm->addr;
+ if (addr >= vaddr + vm->size - PAGE_SIZE)
continue;
while (addr < vaddr) {
if (count == 0)
@@ -2104,10 +2120,10 @@ long vwrite(char *buf, char *addr, unsigned long count)
addr++;
count--;
}
- n = vaddr + tmp->size - PAGE_SIZE - addr;
+ n = vaddr + vm->size - PAGE_SIZE - addr;
if (n > count)
n = count;
- if (!(tmp->flags & VM_IOREMAP)) {
+ if (!(vm->flags & VM_IOREMAP)) {
aligned_vwrite(buf, addr, n);
copied++;
}
@@ -2116,7 +2132,7 @@ long vwrite(char *buf, char *addr, unsigned long count)
count -= n;
}
finished:
- read_unlock(&vmlist_lock);
+ spin_unlock(&vmap_area_lock);
if (!copied)
return 0;
return buflen;
--
1.7.9.5
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