[PATCH] i386/x86-64: Don't call change_page_attr with a spinlock held

It's illegal because it can sleep.

Use a two step lookup scheme instead.  First look up the vm_struct, then
change the direct mapping, then finally unmap it.  That's ok because nobody
can change the particular virtual address range as long as the vm_struct is
still in the global list.

Also added some LinuxDoc documentation to iounmap.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 31 insertions, 6 deletions

diff --git a/arch/x86_64/mm/ioremap.c b/arch/x86_64/mm/ioremap.c
index ecf7acb5db9b..0d260e4492f7 100644
--- a/arch/x86_64/mm/ioremap.c
+++ b/arch/x86_64/mm/ioremap.c
@@ -247,9 +247,15 @@ void __iomem *ioremap_nocache (unsigned long phys_addr, unsigned long size)
         return __ioremap(phys_addr, size, _PAGE_PCD);
 }
 
+/**
+ * iounmap - Free a IO remapping
+ * @addr: virtual address from ioremap_*
+ *
+ * Caller must ensure there is only one unmapping for the same pointer.
+ */
 void iounmap(volatile void __iomem *addr)
 {
-        struct vm_struct *p;
+        struct vm_struct *p, *o;
 
         if (addr <= high_memory) 
                 return; 
@@ -257,12 +263,31 @@ void iounmap(volatile void __iomem *addr)
                 addr < phys_to_virt(ISA_END_ADDRESS))
                 return;
 
-        write_lock(&vmlist_lock);
-        p = __remove_vm_area((void *)((unsigned long)addr & PAGE_MASK));
-        if (!p)
+        addr = (volatile void *)(PAGE_MASK & (unsigned long __force)addr);
+        /* Use the vm area unlocked, assuming the caller
+           ensures there isn't another iounmap for the same address
+           in parallel. Reuse of the virtual address is prevented by
+           leaving it in the global lists until we're done with it.
+           cpa takes care of the direct mappings. */
+        read_lock(&vmlist_lock);
+        for (p = vmlist; p; p = p->next) {
+                if (p->addr == addr)
+                        break;
+        }
+        read_unlock(&vmlist_lock);
+
+        if (!p) {
                 printk("iounmap: bad address %p\n", addr);
-        else if (p->flags >> 20)
+                dump_stack();
+                return;
+        }
+
+        /* Reset the direct mapping. Can block */
+        if (p->flags >> 20)
                 ioremap_change_attr(p->phys_addr, p->size, 0);
-        write_unlock(&vmlist_lock);
+
+        /* Finally remove it */
+        o = remove_vm_area((void *)addr);
+        BUG_ON(p != o || o == NULL);
         kfree(p); 
 }