[PATCH] Remove BKL from PCI syscalls

[Matthew Wilcox <matthew@wil.cx>]

Remove use of the BKL from the PCI syscalls.  It was protecting against
PCI device removal.  By taking a reference (using pci_get_slot), we
ensure the device will not be removed while we're using it, and can
remove the BKL.

While I'm in this file, update the comment at the top to reflect the
status of the syscalls.

Signed-off-by: Matthew Wilcox <matthew@wil.cx>

diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c
index 9d37fec..56dc193 100644
--- a/drivers/pci/syscall.c
+++ b/drivers/pci/syscall.c
@@ -1,10 +1,13 @@
 /*
  *	pci_syscall.c
  *
- * For architectures where we want to allow direct access
- * to the PCI config stuff - it would probably be preferable
- * on PCs too, but there people just do it by hand with the
- * magic northbridge registers..
+ * This is a legacy method for accessing PCI config space on some
+ * architectures.  These days, everybody should be using sysfs or procfs
+ * which allow non-privileged users to read the safe bits of config space,
+ * but we can't remove these syscalls.  These syscalls do not allow access
+ * to PCI domains other than zero, and while it would be possible to add
+ * that support, it is better to migrate any userspace application to use
+ * the sysfs method.
  */
 
 #include <linux/errno.h>
@@ -25,16 +28,13 @@ sys_pciconfig_read(unsigned long bus, unsigned long dfn,
 	u32 dword;
 	long err, cfg_ret;
 
-	err = -EPERM;
 	if (!capable(CAP_SYS_ADMIN))
-		goto error;
+		return -EPERM;
 
-	err = -ENODEV;
-	dev = pci_find_slot(bus, dfn);
+	dev = pci_get_slot(pci_find_bus(0, bus), dfn);
 	if (!dev)
-		goto error;
+		return -ENODEV;
 
-	lock_kernel();
 	switch (len) {
 	case 1:
 		cfg_ret = pci_user_read_config_byte(dev, off, &byte);
@@ -47,10 +47,8 @@ sys_pciconfig_read(unsigned long bus, unsigned long dfn,
 		break;
 	default:
 		err = -EINVAL;
-		unlock_kernel();
 		goto error;
 	};
-	unlock_kernel();
 
 	err = -EIO;
 	if (cfg_ret != PCIBIOS_SUCCESSFUL)
@@ -67,9 +65,10 @@ sys_pciconfig_read(unsigned long bus, unsigned long dfn,
 		err = put_user(dword, (unsigned int __user *)buf);
 		break;
 	};
-	return err;
 
-error:
+	goto out;
+
+ error:
 	/* ??? XFree86 doesn't even check the return value.  They
 	   just look for 0xffffffff in the output, since that's what
 	   they get instead of a machine check on x86.  */
@@ -84,6 +83,8 @@ error:
 		put_user(-1, (unsigned int __user *)buf);
 		break;
 	};
+ out:
+	pci_dev_put(dev);
 	return err;
 }
 
@@ -101,11 +102,10 @@ sys_pciconfig_write(unsigned long bus, unsigned long dfn,
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	dev = pci_find_slot(bus, dfn);
+	dev = pci_get_slot(pci_find_bus(0, bus), dfn);
 	if (!dev)
 		return -ENODEV;
 
-	lock_kernel();
 	switch(len) {
 	case 1:
 		err = get_user(byte, (u8 __user *)buf);
@@ -138,7 +138,7 @@ sys_pciconfig_write(unsigned long bus, unsigned long dfn,
 		err = -EINVAL;
 		break;
 	};
-	unlock_kernel();
 
+	pci_dev_put(dev);
 	return err;
 }

-- 
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."