dm ioctl: optimize functions without variable params

Device-mapper ioctls receive and send data in a buffer supplied
by userspace.  The buffer has two parts.  The first part contains
a 'struct dm_ioctl' and has a fixed size.  The second part depends
on the ioctl and has a variable size.

This patch recognises the specific ioctls that do not use the variable
part of the buffer and skips allocating memory for it.

In particular, when a device is suspended and a resume ioctl is sent,
this now avoid memory allocation completely.

The variable "struct dm_ioctl tmp" is moved from the function
copy_params to its caller ctl_ioctl and renamed to param_kernel.
It is used directly when the ioctl function doesn't need any arguments.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 9ae11b2..7eb0682 100644 (file)
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1560,7 +1560,8 @@ static int check_version(unsigned int cmd, struct dm_ioctl __user *user)
        return r;
 }
 
-#define DM_PARAMS_VMALLOC      0x0001  /* Params alloced with vmalloc not kmalloc */
+#define DM_PARAMS_KMALLOC      0x0001  /* Params alloced with kmalloc */
+#define DM_PARAMS_VMALLOC      0x0002  /* Params alloced with vmalloc */
 #define DM_WIPE_BUFFER         0x0010  /* Wipe input buffer before returning from ioctl */
 
 static void free_params(struct dm_ioctl *param, size_t param_size, int param_flags)
@@ -1568,66 +1569,80 @@ static void free_params(struct dm_ioctl *param, size_t param_size, int param_fla
        if (param_flags & DM_WIPE_BUFFER)
                memset(param, 0, param_size);
 
+       if (param_flags & DM_PARAMS_KMALLOC)
+               kfree(param);
        if (param_flags & DM_PARAMS_VMALLOC)
                vfree(param);
-       else
-               kfree(param);
 }
 
-static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl **param, int *param_flags)
+static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kernel,
+                      int ioctl_flags,
+                      struct dm_ioctl **param, int *param_flags)
 {
-       struct dm_ioctl tmp, *dmi;
+       struct dm_ioctl *dmi;
        int secure_data;
+       const size_t minimum_data_size = sizeof(*param_kernel) - sizeof(param_kernel->data);
 
-       if (copy_from_user(&tmp, user, sizeof(tmp) - sizeof(tmp.data)))
+       if (copy_from_user(param_kernel, user, minimum_data_size))
                return -EFAULT;
 
-       if (tmp.data_size < (sizeof(tmp) - sizeof(tmp.data)))
+       if (param_kernel->data_size < minimum_data_size)
                return -EINVAL;
 
-       secure_data = tmp.flags & DM_SECURE_DATA_FLAG;
+       secure_data = param_kernel->flags & DM_SECURE_DATA_FLAG;
 
        *param_flags = secure_data ? DM_WIPE_BUFFER : 0;
 
+       if (ioctl_flags & IOCTL_FLAGS_NO_PARAMS) {
+               dmi = param_kernel;
+               dmi->data_size = minimum_data_size;
+               goto data_copied;
+       }
+
        /*
         * Try to avoid low memory issues when a device is suspended.
         * Use kmalloc() rather than vmalloc() when we can.
         */
        dmi = NULL;
-       if (tmp.data_size <= KMALLOC_MAX_SIZE)
-               dmi = kmalloc(tmp.data_size, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
+       if (param_kernel->data_size <= KMALLOC_MAX_SIZE) {
+               dmi = kmalloc(param_kernel->data_size, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
+               if (dmi)
+                       *param_flags |= DM_PARAMS_KMALLOC;
+       }
 
        if (!dmi) {
-               dmi = __vmalloc(tmp.data_size, GFP_NOIO | __GFP_REPEAT | __GFP_HIGH, PAGE_KERNEL);
-               *param_flags |= DM_PARAMS_VMALLOC;
+               dmi = __vmalloc(param_kernel->data_size, GFP_NOIO | __GFP_REPEAT | __GFP_HIGH, PAGE_KERNEL);
+               if (dmi)
+                       *param_flags |= DM_PARAMS_VMALLOC;
        }
 
        if (!dmi) {
-               if (secure_data && clear_user(user, tmp.data_size))
+               if (secure_data && clear_user(user, param_kernel->data_size))
                        return -EFAULT;
                return -ENOMEM;
        }
 
-       if (copy_from_user(dmi, user, tmp.data_size))
+       if (copy_from_user(dmi, user, param_kernel->data_size))
                goto bad;
 
+data_copied:
        /*
         * Abort if something changed the ioctl data while it was being copied.
         */
-       if (dmi->data_size != tmp.data_size) {
+       if (dmi->data_size != param_kernel->data_size) {
                DMERR("rejecting ioctl: data size modified while processing parameters");
                goto bad;
        }
 
        /* Wipe the user buffer so we do not return it to userspace */
-       if (secure_data && clear_user(user, tmp.data_size))
+       if (secure_data && clear_user(user, param_kernel->data_size))
                goto bad;
 
        *param = dmi;
        return 0;
 
 bad:
-       free_params(dmi, tmp.data_size, *param_flags);
+       free_params(dmi, param_kernel->data_size, *param_flags);
 
        return -EFAULT;
 }
@@ -1671,6 +1686,7 @@ static int ctl_ioctl(uint command, struct dm_ioctl __user *user)
        struct dm_ioctl *uninitialized_var(param);
        ioctl_fn fn = NULL;
        size_t input_param_size;
+       struct dm_ioctl param_kernel;
 
        /* only root can play with this */
        if (!capable(CAP_SYS_ADMIN))
@@ -1704,7 +1720,7 @@ static int ctl_ioctl(uint command, struct dm_ioctl __user *user)
        /*
         * Copy the parameters into kernel space.
         */
-       r = copy_params(user, &param, &param_flags);
+       r = copy_params(user, &param_kernel, ioctl_flags, &param, &param_flags);
 
        if (r)
                return r;

diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h
index 539b179..b8a6bdd 100644 (file)
--- a/include/uapi/linux/dm-ioctl.h
+++ b/include/uapi/linux/dm-ioctl.h
@@ -267,9 +267,9 @@ enum {
 #define DM_DEV_SET_GEOMETRY    _IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)
 
 #define DM_VERSION_MAJOR       4
-#define DM_VERSION_MINOR       23
-#define DM_VERSION_PATCHLEVEL  1
-#define DM_VERSION_EXTRA       "-ioctl (2012-12-18)"
+#define DM_VERSION_MINOR       24
+#define DM_VERSION_PATCHLEVEL  0
+#define DM_VERSION_EXTRA       "-ioctl (2013-01-15)"
 
 /* Status bits */
 #define DM_READONLY_FLAG       (1 << 0) /* In/Out */