[PATCH] block: add unlocked_ioctl support for block devices

This patch allows block device drivers to convert their ioctl functions to
unlocked_ioctl() like character devices and other subsystems.  All
functions that were called with the BKL held before are still used that
way, but I would not be surprised if it could be removed from the ioctl
functions in drivers/block/ioctl.c themselves.

As a side note, I found that compat_blkdev_ioctl() acquires the BKL as
well, which looks like a bug.  I have checked that every user of
disk->fops->compat_ioctl() in the current git tree gets the BKL itself, so
it could easily be removed from compat_blkdev_ioctl().

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 57 insertions, 23 deletions

diff --git a/drivers/block/ioctl.c b/drivers/block/ioctl.c
index 6d7bcc9da9e7..6e278474f9a8 100644
--- a/drivers/block/ioctl.c
+++ b/drivers/block/ioctl.c
@@ -133,11 +133,9 @@ static int put_u64(unsigned long arg, u64 val)
         return put_user(val, (u64 __user *)arg);
 }
 
-int blkdev_ioctl(struct inode *inode, struct file *file, unsigned cmd,
-                        unsigned long arg)
+static int blkdev_locked_ioctl(struct file *file, struct block_device *bdev,
+                                unsigned cmd, unsigned long arg)
 {
-        struct block_device *bdev = inode->i_bdev;
-        struct gendisk *disk = bdev->bd_disk;
         struct backing_dev_info *bdi;
         int ret, n;
 
@@ -190,36 +188,72 @@ int blkdev_ioctl(struct inode *inode, struct file *file, unsigned cmd,
                 return put_ulong(arg, bdev->bd_inode->i_size >> 9);
         case BLKGETSIZE64:
                 return put_u64(arg, bdev->bd_inode->i_size);
+        }
+        return -ENOIOCTLCMD;
+}
+
+static int blkdev_driver_ioctl(struct inode *inode, struct file *file,
+                struct gendisk *disk, unsigned cmd, unsigned long arg)
+{
+        int ret;
+        if (disk->fops->unlocked_ioctl)
+                return disk->fops->unlocked_ioctl(file, cmd, arg);
+
+        if (disk->fops->ioctl) {
+                lock_kernel();
+                ret = disk->fops->ioctl(inode, file, cmd, arg);
+                unlock_kernel();
+                return ret;
+        }
+
+        return -ENOTTY;
+}
+
+int blkdev_ioctl(struct inode *inode, struct file *file, unsigned cmd,
+                        unsigned long arg)
+{
+        struct block_device *bdev = inode->i_bdev;
+        struct gendisk *disk = bdev->bd_disk;
+        int ret, n;
+
+        switch(cmd) {
         case BLKFLSBUF:
                 if (!capable(CAP_SYS_ADMIN))
                         return -EACCES;
-                if (disk->fops->ioctl) {
-                        ret = disk->fops->ioctl(inode, file, cmd, arg);
-                        /* -EINVAL to handle old uncorrected drivers */
-                        if (ret != -EINVAL && ret != -ENOTTY)
-                                return ret;
-                }
+
+                ret = blkdev_driver_ioctl(inode, file, disk, cmd, arg);
+                /* -EINVAL to handle old uncorrected drivers */
+                if (ret != -EINVAL && ret != -ENOTTY)
+                        return ret;
+
+                lock_kernel();
                 fsync_bdev(bdev);
                 invalidate_bdev(bdev, 0);
+                unlock_kernel();
                 return 0;
+
         case BLKROSET:
-                if (disk->fops->ioctl) {
-                        ret = disk->fops->ioctl(inode, file, cmd, arg);
-                        /* -EINVAL to handle old uncorrected drivers */
-                        if (ret != -EINVAL && ret != -ENOTTY)
-                                return ret;
-                }
+                ret = blkdev_driver_ioctl(inode, file, disk, cmd, arg);
+                /* -EINVAL to handle old uncorrected drivers */
+                if (ret != -EINVAL && ret != -ENOTTY)
+                        return ret;
                 if (!capable(CAP_SYS_ADMIN))
                         return -EACCES;
                 if (get_user(n, (int __user *)(arg)))
                         return -EFAULT;
+                lock_kernel();
                 set_device_ro(bdev, n);
+                unlock_kernel();
                 return 0;
-        default:
-                if (disk->fops->ioctl)
-                        return disk->fops->ioctl(inode, file, cmd, arg);
         }
-        return -ENOTTY;
+
+        lock_kernel();
+        ret = blkdev_locked_ioctl(file, bdev, cmd, arg);
+        unlock_kernel();
+        if (ret != -ENOIOCTLCMD)
+                return ret;
+
+        return blkdev_driver_ioctl(inode, file, disk, cmd, arg);
 }
 
 /* Most of the generic ioctls are handled in the normal fallback path.
diff --git a/fs/block_dev.c b/fs/block_dev.c
index c0cbd1bc1a02..e0df94c37b7e 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -777,8 +777,7 @@ static ssize_t blkdev_file_aio_write(struct kiocb *iocb, const char __user *buf,
         return generic_file_aio_write_nolock(iocb, &local_iov, 1, &iocb->ki_pos);
 }
 
-static int block_ioctl(struct inode *inode, struct file *file, unsigned cmd,
-                        unsigned long arg)
+static long block_ioctl(struct file *file, unsigned cmd, unsigned long arg)
 {
         return blkdev_ioctl(file->f_mapping->host, file, cmd, arg);
 }
@@ -803,7 +802,7 @@ struct file_operations def_blk_fops = {
         .aio_write      = blkdev_file_aio_write, 
         .mmap           = generic_file_mmap,
         .fsync          = block_fsync,
-        .ioctl          = block_ioctl,
+        .unlocked_ioctl = block_ioctl,
 #ifdef CONFIG_COMPAT
         .compat_ioctl   = compat_blkdev_ioctl,
 #endif
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3622e952e98c..9b1278e21279 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -884,6 +884,7 @@ struct block_device_operations {
         int (*open) (struct inode *, struct file *);
         int (*release) (struct inode *, struct file *);
         int (*ioctl) (struct inode *, struct file *, unsigned, unsigned long);
+        long (*unlocked_ioctl) (struct file *, unsigned, unsigned long);
         long (*compat_ioctl) (struct file *, unsigned, unsigned long);
         int (*media_changed) (struct gendisk *);
         int (*revalidate_disk) (struct gendisk *);