helper for inkernel opening of block devices

@@ -22,6 +22,7 @@
 #include <linux/mpage.h>
 #include <linux/mount.h>
 #include <linux/uio.h>
+#include <linux/namei.h>
 #include <asm/uaccess.h>
 
 

@@ -151,7 +152,7 @@
  * for a block special file file->f_dentry->d_inode->i_size is zero
  * so we compute the size by hand (just as in block_read/write above)
  */
-static loff_t block_llseek(struct file *file, loff_t offset, int origin)
+static loff_t blkdev_llseek(struct file *file, loff_t offset, int origin)
 {
 	/* ewww */
 	loff_t size = file->f_dentry->d_inode->i_bdev->bd_inode->i_size;

@@ -182,11 +183,9 @@
  *	since the vma has no handle.
  */
  
-static int block_fsync(struct file *filp, struct dentry *dentry, int datasync)
+static int blkdev_fsync(struct file *filp, struct dentry *dentry, int datasync)
 {
-	struct inode * inode = dentry->d_inode;
-
-	return sync_blockdev(inode->i_bdev);
+	return sync_blockdev(dentry->d_inode->i_bdev);
 }
 
 /*

@@ -764,11 +763,11 @@
 struct file_operations def_blk_fops = {
 	.open		= blkdev_open,
 	.release	= blkdev_close,
-	.llseek		= block_llseek,
+	.llseek		= blkdev_llseek,
 	.read		= generic_file_read,
 	.write		= blkdev_file_write,
 	.mmap		= generic_file_mmap,
-	.fsync		= block_fsync,
+	.fsync		= blkdev_fsync,
 	.ioctl		= blkdev_ioctl,
 	.readv		= generic_file_readv,
 	.writev		= generic_file_writev,

@@ -795,4 +794,63 @@
 
 	sprintf(buffer, "%s(%d,%d)", name, MAJOR(dev), MINOR(dev));
 	return buffer;
+}
+
+struct block_device *open_bdev_excl(char *path, int fl, int kind, void *holder)
+{
+	struct inode *inode;
+	struct block_device *bdev;
+	struct nameidata nd;
+	mode_t mode = FMODE_READ;
+	int error = 0;
+
+	if (!path || !*path)
+		return ERR_PTR(-EINVAL);
+
+	error = path_lookup(path, LOOKUP_FOLLOW, &nd);
+	if (error)
+		return ERR_PTR(error);
+
+	inode = nd.dentry->d_inode;
+	error = -ENOTBLK;
+	if (!S_ISBLK(inode->i_mode))
+		goto path_release;
+	error = -EACCES;
+	if (nd.mnt->mnt_flags & MNT_NODEV)
+		goto path_release;
+	error = bd_acquire(inode);
+	if (error)
+		goto path_release;
+	bdev = inode->i_bdev;
+
+	/* Done with lookups */
+	path_release(&nd);
+
+	if (!(fl & MS_RDONLY))
+		mode |= FMODE_WRITE;
+	error = blkdev_get(bdev, mode, 0, kind);
+	if (error)
+		return ERR_PTR(error);
+	error = -EACCES;
+	if (!(fl & MS_RDONLY) && bdev_read_only(bdev))
+		goto blkdev_put;
+	error = bd_claim(bdev, holder);
+	if (error)
+		goto blkdev_put;
+
+	return bdev;
+	
+blkdev_put:
+	blkdev_put(bdev, BDEV_FS);
+	return ERR_PTR(error);
+
+path_release:
+	path_release(&nd);
+	return ERR_PTR(error);
+}
+
+void close_bdev_excl(struct block_device *bdev, int kind)
+{
+	bd_release(bdev);
+	blkdev_put(bdev, kind);
 }

90 lines not on this page · raw message

@@ -1096,15 +1096,20 @@
 extern void bd_release(struct block_device *);
 extern void blk_run_queues(void);
 
-/* fs/devices.c */
+/* fs/char_dev.c */
 extern int register_chrdev(unsigned int, const char *, struct file_operations *);
 extern int unregister_chrdev(unsigned int, const char *);
 extern int chrdev_open(struct inode *, struct file *);
+
+/* fs/block_dev.c */
 extern const char *__bdevname(dev_t);
 extern inline const char *bdevname(struct block_device *bdev)
 {
 	return __bdevname(bdev->bd_dev);
 }
+extern struct block_device *open_bdev_excl(char *, int, int, void *);
+extern void close_bdev_excl(struct block_device *, int);
+
 extern const char * cdevname(kdev_t);
 extern const char * kdevname(kdev_t);
 extern void init_special_inode(struct inode *, umode_t, dev_t);

@@ -202,6 +202,8 @@
 EXPORT_SYMBOL(bdput);
 EXPORT_SYMBOL(bd_claim);
 EXPORT_SYMBOL(bd_release);
+EXPORT_SYMBOL(open_bdev_excl);
+EXPORT_SYMBOL(close_bdev_excl);
 EXPORT_SYMBOL(__brelse);
 EXPORT_SYMBOL(__bforget);
 EXPORT_SYMBOL(ll_rw_block);