Linux 2.1.107pre2

Are there people out there that use the loopback device with SMP, and have
been irritated at it not working lately?
I gave up on waiting for any real loop device maintainer to step up and
fix this, so I made a very small patch that I suspect may fix the problem.
I'm not going to test it myself, and I'm fairly disgusted with how badly
the loop device is being maintained at all. But if people feel they want
to test it out, go to

        ftp.kernel.org//pub/linux/kernel/testing

and fetch the current pre-107-2 patch.
It also has some other patches to the loop device that I picked up and
that looked like the right thing to do (use dentry pointers instead of
inodes to make mount/umount happy.

                Linus

drivers/block/loop.c

@@ -166,8 +166,8 @@ static void figure_loop_size(struct loop_device *lo)
 {
 	int	size;
 
-	if (S_ISREG(lo->lo_inode->i_mode))
-		size = (lo->lo_inode->i_size - lo->lo_offset) / BLOCK_SIZE;
+	if (S_ISREG(lo->lo_dentry->d_inode->i_mode))
+		size = (lo->lo_dentry->d_inode->i_size - lo->lo_offset) / BLOCK_SIZE;
 	else {
 		kdev_t lodev = lo->lo_device;
 		if (blk_size[MAJOR(lodev)])
@@ -195,7 +195,7 @@ static void do_lo_request(void)
 	if (MINOR(current_request->rq_dev) >= MAX_LOOP)
 		goto error_out;
 	lo = &loop_dev[MINOR(current_request->rq_dev)];
-	if (!lo->lo_inode || !lo->transfer)
+	if (!lo->lo_dentry || !lo->transfer)
 		goto error_out;
 
 	blksize = BLOCK_SIZE;
@@ -229,13 +229,14 @@ static void do_lo_request(void)
 		printk("unknown loop device command (%d)?!?", current_request->cmd);
 		goto error_out;
 	}
+	spin_unlock_irq(&io_request_lock);
 	while (len > 0) {
 		real_block = block;
 		if (lo->lo_flags & LO_FLAGS_DO_BMAP) {
-			real_block = bmap(lo->lo_inode, block);
+			real_block = bmap(lo->lo_dentry->d_inode, block);
 			if (!real_block) {
 				printk("loop: block %d not present\n", block);
-				goto error_out;
+				goto error_out_lock;
 			}
 		}
 		bh = getblk(lo->lo_device, real_block, blksize);
@@ -243,7 +244,7 @@ static void do_lo_request(void)
 			printk("loop: device %s: getblk(-, %d, %d) returned NULL",
 			       kdevname(lo->lo_device),
 			       block, blksize);
-			goto error_out;
+			goto error_out_lock;
 		}
 		if (!buffer_uptodate(bh) && ((current_request->cmd == READ) ||
 					(offset || (len < blksize)))) {
@@ -251,7 +252,7 @@ static void do_lo_request(void)
 			wait_on_buffer(bh);
 			if (!buffer_uptodate(bh)) {
 				brelse(bh);
-				goto error_out;
+				goto error_out_lock;
 			}
 		}
 		size = blksize - offset;
@@ -262,7 +263,7 @@ static void do_lo_request(void)
 				   dest_addr, size)) {
 			printk("loop: transfer error block %d\n", block);
 			brelse(bh);
-			goto error_out;
+			goto error_out_lock;
 		}
 		if (current_request->cmd == WRITE) {
 			mark_buffer_uptodate(bh, 1);
@@ -274,10 +275,13 @@ static void do_lo_request(void)
 		offset = 0;
 		block++;
 	}
+	spin_lock_irq(&io_request_lock);
 	current_request->next=CURRENT;
 	CURRENT=current_request;
 	end_request(1);
 	goto repeat;
+error_out_lock:
+	spin_lock_irq(&io_request_lock);
 error_out:
 	current_request->next=CURRENT;
 	CURRENT=current_request;
@@ -292,15 +296,16 @@ static int loop_set_fd(struct loop_device *lo, kdev_t dev, unsigned int arg)
 	int error;
 
 	MOD_INC_USE_COUNT;
+
+	error = -EBUSY;
+	if (lo->lo_dentry)
+		goto out;
+
 	error = -EBADF;
 	file = fget(arg);
 	if (!file)
 		goto out;
 
-	error = -EBUSY;
-	if (lo->lo_inode)
-		goto out_putf;
-
 	error = -EINVAL;
 	inode = file->f_dentry->d_inode;
 	if (!inode) {
@@ -328,9 +333,8 @@ static int loop_set_fd(struct loop_device *lo, kdev_t dev, unsigned int arg)
 		set_device_ro(dev, 0);
 	}
 
-	/* N.B. Should keep the file or dentry ... */
-	inode->i_count++;
-	lo->lo_inode = inode;
+	lo->lo_dentry = file->f_dentry;
+	lo->lo_dentry->d_count++;
 	lo->transfer = NULL;
 	figure_loop_size(lo);
 
@@ -344,17 +348,17 @@ static int loop_set_fd(struct loop_device *lo, kdev_t dev, unsigned int arg)
 
 static int loop_clr_fd(struct loop_device *lo, kdev_t dev)
 {
-	struct inode *inode = lo->lo_inode;
+	struct dentry *dentry = lo->lo_dentry;
 
-	if (!inode)
+	if (!dentry)
 		return -ENXIO;
 	if (lo->lo_refcnt > 1)	/* we needed one fd for the ioctl */
 		return -EBUSY;
 
-	if (S_ISBLK(inode->i_mode))
-		blkdev_release (inode);
-	lo->lo_inode = NULL;
-	iput(inode);
+	if (S_ISBLK(dentry->d_inode->i_mode))
+		blkdev_release (dentry->d_inode);
+	lo->lo_dentry = NULL;
+	dput(dentry);
 	lo->lo_device = 0;
 	lo->lo_encrypt_type = 0;
 	lo->lo_offset = 0;
@@ -372,7 +376,7 @@ static int loop_set_status(struct loop_device *lo, struct loop_info *arg)
 	struct loop_info info;
 	int err;
 
-	if (!lo->lo_inode)
+	if (!lo->lo_dentry)
 		return -ENXIO;
 	if (!arg)
 		return -EINVAL;
@@ -432,7 +436,7 @@ static int loop_get_status(struct loop_device *lo, struct loop_info *arg)
 	struct loop_info	info;
 	int err;
 	
-	if (!lo->lo_inode)
+	if (!lo->lo_dentry)
 		return -ENXIO;
 	if (!arg)
 		return -EINVAL;
@@ -441,8 +445,8 @@ static int loop_get_status(struct loop_device *lo, struct loop_info *arg)
 		return err;
 	memset(&info, 0, sizeof(info));
 	info.lo_number = lo->lo_number;
-	info.lo_device = kdev_t_to_nr(lo->lo_inode->i_dev);
-	info.lo_inode = lo->lo_inode->i_ino;
+	info.lo_device = kdev_t_to_nr(lo->lo_dentry->d_inode->i_dev);
+	info.lo_inode = lo->lo_dentry->d_inode->i_ino;
 	info.lo_rdevice = kdev_t_to_nr(lo->lo_device);
 	info.lo_offset = lo->lo_offset;
 	info.lo_flags = lo->lo_flags;
@@ -483,7 +487,7 @@ static int lo_ioctl(struct inode * inode, struct file * file,
 	case LOOP_GET_STATUS:
 		return loop_get_status(lo, (struct loop_info *) arg);
 	case BLKGETSIZE:   /* Return device size */
-		if (!lo->lo_inode)
+		if (!lo->lo_dentry)
 			return -ENXIO;
 		if (!arg)
 			return -EINVAL;

include/linux/loop.h

@@ -17,7 +17,7 @@
        
 struct loop_device {
 	int		lo_number;
-	struct inode	*lo_inode;
+	struct dentry	*lo_dentry;
 	int		lo_refcnt;
 	kdev_t		lo_device;
 	int		lo_offset;