[PATCH] uml: allow ubd devices to be shared in a cluster

This adds a 'c' option to the ubd switch which turns off host file locking so
that the device can be shared, as with a cluster.  There's also some
whitespace cleanup while I was in this file.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/um/drivers/ubd_kern.c

@@ -71,7 +71,7 @@ struct io_thread_req {
 	int error;
 };
 
-extern int open_ubd_file(char *file, struct openflags *openflags,
+extern int open_ubd_file(char *file, struct openflags *openflags, int shared,
 			 char **backing_file_out, int *bitmap_offset_out,
 			 unsigned long *bitmap_len_out, int *data_offset_out,
 			 int *create_cow_out);
@@ -168,6 +168,7 @@ struct ubd {
 	__u64 size;
 	struct openflags boot_openflags;
 	struct openflags openflags;
+	int shared;
 	int no_cow;
 	struct cow cow;
 	struct platform_device pdev;
@@ -189,6 +190,7 @@ struct ubd {
 	.boot_openflags =	OPEN_FLAGS, \
 	.openflags =		OPEN_FLAGS, \
         .no_cow =               0, \
+	.shared =		0, \
         .cow =			DEFAULT_COW, \
 }
 
@@ -351,7 +353,7 @@ static int ubd_setup_common(char *str, int *index_out)
 	if (index_out)
 		*index_out = n;
 
-	for (i = 0; i < 4; i++) {
+	for (i = 0; i < sizeof("rscd="); i++) {
 		switch (*str) {
 		case 'r':
 			flags.w = 0;
@@ -362,11 +364,14 @@ static int ubd_setup_common(char *str, int *index_out)
 		case 'd':
 			dev->no_cow = 1;
 			break;
+		case 'c':
+			dev->shared = 1;
+			break;
 		case '=':
 			str++;
 			goto break_loop;
 		default:
-			printk(KERN_ERR "ubd_setup : Expected '=' or flag letter (r,s or d)\n");
+			printk(KERN_ERR "ubd_setup : Expected '=' or flag letter (r, s, c, or d)\n");
 			goto out;
 		}
 		str++;
@@ -567,9 +572,10 @@ static int ubd_open_dev(struct ubd *dev)
 	create_cow = 0;
 	create_ptr = (dev->cow.file != NULL) ? &create_cow : NULL;
 	back_ptr = dev->no_cow ? NULL : &dev->cow.file;
-	dev->fd = open_ubd_file(dev->file, &dev->openflags, back_ptr,
-				&dev->cow.bitmap_offset, &dev->cow.bitmap_len, 
-				&dev->cow.data_offset, create_ptr);
+	dev->fd = open_ubd_file(dev->file, &dev->openflags, dev->shared,
+				back_ptr, &dev->cow.bitmap_offset,
+				&dev->cow.bitmap_len, &dev->cow.data_offset,
+				create_ptr);
 
 	if((dev->fd == -ENOENT) && create_cow){
 		dev->fd = create_cow_file(dev->file, dev->cow.file,
@@ -606,8 +612,8 @@ static int ubd_open_dev(struct ubd *dev)
 
 		flags = dev->openflags;
 		flags.w = 0;
-		err = open_ubd_file(dev->cow.file, &flags, NULL, NULL, NULL, 
-				    NULL, NULL);
+		err = open_ubd_file(dev->cow.file, &flags, dev->shared, NULL,
+				    NULL, NULL, NULL, NULL);
 		if(err < 0) goto error;
 		dev->cow.fd = err;
 	}
@@ -1182,7 +1188,7 @@ int read_cow_bitmap(int fd, void *buf, int offset, int len)
 	return(0);
 }
 
-int open_ubd_file(char *file, struct openflags *openflags,
+int open_ubd_file(char *file, struct openflags *openflags, int shared,
 		  char **backing_file_out, int *bitmap_offset_out,
 		  unsigned long *bitmap_len_out, int *data_offset_out,
 		  int *create_cow_out)
@@ -1206,11 +1212,15 @@ int open_ubd_file(char *file, struct openflags *openflags,
 			return fd;
         }
 
+	if(shared)
+		printk("Not locking \"%s\" on the host\n", file);
+	else {
 		err = os_lock_file(fd, openflags->w);
 		if(err < 0){
 			printk("Failed to lock '%s', err = %d\n", file, -err);
 			goto out_close;
 		}
+	}
 
 	/* Succesful return case! */
 	if(backing_file_out == NULL)
@@ -1260,7 +1270,7 @@ int create_cow_file(char *cow_file, char *backing_file, struct openflags flags,
 	int err, fd;
 
 	flags.c = 1;
-	fd = open_ubd_file(cow_file, &flags, NULL, NULL, NULL, NULL, NULL);
+	fd = open_ubd_file(cow_file, &flags, 0, NULL, NULL, NULL, NULL, NULL);
 	if(fd < 0){
 		err = fd;
 		printk("Open of COW file '%s' failed, errno = %d\n", cow_file,