[PATCH] device-mapper ioctl: add skip lock_fs flag

Add ioctl DM_SKIP_LOCKFS_FLAG for userspace to request that lock_fs is
bypassed when suspending a device.

There's no change to the behaviour of existing code that doesn't know about
the new flag.
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/md/dm-ioctl.c

@@ -693,14 +693,18 @@ static int dev_rename(struct dm_ioctl *param, size_t param_size)
 static int do_suspend(struct dm_ioctl *param)
 {
 	int r = 0;
+	int do_lockfs = 1;
 	struct mapped_device *md;
 
 	md = find_device(param);
 	if (!md)
 		return -ENXIO;
 
+	if (param->flags & DM_SKIP_LOCKFS_FLAG)
+		do_lockfs = 0;
+
 	if (!dm_suspended(md))
-		r = dm_suspend(md, 1);
+		r = dm_suspend(md, do_lockfs);
 
 	if (!r)
 		r = __dev_status(md, param);
@@ -712,6 +716,7 @@ static int do_suspend(struct dm_ioctl *param)
 static int do_resume(struct dm_ioctl *param)
 {
 	int r = 0;
+	int do_lockfs = 1;
 	struct hash_cell *hc;
 	struct mapped_device *md;
 	struct dm_table *new_map;
@@ -737,8 +742,10 @@ static int do_resume(struct dm_ioctl *param)
 	/* Do we need to load a new map ? */
 	if (new_map) {
 		/* Suspend if it isn't already suspended */
+		if (param->flags & DM_SKIP_LOCKFS_FLAG)
+			do_lockfs = 0;
 		if (!dm_suspended(md))
-			dm_suspend(md, 1);
+			dm_suspend(md, do_lockfs);
 
 		r = dm_swap_table(md, new_map);
 		if (r) {

include/linux/dm-ioctl.h

@@ -272,9 +272,9 @@ typedef char ioctl_struct[308];
 #define DM_TARGET_MSG	 _IOWR(DM_IOCTL, DM_TARGET_MSG_CMD, struct dm_ioctl)
 
 #define DM_VERSION_MAJOR	4
-#define DM_VERSION_MINOR	4
+#define DM_VERSION_MINOR	5
 #define DM_VERSION_PATCHLEVEL	0
-#define DM_VERSION_EXTRA	"-ioctl (2005-01-12)"
+#define DM_VERSION_EXTRA	"-ioctl (2005-10-04)"
 
 /* Status bits */
 #define DM_READONLY_FLAG	(1 << 0) /* In/Out */
@@ -301,8 +301,13 @@ typedef char ioctl_struct[308];
 #define DM_BUFFER_FULL_FLAG	(1 << 8) /* Out */
 
 /*
- * Set this to improve performance when you aren't going to use open_count
+ * Set this to improve performance when you aren't going to use open_count.
  */
 #define DM_SKIP_BDGET_FLAG	(1 << 9) /* In */
 
+/*
+ * Set this to avoid attempting to freeze any filesystem when suspending.
+ */
+#define DM_SKIP_LOCKFS_FLAG	(1 << 10) /* In */
+
 #endif				/* _LINUX_DM_IOCTL_H */