On Thu, 23 Aug 2012 14:12:59 +0200, Goffredo Baroncelli wrote:

Export via sysfs some information about the btrfs devices and
filesystem.
---
 fs/btrfs/super.c |    4 
 fs/btrfs/sysfs.c |  933 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/sysfs.h |   31 ++
 3 files changed, 963 insertions(+), 5 deletions(-)
 create mode 100644 fs/btrfs/sysfs.h

Hi Goffredo,

The Signed-off-by line is missing, it is mandatory.

[...]

+struct btrfs_sysfs_fsid {
+		struct kobject			*kobj;
+		struct list_head		list;
+		u8						fsid[BTRFS_FSID_SIZE];
+};

Tabsize needs to be 8.

+static struct list_head btrfs_sysfs_device_list;
+static struct list_head btrfs_sysfs_fs_devices_list;
+static struct list_head btrfs_sysfs_filesystem_list;
+static struct list_head btrfs_sysfs_fsid_list;
+
+
+void uuid_unparse( u8 *uuid, char *out ){
+	static char *i2x = "0123456789abcdef";
+	static int 	lengths[] = {4,2,2,2,6,0};
+	int 		i;
+	
+	for(i=0; ; i++){
+		int j;
+		for(j=0; j < lengths[i] ; j++, uuid++){
+			*out++ = i2x[*uuid >> 4];
+			*out++ = i2x[*uuid & 0x0f];
+		}
+		if( !lengths[i+1] ){
+			*out = 0;
+			break;
+		}else{
+			*out++ = '-';
+		}
+	}
+}

All the missing spaces and all the spaces that are too much...
One line contains a trailing TAB character before the end of the line.
A newline is missing before the opening curly bracket of the function body.
An empty line between the 'int j;' and the code is common, like the one
after the 'int i;'.

[more lines deleted...]

Please refer to:
Documentation/SubmittingPatches
Documentation/SubmitChecklist
Documentation/CodingStyle

And apply:
scripts/checkpatch.pl

I did not look at the patch itself after noticing the style issues.