Bug#600190: linux-image-2.6.32-5-amd64: btrfs filesystem df doesn't work because of missing ioctl

[Mike Hommey <mh@glandium.org>]

On Thu, Oct 14, 2010 at 03:26:08PM +0200, Mike Hommey wrote:
> Package: linux-2.6
> Version: 2.6.32-24
> Severity: normal
> 
> The btrfs tool, which is the canonical tool for btrfs handling, doesn't
> have a useful output for btrfs filesystem df because the necessay ioctl
> isn't available in 2.6.32. Would you consider adding it?
> 1406e4327be3a533a2b18582f715ce2cfbcf6804 is the relevant commit id.
> (7fde62bffb576d384ea49a3aed3403d5609ee5bc further modifies the ioctl
> function to buffer the output)

I can confirm backporting 1406e4327be3a533a2b18582f715ce2cfbcf6804
(attached) makes "btrfs filesystem df" work.

Mike

commit 278068037d34d4c030bd812849f1a0ffae53e3dc
Author: Josef Bacik <josef@redhat.com>
Date:   Wed Jan 13 18:19:06 2010 +0000

    Btrfs: add a "df" ioctl for btrfs
    
    df is a very loaded question in btrfs.  This gives us a way to get the per-space
    usage information so we can tell exactly what is in use where.  This will help
    us figure out ENOSPC problems, and help users better understand where their disk
    space is going.
    
    Signed-off-by: Josef Bacik <josef@redhat.com>
    Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index cdbb054..1e7a71d 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1270,6 +1270,49 @@ out:
 	return ret;
 }
 
+long btrfs_ioctl_space_info(struct btrfs_root *root, void __user *arg)
+{
+	struct btrfs_ioctl_space_args space_args;
+	struct btrfs_ioctl_space_info space;
+	struct btrfs_ioctl_space_info *dest;
+	struct btrfs_space_info *info;
+	int ret = 0;
+
+	if (copy_from_user(&space_args,
+			   (struct btrfs_ioctl_space_args __user *)arg,
+			   sizeof(space_args)))
+		return -EFAULT;
+
+	space_args.total_spaces = 0;
+	dest = (struct btrfs_ioctl_space_info *)
+		(arg + sizeof(struct btrfs_ioctl_space_args));
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(info, &root->fs_info->space_info, list) {
+		if (!space_args.space_slots) {
+			space_args.total_spaces++;
+			continue;
+		}
+		if (space_args.total_spaces >= space_args.space_slots)
+			break;
+		space.flags = info->flags;
+		space.total_bytes = info->total_bytes;
+		space.used_bytes = info->bytes_used;
+		if (copy_to_user(dest, &space, sizeof(space))) {
+			ret = -EFAULT;
+			break;
+		}
+		dest++;
+		space_args.total_spaces++;
+	}
+	rcu_read_unlock();
+
+	if (copy_to_user(arg, &space_args, sizeof(space_args)))
+		ret = -EFAULT;
+
+	return ret;
+}
+
 /*
  * there are many ways the trans_start and trans_end ioctls can lead
  * to deadlocks.  They should only be used by applications that
@@ -1334,6 +1377,8 @@ long btrfs_ioctl(struct file *file, unsigned int
 		return btrfs_ioctl_trans_start(file);
 	case BTRFS_IOC_TRANS_END:
 		return btrfs_ioctl_trans_end(file);
+	case BTRFS_IOC_SPACE_INFO:
+		return btrfs_ioctl_space_info(root, argp);
 	case BTRFS_IOC_SYNC:
 		btrfs_sync_fs(file->f_dentry->d_sb, 1);
 		return 0;
diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index bc49914..9893d02 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -36,6 +36,18 @@ struct btrfs_ioctl_clone_range_args {
   __u64 dest_offset;
 };
 
+struct btrfs_ioctl_space_info {
+	u64 flags;
+	u64 total_bytes;
+	u64 used_bytes;
+};
+
+struct btrfs_ioctl_space_args {
+	u64 space_slots;
+	u64 total_spaces;
+	struct btrfs_ioctl_space_info spaces[0];
+};
+
 #define BTRFS_IOC_SNAP_CREATE _IOW(BTRFS_IOCTL_MAGIC, 1, \
 				   struct btrfs_ioctl_vol_args)
 #define BTRFS_IOC_DEFRAG _IOW(BTRFS_IOCTL_MAGIC, 2, \
@@ -67,4 +79,6 @@ struct btrfs_ioctl_clone_range_args {
 				   struct btrfs_ioctl_vol_args)
 #define BTRFS_IOC_SNAP_DESTROY _IOW(BTRFS_IOCTL_MAGIC, 15, \
 				struct btrfs_ioctl_vol_args)
+#define BTRFS_IOC_SPACE_INFO _IOWR(BTRFS_IOCTL_MAGIC, 20, \
+				    struct btrfs_ioctl_space_args)
 #endif