Re: [PATCH] Btrfs: add a "df" ioctl for btrfs

[Josef Bacik <josef@redhat.com>]

On Tue, Jan 12, 2010 at 03:25:13PM -0500, Josef Bacik wrote:
> 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.
> 

Sorry, here's one without my debugging printk still sitting there.  Thanks,

Josef

---
 fs/btrfs/ioctl.c |   45 +++++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/ioctl.h |   15 ++++++++++++++-
 2 files changed, 59 insertions(+), 1 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 9070b86..7405e42 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1623,6 +1623,49 @@ static long btrfs_ioctl_default_subvol(struct file *file, void __user *argp)
 	return 0;
 }
 
+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
@@ -1691,6 +1734,8 @@ long btrfs_ioctl(struct file *file, unsigned int
 		return btrfs_ioctl_trans_end(file);
 	case BTRFS_IOC_SNAP_LISTING:
 		return btrfs_ioctl_snap_listing(file, argp);
+	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 9e5074c..850e0ee 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -54,6 +54,18 @@ struct btrfs_ioctl_subvol_leaf {
 	struct btrfs_ioctl_subvol_items items[];
 };
 
+struct btrfs_ioctl_space_info {
+	u32 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_SUBVOL_LEAF_SIZE_MIN sizeof(struct btrfs_ioctl_subvol_leaf) + \
 	sizeof(struct btrfs_ioctl_subvol_items)
 
@@ -97,5 +109,6 @@ struct btrfs_ioctl_clone_range_args {
 #define BTRFS_IOC_SNAP_LISTING _IOWR(BTRFS_IOCTL_MAGIC, 16, \
 				   struct btrfs_ioctl_subvol_args)
 #define BTRFS_IOC_DEFAULT_SUBVOL _IOW(BTRFS_IOCTL_MAGIC, 17, u64)
-
+#define BTRFS_IOC_SPACE_INFO _IOWR(BTRFS_IOCTL_MAGIC, 18, \
+				    struct btrfs_ioctl_space_args)
 #endif
-- 
1.5.4.3