Hugo Mills wrote:
> This patch adds an ioctl for cancelling a btrfs balance operation
> mid-flight. The ioctl simply sets a flag, and the operation terminates
> after the current block group move has completed.
>
> Signed-off-by: Hugo Mills <hugo@xxxxxxxxxxxxx>
> ---
> fs/btrfs/ctree.h | 1 +
> fs/btrfs/ioctl.c | 28 ++++++++++++++++++++++++++++
> fs/btrfs/ioctl.h | 1 +
> fs/btrfs/volumes.c | 7 ++++++-
> 4 files changed, 36 insertions(+), 1 deletions(-)
>
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index 25aa3cf..5031085 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -876,6 +876,7 @@ struct btrfs_block_group_cache {
> struct btrfs_balance_info {
> u32 expected;
> u32 completed;
> + int cancel_pending;
> };
>
> struct reloc_control;
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 5ddf816..d4458d0 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -2868,6 +2868,32 @@ error:
> return ret;
> }
>
> +/*
> + * Cancel a running balance operation
> + */
> +long btrfs_ioctl_balance_cancel(struct btrfs_fs_info *fs_info)
> +{
> + int err = 0;
> +
> + if (!capable(CAP_SYS_ADMIN))
> + return -EPERM;
> +
> + spin_lock(&fs_info->balance_info_lock);
> + if (!fs_info->balance_info) {
> + err = -EINVAL;
> + goto error;
> + }
> + if (fs_info->balance_info->cancel_pending) {
> + err = -ECANCELED;
> + goto error;
> + }
> + fs_info->balance_info->cancel_pending = 1;
> +
> +error:
> + spin_unlock(&fs_info->balance_info_lock);
> + return err;
> +}
> +
> long btrfs_ioctl(struct file *file, unsigned int
> cmd, unsigned long arg)
> {
> @@ -2915,6 +2941,8 @@ long btrfs_ioctl(struct file *file, unsigned int
> return btrfs_balance(root->fs_info->dev_root);
> case BTRFS_IOC_BALANCE_PROGRESS:
> return btrfs_ioctl_balance_progress(root->fs_info, argp);
> + case BTRFS_IOC_BALANCE_CANCEL:
> + return btrfs_ioctl_balance_cancel(root->fs_info);
> case BTRFS_IOC_CLONE:
> return btrfs_ioctl_clone(file, arg, 0, 0, 0);
> case BTRFS_IOC_CLONE_RANGE:
> diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
> index 575b25f..edcbe61 100644
> --- a/fs/btrfs/ioctl.h
> +++ b/fs/btrfs/ioctl.h
> @@ -255,4 +255,5 @@ struct btrfs_ioctl_balance_progress {
> struct btrfs_ioctl_fs_info_args)
> #define BTRFS_IOC_BALANCE_PROGRESS _IOR(BTRFS_IOCTL_MAGIC, 32, \
> struct btrfs_ioctl_balance_progress)
> +#define BTRFS_IOC_BALANCE_CANCEL _IO(BTRFS_IOCTL_MAGIC, 33)
> #endif
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 4c0a386..f38b231 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -2049,6 +2049,7 @@ int btrfs_balance(struct btrfs_root *dev_root)
> bal_info->expected = -1; /* One less than actually counted,
> because chunk 0 is special */
> bal_info->completed = 0;
> + bal_info->cancel_pending = 0;
> spin_unlock(&dev_root->fs_info->balance_info_lock);
>
> /* step one make some room on all the devices */
> @@ -2109,7 +2110,7 @@ int btrfs_balance(struct btrfs_root *dev_root)
> key.offset = (u64)-1;
> key.type = BTRFS_CHUNK_ITEM_KEY;
>
> - while (1) {
> + while (!bal_info->cancel_pending) {
> ret = btrfs_search_slot(NULL, chunk_root, &key, path, 0, 0);
> if (ret < 0)
> goto error;
> @@ -2149,6 +2150,10 @@ int btrfs_balance(struct btrfs_root *dev_root)
> bal_info->completed, bal_info->expected);
> }
> ret = 0;
> + if (bal_info->cancel_pending) {
> + printk(KERN_INFO "btrfs: balance cancelled\n");
> + ret = -EINTR;
> + }
Why not detect if there's any pending signal in the while loop? so
we can just use Ctrl+C to cancel balance.
> error:
> btrfs_free_path(path);
> spin_lock(&dev_root->fs_info->balance_info_lock);
--
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