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-rw-r--r--fs/btrfs/ioctl.c14
1 files changed, 13 insertions, 1 deletions
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 18e328ce4b54..12ae31e1813e 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4252,7 +4252,19 @@ static long btrfs_ioctl_scrub(struct file *file, void __user *arg)
&sa->progress, sa->flags & BTRFS_SCRUB_READONLY,
0);
- if (ret == 0 && copy_to_user(arg, sa, sizeof(*sa)))
+ /*
+ * Copy scrub args to user space even if btrfs_scrub_dev() returned an
+ * error. This is important as it allows user space to know how much
+ * progress scrub has done. For example, if scrub is canceled we get
+ * -ECANCELED from btrfs_scrub_dev() and return that error back to user
+ * space. Later user space can inspect the progress from the structure
+ * btrfs_ioctl_scrub_args and resume scrub from where it left off
+ * previously (btrfs-progs does this).
+ * If we fail to copy the btrfs_ioctl_scrub_args structure to user space
+ * then return -EFAULT to signal the structure was not copied or it may
+ * be corrupt and unreliable due to a partial copy.
+ */
+ if (copy_to_user(arg, sa, sizeof(*sa)))
ret = -EFAULT;
if (!(sa->flags & BTRFS_SCRUB_READONLY))