diff mbox series

btrfs: clarify btrfs_ioctl_get_dev_stats padding

Message ID 20190803213634.32736-1-hans@knorrie.org (mailing list archive)
State New, archived
Headers show
Series btrfs: clarify btrfs_ioctl_get_dev_stats padding | expand

Commit Message

Hans van Kranenburg Aug. 3, 2019, 9:36 p.m. UTC 
From: Hans van Kranenburg <hans.van.kranenburg@mendix.com>

In commit c11d2c236cc26 the get_dev_stats ioctl was added.

Shortly thereafter, in commit b27f7c0c150f7, the flags field was added.
However, the calculation for unused padding space was not updated, which
also invalidated the comment.

Clarify what happened to reduce confusion and wasted time for anyone
implementing this.

Signed-off-by: Hans van Kranenburg <hans.van.kranenburg@mendix.com>
---
 include/uapi/linux/btrfs.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Comments

David Sterba Aug. 5, 2019, 6:07 p.m. UTC | #1 
On Sat, Aug 03, 2019 at 11:36:34PM +0200, Hans van Kranenburg wrote:
> From: Hans van Kranenburg <hans.van.kranenburg@mendix.com>
> 
> In commit c11d2c236cc26 the get_dev_stats ioctl was added.
> 
> Shortly thereafter, in commit b27f7c0c150f7, the flags field was added.
> However, the calculation for unused padding space was not updated, which
> also invalidated the comment.
> 
> Clarify what happened to reduce confusion and wasted time for anyone
> implementing this.
> 
> Signed-off-by: Hans van Kranenburg <hans.van.kranenburg@mendix.com>

Reviewed-by: David Sterba <dsterba@suse.com>
diff mbox series

Patch

diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index 7885d79f7515..3ee0678c0a83 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -665,7 +665,12 @@  struct btrfs_ioctl_get_dev_stats {
 	/* out values: */
 	__u64 values[BTRFS_DEV_STAT_VALUES_MAX];
 
-	__u64 unused[128 - 2 - BTRFS_DEV_STAT_VALUES_MAX]; /* pad to 1k */
+	/*
+	 * This pads the struct to 1032 bytes. It was originally meant to pad to
+	 * 1024 bytes, but when adding the flags field, the padding calculation
+	 * was not adjusted.
+	 */
+	__u64 unused[128 - 2 - BTRFS_DEV_STAT_VALUES_MAX];
 };
 
 #define BTRFS_QUOTA_CTL_ENABLE	1