From 73a3ca20934dd02c0912bcf32463fffec6139399 Mon Sep 17 00:00:00 2001 From: Hans van Kranenburg Date: Sat, 3 Aug 2019 23:36:34 +0200 Subject: [PATCH] btrfs: clarify btrfs_ioctl_get_dev_stats padding In commit c11d2c236cc26 ("Btrfs: add ioctl to get and reset the device stats") the get_dev_stats ioctl was added. Shortly thereafter, in commit b27f7c0c150f7 ("btrfs: join DEV_STATS ioctls to one") , 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 Reviewed-by: David Sterba Signed-off-by: David Sterba --- include/uapi/linux/btrfs.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) 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 -- 2.45.2