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btrfs: clarify btrfs_ioctl_get_dev_stats padding

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In commit c11d2c236c ("Btrfs: add ioctl to get and reset the device
stats") the get_dev_stats ioctl was added.

Shortly thereafter, in commit b27f7c0c15 ("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 <hans.van.kranenburg@mendix.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Hans van Kranenburg 2019-08-03 23:36:34 +02:00 committed by David Sterba
parent 202f64ef42
commit 73a3ca2093
1 changed files with 6 additions and 1 deletions
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7
include/uapi/linux/btrfs.h
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@ -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