Re: [PATCH 2/5] vfs: create a generic checking function for FS_IOC_FSSETXATTR

Al Viro
2019-06-26T04:12:24Z

On Tue, Jun 25, 2019 at 07:32:18PM -0700, Darrick J. Wong wrote:
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -373,10 +373,9 @@ static int check_xflags(unsigned int flags)
> static int btrfs_ioctl_fsgetxattr(struct file *file, void __user *arg)
> {
> struct btrfs_inode *binode = BTRFS_I(file_inode(file));
> - struct fsxattr fa;
> -
> - memset(&fa, 0, sizeof(fa));
> - fa.fsx_xflags = btrfs_inode_flags_to_xflags(binode->flags);
> + struct fsxattr fa = {
> + .fsx_xflags = btrfs_inode_flags_to_xflags(binode->flags),
> + };

Umm... Sure, there's no padding, but still - you are going to copy that thing
to userland... How about

static inline void simple_fill_fsxattr(struct fsxattr *fa, unsigned xflags)
{
memset(fa, 0, sizeof(*fa));
fa->fsx_xflags = xflags;
}

and let the compiler optimize the crap out?