Re: [PATCH RFC v2 6/6] inode: make i_state a u32

[Andreas Dilger <adilger@dilger.ca>]

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On Aug 21, 2024, at 9:47 AM, Christian Brauner <brauner@kernel.org> wrote:
> 
> Now that we use the wait var event mechanism make i_state a u32 and free
> up 4 bytes. This means we currently have two 4 byte holes in struct
> inode which we can pack.
> 
> Signed-off-by: Christian Brauner <brauner@kernel.org>
> ---
> include/linux/fs.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 8525f8bfd7b9..a673173b6896 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -681,7 +681,7 @@ struct inode {
> #endif
> 
> 	/* Misc */
> -	unsigned long		i_state;
> +	u32			i_state;

Is it worthwhile to add a comment that there is a hole here, instead
of leaving it for future re-discovery?

        /* 32-bit hole */

> 	struct rw_semaphore	i_rwsem;
> 
> 	unsigned long		dirtied_when; /* jiffies of first dirtying */

Normally this would be excess noise, but since struct inode is
micro-optimized (like struct page) it probably makes sense to
document this case.

Cheers, Andreas






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