[PATCH v3 23/59] netfs: Prep to use folio->private for write grouping and streaming write
Matthew Wilcox
willy at infradead.org
Thu Dec 7 13:34:55 PST 2023
On Thu, Dec 07, 2023 at 09:21:30PM +0000, David Howells wrote:
> +#define NETFS_FOLIO_INFO 0x1UL /* OR'd with folio->private. */
> +
> +static inline struct netfs_folio *netfs_folio_info(struct folio *folio)
> +{
> + void *priv = folio_get_private(folio);
> +
> + if ((unsigned long)priv & NETFS_FOLIO_INFO)
> + return (struct netfs_folio *)((unsigned long)priv & ~NETFS_FOLIO_INFO);
Often one gets better code by using '-' instead of '& ~', and that's
because 'subtract one, then load four bytes from offset 12' can be
optimised into 'load four bytes from offset 11' in a way that 'clear
the bottom bit, then load four bytes from offset 12' can't be.
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