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SubjectRe: [PATCH 1/2] BDI: Provide backing device capability information
David Howells <dhowells@redhat.com> wrote:
>
>
> The attached patch does two things:
>
> (1) It gets rid of backing_dev_info::memory_backed and replaces it with a
> pair of boolean values:
>
> (*) dirty_memory_acct
>
> True if the pages associated with this backing device should be
> tracked by dirty page accounting.
>
> (*) writeback_if_dirty
>
> True if the pages associated with this backing device should have
> writepage() or writepages() invoked upon them to clean them.

Cool, thanks.

> (2) It adds a backing device capability mask that indicates what a backing
> device is capable of; currently only in regard to memory mapping
> facilities. These flags indicate whether a device can be mapped directly,
> whether it can be copied for a mapping, and whether direct mappings can
> be read, written and/or executed. This information is primarily aimed at
> improving no-MMU private mapping support.
>
> ...

> +#define BDI_CAP_MAP_COPY 0x00000001 /* Copy can be mapped (MAP_PRIVATE) */
> +#define BDI_CAP_MAP_DIRECT 0x00000002 /* Can be mapped directly (MAP_SHARED) */

Why not make these bitfields as well?

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