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SubjectRe: [PATCH v2 10/18] mm: teach truncate_inode_pages_range() to handle non page aligned ranges
On Tue,  5 Feb 2013 10:12:03 +0100
Lukas Czerner <lczerner@redhat.com> wrote:

> This commit changes truncate_inode_pages_range() so it can handle non
> page aligned regions of the truncate. Currently we can hit BUG_ON when
> the end of the range is not page aligned, but we can handle unaligned
> start of the range.
>
> Being able to handle non page aligned regions of the page can help file
> system punch_hole implementations and save some work, because once we're
> holding the page we might as well deal with it right away.
>
> In previous commits we've changed ->invalidatepage() prototype to accept
> 'length' argument to be able to specify range to invalidate. No we can
> use that new ability in truncate_inode_pages_range().
>
> ...
>
> + /*
> + * 'start' and 'end' always covers the range of pages to be fully
> + * truncated. Partial pages are covered with 'partial_start' at the
> + * start of the range and 'partial_end' at the end of the range.
> + * Note that 'end' is exclusive while 'lend' is inclusive.
> + */

That helped ;) So the bytes to be truncated are

(start*PAGE_SIZE + partial_start) -> (end*PAGE_SIZE + partial_end) - 1

yes?




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