| Message ID | 20180609123014.8861-9-ming.lei@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
I think both callers would be just as easy to understand by using nth_page() instead of these magic helpers. E.g. for guard_bio_eod: unsigned offset = (bv.bv_offset + bv.bv_len); struct page *page = nth_page(bv.bv_page, offset); zero_user(page, offset & PAGE_MASK, truncated_bytes);
On Mon, Jun 11, 2018 at 10:19:38AM -0700, Christoph Hellwig wrote: > I think both callers would be just as easy to understand by using > nth_page() instead of these magic helpers. E.g. for guard_bio_eod: > > unsigned offset = (bv.bv_offset + bv.bv_len); > struct page *page = nth_page(bv.bv_page, offset); The above lines should have been written as: struct page *page = nth_page(bv.bv_page, offset / PAGE_SIZE) but this way may cause 'page' points to the next page of bv's last page if offset == N * PAGE_SIZE. Thanks, Ming
diff --git a/include/linux/bvec.h b/include/linux/bvec.h index 9e082d023392..aac75d87d884 100644 --- a/include/linux/bvec.h +++ b/include/linux/bvec.h @@ -219,4 +219,29 @@ static inline bool bvec_iter_chunk_advance(const struct bio_vec *bv, .bi_bvec_done = 0, \ } +/* + * Get the last singlepage segment from the multipage bvec and store it + * in @seg + */ +static inline void chunk_last_segment(const struct bio_vec *bvec, + struct bio_vec *seg) +{ + unsigned total = bvec->bv_offset + bvec->bv_len; + unsigned last_page = total / PAGE_SIZE; + + if (last_page * PAGE_SIZE == total) + last_page--; + + seg->bv_page = nth_page(bvec->bv_page, last_page); + + /* the whole segment is inside the last page */ + if (bvec->bv_offset >= last_page * PAGE_SIZE) { + seg->bv_offset = bvec->bv_offset % PAGE_SIZE; + seg->bv_len = bvec->bv_len; + } else { + seg->bv_offset = 0; + seg->bv_len = total - last_page * PAGE_SIZE; + } +} + #endif /* __LINUX_BVEC_ITER_H */
BTRFS and guard_bio_eod() need to get the last singlepage segment from one multipage chunk, so introduce this helper to make them happy. Signed-off-by: Ming Lei <ming.lei@redhat.com> --- include/linux/bvec.h | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+)