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Commit 45a3fb95 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

block: introduce mp_bvec_last_segment() 



BTRFS and guard_bio_eod() need to get the last singlepage segment
from one multipage bvec, so introduce this helper to make them happy.

Reviewed-by: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 862e5a5e

include/linux/bvec.h

+22 −0
Original line number Diff line number Diff line
@@ -131,4 +131,26 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv, 
	.bi_bvec_done	= 0,						\

}



/*

 * Get the last single-page segment from the multi-page bvec and store it

 * in @seg

 */

static inline void mp_bvec_last_segment(const struct bio_vec *bvec,

					struct bio_vec *seg)

{

	unsigned total = bvec->bv_offset + bvec->bv_len;

	unsigned last_page = (total - 1) / PAGE_SIZE;



	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 */