For a request to be able to refer to part of a bio, we need to be able to impose a size limit at the request level. So allow hard_nr_sectors to be less than the size of the bios (and bio_vecs) and interpret it such that anything in the last bio beyond that limit is ignored.
As some bios can be less than one sector - as happens when a SCSI sense command is being submitted - we need to set hard_nr_sectors to bi_size rounded up in blk_rq_bio_prep, and we need to abort the rq_for_each_segment loop if _iter.bio becomes NULL even if _iter.size is still non-zero Signed-off-by: Neil Brown <[EMAIL PROTECTED]> ### Diffstat output ./block/ll_rw_blk.c | 11 +++++------ ./include/linux/bio.h | 9 +++++---- ./include/linux/blkdev.h | 11 +++++++---- 3 files changed, 17 insertions(+), 14 deletions(-) diff .prev/block/ll_rw_blk.c ./block/ll_rw_blk.c --- .prev/block/ll_rw_blk.c 2007-07-31 11:21:14.000000000 +1000 +++ ./block/ll_rw_blk.c 2007-07-31 11:21:15.000000000 +1000 @@ -3364,12 +3364,10 @@ static void blk_recalc_rq_sectors(struct /* * if total number of sectors is less than the first segment - * size, something has gone terribly wrong + * size, then we have hit an early end-of-request. */ - if (rq->nr_sectors < rq->current_nr_sectors) { - printk("blk: request botched\n"); - rq->nr_sectors = rq->current_nr_sectors; - } + if (rq->nr_sectors < rq->current_nr_sectors) + rq->current_nr_sectors = rq->nr_sectors; } } @@ -3661,7 +3659,8 @@ static void blk_rq_bio_prep(struct reque /* first two bits are identical in rq->cmd_flags and bio->bi_rw */ rq->cmd_flags |= (bio->bi_rw & 3); - rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio); + rq->hard_nr_sectors = rq->nr_sectors + = DIV_ROUND_UP(bio->bi_size, 512); rq->data_len = bio->bi_size; rq->first_offset = 0; diff .prev/include/linux/bio.h ./include/linux/bio.h --- .prev/include/linux/bio.h 2007-07-31 11:21:07.000000000 +1000 +++ ./include/linux/bio.h 2007-07-31 11:21:15.000000000 +1000 @@ -222,7 +222,8 @@ struct bio_iterator { /* This macro probably need some explanation... * Its purpose is to find all the effective segments in a bio - * missing the first 'offs' bytes. We need to be sure to honour + * missing the first 'offs' bytes and only covering the next _size + * bytes. We need to be sure to honour * bi_offset which can cause us to skip part of the firs segment, * and bi_size which may cause us to stop before the end of bi_io_vec. * The 'for' loop iterates through the segments in bi_io_vec until @@ -233,9 +234,9 @@ struct bio_iterator { * follows this macro) if the size would be zero. * It also keeps 'offset' and 'size' (in the iterator) up to date. */ -#define bio_for_each_segment_offset(bv, bio, _i, offs) \ +#define bio_for_each_segment_offset(bv, bio, _i, offs, _size) \ for (_i.i = 0, _i.offset = (bio)->bi_offset + offs, \ - _i.size = (bio)->bi_size - offs; \ + _i.size = min_t(int, _size, (bio)->bi_size - offs); \ _i.i < (bio)->bi_vcnt && _i.size > 0; \ _i.i++) \ if (bv = *bio_iovec_idx((bio), _i.i), \ @@ -251,7 +252,7 @@ struct bio_iterator { bv.bv_len > 0))) #define bio_for_each_segment(bv, bio, __i) \ - bio_for_each_segment_offset(bv, bio, __i, 0) + bio_for_each_segment_offset(bv, bio, __i, 0, (bio)->bi_size) /* * get a reference to a bio, so it won't disappear. the intended use is * something like: diff .prev/include/linux/blkdev.h ./include/linux/blkdev.h --- .prev/include/linux/blkdev.h 2007-07-31 11:21:14.000000000 +1000 +++ ./include/linux/blkdev.h 2007-07-31 11:21:15.000000000 +1000 @@ -657,13 +657,16 @@ struct req_iterator { struct bio_iterator i; struct bio *bio; int offset; + int size; }; #define rq_for_each_segment(rq, _iter, bvec) \ - for (_iter.bio = (rq)->bio, _iter.offset = (rq)->first_offset; \ - _iter.bio && _iter.bio != rq->biotail->bi_next; \ - _iter.bio = _iter.bio->bi_next, _iter.offset = 0) \ + for (_iter.bio = (rq)->bio, _iter.offset = (rq)->first_offset, \ + _iter.size = (rq)->hard_nr_sectors << 9; \ + _iter.size && _iter.bio; \ + _iter.size -= (_iter.bio->bi_size - _iter.offset), \ + _iter.bio = _iter.bio->bi_next, _iter.offset = 0) \ bio_for_each_segment_offset(bvec, _iter.bio, _iter.i, \ - _iter.offset) + _iter.offset, _iter.size) #define rq_iter_last(rq, _iter) ((_iter.bio->bi_next == NULL || \ _iter.bio == rq->biotail) && \ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/